电力电子混杂系统多模态谐振机理及其多功能复合有源阻尼抑制技术

All power quality problems come from the interaction between power source, line and load. In general, shunt power quality conditioner is used to compensate reactive and harmonic currents. Most researches are carried out in ordinary laboratory supposing strong power supply with big enough short circuit capacity and linear/nonlinear load combination with resistor and inductor. However, the electrical environment in actual site for shunt conditioner is really complicated. For example, the equivalent internal impedance of power source is nonlinear. In addition, there are kinds of capacitive loads such as power capacitor bank for var compensation, passive power filter, distributed capacitors for EMC (electromagnetic compatibility) and voltage source type diode rectifier. All of these linear/nonlinear capacitive loads may trigger multimode resonance in power electronic hybrid system. The compensation band of the conditioner may be overlapped partly by the resonant band of the whole system, which will induce positive feedback and harmonic amplification. Therefore, the multimode resonance should be damped actively by suitable damping control strategy in time. In this proposal, by means of MMC (modular multilevel converter) setup and dynamic capacitor prototype, both parameter identification method and multimode resonance mechanism will be studied firstly in power eletronic hybrid system, while the ultimate capability of shunt active conditioner to compensate voltage source type diode rectifier will be also investigated. Consequently, three kinds of multifunction acitve damping control techniques are expected to obtain, namely harmonic virtual resistor method, harmonic current decomposition skill and harmonic energy closed-loop regulation tactics. Furthermore, taking advantage of advanced power electronics, the traditional power capacitor bank for power factor correction will be studied how to compensate reactive power, inhibit harmonic current and suppress series/parallel resonance more effectively and how to tranform itself into dynamic capacitor by use of thin AC converter.

电能质量问题由电源、线路和负载共同产生，并联型电能质量调节装置能够补偿无功和抑制谐波。大部分研究主要针对实验室典型应用环境：电源短路容量大，线性、非线性阻感型负载。但是，实际现场应用环境复杂：电源等效内部阻抗非线性，存在以无功补偿电容器组、无源电力滤波器、电磁干扰抑制电容器、电压源型非线性负载等为代表的容性负载。各种线性、非线性容性负载容易产生混杂系统多模态谐振，谐振频段可能与补偿频段部分重叠，形成正反馈导致谐波放大，必须实施适时、适式的有源阻尼控制。本项目拟搭建模块化多电平变换器和动态电容器实验样机，研究混杂系统参数辨识方法与多模态谐振产生机理，探索对电压源型非线性负载的极限补偿能力，获得分别基于谐波虚拟电阻方法、谐波电流分解技术以及谐波能量闭环调节方式的三种多功能复合有源阻尼抑制技术，以及利用电力电子技术对无功补偿电容器组进行改进形成动态电容器以提升无功补偿、谐波抑制和谐振阻尼性能。

在配电系统中，感性负载消耗无功，常用补偿电容器进行功率因数校正。非线性负载产生谐波电流，常用无源电力滤波器进行抑制。电容器、无源电力滤波器等容性元件，会与系统内部等效感性阻抗产生并联谐振，谐振频率和品质因数与结构、参数和工况有关，导致PCC点电压严重畸变，不满足电能质量标准要求，并联型电能质量调节装置不能正常完成无功补偿和谐波抑制任务，必须同时进行谐振阻尼复合控制。.本项目紧紧瞄准无功补偿、谐波抑制和谐振阻尼等电能质量控制目标，搭建了常规两电平有源电力滤波器SAPF，模块化多电平电能质量调节器MMC-SPQC，以及动态电容器D-CAP等三相有源并联型电能质量调节装置样机及其实验平台，进行了谐振机理分析、谐振频率和阻尼系数自适应检测、谐振阻尼程度闭环调节等研究。.对于SAPF，如果存在线性容性元件，系统并联谐振频率将随SAPF补偿系数不同产生漂移，通过SAPF向系统注入适当方波信号可以实时准确检测谐振频率和阻尼程度；如果电流补偿指令检测中不含电容电流，系统稳定；如果电流补偿指令检测中包含电容电流，系统不稳定；非谐振谐波电流可以正常抑制，谐振谐波电流则必须通过检测PCC电压谐振谐波构成虚拟电阻进行闭环阻尼。.对于MMC-SPQC，设计了基于多个DSP的主从式分层控制系统，解决了实时通讯和同步问题，给出了电容电压和环流计算公式，实现了电容电压均衡控制。对于MMC-DSTATCOM，实现了动态无功补偿、PCC电压下垂调节和不平衡控制；对于MMC-SAPF，采用四重采样载波移相PWM技术扩展了控制带宽，实现了低频谐波电流的有效抑制。.对于D-CAP，解决了AC/AC变换器开关器件有源缓冲问题，量化了补偿电流波形畸变的原因，发现无功补偿和谐波抑制之间存在耦合，采用偶次谐波调制PWM和协调控制技术，实现了无功补偿、谐波抑制和谐振阻尼的复合控制。.以上研究不仅为并联型电能质量调节装置的推广应用开辟了道路，而且也对串联型、混合型电能质量调节装置的实用化有较大的借鉴意义，同时对并网变换器以及电力电子化系统的稳定与控制具有一定的参考价值。