双线电压级联型多重化PWM变频调速系统运行控制

The line-voltage cascaded multiple PWM converter is composed of traditional three-phase two-level PWM converter by line-voltage cascaded manner. The advantages of the four-quadrant inverter constituted of the multiple converter are low harmonic component, high use-ratio of dc-link voltage. Based on the characteristics of the external circuit and the structure of the internal circuit of the variable frequency speed control system, the functional relations symbolized the characteristics of the external circuit of the multiple power converter and the constraint equations among units of the internal circuit are solved and the mapping relations are analyzed in the research. The equivalent mathematical model of the external circuit that covers all the operating messages of the units is established. The predictive control method is used in the control of the circuit loop to improve the response speed of the overall power transmission of the variable frequency speed control system. The model predictive control and the coordinating control are combined by the used of the mapping relation. Consider of the specific structure of the multiple PWM variable frequency speed control system, the coordinating operation mechanism among the component units is analyzed from the vertical and horizontal dimensions respectively, and the coordinating operation between the two dimensions is also analyzed. The design method of the control system is summarized, and the whole system will be optimized on the basis of experimental results.

线电压级联型多重化PWM功率变换器，是一种以传统三相两电平PWM变换器为基本单元，通过线电压级联方式构成的多重化变换器。由其构成的四象限变频调速系统具有谐波含量低、直流侧电压利用率高等优点。本申请课题拟从变频调速系统外电路特性和内部电路结构两个层面出发，求解表征多重化功率变换器外电路特性的函数关系与电路内部各单元间约束方程，并分析两者之间映射关系，从而建立涵盖全部组成单元运行信息的外电路等效数学模型。为提高变频调速系统整体功率传输的响应速度，将模型预测控制思想引入到电流控制环中，利用求解得到的映射关系，将模型预测控制与协调控制有机结合。针对多重化PWM变频调速系统结构的特殊性，分别从纵向与横向两个维度分析各组成单元间协调运行机制，并研究两个维度的协调控制之间配合运行方式。本申请课题将总结提炼控制系统设计方法及思路，并根据实验结果进一步优化整体系统。

本项目围绕线电压级联型多重化PWM功率变流器，从变频调速系统整体外电路特性和线电压级联型多重化PWM功率变流器内部电路结构出发，阐明了调速系统中各组成单元间交流侧电流、直流侧电容电压等物理量函数关系，揭示出形成单元间环流以及造成直流侧电容电压严重波动的主要因素，建立完备的外电路等效数学模型，为实现系统迅速而稳定的运行控制提供必要的理论基础。为降低变流器输出电压谐波含量，提高变频调速系统控制品质，从电路拓扑结构特点出发，提出了一种改进性载波移相SVPWM调制策略以及一种从重构矢量空间的角度出发的新型空间矢量调制策略，一方面实现了变流器输出线电压波形的改善，另一方面去掉了大量冗余开关状态降低了系统损耗。此外，通过对模型预测控制机理的剖析，依据对系统从整体外电路特性和内部电路结构两个层面的分析结果，将模型预测控制引入到多重化PWM变流器宏观层面控制中，并针对模型预测控制参数敏感性问题，将模型预测控制与模糊算法相结合，提出了一种抗参数扰动性强，且算法实现简单，在线运算量少，硬件需求量低的控制方法。