Proportional multi-resonant-based controller design method enhanced with a lead compensator for stand-alone mode three-level three-phase four-leg advanced T-NPC inverter system

This study presents an inverter current sampled double-loop proportional multi-resonant (PMR)-based control technique for three-level (3L) three-phase four-leg (3P4L) advanced T-type neutral point clamped (AT-NPC) stand-alone mode inverter. Apart from the conventional linear controller the PMR controller has the ability to track a sinusoidal reference and does not require any axis transformation. Therefore, the main advantage of the proposed control technique for a 3P4L inverter is to independently control the output phase voltages when feeding a single phase and/or three phase loads. This is achieved by the inverter current sampled double-loop controller with a lead compensator in order to increase the control system phase margin unlike the capacitor current sampled controller. Thus, the harmonic compensation capability of the controller is increased which strengthens the controller against highly non-linear load types. The design procedures of the controller for the system are analytically explained. Then, the steady-state and dynamic performance of the controller is tested in a 3L 3P4L AT-NPC inverter system through many simulations and experimental studies. The results verify the fast-dynamic performance and the achievement of the low total harmonic distortion with a maximum of 2.89% for the 3L 3P4L AT-NPC inverter system even under serious non-linear load type.