Model Reference Adaptive Control for Switched Systems with Closed-loop Reference Model Under Arbitrary Switching

This paper explores the model reference adaptive control problem for a class of switched linear systems under arbitrary switching with no need for the measurability of the system state.Based on the state of reference model and the measurable output error, adaptive laws and controllers are designed for switched systems.Each subsystem may have its individual reference model and controller, which increases the design flexibility.The introduction of the closed-loop reference model is to get a better transient performance of the whole switched systems.A numerical example is provided to verify the effectiveness of the main results.

EFFICIENT STEADY-STATE ANALYSIS METHOD FOR CLOSED-LOOP PWM SWITCHING CONVERTERS

An analysis technique of steady state and stability for closed-loop PWM DC/DC switching converters is presented. Using this method, the closed-loop switching converter is transformed into an open-loop system. By means of the fact that in steady state, the two boundary values are equal in one switching period. The exponential matrix is evaluated by precise time-domain-integration method, and then the related curve between feedback duty cycle and the input one is obtained. Not only can the steady-state duty cycle be found from the curve, but also the stability and stable domain of the system. Compared with other methods, it features with simplicity and less calculation, and fit for numerical simulation and analysis for closed-loop switching converters. The simulation results of examples indicate the correctness of the presented method.

关于取消新疆电网750 kV断路器合闸电阻可行性的仿真研究

目前,超、特高压输电线路常用合闸电阻吸收能量,并将其作为限制合闸过电压的主要手段,但是带有合闸电阻的断路器不仅造价昂贵,而且还存在运行可靠性差、故障率高等缺点,如果能利用低残压、保护性能优异的金属氧化物避雷器替代合闸电阻来限制操作过电压,不仅可以降低成本,还能简化断路器操纵机构以提高电力系统运行的可靠性。文中以新疆电网最长距离的750 kV线路为研究对象,通过沿线安装多组避雷器的方式,将沿线最大2%合闸过电压限制到规程规定的1.8 p.u.以内,为新疆电网所有750 kV长距离线路取消断路器合闸电阻的可行性提供了理论依据。

多触指刀闸式接地开关短路关合过程动稳定性仿真分析

接地开关是电力系统中使用量较大、应用较广的设备之一,其稳定性与可靠性对电网的运行安全起着重要作用。仿真研究多触指刀闸式接地开关短路关合过程的动稳定性。首先搭建接地开关短路关合故障系统模型,分析接地开关载流特点;其次以接地开关为物理模型,分析关合过程状态并进行短路电流时域匹配;最后对接地开关关合过程中的动稳定性进行仿真分析。结果表明,接地开关短路电流时域匹配法可以分析接地开关关合过程中短路电流对动稳定性的影响,为大容量接地开关结构设计研发提供参考。

发电机出口刀闸合闸不到位原因分析及处理办法

以一起发电机出口刀闸合闸不到位为例,通过分析现象,从机械方面和电气回路方面入手,逐步排查可能导致故障的原因,逐一验证,最终通过试验找出故障原因为刀闸控制箱内限位接点动作连片有轻微变形所致。解决的临时措施为使用工具将合闸限位接点动作连片向上方弯曲倾斜一定角度,经反复试验可行;彻底解决方法为大修时更换限位接点动作连片和固定连片的弹簧。

含储能的多端口柔性合环开关协调控制研究

随着光伏和风能等可再生能源在柔性配电网中的比例不断提高,可再生能源发电的间歇性输出给电力系统带来了不稳定性与波动性。现有的柔性合环开关因为硬件参数和容量限制,无法应对负荷超容量波动带来的频率超限及潮流转移造成的电网开路问题。因此,有必要将柔性合环开关与储能技术相结合,构建新型柔性互联配电网,对带电池储能系统的多端口柔性合环开关设计相应的控制策略。首先,对于硬件参数不同和工作状态差异造成的储能单元荷电状态(state of charge,SOC)不均衡,设计自适应的SOC均衡控制策略。其次,对负荷大波动和稳压侧开路故障,设计切换策略以调节电网频率并进行短时直流电压支撑,确保下级负荷的稳定运行。最后,利用基于MATLAB/Simulink平台的仿真模型和RTLAB硬件在环平台验证了所提协调控制策略的有效性和实用性。

基于风险理论的合闸过电压抑制方案评估方法研究

断路器合闸电阻是抑制电力系统合闸操作过电压的有效措施,线路避雷器起后备保护作用。然而随着输电线路变短以及避雷器性能提高,线路操作过电压有所下降;同时合闸电阻高成本、低可靠性的弊端凸显,过电压抑制方案的技术经济性缺乏量化的综合评估。基于风险理论提出合闸过电压抑制方案评估方法,搭建系统沿线过电压仿真模型,定义计及闪络率、故障率、成本等多种因素的综合风险指标,实现过电压抑制方案技术经济性的量化评估。算例对实际500kV系统进行过电压仿真和风险指标计算分析,并基于所提评估方法对合闸电阻取消的可行性进行讨论,验证了所提评估方法可以合理量化过电压的抑制效果和存在的系统风险,为过电压抑制方案的选取提供有效评价。

一起220kV隔离开关异常合闸故障分析

变电站控制与信息交互都离不开低压电缆,随着电缆使用年限增加,逐渐丧失绝缘性能,使其在绝缘薄弱的区域与大地之间形成某种导电途径,导致二次回路误导通、开关误动作现象时有发生,本文结合一起隔离开关异常合闸故障,分析控制回路故障原因,并提出相关整改措施。

一类有源钳位七电平PFC拓扑结构研究

针对传统两电平图腾柱PFC拓扑存在开关器件电压应力大、适用功率等级较低等问题,提出了一种新型无桥七电平PFC通用拓扑结构。通过使用不同的双向钳位开关管替换通用拓扑的钳位支路,从而获得相应拓扑。以最具代表的I型七电平PFC拓扑为例对工作原理详细分析。选择适用的辅助电路用以平衡直流侧电容电压,并结合载波同相层叠脉宽调制与电压电流双闭环控制策略生成相应开关脉冲序列,控制对应开关管的有序通断,实现桥臂电压七电平输出。通过仿真验证了拓扑结构的有效性与可行性,所提拓扑降低了开关管电压应力,实现了高功率因数运行,适于功率等级更高的应用场合。

A Multi-Gap Multi-Channel Gas Switch for the Linear Transformer Driver

A multi-gap and multi-channel gas switch with convexo-convex discal planet electrodes was designed and investigated. Eight gaps are formed in series by a trigger electrode, six intermediate electrodes and two high voltage electrodes with a uniform gap length of 5 ram. The self breakdown and triggered breakdown performance of the switch are reported. Both the delay time and jitter decrease with the increase in the trigger voltage, switching coefficient and the decrease in the trigger isolating resistor. The delay time of the switch is about 40 ns, and the jitter is less than 2 ns when charged with 4-85 kV and triggered by a voltage pule of -75 kV. The inductance of the switch is about 30 nH.

Study of the Fast-Closing Switch Used for Fault Current Limiters in Power System

This paper presents a new type of fault current limiter (FCL) based on fast closing switch, which is composed of a capacitor bank and a reactor in series. The main control component is a fast closing switch connected in parallel with the capacitors, which is driven by the electromagnetic repulsion force. It can response the order within 1 ms. When fault occurs, the switch closes and the capacitors are bypassed, and the fault current is limited by the reactor. Simulation analysis and experiment show that the electromagnetic repulsion force actuator can meet the demand of fast closing switch, it is feasible to develop the FCL with low cost and high reliability.

Experimental Study of the Multi-gap Multi-channel Gas Spark Closing Switch

A coaxial multi-gap multi-channel spark switch with stainless-steel-spring ring gap electrodes is designed and investigated. The switch is triggered by a pulse applied to the cylindrical electrode outside the discharging channel through a parasitic capacitance coupling. The jitter of the switch is reduced by several short-distance gas gaps in series, and its inductance is reduced by a multi-channel discharge on account of the inductance isolation between the coils of the spring ring electrode. The experimental results indicate that the switch is of low inductance (15-30 nH), low jitter (-3 ns), and stable breakdown performance

基于UC3842反激式AC-DC开关电源设计

基于传统的反激开关电源使用二极管整流,开关电源损耗较大。设计了一种多路输出反激式AC-DC同步整流开关电源,输出分别为12 V和6 V。采用导通电阻极低的MOSFET代替二极管。介绍了开关电源的工作原理、UC3842内部结构、反激闭环控制以及同步整流。使用PSIM仿真软件搭建开关电源整体闭环模型,对电路进行仿真。结果表明,电路同步整流相比于二极管整流电路输出电压精度更高,同步整流输出电压、电流特性好、纹波小。

Research on a Fast-Closing Switch Based Fault Current Limiter with Series Compensation

A new type of fault current limiter (FCL) with series compensation based fast-closing switch is proposed. It is composed of a capacitor bank and a reactor in series. The main control component is a fast-closing switch connected in parallel with the capacitors, which is driven by the electromagnetic repulsion force. When fault occurs, the switch closes and bypasses the capacitors, and the fault is limited by the reactor then. Simulated analysis and experiments show that it is feasible to develop the FCL with low cost and high reliability. The effectiveness of transient stability for power system is evaluated by digital simulation.

Noise analysis and characterization of a full differential CMOS interface circuit for capacitive closed-loop micro-accelerometer

To achieve a high precision capacitive closed-loop micro-accelerometer,a full differential CMOS based on switched-capacitor circuit was presented in this paper as the sensor interface circuit.This circuit consists of a balance-bridge module,a charge sensitive amplifier,a correlated-double-sampling module,and a logic timing control module.A special two-path feedback circuit configuration was given to improve the system linearity.The quantitative analysis of error voltage and noise shows that there is tradeoff around circuit's noise,speed and accuracy.A detailed design method was given for this tradeoff.The noise performance optimized circuit has a noise root spectral density of 1.0 μV/Hz,equivalent to rms noise root spectral density of 1.63 μg/Hz.Therefore,the sensor's Brown noise becomes the main noise source in this design.This circuit is designed with 0.5 μm n-well CMOS process.Under a ±5 V supply,the Hspice simulation shows that the system sensitivity achieves 0.616 V/g,the system offset is as low as 1.456 mV,the non-linearity is below 0.03%,and the system linear range achieves ±5 g.

基于UC3842双闭环反馈实现开关电源

为了提高开关电源的稳定性,采用控制芯片UC3842电流和电压的双闭环反馈,控制驱动的PWM波形每个周期占空比的大小,实现开关电源的稳定输出。该文对设计的主电路和控制驱动电路利用仿真软件Multisim搭建仿真模型,仿真结果表明设计的合理性。根据仿真模型完成硬件电路并调试,实验结果表明,该文设计的电路合理,利用UC3842设计的电流和电压的双闭环反馈,实现调节驱动波形每个周期占空比的大小,最终达到稳定开关电源输出电压的目的。

开关电源闭环反馈控制的教学与实验方法

现有“电力电子技术”课程中,闭环反馈控制特性分析、反馈控制电路设计和实验等教学和实验方法存在不足。通过对开关电源闭环反馈控制设计分析和实验方法的教学实践进行研究,详细分析了典型开关电源电压模式控制结构、控制特性和闭环反馈控制电路设计。基于频率分析仪器AP300建立了实验测量系统,设计实验内容和考核要求,帮助学生掌握相关实验技能,优化了“电力电子技术”课程的教学实践。

基于能量分析的自供能式电磁混合悬架分层协调控制

为了在保证减振性能的同时提高主动悬架的能量回收性能,提出一种基于电磁混合作动器的自供能式主动悬架系统,采用分层协调切换控制策略,包括上层控制器和下层控制器。在考虑电机损耗的情况下分析作动器的能量流动状态,得出自供能判据,设计下层非线性双闭环控制器通过馈能/供能电路实现对作动器的控制;根据对下层系统的分析,设计拥有主动、半主动、馈能3种模式的上层协调切换控制器。在MATLAB/Simulink环境中对控制策略有效性进行仿真验证,并分析电磁混合主动悬架性能,结果表明,所提出的悬架系统动态性能与无能量回收功能的主动悬架基本一致,且储能模块的平均功率小于0,符合自供能判据,在该控制策略下悬架系统可实现自供能。

一种DC-DC升压变换器的动态建模及其数字补偿

针对广泛应用于核电子设备的稳压电源中的非理想型直流—直流(DC-DC)升压变换器进行了研究,提出了一种新的DC-DC变换器设计方案。首先,采用平均状态空间技术对非理想升压变换器进行动态建模,通过对状态方程进行状态平均,以到变换器的连续时间传递函数作为设计有效控制器的前提;然后,通过采用数字再设计和直接数字设计两种方法,对DC-DC升压变换器的数字控制器进行了设计,从而实现变换器的闭环控制和动态响应。仿真实验结果表明,提出的DC-DC升压变换器及其数字补偿设计不仅实现了预期的动态电压调节性能,而且在输入电压动态变化范围、瞬态响应时间和响应带宽方面相比于目前先进的设计方案具有优势。

CVT铁磁谐振过电压的抑制与不同故障下二次电压特征分析

针对220 kV CVT(电容式电压互感器)因铁磁谐振故障产生的过电压问题与3U0监测装置误报警的问题,结合实际参数建立仿真模型,分析了各个参数对于过电压的影响,给出了最佳参数配置并对电路拓扑结构进行优化,有效地抑制了铁磁谐振过电压。建立仿真模型对比了各个工况下的二次电压数据。仿真结果表明:二次侧接地再恢复和一次侧合闸操作均会引发铁磁谐振,同时伴随着1/3次谐波的产生,但前者引发的铁磁谐振较为严重;采用速饱和阻尼器对铁磁谐振进行抑制,阻尼电阻为5Ω时有最佳的抑制效果;阻尼器两端并联定值电阻可以有效提高抑制效果,且当电阻阻值为5Ω时效果最佳;3U_0在不同工况下对应不同的频谱特征,可据此区分不同故障。