Dual-PWM Three-Level Voltage Source Converter Based on SVPWM

In this paper, a winding inter-turn fault (ITF) diagnosis algorithm for electrical machines in integrated motor and drive (IMD) systems is proposed based on impedance analysis using space voltage vectors. An ITF alters the stator resistance, causing an imbalance in the motor’s impedance depending on the phase connection. This impedance asymmetry can be effectively utilized for fault diagnosis. However, in IMD systems, direct impedance measurement through mechanical terminal access is difficult due to the integrated structure. To address this, the impedance of the induction motor is analyzed electrically, without the need for physical disconnection, allowing practical implementation within integrated systems. The specific phase angle of the space voltage vector in the three-phase inverter is analyzed to replicate the electrical conditions of mechanical terminal configurations. Based on this approach, a fault diagnosis algorithm was developed by analyzing the variation in stator current and impedance with respect to space voltage vector angles. The effectiveness of the proposed method was verified through experimental validation using a 12kW three-phase induction motor and terminal box.

This paper introduces control system design based softwares, SIMNON and MATLAB/SIMULINK, for power electronics system simulation. A complete power electronics system typically consists of a rectifier bridge along with its smoothing capacitor, an inverter, and a motor. The system components, featuring discrete or continuous, linear or nonlinear, are modeled in mathematical equations. Inverter control methods,such as pulse-width-modulation and hysteresis current control, are expressed in either computer algorithms or digital circuits. After describing component models and control methods, computer programs are then developed for complete systems simulation. Simulation results are mainly used for studying system performances, such as input and output current harmonics, torque ripples, and speed responses. Key computer programs and simulation results are demonstrated for educational purposes.

A new constant-voltage constant-current ac power regulator is proposed. Our original Variable Capacitance Device of linear reactance device is utilized in the power stage. This circuit theoretically makes no distortion of output voltage waveform and a high efficiency can be obtained. For output voltage/current control and input power-factor correction, two Variable Capacitance Devices were employed as linear capacitor. Two dc-dc converters were used for high-speed driver of these devices. The unity input power factor can be obtained all over the constant-voltage region and the constant-current region. Input current of the proposed power supply becomes almost zero at no load and at short-circuit load.

A single-phase bi-directional neutral point clamped AC/DC converter with the functions of being a power factor corrector and an active filter is proposed, to reduce current harmonics and compensate for the reactive power current drawn from a nonlinear load. Based on neutral point clamped topology, the voltage stress of the power device is clamped to half the DC bus voltage instead of the full DC link voltage in a conventional half and full bridge pulse-width modulation (PWM) AC/DC converter. The line current tracking, DC link voltage regulation and neutral point voltage compensation are performed by an inner loop current controller, an outer loop voltage controller and a voltage balance compensator, respectively. To generate a three-level PWM pattern on the AC terminal of the AC/DC converter, a region detector of the mains voltage is employed. Based on the proposed control scheme, the converter can draw a clean sinusoidal line current with unity input power factor and achieve DC bus voltage regulation. The effectiveness of the proposed AC/DC converter with the function of power factor corrector as well as active filter is confirmed by the experimental results.

This study presents a novel control strategy of discrete variable frequency (DVF) based on space voltage vectors for a three-phase induction motor (IM) soft-starting. The proposed strategy is developed in four steps. First, conducting states of the three-phase thyristor circuits are analysed, and the formation mechanism of space voltage vectors is also demonstrated. Then, DVF control strategy of IM based on hexagon flux linkage loci is expounded categorically, which contains frequency f/7 control, frequency f/4 control, frequency f/3 control and ramp voltage control. Next, under two-phase stationary coordinate system, stator flux equation of IM is derived, and the decrease in stator flux when zero-vector voltage working is calculated accurately. In the end, an experimental system of IM based on three-phase thyristor circuits is constructed, and the experimental results are dealt with and compared with the usual ramp voltage technique. The study results show that IM driven by the proposed strategy can steadily operate at the preset discrete frequency, and the effective value of starting current of IM can be decreased by nineteen percent. The experimental results verify the conclusions.

This paper propose a improved direct torque control(DTC) system for improving operation of five-phase squirrel-cage induction motor(IM). A five-phase IM drives present unique characteristics due to the additional degrees of freedom and also drives possess many others advantage compared with the traditional three-phase motor drive system, such as reducing a amplitude of torque pulsation and increasing the reliability. In order to maximize the torque per ampere, the proposed motor has concentrated windings and the produced back-electromotive force(EMF) is almost trapezoidal, and the motor is supplied with the combined sinusoidal plus third harmonic of currents, there is necessary to controlled 3rd harmonic current. Also a DTC method is advantageous when it is applied to the five-phase IM, because the five-phase inverter provides 32 space vectors in comparison to 8 space voltage vectors into the three-phase inverter drive system. For presenting the superior performance of the proposed DTC, experimental results of speed control are presented using a 32-bit fixed point TMS320F2812 DSP with 1.5[hp] IM.

In this paper, a single-phase to three-phase converter is proposed to provide variable output voltage and frequency. The proposed topology employs only six IGBT switches, which form the front-end rectifier and the output inverter for the one step conversion from single-phase supply to output three-phase supply. The front-end rectifier permits bidirectional power flow and provides excellent regulation against fluctuations in source voltage. Moreover, it incorporates active input current shaping feature. An easy method to implement control strategy is proposed. This control strategy ensures nearly unity input power factor with sinusoidal input current over the operating range. Based on sensorless vector control technique, the proposed converter is used for the speed control of the three-phase induction motor. A low cost motor drive can be achieved using the proposed converter and control technique. Simulation and experimental results are carried out to analyse and explore the characteristics of the low cost drive system.

A harmonic resonance phenomenon associated with high power GTO current source inverter drives is investigated. It is indicated in this paper that the resonance is caused by the parallel connection of output capacitor and induction motor, and it is excited by harmonics in the inverter output current. A general solution to eliminating the harmonic resonance is discussed. Two practical problems, the effects of DC link current ripple on inverter current harmonics and the effects of noncharacteristic harmonics on the resonance, are investigated. Solutions to these problems are proposed. Simulation and experimental results on a 1250 HP drive are provided to verify the analysis. >

Among the total energy consumed by presently installed utilities, pumping systems contributes nearly 30% of them that are controlled through induction motor. The flow rate of centrifugal pump is directly proportional to the speed of induction motor. Induction motor based electric drives are a complex nonlinear system to control due to their varying nature of speed with respect to changes in load. Thus, controllers are required for the speed control and performance enhancement of the induction motors. In this paper, a comparison of various controllers is discussed for the flow rate control of the pumping system. Among all the conventional controllers the proportional integral derivative (PID) is the mostly preferred for induction motor speed control. However, high overshoot, fixed gain constants and sluggish response are the disadvantages of the PID controller. So, automatic gain tuned PI controllers (i.e., adaptive PI controllers) are introduced to overcome the drawbacks of the conventional PID controllers. Further advancements in the field of artificial intelligence lead to the development of fuzzy logic based controllers. These controllers are simple, compatible and can be modelled without detailed mathematical model of the system. Thus, they are gaining more popularity than other controllers. The rules and membership functions (MFs) are responsible for performance of fuzzy logic controllers are designed using trial and error method. The result comparison of all the controllers is presented and the performance of each controller is analyzed. From the observations, fuzzy logic controller provides better performance than the conventional controllers.

In this paper, a multilevel dodecagonal voltage space vector structure with nineteen concentric dodecagons is proposed for the first time. This space vector structure is achieved by cascading two sets of asymmetric three-level inverters with isolated H-bridges on either side of an open-end winding induction motor. The dodecagonal structure is made possible by proper selection of dc link voltages and switching states of the inverters. The proposed scheme retains all the advantages of multilevel topologies as well as the advantages of dodecagonal voltage space vector structure. In addition to that, a generic and simple method for calculation of pulsewidth modulation timings using only sampled reference values ( $v_\alpha$ and $v_\beta$ ) is proposed. This enables the scheme to be used for any closed-loop application such as vector control. In addition, a new method of switching technique is proposed, which ensures minimum switching while eliminating the fifth- and seventh-order harmonics and suppressing the eleventh and thirteenth harmonics, eliminating the need for bulky filters. The motor phase voltage is a 24-stepped waveform for the entire modulation range thereby reducing the number of switchings of the individual inverter modules. Experimental results for steady-state operation, transient operation, including start-up have been presented and the results of fast Fourier transform analysis is also presented for validating the proposed concept.

A new virtual voltage space vector based direct torque control (DTC) scheme that can eliminate varying common mode voltages occurring in voltage source inverter fed induction motor (IM) drives is proposed in this paper. In this scheme, six virtual active voltage space vectors are employed to implement the direct torque control of the induction motor drive without generating varying common mode voltage. This scheme can be implemented using a conventional 2-level inverter and does not require any additional hardware. The proposed scheme is validated by simulation using Matlab-Simulink software and then experimentally validated on a laboratory prototype comprising of an induction motor drive fed by a two-level voltage source inverter and a digital signal processor TMS320F28069M for the implementation of the controller.

Interior permanent magnet synchronous motors (IPMSMs) which are driven by matrix converters have many advantages, including one‐stage power conversion, high efficiency, bidirectional power transfer, near unity input power factor, and low input current harmonics. However, the virtual DC‐link voltages of matrix‐converters vary from 0.866 to and the current commutations of matrix‐converters create serious three‐phase stator harmonic currents as well. Moreover, matrix‐converter‐based IPMSM drive systems, in general, have very large external loads, which require advanced control methods. To solve these problems, two adaptive controllers, including a model reference adaptive controller and a self‐tuning controller, are investigated in this article for matrix‐converter PMSM drive systems. From the experimental results, the proposed two adaptive speed controllers provide excellent dynamic responses, which are superior to PI speed controllers, including faster transient responses, better tracking abilities, and greater robustness. As a result, this proposed matrix‐converter‐based IPMSM drive system is very suitable in industrial applications.

Single stage AC/DC converters based on series-parallel resonant circuit and operating above the resonance frequency provide high input power factor. However, with conventional variable frequency control, zero voltage switching may be lost in some operating conditions. In this paper two control techniques for resonant converter operating above resonance frequency are compared. These control techniques ensure zero voltage switching in all operating points allowing operation at high frequencies. A design procedure is suggested for the selection of resonant circuit parameters. Finally experimental results from a 500 W power factor corrected AC/DC power supply are given to verify the predicted results.

A novel active power factor correction method for power supplies with three-phase front-end diode rectifiers is proposed and analyzed. The implementation of this method requires the use of an additional single switch boost chopper. The combined front-end converter draws sinusoidal AC currents from the AC source with nearly unity input power factor while operating at a fixed switching frequency. It is shown that when the active input power factor correction stage is also used to regulate the converter DC bus voltage, the converter performance can improve substantially in comparison with the conventional three-phase AC-to-DC converters. These improvements include component count reduction, simplified input synchronization logic requirements, and smaller filter refractive components. Theoretical results are verified experimentally. The proposed method has the disadvantage of substantially increasing the current stresses of the switching devices and the high-frequency ripple content of the prefiltered AC input currents. >

This paper presents the conception and analysis of a switch-mode power supply (SMPS) with desirable characteristics of high-frequency isolation, high input power factor, low harmonic distortion, and high efficiency. Nearly unity input power factor can be obtained by using an interleaved boost converter associated with a nondissipative snubber, as high efficiency of the ac–dc front-end stage results. Additionally, a soft-switching full-bridge topology performs the dc–dc conversion, providing isolation to the SMPS by using a high-frequency transformer. By cascading both stages, the aforementioned characteristics are achieved. Theoretical background on each one of the converters is presented, and experimental results obtained from a laboratory prototype are presented and discussed in order to validate the proposal. In addition, the evaluation tests demonstrate the operation with nearly unity power factor, high efficiency, and good dynamic response over a wide load range.