三相交错并联双向直流变换器无电流传感器均流控制

Sensorless Current Sharing Control of Three-phase Interleaved Bidirectional DC Converter

针对三相交错并联双向直流变换器均流策略中,控制环路多、电流检测电路设计复杂的缺点,基于传统单闭环电压型控制方法,提出一种无电流传感器均流控制策略。以变换器降压模式为例,根据戴维宁定理建立其等效电阻电路模型,通过分析相间电流与等效电阻、有效占空比的关系,明确了相间电流不平衡的主要原因是阻抗失配。为了消除其引起的电流不均衡,以任意一相为基准,推导出其余两相应补偿的占空比△D。同时给出了无电流传感器均流控制系统控制环路的设计方法,采用数字控制技术对控制器离散化处理,并对开关节点处占空比失配进行了补偿,避免因电流传感器精度低和设计不足对变换器的影响。仿真和在25 kW样机的实验结果表明,在各种失配与不同负载下,均流性能表现良好,稳压精度高,验证了理论分析的正确性与可行性。

Aiming at the disadvantages of overabundant control loops and complex design of current detection circuit in the current sharing process of three-phase interleaved bidirectional DC-DC converters, a current-free current sharing control strategy is proposed based on traditional voltage-type control. The converter buck mode is taken as an example, and the equivalent resistance circuit model is established according to the Thevenin theorem. The relationships between the phase-to-phase current and the equivalent resistance or the effective duty cycle are analyzed. It is clear that the cause of the phase-to-phase current imbalance is the impedance mismatch. Moreover, based on one of the phases, the other two correspondingly changed duty cycles △D are derived and compensated. At the same time, the design method of the control loop of the current-free current sharing control system is given. The digital control technology is used to discretize the controller, and the duty cycle mismatch at the switch node is compensated to avoid the effects of the low accuracy of the current sensor, and insufficient design on the converter. The simulation and experimental results in a 25 k W prototype show that the current sharing performance is superior under various mismatches and different loads, which verifies the correctness and feasibility of the theoretical analysis.