外文翻译--三相电压型PWM整流器建模和仿真研究.doc

重 庆 理 工 大 学文 献 翻 译二级学院 应用技术学院 班 级 109217402 学生姓名 康亮 学 号 10921740209译 文 要 求1、译文内容必须与课题（或专业）内容相关，并需注明详细出处。2、外文翻译译文不少于2000字；外文参考资料阅读量至少3篇（相当于10万外文字符以上）。3、译文原文（或复印件）应附在译文后备查。 译 文 评 阅导师评语（应根据学校“译文要求”，对学生外文翻译的准确性、翻译数量以及译文的文字表述情况等作具体的评价） 指导教师： 年 月 日三相电压型PWM整流器建模和仿真研究摘要：三相电压型PWM整流器（VSR）广泛用于AC/DC/AC系统前端整流。考虑到VSR本身非线性特点，建立适合于控制器设计上的数学模型比较，提出了一种状态反馈解耦控制电流内环和直流电压平方外环的电压型PWM整流器新型控制策略，基于功率平衡理论，采用解耦状态反馈控制方法，分析并建立了三相电压型PWM 整流器 dq 坐标系下的线性化数学模型。由于采用直流电压平方外环，使典型的非线性模型线性化，控制器设计直观精确，提高了直流电压和网侧电流的跟踪能力，改善了波形。提出了一种空间矢量的简化算法，简化了运算过程。在MATLAB/SIMULINK 环境中建立了仿真模型。仿真结果表明：所设计整流器具有优良的稳态性能和快速的动态响应，实现简单，具有一定的实用价值。 关键词：电压型PWM整流器；功率平衡；解耦状态反馈；空间矢量脉宽调制；仿真引言 在当今的电力系统当中大都采用二极管和相控转换器。这种转换器电路简单，但缺点是线电流畸变严重和功率因数较低。为了解决这个问题，PWM 整流器的基于线电流波形整定的的各种功率因数校正技术被提出来了。 PWM 整流器有以下几个优势比如:直流总线电压的控制功率双向流动单位功率因数、线电流正弦化。 为了提高输入功率因数和整定输入电流正弦化，整流装置采用了许多控制技术，传统的整流模型是多输入多输出非线性系统。整流器控制中最困难的就是非线性。 在优秀的研究报告中，直接电流控制传统的控制策略是建立功率因数补偿的内环和电压调节的外环的双环控制。大多数的系统参数依赖于PI调节器：输出电压控制环会产生电流内环的参考电流的参考指数或振幅。 电流内环的作用是是三相交流负载的电流跟随给定信号的变化。 本文着重探讨了VSR的建模和控制。以一种新的基于电力电量平衡方程来取代原有的非线性方程。然后应用非线性输入变换使改进后的模型线性的。提出了一种简化算法空间矢量PWM整流器。该算法避免了传统方法的查表的正弦或反三角和复杂计算的需要是直接计算空间电压矢量的责任周期跟踪参考电压矢量在每一个环节上的空间矢量。1、 VSR的建模和控制1.1VSR在dq坐标系下的数学模型三相电压型电路的主电路如图 1 所示，每个半导体开关由一个 IGBT 和并行的二极管组成。这里 ua，ub，uc分别为三相平衡电压源的相电压，ia，ib，ic为相电流，vdc是直流输出电压，R和L分别代表滤波电抗器的电阻和电感，C是平滑电容，RL是直流侧负载，il 是负载电流。 以下公式描述了整流器在 dq 坐标下的动态特性：在这里urd=Sdvdc, urq=Sqvdc,urd,urq,和Sd,Sq分别是整流器输入电压，在同步旋转dq坐标系的开关函数。ud,uq和id,iq分别为同步旋转dq坐标下的电压源和电流,为角频率。 图 1，三相电压型整流器主电路1.2 电流环状态反馈解耦方法在上述的非线性方程中，公式（1）（2）说明sd,sq与状态变量vdc有关，urd=Sdvdc和urq=Sqvdc,说明urd和Sd ,urq和Sq没有动态关系，因此一个非线性输入变换可以用于修改将旧的输入变量 sd,sq变成urd ,urq,而且模型说明dq电流和耦合电压wliq和wlid有关系，而且受主电压ud,uq以及urd和urq的影响。公式（1）和(2）中的urd和urq表示为公式（4）（5）。 将公式（4）（5）带入公式（1）（2），被控变量和新输入的最关系是线性和解耦的非线性表达，VSR 的预期关系是：从等式中我们可以看到，两个轴的电流是完全解耦的，与只和期望的id与iq是有关系的，电压环和电流环采用简单的PI控制方法。1.3 外环电压设计公式（3）描述了Vdc的模型，功率平衡方程可以用来辅助替代方程模型。吸收的有功功率交流电流功率（Pac）和有功功率转换器直流功率（Pdc）表达:Pac和Pdc的关系是：Pac=Pdc+Ploss (10)Ploss包括电阻R功率损耗以及开关和VSR传导损失，电阻R通常很小，它实际上是合理的忽视它的能量损失，整流器损失是比电阻R损失功率大，但它们仍然是总功率很小的一部分，因此，忽略整流器损失没有明显的损失整流器准确性。如果更精确的表示损失，需要整流器可以表示一个小电阻RL,直流侧总电阻用RL表示，从Pac=Pdc中可以看出，下面是动态结果：重新整流公式得：由Vdc的单相特性，以为变量，公式（12）就会变成线性的，将公式（8）带入公式（12）得到这是的动态方程和输出的状态变量，是输入，设计一个简单的PI控制器能够调节直流电压无稳态误差，ud是可测量的，实际的输出变量id从中得到，电流内环的结果为id的参考值。图2显示内部电流回路与状态反馈解耦和VSR外环控制系统。图2，三相VSR的双闭环控制模块2.空间电压矢量合成当得到urd和urq后，通过dq变换到变换得到精确的直流电压命令和直流总线电压。根据图1开关状态的桥式整流电路，桥式整流器电压可以假设8个状态电压矢量（V0到V7）。V1到V7是六个确定的非零矢量，V0和V7是图3中所示的两个零矢量。三相输入电压分为六个60，如图4所示：定义 图3 PWM桥式整流器-变换空间矢量表示图4 三相输入电压六个分区N=sign(B0)+2sign(B1)=4sign(B2) (16)在图5所示，信号分为6个60间隔，相对于另一个信号的迹象，它满足了那个标志两个信号幅值都是一样的。在每个分区，并没有明显变化。设置的值，每个都是独一无二的。例如，再间隔1，B0是正的，B1，B2是负的。图5，B0，B1，B2六个分区其中的矢量是基于表达式（6）的，如图4表示，矢量与N的一致关系如表1所示。表一三相电压可视为一个电压矢量对。有许多不同的方法合成，根据调制的不同组合八个向量。这些方法，可以使两相调制的开关损耗减少，在一个工作循环内其中一个开关应该总是开或关。理想的参考矢量是在每一个子环平均取样时间Ts和实现了三个最近的空间向量的平均向量。例如，在图3中所示的参考矢量，电压Vs和角度和电流I用矢量1，矢量2和零矢量表示。三个持续的空间向量T1、T2、TZ分别计算为：其他矢量合成与矢量合成方法是相似的，通用的变量X,Y,Z的通用矢量表达如下：对于任何参考向量，持续两个时间空间向量，如列表2。3、仿真基于前面的分析，利用图1的三相VSR的MATLAB/SIMULINK仿真，利用IGBT的实验负载和以下参数：uRMS220V,L 3mH,R0.1,C 4700Mf,RL16,vdc=700V.下面的两个数据总结simulation的仿真结果。图6的结果显示了瞬态响应输出电压，第二个数字显示输入电流的瞬态响应。在回路负载RL=16时仿真开始时刻直流母线电压停留在二极管整流器的水平。然后，应用控制负载电阻和输出电压增加到预期直流电压值。图7显示所需的电压和电流在同一侧。我们能看到电流与电压同相位。图6，直流电压动态仿真结果4、总结本文中，给出了一个非线性变换方法推导三相VSR。一种新的控制策略是应用前面介绍的状态反馈解耦的电流内环和本文介绍的基于状态空间解耦的电压外环，利用非线性输入的转变，传统的非线性模型可以变换为线性模型。这一改善使设计的控制器变得简单明了。介绍了SVPWM算法描述和验证。仿真结果表明它具有更好的控制精度，更少的开关动作、计算简便、容易实现，更好的利用直流电压。图7，A相电压、电流仿真结果文献原文Modeling and Simulation Research for Three-Phase Voltage Source PWM RectifierAbstract:Pulse-Width Modulated three-phase Voltage Source Rectifier(VSR)is the building blocks of the most of AC/DC/AC systems as the front-end rectifier. The major difficulty in control is caused by the nonlinearities in the rectifier model. The linear mathematical model of VSR in d-q coordinates was deduced with analysis based on the power balance equation. A new control strategy using inner current loop with state feedback decoupling and outer voltage square loop was proposed.Nonlinear input transformation was used to derive a linear model from the original nonlinear model. The advantages of the proposed scheme include accuracy controller design fast dynamic response and high quality of the current and voltage waveforms.A simplified algorithm was proposed for space vector PWM SVPWM rectifier. The whole system was modeled and simulated by using the toolbox of MATLAB/SIMULINK. Simulation results show that the PWM model proposed can satisfy steady-state characteristics and fast transient response. This design scheme has some value for practical operation due to its simple implement.Keywords:VSR;power balance equation;state feedback decoupling; SVPWM;simulation Introduction Diode and phase-controlled converters constitute the largest segment of power electronics that interface to the electric utility system today. These converter circuits are simple but the disadvantages are large distortion in line current and poor power factor. To combat these problems the PWM rectifier various power factor correction(PFC) techniques based on active wave shaping of the line current have been proposed.The PWM rectifier offers several advantages such as: control of DC bus voltage,bi-directional power flow unity power factor and sinusoidal line current. Many control techniques have been adopted for these rectification devices to improve the input power factor and shape the input current of the rectifier into sinusoidal waveform. In actual implementations the direct current control scheme is widely adopted. The conventional rectifier model is a multi-input multi-output nonlinear system. The difficulty in controlling the rectifiers is mainly due to the nonlinearity. As reported in the excellent survey traditional control strategies in the direct current control scheme establish two loops: a line current inner loop for power factor compensation and an output voltage outer loop for voltage regulation. The most uses system parameters dependent Proportional Integral (PI) regulator: for the output voltage control loop which can generate the modulation index or the amplitude of the reference current for the inner PWM input current control loops. The main task of the current inner loop is to force the currents in a three-phase ac load to follow the reference signals. This paper focuses on the modeling and control of the VSR.A new equation based on power balance is introduced to replace the original nonlinear equation. Then,nonlinear input transformation is applied to make the improved model linear. A simplified algorithm is proposed for space vector PWM rectifier. This algorithm avoids the look-up tables of sine or arc-tangent and complex calculations needed in the conventional methods by directly calculating the duty cycles of space voltage vectors which track the reference voltage vectors in each sector in the space vector.1 Modeling and Control of VSR 1.1 The mathematical model of VSR in d-q coordinates The main circuit diagram of the three-phase voltage source rectifier structure is shown in Fig.1.Each power semiconductor switch consists of an IGBT connected in parallel with a diode. Where ua ,ub and uc are the phase voltages of three phase balanced voltage source and ia ,ib and ic are phase currents vdc is the DC output voltage R and L mean resistance and inductance of filter reactor respectively C is smoothing capacitor across the dc bus RL is the DC side load and iL is load current. The following equations describe the dynamical behavior of the boost type rectifier in Park coordinated or in d-q:Where,urd=Sdvdc, urq=Sqvdc,urd,urq,and Sd,Sq are input voltage of rectifier,switch function in synchronous rotating d-q coordinate respectively. Ud,uq and id,iq are voltage source current in synchronous rotating d-q coordinate respectively. is angular frequency.Fig.1 Circuit schematic of three-phase two-level boost-type rectifier1.2 Decoupled state-feedback control method of current loop In the above nonlinear model equation 1 and equation2 show that both input variables Sd and Sq are coupled with the state variable vdc. The fact that urd Sd vdc and urq=Sq vdc, shows that there is no dynamics between urd and Sd or urq and Sq.Therefore a nonlinear input transformation can be used to modify the old input variables Sd and Sq to the new input variables urd and urq. Moreover the model shows that d-q current is related with both coupling voltages Liq and Lid, and main voltages ud and uq besides the influence of urd and urq.urd and urq in the equations(1)and(2)can be regulated to ensure the correctness of equations(4)and(5). Putting equation (4)and(5)into equation(1)and(2)the nonlinear expression is such that the final relation between the controlled variables and the new inputs is linear and decoupled. Thus,the expected relations in the VSR are,We can see from equation that the two axis current are totally decoupled. urd and urq, are only related with id and iq respectively.The simple proportional-integral(PI)controllers are adopted in the current and voltage regulation.1.3 Design of outer voltage square loopEquation (3) describes the dynamics of vdc. Power balance equation can be used to derive an alternate equation for vdc dynamics. The active power absorbed from the ac source(Pac) and the active power delivered to the converter dc-side (Pdc) are expressed by: The relationship between Pac and Pdc is: Pac=Pdc+Ploss (10) Where Ploss includes the power loss in the resistor R as well as the switching and conduction losses in the VSR. The resistance R is always very small and thus it is practically reasonable to neglect its power loss. The rectifier losses are larger than the power loss in R but still they count for a small portion of the total power. Therefore,the rectifier losses can also be neglected without noticeable loss of accuracy. If better accuracy is desired the rectifier losses can be represented by a small resistor in series with RL. The total equivalent dc-side resistance is still represented by RL. From Pac=Pdc,the following dynamic results: Which can be rearranged in following form: Due to uni-directional nature of vdc ,Taking vdo2 as the variable,(12) will become linear.Putting equation (8) into equation(12),This is a first-order dynamic equation with vdc2 as the state variable as well as the output,and Pac as the input. A simple PI controller can be designed to regulate the DC voltage with no steady state error. Since ud is measurable,the actual input variable id can be derived from Pac. The result is actually the reference value of id for the current inner control loop. Fig.2 displays inner current loop with state feedback decoupling and outer voltage square loop control system for VSR.Fig.2 Block diagram of double close-loop control for three-phase VSR2 Voltage Space-vector SynthesizationWhen the urd and urq acquired the SVPWM method is realized through d-q to -transformation to trace the AC current command exactly and regulate the DC bus voltage. Depending on the switching state on the circuit Fig.1 the bridge rectifier leg voltages can assume 8 possible distinct states represented as voltage vectors (V0 to V7). V1 to V6 are six fixed nonzero vectorsV0 and V7 are two zero vectors as shown in the Fig.3.The input three phase voltage are divided into six 60input intervals,as shown in Fig.4. Defining: Fig.3- space vector representation of the PWM bridge rectifier leg voltageFig.4 Six intervals of input three voltageN=sign(B0)+2sign(B1)=4sign(B2) (16)As shown in Fig.5the signals are divided into six 60 intervals it satisfies that the signs of the amplitudes of two signals are the same and opposite to the sign of another signal. And no sign change occurs during each interval. The value of N in every sector is unique.In interval 1,for example,B0 is positive,B1 and B2 are negative.Fig.5 Six intervals of B0 B1 and B2The sector in which is depends on the expression (6) Compared with Fig.4,it is obvious that the corresponding relations between value N and sector are seen in Table1. Table 1 Determination of sector of based on NThree-phase voltage can be treated as a voltage vector Vs. There are many different methods of modulation to synthesize according to the different combinations eight vectors. Among these methods,the two-phase modulation can make switching loss minimize,in which one switch should be always set ON or OFF in one working cycle.The desired reference vector is sampled in every sub-cycle Ts and realized by time averaging the three nearest space vectors in the space vector plane. For example the reference vector shown in Fig.3with magnitude Vs and anglein sectoris realized by applying the active vector 1the active vector 2 and the zero vectors. The durationsT1,T2 and TZ of the three space vectors respectively is calculated as:The vector synthetic method of other sector is similar. The expressions which is developed on the universal variable X,Y,Z are shown as following: For any reference vector the duration time of two space vectors are assigned as Table2.3 Simulation ResultsBased on the former analysis the MATLAB/SIMULINK simulation model for the VSR of Fig.1with the test load was implemented