In this paper, a proposed control strategy is presented to improve the performance of the pulse width modulation (PWM) boost type rectifier when operating under different supply voltage conditions (balanced, unbalanced, and distorted three-phase supply voltages). The proposed control strategy is divided into two parts, the first part is voltage controller and the second part is current controller. In the voltage controller, Repetitive Controller (RC) is used to reduce the even order harmonics in the regulated output dc voltage so small output capacitor (filter) is used instead of large capacitor. RC also reduces the even order harmonics which appear in the reflected dc current (I MAX ), this leads to reduce the odd order harmonics which appear in the input currents. While in the current controller, Enhanced Phase Locked Loop (EPLL) technique is used to obtain sinusoidal and balanced three phases, to construct the reference currents, which are in phase with the fundamental supply voltages. Therefore, the supply-side power factor is kept close to unity. A proportional controller is used to give excellent tracking between the line and the reference currents. The complete system with the proposed control strategy are simulated using Matlab/Simulink. The results for the complete system using repetitive voltage controller are obtained and compared to the results of the system with the conventional voltage controller (Proportional-Integral (PI) controller connected in series with a Low Pass Filter (LPF)). The results with the repetitive controller show better response and stable operation in the steady state under different input voltage conditions, as well as in the transient response under changing the load condition. — Enhanced Phase Locked Loop,Repetitive Controller,Three-Phase PWM Boost Rectifier, Proportional-Integral controller. I. INTRODUCTION The boost type PWM rectifier has been increasingly employed in recent years since it offers the possibility of a low distortion line current withnear unity power factor for any load condition. Another advantage over traditional phase-controlled thyristor rectifiers is its capability for nearly instantaneous reversal of power flow. Unfortunately, the features of the PWM boost type rectifier are fully realized only when the supply three phase input voltages are balanced. It has been shown that unbalanced input voltages cause an abnormal second order harmonic at the dc output voltage, which reflects back to the input causing third-order harmonic current to flow. Next, the third-order harmonic current causes a fourth-order harmonic voltage on the dc bus, and so on. This results in the appearance of even harmonics at the dc output and odd harmonics in the input currents. An attempt was made to reduce low order harmonics at the input and the output of the PWM Boost Type Rectifier under unbalance input voltages [1]. The authors in [2] used two synchronous reference frames: a positive- sequence current regulated by a
Soft commutation techniques have been of great interest during the last few years in power supply switching applications. The recently developed Zero-Voltage transition (ZVT) and Zero-Current transition (ZCT) pulse width modulation (PWM) technique incorporated soft-switching function into PWM converters, so that the switching losses can be reduced with minimum voltage/current stresses and circulating energy. The ZCT technique can significantly reduce the switch turn-off loss which is usually the dominant switching loss in high-power applications. In this paper the steady state analysis and design of the ZCT PWM boost converter are introduced. Control and drive circuit have been designed to drive a 100 Watt ZCT PWM boost converter to experimentally investigate its features and characteristics.
This paper presents a proposed configuration of paralleling scheme PWM DC/DC buck converter. The topological structure and operation principles are presented. A Bode plot diagram technique is used to study the stability of the scheme for different values of controller parameters and with a number of parallel modules. It is found that the results are confidence, and the proposed scheme can be used in high power applications by increasing the number of parallel modules.
Soft-switching technique can substantially improve the performance of power converters, mainly due to the increase of switching frequency, that result in better modulation quality. This is more concerned particularly in the high power applications, where devices [gate turn off (GTO) or something else similar) can not operate over a few hundreds of hertz in conventional hard switching converter structures. In this paper, design and analysis of moderate power ZCT three-phase PWM inverter has been presented. Also, the designed inverter and its novel control circuit is implemented experimentally to investigate its characteristics with this new zero-current transition ZCT technique.
This Paper presents a novel hardware design methodology of digital control systems. For this, instead of synthesizing the control system using Very high speed integration circuit Hardware Description Language (VHDL), LabVIEW FPGA module from National Instrument (NI) is used to design the whole system that include analog capture circuit to take out the analog signals (set point and process variable) from the real world, PID controller module, and PWM signal generator module to drive the motor. The physical implementation of the digital system is based on Spartan-3E FPGA from Xilinx. Simulation studies of speed control of a D.C. motor are conducted and the effect of a sudden change in reference speed and load are also included.
The multilevel inverter is attracting the specialist in medium and high voltage applications, among its types, the cascade H bridge Multi-Level Inverter (MLI), commonly used for high power and high voltage applications. The main advantage of the conventional cascade (MLI) is generated a large number of output voltage levels but it demands a large number of components that produce complexity in the control circuit, and high cost. Along these lines, this paper presents a brief about the non-conventional cascade multilevel topologies that can produce a high number of output voltage levels with the least components. The non-conventional cascade (MLI) in this paper was built to reduce the number of switches, simplify the circuit configuration, uncomplicated control, and minimize the system cost. Besides, it reduces THD and increases efficiency. Two topologies of non-conventional cascade MLI three phase, the Nine level and Seventeen level are presented. The PWM technique is used to control the switches. The simulation results show a better performance for both topologies. THD, the power loss and the efficiency of the two topologies are calculated and drawn to the different values of the Modulation index (ma).
In medium voltage and high-power drive applications, pulse width modulation (PWM) techniques are widely used to achieve effective speed control of AC motors. In real-time, an industrial drive system requires reduced hardware complexity and low computation time. The reliability of the AC drive can be improved with the FPGA (field programmable gate array) hardware equipped with digital controllers. To improve the performance of AC drives, a new FPGA-based Wavect real-time prototype controller (Xilinx ZYNQ-7000 SoC) is used to verify the effectiveness of the controller. These advanced controllers are capable of reducing computation time and enhancing the drive performance in real- time applications. The comparative performance analysis is carried out for the most commonly used voltage source inverter (VSI)-based PWM techniques such as sinusoidal pulse width modulation (SPWM) and space vector pulse width modulation (SVPWM) for three-phase, two-level inverters. The comparative study shows the SVPWM technique utilizes DC bus voltage more effectively and produces less harmonic distortion in terms of higher output voltage, flexible control of output frequency, and reduced harmonic distortion at output voltage for motor control applications. The simulation and hardware results are verified and validated by using MATLAB/Simulink software and FPGA-based Wavect real-time controller respectively.
The paper dells with a modified experimental prototype for pulse-width modulation (PWM) sliding mode control (SMC) applied to a DC-to-DC-boost converter operated in continuous conduction mode (CCM). Experimental results show that the proposed control schme provides good voltage regulation and is suitable for common DC-to-DC conversion purposes. The prototype and its implementation are given in detail. The static and dynamic performances of the The static and dynamic performances of the experimental system are recorded. Experimental results show that the proposed control scheme provides good voltage regulation and is suitable for common DC-to-DC conversion purposes.
In this article, a comparison of innovative multilevel inverter topology with standard topologies has been conducted. The proposed single phase five level inverter topology has been used for induction heating system. This suggested design generates five voltage levels with a fewer number of power switches. This reduction in number of switches decreases the switching losses and the number of driving circuits and reduce the complexity of control circuit. It also reduces the cost and size for the filter used. Analysis and comparison has been done among the conventional topologies (neutral clamped and cascade H-bridge multilevel inverters) with the proposed inverter topology. The analysis includes the total harmonic distortion THD, efficiency and overall performance of the inverter systems. The simulation and analysis have been done using MATLAB/ SIMULINK. The results show good performance for the proposed topology in comparison with the conventional topologies.
In this article, a PD-type iterative learning control algorithm (ILC) is proposed to a nonlinear time-varying system for cases of measurement disturbances and the initial state errors. The proposed control approach uses a simple structure and has an easy implementation. The iterative learning controller was utilized to control a constant current source inverter (CSI) with pulse width modulation (PWM); subsequently the output current trajectory converged the sinusoidal reference signal and provided constant switching frequency. The learning controller's parameters were tuned using particle swarm optimization approach to get best optimal control for the system output. The tracking error limit is achieved using the convergence exploration. The proposed learning control scheme was robust against the error in initial conditions and disturbances which outcome from the system modeling inaccuracies and uncertainties. It could correct the distortion of the inverter output current waveform with less computation and less complexity. The proposed algorithm was proved mathematically and through computer simulation. The proposed optimal learning method demonstrated good performances.
In this paper, the vector-controlled Permanent Magnet Synchronous Motor (PMSM) fed by Indirect Matrix Converter (IMC) is analyzed, designed, and simulated by using the IMC with Carrier Based Pulse Width Modulation (CBPWM). The CBPWM strategy is based on Space Vector Pulse Width Modulation (SVPWM) analysis, it is used to enhance the input current waveform, reduce the complexity of switching signals generation, and to solve the commutation problem. The traditional PMSM drive system is simulated for comparison with proposed drive system. The proposed drive system is compared to the traditional drive system using the Total Harmonic Distortion (THD). The comparison results show that the proposed drive system outperform the traditional drive system by THD different of 1/30 of input current and 1/1.5 of stator current, with high input power factor.
This paper presents a simplified control method for three-phase active power filter by calculating the required reactive and harmonics current of the load. The active power filter needs this current to correct the power factor and eliminate the generated harmonics by nonlinear loads. This method has the advantages of using only one current sensor and effectiveness in achieving the required compensation characteristics. The proposed circuit may be operate at frequencies ranging from 40 to 60 Hz, and it also responds very fast under sudden changes in the load conditions. The considered system is analyzed and a prototype is also developed and tested to demonstrate the performance of the implemented active power filter in the power factor improvement and harmonics elimination. Finally, predicted results are verified experimentally.
The conventional multilevel inverter (MLI) is divided into three types: diode clamped MLI, cascade H Bridge MLI and flying capacitor MLI. The main disadvantage of these types is the higher required number of components when the number of the levels increases and this results in more switching losses, system higher cost, more complex of control circuit as well as less accuracy. The work in this paper proposes two topologies of nonconventional diode clamping MLI three phase nine levels and eleven levels. The first proposed topology has ten switches and six diodes per phase while the second topology has nine switches and four diodes per phase. The pulse width modulation (PWM) control method is used as a control to gate switches. THD of the two proposed topologies are analyzed and calculated according different values of Modulation index (where the power loss and efficiency are obtained and plotted.
Five-phase machine employment in electric drive system is expanding rapidly in many applications due to several advantages that they present when compared with their three-phase complements. Synchronous reluctance machines(SynRM) are considered as a proposed alternative to permanent magnet machine in the automotive industry because the volatilities in the permanent magnet price, and a proposed alternative for induction motor because they have no field excitation windings in the rotor, SyRM rely on high reluctance torque thus no needing for magnetic material in the structure of rotor. This paper presents dynamic simulation of five phase synchronous reluctance motor fed by five phase voltage source inverter based on mathematical modeling. Sinusoidal pulse width modulation (SPWM) technique is used to generate the pulses for inverter. The theory of reference frame has been used to transform five-phase SynRM voltage equations for simplicity and in order to eliminate the angular dependency of the inductances. The torque in terms of phase currents is then attained using the known magnetic co-energy method, then the results obtained are typical.
Among all control methods for induction motor drives, Direct Torque Control (DTC) seems to be particularly interesting being independent of machine rotor parameters and requiring no speed or position sensors. The DTC scheme is characterized by the absence of PI regulators, coordinate transformations, current regulators and PWM signals generators. In spite of its simplicity, DTC allows a good torque control in steady state and transient operating conditions to be obtained. However, the presence of hysterics controllers for flux and torque could determine torque and current ripple and variable switching frequency operation for the voltage source inverter. This paper is aimed to analyze DTC principles, and the problems related to its implementation, especially the torque ripple and the possible improvements to reduce this torque ripple by using a proposed fuzzy based duty cycle controller. The effectiveness of the duty ratio method was verified by simulation using Matlab/Simulink software package. The results are compared with that of the traditional DTC models.