Dynamic adaptability of model predictive control for power converters in inverter dominated microgrids

Abstract

This paper presents the design and development of Dynamic Adaptability (DA) feature, added to a multi-objective Model Predictive Control (MPC) of a basic grid-tied inverter with a secondary function for switching frequency reduction. The classical MPC is enhanced with dynamically varying secondary function weightage in accordance with the demand of the operating condition for self-reliant change-over across grid-tied mode and grid-forming modes in an Inverter Dominated Microgrids (IDM) environment. A customized DA database has been developed through prior investigation on the IDM, considering possible operating conditions with diverse combinations of the sampling frequency and the secondary function weight. Investigations unveiled that there is a unique value of secondary weight for every operating condition, beyond which the reference tracking is lost. This necessitated the dynamic assignment of the weight to achieve a desirable inverter performance. The dynamic weightage assignment is accomplished by accessing the DA database through the priority signals for harmonic standards, inverter losses and reference tracking, respectively. The DA imparted MPC is tested for its mode transfer capability with desired performance under all operating modes of IDM in simulations with a 15 kVA grid-tied/forming inverter and the results are presented. Further, the experimental investigations are conducted with a 10 kVA inverter on a 5-bus laboratory scale IDM emulator along with hardware-in-loop. Both inter-mode and intra-mode transitions were initiated in the IDM and the inverter performance are presented here. Both the simulation and the hardware results yielded competent values of reference tracking accuracy and mode transition times.

Keywords

• Inverter dominated microgrids
• Grid-tied inverter
• Model predictive control
• Dynamic adaptability
• Grid-tied mode
• Grid-forming mode