TWI677180B - Controlled energy storage balance technology - Google Patents

Abstract

An energy storage system includes an energy storage device and a system controller. When the DC power is discharged to the DC / AC inverter, the energy storage device also receives DC power from the DC power source for charging. The system controller controls the amount of DC power released from the energy storage device to the DC / AC inverter, so that the DC power stored in the energy storage device and the power (for the DC / AC inverter) are almost balanced with each other. Because this design allows the instantaneous charge and discharge of the energy storage to be almost balanced, the required energy storage capacity can be made very small compared to a high charge and high discharge that is not instantaneously balanced. Taking a solar power station as an example, when the energy storage device receives all or most of the charge generated by the power station, this controller design becomes very advantageous in the state of high charge and discharge.

Description

   Techniques for controlling stored energy balance   

The invention relates to a technology for controlling the balance of stored energy.

Photovoltaic (PV) power stations convert solar energy into electricity. The generated electricity is then provided to the grid. Failure to provide a constant light intensity is a characteristic of solar energy (i.e., received solar light). Therefore, the photovoltaic power generators in such photovoltaic power stations all add a power generation optimization component (also called "optimizer"). One type of optimizer is named "Maximum Power Point Tracker (MPPT)" (or "MPPT component"). MPPT is used to track the instantaneous maximum power generation (MPPP) voltage value to control the operation of photovoltaic power plants. This approach is called "blindly following MPPT" in this article. MPPT is usually software or firmware; it is used to continuously find and track the voltage value of the maximum power generated by the solar energy source due to the time-varying intensity.

The scope of the claims of this patent is not just to resolve the shortcomings of any of the above practical cases or the environment in which they are used. It should be said that this background narrative only provides one of the areas where the implementation case is applied.

The embodiments described herein relate directly to an energy storage system that includes an energy storage and a system controller. When the DC energy is discharged to the DC / AC inverter, the energy storage device receives DC energy from the DC power source for charging. The system controller controls the DC energy discharged from the energy storage device to the DC / AC inverter, so that the DC electric energy stored in the energy storage device and the electric energy (for the DC / AC inverter) are almost balanced with each other. Because this design allows the instantaneous charge and discharge of the energy storage to be almost balanced, the required energy storage capacity can be made very small compared to a high charge and high discharge that is not instantaneously balanced. Taking a solar power station as an example, when the energy storage device receives all or most of the charge generated by the power station, this controller design becomes very advantageous when the charge and discharge are high. This kind of controller can make the energy storage device practically feasible in the application technology of the power station even under the very large transmission current in the solar power station.

The system controller includes a detection module, a determination module, and a message transmission module. The detection module is configured to measure the capacity of electric energy stored in the energy storage device. The determination module is configured to evaluate whether the measured electric energy capacity of the energy storage is to be adjusted for the stored electric power. The message transmission module is configured to compile the instruction for performing the adjustment into a message code when the determination module determines that the stored power is to be adjusted and transmit the message code to the DC / AC inverter.

This summary of conclusions is provided to introduce some concepts in a simplified manner, and these concepts will be further described in the following detailed embodiments. The purpose of this summary review is not to define the key or basic characteristics of the scope of this patent claim, nor to help determine the scope of the claimed patent claim.

1100B‧‧‧Solar Panel String

1100C‧‧‧photovoltaic solar string, photovoltaic string

1201B‧‧‧DC / AC Inverter

1201C‧‧‧DC / AC Inverter

1202B‧‧‧DC / AC Inverter

1202C‧‧‧DC / AC Inverter

1300A‧‧‧ Energy Storage

1300B‧‧‧ Energy Storage

1300C‧‧‧Energy storage

1310B‧‧‧MEUPT controller

1310C‧‧‧MEUPT controller

1400C‧‧‧Diode C

1500B‧‧‧Transformer

1500C‧‧‧Transformer

1600B‧‧‧cable

2000A‧‧‧PV Power Station

2100A‧‧‧Power generation unit, power production unit, power generation unit

2100B‧‧‧ Power generation unit, power production unit, power generation unit

2110A‧‧‧ Generator

2111A‧‧‧Solar Panel Strings, Photovoltaic Strings

2111B‧‧‧ solar panel string, photovoltaic string

2112A‧‧‧Photovoltaic string

2112B‧‧‧ solar panel string, photovoltaic string

2130A‧‧‧ Inverter

2130B‧‧‧ Inverter

2130S‧‧‧ Inverter

2140B‧‧‧ Energy Storage

2200A‧‧‧Power generation unit, power production unit

2200B‧‧‧Power generation unit, power production unit

2220A‧‧‧Generator

2221A‧‧‧Solar Panel String

2222A‧‧‧Solar Panel String

2230A‧‧‧Inverter

2230B‧‧‧ Inverter

2311B‧‧‧Intercepting Diodes, Intercepting Diode Sets, Intercepting Components

2312B‧‧‧Intercepting Diode, Intercepting Diode Set

2313B‧‧‧Intercepting Diode, Intercepting Diode Set

2320B‧‧‧MEUPT controller

2351A‧‧‧Three-phase AC Wattmeter

2351B‧‧‧Power Meter, Electricity Meter

2352A‧‧‧Three-phase AC Wattmeter

2352B‧‧‧ Electricity Meter

2361A‧‧‧ Electricity Meter

2361B‧‧‧ Electricity Meter

2362A‧‧‧ Electricity Meter

2362B‧‧‧ Electricity Meter

2410B‧‧‧Measured Energy Storage

2420B‧‧‧MEUPT Controller

2500A‧‧‧Transformer

2600A‧‧‧Grid

3000‧‧‧PV Power Station

3100‧‧‧AC Power Production Unit

3110‧‧‧DC Power Module

3110‧‧‧Solar Panel Strings

3110‧‧‧Generation Module

3110‧‧‧ Generator

3130‧‧‧ Inverter

3130S‧‧‧Inverter

3311‧‧‧ Intercepting Components

3312‧‧‧Intercepting components

3313‧‧‧Intercepting components

3410‧‧‧ Energy Storage

3500‧‧‧Transformer

3600‧‧‧Grid

4110‧‧‧Solar Panel String

4130‧‧‧PS three-phase DC / AC inverter

4130S‧‧‧ER three-phase DC / AC inverter

4213‧‧‧Message Transmission Module

4311‧‧‧Intercepting device

4312‧‧‧ Intercepting components, intercepting devices

4313‧‧‧Intercepting components

4410‧‧‧ Energy Storage

4500‧‧‧Transformer

4502‧‧‧Three-phase DC / AC inverter

4600‧‧‧Grid

5000‧‧‧PV Power Station

5100‧‧‧AC power production unit

5110‧‧‧DC generator, generator

5130‧‧‧ Inverter

5130S‧‧‧Inverter

5311‧‧‧ Intercepting Components

5312‧‧‧ Intercepting components

5313‧‧‧Intercepting components

5410‧‧‧ Energy Storage

5500‧‧‧Transformer

5600‧‧‧Grid

6110‧‧‧Solar Panel Strings

6130‧‧‧ Inverter

6130S‧‧‧ Inverter

6311‧‧‧ Intercepting components

6313‧‧‧ Intercepting components

6410‧‧‧ Energy Storage

7000‧‧‧PV solar power station, PV power station, DC generator

7100‧‧‧DC Generator

7100‧‧‧PV Solar Panel String

7100‧‧‧Solar Panel Strings

7201‧‧‧ Intercepting components

7201‧‧‧ Intercepting Device

7202‧‧‧ Intercepting components

7203‧‧‧ Intercepting components

7301‧‧‧PS Inverter

7301‧‧‧Three-phase DC / AC inverter

7301‧‧‧Three-phase DC / AC inverter

7301‧‧‧ Inverter

7302‧‧‧ER Inverter

7302‧‧‧Three-phase DC / AC inverter

7302‧‧‧ Inverter

7400‧‧‧energy storage

7410‧‧‧ Energy Storage

7500‧‧‧Transformer

7600‧‧‧Grid

8000‧‧‧MEUPT controller

8000‧‧‧ Controller

8100‧‧‧ Detection Module

8200‧‧‧Judgment Module

8300‧‧‧Message Transmission Module

8400‧‧‧ surplus power storage

8400‧‧‧energy storage

8500‧‧‧ Inverter

9000‧‧‧PV Power Station

9100‧‧‧PV Solar Panel Strings, Solar Panel Strings

9200‧‧‧MEUPT controller

9210‧‧‧MEUPT controller

9211‧‧‧ Detection Module

9212‧‧‧Judgment Module

9213‧‧‧Message Transmission Module

9320‧‧‧ Intercepting components

9330‧‧‧ Intercepting components

9400‧‧‧Residual energy storage, remaining storage

9502‧‧‧Three-phase DC / AC inverter

9600‧‧‧Transformer

9700‧‧‧Grid

SW1‧‧‧Switch

SW2‧‧‧Switch

SW3‧‧‧Switch

In order to make the above and other objects, features, advantages, and embodiments of the present disclosure more comprehensible, the description of the drawings is as follows: FIGS. 1A to 1C illustrate the use of the interception coupling component and the energy storage device in a solar power station. Different architectures; Figure 2A shows the power station architecture diagram set in the experiment. There are two traditionally set AC power production units, and each power production unit has a power meter and a kilowatt-hour meter (electricity meter) that measure the output individually. FIG. 2B shows the structure diagram of the power station after the modification of FIG. 2A, which includes interception coupling devices and energy storage devices, which are used to verify that enhanced power can be output to the power grid; FIG. 3 shows the structure diagram of the power station with two power transmission channels, One transmission channel calls an energy storage device, and the other transmission channel does not call an energy storage device; FIG. 4 represents a generalized power station architecture diagram representing the embodiment of FIG. 3; and FIG. 5 illustrates a power station architecture diagram for transmitting power by using the energy storage apparatus; Figure 6 represents the generalized power plant architecture diagram representing the embodiment of Figure 5; Figure 7 represents the architecture diagram of a solar power plant; and Figure 8 represents the maximum energy use point tracking (MEUPT) described in accordance with the principles of this document FIG system's architecture; FIG. 9 and FIG. 8 MEUPT expresses the solar power system controller disposed in the architecture of FIG.

The following is a detailed description with examples and the accompanying drawings, but the examples provided are not intended to limit the scope covered by this disclosure, and the description of the structure operation is not used to limit the order of its implementation. Any recombination of components The structure and the devices with the same effect are all the scope covered by this disclosure. In addition, the drawings are for illustrative purposes only, and are not drawn to the original dimensions. In order to facilitate understanding, the same elements or similar elements in the following description will be described with the same symbols.

US patent bulletins US2016 / 0036232 and US2017 / 0149250A1 (this article refers to the two patent publications and is described here after integration) discloses that the use of photovoltaic power systems that follow the MPPT blindly can only provide part of the power generation energy to the power grid. These patent publications also teach that, in order to effectively extract power for use, the power extraction device must be able to match the front and rear equipment in order to achieve efficient and effective extraction of the produced electrical energy. In addition, these patent publications also disclose that some related components should also be matched to adjust and / or deliver the captured power to effectively use the captured power.

These patent bulletins also emphasize the fact that, in addition to the efficiency at the power generation side, the efficiency of energy use will definitely depend on the power demand at the demand side. It is even further revealed that in any energy system, even if energy and charge conservation are met, the typical power consumption is not necessarily equal to the power production.

Referring to the proposal cited in the patent announcement, the power system must use "maximum power usage point (or MEUPT component)" tracking technology instead of MPPT (maximum power generation voltage tracking) technology. Such an optimizer is referred to herein as a "MEUPT optimizer". According to the cited patent announcement, the MEUPT optimizer is designed to capture the "remaining power" mentioned in the patent announcement. Residual energy is defined as "electricity that has not been captured and / or delivered to the grid for utilization". The definition of "residual energy" used in the patent publications cited herein is the same as the above definition.

The MEUPT optimizer can be designed to temporarily store the remaining electrical energy captured in the energy store; then adjust and deliver this electrical energy to the grid for use. Therefore, when the MEUPT optimizer is incorporated into the power plant, it can increase the electricity sales revenue of photovoltaic power plants.

Section 1: MEUPT Optimizer Features

According to the principles described in US2016 / 0036232 and US2017 / 0149250A1 ("Reference Patent Bulletin"), the "MEUPT optimizer" embodiment disclosed herein includes a residual power extractor, an energy storage device, and a MEUPT controller. The MEUPT controller works in conjunction with a power grabber and a DC / AC inverter. Although the terms "power" and "energy" (although the physics they represent are completely different) are often used interchangeably in the field of electric power. Therefore, unless otherwise stated, both have the same meaning herein.

The power extractor extracts an initial pulsating power from a DC power source produced by the power station. The initial power captured must comply with the AC requirements of the grid. In other words, the captured initial pulsating power has a varying sinusoidal voltage and has a peak voltage that follows the grid voltage range. In addition, the power (proportional to the square of the voltage) takes a waveform (sin ² (ωt) or cos ² (ωt)) that is synchronized with the grid (with the same phase and frequency).

On the other hand, the residual power extractor captures the residual pulsating power, and the residual pulsating power is the DC power produced minus the initial pulsating power. In other words, this residual pulsating power is the power remaining after the initial pulsating power is supplied to the grid. Compared to the initial pulsating power supplied to the grid, the remaining pulsating power has a phase difference of 90 degrees. Due to this 90-degree phase difference, the remaining pulsating power cannot be immediately converted into AC power and supplied to the same pair of cables. Therefore, the energy storage must be used to temporarily store the remaining (pulsating) power. After storage, the energy stored in the energy storage is provided to DC / AC inverter; enables the stored residual energy to be converted into AC power synchronized with the same pair of cables (with the same phase and frequency).

The MEUPT controller is designed to measure the stored energy level in the energy storage; and estimate the amount of stored energy that can be captured in the energy storage; and then pass this information to the connected DC / AC inverter, so that the appropriate The stored energy is retrieved by the DC / AC inverter. The captured stored energy is then converted into AC power in the form of appropriate pulsating power and provided to the pair of cables. Therefore, when incorporated into the MEUPT optimizer, a photovoltaic power plant can provide almost all of the electrical energy produced to the grid. On the contrary, according to the content of the cited patent announcement; in the absence of the MEUPT optimizer, the power / electricity generated by the PV power plant can only provide less than half of the electrical energy produced by the grid.

Section 2: Traditional Photovoltaic Power Station Improved with MEUPT

Solar power plants are typically in the multi-megawatt (MW) power class. Traditionally, when the rated power declared by a solar power plant is x MW (where x is a certain positive value), this means that the sum of the DC power generation ratings of all solar panel strings is x MW. This traditional solar power station is also equipped with a three-phase DC / AC inverter, and all inverter manufacturers claim that the ability to convert DC power to AC power will not be greater than x MW. This principle is based on conclusions obtained from traditional power stations operating in accordance with MPPT.

In other words, a traditional photovoltaic power plant rated x MW is made up of x MW photovoltaic solar panels connected in series to convert solar energy into DC power. This generated DC power is captured by a three-phase DC / AC inverter and converted into appropriate AC power that meets all AC power requirements of the power grid to be provided to the power grid. This AC power provided to the grid is also referred to herein as "initial pulsating power." Here again, all manufacturers claim that the DC power conversion capacity of the DC / AC inverter will not be greater than x MW, which is also the total DC power generation of the solar panels announced by the solar panel industry.

According to the inferences in the two cited patent publications US2016 / 0036232 and US2017 / 0149250A1, the remaining pulsating power in the above-mentioned power station is the exact existence, which is the total DC power generated by the solar panel string minus the initial pulsating power ( (Remained by the power grabber). In other words, the residual power has a phase difference of about 90 degrees from the initial pulsating power.

Because the remaining pulsating power is about 90 ° out of phase with the grid power, this remaining pulsating power cannot be directly adjusted and converted into AC power, which is provided to the same pair of cables. According to the principle disclosed in the cited patent publication, the energy temporarily stored by the energy storage device is electrical energy including residual pulsating power with a phase difference of 90 degrees (when the residual pulsating power is stored, it represents the residual electrical energy). After the remaining electric energy is stored in the energy storage device, the remaining electric energy can serve as the DC electric energy to be supplied to the DC / AC inverter. This residual power is then converted into AC power that complies with all grid specifications, including synchronization with the grid, so that the generated AC power can be provided to the same pair of cables.

Section 3: Preventing Energy Leak from Energy Storage

Before explaining the energy storage design of the MEUPT optimizer in detail, this article first needs to explain an important issue. Specifically, the solar panel string may have a very high resistance at dusk, but when the sunlight is strong at noon, the solar panel string can obviously conduct current in the direction of coming and going. Therefore, the electric energy stored in the energy storage device may leak during the day to heat the solar panel. If you add a decoupling diode to each group of solar panel strings, you can make sure that electricity is output from each solar panel string to the energy storage device for charging, but the energy in the energy storage device will not return to the solar panel. . Figures 1A, 1B, and 1C depict different types of energy storage systems that are completed with a configuration of a coupled coupling structure.

Section 4: Design Considerations for Energy Storage

Figure 1A depicts the architecture diagram of the energy storage device 1300A, which is designed to temporarily store the remaining (DC) power generated by the solar panel string 1100A, that is, convert the DC power produced by 1100A to AC power minus DC / After the actual power that the AC inverter 1200A fetches, the resulting surplus power is stored in this energy storage. The AC power converted by the inverter is then supplied to the power grid 1600A through the transformer 1500A. The remaining power passes through the intercepting diode group 1400A, and the energy storage device 1300A receives the remaining pulsating power. In one implementation case, the energy storage 1300A is designed to temporarily store the remaining electrical energy of a 1 MW photovoltaic power plant for about 2 minutes.

As an example, suppose that the initial energy can be maintained at a constant intensity (the power production of the PV string 1100A is maintained at a fixed intensity, so a 1MW generator can be allowed to generate electricity constantly) for 2 minutes. For the following analysis, both the initial and remaining pulsating power have the same periodic waveform, but the initial and remaining power have a 90-degree phase difference. First, let's look at how to design an energy storage device using a brute force method. Remember that the purpose of the energy store is to temporarily store the remaining energy so that the DC / AC inverter can later convert this stored remaining energy.

As discussed in the referenced patent publication, for a typical conventional PV power plant, the estimated ratio of residual power to DC power generated is greater than 0.5. For the convenience of analysis, let us assume that a photovoltaic power station has a 1 megawatt photovoltaic solar panel string; and convert DC power to AC power to provide a line voltage of 50 Hz and 380 volts AC in the power grid. In this case, the duration of one power cycle is approximately equal to 0.01 seconds, and the total current of the three phases is as high as 1,000,000 / (380 / 1.732), where 1.732 is a square root value of 3. This ratio is the relationship between the peak voltage and the line voltage (phase-to-line voltage or "phase voltage" in three-phase alternating current). Storing the charge related to the remaining power in the power cycle of the power station will require an equivalent charging capacity of about 8V Faradays (0.5 * 0.01 * 1,000,000 / (380 / 1.732)), where "V" is the voltage difference allowed by the AC grid ; That is, the voltage difference between the designed energy store before and after charging.

In order to maximize the energy used by the photovoltaic power plant, in some embodiments, the operating voltage of the MEUPT optimizer should be about 75% of the voltage at which the PV power plant generates power. In other words, in those embodiments of the MEUPT optimizer, a corresponding voltage range of 75% of the maximum power will be observed. The measured "current-voltage" corresponding value indicates that this voltage range is usually around 80 volts. When this voltage range is selected as the charge / discharge voltage range of the energy storage (that is, V = 80 volts), at each power cycle per million watts (where the power cycle lasts approximately 0.01 seconds), the capacity of the energy storage About 0.1 Farads.

If the design consideration is to store the maximum remaining electrical energy accumulated over two (2) minutes, the equivalent power capacity required is equal to 1200 Farads (100 * 120 * 0.1) for a 1MW photovoltaic power plant. This article calls this required equivalent capacitance the “maximum total capacitance” and the associated energy storage is referred to as the “maximum total energy storage capacity” or “maximum total residual energy”.

If only a film capacitor is used to meet the required capacitance, the film capacitor capacity required to meet the capacitance will be too large to meet actual needs, and the cost will be very high. Therefore, an energy storage device consisting only of a thin film capacitor is not in line with actual needs.

If the brute force method of deformation design is used, a Faraday device (such as a battery) is integrated into the energy storage design to reduce the volume and capacity. A detailed analysis from the inventor shows that for an energy storage device having a thin film capacitor and a Faraday device, the required capacitance range is technically practical. However, the cost of using such an energy storage device is still too high, which is not conducive to actual profit. Unless the price of the battery remains the same as the existing performance, it can be reduced to at least 1/3 of the original price.

The use of electrolytic capacitors can significantly reduce the required investment costs. However, due to the relatively short life of such capacitors, long-term operating costs can increase significantly. Therefore, it is not realistic to use electrolytic capacitors at present. Therefore, the brute force method cannot achieve an economically beneficial design and meet the maximum capacity requirements required for energy storage.

The principles described here use the following facts observed by the inventors to solve this problem:

(1) Most existing DC / AC inverters can easily rise or fall by 3% of power in one second; while existing 500kW DC / AC inverters can easily rise and fall by more than one second during operation. 10kW.

(2) Take a rough look at a typical one-megawatt photovoltaic power plant; start generating electricity from zero power every morning, and rarely generate more than 10 kilowatts per second in daily normal operation.

(3) Megawatt-scale photovoltaic power stations (rated power greater than 1 million watts) will occasionally generate a sudden increase in power of more than 10 kilowatts per second within a short period of time during the power pulse. However, the energy of this short burst (or even a larger burst of 100 kilowatts per second) is insignificant compared to the total daily energy produced by a MW-class power station.

Based on the above three facts, the inventors determined that: (1) the amount of electricity generated by each solar panel string every morning starts from zero; and (2) the photovoltaic generator cannot immediately produce full power. Therefore, the remaining pulsating power does not immediately rise to the maximum power generation. In other words, the rate of rise of the residual pulsating power is usually much higher than the rate of rise of the DC / AC inverter power conversion. Moreover, any transient pulse-increased energy will not be a major problem for energy harvesting of photovoltaic power plants rated 1 million watts or higher.

Therefore, this patent proposes to design an energy accumulator that can be used to replace the maximum total remaining electrical energy. The principle described here is to propose the design of an energy accumulator that stores a net energy, which is more than 2 minutes. The difference between the remaining electrical energy in the energy store and the energy extracted by the DC / AC inverter from the energy store. This energy difference is referred to herein as the "maximum residual energy difference." The magnitude of this maximum residual power difference is much smaller than the maximum total residual power. Therefore, this smaller energy storage device is easier to design; it is technically feasible and meets cost requirements.

Figure 1B depicts a structure that symbolically illustrates that the remaining power generated is stored in the energy storage device 1300B. The remaining power is obtained by subtracting the DC / AC inverter 1201B from the power generated by a group of solar panel strings 1100B. The rest of the electricity is the electricity stored in the energy store 1300B. At the same time, another DC / AC inverter 1202B accepts the instructions of the MEUPT controller 1310B to receive the DC power (including the remaining power) from the energy storage 1300B, so that the power received by the 1202B and the surplus stored in the energy storage The power is almost equal. Both the DC / AC inverters 1201B and 1202B individually convert the received DC power into AC power at the same time, and provide the AC power to the same pair of cables 1600B through the same transformer 1500B. In this way, compared to the design of the energy storage device 1300A shown in FIG. 1A, the net energy storage load of the 1300B can be reduced to a very small capacity.

FIG. 1C is modified from the configuration depicted in FIG. 1B, but still has almost the same performance as the configuration in FIG. 1B. As shown in FIG. 1C, the DC power generated by the photovoltaic solar string 1100C is stored to the energy storage device 1300C through a set of diodes 1400C. The two DC / AC inverters 1201C and 1202C are instructed by the MEUPT controller 1310C. (Total) receives the total DC output power from the energy storage 1300C. This output power is almost equal to the input generated by the photovoltaic solar string to the energy storage. DC power of the converter. Therefore, from the input and output power of the energy storage 1300C, as long as the net input power is very small, the stable capacity of the energy storage can be maintained. Both 1201C and 1202C convert the received DC power into AC power at the same time, and then pass through the same transformer 1500C to supply the same pair of cables 1600B.

In short, as shown in Figure 1B (when the interception is correct), after the generated DC power is extracted by the power extractor (which can be built in as a module of the DC / AC inverter 1201B), it can be used in the form of pulsating power The remaining power is captured and stored in the energy storage, and the remaining pulsating power is saved. The other DC / AC inverter 1201B is designed to extract approximately equal electrical energy from the energy storage 1300B to reduce the net residual electrical energy stored in the energy storage. Therefore, a relatively small-capacity energy storage device is suitable for the needs of this energy storage design.

Similarly, as shown in FIG. 1C (when the interception coupling design is correct), the energy storage device 1300C can receive all the generated DC power from the photovoltaic string 1100C. Then, the pulsating power is extracted by the DC / AC inverters 1201C and 1202C. At the same time, the remaining pulsating power in the form of a 90 degree phase difference of the remaining electrical energy (residual power) is also passively stored in the energy storage 1300C. As shown in the figure, the remaining electrical energy is also naturally extracted and stored in the energy storage device 1300C.

Using the energy storage device in any of the design architectures depicted in FIG. 1B (or FIG. 1C) can provide the energy storage device as a MEUPT optimizer; it can temporarily store a small residual energy with a 90-degree phase difference. In this way, the difficult task of the original maximum total capacity storage can be transferred to a properly designed MEUPT controller.

Section 5: Necessary Functions of MEUPT Controller

The MEUPT controller should be designed to be able to guide the relevant DC / AC inverter to safely extract the appropriate energy from the energy storage device, and the extracted energy is approximately equal to the amount of remaining electrical energy charged into the energy storage device. In this way, the net energy stored in the energy storage can be minimized; and the energy storage can be maintained at a balanced and appropriate power storage capacity to stabilize the operation of the system. When operating in this way, it only needs to be designed to store the charged surplus power in excess of the power drawn by the DC / AC inverter into the energy storage device within a short time interval; or draw insufficient power from the energy storage device to the DC / AC inverter. With this balanced design, small-capacity energy storage can be used.

Using a controllable controller as described above, the net energy can be designed within a small controllable range. As long as the operating time interval is designed to be long enough, and the rise or fall of the operating power of the DC / AC inverter can be quickly and correctly matched to the change of the remaining electrical energy; while the energy storage capacity is significantly reduced, the system can also be ensured Stable operation. In this way, the capacity of the energy storage can be estimated to be reduced to 0.001 times the maximum total remaining energy. The energy storage capacity requirement per million watts of photovoltaic power stations is less than 2 Faraday. In this way, even if film capacitors are used as energy storage, suitable film capacitor specifications can be found and used. This article will use sections 12 to 14 to describe how to use an appropriate MEUPT controller example.

Section 6: Capacitor / Battery Energy Storage Combination

Another consideration: when using a good film capacitor for 10 to 15 years, it can still maintain more than 80% of its original capacitance, while a good battery can last up to 5 years and can retain about 70% of its initial capacity. Therefore, the inventors suggest that the energy storage design should be careful with the net energy balance to optimize the economic benefits of the system. In addition, the capacity in the energy storage device needs to be large enough to maintain stable system operation at all times. According to the design simulation, according to the current price of film capacitors and batteries, a typical 20-year optimized energy storage design for a 1 MW photovoltaic power station should use 0.1 to 1 Faraday film capacitors and about 50 amp-hours of cheap standard automotive batteries The strings allow the energy storage device to operate at the appropriate operating voltage.

Section VII: Preventing Electricity in PV Strings from Mutual Extinction

As mentioned above, the interception coupling technology applied in FIG. 1B and FIG. 1C allows the solar panel string to charge the energy storage device; and prevents power from flowing back from the energy storage device to the PV solar panel string. This technique not only prevents leakage of energy from the energy storage device through the strings of PV solar panels, but also prevents another bad phenomenon discovered by the inventors when properly applied with a decoupled diode. This phenomenon is called "mutual power annihilation phenomenon between PV strings", or "mutual power annihilation phenomenon" or "electricity annihilation phenomenon" in this article.

This kind of power annihilation often occurs when many photovoltaic groups collect electricity when connected in series and parallel. This phenomenon is particularly noticeable when different photovoltaic strings connected in parallel have comparable I-V characteristics to each other, or have different photoelectric conversion efficiency, and / or have different maximum power production voltages.

For example, when some solar panels in these parallel groups are shaded, the PV strings in the shadow will have lower photoelectric conversion efficiency than the PV strings in the non-shaded area. In other words, due to the shadows cast in different regions, these solar panel strings will have considerable I-V characteristics differences even at the same time of day. When these solar panel strings are connected in parallel, the solar panel strings with high conversion efficiency will discharge part of the electricity generated to the solar panel strings with lower efficiency, resulting in the production of electricity in some PV solar panel strings being offset. . The inventors have confirmed this phenomenon through experiments. These experiments also show that this kind of undesirable phenomenon can be prevented when the photovoltaic solar panel string is connected to the correct interception coupling.

In addition, the inventor's experiments also confirmed that when photovoltaic strings connected in parallel, individual strings have very different maximum power production voltages, electric annihilation also occurs. For example, suppose there are two strings of solar panels connected in parallel; one of them consists of 15 solar panels connected in series and the other consists of 19 solar panels connected in series. Experiments have shown that the power generated by 19 solar panels connected in series will surely release electricity through 15 solar panels connected in series, leading to the phenomenon of power annihilation. Experimental results show that the actual power received by the two strings connected in parallel can be reduced to half the power generated by only 19 solar panels connected in series. However, when properly decoupled, the power received from the two parallel photovoltaic strings can be restored to about 1.53 times the power produced by 19 strings connected in series. The above experiments show that: (a) there is a mutual power annihilation phenomenon; and (b) the correct interception coupling technology can prevent this kind of power annihilation phenomenon.

In another experiment, a photovoltaic power plant was set up as two power production units; each unit consisted of 85 solar panels of the same manufacturer and the same model in series and parallel. Each of the two power production units is configured with five (5) parallel photovoltaic strings to collect the generated DC energy. Each photovoltaic string is configured with two sets of 15 series-connected solar panels, two sets of 19 series-connected solar panels, and a group of 17 series-connected solar panels. When the sky is high at noon and the sky is clear and without clouds, the experiment measured the maximum power production voltage of these 10 groups of solar panel strings separately. The minimum value of the maximum power production voltage is 420 volts, and the maximum value is 610 volts. This phenomenon tells us that even in the same clear sky, these parallel solar panel strings will still have very different maximum power production voltages.

Each group of power production units converts the collected DC power into AC power via different DC / AC inverters. In order to measure the electrical energy and power produced in each group of production units, an AC output terminal of each DC / AC inverter in each production unit is connected with a wattmeter and a wattmeter. These units are then connected to a transformer to provide grid AC power. During the 36-day operating time, the 72 readings of the two wattmeters were read twice a day, confirming that they were almost the same, and at the end of 36 days, the readings from the two electricity meters were also consistent. This experiment can It is proved that these two power production units (including two sets of measuring instruments) can be confirmed to be sufficiently consistent and identical.

Then, an electric power production unit was modified to be configured into 4 groups in parallel, each group having 21 strings of solar panels connected in series (one of which is not used). While another power production unit maintains the above-mentioned five parallel solar panel strings, it is not modified. Then measure the electricity generated at noon in the clear sky, and the modified power production unit is generally more than 4.1 times the power generation of the unmodified power production unit. We then derived a cumulative energy measurement of sixty (60) days from the readings of the two kilowatt-hour meters. The power provided by the modified power production unit is 3.38 times that of the unmodified power production unit. The above experiment clearly proves that mutual power annihilation does exist in parallel photovoltaic strings, especially for individual strings in parallel strings with very different I-V characteristics, or maximum power production voltages that differ greatly.

In a word, according to the principle of the correct interception technology described in this article, the energy storage device can be prevented from leaking electric energy to the string of solar panels; the phenomenon of electric power annihilation between PV strings can also be prevented.

Section VIII: Experiments to prove the existence of residual energy

Before explaining the design of the MEUPT optimizer, the description of the articles in this chapter can refer to the predictions in the patent publications US2016 / 0036232 and US2017 / 0149250A1, and experiments to prove the existence of the remaining power in these PV power plants. To reiterate, in the cited patents, the definition of residual electrical energy refers to electrical energy that has been produced, but converted to heat before it is extracted and / or used. Specifically, in a photovoltaic power plant, "residual power" is included in DC power production, and all power that is not captured by a three-phase DC / AC inverter and converted to AC power. The MEUPT optimizer is designed to capture / use these uncaptured remaining electrical energy (residual energy). The following is a description of the experimental design and step-by-step method.

Figure 2A depicts a setup of a PV power plant 2000A including two AC power production units 2100A and 2200A. The 2100A and 2200A both use the MPPT power production architecture blindly; and provide three-phase AC power to the grid 2600A. The AC power production unit 2100A consists of a DC generator 2110A and a three-phase DC / AC (15KW) inverter 2130A. The AC power production unit 2200A is composed of a DC generator 2220A and a three-phase DC / AC (15kW) inverter 2230A. The generator 2110A uses two parallel PV strings 2111A and 2112A to generate DC power. The generator 2220A uses two other parallel solar panel strings 2221A and 2222A to generate DC power. Each of the 4 parallel PV strings is composed of 25 solar panels connected in series; each solar panel can generate 250W of electricity at noon and under clear skies.

The DC generator 2110A supplies DC power to the three-phase DC / AC inverter 2130A; and the DC generator 2220A supplies DC power to the three-phase DC / AC inverter 2230A. These two inverters 2130A and 2230A convert the supplied DC power into three-phase AC power. In this experiment, the AC output power of the power production units 2100A and 2200A was measured by two three-phase AC wattmeters 2351A and 2352A, respectively. These two power generation units 2100A and 2200A also measure the AC power generation (仟 W * h) from (仟 Wh meter) electricity meters 2361A and 2362A, respectively. These three-phase AC power is provided to the grid 2600A through the transformer 2500A. Under the operating conditions of the photovoltaic power plant; the production electric energy of two AC power production units 2100A and 2200A was measured within 7 days.

The readings of the two kilowatt-hour meters show the same readings at the same time every day; this proves that all the components of the two power production units 2100A and 2200A (including the two sets of instruments used for measurement) are basically the same and Credible. After that, the two AC power production units 2200A remain unchanged, while the other AC power production unit 2100A is modified to a 2100B configuration as shown on the left side of FIG. 2B.

The architecture of the power production unit 2200A in FIG. 2A is modified to obtain the power production unit 2200B of FIG. 2B. The components in Figure 2B; 2351B, 2361B, 2352B, 2362B, 2500B, and 2600B correspond to the components in Figure 2A, which are 2351A, 2361A, 2352A, 2362A, 2500A, and 2600A. In addition, although the configuration of the power production unit 2100B in FIG. 2B is different from that of the power production unit 2100A of FIG. 2A, some elements in the power production unit 2100B of FIG. 2B are different from those included in the power production unit 2100A of FIG. 2A Are the same. For example, the photovoltaic strings 2111B and 2112B of FIG. 2 are the same as the photovoltaic strings 2111A and 2112A of FIG. 2A, respectively. Similarly, the DC / AC inverter 2130B of FIG. 2B is the same as the DC / AC inverter 2130A of FIG. 2A.

The six (6) steps in the next paragraph are used to describe how to modify the structure of the power production unit 2100A to become the structure of 2100B. 2100B is like the structure configured on the left side of FIG. 2B. Step 1 is the configuration of adding a set of interception diodes 2311B between the solar panel strings 2111B and 2112B, and the three-phase DC / AC inverter 2130B blindly following the MPPT. Step 2 is to add a group of energy storage devices 2410B configured in the 2100B architecture. In step 3, the energy storage device 2410B is connected to the DC input terminal of the DC / AC inverter 2130B through another set of the interception diode 2312B and the switch SW1. Step 4: According to the direction of the designed MEUPT controller 2420B, add another three-phase DC / AC inverter 2130S (20kW) to the 2100B architecture to control the inverter 2130S. Step 5 is to connect the DC / AC inverter 2130S to the energy storage device 2410B through another set of interception diode 2313B and switch SW2. Step 6 is to connect the output of the inverter 2130S to the power meter 2351B and the electricity meter 2361B through the switch SW3. Note, note that the "cut-coupled diode group" referred to in this article can be the type of diode called "blocking diode" in the field of diodes. In addition, the switches SW1, SW2 and SW3 configured in Figure 1B allow 2100B to comply The implementation steps of the experimental design, when appropriate, the relevant devices are introduced into the experiment (or removed from the experiment).

The first night after configuration adjustment; switch SW2 and SW3 to open, SW1 to switch. In this way, the inverters 2130B and 2230B can start operation the next morning. Under this condition, the system performs all-weather operation on the first day. On this day, the meters 2351B and 2352B, which measure the two power outputs of the power generation units 2100B and 2200B, show that the cumulative readings for the day are the same. In addition, by measuring the increase in the voltage at the end of the energy storage device 2410B, it can be seen that the energy storage device 2410B starts to charge early. As shown by the day's cumulative readings of electricity meters 2361B and 2362B, these two power generation units 2100B and 2200B provide equal electrical energy to the three-phase AC grid. This experimental step indeed proves that the added interception diode group 2311B and energy storage 2410B will not change the power of the power generation unit 2100B and the generated electric energy.

The switches SW1, SW2, and SW3 are switched to the channel at night after the first day operation (the second night). Inverters 2130B and 2230B also started operation in the early morning of the next day, while inverter 2130S operated at a lower power within about 15 minutes after inverters 2130B and 2230B started to operate. After that, the inverter 2130S increases the DC / AC conversion power approximately every 2 minutes; this process of increasing the conversion power is consistent with the designed energy storage control program. The electricity provided by the two power production units 2100B and 2200B all day until close to sunset can be obtained from the readings of the two electricity meters at the end of the next day. As a result, the day's cumulative increase reading of the electricity meter 2351B (for the unit 2100B) reached more than twice the day's cumulative increase reading of the electricity meter 2352B (for the unit 2200B). Therefore, the results of the above-mentioned experimental results show that the cumulative increase of electric energy provided from the adjusted power generation unit 2100B to the power grid for a day is more than twice that of the cumulative increase of electric power provided by the unadjusted power generation unit 2200B. For the next six consecutive days, the switches SW1, SW2, and SW3 remained open, and the adjusted power production unit 2100B provided more than twice the power to the grid every day.

In the evening after these six days of experiments, disconnect the SW2 and SW3 switches. During the 5 consecutive days during which the switches SW2 and SW3 remain open, the power supplied from the power generating units 2100B and 2200B to the grid every day returns to the same amount of power. Later in the evening, SW2 and SW3 were switched to the channel again. And keep the switches SW2 and SW3 operating under the condition of continuous passage for the next 5 consecutive days, and the daily cumulative power supply power measured by the power generation unit 2100B once again becomes more than double the cumulative power supply power per day of the power generation unit 2200B.

As explained in the foregoing; the execution of this experiment can be confirmed without doubt; the predictions proposed in the patent publications (US2016 / 0036232 and US2017 / 0149250A1); the existence of residual electrical energy does exist in PV power plants. Especially in photovoltaic power stations, when the generated DC power is captured by the three-phase DC / AC inverter and provided to the grid, there is still residual power. And the MEUPT optimizer it invented / designed can capture and use this surplus energy to increase the power provided to the grid.

Section 9: Several Configuration Architectures for MEUPT Optimizer Design

The configuration-adjusted power production unit 2100B (as described in FIG. 2B) can be used as an example of the configuration of the MEUPT optimizer and integration into the PV power production unit. In this architecture, the MEUPT optimizer includes three sets of intercepting diode groups 2311B, 2312B, and 2313B; an energy storage 2140B and a MEUPT controller 2320B. Note that in the following, the intercepting diode group is referred to as a “intercepting component”.

As mentioned above and shown in Figure 2B; the connection of this MEUPT optimizer module. Please note that in this embodiment, the remaining power is captured passively by the energy store 2410B. Another power extractor is a module included in the three-phase DC / AC inverter 2130S. This power extractor extracts the energy stored in the energy storage device 2410B and provides it to the three-phase AC power grid. The AC power converted by the inverter 2130S is adjusted by the MEUPT controller 2320B. Proper design can make the power charged into the energy store 2410B and the power discharged from the energy store 2410B almost balanced. Therefore, during a certain period of time, the "net" electricity stored in the energy storage can be manipulated to minimize it. A smaller net power has the advantage that a smaller energy storage device 2410B can be used, but the price paid is that the MEUPT controller 2320B must be able to perform stricter and faster charge / discharge energy management requirements.

Another embodiment is depicted in FIG. 3, which illustrates the configuration of a photovoltaic power station 3000 containing a MEUPT optimizer, which includes only one AC power production unit 3100, which uses a 500kW solar panel string 3110 to convert solar energy Converted into DC power. In other words, the AC power production unit 3100 includes a DC power generation module 3110 and a three-phase DC / AC (500kW) inverter 3130. The power generation module 3110 uses 80 parallel strings of solar panels to generate DC power. Each of the 80 solar panel strings is composed of 25 solar panels in series; according to the manufacturer's declared value, each panel can produce 250W DC power under noon and clear skies. Note that the DC power generation module 3110 is referred to herein as a 500kW generator (80 * 25 * 250W = 500kW); and this photovoltaic power station is also referred to as a 500kW photovoltaic power station.

As shown in FIG. 3, the generator 3110 provides DC power to the three-phase DC / AC inverter 3130 (manufacturer claims 500KW inverter) through the interception coupling 3311. The generator 3110 also supplies the charged DC power to the energy storage 3410 via the interception coupling 3312. Therefore, the energy storage 3410 passively collects the remaining electric energy. DC power (or discharge) is then provided to another three-phase DC / AC inverter 3130S (manufactured by the manufacturer as 500kW) through the interception coupling unit 3313. The inverter 3130 operates according to the MPPT optimizer, while the inverter 3130S operates according to the MEUPT controller. The inverters 3130 and 3130S convert the DC power of the extracted generator 3110 into three-phase AC power, and then transmit the power to the power grid (same pair of cables) 3600 through the same transformer 3500.

The DC / AC inverters cited in the previous description can be divided into two types in use; namely, one type directly receives the direct current produced by the photovoltaic solar panel string, and the other receives the direct current from the energy storage. In this article and the detailed description of the following implementation methods, when it is necessary to distinguish between the types of inverters, the type of DC power received from a photovoltaic solar panel string is called a "PS DC / AC inverter"; Another type of power is called "ER DC / AC inverter". When a three-phase DC / AC inverter is used in this patent announcement, if there is a need to distinguish, the inverters are also classified, and are referred to herein as "PS three-phase DC / AC inverters" and " ER three-phase DC / AC inverter ".

Explain from a broader level; as shown in the configuration of Figure 4, the MEUPT optimizer is optimized for x MW photovoltaic power plants, which is a correctly set solar panel string with a rated power generation capacity of x MW. The produced DC power passes through the interception coupling device 4311 and is supplied to the manufacturer for a "PS three-phase DC / AC inverter" 4130 which claims "y MW". The remaining power that is not captured is sent to the energy storage 4410 through another interception device 4312 to be captured and stored. The stored residual energy is passed through another interception component, which is declared by another manufacturer as z MW "ER three-phase DC / AC inverter" 4130S, which converts the DC energy of the 4410 energy storage device into AC power. The inverter 4130 is regulated by the MPPT optimizer, while the other inverter 4130S is regulated by the MEUPT controller. Both inverters convert an appropriate amount of DC power into three-phase AC power; and provide three-phase AC power to the grid 4600 via the same transformer 4500. Please note that x = y = z = 0.5 in the configuration of this embodiment.

Figure 5 depicts another embodiment of incorporating a MEUPT optimizer into a large photovoltaic power plant. The power station is equipped with a solar panel string 5110 with a rated power of 0.5MW, and two three-phase DC / AC inverters 5130 and 5130S claiming 500kW. This embodiment illustrates another configuration of the MEUPT optimizer. The photovoltaic power plant 5000 can be regarded as including one AC power production unit (also referred to herein as "AC power production unit 5100"). The AC power generation unit 5100 contains a DC generator 5110, which is composed of a set of solar panel strings with a rated power of 500KW, and two three-phase DC / AC (each declared 500KW) inverters 5130 and 5130S. The generator 5110 uses 80 parallel-connected solar panel strings to generate DC power. Each group of strings connected in parallel is composed of 25 solar panels in series, and each solar panel has a power production capacity of 250W. The energy storage 5410 receives DC power from the generator 5110 through the coupling member 5311. The two three-phase DC / AC inverters 5130 and 5130S receive DC power from the energy storage 5410 through two intercepting diode components, respectively, and the two intercepting components include a intercepting component 5312 for the inverter 5130, and Interceptor 5313 for inverter 5130S. The inverters 5130 and 5130S are regulated by the MEUPT controller, and a proper amount of power is obtained from the energy storage 5410, and the DC power is converted into three-phase AC power, which is then supplied to the power grid 5600 via the transformer 5500.

In order to explain the configuration in Fig. 5 in a broader sense: an MEUPT optimizer is used to optimize an x MW photovoltaic plant. The photovoltaic power plant has an AC power production unit that contains strings of solar panels and has a DC power generation capacity of a total rated power x MW. The DC generator charges the energy storage device by means of a coupling device. The energy storage device then provides DC power to two three-phase DC / AC inverters through two independent sets of intercepting coupling components. The manufacturer claims that the conversion capabilities of the two "ER three-phase DC / AC inverters" are z1 and z2, which together add up to z1 + z2 = z MW. Both inverters are controlled by the MEUPT controller to convert the appropriate amount of DC power into three-phase AC power. The AC power generated by the two inverters is then supplied to the same pair of cables through the same transformer. The configuration described above is then redrawn in Figure 6. Note that x = 0.5, y = 0, and z = 1 in this configuration.

The description in this section will compare the two configurations depicted in Figures 4 and 6. In the configuration depicted in FIG. 4, the DC generator supplies DC power to a “PS three-phase DC / AC inverter” with a y MW power generation capability declared by the manufacturer. And charge the remaining power into the energy storage. In Figure 4, the energy storage device provides DC power to the inverter. The manufacturer claims a "ER three-phase DC / AC inverter" with a rated power of z MW. In the configuration shown in Figure 6, there is no "PS three-phase DC / AC inverter" (that is, y = 0), and all produced DC power will be charged into the energy storage device through the interception coupling; A set of independent intercepting components provides DC power to two "ER three-phase DC / AC inverters". Therefore, in the configuration of FIG. 3, x = y = z = 0.5; in the configuration of FIG. 6, x = 0.5, y = 0, and z = 1. In another embodiment of FIG. 6, the energy storage device 6410 is not provided, and instead, the solar panel string 6110 directly supplies DC power to the inverter 6130 through the interception coupling component 6311.

Until now described, the only remaining design focus of the MEUPT optimizer is to determine the relationship between the power matching optimization parameters between the representative parameters of the rated capacity of the solar panel string and the representative parameters of the inverter's rated capacity. Specifically, the relationship between the values of x, y, and z is confirmed under the optimized conditions. It must be reminded that in the second section, the total value of y + z is usually not greater than the value of x in traditional photovoltaic power plants.

Also note that the value of x is defined as the MW power generation capacity of the rated DC power production capacity of the PV string; the value of y is set as claimed by the manufacturer, and the DC power supplied from the PV string is subject to "PS three-phase DC / AC inverter The total (MW) power generated by the converter; and the z value is set to the total (MW) power generated by the manufacturer claiming that the DC power provided by the energy storage device is converted by the "ER three-phase DC / AC inverter".

For example, in Figure 6, x is equal to 0.5, which means that the manufacturer ’s declared total power generation capacity of the photovoltaic power plant is 0.5MW; y is equal to 0, which means that there is no “PS three-phase DC / AC inverter” installed; The total total rated capacity of the two "ER three-phase DC / AC inverters" declared by the manufacturer is 1MW; it is the two inverters that receive DC power from the energy storage and convert the DC power into three-phase AC The result of the combined electricity. Please note that in the above two configurations, the value of y + z is not less than twice the value of x. Unless otherwise stated, the "rated capacity" mentioned in the text may also be referred to as the "rated power" of the equipment.

Section 10: The relationship of power matching optimization

Due to different (industrial) fields, the definition of the rated power of solar panels is different from the definition of the rated power of DC / AC inverters. The rated power of a solar panel is defined as the maximum direct current power that a solar panel can produce when the sun is orthographic in the clear sky at noon. Solar panel manufacturers use a specific type of lighting fixture (herein referred to as a "standard light fixture") to illuminate the luminous flux passing through the surface of the solar panel vertically to simulate orthographic sunlight on a clear midday sky. Therefore, manufacturers claim that the power production capacity is indeed very close to that of a true DC generator. Experiments conducted by the present inventors also confirmed the above inference. Therefore, the declared value of the total DC power generation capacity of the photovoltaic solar panel string is credible; therefore, when describing the rated power of the solar panel string in this article, we will not add "the declared capacity of the manufacturer". On the other hand, the DC / AC inverter manufacturing industry defines the rated power of the DC / AC inverter according to the specifications of the traditional power industry, which is referred to herein as the "power grid specification." The specifications and definition of DC / AC inverter capabilities are detailed below.

The AC power industry enforces a specification (called the grid specification) to ensure that the three-phase AC power constructed can achieve the claimed power transmission capacity. Three-phase AC grid power consists of 3 or 4 power lines. Each pair of power lines between power lines can be regarded as one phase, providing positive (/ cos) sine wave voltage and current that change with time. The sine wave that changes with time is described in this article. Also called "time-varying function". Grid specifications define the declared voltage value specification as the "standard" maximum voltage that the power line can withstand (referred to as "line voltage"). Similarly, the maximum current declared in this specification refers to the maximum current that the power line can carry (referred to as "maximum phase current"). When the device is manufactured in accordance with grid practices, the voltage declared in the device specification is the maximum voltage that all relevant components should withstand. Similarly, the maximum current declared in the device's specifications is the maximum current carrying capacity of all related components connected to the same phase in a pair of power lines. The time-varying functions of the voltage and current of these related components also need to conform to the sine (/ cosine) function of each phase in the AC grid.

Restate as follows; the specified voltage of the three-phase DC / AC inverter is defined as the line voltage of the three-phase power supply; the specified maximum current is defined as the maximum current carrying capacity that a pair of power lines in each phase can bear; and The specified maximum power is defined as the sum of the maximum power capabilities that the three phases can withstand. In other words, when the grid specifications are met, each phase of the power line and connected electrical equipment should be able to transmit one-third (1/3) of the specified maximum power, in other words, a three-phase DC / AC inverter The manufacturer's "declared power rating" is 3 * U * I, where U is the phase voltage and I is the phase current. Each pair of power line energy and related power devices can withstand U * I power, or 1/3 of the "manufacturer's declared power rating"; each module connected to a pair of power lines also needs to be capable of carrying or transmitting when the grid specifications are met Declared 1/3 rated power.

Take a three-phase DC / AC inverter as an example. Its setting specifications are "AC voltage = 315VAC; maximum current is 916 amps; maximum power output is equal to 500kW". In the specification, "AC voltage is equal to 315 VAC" should be understood as: "The output AC line voltage of this inverter is 315 volts. Or, when the three-phase balance is achieved, the phase voltage U of each phase is U = 315 / 1.732 = 181.9 volt (Where 1.732 is the square root of 3, which is the ratio of line voltage to phase voltage). The set "maximum current = 916 amps" is understood as the power line and all components in each phase are designed to ensure I = 916 amps of current carrying Capacity. The set “maximum output power = 500kW”; it should be understood as the maximum DC / AC inverter conversion and power transmission capacity of all components in each DC / AC conversion stage = U * I = 181.9 * 916 = 500 / 3KW; The total maximum power conversion capacity and output capacity of the relevant modules of the three conversion phases are the sum of each phase, 3 * U * I = 3 * 181.9 * 916 = 500kW, which is the definition of "rated power declared by the manufacturer" (= 3 * U * I), in line with the grid specifications described in the previous paragraph.

The three phases of the three-phase DC / AC inverter are strictly related to each other with a phase difference of 120 degrees. In other words, when a pair of power lines (phases) provide a time-varying power function of U * I sin ² (ωt); the time-varying power function of the second phase is U * I sin ² (ωt + 120 °) ; The third phase provides a time-varying power function of U * I sin ² (ωt-120 °). In other words, each pair of power lines in the three phases provides three interconnected pulsating AC power systems with strict correlation, they cannot be changed randomly. Please note that the inverter power is under this strict correlation limit; this paper finds and proves that the DC / AC power conversion capability P (t) of the inverter is not equal to the set "manufactured power rating". The power conversion capability P (t) of the inverter derived in this paper is a function of time and is derived from the inverter power conversion capability based on the three-phase AC power limit defined by the grid code.

In other words, the DC / AC power conversion capability P (t) of the inverter must be derived from the sum of the time-varying power output of the three phases; there is a strictly associated 120 ° phase difference between them; And it must conform to the power wave form of sin ² (ωt) or cos ² (ωt) square sine oscillating with time; it must also be synchronized with the power grid (with the same phase and frequency) so that the angular frequency ω becomes a constant constant.

Now, let us derive the time-varying power conversion capability P (t) of the three-phase DC / AC inverter. Each phase of his DC / AC inverter conversion is a function of time. So the power conversion capability of this three-phase DC / AC inverter is P (t) = U * I * (sin ² (ωt) + sin ² (ωt + 120 °) + sin ² (ωt-120 °)). As mentioned above, U is the phase voltage, I is the phase current, and ω is the fixed angular frequency of the grid. In addition, mathematical axioms can prove that sin ² (ωt + 120 °) + sin ² (ωt-120 °) = cos ² (ωt) +1/2. Therefore, the derivation of the power conversion capability P (t) of the three-phase DC / AC inverter as a function of time is: P (t) = U * I * (sin ² (ωt) + sin ² (ωt + 120 °) + sin ² (ωt-120 °)) = U * I * (sin ² (ωt) + cos ² (ωt) +1/2) = U * I * (1 + 1/2) = 3/2 (U * I).

As a result of the derivation above, the sum of the power of these strictly related three pulsating power strings in the three phases is constant. That is, the total output power of these three pairs of power lines is constant. In other words, the sum of the power of three single-phase DC / AC inverter modules with three phase correlations is constant (3 / 2U * I). However, this constant is only equal to half (1/2) of the "declared power capability (3U * I)". This is the relationship between the power conversion capability of the three-phase inverter and the "power capability declared by the manufacturer" of the three-phase DC / AC inverter when the grid specifications are met.

Please note that when the grid specifications are met, the “manufactured nominal power” of the three-phase DC / AC inverter or the “manufactured power capability” mentioned earlier is 3 * U * I. Compare it with the DC / AC conversion capability P (t) = 3/2 (U * I) derived above; it can be clearly shown that the DC / AC power of the three-phase DC / AC inverter The conversion capability is only half of the "manufacturer's claimed power capability".

Just like the previous example; if that three-phase DC / AC inverter is used. They declared the setting "AC voltage = 315 VAC; maximum phase current = 916 amps; maximum power output = 500kW". We first confirm to the manufacturer that his declared maximum power of 500kW is indeed equal to 3 * U * I, where U is the phase voltage obtained from the specified line voltage and I is the declared maximum current. According to the above derivation, the power conversion capacity of this three-phase DC / AC inverter is only equal to 3/2 * U * I = 250kW. This DC / AC power conversion capability is also confirmed by the unidirectional U * I test results.

The relationship between the parameters x, y, and z (as defined herein) for power matching optimization is that the value of (y + z) should not be less than the value of 2x. The relevant photovoltaic power plant consists of a string of x MW PV solar panels; and includes a "PS three-phase DC / AC inverter" with a total "manufactured power" of y MW; a total "manufacturer declared power with z MW "ER three-phase DC / AC inverter". "PS three-phase DC / AC inverter" and "ER three-phase DC / AC inverter" can be controlled by one or more MPPT controllers, or by one or more MEUPT controllers. However, in order to comply with MEUPT's optimization requirements, it is best that all DC / AC inverters are controlled by MEUPT controllers.

Section 11: Summary

FIG. 7 schematically describes the configuration of the PV solar power station 7000. The power station includes all solar panels of x MW arranged in a solar panel string 7100. The DC power generated in the solar panel string 7100 provides DC power input to a group of three-phase DC / AC inverters 7301 through the interception coupling device 7201; and the remaining power is charged to the energy storage unit 7400 through the interception coupling device 7202 in. The energy storage device 7400 provides a DC power input to a group of three-phase DC / AC inverters 7302 through a coupling unit 7203. The AC power output of the two three-phase DC / AC inverters 7301 and 7302 passes the transformer 7500 to supply the boosted three-phase AC power to the power grid 7600. The total power of the "manufactured capacity" of inverter 7301 is y MW. The total power of the "manufacturer declared capabilities" of inverter 7302 is z MW. The value of (y + z) is not less than the value of 2x. Please note that when a similar configuration is used to describe the traditional photovoltaic power plant described in Section 2, the value of (y + z) is usually not greater than the value of x. Therefore, when there is a residual power storage device of the above design, and the design of the (y + z) value is greater than x or even better 1.1 x; this means that some residual power can be captured to enhance the power provided to the power grid .

Both inverters 7301 and 7302 can be controlled by the MEUPT controller described herein. In some embodiments, the MEUPT controller can operate some, one or none of the inverters. In addition, in some embodiments, one or some of the 7201, 7202, and 7203 interception coupling modules may be omitted in the power generation configuration. The PV solar panel string 7100 provides DC power input to the inverter 7301. Therefore, 7301 is referred to herein as a "PS inverter." The energy store 7400 provides DC power input to the inverter 7302. Therefore, 7302 is referred to herein as an "ER inverter." The terms "manufactured nominal power" and "manufactured power generation capability" are both referred to herein as "declared power".

Once again, the components and configuration depicted in FIG. 7 are explained: The PV power plant 7000 includes an x MW solar panel string 7100 as a DC generator. The DC generator 7100 is provided to the "PS converter" 7301 of y MW through a decoupling component 7201; and the remaining power is charged into the energy storage 7400 through another decoupling component 7202. The 7400 is provided to the "ER inverter" 7302 with a "declared power" of z MW through the interception coupling unit 7203. The three-phase AC output power of all three-phase DC / AC inverters 7301 and 7302 provides the converted three-phase AC power to the grid 7600 through a transformer 7500. In some embodiments, the (y + z) value is not less than a 2x value. However, when there is the above-mentioned residual electric energy storage device, and the (y + z) value is greater than the x value, the design can obtain a part of the benefits from the increase of the sales power on the grid.

According to the principles described herein; a MEUPT optimizer can serve small PV plants or large PV plants with one or more AC power production units. In addition, through properly designed interception coupling components, the energy of the energy storage device can be prevented from leaking through the PV solar panel string. In addition, through properly designed interception coupling components, the phenomenon of "mutual power annihilation" found by the inventors can be avoided. Moreover, the energy storage can be used to capture and receive the remaining power after the power extraction of the "PS inverter", or to receive all the generated DC energy before any energy extraction process. Finally, the MEUPT optimizer design described above can also serve PV power plants with single-phase DC / AC inverter configurations.

Section 12: Design Limitations of MEUPT Controller

FIG. 8 shows a MEUPT controller 8000 (also referred to as a “system controller”) as a representative example of the MEUPT controller 2320B of FIG. 2B. The MEUPT controller 8000 includes three executable components: a detection module 8100, a determination module 8200, and a message transmission module 8300.

The detection module 8100 measures the energy level stored in the energy storage device 8400. Examples of energy storage devices include energy storage device 2410B in FIG. 2B, energy storage device 3410 in FIG. 3, energy storage device 4410 in FIG. 4, and energy storage device 5410 in FIG. The energy store 6410 in FIG. 6 and the energy store 7410 in FIG. 7.

A judging module 8200 determines the appropriate power draw size. This can correctly maintain the power charged to the energy storage 8400 and the power extracted from the 8400 to be almost balanced, and the stored "net" power is almost Is zero.

The message transmission module 8300 transmits the encoded information of the above determined appropriate extracted power size to the DC / AC inverter 8500 of the remaining power extraction for interpretation and execution of the encoded message, so that the inverters can use the specified power extraction size Continuous operation allows the power output from the energy storage to be almost balanced with the charged power. Examples of the inverter 8500 that extracts electric energy from the energy storage 8400 are the inverter 2130S in FIG. 2B, the inverter 3130S in FIG. 3, the inverter 4130S in FIG. 4, and the inverter 5130S in FIG. , Inverter 6130S in FIG. 6, inverter 7302 in FIG. 7.

In order for the MEUPT optimizer to produce economic benefits, the design of the MEUPT controller needs to consider the following parameters and variables: (1) the energy storage capacity of the energy storage device 8400; (2) the rise / fall of the conversion power of the DC / AC inverter 8500 Speed; (3) the current-voltage characteristics of solar panels; (4) the climate of the photovoltaic power plant's location; (5) how the MEUPT controller and the remaining DC / AC inverters work together to make the energy stored in the storage battery charge The difference from the power drawn from the energy store is minimized (or balanced). Only after considering all the aforementioned parameters and variables, can a practical custom MEUPT controller be designed for each photovoltaic power plant or any group of photovoltaic strings in a certain power plant.

Section 13: How to Design a MEUPT Controller

In practical applications, it is not economical to design a customized MEUPT controller for each PV power station or each group of PV strings. On the other hand, when custom-designed controllers are not allowed; it is very difficult to design a MEUPT controller that can be used for all PV strings or power stations. However, what can be used is; the terminal voltage of the energy storage can be regarded as a measurement value that is affected by the combination of 5 parameters and variables. Therefore, when the terminal voltage of the MEUPT energy storage device is selected as the judgment parameter, the above five design parameters can be relatively divided into two parts for consideration.

After comparing the measured terminal voltage with a set of "standard voltage intervals" set in the field; the inventor clearly knows that the DC power capture and DC / AC conversion power currently performed by the system can be performed at the moment of execution. Quantified as three DC power capture situations (1) too low, (2) too high, or (3) just right. Therefore, the design of the MEUPT controller can be divided into 1) a general industrial controller, and 2) a customized field setting "standard voltage interval" table (hereinafter referred to as "voltage interval table") to complete.

Once a field-set voltage interval meter is constructed for a PV power plant; the voltage interval meter can work in conjunction with an industrial controller to complete the required MEUPT controller functions. As shown in FIG. 8, the industrial controller includes a detection module, a determination module, and a message transmission module. In this case, the detection module 8100 is used to measure the terminal voltage of the energy store 8400. The determination module 8200 is used to compare the measured voltage with the voltage interval table; in order to determine that the appropriate amount of power captured and the amount of charging power are almost balanced. The message transmission module 8300 then transmits the above-determined message code of the appropriate power capture size to the DC / AC inverter that captures the remaining power; so that the inverter can continuously operate under this specified power capture size, allowing the storage The power input and output of the Energy Saver 8400 are close to balance. In this way, the "net" electricity stored can be made almost zero.

In one embodiment, the detection module 8100 of the MEUPT controller 8000 is designed to measure the terminal voltage of the remaining power storage device 8400 in real time. The determination module 8200 can still be designed to perform the comparison between the terminal voltage and the standard voltage (comparison between the measured voltage and the voltage interval table) in a specified time interval. The comparison result may be divided into one of the following three cases: (1) If the comparison of the measured voltage and the voltage interval meter shows that the power is captured too low, the controller 8000 can request (through the message transmission module 8300) When the three-phase DC / AC inverter 8500 switches to the next specified time interval, it increases the power capture; (2) If the comparison of the measured voltage and the voltage interval meter shows that the power capture is too high, the controller 8000 can ( (Via the message transmission module 8300) requires the three-phase DC / AC inverter 8500 to switch to the next specified time interval to reduce power capture; (3) if the measured voltage is compared with the voltage interval table, the power capture is displayed Yes, the controller 8000 may require the three-phase DC / AC inverter 8500 to maintain the same power extraction at the next specified time interval (at least until the next comparison occurs).

When the adjustment step of the DC / AC inverter's power capture / conversion is sufficiently small, the above design can be applied to all types of energy storage and its power storage capacity; it can be applied to all types of DC / AC inverters to capture power The speed of the power up / down adjustment; it can be applied to the current-voltage characteristics of various solar panel strings; and it can be applied to the climate of photovoltaic power stations in all different regions. The most important thing is that the controller can instruct the three-phase DC / AC inverter to perform extremely fast adjustment when extracting power from the energy storage device.

Typical traditional centralized three-phase DC / AC inverters can be quickly operated with very small adjustment steps when instructed. It is already equipped with a communication channel and is known in the art as a "dry box" (referred to herein as this term). The dry box is usually a set of 6-bit communication channels through optical signals. We can use an encoding-decoding technology to control more than 6 power capture size communication channels through a dry box. This technology allows transmission of up to 26-bit change messages, that is, 64-step messages to control the specified amount of captured power. By adjusting the power capture size up to 64, it is possible to easily technically achieve the demand that the net balance of input energy and output energy of the energy storage device is close to zero.

Section 14: PV Power Plant with MEUPT Optimizer

As shown in FIG. 9, a PV power plant 9000 includes a MEUPT optimizer 9200 with a MEUPT controller 9210, and a MEUPT controller 9200 includes three executable components; that is, a detection module 9211 for measuring the remaining energy storage device 9400. The terminal voltage of the module; the judgment module 9212 is used to compare the measured voltage with the voltage interval table of the photovoltaic power plant; the message transmission module 9213 informs the three-phase DC / AC inverter 4502 to rise and fall through the message transmission module 4213 Or keep it at the same power capture size. Modules 9211, 9212, and 9213 in FIG. 9 are exemplary cases of components 8100, 8200, and 8300 in FIG. 8, respectively. The energy storage device 9400 of FIG. 9 is an exemplary case of the energy storage device 8400 of FIG. 8. The inverter 9502 is an exemplary example of the inverter 8500 of FIG. 8.

The PV plant 9000 also contains a string of 9100 PV panels. The solar panel string 9100 converts solar energy into DC power; the generated DC power is transmitted to the remaining electric energy storage device 9400 through the interception coupling component 9320. The 9400 transmits DC power to the three-phase DC / AC inverter through the interception coupling component 9330器 9502. The solar panel string 9100 in FIG. 9 is to provide a concentrated DC power source for charging the energy storage device. Examples thereof may be the solar panel strings 2111A and 2111B in FIG. 2B, and the solar panel string 3110 in FIG. 3, The solar panel string 4110 in FIG. 4, the solar panel string 5110 in FIG. 5, and the solar panel string 7110 in FIG. 7. An example of the decoupling component 9320 in FIG. 9 may be the decoupling component 2312B in FIG. 2B, Examples of the decoupling component 3312 in FIG. 3, the decoupling component 4312 in FIG. 4, the decoupling component 5311 in FIG. 5, the decoupling component 6311 in FIG. 6, and the decoupling component 7202 in FIG. 7. The interception coupling part 9330 in FIG. 9 is the interception coupling part 2313B in FIG. 2B, the interception coupling part 3313 in FIG. 3, the interception coupling part 4313 in FIG. 4, the interception coupling part 5313 in FIG. 5, and the interception coupling in FIG. 6. Part 6313 and the intercept coupling part 7203 in FIG. 7.

As described in this article, the MEUPT controller 9210 instructs the three-phase DC / AC inverter 9502 to extract appropriate power from the energy storage 9400 to balance the input power from the solar panel string 9100 to charge the energy storage; resulting in energy storage The "net" value of charging or output power in the charger 9400 is close to zero. Therefore, a small energy storage 9400 pairs of PV power stations can become the correct design. The AC power converted and output by the DC / AC inverter passes the transformer 9600 to the boosted AC power to the connected power grid 9700.

The term "executable component" as used herein is applied to the fields related to Figs. The term "executable component" is a structure name that is well known to those skilled in the computer field. The definition of "calculation" can be software, hardware, firmware, or a combination thereof. For example, when implemented in software, it is recognized by those of ordinary skill in the (computer) field that the structure of an executable component may include software targets, programs, and methods that are executed on a computing system, including whether or not this structure is included in the system computing heap. Such an executable component exists, or the executable component exists on a computer-readable storage medium.

In the following case, one of ordinary skill in the art can recognize that when the structure of the execution component exists on a computer-readable storage medium, it is interpreted by one or more processors of the computing system (for example, by processing Processor threads) to guide the computing system to perform functions. This structure may be a computer-readable function performed directly by the processor (this is the case when the executable component is binary). Alternatively, the structure can be structured to be interpretable and / or compiled (whether in a single or multiple stages) to produce such a binary file that can be directly interpreted by a processor. When using the term "executable component", the case structure of the executable component can be fully understood and mastered by those skilled in the computer field.

A full understanding of "executable components" by those skilled in the art may also include structures implemented exclusively or near exclusively in hardware or firmware, such as field programmable gate arrays (FPGAs). Integrated Circuit (ASIC) or any other special purpose circuit. Therefore, the term "executable component" is a structural term clearly understood by those of ordinary skill in the computer field, whether implemented in software, hardware, or a combination of both.

The invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are intended to be illustrative in all respects and not restrictive. Therefore, the patentable scope of the present invention is determined by the appended claims rather than by the foregoing description. The meanings and all changes within the equivalent scope of the claims are included in the scope of their claims.

Although this disclosure has been disclosed as above in the form of implementation, it is not intended to limit this disclosure. Any person with ordinary knowledge in the field can make various changes and modifications without departing from the spirit and scope of this disclosure. Therefore, this disclosure The scope of protection shall be determined by the scope of the attached patent application.

Claims (8)

An energy storage system includes: an energy storage device that is charged with DC power energy and releases DC power to a DC / AC inverter, wherein the DC power energy is composed of a xMW solar panel string, where x The value is the MW power generation capacity of the rated DC power production capacity of the solar panel string, and the energy capacity of the energy storage device required per MW of the solar panel string is less than 2 Faradays; a system controller for controlling the The DC power released by the energy storage device to the DC / AC inverter makes the DC power stored in the energy storage device and the power released to the DC / AC inverter almost balance each other. The system controller includes: A detection module configured to measure the amount of energy stored in the energy storage device; a determination module configured to evaluate whether the measured energy storage level of the energy storage device is to be adjusted for power release; And a message transmission module, which is configured to compile a specific instruction to execute the adjustment of the amount of release into a message code when the determination module determines that the amount of electricity release is to be adjusted, and transmit the message code to the DC / AC inverter Device. The energy storage system according to item 1 of the scope of patent application, wherein the detection module measures the amount of electrical energy of the energy storage device by measuring the terminal voltage of the energy storage device. The energy storage system described in item 2 of the scope of the patent application uses real-time detection to detect the terminal voltage of the energy storage. The energy storage system according to item 3 of the scope of patent application, wherein the determination module is configured to perform periodic power release adjustment assessment only at specified time intervals. The energy storage system according to item 1 of the scope of the patent application, wherein the determination module is configured to periodically perform an assessment of power release adjustment at a specified time interval. The energy storage system according to item 1 of the scope of the patent application, wherein the message transmission module is configured to send the coded message to the inverter through the dry junction box of the DC / AC inverter. The energy storage system according to item 1 of the patent application scope, wherein the message transmission module is configured to transmit a corresponding encoded message to each of the plurality of DC / AC inverters including the DC / AC inverter. An inverter. According to the energy storage system described in item 1 of the scope of patent application, the message transmission module is configured to transmit a corresponding coded message to the DC / AC inverter through the dry box of the DC / AC inverter. At least one of a plurality of DC / AC inverters.