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Summary Multilevel inverter based shunt active power filter is cost‐effective and decisive solution for mitigating numerous power quality problems in case of medium‐voltage distribution sector. Performance of the filtering unit and nature of source current mainly depends on current control loop of control algorithm. Conventionally, proportional‐integral controllers are used in current control loop for AC current controllability, but it suffers from severe problems, namely, magnitude and phase error in steady‐state conditions. This paper presents an advanced current control loop that consists of a new breed of compensator called proportional‐resonant compensator for cascaded H‐bridge multilevel inverter based shunt active power filter in order to maintain zero steady‐state current error. Stability of proposed current control loop and closed‐loop control mechanism is extensively checked and analyzed using transfer function approach and root‐locus criteria. A complete mathematical analysis of the proposed control system has been presented, and parameters of proportional‐resonant regulator are finely tuned using bode plot technique. The performance of proposed control mechanism is tested using MATLAB/Simulink. A detailed experimental analysis has been carried out to verify effectiveness of the proposed controller over conventional one. Source current waveform becomes sinusoidal, and harmonic limits are in compliance with IEEE‐519 standard after successful operation of filtering unit.

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This study aims to propose optimised and robust current controller for the transformerless grid-integrated photovoltaic inverter. Challenge of ensuring improved power quality while minimising the DC-component under non-ideal grid condition is at the forefront in the photovoltaic system. In this context, an advanced current controller is designed and developed in the stationary reference frame with proportional-integral (PI) plus four-vector PI (4VPI) controllers. The PI-controller modulates the shape of fundamental current to follow its reference induced from outer DC-link loop. Meanwhile, 4VPI controllers are tuned at the multiple of grid frequencies including third-(3ω 0), fifth-(5ω 0), seventh-(7ω 0), and ninth-(9ω 0) to introduce infinite gain and thereby alleviating stationary errors in the current loop of the photovoltaic inverter. The most distinguishing feature of the proposed controller is its inherent control robustness, and therefore, it operates satisfactorily against control delay time and frequency excursion. Traditionally, cumbersome trial-and-error techniques have been largely employed to adjust the PI-VPI controller gains. Nonetheless, tuning of these parameters has made many practitioners switch-off from employing the proposed controller. Given this, the particle swarm optimisation algorithm is proposed. Finally, the practicality of the proposed controller is verified through comprehensive set of simulation and experimental tests conducted on a laboratory-developed prototype using dSPACE-1104.

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