Sustainable microgrids are powered by renewable energy sources [e.g., solar photovoltaic (PV) and wind energy], and these support the reliability, resilience, and the decarbonization of the electrical grid. In recent decades, advanced nonlinear control techniques are increasingly being used to integrate power converters to meet grid requirements. This study reviews the advanced nonlinear control techniques predominantly used for grid-connected converters, namely, data-driven control, nonlinear model predictive control, direct power control, sliding mode control, disturbance-observer methods, and passivity control. Recent advances in these control policies are highlighted and various design and performance features are compared. Solutions for grid-synchronization stability, nonideal and distorted grid conditions, circulating current suppression, power quality, harmonics suppression, and grid support are presented—as well as the future trends of the advanced control methods. The study indicates that advanced control offers advantages in dynamic performance, disturbance rejection and multiobjective control over linear control for multiobjective and multitimescale microgrids.

For high-power grid-connected voltage source converters (VSC), weight reduction of the LCL filter is one of the main concerns, where a LCL filter can weigh hundreds of kilograms. It is a multidomain optimization issue to find the minimum weight of a LCL filter considering pulse-width modulation (PWM) method, control bandwidth, filter design, and magnetic components with given constraints, such as harmonic standards, semiconductor power losses, and cooling conditions. The comprehensive design procedure and analytical limits of a LCL filter for a 690-V/1.2-MW VSC is provided. In addition, a prototype system of 400 V/40 kW has been built to verify the design methodology and to investigate the impact of different PWM methods on the LCL filter.

With rapid developments in the satellite data services market, the demand for low Earth orbit (LEO) satellites is increasing. Advancements in designing lightweight satellites are essential to maximize profits from the mass production of LEO satellites in private companies. This paper proposes a new direct charging control suitable for electrical power systems for lightweight and highly reliable LEO satellites. Moreover, an analysis of the proposed solar array regulator (SAR) in terms of weight, efficiency, and reliability is presented. Additionally, the advantages of the proposed SAR in terms of lifespan and state of health (SOH) of Li-ion batteries are presented because the peak value of the battery charging current and the temperature changes during the battery charging operation are relatively small.

Paralleling of voltage source converters (VSCs) with a limited maximum output power is essential when the power rating of a system must be increased. Interleaving (ILV) of the switching signals for parallel-connected VSCs provides a better harmonic spectrum than hard paralleling (HP), i.e. applying identical signals to all VSCs. This can be particularly beneficial for grid-tied converters, since a smaller LCL filter can be realized. To investigate the performance limitations and the impact of ILV operation on the LCL filter hardware, a comprehensive optimization procedure for LCL filters and intercell transformers (ICTs) for two paralleled VSCs is presented in this paper. In addition, a comparative evaluation of HP and ILV operation of VSCs is carried out. The developed optimization procedure and the hardware benefits of ILV operation were verified through testing on a 260-kW full-scale system. Compared with the commercial state-of-the-art weight-optimized LCL filter for HP, the developed LCL filter for ILV utilizing an integrated ICT (IICT) reduces the total filter weight by 30% while guaranteeing harmonic standard compliance and meeting thermal requirements.