Multi-Paralleled Current Source Converters with Simple Configuration

为了简化用于超导储能、核聚变等领域的多并联电流源变流器的结构，研究了两种方法，例如1）通过仅使用Δ-Δ和Δ-Y连接以及不使用Transformer绕组的并联连接的多并联配置来减少谐波，2）串联连接变压器的初级绕组以平衡电流而不使用DC电抗器。在变换器电路方面，选择了吸收式能量回收电流型变换器，并对电路的特性进行了详细的分析。所得结果总结如下。对一次侧绕组串联均流方法进行了数字仿真验证。电流平衡是在无短路模式下进行的，在这种模式下串联连接的正、负侧器件同时导通。 关于我们 桥的平衡，其中电流不流过Transformer绕组。2. N次谐波可在不使用变压器的情况下由2台变流器的N次幂抵消。例如，11次或13次谐波电流可以由两组转换器消除，其中电流相位彼此偏移以消除谐波，11次和13次谐波电流都可以由四组转换器消除。通过使用具有Δ-Δ和Δ-Y连接的变压器，5次和7次谐波也被消除。缓冲电容器被充电，即使电容器旁边的开关器件保持关断状态。这种现象是由于其他器件开关的影响，常发生在电容值较大时。如果这种现象经常发生，施加到开关器件的电压不能相应地降低缓冲电容器的电容值的增加，和交流线路的谐波增加，由于充电电流.对于采用正弦脉宽调制（PWM）控制的缓冲式能量可回收电流源整流器，缓冲电容应设计得尽可能小，以将开关器件两端的电压上升率抑制在允许值以内。交流线路需要额外的电容器来抑制开关器件两端的电压，并吸收PWM产生的高频涟漪电流。少

In order to simplify the configuration of mutli-parallel connected current source converters used for superconducting magnetic energy storage (SMES), nuclear fusion and etc., two methods such as 1) Reduction of harmonics by multi-parallel configuration using only DELTA-DELTA and DELTA-Y connection ans without using zigzab connection of transformer windings, 2) Series connected primary windings of transformers to balance the current without DC reactors, were examined. As for the converter circuit, snubber energy recoverable current source converter was chosen, and characteristics of the circuit were also carefully examined. Obtained results are summarized as below.1. Current balancing method by series connected primary side windings was examined by digital simulation. Current balancing was performed in the operation without short-through mode in which series connected positive and negative side devices are simultaneously turned on. Operation with such short-through mode prevents current … More of bridges from balancing, in which current does not flow through transformer windings.2. N harmonics can be canceled by the N-th power of 2 sets of converters without using transformers. For example, either 11th or 13th harmonic current can be canceled by two sets of converters in which current phases are shifted each other to cancel the harmonics, both 11th and 13th harmonic current can be canceled by four sets of converters. By using transformers with DELTA-DELTA and DELTA-Y connection, 5th and 7th harmonics are also canceled.3. Snubber capacitors are charged, even if the switching devices beside the capacitor is keeping off-state. This phenomenon is due to the effect of switching of other devices and often occurs when the capacitance value is larger. If such phenomenon occurs frequently, applied voltage to switching devices can not be decreased corresponding to increase of the capacitance value of snubber capacitors, and harmonics of ac line are increased due to the charging current.4. As for application of sinusoidal Pulse Width Modulation (PWM) control to the snubber energy recoverable current source conveter, snubber capacitor should be designed as small as possible to suppress the rate of rise of voltage across switching devices within the allowed value. Additional capacitors to ac line are required to suppress the voltage across switching devices and absorb high frequency ripple current produced by PWM. Less