Grid Connected Current/Power Coordinated Control Of Quasi Z-Source Inverter In Unbalanced Power Grid

Abstract

Under the condition of unbalanced grid voltage, the non-off grid operation of photovoltaic system will lead to the fluctuation of system output power and obvious harmonic distortion of grid connected current. Because stable output power and better grid connected current quality cannot be realized at the same time, a coordinated control strategy of power fluctuation suppression and current balance is proposed. The harmonic component in the output current is adjusted by using the adjustment coefficient, and the proposed strategy is realized based on reduced order resonance control. The voltage/current positive and negative sequence separation link and phase-locked loop are not needed in this method so that the control structure is simpler, and instantaneous power is used to calculate the reference command value of grid connected current. The coordinated control of power/current is realized by MATLAB simulation, which verifies the feasibility and effectiveness of the proposed strategy.

Keywords

• unbalanced power grid
• quasi z-source inverter
• power suppression
• current balance
• coordination control