Iron Loss Calculation of AC Filter Inductor for Three‐Phase PWM Inverters

In recent years, remarkable advancement of new power semiconductor devices, such as SiC and GaN, enables the increase of switching frequency of power converters, and hence the volume of passive components, such as ac filters and transformers, can be reduced. However, temperature rise caused by the inductor loss is increasing, and hence iron loss evaluation of the inductor is one of the most important issues to realize high power density converters. Conventionally, an improved generalized Steinmetz equation (iGSE) has proposed in order to calculate the iron loss under a pulse voltage magnetizing condition. However, accurate iron loss calculation of the ac filter inductor used in a PWM inverter cannot be realized. The authors have proposed two methods of iron loss evaluation of ac filter inductors. The first one is a loss map method which can calculate the iron loss without using a real PWM inverter. Another one is an ILA (Inductor Loss Analyzer) which can measure the iron loss in every switching period in a real PWM inverter. In this paper, comparisons of the iron loss between the ILA and the loss map method on both the single‐phase and three‐phase inverters are studied. It is found that iron loss of the ac filter inductor in the three‐phase PWM inverter which is calculated by the loss map method cause a large error on a specific condition. In order to prevent the calculation error, the authors proposed a revised loss map method and proved the effectiveness of the method.     

Robust Adaptive Control of Pulse-width Modulated Rectifiers Based on Adaptive Super-twisting Sliding-mode and State Feedback Controllers

Abstract—This article proposes a new robust adaptive hybrid controller for three-phase pulse-width modulated rectifiers to improve control performance. This hybridization is implemented by combining the second-order sliding mode with the adaptive gain super-twisting control law in the DC bus voltage control loop and state feedback adaptive control in the d-q-axis current control loops. The control objectives are fourfold: (1) driving the DC bus voltage to a reference signal without using a priori knowledge of the plant parameters, (2) forcing the d-q-axis current errors to zero, (3) assuring a satisfactory power factor correction in relation to the AC source, and (4) eliminating the chattering effect. In the closed-loop control system, three-phase source currents and the DC bus voltage are supposed to be available for feedback. As a result, no a priori knowledge of the plant parameters is necessary in the design of the proposed controller. In addition, the proposed controller does not have the disadvantages of singularity, over-parameterization, and chattering phenomenon. Results of experimental studies prove that the proposed control system guarantees the tracking of reference signals with high performance despite all the parameter and external disturbance uncertainties.     

基于阀点优化的1 000 MW超超临界机组节能优化控制技术

针对目前1 000 MW超超临界机组滑压优化运行中存在的问题,分析了凝汽式机组真空变化和抽汽变化对发电机组最优滑压曲线的影响,提出一种以汽轮机阀门开度为控制目标的滑压曲线在线节能优化调整控制策略,结合协调控制系统（CCS）的优化,加快了主蒸汽压力和机组负荷的响应速率,提高了CCS控制品质,实现主蒸汽压力快速、平稳过渡到最佳滑压曲线上,很好地解决了滑压优化带来的CCS控制问题。通过在2台1 000 MW 超超临界机组上的实际应用表明,无论环境温度、抽汽量如何变化,机组始终能在最佳的滑压状态运行,实现了机组经济运行的目的。     

Validation of an integral sliding mode control for optimal control of a three blade variable speed variable pitch wind turbine

Reduction in cost of wind energy requires most efficient control technology which can able to extract optimum power from the wind. This paper mainly focuses on the control of variable speed variable pitch wind turbine (VSVPWT) for maximization of extracted power at below rated wind speed (region 2) and regulation of extracted power when operating at above rated wind speed (region 3). To extract maximum power at below rated wind speed torque control is used whereas to regulate rated power at above rated wind speed pitch control is used. In this paper a nonlinear control i.e. integral sliding mode control (ISMC) is proposed for region 2 whereas a conventional proportional–integral (PI) control is adapted for region 3 of a VSVPWT. The proposed controller is combined with modified Newton Raphson (MNR) wind speed estimator to estimate the wind speed. The stability of the proposed ISMC is analyzed using Lyapunov stability criterion and the control law is derived for region 2 which is also adapted for the transition period between region 2 and region 3 (region 2.5). The dynamic simulations are tested with nonlinear FAST (Fatigue, Aerodynamics, Structures, and Turbulence) wind turbine (WT). The simulation results of ISMC are presented and the control performance is compared with conventional SMC and existing controllers such as aerodynamic torque feed forward control (ATF) and Indirect speed control (ISC). It is seen that especially in region 2.5, ISMC gives better performance compared to all other controllers.     

具有不确定参数的车辆跟随滑模控制

假定车辆质量及作用在车辆上的空气阻力、地面对轮胎的摩擦力等参数随时间变化但有界,研究自动化公路系统车辆纵向跟随控制。根据车辆不确定参数的有界性和滑模控制策略,采用饱和函数法,设计了车辆跟随系统的纵向变结构控制规律;基于李雅普诺夫稳定性方法,对控制系统的稳定性进行分析,并确定系统收敛的充分条件。仿真结果表明:采用所设计的控制方法,在达到满意跟踪性能的同时,还能有效抑制控制颤振,对参数不确定性具有鲁棒性。     

架空输电线路雷电过电压识别

准确辨识架空输电线路雷电过电压类型对改进防雷设计具有十分重要的意义。为此,分析了感应、反击、绕击3种雷电过电压的发生机理,对输电线路雷电流行波波形特点的研究表明感应雷电过电压三相电流行波相似程度大,反击雷电过电压发生时,闪络相在绝缘子未击穿时,由于避雷线等的分流、耦合作用,存在空间电磁耦合电流,而绕击过电压闪络相不存在空间电磁耦合电流。提出了以输电线路雷电流行波三相电流波形最小相似度、上升时间比作为上述3种雷电过电压识别判据。还分析了上述特征参量在工程应用中可能受到的干扰因素及解决方法。大量EMTP仿真表明所提取的特征量有效可行。     

基于随机滤波器的SMPM电机定子电阻辨识

用随机滤波器对无速度传感器的交流永磁电机的定子绕组阻值进行观测。观测过程中为了降低控制器的计算工作量,采用参数的混合辨识方法,通过滑模观测器得到电机控制系统的转速量,再将电机的定子电压、电流和转速作为已知量,用于对电机定子绕组电阻的估计,考虑到定子绕组电阻的变化速度通常远低于定子电压、电流的变化速度,因此可以设定不同的计算周期以期降低计算量。     

三峡近区电网相关运行问题研究

当前,三峡近区电网存在两个亟待解决的问题,一是斗笠-江陵断面枯水期受热稳定限制,制约跨省(区)资源优化配置,二是三峡近区短路电流水平接近超标,且有不断加重趋势。针对三峡近区电网的斗江断面潮流输送能力不足和短路电流偏高问题进行深入研究,分析其问题产生的根源,并结合电网发展提出逐年解决措施。     

基于等效误差法的直线电机XY平台二阶滑模控制

对于直线电机驱动XY平台,系统动态的非线性、系统不确定性因素以及曲线轨迹的轮廓误差模型相对复杂等问题影响其轮廓加工精度。采用适用于多轴非线性运动系统轮廓控制的等效误差法,建立可用于一般曲线跟踪且容易计算的XY平台等效误差非线性模型。运用二阶滑模控制方法进行轮廓控制器的设计,通过连续控制量使滑模面及其时间导数在有限时间内趋近于零,削弱抖振的同时抑制不确定性因素对系统性能的影响,使直线电机XY平台达到高加工精度要求。理论推导与仿真结果表明,所设计控制系统能有效提高XY平台的轮廓加工精度。     

模糊滑模变结构矢量变频调速系统建模与仿真

当前,矢量控制是一种优越的交流电机控制方式,它模拟直流电机的控制方式使得交流电机也能取得与直流电机相媲美的控制效果。依据矢量控制的基本原理和方法,用MATLAB/SIMULINK模块构建了一个基于转子磁场定向的旋转坐标系下的交流异步电机矢量控制系统仿真模型,对其速度控制器提出并设计一种模糊滑模变结构控制算法。该控制算法具备模糊逻辑控制和滑模变结构控制两者优点,并且较好地解决了滑动模态的抖动问题。仿真结果表明了该设计的可行性以及具有良好的动静态性能、较强的鲁棒性。