级联型电力电子变压器控制策略研究

电力电子变压器是一种新型的电能转换工具,它可以利用电力电子转变技术来实现传统变压器的功能.基于此,本文对级联型电力电子变压器进行了简单的研究,并根据其自身特点制定对应的控制策略.     

A flexible active and reactive power control strategy for avariable speed constant frequency generating system

Variable-speed constant-frequency generating systems are used in wind power, hydroelectric power, aerospace, and naval power generation applications to enhance efficiency and reduce friction. In these applications, an attractive candidate is the slip power recovery system comprising a doubly excited induction machine or doubly excited brushless reluctance machine and PWM power converters with a DC link. In this paper, a flexible active and reactive power control strategy is developed, such that the optimal torque-speed profile of the turbine can be followed and overall reactive power can be controlled, while the machine copper losses have been minimized. At the same time, harmonics injected into the power network have also been minimized. In this manner, the system can function as both a highly-efficient power generator and a flexible reactive power compensator     

A simple power control technique

An open-loop power control technique that establishes a linear relationship between a d.c. control voltage and the average load voltage is described. The output voltage is insensitive to input a.c. line voltage fluctuations as well as variations in supply frequency. The control output is versatile enough to drive a semiconductor on/off switch or an s.c.r. bridge operating either as a rectifier or as an inverter.     

A novel DC voltage control strategy of series hybrid active power filter

In this article, a novel DC voltage control strategy which is independent of the detection of the primary winding voltage across the series transformer is proposed to solve the DC voltage control problem of the series hybrid active power filter (APF). Meanwhile, this proposed DC voltage control method adopts an open-loop control strategy. The inverter generates unchanged DC voltage control current to ensure that the fundamental voltage loss of the series transformer remain stable. The simulation and experimental results validity and feasibility of the proposed DC voltage control the method of the series hybrid APF.     

A new control strategy for neutral-point-clamped active rectifiers

A new control strategy has been developed for interfacing a neutral-point-clamped active rectifier with the mains. In particular, a method, based on the modulation of the input currents amplitudes, is proposed to compensate the dc-link capacitors voltages fluctuations. The proposed strategy gives good results in all the operating conditions, but it appears to be very useful especially in no-load or low-load operations, where other methods fail. Analytical, simulation, and experimental results, derived from a reduced-scale prototype, are presented and confirm the validity of the proposed approach.     

有源功率因数校正的控制策略及仿真研究

针对开关电源模拟控制存在的不足,对开关电源数字控制技术进行了前瞻性研究。讨论了实现功率因数校正的各种拓扑结构的特点和应用范围,并结合实际情况选用基于Boost电路的功率因数校正变换器,为实现数字控制对传统模拟控制的主电路拓扑结构进行了改进,对其工作原理和工作模态进行了详细分析。根据设计参数,利用Matlab对此模块进行了仿真,通过输入电压和输入电流波形的对比,表明功率因数得到提高,验证了上述研究成果的正确性和优越性。     

A simple active damping control for compliant base manipulators

When a robotic manipulator is mounted to a crane, boom or mobile platform, it loses its accuracy and speed due to the compliance of the base. This paper presents a simple robust control strategy that will reduce mechanical vibrations and enable better tip positioning. The control algorithm uses the sensory feedback of the base oscillation to modulate the manipulator actuator input to induce the inertial damping forces. The authors' previous work (1999) demonstrated the feasibility of the proposed concept using linear analysis. This work extends the concept to a more general case of a nonlinear multiple link manipulator using acceleration feedback and one sample delayed torque. A simulation and an experimental study show very promising results for a test bed consisting of a two-link manipulator and a compliant base     

A simple distributed autonomous power control algorithm and itsconvergence

For wireless cellular communication systems, one seeks a simple effective means of power control of signals associated with randomly dispersed users that are reusing a single channel in different cells. By effecting the lowest interference environment, in meeting a required minimum signal-to-interference ratio of ρ per user, channel reuse is maximized. Distributed procedures for doing this are of special interest, since the centrally administered alternative requires added infrastructure, latency, and network vulnerability. Successful distributed powering entails guiding the evolution of the transmitted power level of each of the signals, using only focal measurements, so that eventually all users meet the ρ requirement. The local per channel power measurements include that of the intended signal as well as the undesired interference from other users (plus receiver noise). For a certain simple distributed type of algorithm, whenever power settings exist for which all users meet the ρ requirement, the authors demonstrate exponentially fast convergence to these settings     

A control method for the active power filter in unsymmetrical voltage systems

In this paper, the authors propose a calculation method for the compensating current reference of the active power filter, where a nonlinear load exists in a three-phase, three-wire unsymmetrical voltage system. This new method has been named the extension pq method. The authors have experimented with the extension pq method and the pq method, using the same current-controlled intelligent power module inverter for both methods. The results of the experiments proved that in the unsymmetrical voltage system the source current was distorted in the case of the pq method, but undistorted in the case of the extension pq method.     

A novel open-loop control method for a current-source active power filter

This paper presents a new control system for a current-source active power filter. The harmonic current compensation is realized using only a feedforward control of the load currents. The LC filter resonance of the converter is damped in an open-loop manner using the dynamic equations of the supply filter. The benefits of the proposed control system are that it is simple and straightforward, the number of measurements and sensors can be minimized, and also that the LC filter size can be optimized according to proper harmonic distortion level of the supply currents without care about the stability issues of the closed-loop system. This usually leads to reduction of the filter size. Also, the changes in fundamental current components of the active filter can be effectively realized when the active power filter can also be used as a fast reactive power compensator. The control system also includes the calculation delay compensation of the digital control system. The control system is realized using a single-chip Motorola MPC555 microcontroller. The tests with the prototype show effective current harmonic compensating performance of the nonlinear loads.     

微电网功率跟踪策略优化研究

针对微电网功率跟踪控制复杂、实时性差的问题,提出微电网系统负载功率跟踪与各分布式电源最大功率跟踪的分层控制策略。在构建含风力发电、光伏发电及蓄电池的风光储系统模型的基础上,针对电源层采用基于扰动观测法的最大功率跟踪,实现分布式电源的效率最大化;配电层采用基于直接功率控制的负载功率跟踪,保证系统功率平衡。研究结果表明,两种功率跟踪控制策略同时发挥作用,可以减少控制模块的工作量,缩短系统响应时间,优化了传统微网功率跟踪策略。     

A 31-level cascade inverter for power applications

Power inverter modules fed with separate DC voltage sources of voltage ratio 1:2:4:8 are connected to form a cascade multilevel inverter. This new proposal combines the advantages of the static phase-shifter and chain-cell converter concept. Using the same number of power devices as a standard nine-level inverter, the proposed converter operates as a high-power digital-to-analog converter with 31-level resolution. Electrolytic capacitors used in the proposed inverter for providing the DC voltage sources will never be connected in opposite polarity in all cases, thus ensuring high reliability. The proposal has the potential for uninterruptible power supply and flexible AC transmission applications     

A series active power filter adopting hybrid control approach

The series active power filter (APF) is suitable for compensating a voltage type harmonics-producing load, whereas the control approach it adopts may directly influence its compensation characteristics. This paper first discusses the control approach of detecting source current in terms of the basic operation principle of a series APF, then developing a control approach of detecting load voltage. On the basis of these, a hybrid control approach is proposed. In this approach, the reference signal of the compensation voltage needed by the series APF is obtained by detecting both source current and load voltage. Thus, this approach has the advantages of the first and the second control approaches and, at the same time, it can overcome their respective drawbacks. For practical realization, the control methods of the PWM inverter in the series APF and for regulating its DC side voltage are discussed in detail. A prototype of the series APF is manufactured and corresponding experimental investigation is done. The results show that when the series APF, if adopting the hybrid control approach instead of the other two, compensates for the voltage type harmonics-producing load, its performance can be improved greatly     

A novel control algorithm for active power conditioner without load current sensor

A novel control algorithm for an active power conditioner (APC) is proposed. The operation of this APC can be divided into two modes: active power filter mode and back-up power mode. When the mains are normal, the proposed APC operates in the active power filter mode that provides the functions of active power filter and battery charger. Once the mains have failed, the proposed APC operates in the back-up power mode to supply power to the demands. In this circuit design, the control circuit is suitable for both operation modes except in the arrangement of feedback signals. Hence, the design cost can be reduced; also, no load current sensor is used in the circuit. The practicality of the method is, therefore, further enhanced.     

A new control system with a control delay compensation for a current-source active power filter

In this paper, a new control system for the current-source active power filter is presented. The harmonic current compensation is realized using combined feedforward control of the load currents and closed-loop control of the supply currents. The control system includes a simple method for compensating the sampling and calculation delays of the digital control system. The compensation in the proposed method is achieved using the regular LC filter of the active power filter as an energy storage for load currents, and no additional components is needed in the main circuit. Furthermore, the calculation power demand of the compensation method is very low and is, therefore, suitable for single-chip microcontroller implementations. The proposed control system is realized using a 32-bit Motorola MPC555 microcontroller. The simulation and experimental results show effective filtering performance also for higher order harmonics of the distorted load currents.     

Repetitive-based control for selective harmonic compensation in active power filters

This paper proposes a repetitive-based controller for active power filters, which compensates selected current harmonics produced by distorting loads. The approach is based on the measurement of line currents and performs the compensation of selected harmonics using a closed-loop repetitive-based control scheme based on a finite-impulse response digital filter. Compared to conventional solutions based on stationary-frame current control, this approach allows full compensation of selected frequencies, even if the active filter has limited bandwidth. Compared to synchronous-frame harmonic regulations on line currents, the complexity of the proposed algorithm is independent of the number of compensated harmonics. Moreover, it is more appropriate for digital signal processor implementation and less sensitive to rounding and quantization errors when finite word length or fixed-point implementation is considered. Experimental results on a 5-kVA prototype confirm the theoretical expectations.     

有源电力滤波器的无差拍控制应用研究

有源电力滤波器是谐波治理一种常用的设备,PWM变流器控制是有源电力滤波器的关键部分。在众多控制方法中,空间矢量脉冲宽度调制由于有较高的电压利用率和控制精度而广泛应用,但是由于运算量较大而产生的延时是不可避免的。利用无差拍控制能够有效消除延时,但前提是需要准确预测出下一时刻的指令电流。为了减少计算量,电流预测方法通常采用简便的方法,为了提高预测精度,提出一种新的预测电流方法。通过仿真软件Matlab对新方法进行仿真并利用硬件平台进行硬件实验,仿真结果和实验结果都验证了新方法的可行性。     

统一潮流控制器预测直接功率控制策略研究

在此以基于矩阵变换器为基础的统一潮流控制器为研究对象,介绍了当前统一潮流控制器的发展状况以及控制策略现状,在此基础上提出预测直接功率控制策略用于该系统,并建立了预测模型,以便有效提高系统的动静态性能。通过Matlab仿真平台搭建了系统模型,通过仿真试验对比了PI控制和预测直接功率控制的波形效果。仿真结果表明了所提控制策略的正确性和有效性,有利于电力系统安全可靠运行和数字化实现。     

基才三相四线APF的模糊直接反馈控制

为解决三相四线有源电力滤波器的非线性控制问题,时三相四线有源电力滤波器进行电路模型分析,提出采用Takagi-Sugeno模糊直接反馈控制的方法,对电源电流进行模糊直接反馈控制,快速地实现了三相四线有源电力滤波器的非线性电流补偿。采用并行分布补偿的方法设计了模糊反馈控制器,将三相四线有源电力滤波器的非线性问题线性化,在稳定性条件下求解得线性矩阵不等式,得到无功功率及非线性电流全补偿控制策略的状态反馈增益．仿真及实验结果验证了此模糊直接反馈控制的有效性。     

A digital power factor correction (PFC) control strategy optimized for DSP

A predictive algorithm for digital control power factor correction (PFC) is presented in this paper. Based on this algorithm, all of the duty cycles required to achieve unity power factor in one half line period are calculated in advance by digital signal processors (DSP). A boost converter controlled by these precalculated duty cycles can achieve sinusoidal current waveform. One main advantage is that the digital control PFC implementation based on this control strategy can operate at a high switching frequency which is not directly dependent on the processing speed of DSP. Input voltage feed-forward compensation makes the output voltage insensitive to the input voltage variation and guarantees sinusoidal input current even if the input voltage is distorted. A prototype of boost PFC controlled by a DSP evaluation board was set up to implement the proposed predictive control strategy. Both the simulation and experimental results show that the proposed predictive strategy for PFC achieves near unity power factor.