【作者】 白志红；

【导师】 张仲超；

【作者基本信息】 浙江大学 ， 电气工程， 2008， 博士

【摘要】 多电平变流器具有功率容量大、开关频率低、输出谐波小以及电磁兼容性好等特点,使得变流器装置在增大容量的同时改善其输出性能成为可能。随着超导储能技术的不断发展以及高反向电压阻断能力半导体器件(如MCT、IGCT等)的相继出现,电流型变流器的效率问题将得以解决,这为电流型多电平变流器在某些大电流高功率场合的应用提供了优势。本文首先研究了电流型多电平变流器的一些相关理论,如拓扑构造方法、PWM调制技术等;在此基础上,本文以三相电流型多电平整流器的应用研究为目标,对三相电流型多电平整流器的工作特性、参数设计以及控制方法等进行了深入研究,并取得了以下一些成果。本文提出了基于基本电路单元的电流型多电平变流器拓扑的构造方法。采用本文所提出的拓扑构造方法不仅推导出了已有的一些电流型多电平变流器拓扑,还构造出了一些新型拓扑结构。在此基础上,本文分析了电压型多电子变流器与电流型多电平变流器的“内在”对偶关系,揭示了通过借鉴电压型多电平变流器的研究成果来研究电流型多电平变流器的一些方法。本文提出了三相电流型变流器的间接调制技术和直接调制技术。间接调制技术是将二逻辑信号到三逻辑信号的变換关系作为通过三相电压型变流器调制策略来构造三相电流型变流器调制策略的一种通用实现手段。直接调制技术是基于三相电流型变流器本身的开关工作机理而提出的。与间接调制技术相比,直接调制技术具有线性传输特性、开关次数少、直流电流利用率高等优点。另外,本文还提出了一种低电压应力直接调制技术,实现了变流器的非零矢量所在相之间的自然换相。本文建立了三相电流型多电平整流器的低频数学模型和高频数学模型,详细分析了三相电流型多电子整流器的频域特性。在此基础上,从整流器的工作性能、电路参数以及系统成本等方面对三相电流型多电平整流器和三相多重化相控整流器进行了比较。分析结果表明,三相电流型多电平整流器的多项性能指标要优于多重化相控整流器,因此本文提出了在今后工业应用领域中,采用三相电流型多电平整流器来取代多重化相控整流器的设想。基于频域特性分析结果,本文提出了一种三相电流型多电平整流器直流侧滤波参数的设计方法。该方法将多模块并联整流器的直流侧等效电路等效为多个单模块整流器直流侧等效电路的并联,因此当三相电流型多电平整流器恒流输出时,直流侧体现为一阶系统,可以根据直流电流纹波指标要求和系统动态响应要求对分流电感参数进行设计。当三相电流型多电平整流器恒压输出时,可以参照Buck电路原理来设计其直流侧分流电感参数和滤波电容参数。本文研究了三相电流型多电平整流器的控制方法。首先研究了基于直接电流控制的双闭环控制方法在三相电流型多电平整流器中的应用。然后,针对三相电流型多电平整流器恒压输出情况,提出了采用负载电流前馈控制的双闭环控制策略,解决了开环幅值增益尖峰和系统快速性之间的矛盾,使得系统即便采用较小的回路增益,仍可具有较快的动态响应和较好的稳态性能。最后,基于DSP和FPGA硬件平台,设计了三相电流型多电乎整流器的全数字化控制系统。在此基础上,分别对三相电流型多电平整流器在恒流输出和恒压输出时的工作情况进行了实验,验证了本文所述理论的正确性。更多还原

【Abstract】 Multilevel converters can offer many benefits such as increased power ratings, low switching frequency,reduced output harmonics and good electromagnetic compatibility(EMC),which will make it possible to enlarge the power rating and improve the output performance simultaneously.With the development of Superconducting Magnetic Energy Storage(SMES) and the semiconductor devices with high blocking voltages(such as MCT and IGCT),the efficiency of Current Source Converters(CSCs) will be overcome,and hence their use is becoming attractive in high power applications.In this dissertation,some theories about the topology conformation and Pulse Width Modulation(PWM) methods of Multilevel Current Source Converters(MCSCs) have been studied.As an application example of MCSC,operation characteristics,parameters design and control strategies of a three-phase Multilevel Current Source Rectifier(MCSR) have also been developed. The following research works have been achieved.This dissertation explores the issue of constructing MCSC topologies using the duality principle.Three circuit cells for MCSCs are derived from the applications of the duality on the three common leg circuit cells of Multilevel Voltage Source Converters(MVSCs).Based on the presented three cells,some new or given MCSC topologies are constructed.Analytical results show that these derived MCSCs and their corresponding MVSCs present analogous features such as the ac side currents/ voltages and inductor/capacitor currents/voltages,though they are not direct dual structures.Based on this understanding,the research on MCSCs and MVSCs can refer to each other.The PWM methods for three-phase CSCs are also investigated in this dissertation. The indirect PWM method is proposed,which states that some modulation strategies of three-phase MCSCs can be got from those used for three-phase MVSCs by transforming the bi-logic signals to the tri-logic signals.Besides,based on the built-in mechanism of three-phase CSCs,the direct PWM method is also proposed.Compared to the indirect modulation,the direct PWM method has many advantages such as the linear transmission,less switch times and higher-usage of the dc current,etc.In addition,a novel low voltage-stress direct PWM method is developed to lower the voltage stress on the switches of three-phase CSCs.Low frequency and high frequency time space mathematical model of three-phase MCSR have been founded,and the characteristics of the three-phase MCSR in frequency space have been analyzed in detail.Based on analytical results, some comparisons between the three-phase MCSR and the multi-pulses thyristor phase-controlled rectifier are carried out from the characteristics,circuit parameters and cost,etc.Then,it is proposed to substitute the three-phase MCSR for the multi-pulses thyristor phase-controlled rectifier because of many superior features of the three-phase MCSR.According to the analytical results of characteristics of the three-phase MCSR, a circuit parameter design method for the dc-side filter inductor/capacitor is proposed. The dc-side equivalent circuit of MCSR can be looked on as the parallel connections of multiple dc-side equivalent circuits of a three-phase Current Source Rectifier (CSR),so for the constant dc current output,the dc-side circuit is a first-order system and the dc inductor can be designed according to the dc current ripple index and the dynamic response index.For the constant dc voltage output,the dc-side circuit is a second-order system and the design of dc filter inductor/capacitor can refer to those of the buck converter.After designing the MCSR parameters,in this dissertation we investigate the direct current double-loop control for the three-phase MCSR.For the constant dc voltage output,the problem of low bandwidth and gain,resulted from the LC-filter resonance frequency by the direct current double-loop control,makes the dc-side dynamic response bad.The load current forward feedback control strategy is proposed to solve the conflict between the fast dynamic response and the LC-filter resonance peak,and even adopting the less loop gain,the system can have a fast dynamic response and good steady state performance.Finally,a fully digital control system using cartier phase-shifted SPWM is built up based on DSP and FPGA hardware platform.The experiment on a three-module three-phase MCSR is carried out to test the operation performance when outputting the constant dc voltage/current and the experimental results verify the above proposition.更多还原