An energy-based control for an n-H-bridges multilevel active rectifier

This paper deals with the control of a multilevel n-H-bridges front-end rectifier. This topology allows n distinct dc buses to be fed by the same ac source offering a high loading flexibility suitable for traction applications as well as for industrial automation plants. However, this flexibility can lead the system to instability if the dc buses operate at different voltage levels and with unbalanced loads. Thus, linear controllers, designed on the basis of the small-signal linearization, are not effective any longer and stability can not be ensured as large-signal disturbances occur. The use of a passivity-based control (PBC) designed via energy considerations and without small-signal linearization properly fits stability problems related to this type of converter. The system has been split into n subsystems via energy considerations in order to achieve the separate control of each dc bus and its stability in case of load changes or disturbances generated by other buses. Then, a set of n passivity-based controllers (one for each subsystem) is adopted: the controllers are linked using dynamical parameters computed through energy balance equations. Hence, the system dc buses are independent and stable as experimental results demonstrate.     

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     

Genetic algorithm-based design of the active damping for an LCL-filter three-phase active rectifier

Active rectifiers/inverters are becoming used more and more often in regenerative systems and distributed power systems. Typically, the interface between the grid and rectifier is either an inductor or an LCL-filter. The use of an LCL-filter mitigates the switching ripple injected in the grid by a three-phase active rectifier. However, stability problems can arise in the current control loop. In order to overcome them, a damping resistor can be inserted, at the price of a reduction of efficiency. The use of active damping by means of control may seem attractive but it is often limited by the use of more sensors compared to the standard control and also by a complex tuning procedure of the controllers. This paper introduces a new active damping method that does not require the use of more sensors. It consists of adding a filter on the reference voltage for the modulator. The tuning process of this filter is easily done, for a wide range of sampling frequencies, with the use of genetic algorithms. This method is used only for the optimum choice of the parameters in the filter and an on-line implementation is not needed. Thus the resulting active damping solution does not need new sensors or complex calculations. Moreover, in the paper particular attention is devoted to the susceptibility of the system in a high polluting environment.     

Dynamic control of a fixed pattern rectifier

A three-phase, sinusoidal, active rectifier is presented, based on the classical inverter topology. The switches are governed by a fixed pulse width modulation (PWM) pattern, and the control strategy is extremely simplified as compared with many active rectifiers. General equations describing the steady-state operation of fixed pattern rectifiers are given. A dynamic model of the simplified control rectifier is presented, based on the nonlinear equations describing the system. Based on the analytical model, the classical PI-controller yields poor dynamic results, especially at low load conditions. However, the dynamic performance of the prototype is much better, due to the effects of commutation dead time of the rectifier switches. It is shown that a small modification to the classical PI-controller yields a remarkable increase in amplitude and phase margin, without slowing down the response. The obtained dynamics show a clear improvement over the classical PI-controller and are adequate for most applications     

A practical approach to the design and control of active endoscopes

Actual endoscopes and boroscopes, widely used in industry and in minimal invasive surgery, have considerable limitations, mainly due to their low number of degrees of freedom and their manual operation. Two different solutions for the electrical actuation of articulated endoscopes are presented in this paper. The technical constraints for this kind of application are very limited space for the actuators and high performance in terms of torque and angular reach. The first solution classically consists in a 2 d.o.f. structure steered by two pairs of antagonist shape memory alloy (SMA) wires. The sizing and preload determination for those actuators follow an original analytical approach. The second solution consists in a multi-d.o.f. structure actuated by thin NiTi springs mounted in an antagonist configuration and directly integrated in the structure of the endoscope. The geometry of the springs is obtained by optimization through genetic algorithms and finite elements method. Experiments show good adequacy between real behaviour and numerical model and also validate the approach.This study is also enhanced by a control scheme specifically developed for SMA actuators in an antagonist configuration. It is based on a first order sliding mode scheme, which has the advantage of a great structural simplicity. The experimental results show that this solution can reach a good compromise between the dynamic behaviour of the actuator, its energy consumption and the structural lifetime of the endoscope.     

Fast-response high-quality rectifier with sliding mode control

A PWM rectifier including an uncontrolled rectifier and a Cuk converter stage driven by a sliding mode controller is described. Like other high-quality rectifiers, this solution allows low-distorted and in-phase line current. Moreover, due to the sliding mode control, fast and stable response is achieved, in spite of the large output filter. Control complexity is the same as that of standard current-mode controls. Converter analysis, design criteria, and experimental results are reported     

Integrated active rectifier and power quality compensator withreduced current measurement

This paper describes a three-phase integrated active rectifier and shunt power quality compensator (IPQC). The measurement of only three currents is required, and the control algorithm can be implemented using a low-cost controller. The IPQC improves the harmonic content of the supply current, displacement power factor, supply current balance, and can serve as a four-quadrant active rectifier for motor drives and other DC-link loads. The operation of the IPQC is experimentally verified using a conventional three-phase insulated gate bipolar transistor voltage-source inverter. A low-cost fixed-point DSP-based controller with fixed-band hysteresis current regulation is used for the implementation of the control algorithms     

Analysis and implementation of active clamp SEPIC converter with synchronous rectifier

An active clamp SEPIC converter with synchronous rectifier is presented to achieve zero voltage switching (ZVS). The active clamp circuit is adopted in the proposed converter to absorb the energy stored in the leakage inductance of the transformer and limit the peak voltage stress on the switching devices. The resonance during the transition interval between the switching devices will help the power switches to turn on at ZVS. Therefore, the switching losses of switches are effectively reduced. The synchronous rectifier is used at the secondary side of the transformer to further reduce the conduction loss. The principle of operation and the steady-state analysis of the proposed converter are presented. Finally, the experimental results taken from a laboratory prototype with 240 W (12V/20A) rated power are presented to verify the effectiveness of the proposed converter.     

Online secondary path modeling in multichannel active noise control systems using variable step size

In single-channel feedforward active noise control (ANC) systems, additive random noise based methods are often applied to achieve secondary path modeling (SPM) during online operation. This paper investigates the issue of online SPM in multichannel ANC systems. It is shown that the application of existing methods for online SPM in multichannel ANC systems greatly increases the computational complexity. Here we extend our previous work on single-channel variable step-size online SPM to multichannel ANC systems. It is shown that the proposed method has reduced computational complexity as compared with other methods. Computer simulations are carried out that demonstrate the effectiveness of the proposed method.     

A common mode voltage reduction in boost rectifier/inverter systemby shifting active voltage vector in a control period

This paper proposes a new space-vector pulse width modulation (SVPWM) strategy that can reduce the number of common mode voltage pulses in a three-phase boost rectifier/inverter system using a synchronized switching sequence. In the proposed SVPWM strategy, it is possible to eliminate one common mode voltage pulse in every control period by shifting the active voltage vectors of the inverter to align to those of the boost rectifier. Thus, a reduction in the total number of common mode voltage pulses and RMS motor leakage current can be obtained without extra hardware. Since the proposed SVPWM strategy can be simply implemented in software, it is widely applicable regardless of the power capacity of the converter and results in no increment of converter volume, weight and price. Moreover, because the proposed SVPWM strategy maintains the magnitude of the active voltage vector required for motor control and simply changes the distribution of the zero, voltage vector, it does not effect the control performance of the power converter     

A direct digital control for the phase-controlled rectifier

Direct digital control of the phase-controlled rectifier (PCR) is implemented with a minimum control hardware structure. A digital phase-locked voltage control (PLVC) without detecting the line voltage is presented. An inner fast control loop is proposed to stabilize the PCR system and to obtain its constant loop gain. In the inner loop, an averaging function is introduced to feed back the average DC voltage of the PCR output without the feedback filter. Its synchronism is modeled and analyzed. An optimal constant digital integral, proportional, and measurable variable feedback (IPM) current controller with a time-multiplied performance index is also proposed to obtain a good dynamic response of the output current. All control functions are implemented with an Intel 8797 single-chip microcomputer. Experimental results show that the scheme gives good dynamic and static performance for the PCR system     

单相PWM整流器控制方法及谐波分析

传统二极管不控整流或晶闸管相控整流,对电网注入大量谐波及无功功率,造成电源污染.PWM整流器采用全控型开关器件取代二极管或半控型器件,并将PWM控制技术引入整流器,在稳定直流电压输出同时,使交流侧电源电流接近正弦波,实现能量的双向流动.通过介绍单相PWM整流器的控制方法,利用Matlab/Simulink搭建仿真模型,比较分析不同控制方式下PWM整流器运行时电压波形及输入电流的谐波频谱.     

Three-phase switch mode rectifier with hysteresis current control

A three-phase configuration of a switch mode rectifier (SMR) that makes use of continuous conduction waveform of the input supply current is suggested. Continuous conduction is achieved by the hysteresis current control (HCC) technique. This three-phase SMR operates at close to unity power factor and has reduced current stresses on the switching devices because of the continuous nature of input current. The conduction period considered for the rectifier diodes is 180°. Digitally simulated performance results are provided. Selected experimental results demonstrating the SMR operation are also presented     

Stability analysis of a series active filter integrated with adouble-series diode rectifier

This paper deals with a harmonic current-free AC/DC power conversion system which is characterized by the integration of a small-rated series active filter with a large-rated double-series diode rectifier. The stability of the active filter based on feedback control is discussed theoretically, taking into account delay time in the control circuit. As a result, it is revealed that the delay time may produce a bad effect on stability, especially when the power conversion system is installed on a stiff power system with low system inductance. The authors propose a viable way of reducing the effect of delay time on the system stability. Analysis in the frequency domain enables us to know how much the system stability is improved in terms of gain and phase margins. A switching-ripple filter is designed to obtain good filtering performance without affecting the system stability. Experimental results obtained from a 20 kW laboratory system verify the validity of the developed theory, and confirm the viability and effectiveness of the proposed control circuit     

地铁牵引供电PWM整流器智能维护技术

面向应用于地铁牵引供电系统中的PWM整流器的智能诊断技术开展了研究。文中首先围绕影响PWM整流器可靠性最大的直流支撑电容器提出了基于参数拟合以及Miner累积损伤原则的电解电容器损伤预测方法;其次,文中基于PWM整流器直流中近端非金属性短路时短路电流受其交流电抗器抑制,从而无法可靠实现保护的特点,研究了PWM整流器的非金属性短路电流辨识方法;最后,结合PWM整流器对高性能故障诊断以及虚拟仪器技术的支持,基于分层分布思想以及虚拟仪器技术设计了地铁牵引变电所内PWM整流器的综合监控系统,介绍了系统的组成原理并给出了现场故障录波结果。     

A Lyapunov function approach to longitudinal control of vehicles ina platoon

The Lyapunov second method is used to derive a control law that can he used to control the spacing between vehicles in a platoon. A third-order system is adopted to model the vehicle and powertrain dynamics. In addition, the concept of “expected spacing error” is introduced and used to form a Lyapunov function. Then a control law that always decreases the Lyapunov function is selected. A platoon of four vehicles and various scenarios are used to demonstrate the performance of the proposed control law     

Linear control design for a current-injection-based three-phase unity-power-factor rectifier

In this paper, a new control strategy based on the pulsewidth-modulation technique is proposed and applied to an active-current-injection-based unity-power-factor three-phase ac-dc converter. The control circuit of the converter consists of a multivariable inner current regulator and an outer voltage regulator. Based on linear control techniques, the control circuit has been designed. Averaging techniques are used to derive a linear small-signal model of the converter in the frequency domain. Numerical simulations using the Power System Blockset tool of Matlab/Simulink highlight the performance of the proposed control scheme. Experimental results obtained on a 2-kW prototype validate the theoretical approach described in the paper.     

基于改进型PR调节器的三相PWM整流器控制

应用三相PWM整流器在两相静止坐标系下电流矢量αβ分量的可解耦控制,解决了传统的基于两相旋转坐标系下三相PWM整流器控制系统电流矢量dq分量无法解耦控制的问题,提高了系统的控制性能。且采用改进型PR调节器控制代替传统的PI调节器控制能够对指定频率的交流信号实现稳态无静差跟踪控制,有效抑制低次谐波和高次谐波;相比于传统PR调节器对于系统波动过于敏感的特点,改进型PR调节器在能够保持谐振频率处的敏感度和高增益的基础上,可以增强系统稳定性。对此系统进行Matlab/Simulink仿真分析,验证了该方法的可行性。     

A novel simplified space-vector-modulated control scheme forthree-phase switch-mode rectifier

A novel simplified control scheme for a three-phase switch-mode rectifier is proposed in this paper. The proposed control scheme is based upon a load-conductance rectifier controller, in which reference current signals are obtained. The goal to follow the reference current is converted to follow a reference voltage. A simplified control scheme utilizing space-vector modulation is developed to calculate the duty ratio required to synthesize the reference voltage. The proposed scheme has the advantage of space-vector modulation with fast dynamic response and is simple enough to be implemented in a single-chip microprocessor 80196MC