3L-T-Type QZSI Participation in Grid Voltage Imbalance Control in Grid-connected Photovoltaic Systems
In addressing the problem that traditional inverters cannot suppress the input active power oscillation component when working under unbalanced network voltage,a control strategy based on a three level T-type quasi-Z source inverter(3L-T-type QZSI)to suppress the active power oscillation component was proposed.The reference current for grid-connected QZSI was derived from power theory,achieving a control strategy with constant grid-connected active power and unit power factor as the goal for grid connection.That is,a second-order generalized integrator(SOGI)was used to complete the positive and negative sequence separation of the voltage,and then the carrier-based level-shift pulse width modulation(LS-PWM)technique was combined to regulate the duty cycle of the power switch through state and the superimposed balance component to realize the DC-side voltage control and midpoint voltage balance.Finally,the voltage imbalance of the power grid was simulated on the Simulink platform,and the simulation results show that the strategy can effectively suppress the active power two-fold fluctuations of intermittent energy sources,which is conducive to the mid-point potential balance and the stable operation of intermittent energy sources on the grid.
three-level invertergrid voltage imbalanceconstant active powerthrough duty cyclemidpoint potential balance
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维普
