Variable structure approaches for current control in vector‐controlled inverter‐induction motor system

The number of voltage levels available in pulsewidth modulation (PWM) voltage source inverters can be increased by using a split-wound coupled inductor within each inverter leg and interleaved PWM switching of the upper and lower switches. The magnetizing inductance of the symmetrical split-wound inductor filters the high-frequency PWM voltage differences between the upper and lower switches. The same inductor presents a three-level PWM voltage at the inverter output terminals, with the winding leakage inductance being located in series with the low-frequency output current. Deadtime PWM signal delays can be reduced as DC-rail short circuits are not possible: as a result, the quality and voltage range of the PWM output is improved. Since the inductor windings are technically exposed to high-frequency PWM AC voltages with no DC components, device voltage drops help to reduce the buildup of winding DC currents. Theoretical analysis and a sample design case are presented to illustrate how to design suitable inductors for the various topologies. Simulation and experimental results are used to illustrate the operation of the proposed inverter structures.

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.

This paper proposes a new position sensorless control for interior permanent-magnet synchronous motor (IPMSM) drives fed by overmodulation mode pulsewidth modulation (PWM) voltage source inverter. It is attractive to expand the speed range of the IPMSM for application to electric vehicles, electrical household appliances, and so on. An overmodulation mode PWM voltage-source inverter makes it possible to solve problems such as efficiency, wide speed range operation, and so on. Most position sensorless controls based on inverter output voltage knowledge, however, cannot directly be utilized because the voltage reference obtained by the controller is not equal to the inverter output voltage. This paper proposes unknown input observer to estimate rotor position without voltage knowledge, and investigates robustness to inductance variation.

The inverters and control methods are applied in more and more fields with power electronics development. The technology of current hysteretic band PWM is a kind of easy and reliable control method. But the harmonic distortion of load current is big amplitude around switching frequency side band. The paper introduce a Varied Hysteretic-band Current control technique(VHBCC), this method can spreads the spectrum contents of load current around switching frequency side band, reduces the harmonic distortion of load current . At last, The results of simulation prove the method feasible and effective.

This paper proposes an “active common-mode noise canceler” that is capable of eliminating the common-mode voltage produced by a voltage source PWM (pulsewidth modulated) inverter. It generates a compensating voltage which has the same amplitude as, but the opposite phase to, the common-mode voltage produced by the PWM inverter. The compensating voltage is superimposed on the inverter output by a common-mode transformer. As a result, the common-mode voltage applied to the load is canceled completely. The design method of the active common-mode noise canceler is also presented in detail. A prototype has been constructed and tested to verify the effectiveness for an induction motor drive system of 3.7 kW using an IGBT (insulated gate bipolar transistor) inverter. Some experimental results show that the proposed active common-mode noise canceler makes a significant contribution to eliminating the common-mode current or the ground current, and it prevents an electric shock from being received by anyone handling it. © 1998 Scripta Technica, Electr Eng Jpn, 124(3): 64–72, 1998

When calculating the permanent magnet (PM) eddy current loss (ECL) in the interior permanent magnet synchronous machine (IPMSM) under pulse width modulation (PWM) voltage source inverter (VSI) supply, it is very important to take the high frequency harmonic voltages (HFHVs) in the input voltage into consideration because most of the PM ECL in IPMSM with distributed windings is caused by them [1–2]. However, common finite element analysis (FEA) with sinusoidal current source supply isn’t able to take the HTHVs into consideration and the coupled field-circuit time-stepping FEA under PWM VSI supply with fine time step is needed for the calculation, which is very time-consuming especially when conducting 3D FEA to take the end effect and axial segmentation into consideration. A hybrid method with the combination of 2D FEA and analytical method has been proposed in [3] for fast calculating the PM ECL considering axial segmentation. However, the 2D time-stepping FEA with fine time step, which takes several hours for one case study, is still needed for the PM ECL calculation under one load condition with the method proposed in [3]. In this paper, the analytical method in [3] is further developed and applied for the PM ECL calculation of an IPMSM applied in the HEV application [4]. Rather than calculating the PM ECL with the average flux density passing through the PM as input [3], the relationship between arbitrary HFHV and the corresponding PM ECL is established. Hence, the total PM ECLs can be calculated with the FFT results of the input line-line voltage directly without time-stepping FEA at a given load condition.

One of the most common fault in Pulse Width Modulation (PWM) Voltage Source Inverter (VSI) feeding an induction motor is open gate drive of the switching device (IGBT). In addition to these extreme fault cases, there may be less severe faults cases due to improper contact points, problematic solder joints, poor connections etc. Main objective of this work is to develop a rule base that not only can segregate these two different types of fault cases but also can identify the power switch in which such a fault has occurred. Rigorous simulation results using PSIM software for creating all variations of the above mentioned fault cases in a PWM VSI driven induction motor is presented for diagnosing the condition of an inverter. The three phase line currents feeding the motor are recorded and transformed to d-q reference frame using Park's Transformation for further analysis. From d and q current components thus obtained, the mean current vector is calculated. The loci of the mean current vector are plotted on the d-q plane and their patterns are observed. Shapes of these loci have been found to be effective in classifying different fault modes.

Voltage Source Inverters (VSI) fed Induction Motors provide significant applications such as electric traction, evehicles etc., in the field of variable speed utilization. Whenever VSI is operated at constant switching frequency carrier pulse width modulation(PWM), the output voltage and current harmonics in the fast fourier transform (FFT) spectrum locates at switching frequency, and its integral multiples that tends to generate acoustic noises where acoustic noises are intolerable for human beings. Therefore, we propose a new PWM technique, namely modulated frequency triangular carrier-based bus clamping PWM (MFTC-BC-PWM) that derives a better spreading effect which overcomes the issue. The MFTC-BC-PWM is simulated and experimentally verified on TMS320F28379D TI controller and the experimental results depict that the magnitudes of dominant harmonic components have reduced significantly. Moreover, the results show that the inverter losses such as conduction and switching losses are much lower in the proposed technique when compared to the sinusoidal PWM and other conventional space vector PWM techniques.

Voltage source inverter (VSI) is one of the most common types of power converters, which is used in various industries. The energy efficiency indicators of the AVI depend not only on the IGBT or MOSFET-based transistors used in the AVI element, but also on the chosen modulation algorithm.The most commonly used in VSI is pulse width modulation (PWM) and single modulation. The advantage of PWM prior to single modulation is the ability to control the amplitude of the first harmonic of the output voltage and, accordingly, the current required both for scalar and vector control of an asynchronous electric drive.At the same time, the disadvantage of PWM is the need for a higher switching frequency of power switches, which results in higher dynamic losses. In addition, in the PWM mode, VSI at the same load parameters has a smaller amplitude of the first harmonic of the output voltage, and hence less output power.The article proposes the use the mode of overmodulation algorithm in the pulse-width modulation (PWM) mode for a three-level autonomous voltage inverter, which is relatively classical PWM with a modulation factor equal to one, justified and allows to increase the control range of the output power of the VSI, to reduce the dynamic losses in the power switches, to improve the sinusoidal output current, as well as reduce the ripple factor of the input current. Given the dependence of the energy indicators of the VSI on the modulation factor in the mode of overmodulation.In the specialized MelcoSim program from Mitsubishi, the calculation of static and dynamic losses in the power switches of an autonomous voltage inverter in the mode of overmodulation was performed. The dependences of the output power on the modulation coefficient, the dependence of the amplitude of the first harmonic of the output current on the modulation coefficient, the dependence of the coefficient of harmonic distortion of the output voltage on the modulation coefficient, the dependence of the harmonic distortion factor of the output current on the modulation coefficient, and the dependence of the losses in the power switches on the modulation coefficient.

A method of deriving the switching instants of different space vectors in the direct torque control of induction motor drives using pulse width modulated voltage source inverters is described in this paper. The switching instants of different space vectors are determined to reduce torque ripple compared to the commonly used space vector concept based on the sinusoidal pulse width modulation technique. The time durations of two adjacent voltage space vectors and the corresponding zero voltage space vectors are determined in this method depending on maximum and average switching frequency, allowable for the switching devices in the three-phase inverter. The sampling rate of the impressed reference voltage vector (in other words the switching frequency of the carrier wave) is varied to keep the torque ripple within the specified limit, determined by maximum allowable switching frequency. This paper also deals with the optimum switching pattern to reduce the average switching frequency of the switching devices. A simulation program is developed in order to verify the validity of the theory.

The aim of this paper is to obtain the AC voltage from DC source with the help of Space vector based Inverter. In a space-vector PWM (Pulse Width Modulation) inverter, which is widely used, the voltage utilization factor can be increased to 0.906, normalized to that of the six step operation. Three phase voltage-source pulse width modulation inverters have been widely used for dc/ac power conversion since they can produce a variable voltage and variable frequency power. However, they require a dead time to avoid the arm-short and snubber circuits to suppress the switching spike. Apart from these ancillary aspects, the PWM inverters have an essential problem that they cannot produce voltages as large as the six-step inverters can. That is, the dc bus voltage cannot be utilized to the maximum. To increase the voltage utilization of the sinusoidal PWM inverter, a method of the addition of the third harmonics to the reference voltage was proposed by which the fundamental component can be increased by 15.5%. In a space-vector PWM inverter, which is widely used, the voltage utilization factor can be increased to 0.906, normalized to that of the sixstep operation. On the other hand, different discontinuous PWM strategies were analyzed, where the modulation waveform of a phase has at least one segment of 60 which is clamped to the positive and/or negative dc bus for, at most, a total of 120 in a fundamental period during which no switching in either inverter arm occurs. Recently, it is shown that discontinuous PWM schemes and the space-vector PWM can be obtained by properly adding a zero-sequence voltage to the original modulation waveform.

This paper investigates the effect of (voltage source) inverter's non-linearity on the space vector pulse width modulation (PWM) method and the discontinuous PWM methods, DPWM0, DPWM1, and DPWM2. The inverter's non-linearity of dead-time and minimum pulse-width are considered. These non-linearity's impose distortion regions where their effects cannot be properly compensated. The distortion regions are identified for the various PWM methods in space vector diagram format. A method to switch between DPWM methods to avoid the distortion regions while minimizing switching losses is proposed for the middle modulation indexes. At high modulation indexes, a method to modify the DPWM1 switching function is proposed which preserves the fundamental component while taking into consideration the inverter's non-linearity. The proposed methods are experimentally verified and shown to reduce the harmonics in the motor phase currents which would normally be induced due to the inverter non-linear effects. As a result, the proposed method allows for smoother torque production

The pulse width modulation (PWM) strategy employed in the voltage source inverter (VSI) not only control the magnitude of the output voltage but also the quality. Performance evaluations of such strategies are done in terms of fundamental voltage, total harmonic distortion (THD), switching losses etc. (primary indices) and also in terms of acoustic noise, electromagnetic interference (EMI), harmonic spread factor, distribution of harmonic power etc. (secondary indices). Multilevel inverter (MLI) has become unanimous choice in medium and high power applications due to their superior performance compared to three level inverters. The conventional Sub-Harmonic PWM (SHPWM) scheme and its variations offer the output voltage spectrum with high intensity harmonic components around the switching frequency; it will end with cluster harmonic with high acoustic noise. The first objective of this paper is to investigate harmonic spreading effects of existing multilevel inverter (MLI) strategies. Secondly the developing innovative PWM strategies for MLIs based on modified reference and carrier functions, which were proved for superior the primary indices at three-level VSI. Thorough simulation study of Pulse width modulation strategies such as SHPWM, inverted sine carrier PWM, MWM PWM, third harmonic injection PWM, triplen harmonic injection PWM, analog space vector PWM, trapezoidal PWM and discontinuous PWM for a cascaded multilevel inverter, are presented with results of primary and secondary indices. Hence, the PWM strategies of MLI are evaluated for harmonic spreading effect first time and a guide line for a beginner to select the PWM scheme for MLI fed drive systems is stenciled.

In this paper, Design and development of control circuit algorithm of 3-Φ Voltage Source Inverter (VSI) using Unipolar Sinusoidal Pulse Width Modulation (SPWM) techniques is proposed using STM32F407VGTx discovery board interfaced with MATLAB Simulink Environment. For implementing 3-Φ VSI, this method is most useful as it will eliminate complexity of control circuit algorithm occurred due to analog circuit, reduces cost, size of filter required, and improved overall inverter efficiency. Pulse width modulated voltage source inverter is preferred for high performance AC drives. The proposed control scheme and the result obtained by embedded simulations interfaced with STM32F4 microcontroller are presented and discussed. A simple hardware implementation is proposed and experimental results of SPWM based VSI are also shown. The Simulation results of the proposed scheme have excellent performance and compared with hardware results.

This paper presents a new approach for diagnosis of short circuit Insulated Gate Bipolar Transistor (IGBT) faults in a three-phase voltage-fed motor drive. The three-phase Pulsewidth Modulated (PWM) voltage signals are monitored and digitised into two discrete levels. The combination of discrete voltage levels of the three phases composes eight voltage states. For a healthy Sinusoidal PWM (SPWM) motor drive, all eight states are monitored within one carrier period. However, when a fault occurs certain states cannot be obtained. A fault signature set is defined for each switch fault. By comparing the monitored states with the fault signature sets, the faulty switch is detected and isolated. A PWM voltage source inverter that feeds a threephase Permanent Magnet Synchronous motor with IGBT switch faults is simulated and the fault diagnosis algorithm is applied. The results show that the faults can be diagnosed within tens of microseconds. The robustness of the proposed fault diagnosis and isolation (FDI) approach to the load changes is tested by connecting the motor to a variable mechanical torque.