微电网电能质量主动控制策略研究

发布时间：2018-08-13 15:27

【摘要】：为有效解决分布式电源的接入给电网带来的影响，微电网概念被提出。为保证微电网高效可靠运行，满足客户对高质量电能的需求，微电网电能质量控制技术成为微电网的关键技术之一。与配电网不同，由于微电网中多数微电源接口采用电力电子变流器，使得采用适当的控制策略实现微电网电能质量主动控制成为可能，在微电网中主要通过实现微电源接口微网变流器的复合控制，以及采用相应的控制策略提高微网变流器运行性能来实现电能质量主动控制。本文以微电网为研究对象，对微电网的电能质量主动控制，包括实现储能电源接口变流器复合电能质量补偿功能的多目标控制策略、储能电源接口双四桥臂变流器电能质量控制策略、非理想电压条件下提高微网变流器运行性能的控制策略等问题展开研究。论文首先针对微电网的网络构造、运行特点以及负荷特性，分析微电网结构及其控制方法，指出由于储能微网变流器与电能质量治理装置有相同的拓扑结构，，因此具备电能质量主动控制条件；然后分析比较现有三种微电网PQ控制策略，指出由于受到滤波电感误差或电网感抗的影响导致系统性能降低，为改善性能采用功率、电流完全解耦的微网变流器PQ控制策略；最后建立了基于PQ控制微网变流器诺顿等效电路的微电网等效模型，以此为基础深入分析微电网电压波动原因和微电网与配电网间谐波谐振交互机理。为有效抑制电压不平衡、谐波畸变干扰，采用基于自适应陷波器(Adaptive Notch Filter, ANF)的正负序分量分解方法提取电网电压基波正、负序分量，从而实现补偿电流检测和参考电流计算。为充分利用储能电源接口变流器冗余容量，实现电能质量主动补偿，研究具有微电网电能质量主动治理功能的储能微网变流器多目标控制策略。该控制策略可以使储能系统平抑微电网功率波动，同时在全补偿控制方式下实现谐波、无功和不平衡电流的全频段范围补偿，在分频选择补偿控制方式下基于比例矢量比例积分(Proportional Vector Proportional-integral, PVPI)控制还可实现对谐波、无功和不平衡电流有选择的分频进行补偿。两种多目标控制策略可以有效利用储能系统，提高微电网电能质量，减小对配电网的影响。在储能微网变流器多目标控制的基础上，为进一步解决配电网与微电网之间电能质量交互影响，对具有灵活接入方式的超级电容(Super Capacitor, SC)储能电源双四桥臂变流器(Microgrid Power Quality Controller, MGPQC)的控制策略进行研究。在串-并联接入方式下，为补偿公共连接点(Point of Common Coupling, PCC)电压跌落，根据SC的剩余容量(SC-SOC)，提出一种电压跌落协调补偿策略，通过微电源、SC和普通负荷切除之间的协调控制使得PCC电压始终维持在正常水平；在串联接入方式下，分析了电网电压不平衡、谐波畸变对MGPQC传输功率的影响，采用SC储能平抑MGPQC中间直流侧功率波动，提高微电网电能质量，避免配电网对微电网的影响。为实现变流器正、负序电流统一控制，采用多谐振PVPI控制器实现电流内环控制。上述方法提高了微电网电能质量，增强了微电网并网运行能力。为提高电网电压不平衡、谐波畸变条件下LCL滤波微网变流器的运行性能，结合电容电流反馈有源阻尼和电网电压前馈控制，提出基于PVPI控制的非理想电压条件下微电网变流器PQ控制策略，控制策略不需要锁相环和对电流进行正负序分离，计算量小，简化了系统控制结构，并可以改善微网变流器输出电能质量，提高非理想电压条件下微网变流器运行性能；针对电流闭环系统由于结构复杂、参数较多导致的系统参数设计困难，以及通过参数设计提高系统鲁棒性的设计要求，提出一种提高系统鲁棒性的简化电流闭环参数设计方法，采用频率法分析电容电流反馈系数和PVPI控制器各参数对电流环性能的影响，根据稳定性、幅值裕度和相位裕度要求，分别设计电容电流反馈系数、PVPI控制器的相对谐振增益系数和比例系数。该方法采用解析计算，简化了参数设计，提高了系统的稳定性、鲁棒性和动态响应性能。
[Abstract]:In order to ensure the efficient and reliable operation of the micro-grid and satisfy the customers'demand for high-quality power, the power quality control technology of the micro-grid has become one of the key technologies of the micro-grid. Unlike the distribution network, most of the micro-grid power interfaces are adopted. With the power electronic converter, it is possible to adopt appropriate control strategy to realize the active control of power quality in microgrid. In microgrid, the active control of power quality is realized mainly by realizing the compound control of microgrid converter with microgrid interface and adopting corresponding control strategy to improve the operation performance of microgrid converter. The active power quality control of micro-grid includes multi-objective control strategy to realize the composite power quality compensation function of energy storage power interface converter, power quality control strategy of dual-four-leg converter with energy storage power interface, and control strategy to improve the performance of micro-grid converter under non-ideal voltage conditions. The problem is studied.
Firstly, according to the network structure, operation characteristics and load characteristics of micro-grid, the structure and control method of micro-grid are analyzed. It is pointed out that the converter of energy storage micro-grid has the same topology structure as the power quality control device, so it has the conditions of active power quality control. It is pointed out that the system performance is degraded due to the influence of filter inductance error or grid inductance reactance. In order to improve the performance, the PQ control strategy of microgrid converter with power and current completely decoupled is adopted. Finally, the equivalent model of microgrid based on Norton equivalent circuit of microgrid converter controlled by PQ is established, and the voltage wave of microgrid is analyzed in depth on this basis. Dynamic reason and interaction mechanism of harmonic resonance between microgrid and distribution network.
In order to effectively suppress voltage unbalance and harmonic distortion, the positive and negative sequence components of fundamental voltage are extracted based on adaptive notch filter (ANF) to realize compensation current detection and reference current calculation. The multi-objective control strategy of the energy storage microgrid converter with the function of active power quality control is studied. The strategy can make the energy storage system suppress the power fluctuation of the microgrid, and realize the full-band compensation of harmonics, reactive power and unbalanced current under the full-compensation control mode, and select compensation control in the frequency division. Proportional Vector Proportional-integral (PVPI) control can also be used to compensate harmonics, reactive power and unbalanced currents selectively. Two multi-objective control strategies can effectively utilize energy storage system to improve the power quality of micro-grid and reduce the impact on distribution network.
On the basis of multi-objective control of energy storage micro-grid converter, in order to further solve the power quality interaction between distribution network and micro-grid, the control strategy of double four-leg microgrid power quality controller (MGPQC) with flexible access mode for super-capacitor (SC) energy storage power supply is studied. In order to compensate for the voltage sag at the common point of connection (PCC), a voltage sag coordination compensation strategy is proposed according to SC-SOC. PCC voltage is always maintained at normal level through the coordination control between micro-power, SC and common load removal. The influence of unbalanced voltage and harmonic distortion on MGPQC transmission power is studied. SC energy storage is used to suppress the power fluctuation at the middle DC side of MGPQC, improve the power quality of microgrid and avoid the influence of distribution network on microgrid. The power quality of the microgrid is improved, and the grid connected operation capability of the microgrid is enhanced.
In order to improve the performance of LCL filter microgrid converter under unbalanced grid voltage and harmonic distortion, a PQ control strategy based on PVPI control is proposed, which combines active damping with capacitor current feedback and feedforward control of grid voltage. The control strategy does not require phase-locked loop and positive-negative sequence separation of current. It can also improve the output power quality of the micro-grid converter and improve the performance of the micro-grid converter under non-ideal voltage conditions. It is difficult to design the parameters of the current closed-loop system because of the complex structure and the large number of parameters, and to improve the robustness of the system through parameter design. In order to improve the robustness of the system, a simplified current closed-loop parameter design method is proposed. The influence of the capacitor current feedback coefficient and the parameters of the PVPI controller on the performance of the current loop is analyzed by the frequency method. According to the requirements of stability, amplitude margin and phase margin, the capacitor current feedback coefficient and the relative resonant gain of the PVPI controller are designed respectively. The method simplifies the parameter design and improves the stability, robustness and dynamic response performance of the system.
【学位授予单位】：哈尔滨工业大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TM711

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