Performance comparison of DC and AC controllers for a two-stage power converter in energy storage application

•Same block diagram and frequency-design methodology are used to design current and voltage controllers for different converter topologies such as DC–DC boost, DC–DC buck, inverter (DC–AC) and rectifier (AC–DC). Similarities in sizing, modeling and control design equations are presented in the paper.•Performance comparisons of several DC and AC controllers through simulations, in addition to tuning of the selected controllers by adjusting their control-loop parameters.•Development of a supervisory controller to manage the operating modes of the system: a finite state machine is employed to manage the operating modes of two bidirectional controllers, monitor the system parameters and control the connection of the battery bank and the main grid.•Experimental verification of a scaled power converter: with the same procedure, a 5-kW converter was designed and simulated, and a 100-W converter was designed and tested, due to availability of components. This paper presents a procedure for modelling and controlling a single-phase, two-stage, bidirectional DC–AC converter for application of energy storage system (ESS) in autonomous microgrids, in addition to experimental verification of its uninterruptible power supply (UPS) functionality. Average theory and frequency analysis are utilized to model the power converters and design the controllers in a generic fashion. Performance comparison of different controllers (type-2 and type-3 Venable compensators, Proportional Integral, Resonant-PI and multiple-RPI) is realised through simulations and tests. To tune the controllers, parameter values of crossover frequency and phase margin are adjusted by comparing simulation responses of the converters. A 5-kW ESS is evaluated through simulations during normal operation (grid-connected or stand-alone mode), as well as under transition events such as disconnection and recovery of the main grid. Besides that, a 100-W system was implemented, in which grid-connected mode was evaluated by measuring the power factor (about 0.998 in simulation and 0.993 in test at rated power), while stand-alone mode was evaluated by the total harmonic distortion of the output voltage (about 1.57% in simulation and 2.35% in test at rated power). The presented procedure can also be used to design higher power systems.