【作者】 杨晓萍；

【导师】 钟彦儒；

【作者基本信息】 西安理工大学 ， 电力电子与电力传动， 2009， 博士

【摘要】 配电网静止同步补偿器(Distribution Static Synchronous Compensator-DSTATCOM)因其能对系统无功功率进行双向动态补偿、抑制谐波、补偿负载不平衡等,成为现代静止无功补偿技术研究的热点之一。以往电力电子设备的设计和运行分析,通常假设运行在对称条件下,但这与实际情况不符,尤其在三相四线系统中对称的假设难于满足。因此,研究DSTATCOM及其在系统不平衡补偿中的控制策略对于提高配电网的电能质量具有十分重要的意义。本文针对配电网不平衡补偿这一课题,从理论和技术上进行了深入研究,主要研究内容及结果如下：建立了三相四线DSTATCOM的数学模型。从abc静止坐标系出发建立了三相四线三电平NPC逆变器的开关模型和平均模型,并将abc坐标下的平均模型转化为dqO坐标下的平均模型；在对直流电容引入“等值电容”概念的基础上,将交流侧和直流侧电量进行统一处理,建立了不依赖主电路结构的三相四线DSTATCOM装置的标幺值平均数学模型,并给出了等值电路。标幺值模型的引入,为进行装置的稳定性分析和装置参数评估提供了统一方法,解决了不同电压等级不同容量的统一处理问题。提出了基于参考电压分解的新型3-D多电平空间矢量PWM调制算法。针对算法中的开关矢量选择问题,提出将参考电压矢量分解成偏移矢量和3-D两电平矢量,采用3-D两电平空间矢量PWM算法来合成多电平参考电压矢量,将任意电平数目的3-D空间矢量PWM调制算法问题简化成3-D两电平空间矢量PWM调制算法问题。分析了配电网不平衡对DSTATCOM运行和控制的影响,建立了电网不平衡状态下DSTATCOM的复矢量模型和零序单变量矢量模型。研究了补偿三相负载不平衡的正、负序双同步控制器和零序同步控制器,实现了对不平衡负载负序、谐波电流的补偿及三相四线系统中线电流的控制：并提出了基于正负序分量调节的不平衡电压控制策略,解决了配电网电压的不平衡问题。分析了DSTATCOM装置自身故障及电力系统故障对装置的影响,提出了将封锁脉冲运行方式作为DSTATCOM装置处于紧急状态下的保护措施,针对NPC逆变器桥臂直通短路故障,提出了采用阳极电抗及其箝位电路限制短路电流及阻尼短路电流振荡,使短路电流在IGBT浪涌电流的承受能力内。在电力系统发生不对称故障情况下,采用对称调制方式,应对正序电流进行快速控制来抵御系统对装置的影响；采用非对称调制方式,在保证装置安全的条件下,增加对系统无功的支持能力。最后根据本文提出的DSTATCOM的控制策略,研制了基于3-D空间矢量调制三电平NPC逆变器的100kVar DSTATCOM装置。仿真实验和样机的运行试验表明,多电平3-D空间矢量PWM调制算法设计简单,计算时间少；DSTATCOM的不对称控制策略能有效实现负载不对称、谐波的补偿,减小电网的不平衡度,装置设计达到了预期目的。更多还原

【Abstract】 Distribution Static Synchronous Compensator abbreviated as DSTATCOM, is a hot subject for modern static reactive power compensation technology since it has several functions such as the bidirectional dynamic compensating to the power system, restraining harmonics, and compensating unbalanced loads. The traditional design and operational analysis of power electronic equipments were done under the balanced circumstances which were not agreeable with the practical situation, especially under the three-phase four-wire system. Therefore, study on DSTATCOM and its control technology under unbalanced system, plays an important role in the power quality improvement for distribution network. Thus, the theoretical and technological investigations on DSTATCOM were carried out aiming at solving the problem of unbalanced compensation in distribution system. The main results were summarized below.The mathematical model of three-phase four-wire DSTATCOM was established. The switch model and average model of three-phase four-wire three-level NPC inverter were formed from the abc coordinate. Then the average model in the abc coordinate was transformed into the one with dqo coordinate. Based on introducing the conception of "equivalent capacitance" to DC capacitor, the electric quantity of AC-link and DC-link were processed simultaneously. An averaged mathematical model of three-phase four-wire DSTATCOM based on per unit, independent of the main circuit topology, was established, and then the equivalent circuits were given. The introduction of per unit model provided a uniform method for the stability analysis and the parameter evaluation of the device, and solved the problems of different voltage classes and capabilities, thus made parameter comparisons easy.A new PWM modulation algorithm of three Dimensions multi-level Space Vector based on decomposing referential voltage was proposed. The method included the following steps, decomposing reference voltage into offset vector and 3-D two-level vector for the switching vector selection firstly, while introducing 3-D two-level space vector PWM algorithm to compose multi-level vector, and then reducing any numeracy level 3DSVPWM to two-level 3-D SVPWM.The effects of unbalanced distribution network on DSTATCOM operation and control were analyzed. The complex vector model and zero-sequence single-variable vector model of DSTATCOM in the unbalanced power system were established. The positive-negative sequence bisynchronous controller and zero-sequence synchronous controller were investigated to compensate the unbalanced 3-phase loads which accomplished several functions such as compensating to the negative-sequence current and the harmonics current of unbalanced loads, and controlling the null line current of 3-phase 4-line system. Meanwhile, an unbalanced voltage control strategy based on the regulation of positive and negative components, was proposed to solve the unbalanced voltage in the distribution.The own fault of DSTATCOM and the influence of power system fault on the device were analyzed, a pulse-block operation mode serving as anti-fault means under the emergency condition was proposed. To overcome the problem of the NPC inverter bridge arm, a nonstop to the short circuit breakdown was proposed using the anode reactance, the clamping circuit limit short-circuit current, and the damping short-circuit current vibration. This made the short-circuit current in IGBT surge current bearing capacity. Under the circumstance of unbalanced fault in the power system, the symmetrical modulation method carrying out fast control on the positive-sequence current was adopted to resist the impact on the device, while the unsymmetrical modulation method was used to increase the reactive power to the system under the safe condition.A 100-kVAR DSTATCOM prototype based on 3-D space vector modulation 3-lever NPC inverter was developed according to control strategies proposed in this paper. Emulation and operational experiments shown the multi-lever 3-D space vector PWM modulation algorithm had the advantages such as easy design and short calculation time. The unbalance control strategy of DSTATCOM fulfilled the compensation of unbalanced loads and harmonics, and reduced the asymmetry of the distribution networks. Therefore, the DSTATCOM achieved the expected purpose.更多还原