KR101281079B1 - Photoelectric cell system with improved power quality and operating method of it - Google Patents

Abstract

PURPOSE: A solar cell generating system in which power quality is improved and an operating method thereof are provided to improve a power factor using current controlled voltage source inverter (CCVSI) only. CONSTITUTION: A photocell module transforms optical energy into electric energy. An inverter (160) transforms direct current (DC) voltage into alternating current (AC) voltage. A filter part delivers output of the inverter to an output terminal. A voltage source inverter (VSI) pulse controller (500) controls the operation of the inverter with pulse width modulation (PWM). A PWM driver (520) drives the inverter with a PWM method.

Description

Photoelectric Cell System with Improved Power Quality and Operating Method of it}

The present invention relates to a photovoltaic power generation system having a function of improving power quality in connection with a grid, and a method of operating the same.

In the past decades, the demand for renewable energy has increased significantly due to the shortcomings of fossil fuels and the greenhouse effect. Of the various types of renewable energy sources, solar and wind energy have become the most promising and attractive due to advances in power electronic technology. Photovoltaic (PV) power has been applied in various fields for the benefit of no maintenance and no pollution. In particular, the field of solar energy power has grown consistently over the last few years due to increased efficiency of solar cells, improved manufacturing technology and economies of scale. Increasingly, PV modules have been connected to and will be connected to utility systems in many countries. The world's largest PV power plant is now larger than 100 MW.

However, the output of the PV array depends on solar irradiation and weather conditions. More importantly, the high initial cost and limited lifetime of PV panels are required to extract as much power from them as possible. Therefore, a maximum power point tracking (MPPT) technique must be implemented to achieve maximum efficiency of the PV array in the DC / DC converter. Several algorithms have been developed to achieve MPPT technology.

Due to the capacity of the PV system to grow significantly, the influence of PV modules on the power grid cannot be ignored. They cause problems with the system, such as flickering and increasing harmonics, and worsen the stability of the power system. Both the capacity increase of PV arrays and the maintenance of power quality are necessary to comply with the technical requirements for PV systems such as function and harmonic current regulation. Especially when large PV modules are connected to the grid, there is a possibility that the effects on the grid will certainly be severe. Therefore, when PV modules are connected to the power grid, the requirements for system operation and system stability under fault conditions will be strengthened.

The increasing use of electrostatic source converters, such as rectifiers and switched mode power supplies, causes the injection of harmonic currents into the distributed system. Current harmonics cause voltage distortion, current distortion and unstable operation of the power system. Harmonic mitigation measures therefore play an important role in grid-connected PV systems. In addition to the active power supply, the PV inverter can be controlled to provide the harmonic current required by the nonlinear load, allowing the current on the grid side to be close to the sine wave.

In general, a grid-connected photovoltaic power generation system is composed of a solar cell, an MPPT converter, and an inverter for supplying power generated from the solar cell to the grid. The existing system simply supplies the electricity generated from the solar power to the system by the MPPT control of the converter (or inverter) and can be used only in the daytime with insolation, so that the utilization rate (5-6 hours / day) is high compared to the high installation cost. In addition to the very low power, when applied to non-linear and power factor loads such as homes and office buildings, the power factor of the system is rather deteriorated due to the active power support by solar power generation.

In general, when a power factor occurs in a system, the supply power requirement of the system increases because the same active power demand must be supplied considering reactive power. It is not a big problem for the system because of the small size of the currently installed system, but as mentioned above, in view of the fact that the prevalence is greatly expanded, there may be a problem due to the grid connection. In addition, the proliferation of non-linear loads, such as computers and modern electronic devices, leads to problems such as power quality of the system, such as increased harmonics and reduced power factor, as well as malfunction of electrical equipment and increased rated capacity of the power converter.

1. Prior Document 1: Korean Patent Publication No. 2006-0084068 (2006.07.24) 2. Prior Document 2: Republic of Korea Publication No. 2009-0015391 (2009.02.12)

The present invention is to provide a photovoltaic power generation system that provides an effective function as a system even in a non-power generation period such as night.

More specifically, the photovoltaic power generation system is composed of a solar cell that generates power by using sunlight as an energy source and a current controlled voltage source inverter (CCVSI) that supplies the generated power to the grid, and operates in day mode and night mode. In night mode, it performs reactive power compensation functions such as harmonic reduction and power factor improvement of the system.In daylight mode with solar radiation, the solar power generation system which performs MPPT control and reactive power compensation function simultaneously to obtain maximum output from solar cells To provide.

Photovoltaic power generation system according to an aspect of the present invention, a photovoltaic module for converting light energy into electrical energy; An inverter for converting a DC voltage input from the photovoltaic module into an AC voltage; A filter unit for transmitting the output of the inverter to an output terminal by removing a noise component; And a VSI pulse controller configured to PWM control the operation of the inverter by applying a p-q theory.

Here, the VSI pulse controller may perform a reactive power compensation function of harmonic reduction and power factor improvement of a system in a non-power generation period, and may perform a control to perform a reactive power compensation function of a power generation power during a power generation period.

Here, the VSI pulse controller may turn off the switching elements of the inverter while the output terminal is connected to the grid in the non-power generation period of the photovoltaic module.

The VSI pulse controller may include: a PWM driver for driving the inverter in a PWM manner; A p-q signal generating module generating a p signal and a q signal from the electrical signal detected at the three-phase output terminal; And a reference current generator configured to generate two reference current signals Iref_alpha and Iref_beta for the PWM driver from the p signal and the q signal.

Here, the p-q signal generation module, α β voltage signal generation unit for generating an alpha voltage signal and a beta voltage signal from the voltage of each line of the three-phase output terminal; An αβ current signal generator for generating an alpha current signal and a beta current signal from currents in each line of the three-phase output terminal; And a p-q signal generator configured to generate a p signal and a q signal from the alpha voltage signal, the beta voltage signal, the alpha current signal, and the beta current signal.

The apparatus may further include a boost converter for boosting the voltage produced by the photovoltaic module and transferring the voltage to the inverter.

Here, the filter unit may include a reactor for limiting a current at the output terminal and a capacitor for blocking high frequency components.

According to another aspect of the present invention, there is provided a method of operating a solar power generation system, the method comprising: converting light energy into electrical energy in a photovoltaic module; Converting a DC voltage into an AC voltage in an inverter input from the photovoltaic module; Transmitting an output of the inverter to an output stage by removing a noise component from a filter unit; PWM control the operation of the inverter by applying the p-q theory,

During the non-power generation period, blocking the photovoltaic module; Performing a reactive power compensation function of the connected grid power may be performed.

Here, in the blocking of the photovoltaic module, the switching elements of the inverter may be turned off.

The PWM control may include generating an alpha voltage signal and a beta voltage signal from voltages of each line of the three phase output terminal, and generating an alpha current signal and a beta current signal from currents of each line of the three phase output terminal. ; Generating p and q signals from the alpha voltage signal, beta voltage signal, alpha current signal and beta current signal; Generating two reference current signals from the alpha voltage signal and the beta voltage signal and the p signal and the q signal; And PWM controlling the inverter with the two reference current signals.

The blocking of the photovoltaic module may be performed using the inverter, and the performing of the reactive power compensation function of the connected grid power may be performed using the filter unit.

When implementing the solar power generation system of the present invention according to the above configuration, there is an advantage to provide an effective function as a system even in a non-power generation period such as night.

For example, the proposed system can improve the power quality of the system by using only one CCVSI, which can receive power in both directions, as well as the maximum power production of photovoltaic power generation as well as power factor improvement and harmonic reduction. This can maximize the utilization rate (24 / day) compared to the existing system that operates only during the day, and can perform maximum solar power generation, reactive power compensation, and power quality improvement simultaneously without additional equipment, thereby improving efficiency and miniaturization. Can be achieved.

1 is a block diagram showing a solar power system according to an embodiment of the present invention.
FIG. 2 is a detailed block diagram illustrating an associated portion of a boost converter, an inverter, and a filter unit in the solar power generation system of FIG. 1.
3 is a detailed block diagram of a PWM driver provided in the VSI pulse controller of the solar power generation system of FIG.
4 is a graph showing I / V and P / V characteristics of PV module output, respectively.
5 is a flow diagram illustrating a method in accordance with an incremental conductance algorithm.
6 is a detailed block diagram illustrating the boost converter and MPPT control circuit portion of FIG.
FIG. 7 is a detailed block diagram of a pq signal generation module provided in the VSI pulse controller of FIG. 1. FIG.
FIG. 8 is a detailed block diagram of a reference current generator provided in the VSI pulse controller of FIG. 1. FIG.
9 is a block diagram illustrating the solar power generation system of FIG. 1 connected to various grid loads.
10 is a circuit diagram when a nonlinear load is connected to the grid power supply so that reactive power is not compensated for.
Fig. 11 is a graph showing waveforms of grid current and nonlinear load current.
12 is a graph showing the power factor of the system and the load.
13 is a graph showing _a grid current I _sa , a nonlinear load current I _La , and an inverter current I _a with harmonic compensation.
Fig. 14 is a graph showing power factor change of system current I _sa , nonlinear load current I _La , and inverter current I _a with harmonic compensation;
15A and 15B are flowcharts illustrating a method of operating a photovoltaic power generation system according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Photovoltaic power generation system according to an embodiment of the present invention shown in Figure 1, a photovoltaic module 110 for converting light energy into electrical energy; An inverter (160) for converting a DC voltage input from the photovoltaic module into an AC voltage; A filter unit for transmitting the output of the inverter 160 to an output terminal by removing a noise component; And a VSI pulse controller 500 for PWM controlling the operation of the inverter by applying a p-q theory.

In addition, the photovoltaic power generation system may further include a booster converter 120 for boosting the voltage produced by the photovoltaic module and transferring the voltage to the inverter.

The VSI pulse control unit 500 may perform reactive power compensation for reducing harmonics and improving power factor of the system during non-power generation periods such as nighttime or bad weather, and performing reactive power compensation of generation power during the daytime generation period. Can be. To this end, in the above-described photovoltaic power generation system of the present embodiment, only a component capable of compensating for reactive power can be connected to the grid in a non-power generation period, and the photovoltaic module can be disconnected from the grid. As the component that performs the function of compensating the reactive power, the filter unit having a relatively large amount of inductor or capacitor component is representative.

Although separate switch elements may be provided for grid connection of the filter unit and grid shutdown of the photovoltaic module during the non-power generation period, a switch element belonging to the inverter (inverter generally includes a switch element for converting direct current into alternating current). It has the advantage of cost reduction.

In this case, the VSI pulse controller 500 turns off all switching elements (switching transistors) for DC-AC conversion of the inverter 160 in the non-power generation period of the photovoltaic module with the output terminal connected to the grid. Can be controlled.

The photovoltaic power generation system (PV system) shown in FIG. 1 is in a state of being connected to a distributed network, and the figure illustrates a schematic diagram of disconnection of the system.

In the case of grid-connected PV systems, the photovoltaic (PV) array 110 is connected to the grid via a power electronic inverter that converts DC power to AC power. Many other topologies have been developed and used over the last few decades. Dual-string topologies are the most common type of PV installation in the past.

Some strings connect voltage boost with their own DC / DC converters and are connected to the DC bus. At that time, a common DC / AC inverter is used for integration with the utility. The advantage of this topology is the fact that it has independent control of the power supply, better protection, safer during installation and maintenance, lower cost and so on.

Maximum power point tracking (MPPT) technology is implemented in the DC / DC converter to achieve maximum efficiency of the PV modules. DC / DC converter topology commonly used by boost and chuck converters. However, boost converters offer advantages over chuck converters because of blocking diodes that can prevent reverse currents in PV arrays. Incremental conductance (IncCond) method is used for boost converter control.

The output of boost converter 120 is connected to central inverter 160 via a DC transmission line. DC transmission lines are considered to be short circuits at the same distance from both boost converters. Multi-string PV arrays are connected together at certain points. The DC common bus is then connected to the dc end of the dc connection capacitor C and the dc side of a three phase voltage source inverter (VSI). The DC-connected capacitor tries to regulate the voltage on the DC side of the inverter. And the capacity depends on the ripple requirement of the capacitor. Based on the sinusoidal-triangle modulation strategy, the VSC is controlled. The connection resistor connects a point of common coupling (PCC) to the distributed end of the VSC's AC side. The connection resistor includes the resistance of the IGBT. Filter capacitor C _f provides a low impedance path to the current harmonics produced by the inverter.

A distributed network is just an example of simplifying a real distributed network. The distribution network comprises a transformer T _r1 , a load, two distribution lines and a capacitor C ₁ . T _r1 steps the network voltage down to an appropriate level for the PV system. The high voltage side of T _{r1 has} a Y-shaped connection and is firmly grounded. In addition, three-phase loads are connected by lines at locations between the PCC and the system. The inductor and resistance of the distributed line between the PCC and the load are represented by L ₁ and R ₁ , respectively. Similarly, R ₂ and L ₂ represent the inductor and resistance of the line between the load and the grid, respectively. Capacitor C ₁ is used to improve the load power factor and always provide it to the load.

An overview of a multi-string grid-connected photovoltaic (PV) system with the function of harmonic compensation is illustrated in FIG. 2. However, transformers are not represented in hardware configurations because of the fact that large transformers are not needed at low voltage levels. However, a variable transformer is needed to bring down the voltage to the commercial voltage. Moreover, the transmission line is not taken into account because the resistor and inductor are included in both the LC filter and the connecting line in this machine. Since the PV array is not available in the laboratory, a controllable DC power source is used instead to mimic the characteristics of the PV array. In parallel with the three-phase R load, the three-phase diode rectifier is connected with a nonlinear load.

FIG. 2 illustrates in detail the associated part of the boost converter, the inverter, and the filter unit in the solar power generation system of FIG. 1. The filter unit may include a reactor L1 for limiting a current at the output terminal and an output capacitor C0 for removing high frequency noise. In addition, according to a viewpoint, the capacitor C1 connected to the input terminal of the inverter 160 of FIG. 1 may also be defined to be included as a filter in its function.

3 illustrates a detailed structure of the PWM driver 520 included in the VSI pulse controller of the solar power generation system of FIG. 1. The illustrated PWM driver operates as a sinusoidal- triangle wave modulation control block that receives two reference current signals Iref_alpha and Iref_beta. The switching operation of the switching transistors of the inverter 160 of FIG. 2 may be controlled in a PWM manner by signals output from the PWM driver 520 of FIG. 3.

Next, we will look at the maximum power point tracking and PLL control algorithm of the photovoltaic power generation system.

Performance and reliability are of paramount importance in PV systems with significant power devices and voltage levels. Therefore, proper modeling and control design allows the progress of hardware execution. The entire PV system can be divided into several subsystems to facilitate control individually. First, in a multi-string grid-connected photovoltaic (PV) system, an equivalent circuit is made to represent the PV array.

Maximum power point tracking (MPPT) control is implemented to ensure high efficiency of distributed generation in the boost converter. MPPT algorithm and block model are discussed. Three-phase inverters convert DC power to distributed networks and harmonic AC power. Inverter current control is so critical because it determines how well harmonics are compensated. This section deals with voltage power inverter (VSI) control.

VSI pulse width modulation and control is synchronized to the distributed network voltage using the pq theory. The three-phase AC voltages and currents are then converted into αβ components that make design and control easier. This component is used to find the active power and reactive power after passing through the filter portion as a high pass filter.

Next, we will look at the control method using the maximum power point tracking, and in particular, the incremental conductance algorithm. PV arrays exhibit nonlinear characteristics. 4 shows the I / V and P / V characteristics of the PV module output, respectively. The power conversion ratio of PV panels is not so high yet. Therefore, it is important to extract as much power as possible from PV panels.

Many kinds of MPPT algorithms have been developed and put into application. The most widespread is the incremental conductance method (IncCond) of constant voltage tracking (CVT), perturbation and observation method (P & O). The dual incremental conductance method has advantages over others, such as high tracking accuracy and no vibration around the MPP. A flowchart of the method according to the incremental conductance algorithm is shown in FIG. 5.

As can be seen in the flowchart shown, the MPP can be tracked by comparing the instantaneous conductance (I / V) with the incremental conductance (ΔI / ΔV). V _ref is the reference voltage and is equal to V _MPP in _MPP . Once the MPP is reached, the operation of the PV array is maintained at that point unless there is a change in ΔI indicating a change in solar irradiation or weather conditions. The algorithm decreases or increases V _ref to track the new MPP.

6 is a schematic diagram of a boost converter MPPT control circuit, and the MPPT execution process will be described with reference to this drawing.

The control algorithm is executed in the boost converter to provide the DC voltage to the voltage source inverter. The boost converter topology has advantages over buck converters for MPPT applications for the following reasons. First, the effective current through the inductor is less than that of a buck converter. For power IGBT and driver selection, the current rating is lower in the boost converter than in the buck converter. The capacity of a solar power system depends on light. At night, current can flow back into the photovoltaic cell from the grid, where leakage losses can cause massive damage. Reverse current blocking diodes are effective to prevent reverse currents in the boost converter, and diodes help to avoid reverse currents with reverse current blocking diodes. Compared to natural frequencies that do not attenuate, boost transducers exhibit better dynamics than buck transducers. In general, it offers advantages in terms of wider bandwidth and smaller resonance because of the small input capacitance of the boost converter.

Next, the p-q theory which is one of the main features of the present invention will be described.

The VSI pulse controller 500 of FIG. 1 includes a PWM driver 520 for driving the inverter in a PWM manner; A pq signal generation module (530, 540, 550) for generating a p signal and a q signal from the electrical signal detected at the three-phase output terminal; And a reference current generator 570 for generating two reference current signals Iref_alpha and Iref_beta for the PWM driver from the p signal and the q signal.

The p-q theory uses the controller design involved in this work without neutral lines. The p-q theory consists of the algebraic transformation (Clarke transformation) of the three-phase voltage and current on the axis to the α-β axis. The equation for the current in the α-β axis is as shown in Equation 1 below.

The equation for the voltage on the α-β axis is shown in Equation 2 below.

The equations for p and q are shown in Equation 3 below.

Equation 4 is used to generate a reference current for the controller.

The present invention provides a control means based on the p-q theory described above. The instantaneous values of active power and reactive power at the first stage of the control means are calculated in FIG. 7. In addition, as a second step of the control means, an error current signal for switching a valid inverter is used in FIG. In FIG. 7, Van, Vbn, and Vcn denote sensing values of the three-phase current sensors 311, 312, and 313 of FIG. 1 and a potential sensor 315 for sensing a potential between any two of the three-phase output lines. Can be obtained by calculating the value.

Here, the pq signal generation modules 530, 540, and 550 illustrated in FIG. 7 may perform alpha voltage signals according to the above-described process according to Equation 2 from voltages Van, Vbn, and Vcn of each line of the three-phase output terminal. An αβ voltage signal generator 530 for generating a Valpha and a beta voltage signal Vbeta; Αβ current signal generator for generating an alpha current signal Ialpha and a beta current signal Ibeta from the currents Ia, Ib and Ic of each line of the three-phase output terminal according to the above-described process of Equation 1 above 540; And a pq signal generation unit generating a p signal and a q signal from the alpha voltage signal Valpha and the beta voltage signal Vbeta, the alpha current signal Ialpha, and the beta current signal Ibeta according to Equation 3 described above. 550).

Meanwhile, the reference current generator 570 shown in FIG. 8 includes two reference current signals according to Equation 4 described above from the alpha voltage signal Valpha, the beta voltage signal Vbeta, the p signal, and the q signal. (Iref_alpha, Iref_beta) are generated and supplied to the PWM driver 520.

Next, a process of compensating harmonics of the photovoltaic power generation system having the above-described configuration will be described.

FIG. 9 illustrates the solar power generation system of FIG. 1 in various grid load connections. The PV system in the illustrated state not only supplies active power to the power system but can also compensate for harmonics generated by nonlinear loads.

The grid voltage is assumed to be balanced and simulated with the ideal voltage source. Solar arrays and systems are powering diode rectifiers in parallel with resistive loads. There are many harmonics in the load current, and the inverter is controlled to provide harmonic compensation.

10 is a circuit when a nonlinear load is connected to the grid power supply so that reactive power is not compensated for.

In this case, Fig. 11 is a graph showing waveforms of the grid current and the nonlinear load current, and Fig. 12 is a graph showing the power factor of the grid and the load. It can be seen in FIG. 12 that the current on the inverter side is full of harmonics compared to it before compensating. However, the current on the grid side is close to the sinusoid after compensating with the inverter current.

FIG. 13 shows a grid current I _sa , a nonlinear load current I _La , and an inverter current I _a with harmonic compensation, and FIG. 14 shows a grid current I _{sa with a} harmonic compensation, a nonlinear load current ( I _La ) and the power factor change of the inverter current I _a are shown. In FIG. 13, it can be seen from FIG. 14 that the reactive power component generated by the non-sinusoidal load current compensates for the reactive power by the inverter current, thereby attenuating the lower harmonic components of the grid current, thereby increasing the power factor from 0.946 to 0.961.

As described above, the operation method of the photovoltaic power generation system of the present embodiment performing harmonic compensation of the system in the non-power generation period according to the spirit of the present invention is as shown in FIGS. 15A and 15B.

The operation method of the photovoltaic power generation system of this embodiment shown in Figure 15a, in the power generation period, the step of converting light energy into electrical energy in the photovoltaic module (S220); Converting DC power into AC power in the inverter input from the photovoltaic module (S240); Transmitting an output of the inverter to an output terminal by removing a noise component from a filter unit (S260); And PWM control the operation of the inverter by applying the p-q theory (S280).

In a non-power generation period, blocking the photovoltaic module (S310); And performing a reactive power compensation function of grid power to the filter unit (S350).

Referring to the step (S280) of PWM control the operation of the inverter in detail by applying the pq theory in Figure 15b, by applying the equation (2) from the voltage of each line of the three-phase output terminal and the alpha voltage signal (Valpha) and Generating a beta voltage signal (Vbeta) and generating an alpha current signal (Ialpha) and a beta current signal (Ibeta) by applying Equation 1 from the currents of each line of the three-phase output terminal (S282); Generating a p signal and a q signal by applying Equation 3 from the alpha voltage signal Valpha, the beta voltage signal Vbeta, the alpha current signal Ialpha, and the beta current signal Ibeta (S284); Generating two reference current signals Iref_alpha and Iref_beta by applying Equation 4 from the alpha voltage signal Valpha and the beta voltage signal Vbeta, the p signal, and the q signal (S286); And PWM controlling the inverter with the two reference current signals Iref_alpha and Iref_beta (S288).

In the illustrated process, the steps S240, S310, and S390 may be performed using the inverter 160 (more specifically, a switching transistor belonging to the inverter) of FIG. 1, which is the same component, or the steps S260 and Step S350 may be performed using the filter unit of the system of FIG. 1, which is the same component.

That is, in an implementation of preventing cost increase due to additional switching elements for shutting down the grid, in the step of blocking the photovoltaic module (S310), the switching elements (switching transistors) of the inverter may be turned off.

It should be noted that the above-described embodiments are intended to be illustrative, not limiting. In addition, those skilled in the art will understand that various embodiments are possible within the scope of the technical idea of the present invention.

110: photovoltaic module 120: booster converter
160: inverter 500: VSI pulse control unit
520: PWM driver 530: αβ voltage signal generator
540: αβ current signal generator 550: pq signal generator
570: reference current generating unit

Claims (7)

A photovoltaic module for converting light energy into electrical energy;
An inverter for converting a DC voltage input from the photovoltaic module into an AC voltage;
A filter unit for transmitting the output of the inverter to an output terminal by removing a noise component; And
It includes a VSI pulse control unit for PWM control the operation of the inverter by applying the pq theory,
The VSI pulse control unit,
A PWM driver for driving the inverter in a PWM manner;
A pq signal generation module generating a p signal and a q signal from the electrical signal detected at the output terminal; And
Including a reference current generating unit for generating two reference current signals (Iref_alpha, Iref_beta) for the PWM driver from the p signal and q signal,
In the non-power generation period, the system performs reactive power compensation function to reduce harmonics and power factor improvement of the system.
The pq signal generation module,
An αβ voltage signal generator for generating an alpha voltage signal and a beta voltage signal from voltages of each line of the output terminal;
An αβ current signal generator for generating an alpha current signal and a beta current signal from currents in each line of the output terminal; And
A pq signal generator configured to generate a p signal and a q signal from the alpha voltage signal, the beta voltage signal, the alpha current signal, and the beta current signal,
The VSI pulse control unit,
In the non-power generation period of the photovoltaic module, with the output terminal connected to the grid, switching off the switching elements of the inverter,
The reference current signal is generated by the following formula (1).
[Equation 1]

Where i _αref and i _βref are reference current signals,
v _α , v _β is the voltage on the α-β axis,
i _α , i _β are the currents on the α-β axis.
delete delete The method of claim 1,
Boost converter for boosting the voltage produced by the photovoltaic module to the inverter
Photovoltaic power generation system further comprising.
The method of claim 1,
The filter unit includes:
A photovoltaic power generation system comprising a reactor for limiting current at an output stage and a capacitor for blocking high frequency components.
In the developing period,
Converting light energy into electrical energy in the photovoltaic module;
Converting a DC voltage into an AC voltage in an inverter input from the photovoltaic module;
Transmitting an output of the inverter to an output stage by removing a noise component from a filter unit;
PWM control the operation of the inverter by applying the pq theory
Lt; / RTI >
In the non-development period,
Turning off the switching elements of the inverter and shutting off the photovoltaic module;
Perform reactive power compensation of the connected grid power,
The PWM control step,
Generating an alpha voltage signal and a beta voltage signal from voltages of each line of the output stage, and generating an alpha current signal and a beta current signal from the currents of each line of the output stage;
Generating p and q signals from the alpha voltage signal, beta voltage signal, alpha current signal and beta current signal;
Generating two reference current signals from the alpha voltage signal and the beta voltage signal and the p signal and the q signal; And
PWM controlling the inverter with the two reference current signals,
Blocking the photovoltaic module is performed using the inverter,
Performing a reactive power compensation function of the connected grid power is performed using the filter unit,
The reference current signal is generated by the following [Equation 2] operating method of a solar power system.
[Equation 2]

Where i _αref and i _βref are reference current signals,
v _α , v _β is the voltage on the α-β axis,
i _α , i _β are the currents on the α-β axis. delete

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