Improved harmonic injection pulse‐width modulation variable frequency triangular carrier scheme for multilevel inverters

This study proposes an optimised controllable pulse-width modulation (PWM) scheme suitable for multilevel inverters. Seeing the need for improving the output voltage characteristics such as total harmonic distortion, low-order harmonic and distortion factor, an improved harmonic injection PWM variable frequency triangular carrier modulation technique is employed for off-line mode. For this purpose, the carrier signal frequencies at each level (carrier-based), and also amplitudes and orders of the harmonic-injected signal (reference-based) are considered as controllable parameters. The proposed technique benefits are operating with considerably fewer numbers of the pulses per cycle, low switching losses, and improvement in the output voltage characteristics. However, selective harmonic elimination and optimal switching angles are the most common modulation techniques, but they employ only one angle as a control parameter at each level of the output waveform. Hence, the modulation scheme can consider more angles at each level as controllable parameters by applying multi-objective particle swarm optimisation and non-dominated sorting genetic algorithm II (NSGA-II). Simulations are conducted in 5-, 7- and 9-level inverter. Finally, the effectiveness of the studies is validated by obtaining experimental results on a single-phase 1 kW 7-level inverter prototype

Intelligent Secondary Control of Islanded AC Microgrids: A Brain Emotional Learning-based Approach

This paper proposes a distributed intelligent secondary control (SC) approach based on brain emotional learning-based intelligent controller (BELBIC) for power electronic-based ac microgrid (MG). The BELBIC controller is able to learn quick-auto and handle model complexity, non-linearity, and uncertainty of the MG. The proposed controller is fully model-free, indicating that the voltage amplitude and frequency deviations are regulated without previous knowledge of the system model and parameters. This approach ensures low steady-state variations with higher bandwidth and maintains accurate power-sharing of the droop mechanism. Furthermore, primary control is realized with a robust finite control set-model predictive control (FCS-MPC) in the inner level to increase the system frequency bandwidth and a droop control in the outer level to regulate the power-sharing among the distributed generations. Finally, experimental tests obtained from a hardware-in-the-loop testbed validate the proposed control strategy for different cases