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Coordinated Control Research of Grid-Connected Two-Stage Power Converter System

The DC bus voltage of grid-connected two-stage power converter system (PCS) is always vulnerable to abrupt change of output power. To solve this problem, the mathematical models of the converter and its control system is established firstly. The control parameters designing via classical control theory is followed. This is continued with analyzing the cause of the voltage fluctuations. Theoretical analysis points out that the voltage fluctuations can not be completely suppressed or eliminated just via parameters design and steady-state feedforward compensation. As a consequence, we propose an improved control strategy by setting a first derivative element in series to the steady-state feedforward compensation to compensate for the delay of the response. Experimental results indicate that the proposed feedforward compensation method can effectively suppress transient voltage fluctuations, and speed up system dynamic response.