Reactive power control method and circuit of single-phase photovoltaic inverter

Abstract

The invention discloses a reactive power control circuit of a single-phase photovoltaic inverter. The reactive power control circuit comprises a bus voltage supporting capacitor, a single-phase full-bridge inversion circuit, a filtering inductor, an EMC (Electro Magnetic Compatibility) filtering circuit, a sampling circuit, a power switch pipe driving circuit and a DSP (Digital Signal Processor), wherein the DSP consists of a PLL (Phase Locked Loop) control module, a voltage outer ring PI control module, a current inner ring PI feedforward control module and a sinusoidal PWM (Pulse-Width Modulation) wave sending control module, and an input signal of the sinusoidal PWM wave sending control module of the DSP further includes a current inner ring current given amount Ig. The invention further provides a reactive power control method of the single-phase photovoltaic inverter. The method not only can be used for judging whether the voltage Uac of a power grid is larger than zero, and comparing the absolute value of a PWM wave sending control input modulation wave Upwm with a given triangular carrier wave Uc, but also can be used for judging whether the given current inner ring current amount Ig is larger than zero. Not only can the conduction loss of a power switching tube be reduced, and the conversion efficiency of the inverter is improved, but also the current waveform can be continuous, an output harmonic wave is reduced, and the pollution on a harmonic wave of a power grid is reduced.

Description

technical field [0001] The present invention relates to the field of photovoltaic new energy, in particular to a single-phase photovoltaic inverter reactive power control method and circuit, which can be applied to single-phase photovoltaic inverter reactive power control of any power level, and can also be applied to single-phase circuit Static var compensation device. Background technique [0002] As the proportion of photovoltaic power generation in the power grid distribution system is increasing, the harmonic pollution of photovoltaic power generation to the power grid is also increasing, which also affects the power quality of the power grid; and in large power distribution systems, other users Electrical equipment will inevitably cause harmonic pollution to the grid. For these harmonic pollution, reactive power compensation can solve the harmonic pollution of part of the power grid very well. Compared with the photovoltaic inverter system without reactive power comp...

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Problems solved by technology

[0032] On the one hand, the bipolar control method can solve the reactive power compensation control very well, but the defects of this technical solution are: the switching loss of the power switching device is large, the service life is short, especially the efficiency of the inverter is reduced;

[0033] from Figure 2C It can be seen that in the bipolar reactive power control method, in each given period of the bipolar triangular carrier Uc, the four power switch tubes T1, T2, T3, and T4 are turned on and off, and the power switch tubes work When the switching loss is large, the service life is short, which has a certain impact on the efficiency of the entire inverter

[0034] 2. General unipolar reactive power control method

[0043] Depend on Figure 3C It can be seen that the usual unipolar control method also has its own defects: it wil

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