Photovoltaic power generation system reactive power control method based on probabilistic fuzzy neural network

Abstract

The invention discloses a photovoltaic power generation system reactive power control method based on a probabilistic fuzzy neural network. The method comprises the following steps: S1, a photovoltaic power generation system mathematical model is built, and maximum allowable values of active power and reactive power injected into a power grid by the photovoltaic power generation system are solved; S2, a power grid fault controller model for the photovoltaic power generation system is built; S3, a probabilistic fuzzy neural network controller is built, and reference values of active current and reactive current injected to the power grid by a three-phase inverter are solved; S4, an error back propagation learning algorithm mechanism for the probabilistic fuzzy neural network controller is built; and S5, a Boost chopper circuit inner loop controller model and a three-phase inverter inner loop current control model are built. In conditions of power grid voltage mutation and fall, the working mode of the photovoltaic power generation system can be quickly adjusted so as to be adaptive to limitations of the photovoltaic array maximum output power, grid-connected inverter rated capacity and the maximum output current, and stability is strong, and the tracking speed is quick.

Description

technical field [0001] The invention belongs to the technical field of solar photovoltaic power generation, and relates to a reactive power control method for a grid-connected photovoltaic power generation system, in particular to a reactive power control method for a two-stage grid-connected photovoltaic power generation system based on a probabilistic fuzzy neural network. technical background [0002] A large number of photovoltaic power generation systems are connected to the grid, and the method of quickly cutting the photovoltaic power generation system out of the grid due to grid failure is currently not satisfactory. Suddenly cutting out large-capacity photovoltaic systems will have a serious impact on the grid system, and even cause the grid to collapse. In order to ensure that the photovoltaic power generation system does not disconnect from the grid when a fault occurs, it is necessary for the photovoltaic power generation system to have a certain low voltage ride-...

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Problems solved by technology

[0003] Since the grid voltage drops symmetrically without negative sequence components, it is only necessary to suppress the outlet current of the grid-connected inverter to prevent the overcurrent protection action and realize its low-voltage ride-through when the grid voltage drops symmetrically; however, in the actual operation of the grid, absolutely Most of the faults are asymmetrical faults, including single-phase ground faults, phase-to-phase short-circuit faults, and two-phase ground faults. Sequence current exists, the grid-connected inverter’s grid-connected power is unbalanced with the output power of the photovoltaic array, and the voltage drop on the DC side of the photovoltaic grid-connected inverter fluctuates greatly, which affects the stable operation of the photovoltaic power generation system and even causes it to go off-grid

[0004] Invention patent CN102856916B "A single-phase photovoltaic inverter reactive power control method and circuit" proposes a single-phase photovoltaic inverter reactive power control method, this method does not consider the inverter capacity and the maximum allowable output current value However, the feasibility of grid faults is debatable. In the event of single-phase faults, two-phase faults and three-phase faults in the grid, the output current of the inverter will increase significantly. On the one hand, it is easy to cause inverter elements On the other hand, the mismatch between the output power of the photovoltaic array and the power injected into the grid by the inverter will cause overvoltage of the DC bus capacitor of the inverter, which will cause the relay protection switch of the photovoltaic inverter to trip, affecting the safe and stable operation of the grid

The invention patent with the application number of 201410189148.4 "A Reactive Power Control Method for Non-isolated Single-phase Photovoltaic Grid-connected Inverter" adopts DSP control chip to sample the grid voltage and inverter output current to realize the function of leading and lagging reactive power output , this method does not consider the inverter output current limit and the PV array output power limit in the case of a grid fault, and it is difficult to meet the technical requirements of the national standard for low-voltage ride-through of photovoltaic inverters connected to the grid

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