Power equalization device for parallel inverter based on current sag characteristics and control method

Abstract

A power equalization device for parallel inverter based on current sag characteristics and a control method are disclosed. The power equalization device comprises a DC voltage stabilized power supply,an inverter control unit and a central controller. Each inverter control unit includes a three-phase inverter and an improved current sag control module. The output current of the three-phase inverter is synthesized by the improved current sag control module, and then the SPWM wave is output through the voltage-current dual-loop controller and the SPWM pulse modulation module to control the inverter. Central control acquires instantaneous value of output current at common couple point for [alpha] [beta] transformation, calculates the instantaneous reactive current, according to the ratio of the reactive current value of each three-phase inverter in the parallel inverter to obtain the average value of the reactive current as the reference value of the inverter, The reference value is transmitted to each reactive current sample value and subtracted to make difference and multiplied by the integral constant feedback, and the reactive output bias is adjusted by the following action of theintegral regulator, so that the reactive current is proportionally divided according to the capacity, and the circulating current is eliminated.

Description

(1) Technical field [0001] The invention belongs to the category of power electronic control, and relates to the field of current droop control of grid-connected inverters, in particular to a parallel-connected inverter power sharing device and a control method based on current droop characteristics. (2) Background technology [0002] In recent years, with the reduction of fuel energy resources and the continuous deterioration of the environment, more and more renewable energy is connected to the microgrid through distributed generation (DG, distribution generation), making the microgrid gradually become a research hotspot. During the operation of the microgrid island, there is no reference for the voltage and frequency provided by the large grid, and the inverter provides the voltage and frequency for the entire grid. Therefore, the control of the inverter is very important and affects the microgrid to a large extent. power quality. [0003] In the prior art, the droop con...

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Problems solved by technology

However, the traditional droop control method depends on the characteristics of the line impedance, and the inconsistent line impedance will cause the output power of the inverter to be unable to be shared equally, and even cause serious circulating current; therefore, most of this method is only for parallel connection of inverters with the same capacity. However, inverters with different capacities inevitably exist in practical applications. The parallel connection of inverters with different capacities leads to uneven power distribution and even has a serious impact on equipment.

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