With the proliferation and increased use of power electronics devices (nonlinear loads) and motor loadings (such as converters, adjustable speed drives (ASDs), arc furnaces, bulk rectifiers, power supplies, fluorescent lamps, elevators, escalators, and large air conditioning systems) and also rapid increase in renewable energy generator and railway electrification systems in grid or microgrid recently, the power quality (PQ) problems become more serious, especially for lower power factor, harmonic pollution, unbalanced current, neutral current, voltage sag, voltage swell, voltage fluctuation, and resonance problems, which strongly affect the performance, efficiency, and reliability of the grid or microgrid. Advanced PQ solutions, compensator topologies, detection methods, control algorithms, and PWM techniques are the key driven force to achieve the goal of power quality enhancement in power grid or microgrid.

The purpose of this special issue is to publish high-quality research articles as well as review papers on the recent theoretical, structure, control, and analysis advancement on PQ problems and their corresponding solutions in power grid, microgrids, and railway electrification system.

Potential topics include but are not limited to the following:

• Topologies and control of power electronics converters
• Power factor correction circuits
• Static VAR compensators
• Active and hybrid active power filters
• Dynamic voltage restorers
• Unified power quality conditioners
• Advanced power quality compensators
• Advanced control techniques for power quality compensators
• Power quality in microgrids
• Power quality and renewable energy generation
• Power quality in railway electrification system