高可靠性双端级联式多电平逆变器单母线并联技术研究

The drive technology of open-end winding fed by dual-inverter is a very significant part in high voltage and high power drive system. Against the applications which need high reliability and high power density, some researches should be conducted around the common dc-link structure inverter’s fault tolerant control, zero sequence current and the the remaining problems after reducing it, such that it will make the neutral point potential drift, decreases modulation range and it will be hard to compensate the dead time, and so on. So the detailed research content should include that:①Analyze the causes of zero sequence current and influence factor, and build the model of it. Then design the reducing strategies. All of these will be helpful to design the theory of control algorithm. ②From the whole system, research the inner link among reducing the zero sequence current, the neutral point potential, the dead time and modulation range. Then analyze the different effects between using different reducing strategies. After that, the value function of multi-objective optimization will be decided, and it will take the best control strategies under single inverter system. ③After analyze the fault feature of the inverter system, it will be useful to increasing the reliability of dual-inverter system,by establishing the vector choosing rules in condition of fault running. It also can take more fault feature into consideration. Research results of this project can provide important theoretical basis, and make contributions to promoting the developing of large electric drive system and high power drive field.

开绕组双端级联式驱动技术是高压大功率驱动系统的一项重要研究内容。针对高可靠性、高功率密度的应用场合，围绕逆变器单母线并联容错控制、零序环流以及环流抑制后产生的中点电位漂移、调制范围下降、死区补偿困难等共性基础问题展开研究，包括：①研究零序环流的产生机理和影响因素，建立零序环流模型，制定抑制策略，为控制算法设计提供理论支持；②从系统整体角度，研究环流抑制与中点电位、死区以及调制范围的内在联系，分析不同抑制策略对系统特性的影响，以此为基础建立多目标优化的价值函数，进而提出单母线逆变器系统最优化控制策略；③分析故障特征，构造复杂故障条件下矢量选择规则，研究多故障容错控制技术，实现双端级联式系统的高效稳定运行。本项目的研究成果能够为双端级联式多电平逆变器单母线并联运行提供重要的理论依据，推动大型电力拖动系统，全电舰船等大功率电力驱动领域的发展。

开绕组电机独特的双逆变器并联驱动结构能够有效提高输出电压等级和电能质量，其冗余开关状态多，两侧逆变器独立控制和绕组单独供电等特性加强了系统的容错能力。本项目围绕单母线并联系统的性能、效率和可靠性展开研究，包括：（1）建立双逆变器系统数学模型、改进离散模型，针对预测模型误差和系统延时等固有问题，加入反馈校正和延时补偿；（2）针对零序电流抑制、中点电位平衡、电压越级跳变、死区补偿、低开关频率等共性问题，提出一种多目标优化协同模型预测控制，在对电机整体控制的基础上实现其它控制目标；（3）提出一种基于零序电流抑制的有限开关序列模型预测电流控制策略，降低计算量，减小纹波幅度之间的误差，同时解决传统模型预测算法开关频率不固定的问题；（4）研究权重因子整定复杂问题，提出一种无权重因子模型预测控制方法，保证控制目标的同时实现无权重因子模型预测控制，算法中引入虚拟理想电压矢量概念，通过在线寻优过程追踪虚拟理想电压矢量，简化迭代过程；（5）提出一种模型预测准无差拍容错控制策略，针对单管、桥臂开路故障进行控制，根据负载电流响应的畸变程度分布不均匀的特性，提出一种优化边界圆控制方法减少线计算量。（6）为实现容错控制的同时保证其他控制目标，基于Heun预测校正方案修正系统离散模型，提出一种满意优化模型预测控制策略，根据不同控制目标的重要性差异分层设计，解决故障下权重系数难以整定与协调的问题，针对控制过程中出现优化无解的情况提出了相应的改进方案。通过本项目的研究，为双逆变器系统的控制与应用提供了基础理论和方案指导。