In this paper, a proton exchange membrane fuel cell (PEMFC) is implemented as a grid-connected electrical generator that uses hydrogen gas as fuel and air as an oxidant to produce electricity through electrochemical reactions. Analysis demonstrated that the performance of the PEMFC greatly depends on the rate of fuel supply and air supply pressure. Critical fuel and air supply pressures of the PEMFC are analysed to test its feasibility for the grid connection. Air and fuel supply pressures are varied to observe the effects on the PEMFC characteristics, efficiency, fuel supply, and air consumption over time. The PEMFC model is then implemented into an electrical power system with the aid of power electronics applications. Detailed mathematical modelling of the PEMFC is discussed with justification. The PEMFC functions as an electrical generator that is connected to the local grid through a power converter and a transformer. Modulation of the converter is controlled by means of a proportional-integral controller. The two-axis control methodology is applied to the current control of the system. The output voltage waveform and control actions of the controller on the current and frequency of the proposed system are plotted as well. Simulation results show that the PEMFC performs efficiently under certain air and fuel pressures, and it can effectively supply electrical power to the grid.

The integration of battery energy storage (BES) with photovoltaic (PV) systems is becoming economically attractive for residential customers. The conventional approach for the interconnection of PV and battery systems requires at least two separate power converters that results in multistage power conversion for some power flows. The dc-dc three port converters (TPCs) are an alternative solution. These converters have many topological variants and possess different operating principles, topological benefits and limitations, and complexities. This paper concentrates on the topological study of TPCs for integrated PV and BESS applications in the power range from a few hundred watts to 350 kW. These are classified into three different categories based on their isolation features between the ports to establish a topological mapping of the reported TPCs. This provides a framework that systematically explores the full range of technical benefits and limitations of each TPC topology. This paper also examines the possible extension of the TPC topologies for grid-interactive PV-BES systems where bidirectional power flow capability is required between grid and BES systems. This extensive review will provide a useful framework and a strong point of reference for researchers for the selection of TPC topologies to meet the system requirements for PV and energy storage applications.

This paper presents a dual active bridge (DAB) converter for a battery energy storage system (BESS) or an electric vehicle (EV) to deliver battery-to- home (B2H) and battery-to-grid (B2G) or vehicle-to-home (V2H) and vehicle-to-grid (V2G) services. The DAB topology is preferable for EV charging systems due to galvanic isolation and bidirectional power flow capabilities, however this topology increases reactive current peak and loses zero voltage switching (ZVS) operation at light loads if it is not controlled with improved modulation strategies and proper reactive power optimization (RPO) algorithm. This paper proposes a mixed modulation method and a RPO algorithm based on power system concepts that reduce the reactive power and provide ZVS operation over a wide voltage range. The mixed modulation allows one of the bridges of DAB converter to run with 2-level while and other to run with 3-level square wave modulation. Due to the complexities associated with the analytical solution using time domain analysis, this paper develops detailed universal expressions of a DAB converter using harmonic analysis method. Analytical identification of ZVS boundaries and DSP implementation of RPO algorithm become easier with these universal expressions. Multiple modes analysis for different operational states are no longer required. Simulation models of the DAB converters have been developed to show the results with different modulation strategies. The theoretical analysis of modulation strategies, RPO algorithm and ZVS operation are validated by experimental results on a laboratory scale prototype. Results show that the proposed mixed modulation with RPO algorithm improve the DAB converter performance.

The large-scale integration of distributed photovoltaic generation causes several power quality issues in low voltage (LV) distribution networks. Network voltage profile variations severely affect the LV distribution networks. The four-leg unified power flow controller (4L-UPFC) has series and shunt converters that can address the power quality issues. However, instantaneous power theory shows that second-order harmonic voltage (2ωHV) appears at the dc-link capacitor of the 4L-UPFC during any unbalanced operations. This article proposes control strategies for series and shunt converters that will simultaneously regulate the load voltages of a distribution feeder while suppressing the 2ωHV term on the dc-link of the UPFC. A controlled negative sequence current from the shunt converter is used to suppress the 2ωHV term on the dc-link. The active suppression of the 2ωHV term allows electrolytic capacitors to be replaced with small long life ceramic or film capacitors, and this does not require additional passive compensation. Stability analysis of the control loops demonstrates the overall stability of the converter system. The proposed control methods have been implemented on a Texas DSP (F28377D). An experimental demonstration on a laboratory scale prototype shows that the proposed control methods can effectively regulate the load voltages at LV distribution feeders and suppress the 2ωHV on the dc-link of UPFC during unbalanced loads and supply conditions.