Active damping (AD) is a popular approach to suppress the resonance in LCL filtered grid-connected inverter (GCI) owing to lossless damping and efficient system design. In capacitor voltage (CV) damping methods, a differential compensator is essentially needed in feedback path where the damping effectiveness depends on emulated derivative characteristics of the compensator. Such capacitor voltage feedback compensation (CVFC) methods face design limitation at the critical resonance frequency and may require additional delay reduction to ensure stability. In this paper, an alternative parallel feedforward compensation (PFC) method is proposed to synthesize an almost strictly positive real (ASPR) plant and achieved damping with modified stability characteristics. A second-order bandpass section (BPS) employed as a compensator in damping loop based on the proposed control scheme. The main features of the proposed method are effective damping without critical resonance frequency damping limit, extended stable damping region, improved control performance and good robustness under filter parameters and grid inductance variation conditions. The simulation and experimental results are presented to verify the effectiveness of the proposed method.

Wireless power transfer charging of modern electric vehicles is complicated by widely varying charging battery pack voltages between different models. This article proposes a new resonant inductor integrated-transformer (RIIT)-based receiver. It is compact, low cost, and can adapt to different battery pack voltages without any significant change of resonant parameters. The design approach, power losses, and power transfer capacity of the proposed system are presented. In addition, methods of natural current sharing and voltage sharing among different RIITs are proposed. An LCC-LCC WPT prototype compatible with both 400 and 800-V battery pack voltages is built, and the system efficiency reaches 94% at 9.5 kW, which verifies the feasibility and performance of the proposed receiver.

Conventional high-power wireless power transfer (WPT) systems that are required to deliver power over a wide operating range suffer from issues like hard switching, poor current sharing, and unwanted cross-coupling issues. This article proposes a new resonant inductor integrated-transformer-based multi-inverter to improve the WPT power rating without compromising performance. Viable modulation schemes of the proposed system are analyzed, and a hybrid modulation scheme is proposed for wide-range power regulation. To further investigate the feasibility of the proposed system, the power transfer capacity, current sharing among multiple inverters, and the soft switching regions are studied. A 14-kW LCC – LCC WPT experimental system with three parallel inverters is built, which achieves 93.5% efficiency, demonstrating the high performance of the proposed system. This article is accompanied by a video demonstrating these experiments.

Electric vehicles with different output power levels can use wireless power transfer (WPT) systems. Different vehicle assemblies (VAs) may be charged by different ground assemblies (GAs) in charging stations. However, the overall efficiency of the WPT system may drop significantly when the power class difference between GA and VA is large. To address this issue this article proposes a dc-link parallel ac-link series multi-inverter multirectifier architecture for high-power WPT systems. Modulation, power transfer capability, and power sharing from the design aspects are investigated. A detailed power loss analysis and an easy-to-implemented power loss optimized control method based on mutual inductance identification are presented in this article. Finally, experimental results are obtained from a 20-kW LCC-LCC WPT system to validate the analysis and proposed system operation.

The dynamics of current controller is usually neglected for simplification when assessing microgrid transient stability. Utilizing the Takagi-Sugeno method, this letter thoroughly examines the effects of current controller on transient stability estimations and reveals that completely ignoring the dynamics of current controller can cause overestimation on transient stability. The findings highlight a significant overestimation on lower boundary of angle about 29.2% even if current controller performs fast dynamics with bandwidth more than 28 times the fundamental frequency. Recognizing the impracticality of including current controller dynamics in microgrids with multiple converters, the letter proposes a stability-enhanced method through phase compensation in the current controller, which can improve the accuracy of transient stability assessments while still omitting current controller dynamics. Additionally, a guideline for parameter design of phase compensation is provided. Theoretical findings are verified by hardware-in-loop experimental results based on OPAL-RT platform.

Improvements in control of renewable energy-based microgrids are a growing area of interest. A hierarchical control structure is popularly implemented to regulate key parameters such as power sharing between generation sources, system frequency and node voltages. A distributed control infrastructure is realized by means of a communication network that spans the micro-distribution grid. Measured and estimated values, as well as corrective signals are transmitted across this network to effect required system regulation. However, intermittent latencies and failures of component communication links may result in power imbalances between generation sources, deviations in node voltages and system frequency. This paper proposes a hierarchical control structure to regulate the operation of an islanded AC microgrid experiencing communication link failures. The proposed strategy aims to virtually sub-divide the microgrid into controllable “islands”. Thereafter, active power sharing, frequency and voltage restoration is achieved by competing converter systems through multi-agent consensus. The effectiveness of the proposed methodology has been verified through stability analyses using system wide mathematical small signal models and case study simulations in MATLAB, Simpower systems.