Second-order generalized integrator-based control method for single-phase gird-connected inverter

Abstract

The invention provides a second-order generalized integrator-based control method for a single-phase gird-connected inverter. Two-phase orthogonal fundamental current signals are reconstructed by a second-order generalized integrator; decomposition of a fundamental active component and a fundamental reactive component of a current in a synchronous rotating reference frame, so that decoupling control on the active component and the reactive component of the fundamental current is achieved; observation and control on output current harmonics of the inverter are achieved by the reconstructed fundamental current signals; and power quality of a single-phase grid-connected system is improved. The control method is simple, feasible, and insensive to an input signal, and meets the dynamic and static properties of the system. Compared with a traditional control strategy, the system can still be kept stable and has relatively good engineering practice value under the conditions of an amplitude drop and a frequency change of an input signal.

Description

technical field [0001] The invention relates to a control method for a grid-connected inverter, in particular to a control method for a single-phase grid-connected inverter based on a second-order generalized integrator. Background technique [0002] With the rapid development of distributed power generation, the proportion of renewable energy connected to the grid is increasing. Currently, low-power power generation equipment such as single-phase grid-connected inverters are required to have flexible active and reactive power control, and have good grid-connected performance. . As a single-phase grid-connected inverter, the grid information is relatively small, and the calculation of active power and reactive power is not direct enough, which makes the realization of power control difficult. [0003] In the prior art, for the single-phase system control design based on the static coordinate system, the single-phase grid-connected inverter system usually adopts a double-loo...

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Problems solved by technology

[0004] (1) Construct a two-phase quadrature signal based on the delay method. This method uses a delay module that outputs a quarter cycle, which is responsible for generating an output signal that is phase-shifted by 90° relative to the input signal, but this method depends on the input The frequency of the signal, and there is a shortage of poor filtering effect

Therefore, when the frequency of the input signal changes, the time delay of 90° cannot be accurately realized, and the dynamic performance is poor

[0005] (2) The two-phase quadrature signal is constructed based on the differential method. This method has relatively high requirements on the input signal, and is generally applicable to the case of an ideal input signal. If there is a step in the input signal, it will not be able to form a virtual two-phase. In the case of harmonics, since a filtering link must be added to the loop, it also has a greater impact on the dynamic performance of the virtual two-phase

[0006] (3) Constructing two-phase quadrature signals based on Park inverse transform, this method also faces the problem that it is difficult to respond quickly and accurately in the case of non-ideal input signals

However, after passing through the second-order generalized integrator, the filtered high-order harmonics will not be controlled, which will affect the quality of the output signal

[0008] To sum up, the single-phase grid-connected inverter control method based on the synchronous rotating coordinate system needs to construct two-phase orthogonal signals. However, the above-mentioned construction methods have their own defects.

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