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This letter proposes a switched capacitor (SC)-based continuously adjustable modular bidirectional dc–dc converter. The structure of the proposed converter consists of three types of modules, series–parallel SC converter module, regulating module, and resonant SC converters module. A basic configuration of three modules working in buck operating mode is analyzed in detail. The boost mode operation is symmetrical to the buck mode. The regulation module provides all regulation capability, and the other two modules operate at fixed duty cycle and provide the main conversion ratio. A prototype of the basic configuration was built to verify the theory. The peak efficiency of the prototype is 97.15%. [ABSTRACT FROM AUTHOR]

In meshed high-voltage direct current (HVdc) grid, the current flows through the lines cannot be controlled with sufficient freedom without additional power electronics-based devices, namely current flow controller (CFC). In this article, a novel hybrid modular interline CFC is proposed based on H-bridge submodules and thyristor valves. Due to its modularity, the proposed CFC is particularly suitable for applications requiring high voltage and large power capacity. The circuit structure, operation principle, and parameter design are presented. In addition, a control strategy is developed for the proposed CFC. Simulations are carried out using a four-terminal meshed HVdc grid to verify the effectiveness of the topology and its control strategy. A downscaled prototype is built, which further validates the proposed CFC. [ABSTRACT FROM AUTHOR]

Modular multilevel converter (MMC) is regarded as an emerging topology in medium-voltage (MV) variable-speed motor drive applications, particularly for driving fan-/pump-like loads. The main challenge is the large capacitor voltage ripple of MMC at low speed with high starting torque. In this brief, a simple and cost-effective modified MMC topology is introduced, which can provide high toque to motor during the zero/low frequency. The topology is particularly suitable for fan-/pump-like loads. Circuit structure and operation principle of this modified topology is explained, and the control schemes are also developed. Validity and effectiveness of this topology are verified by experimental results. [ABSTRACT FROM AUTHOR]

Medium-voltage (MV) dc collection system is a promising solution for future integration of large-scale renewables at remote places. This requires a high-power dc–dc converter to step up the voltage and connect with the high voltage direct current transmission line. In this article, a novel modular high-power dc–dc converter is proposed, with the combination of half-bridge and full-bridge submodules (SMs), as well as thyristors and diodes. It alternatively configures the SMs into parallel connection with the MV side to effectively share high current stress while series connection with the high voltage side to share the high voltage stress. It presents attractive features such as high device utilization rate, low cost, high step-up ratio, high efficiency, and small footprint. The circuit structure, operation principle, and the control schemes are discussed. Simulation results demonstrate the effectiveness, and the experimental results from a scaled down prototype further prove the proposed concept. [ABSTRACT FROM AUTHOR]

Bipolar LVdc distribution is a promising solution for better integration of renewables and enhancement of system efficiency and reliability, but it also faces the challenge of pole voltage imbalance. By simple modifications of the bidirectional CLLC dc/dc converter, this article presents a dc/dc converter with integrated pole voltage balance capability. The converter presents less number of semiconductors, smaller overall footprint, and lower power loss compared to the employment of additional pole voltage balancers. Operating principle of this dc/dc converter and its inherent pole voltage balancing capability are explained, while further control scheme is also developed to compensate the small pole voltage difference caused by the dead time effect. Simulation results with 150 kW/±375 V bipolar output demonstrate the effectiveness of the converter, and the experimental results from a 500 W/±50 V downscaled prototype further prove the proposed concept. [ABSTRACT FROM AUTHOR]

Inductive power transfer (IPT) systems designed with conventional methods offer optimum performance only at specific operational points. These methods are not applicable for dynamic IPT systems where both the coupling and load change throughout the operation. This study proposes a novel particle swarm optimization (PSO)-based parameter design method and aims to obtain a steady output voltage regardless of the coupling and load. The proposed method addresses the constraints of the conventional methods where the compensation capacitors/inductors are designed to resonate with certain other inductors/capacitors at the system's operational frequency. The S/CLC (primary series, secondary capacitor–inductor–capacitor) compensation topology is chosen in this research as it offers many appealing characteristics. The procedure to design an IPT system using the proposed method is presented. Two IPT systems, one designed with the proposed scheme and the other using conventional methods, are theoretically and experimentally compared in terms of fitness, voltage variation ripple (VVR), and power transfer efficiency (PTE). It is demonstrated that the fitness and the VVR of the conventional system are 1400.8% and 372.3% higher than those of the proposed system. [ABSTRACT FROM AUTHOR]

The requirement of a large number of sizeable capacitors in traditional modular multilevel converter (MMC) submodules is seen as a major barrier hampering its widespread use in medium-voltage applications. To reduce the value of capacitance, this paper presents a modified MMC (M-MMC) topology, which offers inherent alleviated capacitor voltage fluctuations compared with traditional MMC. Its operating principle, modulation, and capacitor voltage balancing strategies are described in detail. Moreover, a novel capacitor voltage fluctuation suppression scheme is also proposed to further reduce the second-order capacitor voltage ripples. Finally, both a three-phase prototype of M-MMC and traditional MMC have been built in the laboratory. The effectiveness of the proposed M-MMC topology and control methods is experimentally verified by comparing with the traditional MMC. [ABSTRACT FROM PUBLISHER]

Parallel operation is an effective way to improve the capacity of full power converter in permanent-magnet direct-drive wind power generation system. But it causes the zero-sequence circulating-current (ZSCC), which brings current discrepancy, current waveform distortion, power losses, and electromagnetic interference (EMI), etc. The paper proposes a new topology of full power converters which are composed of n full power converters. The n converters have the same structures and are in parallel with each other. Besides, the average models of the system are analyzed and the fundamental mechanism of ZSCC generation is given. Based on the above analysis, the control strategy of the system is designed. The simulation and experiment results of two parallel full power converters show the feasibility of the proposed theory and control scheme. [ABSTRACT FROM PUBLISHER]