This paper presents a flying-capacitor modular multilevel converter (FC-MMC) based on series-connected submodules. It is intended for completely improving the performance of medium-voltage motor drive system in entire speed range especially at zero/low under rated torque condition. The proposed FC-MMC circuit characterized by cross connection upper and lower arm middle taps through flying capacitor per phase leg. By properly controlling ac current flowing capacitor, power balance between...

This paper presents a transformerless static synchronous compensator (STATCOM) system based on hybrid multilevel H-bridge converter with delta configuration. STATCOM is characterized by per-phase series connection of high-voltage operating at fundamental frequency and low-voltage 5 kHz without any other circuit for dc voltage control. A new control strategy proposed in this focus regulation. Clustered balancing realized injecting zero-sequence current to the delta-loop, while individual...

This paper presents a three-phase transformerless structure of modular multilevel converters based on cascaded pulsewidth-modulated chopper cells in medium-voltage D-STATCOM application. It is suggested for installation unbalanced power-supply systems to achieve higher performance improving power quality. proposes new control strategy power-flow analysis with focus dc capacitor voltage that insulated from the source fault. enables system compensate nonlinear load even under asymmetrical grid...

This paper presents an active cross-connected modular multilevel converter (AC-MMC) based on series-connected half-bridge modules. It is intended for completely enhancing the performance of a medium-voltage motor drive system in full speed range from standstill to rated under all load conditions. The proposed AC-MMC circuit characterized by cross connection upper and lower arm middle taps through branch converters, which have identical voltage current rating with submodules arms. provides...

This paper proposes a novel modular multilevel dc-dc converter intended for transforming dc voltage and interconnecting grids medium-voltage networks. The is composed by two strings of submodules, each which consists an upper arm lower with their middle points crossly connected through capacitor. With assistant the cross-connected capacitors, ac power loops are formed converter, leading to balance between primary secondary sides, as well arms. avoidance transformer brings favorable features...

This paper presents a novel modulation and capacitor voltage control method for the modular multilevel converter (MMC) allowing fixed switching frequency of 50 Hz. In proposed method, angles are calculated through new approach with reference to nearest level control. And then, every four pulse patterns grouped together averaging dc fundamental ac components in output individual submodules. Accordingly, absorbed power each submodule could be self-balanced during few line periods simply by...

This paper presents a transformerless bipolar dc- dc converter based on series-connected submodules. It is intended for transforming voltage and managing power flow medium/high-voltage grids. The dc-dc composed of positive-pole negative-pole subsystems, each which consists six arms/branches. Every two arms one branch are constructed into T-type circuit with the outer terminals interface to primary- secondary-side buses. circuits in subsystem connected parallel transmit between primary...

The flying-capacitor modular multilevel converter (FC-MMC) overcomes the low/zero-speed operation issues of conventional MMC-based drive. FC-MMC injects no common-mode voltage (CMV) to drive system. However, pulse width modulator (PWM) introduces switching ripples, which appear as CMV on motor stator windings. To completely get rid CMV, an elimination method based a new modulation scheme is proposed in this paper. algorithm places pulses end for upper and lower arms, respectively. consistent...

Multiple insulated gate bipolar transistor (IGBT) open-circuit faults severely affect the reliable operation of modular multilevel converters (MMCs). The existing literatures have not provided an effective diagnosis algorithm for MMCs when multiple IGBT simultaneously appear in one arm. This article presents a strategy to handle that condition. Fault detection and estimation faulty submodule (SM) number is implemented by checking value arm voltage error. SMs are located observing transition...

This paper describes a three-phase trasformerless active filter system based on hybrid cascaded H-bridge converters with delta configuration. It is intended for dynamically compensating harmonic current of nonlinear load. characterized by per-phase series connection high-voltage converter operating at 50 Hz and low-voltage 7.5 kHz. DC-link voltages all are regulated purely control algorithm without any auxiliary circuit. The dc voltage ratio 2:1 realized the series-connected injecting...

A simple and cost-effective precharge method for modular multilevel converter (MMC) by using a low-voltage direct current (dc) source is proposed in this paper. The submodule (SM) capacitors MMC are required to be precharged their nominal voltage values at start-up ensure work normally. Conventional methods perform the precharging either through grid side or dc costly high-voltage bypass breakers, charging resistors source. Voltage of must equal SM capacitor could as high thousands volts. By...

This paper proposes a star-channel modular multilevel converter (MMC). It overcomes the zero/low-fundamental-frequency operation issues of conventional MMC while not injecting common-mode voltage (CMV). The proposed is characterized by cross connections upper three arms and lower through two sets branches. These branches rebalance power among phase legs, resulting in minimized submodule capacitor ripples even at without CMV injection. feature enables to interface medium/high-voltage DC...

Delta-channel modular multilevel converter (MMC) proved successful for zero/low-fundamental-frequency operation without injecting common-mode voltage. However, its application in a medium-voltage variable-speed motor drive is not verified. This paper develops system based on delta-channel MMC. The power losses together with the compensation strategies are analyzed, and accordingly submodule capacitor voltage controls elaborated. cascaded advanced control form entire scheme system....

Three-phase LLC converters show considerable potential in battery chargers. However, existing parameter design methods for three-phase have limitation analytical accuracy and efficiency optimization over the wide voltage range. To address above issues, this article proposes a time-domain model (TDM)-based method Firstly, comprehensive TDM converter is developed, providing detailed analysis of operating modes mode distributions across entire Then, based on TDM, novel proposed to optimize...

Transformerless modular multilevel converter (MMC)-based drive system usually installs a grid-tied MMC to interface with medium-voltage ac utility. Since no frontend transformer is installed, the expected directly defense common-mode voltage (CMV) from asymmetrical grid fault and switching operation of converters for maximally protecting motor. This paper presents control strategy minimize CMV MMC. The due canceled by counterpart voltage, while ripples caused are reduced arranging...

This article proposes a high-efficiency isolated dc–dc–ac three-port converter (TPC) intended for residential photovoltaic-battery systems. The TPC is derived from dual active bridge based dc–ac converter. Its dc-side provides two bidirectional dc ports by sharing the full-bridge topology, while its ac-side enables direct ac-load connection via unique T-type half-bridge structure. Due to shared branches and proposed has few components but offers single-stage power conversion substantial...

This paper presents a transformerless high-voltage dc-dc converter based on cascaded sub-modules. It is intended for interconnecting or medium-voltage dc grids. The proposed consists of two phase legs, each which an upper arm and lower with their middle nodes crossly connected through branch active By properly controlling the output voltage cross-connected branch, trapezoidal ac current induced to interact components in rebalancing power amongst arms. features modular design, single-stage...

This paper proposes a transformerless bipolar multistring dc-dc converter based on series-connected submodules. It is intended for converting dc voltage and managing power flow medium-voltage high-power networks. new has flexible structure of multistrings each string consists four valves with their middle points crossly connected through two cost-effect capacitors to form balancing channels between valves. Its solution single-stage configuration greatly reduce the volume, weight, cost, loss....

The flying-capacitor modular multilevel converter (FC-MMC) overcomes the low-/zero-speed operation issue of conventional MMC in medium-voltage motor drive application. However, introduced flying capacitor (FC) each phase leg brings great difficulties for circuit startup: 1) precharging FC to nominal voltage is necessary normal operation; and 2) oscillation between inner buffer inductors need be mitigated process. In this paper, a startup method with simple control algorithm proposed solving...