Photovoltaic inverter control device with backflow preventing function and control method thereof

Abstract

The invention relates to a photovoltaic inverter control device with the backflow preventing function to enable a three-phase inverter to achieve the backflow preventing function and further relates to a control method of the photovoltaic inverter control device with the backflow preventing function, wherein the photovoltaic inverter control device with the backflow preventing function and the control method are applied to a grid-connected irreversible system of the three-phase inverter. Whether backflow occurs in a photovoltaic inverter system or not is monitored in real time when the inverter runs, and if yes, the active current is given, amplitude limiting is carried out on the active current, the active current is limited as 0, and in other words, Idref is equal to zero; if not, whether the photovoltaic inverter system has the backflow tendency or not is judged, if the photovoltaic inverter system has the backflow tendency, the power reduction is carried out on the inverter, and if the photovoltaic inverter system does not have the backflow tendency, the process is ended. By means of the method, the output power of the three-phase inverter is kept constant, the oscillation phenomenon cannot occur, the response speed is higher, control is more timely, effective control can be carried out before a grid-connected power generation system possibly sends residual electric energy to a power grid, backflow is prevented, and the real-time performance is good especially on the occasions where the situation that a load is suddenly discharged happens frequently.

Description

technical field [0001] The invention relates to an irreversible system for grid-connected power generation of a three-phase inverter, in particular to a photovoltaic inverter control device with anti-backflow and a control method thereof. Background technique [0002] In the photovoltaic power generation system, when the three-phase inverter is irreversible grid-connected, it is necessary to configure an anti-backflow controller to ensure that the power consumed by the local load is greater than the power generated by the grid-connected inverter, and the excess power is provided by the grid. Ensure that the power provided by the grid to the load must be greater than or equal to 0, and the output power of the inverter cannot be connected to the grid. The usual practice is that the anti-backflow controller detects the total power of the grid at the access point of the grid. When it detects that the total power supplied by the grid to the load is less than a preset power, it in...

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Problems solved by technology

Sudden loading and unloading of electrical equipment occurs from time to time, and the power changes greatly. If the anti-backflow controller is not well controlled, backflow phenomenon is easy to occur. If the communication control method is adopted, it is detected by the anti-backflow controller and then communicated. 1. The inverter analyzes the command and applies control, which will cause a time delay. When the inverter responds, the reverse flow has occurred for a period of time, which may cause a certain impact on the power grid and pollute the power grid.

At the same time, the above-mentioned communication control method is to detect the total power of the grid access point when the three-phase load is balanced, but when the three-phase load is unbalanced, the total power may not reach the preset control power point, and the reverse flow will not be judged. trend, but considering that the single phase may be countercurrent or has already countercurrent, it is impossible to make an early judgment

There are two ways to reduce power by communication control. One is that the anti-backflow controller sends a fixed power reduction coefficient or an accurately calculated power reduction coefficient. When the inverter receives the power reduction command, it will reduce the current output power by a fixed coefficient output. , but after the power reduction has been completed and before the next power reduction command is received, the inverter will continue to track the maximum power, and the power output will increase again. The problem that exists in this way is that when the inverter output power and the control power are critical , the output power of the inverter is always oscillating. Another way is that the anti-backflow controller accurately calculates the power reduction coefficient and power increase coefficient. The power increase, power reduction, and power maintenance of the inverter are completely controlled by the anti-backflow controller However, when the load is unstable and fluctuates, it is difficult to determine the power coefficient of increase and decrease, which will also cause the output power of the inverter to oscillate.

[0004] In addition, if only one inverter is needed in the application, it is still necessary to configure an anti-backflow controller, and the cost is relatively high

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