Grey Wolf Optimizer-Based Optimal Inner Loop Control and SRF-PLL for Grid Tie Inverter Under Low Frequency Oscillation

This paper presents the optimization of inner loop control and SRF-PLL on a Grid Tie Inverter (GTI). GTI requires a PLL to be able to synchronize with the grid. Synchronous Reference Frame PLL (SRF-PLL) is an effective method used to synchronize GTI with the grid. Meanwhile, to control current, the GTI requires inner loop control. Both control systems must have a good response when disturbances occur that can cause low frequency oscillations. The high complexity makes setting up the inner loop control system and SRF-PLL difficult. So this paper proposes simultaneous optimization of the inner loop control and SRF-PLL to get a good response from the GTI when fluctuations occur in the system. Grey Wolf Optimizer (GWO) is used to set parameters in the inner loop control of GTI with SRF-PLL. The oscillation damping of the control system is formulated as an objective function. Transient response and steady state error are used as limits in optimization carried out when low frequency oscillations occur due to disturbances in the system. The optimal parameters obtained have been verified on a series of GTI simulators with results confirming that this method can optimize the response of the inner loop control and SRF-PLL on the Grid Tie Inverter (GTI) simultaneously.