基于高压交流直接接入的高频隔离高效率双向AC-DC变流器研究

Based on the requirement of the large scale energy storage application, high frequency conversion is used to achieve high frequency and high efficiency conversion between high voltage AC grid and low voltage DC based energy storage device. To meet the 10kV AC grid and wide voltage gain requirement, a power circuit composed of cascaded H bridge converters connected with individual current-fed bidirectional high frequency isolated three-level DC-DC converter. For the bidirectional DC-DC converter, a double PWM dual phase shifted with fixed pulse width is proposed, with which all the switches can achieve ZVS within wide load range and the circulating loss can be suppressed. It is very easy to achieve fast closed-loop control. During the power transferring stage, the leakage inductance current can be sensed to achieve excellent current waveform control and therefore the main circuit parameter mismatch and load variation effect can be eliminated. For individual DC bus for cased H bridge converters, a unified DC bus control is proposed in spite of the power flow direction. Besides, the amplitude and frequency fluctuation of the high voltage grid can be compensated by the proposed converter and thus smart interaction can be obtained, which lays the fundamental theory and technology based for the massive application of the energy storage.

针对未来智能电网中大规模储能技术发展的要求，采用高频隔离代替传统的工频隔离，实现高压交流和低压直流储能元件之间高频隔离、高效率变换。为了适应于高压交流10kV及储能用宽电压增益要求，提出了级联H桥分别接多个电流源型双向高频隔离三电平DC-DC变换器的主电路。对于双向DC-DC，提出了基于恒定脉宽误差的双PWM双移相控制策略，采用该方法，可以在宽负载范围内功率流方向变化时实现所有开关管ZVS软开关，抑制了环流损耗。同时该方法易于实现实时闭环控制。在功率导通阶段，提出了漏感电流直接反馈控制策略，可实现最佳电流波形控制，消除了主电路参数离散型和功率实时变化的影响。为了适应储能单元和高压电网之间的双向互动，对于级联H桥直流母线控制，提出了一体化直流母线电压均衡控制策略。该变流器能够实现自动补偿交流侧电压幅值和频率的变化，使得储能单元和高压交流电压实现双向智能交互，为大规模储能应用奠定基础

针对未来智能电网中大规模储能技术发展的要求，采用高频隔离代替传统的工频隔离，实现高压交流和低压直流储能元件之间高频隔离、高效率变换。为了适应于高压交流10kV及储能用宽电压增益要求，提出了级联H桥分别接多个电流源型双向高频隔离三电平DC-DC变换器的主电路。对于电流型双向DC-DC，提出了基于恒定脉宽误差的双PWM双移相和电压非匹配下的占空比扩展控制策略，可以在宽负载范围内功率流方向变化时实现所有开关管ZVS软开关，抑制了环流损耗。对于电压型DAB，提出了临界梯形波调制策略，实现了实时闭环控制。为了进一步扩展增益，提出了基于电压匹配控制的双变压器和混合桥控制策略。对于半控型DAB，研究了电压模式和电流DAB，同时由单相扩展到三相。对于高增益DC-DC，三相逆变器，系统地研究了边界控制，以极低的代价实现了软开关。为了适应储能单元和高压电网之间的双向互动，对于级联H桥直流母线控制，提出了一体化直流母线电压均衡控制策略，能够自动适应充、放电的场合。该变流器能够实现自动补偿交流侧电压幅值和频率的变化，使得储能单元和高压交流电压实现双向智能交互，为大规模储能、特种装备的双向流等应用奠定基础。