Proportional Multiresonant Controller With Automatic Gains Adjustment For Grid-Connected Inverters

This paper proposes an improved Proportional Multiresonant (PMR) control strategy for a grid-connected voltage source inverter, capable of primary (50 Hz) current control and current harmonics compensation. In the proposed algorithm, resonant gain values of a PMR controller are variable and depend on the weight of a corresponding harmonic in the measured current signal. As a result, the system tends to operate with minimal, but sufficient for harmonics compensation parameters. This improves the stability of the system and allows it to maintain a good phase and gain margins in case of non-constant conditions in the grid. Resonant gains adjustment is a compromise between system robustness and power quality, which is usually done manually by researchers or engineers. The proposed algorithm expands the stability region of PMR-controlled grid-connected inverters (GCI) in terms of system parameters, such as AC-side impedance. The proposed controller was validated through simulations and laboratory experiments. The results show clearly the benefits of the proposed controller over a traditional one with static gains.