KR102554154B1 - Apparatus for power compensation of photovoltaic module - Google Patents

Abstract

The photovoltaic power generation system for compensating the output of a photovoltaic module in a shaded area according to the disclosed present invention includes a plurality of photovoltaic (PV) modules 10 and an output compensation device connected to the plurality of photovoltaic modules 10, respectively ( 100). The output compensating device 100 includes an N-Buck DC / DC converter 120 that changes and outputs the DC power generated in the PV module to step-down or boost, and an N-Buck DC / DC converter in the PV module ( 120) and a sensor unit 110 that senses the current and voltage supplied to the PV module and the temperature of the PV module, and the sensor unit continuously monitors the current and voltage supplied by the PV module and tracks the maximum power point (MPPT: A microcontroller 130 including an MPPT control unit 132 that tracks the maximum power point (MPP) of the PV module using a Maximun Power Point Tracking (MPP) algorithm to maintain maximum output power, and the N- and a converter controller 140 that controls the buck DC/DC converter to output a voltage corresponding to the maximum power point tracked by the MPPT controller.

Description

Output compensation device of photovoltaic module {Apparatus for power compensation of photovoltaic module}

The present invention relates to a solar power generation system that compensates for the output of a solar module in a shaded area.

A photovoltaic power generation system converts solar energy into electricity and is composed of a photovoltaic (PV) module and a power conditioning system (PCS). In order to transmit DC power generated by solar power to the AC power system, a solar inverter, which is a power converter that converts direct current to alternating current, is used. This solar inverter consists of two parts. The function of increasing the voltage to a high voltage suitable for the next step and adjusting the solar module to generate maximum power is the direct current (DC)-direct current (DC) converter part at the front stage that performs MPPT (Maximum Power Ponit Tracking), It is a direct current (DC)-alternating current (AC) inverter part at the back stage that converts the DC power appropriately boosted at the front stage into AC power according to the power system and transmits it.

Most solar power generation systems use a method of connecting multiple PV modules (panels) in series to create a string and converting it into a single large-capacity power converter, which lowers the initial installation cost, but causes some PV modules to shade or pollute. There is a problem that the amount of power generation rapidly decreases depending on the degree of this. This is because when there is a problem with some PV modules constituting the string and the output (current) partially decreases, a current bottleneck occurs due to the nature of the series connection circuit, reducing the total current. Eventually, the failure of one part spreads to the whole, drastically reducing the total amount of power generation. A representative case is a partial shading phenomenon in which some modules are shaded in a roof-top PV system installed on the roof of a house or building. In addition, even in normal weather, the angle of light incident on each PV module changes according to the movement of the sun, and this causes a difference in power generation current. Module mismatch is a similar phenomenon.

As a representative output compensation technology to solve this problem, there is a micro-inverter method in which one small inverter (micro inverter) is installed per PV module. The microinverter is not a method of converting the DC electricity collected from the entire string at once, but a small capacity DC-AC conversion in the microinverter installed in each module, and then connecting the small output alternating current to a common parallel circuit to collect it and use it in the power system. It is a distributed system that transmits Since the micro-inverter method uses a dedicated inverter for each individual module, it can have a maximum power point tracking (MPPT) control function for each solar cell module, allowing more power to be generated.

However, micro-inverters are effective in shady places, but micro-inverters installed for each PV module are DC-AC inverters with the same capacity as panels, and are more expensive and less efficient than DC-DC converters. After all, it is not profitable compared to investment to install in all PV modules, so it is used only when space is limited or shade is severe.

In order to solve the disadvantages (economic efficiency) of the micro-inverter method, a micro-converter method in which a small-capacity DC-DC converter (DC optimizer) is installed for each PV module has recently been developed. This is a distributed modular structure in which the primary DC boost is performed using a micro-converter that performs DC-DC conversion for each PV module, and the secondary DC-AC conversion is performed by collecting each boosted DC power. This microconverter method divides the primary-side DC-DC converter, which was in charge of maximum output point tracking (MPPT) and boosting in the conventional centralized string inverter structure, into a number of small-capacity modules, each of which is made into a microconverter, and installed for each PV module. It is designed to perform maximum output point tracking (MPPT) control suitable for the module situation. Therefore, similar to the microinverter method, the microconverter installed in each individual module can perform maximum power point tracking (MPPT) control, enabling more power generation. A microconverter is a DC-DC converter, so it has the advantage of being significantly cheaper than a microinverter that converts DC-AC by less than half and having excellent efficiency.

Republic of Korea Patent Registration No. 10-1408855 (registered on June 11, 2014)

The present invention has been devised in view of the above, and when some shades are generated, the power generation is not constant and the output is different for each solar module, so that the lowest solar module is solar to compensate for the drop in total energy output Its purpose is to provide an output compensating device for the module.

An apparatus for compensating the output of a photovoltaic module according to the present invention for achieving the above object relates to a device for compensating output by being connected to a plurality of photovoltaic (PV) modules, respectively, and direct current power generated from the PV module. N-Buck DC / DC converter that changes and outputs step-down or step-up; A sensor unit for sensing current and voltage supplied from the PV module to the N-Buck DC/DC converter; The sensor unit continuously monitors the current and voltage supplied by the PV module and calculates the maximum power point (MPP) of the PV module using a maximum power point tracking (MPPT) algorithm. A microcontroller to which an InC algorithm is applied; and a converter controller for controlling the N-Buck DC/DC converter to output a voltage corresponding to the maximum power point tracked by the MPPT controller.

According to the present invention, the efficiency of the photovoltaic power generation system is eventually increased by compensating for the drop in output caused by the photovoltaic module having partial shade.

1 is a schematic diagram of an output compensating device for a solar module according to an embodiment of the present invention;
2 is a block diagram of an output compensating device for a solar module according to an embodiment of the present invention;
3 is a circuit diagram of an output compensation device to which the N-Buck DC/DC converter of FIG. 2 is applied;
Figure 4 is a circuit diagram of the switch on (ON) / off (OFF) state of the N-Buck DC / DC converter of Figure 2;
5 is a flowchart of an InC algorithm according to an embodiment of the present invention;
6 and 7 are diagrams showing a simulator of the power follow-up value of the InC algorithm of FIG. 5;
8 and 9 are diagrams for explaining the tracking of the IV and PV characteristics of the solar cell module and the maximum tracking point of the MPPT control unit.

The above objects, features and other advantages of the present invention will become more apparent by describing preferred embodiments of the present invention in detail with reference to the accompanying drawings. Hereinafter, a junction box-integrated power compensation device for a solar cell module according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

Referring to FIGS. 1 and 2 , the device 100 for compensating the output of a photovoltaic module according to an embodiment of the present invention is connected to a plurality of photovoltaic modules (PV 1 to PV N) 10 , respectively.

The output compensation device 100 includes a sensor unit 110, an N-Buck DC/DC converter 120, a microcontroller 130, a converter control unit 140, and a communication unit 150.

The sensor unit 110 includes a voltage sensor and a current sensor for detecting the output current and voltage of the PV module 10, and these voltage sensors and current sensors use various technologies, for example, very low resistance or current (voltage) It can be realized by a technique using a probe or the like.

Meanwhile, the sensor unit 110 may further include a temperature sensor. The temperature sensor is provided in a connection part with the PV module 10 to sense the temperature of the PV module 10 .

Current, voltage, and temperature information sensed by the sensor unit 110 are transferred to the microcontroller 130 . These current and voltage data can be used for system monitoring purposes. And, the temperature data, especially the temperature data of the PV module, indicates a kind of failure and problem of the PV module, and also acts as a coefficient of output power production.

The N-Buck DC/DC converter 140 converts and outputs DC power generated from the PV module 10 by step-down or boost, and an N-Buck converter circuit is applied. 3 shows a circuit diagram of an output compensation device to which an N-Buck DC/DC converter applied to an embodiment of the present invention is applied, and FIG. 4 shows a switch on/off of the N-Buck DC/DC converter. It shows the circuit diagram of the state. The power step-down or boosted by the N-Buck DC/DC converter 140 flows into the inverter 20 and is delivered to the final load. Since types and operations of DC/DC converters are widely known in the prior art, a detailed description thereof will be omitted.

The microcontroller 130 includes an MPPT control unit 132 and an abnormal state detection unit 134.

The MPPT control unit 132 continuously monitors the current and voltage supplied by the PV module 10 and uses a maximum power point tracking (MPPT) algorithm to determine the maximum power point (maximum power point) of the corresponding PV module 10. It maintains the maximum output power by following MPPT (Maximun Power Point). According to an embodiment of the present invention, an Incremental Conductance (InC) algorithm is applied to the MPPT algorithm. Generally, the Perturb and Observe (P&O) algorithm is mainly used as the MPPT algorithm, but according to the present invention, the InC algorithm having high efficiency is applied.

6 and 7 show simulation values of the P&O algorithm and the InC algorithm.

Referring to FIG. 6, when insolation continues at 10Hz with a control period of 10Hz using the P&O algorithm, the power tracking value (blue) shows an approximate convergence to the maximum output power (red) of the solar cell module. In addition, it can be seen that the inverter power tracking for the maximum output power of the solar cell module accurately converges to the maximum power without a tracking error after performing the algorithm 8 times when solar radiation continues at a 10Hz control cycle using the InC algorithm.

Referring to FIG. 7 , it can be seen that the simulated value has a follow-up error at the same rate as when the amount of insolation varies from 1000 W/m2 to 500 W/m2 with a 10 Hz control cycle using the P&O algorithm. In addition, it can be seen that the maximum power is accurately converged after performing the algorithm 8 times even when the solar radiation varies from 1000 W/m2 to 500 W/m2 with a 10 Hz control cycle using the InC algorithm. As such, it can be confirmed in the simulation that the InC algorithm is superior to the existing P&O algorithm in MPP tracking.

8 schematically shows characteristics of a current vs. voltage curve (solid line) in a solar cell, and FIG. 9 shows curves for three different temperature conditions. Here, the temperature may correspond to the solar radiation condition. Also, the dotted line indicates a power scale curve corresponding to each curve, and is determined by multiplying voltage and current.

Referring to FIG. 9 , it can be seen that the current rapidly drops when the voltage increases to a certain extent for all temperature conditions. As the current value decreases, the power scale also rapidly decreases. In order to increase the output efficiency of the PV module, it is necessary to track the maximum power point in the graph of the drawing and control the voltage corresponding to the maximum power point to be output from the output terminal. The maximum power point corresponds to the point where the product of the sensed voltage and current is the largest.

The abnormal state detection unit 134 determines that there is an abnormality when the detected value of the temperature sensor exceeds a predetermined reference value, and sends a control command to the converter control unit 140 through the microcontroller 130 to transmit a DC/DC converter ( 120) to turn off the internal circuit to block the operation of the internal circuit, thereby blocking the transmission of power to the outside or blocking the driving of the PV module.

The converter controller 140 controls the DC/DC converter 120 to output a voltage corresponding to the maximum power point according to the maximum power point followed by the MPPT controller 132 . That is, the converter controller 140 transmits a duty cycle control signal to the DC/DC converter 120 according to the maximum power point calculated by the MPPT controller 132 to adjust the output voltage.

The communication unit 150 serves to transmit various types of sensing data of the sensor unit 110 to the external monitoring device 300 . The information transmitted to the monitoring device 300 enables real-time monitoring and analysis of the corresponding PV module 10 and displays PV modules with shaded areas. Here, by having a unique ID for each individual PV module 10, identification, individual monitoring, and individual maintenance of the corresponding PV module are facilitated.

The operation of the photovoltaic system for compensating the output of the photovoltaic module in the shadow area according to the embodiment of the present invention having the above structure will be described as follows.

First, the voltage sensor and current sensor of the sensor unit 110 continuously sense current and voltage values of the PV module. This information is transmitted to the MPPT controller 132, the MPPT controller 132 tracks the maximum power point from the sensed current and voltage values, and the converter controller 140 determines the maximum power point tracked by the MPPT controller 132. The output of the N-Buck DC/DC converter 120 is controlled so that the corresponding voltage is output.

Here, when the detected value of the temperature sensor exceeds the reference value, the converter controller 140 may turn off the DC/DC converter 120 .

In the case of this embodiment, it corresponds to a configuration in which the maximum power point is directly searched from the real-time sensed voltage and current values.

Another embodiment of searching for a maximum power point using pre-stored DB information will be described.

To this end, the separate parameter DB unit (not shown) is included.

An optimal voltage value for outputting a maximum power point per current for each temperature is previously stored in the parameter DB unit. That is, the same contents as the graph of FIG. 4 are stored in the parameter DB unit.

In this case, the MPPT controller 132 extracts an optimal voltage value corresponding to the sensed values from the voltage sensor, current sensor, and temperature sensor from the parameter DB unit. Thereafter, the converter control unit 140 controls the extracted optimal voltage value to be output at the output terminal. For example, if the currently sensed temperature and current values are known, the corresponding current and voltage curves can be found, and the optimal voltage value for this curve (for example, the voltage value corresponding to point P corresponding to the maximum power point) ) can be extracted.

The operation of the photovoltaic system for compensating the output of the photovoltaic module in the shadow area according to another embodiment of the present invention will be described as follows. First, the voltage and current sensors sense current and voltage values of the PV module 10 . And, the temperature sensor senses the temperature value of the PV module 10 . Thereafter, the MPPT controller 132 extracts the optimal voltage value corresponding to the sensed values from the voltage and current sensors and the temperature sensor from the parameter DB unit. Next, the converter controller 140 controls the N-Buck DC/DC converter 140 to output the extracted optimal voltage value at the output terminal. Of course, when the detected value of the temperature sensor exceeds the reference value, the switch built into the N-Buck DC/DC converter 140 may be turned off.

Although preferred embodiments of the present invention have been described above, the present invention is not limited to the specific embodiments described above. That is, those skilled in the art to which the present invention pertains can make many changes and modifications to the present invention without departing from the spirit and scope of the appended claims, and all such appropriate changes and modifications Equivalents should also be considered as falling within the scope of this invention.

10. PV module 100. Output compensation device
110. Sensor unit 120. N-Buck DC / DC converter
130. Microcontroller 132. MPPT control unit
140. Converter control unit 150. Communication unit
200. Inverter 300. Monitoring device

Claims (3)

It relates to a device for compensating an output by being connected to each of a plurality of photovoltaic (PV) modules,
An N-Buck DC/DC converter that changes and outputs the DC power generated from the PV module to step-down or step-up;
a sensor unit for sensing the current and voltage supplied from the PV module to the N-Buck DC/DC converter and the temperature of the PV module;
The sensor unit continuously monitors the current and voltage supplied by the PV module and uses a Maximum Power Point Tracking (MPPT) algorithm to determine the maximum power point (MPP) of the PV module. a microcontroller to which an InC algorithm is applied; and,
a converter controller for controlling the N-Buck DC/DC converter to output a voltage corresponding to the maximum power point tracked by the MPPT controller; and,
A parameter DB in which an optimal voltage value for outputting a maximum power point per current for each temperature is stored;
The microcontroller determines that there is an abnormality when the temperature value sensed by the temperature sensor exceeds a set reference value, sends a control command to the converter control unit, and turns off the switch in the N-Buck DC/DC converter to turn off the internal Further comprising an abnormal state detection unit to block the operation of the circuit,
The output compensating device of a solar module, characterized in that the MPPT controller extracts an optimal voltage value corresponding to the sensed values from the current sensor, voltage sensor, and temperature sensor from the parameter DB unit.
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