外文翻译原文-静止无功补偿器控制方法综述.pdf

编号 毕业设计外文翻译 原文 毕业设计外文翻译 原文 学 院 机电工程学院 专 业 电气工程及其自动化 学生姓名 覃 思 明 学 号 1200120328 指导教师单位 机电工程学院 姓 名 李 彩 林 职 称 副 教 授 2016 年 03 月 20 日 An Overview on Control Methods Used in Static Var Compensator Youjie Ma Tao Zhao and Xuesong Zhou Key Research Laboratory for Control Theory power system additional control I INTRODUCTION Static var compensator SVC is one of the important components of modern power system Its basic function is to absorb reactive power from the power grid or transport continuous and adjustable reactive power to the power grid so that it can realize the control of its installation point voltage In addition in the process of adjusting output impedance changing can also improve the stability of the power angle of system Since the 1970s the major forms of SVC such as thyristor control reactor TCR thyristor switch capacitor TSC and the mixed device TCR TSC get a rapid development In recent years with the improvement of high power thyristor device manufacturing technology the application of SVC in power system is more and more wide At the same time with the rapid development of power industry the capacity of the power system is increasing and the power grid structure is increasingly complex and huge so SVC system stability issues become more prominent 1 Therefore in order to improve power system stability and dynamic quality the SVC additional control method has become an important research topic in the current power system This article will briefly introduce some additional control methods commonly applied to SVC and control effects about various control methods applied to different control purposes are compared At last some recommendations of the feasibility of the control methods will be given in terms of engineering applications In this paper the commonly used control methods will be divided into traditional and modern control method Among traditional control methods the most common one PID Proportion Integration Differentiation will be introduced In order to comparison the distortion PI Proportion Integration control method which belongs to the category of nonlinear control methods will be stated together with traditional PID control methods Modern control methods include nonlinear control nonlinear robust control nonlinear variable structure control nonlinear adaptive control differential geometry control and inverse system method etc the optimal variable target strategy control and intelligent control fuzzy control genetic algorithm Additional control methods of power system equipped with SVC are always designed on the basis of the traditional linear control theory On the project they are always analyzed and designed in the light of the root locus method frequency response and the state space method If in the disturbance moment system working point have no change the controller designed by the traditional methods has good control effect But the SVC system has strong nonlinear characteristics and it also affected by the uncertainty in the operation process Therefore in a large system especially under large disturbance the traditional methods cannot guarantee its optimal control in the whole system performance even deteriorate the system performance and unable to meet the demand of engineering 2 In recent years domestic and foreign scholars carried out extensive research on this issue So many modern control methods are gradually developed such as nonlinear variable structure control nonlinear adaptive control feedback linearization method optimal variable aim control and intelligent control First the traditional PI control are introduced which are universally applied in present engineering Then some modern control methods are introduced as an additional control in the application of SVC II OPERATING CHARACTERISTICS As is shown in Figure 1 taking the single machine infinite bus system as an example the characteristics of SVC and the control mechanism of installed SVC are introduced The working principle of SVC and generator and line parameters are shown in Figure 2 Fig 1 A single machine infinite bus system with static VAR compensator 92978 1 4799 7098 8 15 31 00 2015 IEEE Proceedings of 2015 IEEE International Conference on Mechatronics and Automation August 2 5 Beijing China Fig 2 Working principle graph of static VAR compensator To guarantee the stability of generator power angle and line voltage stability the coordinated control model of generators and SVC in a single machine infinite system is established 1 VVVxh xh mm02 01 2 0 is generator power Angle 0 is speed steady state operating point L Bis inductance value of SVC and it s initial value is 0L B C Bis capacitance of SVC s Tis time constant of SVC s K is amplification factor of SVC regulation system s uis control volume of SVC System impedance 2121 CLd BBXXXXX among them 1 1Ltd XXXX 22L XX d Xis generator d axis synchronous reactance d Xis generator d transient reactance t Xis transformer reactance and 1L X is transmission line reactance 2L X is reactance values between SVC and system 1 w and 2 w are simulation system disturbance Equation 1 and equation 2 form the mathematical model of single machine infinite system of SVC Equation 2 changes according to the control purpose It can be seen that power system containing SVC presents nonlinear characteristics is additional control of SVC Install location is shown in figure 3 Fig 3 Controller structure of SVC with additional controller III CONTROL PRINCIPLE AND CONTROL PURPOSES The basic function of SVC is to absorb from the power grid or transmit to grid continuously adjustable reactive power to maintain a constant voltage at the installed points and in favor of reactive power balance of the grid SVC master control generally adopts the traditional PI control to maintain line voltage stability Additional control due to different control purpose and control method of using presents diversity Control system control thyristor trigger angle by changing the size of the equivalent reactance value to adjust the output reactive power So the SVC can be equivalent to a controlled reactor The output reactive power of SVC device is directly proportional to the square of the system voltage So when electric power system voltage drops SVC device output reactive power will be reduced in proportion to the square of the system voltage In Literature 3 the role of SVC to improve voltage stability are reviewed It is shown that SVC is good for the system voltage stability in its adjustable range In the power system SVC at least has following several functions 1 Phase modulation and voltage regulation 2 Improve the transient and dynamic stability of the system 3 Restrain the power oscillation of system and the voltage flicker caused by impact load 4 Restrain over voltage Compared with other components in flexible alternative current transmission systems SVC has the following advantages 1 Fast response speed The response of the controller is in milliseconds Using feedforward control technology response speed of regulator even can reach about microsecond 2 Excellent dynamic and continuous reactive power regulating function In addition SVC also has advantages of low loss and operation maintenance convenience Compared to the same capacity condenser it has comprehensive technical and economic advantages IV CLASSIFICATION DESCRIPTION A PID control 1 sin 20 1 0 0 0 0 wuKBB T B w HX VE P HH D ssLL s L d sq m 93 PID control is called a proportional integral differential control which is the most commonly used correction method in SVC The functional block diagram of conventional PID control system is showed in Figure 4 Fig 4 Controller structure of PID controller PI control without differentiating aspects is the most commonly used traditional control methods in SVC Literature 4 designs PI damping controller using pole placement method to position the gain of PI controller to increase the dynamic stability of SVC Literature 4 designs a PI additional controller of the SVC for suppressing subsynchronous oscillation In order to suppress oscillations caused by a variety of torque torsional modes it designs a PI controller which can adjust output power of SVC according to generator speed changes in real time The PID controller parameter applied to SVC in engineering is generally adjusted at the scene The commonly used adjustment methods are Ziegler Nichols adjustment rule frequency response method and optimizing calculation method Using these methods PID controller can be on site mediated accurately and detailedly Furthermore some automatic adjustment methods have been studied out so some PID controllers have the ability to adjust automatically on line Deformations of the PID controller such as the I PD control and multi degree of freedom PID control have been applied in the project The value of PID control is the broad applicability of most control systems Although it can not achieve optimum control in many cases the controller is straightforward and less need to determine the adjustment parameters Besides it is easy to be implemented in the engineering and has a certain robustness So it has been widely used in engineering and still dominates in engineering applications of the SVC This traditional PID applies to SVC the nonlinear complex systems unable to ensure rapidity and stability at the same time and meet the precise control of the output impedance of the SVC To meet the development requirements of the future power grid it must combine with modern control methods B Improved deformation PI control Improved PI control belongs to the nonlinear control of modern control theory Among of them fuzzy PI control is most widely used Fuzzy PI controller structure is showed in Figure 5 Under the control of intelligent coordinator software switch S can automatically switch to fuzzy controller or PI controller working condition according to different situations Literature 5 puts forward a multi objective unified controller according to the principle above In order to obtain better transient performance fuzzy control is used in great deviation And in order to obtain better static performance PI control is used in small deviation Literature 6 designs a SVC additional controller by combining PI control with a new method of adaptive backstepping Literature 7 design nonlinear PI additional controller based on fuzzy algorithm genetic algorithm etc And it have achieved good control effect on SVC Fig 5 Controller structure of fuzzy PI controller Compared to the conventional PI control improved PI control in SVC this complex system of nonlinear overcome defects of dependence on precise mathematical model poor adaptability and robustness Fuzzy PI controller has superiority in strong practicality and easy to implement in engineering But compared to traditional control advantages of simple and little cost improved PI control cannot invest to engineering due to its complex structure C The nonlinear robust control The essence of the robust control is to design a closed loop system stable controller which can meet the index and have a certain domain including Hcontrol 2 Lgain control analysis control Nonlinear control theory is a control theory which obtains a controller with robust performance through certain reaction performance index of the infinite normed optimization in H space Its advantages embody in dealing with the performance of multivariable system design and robust stability The essence of 2 L gain is to guarantee robustness to uncertainties interference The basic idea of structure singular value method is to put the actual control problem down to beg structure singular value problems Accordingly the whole motion control system is completed The defect of it is the improvement of the algorithm of minKGFl K and the analysis method of which is in bad condition number system Literature 8 adopts coordination control method with SVC and generator excitation nonlinear theory to design a coordinated control strategy It can effectively restrain the system oscillations and improve the transient stability of the system Literature 9 proposes a interference suppression method in the sense of 2 Lgain to get the interference rejection control law Combined with the strong nonlinearity and uncertainty of power system 94 it proposes a new coordinated control law with SVC and generator excitation robust nonlinear The general issues of nonlinear robust control which is used in SVC are still unresolved Hnorm considers the largest disturbance situation so it s robustness is relatively conservative It rely on the designer s experience to choose right letter In accordance with the different parameters and the selected different weighted it should redesign the controller Although the robustness of nonlinear control is conservative robust control has strong robustness For the interference parameter deviation model uncertainty and noise suppression system has good stability And the control rate bases on input output and frequency domain description It is easy to implement in engineering so it has feasibility of engineering application D Nonlinear Variable Structure Control Based on the deviation and its derivative of adjusted amount nonlinear variable structure control forces the system state in any initial conditions to reach and remain in the pre designed super plane at a certain approaching rate and gradually becomes stabilized on the plane Control law has character of non uniqueness So it can provide more choices for engineering designers Literature 10 introduced active disturbance rejection control technique technology ADIC to achieve a nonlinear variable structure coordinated control of SVC and generator excitation Then it designs a variable structure coordinate additional controller to simultaneously improve the system power angle stability and dynamic characteristics of the voltage Literature 11 using a nonlinear system theory and variable structure control theory deduces coordinated control rate and designs SVC and HVDC nonlinear coordinated sliding mode variable structure controller Despite the variable structure control has the limitation of high frequency chattering and difficulty to reach switching surface but sliding mode variable structure with the interference and perturbation invariance can effectively solve the problem of SVC robustness and can guarantee the global asymptotic stability of the system So it ensures that the method has the feasibility of engineering application in SVC E Nonlinear Adaptive Control Adaptive Control Adaptive Control AC is the sub optimal control theory which puts system identification and control together It can online identify and control the dynamic change of the parameters of the object or structure along with the change of working condition of system to constantly revise and adjust the controller parameters or structure In the end it can automatically track object changes to achieve optimal control Literature 12 proposes adaptive backstepping method for SVC It completely retains the nonlinear characteristic of the system and improves the response speed of the system but also break through the classical certainty equivalence principle In the initial stage adaptive control does not surely guarantee the stabilization And it will take some time to track input accurately Besides it is unable to handle nonlinear structural changes in the system so it is not feasible on engineering applications It can be predicted that the future focus of the study is fuzzy neural networks robust and other F Differential Geometry method and Inverse System method Differential geometry method find nonlinear feedback by appropriate partial differential homeomorphism transformation Under the action of nonlinear feedback it can map a nonlinear system as linear system Then it designs the controller using linear control method Literature 13 applies inverse system method to power system and establishes the non affine nonlinear model to design the SVC nonlinear additional controller Many modern control methods should linearize SVC the nonlinear system The two methods as the basis of other control methods are mainly used in the linearization of actual system Inverse system method is more simple in principle than exact linearization method and easier to accept by engineering personnel But for the two approaches accuracy requirement of the mathematical model is very high which limits its application in engineering G Optimal Variable Aim Control Optimal variable aim control OVAC firstly drives system to reach an equilibrium point with the largest artificial intermediate stability region which is estimated by the transient energy function Then it drives system to reach a stable equilibrium point after the failure This method can effectively improve the transient stability of the system first swing and increase the dynamic stability of the subsequent swing The key lies in the selection of artificial intermediate balance point Literature 14 deduced HVDC and SVC nonlinear integrated control strategy which is based on optimal variable aim control theory on the basis of HVDC and SVC integrated control model Optimal variable aim control strategy can solve the problem about installation of SVC system which may exist multiple stable equilibrium point And it can adjust the system to return to its kinetically stable equilibrium state Besides it can realize partition sharing hierarchical control for the system So it can be implemented online easily and have the feasibility of engineering applications H Intelligent Control Genetic Algorithm GA deals with structural object directly without any requirements of differentiability and continuation of function And it can automatically acquire and to guide the search space adaptively adjust the search direction Fuzzy Control FC using relevant experts knowledge or experience as a starting point adopts language control rules directly without establishing accurate mathematica