This paper presents a decoupled active and reactive power control scheme for grid-tied quasi-impedance source cascaded multilevel inverter (qZS-CMI). For photovoltaic (PV) applications, the proposed control scheme is based on an enhanced finite-set model predictive control (MPC) to harvest the desired active power from the PV modules with the ability to provide the ancillary services for the grid. The proposed control scheme has two modes of operation: normal grid mode and low voltage ride through (LVRT) mode. In normal grid mode, the controller commands the qZS-CMI to operate at the global maximum power point (MPP). The proposed technique regulates the impedance network's current and voltage according to the MPP of PV strings and grid current/voltage requirements. In LVRT mode, the controller commands the qZS-CMI to provide the required reactive power to the grid during voltage sags as an ancillary service from the inverter as imposed by the grid codes. The main features of the proposed system include the global MPP operation during normal grid condition, LVRT capability during a grid voltage sag, mitigation of the PV modules mismatch effect on overall energy harvesting, seamless transition between a normal grid and LVRT modes of operation, and an efficient predictive controller that exploits the model redundancies in the control objectives. Several real-time experiments are conducted to verify the system performance with transients in both the solar irradiance and the grid voltage.

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This paper presents a model predictive self-healing control (MPSC) scheme for battery system interfaced dual active bridge (DAB) converter in navy ship power system (NSPS) with pulsed power loads (PPLs). The voltage and frequency of NSPS are vulnerable to PPLs energization. A properly controlled battery system with fast dynamic response can mitigate this vulnerability. Model predictive control (MPC) is a potential solution for the battery system interfaced DAB converter to achieve fast dynamic response and mitigate disturbances imposed to the NSPS by PPLs. However, conventional MPC framework suffers from current prediction error due to the pulsating AC-link inductor's voltage profile in DAB converter. This paper proposes a self-healing control loop that utilizes the feasible range of power transfer in conjunction with the AC-link inductor's voltage profile. The proposed method can validate and autonomously correct the predicted current and phase shift in DAB converter interfaced a battery system. The proposed control scheme on DAB converter prevents voltage and frequency collapse in a hybrid AC/DC NSPS particularly during the PPL energization. The system stability is studied based on Lyapunov stability analysis. The theoretical concepts are validated by several case studies implemented on a hardware-in-the-loop (HIL) testbed of a NSPS. The case studies demonstrate voltage and frequency regulation of the NSPS with fast dynamic response during PPLs energization. The proposed MPSC performance is compared with proportionalintegral (PI) based control for DAB in NSPS with PPLs.

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This article presents an effective resonance suppression control for grid-interactive inverters with LCL filter in weak grid conditions. The resonance suppression mechanism is based on an adaptive model predictive control (AMPC). The large parasitic impedance and low short-circuit ratio (SCR) of weak grid challenges the operation of grid-interactive inverters. Specifically, the LCL filter resonance may get excited, resulting in collapse of the inverter operation. The proposed AMPC scheme autonomously alter the controller objectives for suppressing the resonance. The proposed control scheme alters the feedback currents based on the grid-condition. During the stiff grid conditions, grid current serves as feedback to the controller. While in the weak grid conditions, the inverter current is selected as feedback signal. The toggling action between these two feedback currents is determined by comparing moving RMS of grid current with desired current as constraint in the proposed AMPC cost function. The performance of proposed controller is verified experimentally. The results demonstrate that the proposed controller features robust performance under various grid conditions, model parameter mismatch, grid disturbances, seamless transition between controller modes of operation and feedback alteration to attain resonance suppression, eliminates required tuning efforts in comparison to classical multi-nested loop control schemes, and provides high power quality according to IEEE standard 1547.