Cascaded H-bridge photovoltaic inverter power adaptive harmonic compensation strategy

Abstract

The invention discloses a cascaded H-bridge photovoltaic inverter power adaptive harmonic compensation strategy, belongs to the field of photovoltaic power generation, and aims to solve various problems caused by unbalanced transmission power between cascaded H-bridge inverter modules. The method comprises the following steps: controlling the direct-current side capacitor voltage of all H-bridge converters to enable photovoltaic modules corresponding to the H-bridge converters to work at the maximum power point; selecting the reference power of each H-bridge converter according to the modulation degree of each H-bridge converter, and calculating the selected reference power to obtain an active current instruction value; controlling the grid-connected current; and calculating the modulationdegrees of all H-bridge converters, judging the working mode of the system, and calculating the modulation wave of each H-bridge converter by adopting different modulation wave calculation methods. Compared with the prior art, the linear modulation range of the cascaded H-bridge photovoltaic inverter is further expanded, and the capacity of the cascaded H-bridge photovoltaic inverter for coping with power imbalance is improved.

Description

technical field [0001] The invention belongs to the field of photovoltaic power generation in the field of electrical engineering, and in particular relates to a power adaptive harmonic compensation strategy for cascaded H-bridge photovoltaic inverters. Background technique [0002] Compared with traditional inverters, cascaded H-bridge photovoltaic inverters have the advantages of component-level maximum power point tracking (MPPT-Maximum Power Point Tracking), low harmonic content of grid-connected current, small filter size and easy modularization. , has broad development prospects and market potential. [0003] In the cascaded H-bridge photovoltaic inverter, each H-bridge converter is connected to a photovoltaic module, and each photovoltaic module can work at the maximum power point by independently adjusting its DC side capacitor voltage. However, if some photovoltaic modules are blocked or damaged, there will be a large difference in the active power transmitted betw...

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Problems solved by technology

[0009] 1) Hybrid modulation can expand the linear modulation range of the H-bridge converter to 4 / π, but it will increase the voltage fluctuation of the DC side capacitor of the H-bridge converter and affect the efficiency of MPPT

[0010] 2) The reactive power compensation strategy can deal with severe power imbalance, but this method will reduce the system power factor

[0011] 3) The third harmonic compensation strategy will not aggravate the fluctuation of the capacitor voltage on the DC side of the H-bridge converter and can ensure the unit power factor operation of the system, but its ability to deal with power imbalance is weak

[0012] 4) The harmonic compensation strategy retains the advantages of the third harmonic compensation, and further expands the linear modulation range of the H-bridge converter, but in the case of more serious power imbalance, the harmonic compensation strategy will also fail

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