DC-Link Capacitor Voltage Balancing Control of a Five-Level Regenerative AC Electronic Load Using One-Cycle Control

High voltage electric power equipment requires rigorous regulation testing to specific standards which ensure proper and safe operation in the grid. Manufacturers conduct these tests in order to prove standard compliance and product liability. Variable linear or nonlinear loads are necessary for testing medium voltage (MV) high power AC power converters. Generally, those AC power converters or power supplies require performance validation, burn-in and/or lifetime testing under different load conditions, defined by the end-user or standards for the given applications. For flexible and efficient MV verification testing, this paper presents a five-level multilevel converter-based MV regenerative AC electronic load with one-cycle control (OCC), which is based on five-level diode-clamped multilevel converters with back-to-back structure and can emulate any impedance load. In this paper, especially the dc-link capacitor voltage balance of the proposed multilevel MV regenerative AC load is deeply analyzed. Simulation and experimental results are presented to verify the dc-link voltage balance performance of the proposed multilevel MV regenerative AC electronic load.

Analysis of Capacitor Voltage Imbalance in Hybrid Converters and Inherently Balanced Operation Using Symmetric Architecture

<p>This paper investigates the origin of the flying capacitor voltage imbalance in hybrid converters. By observation and logical deduction, an intuitive voltage-charge relationship is established which can give a general explanation of the flying capacitor voltage balance in hybrid converters. This relationship can establish a relatively simple and intuitive method to identify the difference of balance performance in hybrid converters for Vout<(V_in /N) cases. Converter with even number of inductor charging intervals, are shown to be susceptible to flying capacitor voltage imbalance, while flying capacitors in hybrid converters with inductors having odd charging intervals have inherently balanced operations. As a direct result of the analysis, a new symmetric operation of FCML converters is introduced to achieve an inherent balance of flying capacitor voltages. Hardware implementations and experiments have been carried out for verifications of the analytical analysis and the new symmetric operation.</p>

Analysis of Capacitor Voltage Imbalance in Hybrid Converters and Inherently Balanced Operation Using Symmetric Architecture

<p>This paper investigates the origin of the flying capacitor voltage imbalance in hybrid converters. By observation and logical deduction, an intuitive voltage-charge relationship is established which can give a general explanation of the flying capacitor voltage balance in hybrid converters. This relationship can establish a relatively simple and intuitive method to identify the difference of balance performance in hybrid converters for Vout<(V_in /N) cases. Converter with even number of inductor charging intervals, are shown to be susceptible to flying capacitor voltage imbalance, while flying capacitors in hybrid converters with inductors having odd charging intervals have inherently balanced operations. As a direct result of the analysis, a new symmetric operation of FCML converters is introduced to achieve an inherent balance of flying capacitor voltages. Hardware implementations and experiments have been carried out for verifications of the analytical analysis and the new symmetric operation.</p>

Enhanced Boost Factor for Three-Level Quasi-Switched Boost T-Type Inverter

A new modulation strategy has been introduced in this paper in order to enhance the boost factor for the three-level quasi-switched boost T-type inverter (3L-qSBT2I). Under this approach, the component rating of power devices is significantly decreased. Moreover, the use of a larger boost factor produces a smaller shoot-through current. This benefit leads to reducing the conduction loss significantly. Furthermore, the neutral voltage unbalance is also considered. The duty cycle of two active switches of a quasi-switched boost (qSB) network is redetermined based on actual capacitor voltages to recovery balance condition. Noted that the boost factor will not be affected by the proposed capacitor voltage balance strategy. The proposed method is taken into account to be compared with other previous studies. The operation principle and overall control strategy for this configuration are also detailed. The simulation and experiment are implemented with the help of PSIM software and laboratory prototype to demonstrate the accuracy of this strategy.

A New MMC Sub-Module Topology with DC Fault Blocking Capability and Capacitor Voltage Self-Balancing Capability

A large number of modular multilevel converters (MMC) are connected to HVDC transmission systems nowadays. This paper aims at the short-circuit fault in the DC line of the HVDC transmission system and the problem of capacitor voltage imbalance in MMC, proposing a new type of MMC sub-module, which has both the DC fault self-clearing ability and the capacitor voltage self-balancing ability. This sub-module combines the topology of half bridge and full bridge. It uses the reverse capacitor voltage to forcibly turn off the conducting diode to block the fault current loop. At the same time, the two capacitances charge and discharge states are consistent by utilizing the operating mode of the sub-module. It is possible to directly achieve a self-balancing capacitor voltage without complex balancing voltage control. The MATLAB/Simulink simulation verifies the effectiveness of the DC fault blocking capability and capacitor voltage balance capability of the proposed sub-module.

Design and implementation of a single-phase five-level inverter using a DC Source with voltage balancer on capacitor

<span lang="EN-US">The global use of renewable energy resources has led to the design and development of high performance, efficient, controllable, and cheap multilevel inverters, which act as a solution to the numerous power deficiencies. However, in terms of control, these multilevel inverters are often associated with DC sources and complexity. Therefore, this research designed a single-phase five-level inverter using a DC source, with a novel sinusoidal pulse-width-modulated (SPWM) control scheme. The system consists of a Flying Capacitor DC-DC Converter and H-Bridge Inverter (FCDCDC-HBI). A single absolute reference signal and the phase-shifted triangular carrier were used to generate SPWM to enhance the capacitor voltage balance. The designed inverter is capable of producing five levels of output voltage levels, namely Vi, Vi/2, 0, −Vi/2, and −Vi from a DC supply, thereby reducing the overall cost and complexity of the SPWM system. This research also produced a detailed operation principle of the proposed system, which was verified through simulation and implemented using a prototype. Finally, hardware implementation results are presented to check the performance of the inverter.</span>