Adaptive MPC-based Cost Function for Capacitorless VAR Compensator in Distribution Networks

In the post-industrial digital-economy era, dealing with constant power loads along with distributed energy resources, including photovoltaic systems, energy storage, and electrified transportation are the new challenges. This is particularly important in the distribution portion of the electrical power system level where power quality and system integrity directly impact sensitive loads. The D-STATCOM is one solution to address the power quality issue as it provides dynamic reactive power and harmonic compensation. The backbone of the well-known voltage source converter, which is commonly used is the electrolytic capacitor. These capacitors have well-known failure characteristics that are accelerated in austere environments. A D-STATCOM technology that does not utilize electrolytic capacitors has the potential for increased reliability and service life with the goal of 40 years or more to match the lifetime of other power systems device. This paper proposes a method to further improve the efficiency and reliability of the capacitor-less D-STATCOM devices by penalizing high fidelity performance to reduce the average switching frequency using finite control set model predictive control (MPC). Simulation and experimental results using a testbed of 7.5kVA demonstrate a 30% reduction in switching frequency while still meeting 5% THD standards.