ABSTRACT. Distributed energy resources such as PV, WECS, and BESS, connected to the grid through static converters, are being deployed in large numbers. When a part of the electric grid operates in the island mode, isolated from the main transmission system, the local dispatchable energy resources must adequately share the load demand. This is usually done hierarchically in three levels that are: primary, secondary, and tertiary control. The primary control addresses the control of voltage and the frequency and the active and reactive power sharing among the DER often using only local measurements. This tutorial initially compares two inner loop controllers and virtual inductor implementation alternatives aiming to highlight their strong and weak points in terms of small signal stability and large disturbances resulting, for instance, from short-circuits at the grid side. In addition, a test-driven design will be presented making it possible to benchmark some of the main types of inverter-based DER primary controllers that are: (i) droop; (ii) virtual synchronous generator; and (iii) dispatchable virtual oscillator. A detailed description and a design procedure for the three considered primary and inner loop controllers, followed by an automated HIL test will be given in this tutorial. The HIL test covers a wide range of operating conditions, including steady-state with linear and nonlinear loads, as well as transients such as the one resulting from short-circuit at the load side.

ABSTRACT. Over the past 100 years, scientists have been searching for solutions to realize wireless power transfer reliably and efficiently. Their goal? A tether-free world. It is only in the past ten years that this has become reality. With the help of semiconductor devices, electromagnetic materials, and microcomputers, we can now not only charge a cell phone wirelessly, but we can also charge an electric car, implanted medical devices, under water vehicles, industrial automation equipment, robots, and automatic guided vehicles, or a humongous electric ship without plugging it in. In this talk, Professor Chris Mi will look at how his work has made wireless power transfer cheaper, faster, safer, and more efficient, enabling cable-free conference rooms, battery-less drones, and factories populated by untethered robots and autonomous vehicles. Both capacitive and inductive wireless power transfer technologies have been investigated for various applications. Experiments have shown that tens or even hundreds of kilowatts of power can be transferred over 200 mm distance with an efficiency of 97% (DC-DC) or more, and an alignment tolerance of up to 300mm. In this presentation, we will first look at the basic principle of WPT. Then we will show that safety is still one of the major concerns of WPT system for both inductive and capacitive power transfer, especially for high-power applications. Then, we will discuss two unique topologies developed by the research group of Prof. Mi, including the double-sided LCC topology and the LCLC topology for capacitive wireless power transfer. Finally, we will show some case studies that involve electric aircraft, railway, ships, and road vehicles.

ABSTRACT. Power electronic converters require auxiliary supplies for the operation of their control logic and secondary systems such as main relays and fans. For renewable applications it is advantageous to generate this supply from the converter DC bus due to ride-though considerations, but this brings with it challenges for converters that have high DC input voltages as the power supply requires a high step-down ratio. Simple buck implementations at such voltages suffer from cost and availability of switches, parasitic switching issues and high turns ration transformer designs.

ABSTRACT. Transformer-less inverters are the predominant converter used in modern photovoltaic power systems due to their reduced cost and high efficiency. An essential feature of a Transformer-less inverter is reduced common mode voltage generation on the DC BUS to minimize parasitic leakage currents so that electrical faults can be detected using a residual current detector (RCD). Most modern commercial transformer-less inverters use topologies that minimize the common mode voltage and achieve 3 – Level PWM which allows a reduction in the size of the output filter and therefore reduced cost. This paper will present a Five level PWM single phase inverter that achieves reduced common mode leakage currents using low-cost low voltage MOSFETs. The topology will be presented, and its major features discussed, and experimental results provided to illustrates its improved performance.