微电网双向变流器的复合控制策略

研究了采用双向变流技术的微电网的稳定控制和电能质量改善方法。考虑到大电网中的动态电压恢复器(DVR)、静止无功发生器(SVG)、有源电力滤波器(APF)等由于动态响应、功率等级和经济性的原因并不适用于微电网,提出了一种基于非线性控制理论的复合控制方法。该方法对电流内环通过状态反馈使非线性系统精确线性化,并完全解耦有功和无功电流,从而提高了内环电流的跟踪精度及动态响应速度,提升了电压外环的快速响应能力。对电压外环采用滑模控制,解决了系统时变参数的问题,提高了外环电压的鲁棒性。实验表明,该复合控制方法具有网侧电流动态响应速度快、跟踪精度高、谐波电流小,直流侧电压动态响应快速的特点。     

基于双馈感应风力发电机组的VSC控制策略研究

在双馈感应风力发电机纽中的变流器通常栗用3XPWM型变流器,该变流器足由网侧变流器、转子侧变流器和中间直流环节构成,网侧变流器是通过定子电压外环、电流内环双闭环控制实现交流侧输入单位功率因数控制和保持中间囊流环节电压的稳定,转子侧变流器是通过转速外环和电流内环控制实现有功和无功功率的解耦。简介绍双馈感应风力发电机组中变流器的作用和表达式,基于控制系统的理论基础,通过Hypersim和Matlab／simulink等实时仿真软件建立控制系统的数字模型,并在1．5MW的双馈感应风力发电机组模型上进行有功、无功功率的独立控制的仿真研究。在仿真结果中表明该控制系统的正确性,使得整个风电系统拥有良好的动态特性,并能有效的跟踪风速变化,满足变速恒频的求。     

一种智能型光伏发电逆变器设计

研制了一种智能的光伏发电逆变器,它既可以与电网并网又可以独立运行.当它与大电网并网时,采用电压电流双闭环的控制策略,以电流源的形式输出电能;当大电网断开出现孤岛时,它采用电压有效值外环瞬时值内环的闭环控制并进行模糊自调整PI参数,以电压源的形式输出电能.最后在光伏发电实验平台上验证了该方法的有效性.     

基于高低压电源切换的双环恒流控制电磁流量计励磁控制系统

为了提高电磁流量计高频方波励磁性能,基于励磁恒流控制仿真分析,采用外环高低压电源切换和内环电流微调的双环励磁恒流控制方式,以保证电磁流量计高频方波励磁时一次仪表输出信号零点稳定、电源利用效率高。设计方波励磁控制系统,以实现高频方波精确励磁。仿真结果表明,高压源电压越高越有利于拓宽励磁频率范围。实验结果表明,系统在高频方波励磁时,励磁电流响应速度快且电磁流量计传感器输出信号零点稳定。     

一种电动汽车谐振式无线供电系统的研究

针对谐振式无线供电系统初级线圈和次级线圈相对位置变化引起接收功率及输出电压变化的现象,以及二极管整流导致次级电路电流畸变和功率因数下降等问题,提出了一种基于PWM整流的电动汽车谐振式无线供电系统,即采用电压外环及电流内环的双环控制方法,以保证供电系统的单位功率因数及直流电压的恒定输出,并且利用ANSYS和MATLAB/Simulink仿真软件,分别研究电动汽车停车充电位置偏差对互感的影响及基于PWM整流的谐振式无线供电系统的性能,仿真结果验证了方案设计的有效性.     

一种改善逆变器输出动态响应的方法

本文提出了一种改进逆变器输出动态响应的方法,在逆变器控制器中断服务程序中,通过瞬态时刻电压电流的一些特性,判断出瞬投以及瞬卸时刻,并采取一些只在瞬态时刻有效的措施,从而达到改善瞬态时的动态响应速度,且不影响UFS稳态时的工作。经过在自制样机上试验,逆变器纯阻性负载瞬投和瞬卸时刻动态响应指标可做到6％以内。     

一种减小有限控制集模型预测控制开关状态计算时间的方法

有限控制集模型预测控制(finite-control-set model predictive control,FCS-MPC)依靠被控逆变器所具有开关状态对控制目标滚动寻优计算。为减小多电平逆变器中滚动计算开关状态所需时间,该文对经典有限控制集模型预测电流控制进行改进。首先,利用控制系统的离散数学模型和参考电流求得被控逆变器在此参考电流下所应输出的参考电压值。此时,引进SVPWM中的分扇区计算概念,判断参考电压所处扇区,最后将该参考电压所处扇区内所包含的开关状态来循环寻优计算。最后Matlab/Simulink仿真平台搭建二极管钳位型五电平并网逆变器系统模型,通过仿真结果,得以验证改进算法的正确性和实用性。     

虚拟同步发电机平衡电流控制方法的研究

该文基于VSG电网电压不平衡情况,分析并网电流失衡、输出功率振荡产生的原因和瞬时负序电流量、瞬时功率量的关系,以有效控制虚拟同步发电机平衡电流。并提出在电网电压失衡下适用的一种VSG平衡电流控制策略,主要是通过电流指令对连续电流内环控制与VSG控制进行计算,在对逆变器输出电流进行控制的基础上,保持VSG本质属性。研究结果显示,电网电压失衡下的VSG平衡电流控制策略能够在电网电压失衡状态下对VSG三相平衡电流进行有效控制,还可以使故障电流、无功与有功振荡幅值变小。     

级联H桥SVG控制策略研究

对于H桥级联型SVG,采用基于瞬时无功功率理论的无功电流检测法对SVG的输出电流进行检测,采用ip-iq检测法可以有效地检测电网处于平衡或不平衡条件下的无功电流。该文研究了直流侧电压控制方法,由于三相损耗的影响,SVG的直流侧电压采用分层控制,即直流侧整体电压平衡控制、各相电压平衡控制以及各相模块电压平衡控制。其中,电流内环作用于直流电,起到跟踪、补偿无功的作用,电压外环要维持直流侧的整体有功平衡。     

数字控制系统中的测速环节及转速计算方法

直接数字控制电机双环调速系统中大多采用了高分辨率数字触发器和高精度数字测速装置,系统结构原理框图与图1所示的相同,其内环是电流反馈及控制环,外环是电机转速反馈及控制环,内环和外环的控制器都由微机来实现,它按PI控制规律完成数字化的控制运算。这系统结构新颖,使用元器件集成度高,是一个静态和动态性能指标都高于常规调速系统的新型全数字化调速系统。     

Design and implementation of FPGA-based phase modulation control for series resonant inverters

Owing to the tremendous advances in the digital technology, and improved reliability and performance of the digital control mechanisms, this paper focuses on design and implementation of digital controller using FPGA-based circuit design approach. The digital controller proposed is designed for series resonant inverter used in DC-DC converter applications. Phase modulation technique is proposed for the realization of digital controller on FPGA. The Series Resonant Converter (SRC) is considered in this paper as a preferred converter topology for high power, high voltage power supplies. This paper studies the implementation of phase shift modulation technique using FPGA. The inverter designed, is IGBT based, and Zero Voltage Switching (ZVS) technique is implemented due to reduced stresses on devices and increased efficiency. The phase modulated series resonant inverters (PM-SRC) promotes ZVS operation when its switching frequency is greater than resonant frequency. The designed PM controller is realized using FPGA on which control algorithm and other features of a controller are developed. The series resonant inverter is built and tested for full load under open loop and closed loop conditions at a switching frequency of 20 kHz. The results are presented under varying load conditions. The simulation and the experimental results were found to match closely.     

A single phase photovoltaic inverter control for grid connected system

This paper presents a control scheme for single phase grid connected photovoltaic (PV) system operating under both grid connected and isolated grid mode. The control techniques include voltage and current control of grid-tie PV inverter. During grid connected mode, grid controls the amplitude and frequency of the PV inverter output voltage, and the inverter operates in a current controlled mode. The current controller for grid connected mode fulfills two requirements – namely, (i) during light load condition the excess energy generated from the PV inverter is fed to the grid and (ii) during an overload condition or in case of unfavorable atmospheric conditions the load demand is met by both PV inverter and the grid. In order to synchronize the PV inverter with the grid a dual transport delay based phase locked loop (PLL) is used. On the other hand, during isolated grid operation the PV inverter operates in voltage-controlled mode to maintain a constant amplitude and frequency of the voltage across the load. For the optimum use of the PV module, a modified P&O based maximum power point tracking (MPPT) controller is used which enables the maximum power extraction under varying irradiation and temperature conditions. The validity of the proposed system is verified through simulation as well as hardware implementation.     

Zero-voltage-switching DC/AC inverter

A novel zero-voltage-switching (ZVS) DC/AC inverter is proposed. The proposed inverter can not only provide output voltage that is higher or lower than DC input voltage but can also use the pulse-width modulation (PWM) control technique. Furthermore, in the proposed inverter, besides operating at constant frequency, all semiconductor devices operate at soft-switching without additional voltage stress and current stress. A design example of 1000 W ZVS-PWM buck-boost inverter is examined to assess the inverter performance     

Feedforward simple control technique for on-chip all-digital three-phase AC/DC power-MOSFET converter with least components

A novel simple control technique for on-chip all-digital three-phase alternating current to direct current (AC/DC) power-metal oxide semiconductor field-effect transistors (MOSFET) converter with least components, which is employed to obtain small current and DC output voltage ripples as well as excellent performance, and using a feedforward simple control method for DC output voltage regulation is proposed. The proposed all-digital feedforward controller has the features of low cost, simple control, fast response, independence of load parameters and the switching frequency, it has no need for compensation, and high stability characteristics; moreover, the proposed controller consists of three operation amplifiers and few digital logic gates that are directly applied to the three-phase converter. The power-MOSFETs are also known as power switches, whose control signals are derived from the proposed all-digital feedforward controller. Instead of thyristors or diodes, the application of power-MOSFETs can reduce the loss of AC/DC converter that is proper to the power supply system. The input stage of an AC/DC converter functions as a rectifier and the output stage is a low pass inductor capacitor (LC) filter. The input AC sources may originate from miniature three-phase AC generator or low-power three-phase DC/AC inverter. The maximum output loading current is 0.8 A and the maximum DC output ripple is less than 200 mV. The prototype of the proposed AC/DC converter has been fabricated with Taiwan Semiconductor Manufacturing Company (TSMC) 0.35 mum 2P4M complementary MOS (CMOS) processes. The total chip area is 2.333 1.960 mm². The proposed AC/DC converter is suitable for the following three power systems with the low power, DC/DC converter, low-dropout linear regulator and switch capacitor. Finally, the theoretical analysis is verified to be correct by simulations and experiments.     

基于自抗扰控制的直流微电网双向Buck-Boost变换器控制策略研究

为了降低直流微电网母线电压的波动,提出基于自抗扰控制的双向Buck-Boost变换器控制策略。运用直流母线电压外环、直流变换器电感电流内环的控制方法实现直流微电网与储能系统之间的能量双向流动。进一步提出基于扩张状态观测器观测输出总扰动,包括负载电流和母线电压的变化,在负载扰动电流影响系统的直流母线电压最终输出前,主动从外环被控对象的输入信号电感电流或输出信号母线电压中提取扰动信息,然后尽快用控制信号将其消除,从而大大降低其对被控量的影响,以有效抑制暂态直流母线的电压波动和冲击,在母线电压产生波动时能够快速恢复到正常的工作状态。仿真验证表明:储能系统可以通过控制策略实现能量的双向传递,并且当母线产生功率波动和电流冲击时,储能系统可以使直流母线电压稳定,提高了系统的可靠性。     

Neural Network and Fuzzy Control Based 11-Level Cascaded Inverter Operation

This paper presents a combined control and modulation technique to enhance the power quality (PQ) and power reliability (PR) of a hybrid energy system (HES) through a single-phase 11-level cascaded H-bridge inverter (11-CHBI). The controller and inverter specifically regulate the HES and meet the load demand. To track optimum power, a Modified Perturb and Observe (MP&O) technique is used for HES. Ultra-capacitor (UCAP) based energy storage device and a novel current control strategy are proposed to provide additional active power support during both voltage sag and swell conditions. For an improved PQ and PR, a two-way current control strategy such as the main controller (MC) and auxiliary controller (AC) is suggested for the 11-CHBI operation. MC is used to regulate the active current component through the fuzzy controller (FC), and AC is used to regulate the dc-link voltage of CHBI through a neural network-based PI controller (ANN-PI). By tracking the reference signals from MC and AC, a novel hybrid pulse width modulation (HPWM) technique is proposed for the 11-CHBI operation. To justify and analyze the MATLAB/Simulink software-based designed model, the robust controller performance is tested through numerous steady-state and dynamic state case studies.     

Control of a converter system for an asymmetrical parameter type two-phase induction motor drive operating in motoring and generating modes

The control of a converter system is presented and discussed for an asymmetrical parameter type two-phase induction machine drive that is operating in motoring and generating modes. The proposed system consists of back-to-back voltage source converters. For a machine side, a three-leg voltage source converter provides both unbalanced and balanced two-phase output voltages with a scalar V/F control based on a carrier space vector pulse width modulation (SVPWM) technique. For a front end, a single-phase AC/DC doubled voltage converter with hysteresis current control is used to keep DC-link voltage constant, thus resulting in a bi-directional power flow operation for the motoring and generating modes. A closed-loop design for the DC-link voltage is fully given and also included is a review of carrier-based SVPWM for two-phase three-leg VSI. The proposed drive system was both simulated using MATLAB/SIMULINK and implemented on digital microcontrollers. The comparative performance evaluation of the whole system between balanced and unbalanced two-phase voltages for the machine is given. The simulation and experimental results show that the unbalanced phase voltage offers better performance for the whole system.     

PWM逆变器死区效应在线补偿

为了减小控制系统中由PWM逆变器死区效应引起的电流波形失真,在分析了死区效应产生的机理及谐波影响基础上,提出了一种死区在线补偿的新方法。该方法结合两相静止坐标系下误差电压的线性特点,估计出误差电压幅值,再在两相同步坐标系下利用误差电压幅值和转子角度的关系对死区效应进行前馈补偿,补偿方法考虑了逆变器的非线性误差,无需额外硬件电路支持或离线测量,避免了电流极性检测,能够摆脱误差电压突变带来补偿不利的缺陷,简单且易于实现。仿真及实验结果表明,该方法能够有效地抑制高次谐波电流分量,改善电流波形质量。     

基于观测器的单相逆变器控制技术研究

基于单相逆变电源的数学模型,设计了一种能保证系统渐进稳定的控制方案.方案根据李氏稳定理论进行设计,并利用观测器观测控制律中的状态变量,同时采用滤波器对原始参考输出信号进行处理,用以产生控制律所需的连续光滑的输出信号及其微分量,设计保证了系统的稳定性及输出电压跟踪误差的收敛性.理论分析及实验结果均验证了控制方法的有效性.