Pseudo-Derivative-Feedback Current Control for Three-Phase Grid-Connected Inverters With LCL Filters

Pseudo-derivative-feedback (PDF) control is, for the first time, applied to the current control of three-phase grid-connected inverters with LCL filters, which significantly improves the transient response of the system to a step change in the reference input through the elimination of overshoot and oscillation. Two PDF controllers with different terms in the inner feedback path are developed for an inverter current feedback system and a grid current feedback system, respectively. For the inverter current feedback system, a simple PDF controller with a proportional term is used. The influence of the controller parameters on the transient performance is discussed in detail. Compared with a PI controller, the PDF controller is able to eliminate the transient overshoot and oscillation easily, while maintaining a fast response. For the gird current feedback system, a PDF controller with a proportional term and a second-order derivative is developed. The implementation and design of the PDF controller are presented. Active damping is achieved with only the feedback from the grid current, and at the same time, the system transient response is improved. Both theoretical analysis and experimental results verify the advantages of the PDF control over PI control methods.