Constant Power Load Instability Compensation in an Autonomous Microgrid

Recently, the Kingdom of Saudi Arabia has decided to engage around 60 GW of renewable energy sources (RESs) based power generation in its electricity generation sector. RESs are connected in a prudent approach to implement a Microgrid (MG) increasing the energy efficiency, improving the grid power quality, and low carbon emissions reduction. MG can work in two different modes; autonomous and grid connected modes. In both modes, power electronic converters are playing an ever increasingly important role in involving RESs and loads. Microgrid loads can be categorized into several types such as controllable loads and critical loads. The critical loads such as constant power loads (CPLs) and constant voltage loads (CVLs) require proper attention for better performance. Rectifiers and voltage regulators are behaving as constant power loads (CPLs) and expansively used in MG impacting the MG power quality and causing serious instability problems such as negative incremental resistance, synchronization, and control loop dynamics problems. Different compensation schemes are proposed to overcome the MG instability problem. Based on location of the compensation, these techniques can be classified into feeder side compensation, intermediate circuitry compensation and load side compensation. In the feeder side compensation, an implemented controller is adjusted to overcome the CPL instability problems. In the second technique, some intermediate circuitry or element is implemented to prevent the feeder side experience the load side. In the load side compensation, a supplementary arrangement is implemented in the load side to maintain the system stability. The load side stability is managed to be the MG compensation key because most of MGs loads are located close to their sources. The instability problem will be more complicated with high penetrated CPLs in MG systems. This project aims to design a new load compensation approach to defeat the instability problems of high penetration level of CPLs in an autonomous MG. The proposed compensation technique will improve the MG stability and avoid some synchronization problems like tuning difficulties. The proposed control strategy will be implemented in a laboratory scale prototype through Real Time Digital Simulator (RTDS) to validate the proposed compensation technique