High-stability control method of LCL type grid-connected inverter system under weak power grid

Abstract

The invention discloses a high-stability control method of an LCL type grid-connected inverter system under a weak power grid, and belongs to the technical field of photovoltaic grid-connected inverter control. The problem that a conventional grid-connected inverter is likely to be unstable in a weak power grid environment is solved. Aiming at the influence of power grid impedance increase and small signal disturbance on a phase-locked loop and an LCL filter in a grid-connected inverter system under a weak power grid, a double-grid-connected current loop feedback active damping strategy of a second-order generalized integral is adopted, a self-adaptive second-order resonance integrator active damping feedback function is constructed, a proportional resonance function is used as a current loop controller, and the grid-connected inverter system is controlled by the proportional resonance function. Virtual impedance correction is carried out on the control system, and a voltage feedforward controller is designed; a double-second-order adaptive filter-based sequence-dividing phase-locked loop is designed; through demonstration, reasonable virtual impedance correction is added, the use of measuring devices in hardware can be reduced while a good damping effect is achieved, the hardware cost is saved, and the control strategy can ensure the stability and robustness of the system.

Description

technical field [0001] The invention relates to the technical field of photovoltaic grid-connected inverter control, in particular to a high-stability control method of an LCL grid-connected inverter system under a weak grid, which is suitable for weak grid and high-impedance grid-connected conditions. Background technique [0002] The distributed generation system is to connect the power generation source with the load and the grid through the power electronic conversion device. Due to factors such as the increase in the penetration rate of distributed generation, the impedance of long-distance transmission lines, and the leakage inductance of transformers, the rigidity of the grid connection is weakened, and the impact of grid impedance on grid-connected inverters cannot be ignored. When the grid has a large impedance, the grid rigidity will become weaker. Therefore, the grid-connected inverter control design cannot make the grid-connected conditions the same as the tradi...

AI Technical Summary

Problems solved by technology

[0005] The purpose of the present invention is to overcome the problem that the existing conventional grid-connected inverter is prone to instability in a weak grid environment, and to provide a high-stability control method for an LCL type grid-connected inverter system under a weak grid. Adapt to the active damping feedback of the second-order resonant integrator and the sequential phase-locked loop of the biquad adaptive filter to improve the stability and robustness of the grid-connected inverter system under the condition of high impedance and grid fluctuations under weak grid conditions

Images