Regulation method of single-phase LCL grid-connected inverter improved-type current regulator

Abstract

The present invention discloses a regulation method of a single-phase LCL grid-connected inverter improved-type current regulator. The method comprises the following steps: obtaining a phase wt synchronous with a power grid voltage u<g> via a phase-locked loop, wherein the phase and a current amplitude I* generated by an external voltage loop form a grid-connected current command i<ref>; comparingthe sampling signal of a grid-connected current i<2> with the command i<ref>; sending the compared error signal into a current regulator G<c>(S); taking the difference between the output of the current regulator G<c>(S) and the sampling signal of a capacitor current i<c> as a modulation signal v<m>; and comparing the v<m> with a triangular carrier wave to obtain a switch transistor control signal, wherein the feedback coefficients of the capacitor current i<c>, the grid-connected current i<2> and the power grid voltage u<g> are separately set as K<i1>, K<i2>, K<v>. According to the method, suitable closed loop parameter(s) are optimized and selected by using weight coefficient(s) according to practical application need(s), the effective damping and the control precision are ensured, and meanwhile, the relatively good dynamic performance and the relatively good robustness are obtained.

Description

technical field [0001] The invention relates to an adjustment method of an improved current regulator of a single-phase LCL grid-connected inverter. Background technique [0002] Distributed grid-connected power generation system has become the focus of research in recent years and has received extensive attention. As the core component of the distributed power generation system, the grid-connected inverter is required to have extremely high output power factor and extremely low output current total harmonic distortion. The advanced pulse width modulation technology (PWM) and digital control system widely used at present enable the grid-connected inverter to output sinusoidal current with the fundamental frequency of the grid. However, the pulse width modulation (PWM) of the inverter produces a large number of switching frequency subharmonics, which will pose a huge threat to the safe operation of the power grid. In order to realize low harmonic incoming current, it is nec...

AI Technical Summary

Problems solved by technology

However, PI control lacks sufficient ability to suppress low-order current harmonics, and cannot achieve static-difference-free regulation of grid-connected current

The introduction of grid voltage proportional feedforward is beneficial to reduce the output current stability error, but it cannot effectively suppress harmonics

The introduction of grid voltage full compensation can achieve true unity power factor output, but the compensation loop will use differential, which may face the problem of noise interference in actual engineering, and it is difficult to realize

The robustness of the PR controller to frequency changes is very poor, and the tracking performance of the non-resonant frequency is almost equal to that of the pure proportional controller, so the QPR controller is widely used at present.

The QPR controller can approximately achieve error-free tracking, but usually introduces multiple harmonic PR regulators to suppress the influence of the grid voltage background harmonic on the grid-connected current, which will increase the complexity of the control algorithm, and when the grid voltage background harmonic When the frequency of the wave is close to the system frequency, the PR regulator will significantly reduce the phase margin of the system, which will easily cause system instability

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