【作者】 漆铭钧；

【导师】 罗安；

【作者基本信息】 湖南大学 ， 电气工程， 2010， 博士

【摘要】 近年来,随着电力电子技术的发展,非线性及时变负荷在电网中的应用日趋广泛,这使得电网谐波污染日益严重,无功需求也日益增大。与此同时,电力用户对电能质量的要求却日益增高,这就使得电能质量的问题日显突出。为降低电网中的谐波含量,改善电压质量,电力系统已迫切需要一种大容量的谐波治理和无功补偿装置,来对系统中的谐波、无功进行有效的抑制和补偿。无源滤波器是目前被广泛采用的一种无功补偿和谐波治理装置,但其存在只能滤除指定次数谐波,有与电网发生串并联谐振可能的固有缺陷,存在被其它新型装置取代的趋势。其中典型的代表是混合型有源滤波器,它兼具有无源滤波器和有源滤波器的优点,已成为无功补偿和谐波治理的热点研究方向。本论文首先介绍了一种适用于不对称系统的无功、负序以及谐波分量检测的方法,随后围绕某变电站的谐波抑制和无功补偿问题进行了深入研究,提出了一种注入式混合型有源电力滤波器(ITHAPF),着重讨论了其拓扑结构、工作原理、电流控制、直流侧电压控制、工程应用关键技术以及综合设计等方面的问题,并在理论研究的基础上提出了基于ITHAPF的谐波分析与治理一体化系统实现方案,最终实现了ITHAPF的工程应用。准确、快速地检测电力系统电流中的负序、无功和谐波成份是保证有源电力滤波器具备良好工作性能的关键。但是,在系统电压三相不对称或者存在畸变时,传统i,一i。电流检测算法检测到的无功、负序和谐波电流在幅值和相位上将存在一定的误差,这会大大影响有源滤波器的补偿性能。鉴于此,本文提出了一种基于改进型ip-i。算法的新型检测方法,该方法不仅适用于负载不对称系统,而且适用于电源电压不对称系统。在检测过程中,该方法不需要采用锁相环(PLL)电路获得同步旋转角,即使在系统三相电压不对称或者畸变时,也不需要对电压进行锁相、滤波或者对称分解,整个算法的基准矢量相位是由数字检测系统自身精确给定的,从而消除了PLL和滤波器延时带来的影响,减小了检测误差,能准确检测出电流的无功、负序和谐波分量。针对某变电站不仅需要治理谐波,而且需要一定容量的无功功率补偿的要求,通过对单独注入式有源电力滤波器和无源滤波器各自优点和缺点的分析,本文提出了一种谐振注入式混合型有源滤波器ITHAPF,由无源滤波器组、有源逆变器和注入支路等部分组成,其有源部分通过注入支路并联入电网。注入支路中的基波谐振支路使得ITHAPF有源部分承受的基波电压很小,这大大减小了有源部分的所需容量。因而,这种拓扑结构适合于高电压系统中的应用。ITHAPF的无源部分主要用来滤除电网中含量较大的特定次数谐波,而有源部分则用来对无源部分滤波后电网中还存在的谐波进行动态治理。同时,无源部分还可提供一定容量的无功补偿。与常规APF相比,由于ITHAPF的电感电容数目大大增加,导致其系统的阶数增高,提高了其控制的复杂性。并且由于注入支路中基波谐振支路的存在,如果控制系统的参考信号存在微小误差,使得输出指令中含有基波分量,那么将在ITHAPF的有源部分形成很大的基波电流,这将对装置的安全稳定运行造成危害。本文对ITHAPF装置进行了数学建模,在此基础上对ITHAPF有源部分基波环流的产生原理及危害进行了分析,提出了一种电流双闭环控制策略,在外环对注入电流进行控制,在内环对逆变器输出电流进行控制。外环控制主要用来保证系统的补偿性能,使注入谐波电流能较好的跟踪负载谐波电流；内环控制主要用来保证装置的安全可靠运行,其在控制系统中增加了阻尼,可抑制系统的谐振,并对逆变器输出电流进行限制。电流外环控制器采用广义积分算法后,控制系统增益。在需要滤除的谐波频率处将会大大增加,而在其它频率处则变化不大,这一特性使得ITHAPF对电网谐波电流具有良好的跟踪性能。ITHAPF的注入支路中包含了基波谐振支路,理论上将使得ITHAPF有源部分承受的电网基波电压几乎为零。因此,很难通过对ITHAPF逆变器的基波有功电流的控制来维持其直流侧电压的平衡。这时,多采用不可控整流电路来维持直流侧电压。但是在装置的实际运行工况下,如果装置接入点电压含有背景谐波或者存在电压跌落等问题,往往会引起电网能量从逆变侧交流侧往直流侧倒灌,进而引起ITHAPF直流侧电压的抬升,不但会影响到系统的补偿性能,还将对系统的安全运行造成严重威胁。本文对电网电压跌落和电网背景谐波电压抬升ITHAPF直流侧电压的原理进行了深入分析,在此基础上提出了四种稳定直流侧电压的方法：采用多重化主电路拓扑结构；合理优化注入支路参数；加装直流侧能量泄放回路；采用PWM可控整流电路维持直流侧电压。针对实际工程中出现的电磁干扰、PWM调制方法过程复杂且计算量大、死区效应影响装置工作性能等问题,本文研究了ITHAPF工程应用中的关键技术。首先,对PWM陡变脉冲信号产生电磁干扰的原因、电磁干扰的危害以及电磁干扰信号的传导方式进行了分析,并对电磁干扰抑制与电磁兼容设计等内容进行了研究,在此基础上,提出了抑制ITHAPF装置电磁干扰的措施,包括减小干扰源强度、切断干扰传播途径、提高系统本身抗干扰能力等。随后,介绍了一种改进规则PWM调制方法,该方法较规则PWM调制方法调制精度有所提高,而计算量却远小于自然采样法。接着,分析了逆变器的死区效应对输出精度的影响,提出了一种死区效应补偿方法一电流反馈死区补偿法,并对该方法进行了相关实验验证。本文的理论和仿真分析表明,ITHAPF的滤波性能与其主电路参数密切相关。结合工程实际应用,本文提出了一套ITHAPF参数设计的方法：对于无源滤波器的设计,需根据实际工况,确定好调谐次数,并从无源部分的制造成本、所需容量及品质因素等方面进行优化设计；对于注入支路的设计,除考虑与无源滤波器设汁相同的几个因素之外,还需对其对有效谐波电流的注入能力以及基波谐振支路的谐波分压问题进行综合考虑；对于输出滤波器的设计,需要从对高频开关毛刺的滤除能力、对有效谐波的输出能力等方面进行综合考虑；对于耦合变压器的设计,在确定了容量之后,需重点考虑其对有源逆变器的电压、电流进行优化匹配,使功率开关器件的容量得到最充分的利用；对于有源逆变器直流侧电容的设计,其电压的取值既需保证逆变器的电流跟踪能力,又要综合考虑装置的成本,而其电容容量的取值,主要由逆变器直流侧电容电压波动的允许值决定。基于前面的原则,本文设计了一套ITHAPF谐波分析与治理一体化系统。该系统兼有谐波检测、分析、治理和相关信息发布等功能,不仅具有谐波动态治理和一定容量无功静态补偿的能力,还具备谐波分析、谐波信息集成及共享等功能。本文设计的一体化系统实地投运后,谐波治理和无功补偿效果均较好。总之,本文实现了一套基于分层分布式结构的电网谐波监测、分析与治理一体化系统,为推进大功率混合型有源电力滤波器在我国的实用化进程提供了有益的参考。更多还原

【Abstract】 At present, nonlinear and time-varying loads are increasing in power grid. Harmonic pollution is getting worse and reactive power is insufficient in power grid. However, the requirement to electric power quality of customers is more and more strict. The matter of voltage quality and harmonic is getting more and more serious. For improving voltage quality and decreasing harmonic contents, a equipment with big capacity which can supressing harmonic and compensating reactive power is necessary in power grid. Passive filter (PF) is atraditional equipment for reactive power compensation and harmonic suppressing. However, PF can only suppress designated-order harmonic currents and is likely to parallel resonate with power grid impedance. It would be replaced by new equipment gradually. The typical device is hybride active ower filter (HAPF). It hold the strongpoints of APF and PF concurrently and already become the hotspot of researching of supressing harmonic and compensating reactive power.Firstly, this thesis proposed a new detection method for reactive power, negative sequence and harmonic current in unbalanced power grid. Then focusing on the research of harmonic suppression and certain-capacity reactive power compensation in one substation, an injection type HAPF (ITHAPF) was put forward. Then some issues of ITHAPF were discussed, such as topology structure, working principle, current controlling, DC voltage controlling, key techniques in engineering application and integrated design. Based on theoretical research, the actualized scheme of integrated system for harmonic suppressing and reactive power compensating was presented, and the engineering application of ITHAPF was implemented.Detecting reactive power, negative sequence current and harmonic components of power system current accurately and rapidly is an important factor for good operation performance of APF. However, the reactive power, negative sequence current and harmonic components detected by traditional ip-iq arithmetic will have amplitude and phase errors when the voltage of power networks is unbalanced or distorted. This has negative influence on the compensation performance of APF. Therefore this, this paper presents a new detection method which based on improved ip-iq arithmetic. This method is suitable for the unbalanced AC system and don’t need PLL circuit to obtain synchronous rotate angle. Even though the voltage of power networks is unbalanced and distorted, it can works without phase locking, filtering and symmetrical decomposition to the voltage beforehand. The phase of the benchmark vector of the arithmetic is given by the digital detection system itself precisely. Therefore, the time delay caused by PLL and the filter is avoided and the error is reduced. Negative sequence current, reactive power and harmonic components can be detected precisely.Aiming at the requirement of suppressing harmonic current and compensating certain-capacity reactive power in one substation simultaneously, based on the analysis of the advantages and disadvantages of sigle injection active power filter and passive filter, this thesis proposed a resonace injection type hybrid active power filter which incudes passive filters, active power filter, injection circuit and so on. The active part connects with power grid parallel through the injection circuit. Because of the existace of fundamental series resonance ciruit (FSRC) in injection circuit, the fundamental voltage which the active part undertakes is small. This decreased the required rate of active part effectively. Therefore, the topology structure of ITH APF is very suitable for application in high voltage condition. The passive part of ITHAPF was used to suppress some specific-order harmonic currents and realize "rough filter"; the active part of of ITHAPF was used to suppress remanent harmonic currents dynamically and realize "precise filter". At the same time, passive part can compensate certain-capacity reactive power.Comparing with conventional APF, ITHAPF have more complicated structure model. Its system order gets higher beacause of increase of the number of inductance and capacitance. So the control system is more complex. If reference signal has error caused by inaccurate detection and this make output instructions contain a small fundamental component, the inverter will generate big fundamental current. This will influence the security and stability of ITHAPF. This paper established the control model of ITHAPF firstly. Then the mechanism and imperilment of fundamental current circumfluence were analysed. For eliminating fundamental component of the inverter output current, this paper proposed a double closed-loops control strategy which composed of outer control loop of injection circuit current and inner control loop for output current of inverter. The outer control loop can make the injected current track the load harmonic current precisely and the improve the performance of APF. The inner control loop can limit the output current of inverter, increase system damping and restrain system resonance. This will impove the security and reliability of the inverter. Generalized integral arithmetic used in outer loop controller will make the gain of the system becomce very big at the frequency of harmonic current. But the gains at other frequency only have small change. This will impove the performance of ITHAPF in tracking the harmonic currents wanted be filtered.Ther injection circuit of ITHAPF contains FSRC. Theoretically, the fundamental voltage undertaked by the active part is nought. So the DC-voltage of ITHAPF can hardly be maintained through controlling the converter’s active current. The usual method is adopting uncontrollable rectifier. However, if the PCC voltage is not ideal, DC-voltage might be raised up by the energy from AC side and the performance and security of ITHAPF would be threated. Based on the analysis of the theory of the DC voltage rising, this thesis proposed four methods for stabilizing the DC voltage including adopting multiple converters, optimizing the injection circuit, adopting energy release circuit and selecting controllable PWM rectifier at DC side.In allusion to the problems in practical engineering such as electromagnetic interference (EMI), complex process and large computing of PWM modulation method, dead-time effect which influences working performance of device, this paper researched some key technologies of ITHAPF in engineering application. Firstly, the reason of EMI generated by PWM pulse, the harm of EMI and the way of EMI transmission were analysed. Then EMI suppression and electromagnetic compatibility (EMC) design were researched. it is pointed out that EMI suppression measures including decreasing intensity of interference source, cutting off EMI transmission route and improving the anti-interference ability of equipments. Subsequently, a mended regulation PWM modulation method was proposed. Comparing with regulation PWM modulation, this method is more precise than regulation PWM modulation and its calculation amount is smaller. Then dead-time effect on output precision of inverter was analysed. A compensation method of dead-time effect, namely, current feedback compensation method was proposed. This method was confirmed by experiment.The theoretical and simulation analysis in this paper shows that performance of ITHAPF correlate with the main circuit parameters. considering application of engineering, this paper proposed a set of method of parameter design of ITHAPF:For passive filter design, capacity, cost and quality factor shoud be considered mainly after tuned frequency was selected based on actual conditions; for injection ciruit design, in addition to the factors considered in passive filter design, harmonic current injection capability and the voltage which FSRC undertakes shoud be considered chiefly. For the output filter design, switching harmonic suppression, effective harmonic output capacity and dynamic tracking ability should be considered first.For coupling transformer design, after determining the capacity, the matching of current and voltage of active part shoud be optimized so that the capacity of the power switching devices can be utilized fully. When designing the DC capacitor of Inverter, its voltage should have a moderate value considering current tracking ability of voltage inverter and the installation costs. The values of its capacitance mainly decided by the inverter DC-bus voltage fluctuations allowed. Based on the previous principle, this paper designed a harmonic analysis and suppressing Integration system based on ITHAPF. This system has the functions of harmonic detection, analysis, suppressing and publication of harmonic data. It can suppress harmonic current dynamically and compensate large-capacity reactive power simultaneously. Besides, the system had excellent harmonic analysis ability, friendly human-machine interfaces and reliable harmonic-data share ability. This integrated system designed to put into operation in the field have good performance for harmonic suppressing and reactive power compensation.In short, this paper realized a integrated systems based on hierarchical distributed structure which has the functions of harmonic monitoring, analysis and suppressing. This will provide some useful practical references for promoting the high power hybrid active filter in China.更多还原