The delay problem of a deadbeat current controller for solar invcrters is investigated. By applying the z-transformation technique, it is found that system stability is degraded because of the delay of one-sampling-period due to the nonzero computational time of the microprocessor and the conversion time of AD converters. The frequency response of the system loop gain also indicates that the inverter output current oscillates at one sixth of the sampling frequency. Through the analysis presented, it is shown that the predictive current observer based controller compensates this time delay, while remaining an accurate current controller for solar inverters. Computer simulations are performed, and a I kW solar inverter prototype is constructed to verify the analytical results.

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