Emerging Converter Topologies and Control for Grid Connected Photovoltaic Systems

Continuous cost reduction of photovoltaic (PV) systems and the rise of power auctions resulted in the establishment of PV power not only as a green energy source but also as a cost-effective solution to the electricity generation market. Various commercial solutions for grid-connected PV systems are available at any power level, ranging from multi-megawatt utility-scale solar farms to sub-kilowatt residential PV installations. Compared to utility-scale systems, the feasibility of small-scale residential PV installations is still limited by existing technologies that have not yet properly address issues like operation in weak grids, opaque and partial shading, etc. New market drivers such as warranty improvement to match the PV module lifespan, operation voltage range extension for application flexibility, and embedded energy storage for load shifting have again put small-scale PV systems in the spotlight. This Special Issue collects the latest developments in the field of power electronic converter topologies, control, design, and optimization for better energy yield, power conversion efficiency, reliability, and longer lifetime of the small-scale PV systems. This Special Issue will serve as a reference and update for academics, researchers, and practicing engineers to inspire new research and developments that pave the way for next-generation PV systems for residential and small commercial applications

DISCRETE TIME QUASI-SLIDING MODE-BASED CONTROL OF LCL GRID INVERTERS

Application of a discrete time (DT) sliding mode controller (SMC) in the control structure of the primary controller of a three-phase LCL grid inverter is presented. The design of the inverter side current control loop is performed using a DT linear model of the grid inverter with LCL filter at output terminals. The DT quasi-sliding mode control was used due to its robustness to external and parametric disturbances. Additionally, in order to improve disturbance compensation, a disturbance compensator is also implemented. Also, a specific anti-windup mechanism has been implemented in the structure of the controller to prevent large overshoots in the inverter response in case of random disturbances of grid voltages, or sudden changes in the commanded power. The control of the grid inverter is realized in the reference system synchronized with the voltage of the power grid. The development of the digitally realized control subsystem is presented in detail, starting from theoretical considerations, through computer simulations to experimental tests. The experimental results confirm good static and dynamic performance

European White Book on Real-Time Power Hardware in the Loop Testing : DERlab Report No. R- 005.0

The European White Book on Real-Time-Powerhardware-in-the-Loop testing is intended to serve as a reference document on the future of testing of electrical power equipment, with specifi c focus on the emerging hardware-in-the-loop activities and application thereof within testing facilities and procedures. It will provide an outlook of how this powerful tool can be utilised to support the development, testing and validation of specifi cally DER equipment. It aims to report on international experience gained thus far and provides case studies on developments and specifi c technical issues, such as the hardware/software interface. This white book compliments the already existing series of DERlab European white books, covering topics such as grid-inverters and grid-connected storag

Power Converters in Power Electronics

In recent years, power converters have played an important role in power electronics technology for different applications, such as renewable energy systems, electric vehicles, pulsed power generation, and biomedical sciences. Power converters, in the realm of power electronics, are becoming essential for generating electrical power energy in various ways. This Special Issue focuses on the development of novel power converter topologies in power electronics. The topics of interest include, but are not limited to: Z-source converters; multilevel power converter topologies; switched-capacitor-based power converters; power converters for battery management systems; power converters in wireless power transfer techniques; the reliability of power conversion systems; and modulation techniques for advanced power converters

Design of a Grid-Forming, Multi-Loop Control Scheme for Parallel Connected, Three-Phase Quasi-Z-Source Inverters

The quasi-Z-source inverter has been the subject of numerous power electronics publications since its invention in the early 2000s. While often applied as an interface for renewable energies such as wind and PV, there is a lack of literature where the qZSI functions in a grid-forming role. The goal of this work is to design and implement a control scheme for a 3-phase qZSI in order to enable it to operate in a grid-forming role. The qZSI is analyzed in great detail and compared to a conventional voltage source inverter scheme that is commonly used in renewable energy interfaces. Literature is presented to demonstrate the need for current programmed mode (CPM) control for the dc side of the qZSI, and the control scheme is compared to a common control scheme used for boost converters. Then, recent literature is presented to support why the universal droop control (UDC) scheme was chosen for the ac-side control for this work. After contextualizing the design of the overall qZSI control scheme, the final control scheme is presented, which utilizes CPM indirect control on the dc-side, and UDC on the ac side. The stability and dynamic response of the system is analyzed in detail for the chosen gains and component values. Through PLECS simulations, the qZSI system presented in this work demonstrated its ability to operate in a grid-forming role and potentially superior performance when compared to conventional VSI systems. While a much more optimized design approach is needed for both the qZSI and VSI to truly compare the two systems, this work demonstrates that the qZSI is more than capable of operating in a grid-forming role. It handles large step changes in load and input voltage with quick rise times and good damping, and exhibits quick and stable responses when operating in parallel with other inverters. This work concludes with some considerations for future work on this topic