Single Loop Multiple Second Order Generalized Integrator based dq Control for Standalone Inverter Systems

Standalone inverters are expected to maintain their output voltage sinusoidal to ensure proper operation of the loads connected to them. Parameters such as filter design, modulation and control techniques determine the voltage waveform quality. Under linear load operation, filter size is limited by the choice of the converter’s switching frequency. In contrast, the filters are ineffective in mitigating lower frequency harmonics under non-linear loads. Thus, the control technique deployed should be capable of improving the voltage quality. This paper focuses on developing a single loop dq control scheme for output voltage control of a standalone inverter. Single-loop controllers are simpler in implementation and perform faster than conventional multi-loop controls, i.e. cascaded voltage and current control loops. The developed dq scheme is further improved to provide better output voltage quality by mitigating lower-order harmonic components under non-linear load operation. The control is simulated under linear and non-linear loads to test its effectiveness, and experiments are performed to validate them.