PWM Voltage Source Inverter Research Articles

Fuzzy logic field oriented control of double star induction motor drive

An indirect field oriented control of a double star induction motor drive with a conventional PI and fuzzy logic controller based on four rules is presented in this paper. To realize a control of this motor, a DC supply and a PWM voltage source inverter (VSI) are introduced. Performance of the proposed control schemes under load disturbances and parameter variations is studied through simulations. The simulation results regarding the speed response with both controllers are presented and discussed.

Modeling and Analysis of Leakage Currents in PWM-VSI-Fed PMSM Drives for Air-Conditioners with High Accuracy and within a Wide Frequency Range

Leakage currents occur in pulse-width-modulated voltage source inverter (PWM-VSI)-fed permanent magnet synchronous motor (PMSM) drives for air-conditioners, which seriously affect system safety and operation performance. High accuracy modeling and prediction of leakage currents are key issues for the design and implementation of air-conditioning products. In this study, the generation mechanism of leakage currents is discussed. A systematic modeling approach of leakage currents is proposed, including the modeling of leakage current sources and leakage current paths. By using the proposed approach, the complete model of leakage currents in PWM-VSI-fed PMSM drives for air-conditioners has been developed based on the extraction of all parameters. A comparison between the simulated leakage currents based on the developed model and measured leakage currents in the outdoor unit of an air-conditioning product is conducted. The comparison verifies the effectiveness of the proposed modeling approach, and the developed model exhibits high accuracy within a wide frequency range.

Photovoltaics System for Maximum Output Control

In this thesis, a boost chopper using PV (Photovoltaics) system and PWM (Pulse Width Modulation) voltage type power converter were constructed to provide a pleasant environment to the patients in the hospital wards by controlling temperature, humidity and air-conditioning & heating. For the stable modulation of solar cell, synchronizing signal and control signal were processed using one chip microprocessor. Power converter system was constructed with booster chopper and voltage source inverter and test was carried out for both devices. Constant voltage control method was used to track a maximum power point at boost converter control. For the inverter control, synchronizing signal and control signal were processed by microprocessor for the stable modulation according to the switching theory of SPWM (Sinusoidal Pulse Width Modulation) and directions to each sector. Test was carried out for inverter control using SPWM control method. In addition, grid voltage was detected and this grid voltage and inverter output were operated at the same phase for the phase locking with PWM voltage source inverter so that surplus power could be linked to grid. This characteristic was applied on the temperature and humidity sensors in the general buildings and buildings having specific purposes such as hospitals. The good dynamic characteristic of inverter could be obtained by these applications. Also, PWM voltage inverter maintains a high power factor and low-frequency harmonic output so that power can be supplied in the load as well as system.

High-Performance Control of Three-Phase Four-Wire DVR Systems using Feedback Linearization

Power quality is a critical issue in distribution systems, where a dynamic voltage restorer (DVR) is commonly used to mitigate the voltage disturbances for loads. This paper deals with a nonlinear control for the three-phase four-wire (3P-4W) DVR under a grid voltage unbalance and nonlinear loads in the distribution system, where a novel control scheme based on the feedback linearization technique is proposed. Through feedback linearization, a nonlinear model of a DVR with a PWM voltage-source inverter (VSI) and LC filters is linearized. Then, the controller design of the linearized model is performed by applying the linear control theory, where the load voltages are kept constant by controlling the d-q-0 axis components of the DVR output voltages. To keep the load voltage unchanged, an in-phase compensation strategy is employed, where the load voltages are recovered to be the same as the previous voltage without a change in the magnitude. With this strategy, the performance of the DVR becomes faster and more stable even under unbalanced source voltages and nonlinear loads. The validity of the proposed control strategy has been verified by simulation and experimental results.

USING HYBRID POWER FILTER TO MITIGATE CURRENTS AND VOLTAGES HARMONICS IN THREE PHASE SYSTEM

This paper describes different power quality problems in distribution systems and their solutions with power electronics based equipment. A hybrid power filter in combined system of shunt passive and series active power filter has been designed and simulate with Matlab/Simulink. This filter is a three level PWM voltage source inverter and we use a fuzzy logic controller algorithm to control the harmonic voltages. The viability of the proposed algorithm is validated in this work. This hybrid power filter is able to compensate the reactive power (showed that source voltage is sinusoidal and in phase with source current), and harmonics (voltage & current) for three phase of the non linear load current proposed with RL and RC load. The proposed solution has achieved an improvement of power quality in distribution system specifically the reduction of currents and voltages harmonics, we see that through the values of THDI and THDV that are still below the IEC (61000) standard after filtering.

The Effect of PWM on Rotor Eddy-Current Losses in High-Speed Permanent Magnet Machines

High-speed permanent magnet machines, supplied by pulsewidth modulation (PWM) voltage source inverters, operate with distorted stator currents. Harmonics present in these stator currents deteriorate the machine performance by generating losses. Mostly, these losses are following the machine design using a transient finite-element model. The precise measurement of these rotor eddy-current losses is extremely difficult, hence, only a few papers provide convincing comparisons between predictions and measurements. This paper presents a fast and precise analytical approach, verified with measurements, to consider rotor losses of machines, supplied by PWM voltages, already during the design procedure.

An integrated Control Approach and Power Management of Stand-alone Hybrid Wind/PV/Battery Power Generation System with Maximum Power Extraction Capability

The production of electricity from renewable energy sources likewind and photovoltaic energy has increased in recent years, due to en -vironmental problems and the shortage of traditional energy sources.In this article we present a detailed mathematical model and a controlscheme for hybrid wind and PV based DG system with battery and max-imum power extraction capability for isolated mode of operation. Thewind power generation system uses wind turbine (WT), a permanentmagnet synchronous generator (PMSG), a three-phase diode rectifierbridge, DC/DC boost converter with maximum power point tracking(MPPT) controller. The PV generation system uses PV array, a boostconverter with maximum power point tracking controller. Both sourcesand battery are connected to common dc bus with a dc link capacitorand supply power to load through PWM voltage source inverter. Theoverall control system consists of MPPT controller for both Wind andPV power system, a bi-directional dc-dc converter controller for batteryenergy storage management and load side inverter controller for volt -age and frequency regulation. Control strategies for individual systemcomponents of the proposed system are designed with a view to achievean acceptable level of voltage and frequency regulation while extract -ing the maximum power from wind and PV system. The performanceof the developed hybrid system is investigated in terms of voltage andfrequency regulation capability under changing wind, solar irradiation and variable load conditions.

Open-circuit fault detection and diagnosis in pulse-width modulation voltage source inverters based on novel pole voltage approach

In this paper, fault detection and an isolation technique for an insulated-gate bipolar transistor open-circuit fault in a voltage source inverter are presented. This technique consists of analysing the pole voltage and providing the detection and the location of simple, simultaneous and multiple faults. Open-circuit faults can be detected by sensing the pole voltage of each leg and comparing it with the theoretical one. To improve the calculation speed and reliability of this technique and to avoid false diagnosis alarms, the fault detection and isolation scheme is based on a novel model of pole voltage taking into account the time delays due to the turn-on and turn-off process of the power switches. This method reduces the detection time and is applied for open-loop or closed-loop faults in a transient or steady state.

A Method for Measuring Torque of Squirrel-Cage Induction Motors Without Any Mechanical Sensor

This paper presents a method for estimating the torque of three-phase squirrel-cage induction motors. The method is not invasive, since it does not rely on mechanical sensors and only the measurement of the stator current is required. The slip and the rotational speed of the motor are estimated from the spectrogram of the stator current signal either in stationary or in nonstationary operating conditions. The torque is estimated from the ratio of the estimated slip and the rated one. A test platform equipped with a rotational speed sensor and a dc motor for measuring the torque of a three-phase induction motor fed by a pulsewidth-modulated voltage source inverter operating under scalar and vector control was implemented to verify the correctness of the proposed method. The validity of the proposed approach is demonstrated by the close agreement between the estimated values of the speed and torque obtained with the proposed method and the ones that are obtained from direct measurement.

Analytical Formulas for Phase Voltage RMS Squared and THD in PWM Multiphase Systems

The analysis and assessment of the pulsewidth modulation (PWM) techniques is commonly based on the comparison of the total harmonic distortion (THD) results. THD is usually calculated by application of the Fourier transformation and by taking a limited number of harmonics into the consideration. In this paper, derivation of analytical formulas for the phase voltage THD is presented. The considered system is a symmetrical multiphase star-connected load, supplied from a multilevel pulsewidth-modulated voltage-source inverter (VSI, three-phase case is also covered). The solution is based on the Parseval's theorem, which links frequency spectrum and time domain through the average power (i.e., root-mean-square (rms) squared value) of the signal. The assumption throughout the derivations is that the ratio of the switching to fundamental frequency is high. Derivations are based on the integration of the power of the PWM signal in a single switching period over the fundamental period of the signal. Only ideal sinusoidal reference voltages are analyzed, and no injection of any type is considered. Formulas for phase voltage THD for any number of phases are derived for two- and three-level cases, for the most commonly used carrier-based methods. Comparison of the analytically obtained curves with simulation and experimental results shows a high level of agreement and validates the analysis and derivations.

Solar-Based Boost Differential Single Phase Inverter

This paper depicts about a power conversion circuit of a Pulse-width modulated (PMW) voltage source inverter known as a Solar-based boost differential single phase inverter. The total harmonic distortion of 67.12% found in an open loop Solar-based boost differential inverter is reduced down to 22.37% in closed loop system with the aid of Proportional –integral-Differential (PID) voltage controller. The transient stage of the proposed system takes conical shape before it reaches its steady state. The core characteristics of this type of inverter are: it engenders an ac output voltage that is greater than the dc voltage which is not obtained in conventional inverter, it trims down the many stages of power conversions found in other boost converters to one stage, it mitigates the ripple contents of the input voltage and current concurrently and finally, it is portable. This research also shows the disparity between the simulated results of open loop and closed loop of boost differential inverter systems. The dc power source is photovoltaic cell. The maximum power point tracker is in-cooperated in capturing the maximum power from the sun. The proposed topic has its applications in homes, offices and more in industries.

A Tactical Chaos based PWM Technique for Distortion Restraint and Power Spectrum Shaping in Induction Motor Drives

The pulse width modulated voltage source inverters (PWM-VSI) dominate in the modern industrial environment. The conventional PWM methods are designed to have higher fundamental voltage, easy filtering and reduced total harmonic distortion (THD). There are number of clustered harmonics around the multiples of switching frequency in the output of conventional sinusoidal pulse width modulation (SPWM) and space vector pulse width modulation (SVPWM) inverters. This is due to their fixed switching frequency while the variable switching frequency makes the filtering very complex. Random carrier PWM (RCPWM) methods are the host of PWM methods, which use randomized carrier frequency and result in a harmonic profile with well distributed harmonic power (no harmonic possesses significant magnitude and hence no filtering is required). This paper proposes a chaos-based PWM (CPWM) strategy, which utilizes a chaotically changing switching frequency to spread the harmonics continuously to a wideband and to reduce the peak harmonics to a great extent. This can be an effective way to suppress the current harmonics and torque ripple in induction motor drives. The proposed CPWM scheme is simulated using MATLAB / SIMULINK software and implemented in three phase voltage source inverter (VSI) using field programmable gate array (FPGA).

Dual open-end stator winding induction machine fed by redundant voltage source inverters

In this paper, the authors propose the availability analysis of a dual open-end stator windings asynchronous machine. Each open-end stator winding is supplied by two PWM voltage source inverters. The active and passive redundancy of the inverters improves reliability, availability, and safety of the system since the loss of inverter losses does not stop the machine. Indeed, for active redundancy, in the case of failure of the inverter, the corresponding winding is disconnected and the other winding is supplied by the two healthy inverters. For passive redundancy, one winding is fed by two inverters and the two others are waiting; in the case of failure inverter, the roles will be reversed. Simulation results are carried out to show the ability of a fault-tolerant architecture.

Voltage Sources in 2D Fourier-Based Analytical Models of Electric Machines

The importance of extensive optimizations during the design of electric machines entails a need for fast and accurate simulation tools. For that reason, Fourier-based analytical models have gained a lot of popularity. The problem, however, is that these models typically require a current density as input. This is in contrast with the fact that the great majority of modern drive trains are powered with the help of a pulse-width modulated voltage-source inverter. To overcome that mismatch, this paper presents a coupling of classical Fourier-based models with the equation for the terminal voltage of an electric machine, a technique that is well known in finite-element modeling but has not yet been translated to Fourier-based analytical models. Both a very general discussion of the technique and a specific example are discussed. The presented work is validated with the help of a finite-element model. A very good accuracy is obtained.

A DFIM Sensor Faults Multi-Model Diagnosis Approach Based on an Adaptive PI Multiobserver—Experimental Validation

This paper studies the problem of diagnosis strategy for a doubly fed induction motor (DFIM) sensor faults. This strategy is based on unknown input proportional integral (PI) multiobserver. Thecontribution of this paper is on one hand the creation of a new DFIM model based on multi-model approach and, on the other hand, the synthesis of an adaptive PI multi-observer. The DFIM Volt per Hertz drive system behaves as a nonlinear complex system. It consists of a DFIM powered through a controlled PWM Voltage Source Inverter (VSI). The need of a sensorless drive requires soft sensors such as estimators or observers. In particular, an adaptive Proportional-Integral multi-observer is synthesized in order to estimate the DFIM’s outputs which are affected by different faults and to generate the different residual signals symptoms of sensor fault occurrence. The convergence of the estimation error is guaranteed by using the Lyapunov’s based theory. The proposed diagnosis approach is experimentally validated on a 1 kW Induction motor. Obtained simulation results confirm that the adaptive PI multiobserver consent to accomplish the detection, isolation and fault identification tasks with high dynamic performances.

Modelling and simulation of a carrier-based PWM voltage source inverter for a nine-phase induction machine drive

The analysis of a carrier-based PWM two-level voltage source inverter for a nine-phase induction machine drive system is presented in this paper. Methods for generating zero-sequence signals during balanced and unbalanced condition are established. Simulation results for the analysis are presented. Two fault conditions involving the voltage source inverter and the nine-phase squirrel cage induction machine load are investigated. For the two fault scenarios considered, the effects on the performance characteristics of the induction machine load are highlighted. The simulation results obtained show that the two imbalance conditions considered result in substantial oscillations on the electromagnetic torque of the machine with attendant reduction in the torque rating. There is also large slip in the rotor speed.

High-Performance Fault Diagnosis in PWM Voltage-Source Inverters for Vector-Controlled Induction Motor Drives

This paper proposes a simple method for single switch and double switches open-circuit fault diagnosis in pulsewidth-modulated voltage-source inverters (PWM VSIs) for vector-controlled induction motor drives, which also applies to secondary open-circuit fault diagnosis. According to the phase angle of one phase current, the repetitive operation process of VSI is evenly divided into six operating stages by certain rules. At each stage, only three of the six power switches exert a vital influence on this operation and the others make a negligible influence. An open-circuit fault of power switches introduces the repetitive current distortions, whose period is identical to that of the three-phase currents. The current distortions appear at faulty stages and disappear at healthy stages. The stage is determined by recalculating the current vector rotating angle. The d - and q-axis current repetitive distortions are applied to the detection of faulty switches due to its simplicity and fair robustness, while the faulty stages are used for the identification of faulty switches. The simulations and experiments are carried out and the results show the effectiveness of the proposed method.

Short-Circuit Fault Diagnosis for Three-Phase Inverters Based on Voltage-Space Patterns

This paper introduces a fault detection and isolation (FDI) method for faulty metal-oxide-semiconductor field-effect transistors in a three-phase pulsewidth-modulated (PWM) voltage source inverter. Short-circuit switch faults are the leading cause of failure in power converters. It is extremely vital to detect them in the early stages to prevent unwanted shutdown and catastrophic failures in motor drives and power generation systems. Against the common FDI methods for power electronic inverters that use phase currents and PWM gate control signals, the proposed method only uses the inverter output voltages. This method analyzes the PWM switching signals in a time-free domain that is called the voltage space. For a healthy inverter, the projection of the state transitions in the voltage space results in a cubic pattern. Each short-circuit switch fault uniquely changes the voltage-space pattern that allows isolating the faulty switch. The fault detection time is only within one PWM carrier period, which is significantly faster than current-based conventional methods. The FDI result does not depend on the load, the PWM switching frequency, and the feedback loop. This method can address the reliability problem of multilevel inverters in renewable electrical generation systems and can dramatically reduce the number of required sensors.

A Simple and Direct Dead-Time Effect Compensation Scheme in PWM-VSI

This paper presents the direct compensation of the switching interval error of the effective voltage vectors by the dead time of a pulsewidth modulation voltage source inverter (PWM-VSI). The output voltages of a three-phase PWM-VSI are distorted and have voltage errors from the dead time to avoid the shoot-through of inverter arms and the time delay of the gate drive. Voltage distortion increases the harmonics of the output voltages and decreases control performance. This paper presents a simple and direct compensation technique to solve this problem in a three-phase VSI. The practical switching output voltages are determined by the dc-link voltage, the switching signals of each phase, the dead time, the time delay, and the current polarities of each phase. For these reasons, output voltage errors are not constant. In order to analyze the dead-time effect in the actual switching voltages of each phase, the practical switching voltages in a sampling period of a space vector PWM (SVPWM) method are calculated according to the current polarity. In the calculation, the dead time, the time delay of devices, and the voltage drops on power devices are included to consider nonlinear voltage distortion. From these practical switching voltages during the switching intervals in a sampling period, the average output voltages of each phase can be derived, and the output voltage errors between the voltage commands and the average output voltages of each phase are obtained. The SVPWM switching intervals of each phase can be derived by the average output voltages that are calculated according to the current polarity and nonlinear voltage distortion to compensate for the output voltage errors. With the simple detection of the current polarity, the practical errors of the switching intervals of each phase can be compensated by the addition of the compensated switching time. Simulation and experimental results validating the proposed compensation method are presented in this paper.

Approaches to Suppressing Shaft Voltage in Non-Insulated Rotor Brushless DC Motor driven by PWM Inverter

The voltage source PWM inverter generally used to drive the air conditioning (A/C) fans has been posing a large issue that the bearings in air conditioning fan motors are highly possible to be corroded electrically. Potential difference called shaft voltage is generated between inner and outer rings of the bearings due to inverter switching. The shaft voltage causes bearing lubricant breakdown dielectrically. As a result, bearing current is caused. This current causes the bearing corrosion. In previous work, we demonstrated that the shaft voltage can be reduced by using an insulator inserted between the outer and inner cores of the rotor in an air conditioning fan motor without grounding. This paper proposes the other countermeasure for reducing the shaft voltage in fan motors. The countermeasure which adds a capacitor between the brackets and the stator core is effective even for fan motors with non-insulated rotor. The effectiveness is confirmed by both simulated and experimental results.