KR101112650B1 - method for parallel operating control of photovoltaic module - Google Patents

Abstract

A parallel operation control method of a photovoltaic module is disclosed to allow generation of supercapacity by parallelization of a photovoltaic power conditioning system (PCS) module and to allow a consumer to freely manufacture a desired capacity. The parallel operation control method of the photovoltaic module according to the present invention has no signal lines required between the PCS modules, so there is no problem due to sensing noise or interference, and since the PCS module has a completely independent control structure, the parallel between the PCS modules Easy connection makes it easy to expand the capacity of the PV system and reduce the circuit size. In addition, by controlling the number of operating modules according to the amount of sunshine, module efficiency can be maximized. When one module stops operating, the remaining modules share power and continue to operate.

Description

Method for parallel operation control of photovoltaic module

The present invention relates to a parallel operation control method of a solar module, in particular, the parallel of the solar power control system (PCS) module is possible to generate a large capacity and parallel to the solar module to enable the consumer to freely produce the desired capacity It relates to a driving control method.

In general, photovoltaic power generation may contribute to the reduction of foreign currency due to energy self-sufficiency and energy imports by actively utilizing abundant light energy sources without using fossil energy such as petroleum, coal, and natural gas. It is currently in the spotlight as an alternative energy source for petroleum under the World Climate Change Convention, which strictly limits the amount of carbon dioxide generated by fossil energy.

Among the solar power generation systems, the system-linked solar power generation system is used as a distributed power system for residential or other systems, so it has the highest potential for practical use and dissemination, and is an environment-friendly clean energy source. Prevent problems and respond to regulations under climate change agreements.

The development of the source technology of the grid-connected solar inverter and the digitalization of the system enable the high efficiency, reliability, miniaturization, and light weight of the power generation system, thereby improving the safety and reliability for reducing the production cost and practical use of the power generation system. It can raise costs and contribute to cost reduction. In addition, it is possible to effectively utilize and distribute energy through the efficiency of the existing power system operation.

However, when a single solar module is used for photovoltaic power generation, large-capacity photovoltaic power generation is difficult, and it is difficult to produce a desired capacity for a consumer. Therefore, the necessity of a parallel operation method in which the solar modules are connected and operated in parallel has emerged.

In other words, the parallelization of solar modules enables the generation of super-capacity, the capacity desired by consumers can be freely produced, the cost of products can be reduced by mass production of solar module products, and the quality control and troubleshooting of products can be facilitated. have.

The parallel operation control method of the solar module according to the present invention to meet such a need there is no signal line required between the solar PCS module, there is no problem due to sensing noise or mutual interference, the solar PCS module The complete independent control structure allows easy parallel connection between photovoltaic PCS modules, making it easy to expand the capacity of photovoltaic power generation systems and reduce circuits.

By controlling the number of operating modules according to the amount of sunshine, the module efficiency can be maximized, and even if one module stops operating due to failure, the remaining modules can share the power and continue to operate, enabling stable operation and efficient operation module management. This can extend the life of the inverter.

In the parallel operation control method of the solar PCS module,

While sharing the inverter input voltage ( Vdc ) of a plurality of solar PCS modules connected in parallel, one master module and N-1 slave module by comparing the inverter input voltage ( Vdc ) and the inverter input voltage reference value ( Vdc_ref) Determination step of distinguishing;

 After the determination step, the master module performs an MPPT algorithm for operating at the maximum power point at which the maximum power is input from the solar cell, and controls the output current of the inverter to match the inverter input voltage reference value with the inverter input voltage. A master module control step of generating a command value and generating an inverter voltage command value to PWM control the inverter to perform a current control to match the generated inverter current command value with the output current of the inverter; And,

After the determination step, the slave module predicts the module input DC current, calculates the module input DC current reference value from the predicted module input DC current, and applies the application to match the calculated input DC current reference value of the module with the actual input DC current. While performing the converter current control to adjust the rate, it generates an inverter current command value for controlling the output current of the inverter to match the inverter input voltage reference value and the inverter input voltage, and matches the generated inverter current command value with the output current of the inverter. And a slave module control step of generating an inverter voltage command value to perform current control and PWM controlling the inverter.

The parallel operation control method of the photovoltaic module according to the present invention has no signal lines necessary between the PCS modules, so there is no problem due to sensing noise or interference, and since the PCS modules have a completely independent control structure, the parallel between the PCS modules Easy connection makes it easy to expand the capacity of the PV system and reduce the circuit size.

In addition, by controlling the number of operating modules according to the amount of sunshine, module efficiency can be maximized. When one module stops operating, the remaining modules share power and continue to operate.

1 is a configuration diagram of a system for performing parallel operation of a solar PCS module according to the present invention. As shown in FIG. 1, DC-DC converters 110a to 110n are outputted to the output side of DC-DC converters 110a to 110n which receive and convert DC power voltages PV + and PV- from a solar cell (not shown). The three-phase inverters 120a to 120n for changing the output current of the three-phase current share the input and output terminals, respectively, so that the N solar PCS modules 130 are connected to each other in parallel.

The photovoltaic PCS module 130 transmits power corresponding to 1 / N to the power generated from the photovoltaic cell to the grid. And DC + and DC - terminals of each module's DC link are connected to each other and share Vdc . Comparing the shared Vdc with the reference value Vdc_ref , it is divided into 1 master and N-1 slaves, and the master and the slave perform different algorithms.

In the parallel operation control method of the solar module according to the present invention, as shown in Figure 2, the start time is defined so that each module operates sequentially, the algorithm is started as one module starts. The next module is started sequentially and the starting module performs different algorithms by separating the master and the slave.

Here, when the start of each module in parallel, the condition to distinguish the master and slave is compared to the input voltage Vdc input to the three-phase inverter and the reference value Vdc_ref, input voltage Vdc is the difference between the input voltage reference value Vdc_ref 1 ~ If it has a value of 19V range, it is determined to be the same range value and becomes a slave. If the input voltage Vdc has a value greater than or equal to 20V from the input voltage reference value Vdc_ref , it becomes a master.
In other words, the input voltage reference value V _{dc_ref} ranges from 620V to 640V, 620V without output power, and 640V at 100% power. At initial startup, the input voltage V _dc is Has a voltage of less than _600V, the output power is not and V _{dc_ref} Since the difference of V _dc exceeds 1 ~ 19V, it operates as a master. In the presence of master module, the voltage of V _dc is from 620V to 640V due to inverter voltage control, and V _{dc_ref} has no output power. Since it is 620V, input voltage reference value V _{dc_ref} and input voltage The difference between V _dc is within 20V.

The module determined to be a master performs the maximum power point traking (MPPT) algorithm that follows the maximum power from the photovoltaic cell to operate at the maximum power point. Inverter input voltage reference value Vdc_ref for controlling the output current compared to the input voltage ( Vdc ) of the three-phase inverter is as shown in <Equation 1>.

Vdc _ ref = Vref + kPo Equation 1

In Equation 1, Vref is an inverter input voltage reference value when there is no output power, k is a proportional constant, and Po is an output power of the module inverter.

The input voltage and output current control algorithm of the inverter is executed by comparing the input voltage Vdc of the three-phase inverter with the inverter input voltage reference value Vdc_ref . The inverter's input voltage control algorithm generates an inverter current command that controls the inverter's output current to match Vdc_ref and Vdc .

The inverter output control algorithm generates an inverter voltage command value to perform a current control that matches the inverter current command value generated through the inverter input control algorithm with the output current of the inverter.

 The inverter is controlled by pulse width modulation (PWM) by the inverter voltage command value generated through the inverter output control algorithm.

The module determined to be a slave performs an input DC current prediction algorithm. The module input current prediction is derived from Equation 2 below to control the output of the inverter by predicting the module input DC current I _PV .

식 2

Equation 2

는 전력효율이고, Po는 모듈의 출력전력,

는 태양광 셀의 전압이다. 식 2에서의 모듈의 입력 직류전류는 모듈의 인버터 출력 전력에 해당되고, 모듈의 입력 직류전류I_PV 로부터 모듈 입력 직류전류 기준값 I_{PV_ref} 는 다음과 같은 식 3으로 나타낼 수 있다.In equation 2

Is the power efficiency, Po is the output power of the module,

Is the voltage of the solar cell. The input DC current of the module in Equation 2 corresponds to the inverter output power of the module, and the module input DC current reference value I _{PV_ref} from the input DC current I _PV of the module can be expressed by Equation 3 as follows.

식 3

Equation 3

The module determined to be a slave performs a converter current control algorithm to control the current flowing through the module. The converter current control is performed to adjust the duty ratio in order to match the module input DC current reference value I _{PV_ref} with the actual module input DC current I _PV . Obtaining the inverter input voltage reference value ( Vdc_ref ), the method of controlling the input voltage ( Vdc ) and output current of the inverter, PWM signal generation is performed in the same way as the master module.

3 is an output voltage and output current waveform according to the proposed parallel operation control method. The solar cell generates about 7.8 kW, Vpv is about 390 V, and the power factor is about 99.7%. At this time, the estimated current is about 20A, and when two PCS modules are operated in parallel, the current flowing through each module is about 10A. 3, it can be seen that about 10 A flows in the module 1 and the module 2, at which time about 3.9 kW is delivered to the grid. As such, the output currents generated in the module 1 and the module 2 are generated almost evenly.

The parallel operation control method of the solar module according to the present invention by sharing the inverter input voltage ( Vdc ) to distinguish one master module and N-1 slave module by comparing with the reference voltage of the inverter input voltage, the master module The inverter input voltage reference value Vdc_ref is determined while performing a maximum power point traking (MPPT) algorithm for operating at a maximum power point at which maximum power is input from a photovoltaic cell.

An inverter voltage command value is generated through current control that matches the inverter output current reference value with the inverter current, thereby controlling the inverter with a pulse width modu-lation (PWM) signal.

The slave module predicts the module's input direct current, and from this predicted value, the duty ratio resulting from performing the converter current controller to match the new module input direct current reference value I _{PV -ref} with the actual module input direct current I _PV . To adjust the converter current. Obtaining the inverter input voltage reference value ( Vdc_ref ), the method of controlling the input voltage ( Vdc ) and output current of the inverter, PWM signal generation is performed in the same way as the master module.

Therefore, the parallel operation control method of the photovoltaic module according to the present invention has no signal line between the PCS modules, so there is no problem due to sensing noise or interference, and the PCS module has a completely independent control structure. The parallel connection between them makes it easy to expand the capacity of the photovoltaic system and reduce the circuit size.
In addition, by controlling the number of operating modules according to the amount of sunshine, module efficiency can be maximized. When one module stops operating, the remaining modules share power and continue to operate.
Although the preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, the present invention is not limited thereto and may be improved or modified by those skilled in the art within the scope of the technical idea of the present invention.

delete

delete

1 is a parallel configuration diagram of a solar PCS module according to the present invention.

2 is a flowchart of a parallel operation control method of a solar PCS module according to the present invention.

3 is a waveform diagram showing an output voltage and an output current according to the parallel operation control method according to the present invention.

Claims (4)

In the parallel operation control method of the solar PCS module, While sharing the inverter input voltage ( Vdc ) of a plurality of solar PCS modules connected in parallel, one master module and N-1 slave module by comparing the inverter input voltage ( Vdc ) and the inverter input voltage reference value ( Vdc_ref) Determination step of distinguishing; After the determination step master module MPPT algorithm, determining the inverter input voltage reference value (Vdc_ref), and the inverter input voltage reference value (Vdc_ref) and the inverter input while performing that from the solar cells to operate at the maximum power point is the maximum power input Inverter current command value is controlled to control the output current of the inverter to match the voltage ( Vdc ), PWM control of the inverter by generating the inverter voltage command value to perform the current control to match the generated inverter current command value to the output current of the inverter. A master module control step; And, After the determination step, the slave module predicts the module input DC current, calculates the module input DC current reference value from the predicted module input DC current, and applies the application to match the calculated input DC current reference value of the module with the actual input DC current. While performing the converter current control to adjust the rate, the inverter input voltage reference value ( Vdc_ref) is determined, and the inverter current command value for controlling the output current of the inverter to match the inverter input voltage reference value and the inverter input voltage ( Vdc ) is generated. And a slave module control step of PWM controlling the inverter by generating an inverter voltage command value so as to perform a current control to match the generated inverter current command value with the output current of the inverter. The method of claim 1, wherein the determining step is the one solar module is activated, and subsequently when connected in parallel, and then start-up the photovoltaic module, the input voltage Vdc to the input voltage reference value input to the three-phase inverter of each module Vdc_ref In comparison, _if the difference between the input voltage V _dc and the input voltage reference value V _{dc_ref has} a value within the range of 1 to 19 V , it is determined as a slave, and the difference between the input voltage V _dc and the input voltage reference value V _{dc_ref} includes 20 V. Parallel operation control method for a photovoltaic module, characterized in that it has a value greater than that determined by the master. The method of claim 1, wherein the inverter input voltage reference value Vdc_ref for controlling the output current compared to the input voltage Vdc of the inverter is derived by the following Equation 1. Vdc_ref = Vref + kPo Equation 1 In Equation 1, Vref is the inverter input voltage reference value when there is no output power, k is the proportional constant, and Po is the output power of the module inverter. The method of claim 1, wherein the module input DC current I _PV for controlling the output of the inverter in the slave module control step is predicted by the following equation 2,

Equation 2 The module input DC current reference value I _{PV_ref} for performing converter current control to adjust the rate of fertilization is derived by Equation 3 below.

Equation 3 In Equation 2 and Equation 3 above

Is the power efficiency, Po is the output power of the module,

Is the voltage of the solar cell.

Images