Continuous Space Vector Modulation for Symmetrical Six-Phase Drives
Continuous Space Vector Modulation for Symmetrical Six-Phase Drives
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DOI：
10.1109/tpel.2015.2456234
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发表时间：
2016-05
影响因子：
6.7
通讯作者：
Daniel Glose;R. Kennel
中科院分区：
文献类型：
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作者：
Daniel Glose;R. Kennel
六相驱动的两个常见的三桥臂两电平电压型逆变器能够产生不同的开关状态，可以表示为两个正交子空间中的电压空间矢量。逆变器桥臂的离散输出电压通常通过空间矢量调制(SVM)技术来控制，其目的是在一定的时间框架(开关周期)内产生与两个子空间中的连续参考电压矢量相同的伏秒。利用电压源和漏感的各子空间中电机的简化相位模型，发现电机的相电流呈现出不需要的失真谐波。为了减少这些谐波，必须应用适当的电压矢量序列。通过允许每个逆变器支路在开关周期(连续调制)期间改变其输出两次，可以生成518400个不同的空间矢量序列。本文证明，在这些序列中，只需要考虑11个序列来调制参考向量。进一步的仿真表明，对于某一对参考矢量和漏感比，只有一对参考矢量和漏感比将失真减小到最小。然而，由于计算量很大，这个优化问题不能在线求解。为了克服这一缺点，从离线优化的四种不同的调制策略--标准三相支持向量机、分段扇区映射、最优交织和近似交织支持向量机--进行了推导和比较。根据所产生的电流失真和参考矢量以及电感比的影响来评估每种策略。对这几种在线调制策略的谐波电流进行了仿真计算和实验验证。应用所提出的调制技术可以极大地减少由开关引起的电机损耗。
The two common three-leg, two-level voltage source inverters of a six-phase drive are able to produce 64 different switching states, representable as voltage space vectors in two orthogonal subspaces. The discrete output voltage of the inverter legs is usually controlled by means of a space vector modulation (SVM) technique, the aim of which is to produce the same volt-seconds as the continuous reference voltage vectors in both subspaces within a certain time frame (switching cycle). Using a simplified phase model of the machine consisting in each subspace of a voltage source and a leakage inductance, the phase currents are found to exhibit unwanted distortion harmonics. A proper sequence of voltage vectors has to be applied in order to reduce these harmonics. By allowing each inverter leg to change its output twice during the switching cycle (continuous modulation), 518400 different space vector sequences can be generated. This paper demonstrates that, among these sequences, only 11 need to be considered to modulate the reference vectors. Further simulation shows that, for a certain pair of reference vectors and leakage inductance ratio, only one of them reduces the distortion to a minimum. Due to the high computational effort, however, this optimization problem is not solvable online. To overcome this drawback, four different modulation strategies, the standard three-phase SVM, the fragmented sector mapping, the optimal interleaved and the approximated interleaved SVM, are derived from and compared with an offline optimization. Each strategy is evaluated regarding the resulting current distortion and the influence of the reference vectors as well as the inductance ratio. The harmonic current of these online modulation strategies is calculated in simulation and validated by experiments. Applying the proposed modulation techniques leads to a great reduction in the machine losses caused by switching.