Abstract：PWM grid-connected converters are widely used in new energy generation, SVG and APF. LCL filter is usually adopted to filter the switch ripple of grid current. Because of the small inductance of the grid-side inductor, the harmonic current in the grid-side inductor and filter capacitor is caused by the harmonic voltage, resulting in distortion of the grid current. The conventional inverter-side current feedback control scheme only controls the inverter-side current and has no ability to suppress the grid harmonic current because of lacking of the background harmonic information of the grid. The harmonics can be effectively suppressed by compensating the capacitor current, but it will lead to an unstable system. In light of the above, this paper proposes an improved scheme based on inverter-side current feedback control with partial capacitor-current feedforward. The grid harmonic current can be specifically suppress by the harmonic controllers. And the system stability is analyzed. In addition, the capacitor-current extraction scheme based on multi-second-order generalized integrator is proposed in this paper. Finally, the effectiveness of the proposed scheme for suppression of grid harmonic current and capacitor current extraction are verified by detailed experimental results.
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2018, Vol. 33 
