A VOLTAGE MODE CONTROL FOR SINGLE-PHASE INVERTERS IN PARALLEL OPERATION

Abstract

The active and reactive power, P and Q, are important variables when dividing the load for parallel connected inverters using a droop controller. P and Q are calculated based on the transformer output voltage value and the load current. However, when it comes to sharing the nonlinear load power, low pass filters with very low cut-off frequency are used to eliminate harmonics of the load current for increasing accuracy when calculating P and Q. These filters slow down the dynamics of the system, reduce the reliability and cause control errors. This paper uses the DSOGI algorithm to replace the low pass filter, increasing the dynamics and stability of the system. The voltage mode control with a simple observer (DOB) can ensure that the quality of the inverters output voltage and current follows an IEEE standard. The algorithms were tested through simulation on Plecs, with system consists of 2 one phase inverters working in parallel.