Sensorless Operation of a PWM Rectifier for a Distributed Generation

This paper presents a power converter configuration interfaced with the distributed ac power generation system to regulate the dc bus voltage. It is composed of a pulsewidth modulation (PWM) rectifier directly tied to the generator´s terminals without ac reactors. Hence terminal voltages are not useful due to the switched pulse of the PWM rectifier and also it is not the terminal voltages, but the generator´s electromagnetic field voltages that are required for a synchronous angle of the PWM rectifier. This paper proposes a method for estimating the synchronous angle through only the measurement of the ac line currents, and is thus called the voltage sensorless control strategy. For a smooth startup of the PWM rectifier, a technique of setting the integrators´ initial values in the proposed estimator is described. In this paper a commercial engine generator set is used as the distributed generation system. The feasibility of the overall system and algorithms has been verified by the experimental results