Single-Phase Multilevel PWM Inverter Topologies Using Coupled Inductors

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.

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.

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.

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.

Smart rheological materials represented by giant electrorheological fluid (GERF) have attracted considerable attention in vibration isolation, microfluidics, and robotics. The traditional control method is primarily to adjust the amplitude of the constant voltage. This paper introduces a GERF damper that works in squeeze mode and uses varying pulse width modulation (PWM) voltage for damping adjustment. The influence of PWM voltage parameters on the damping characteristics of the damper is analyzed through experiments. The similarities and differences between the constant voltage and PWM voltage are discussed. PWM voltage can obtain larger equivalent damping with small duty cycles. A parametric model is established based on the squeeze flow principle to describe the damping characteristics of the damper. The root mean square error between the experimental and model results is less than 0.015, which verifies the accuracy of the model. The results of the vibration platform test show that the PWM voltage control can adjust the transmissibility of the damper in the frequency domain. The amplitude of the vibration is reduced by 56% in the time domain. This study provides a new damping adjustment method for GERF dampers.

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.

This paper describes the basic concept of an integrated virtual learning system as an instructional tool for the development of digital signal processor (DSP)-based control schemes for motor drive applications. The system is comprised of a graphical user interface (GUI) front-end and a hardware-in-the-loop custom DSP for rapid prototyping and efficient testing of digital control algorithms. The circuit design and control algorithm development of a pulse width modulation (PWM) voltage source inverter (VSI) for 3-phase brushless DC (BLDC) motor control applications is used to describe the functions of the system. It is shown that the virtual learning system provides a cost-effective learning tool for students or engineers in training and can serve as a supplement to a conventional laboratory based system.

This work proposes a methodology to estimate core losses under pulsewidth modulation (PWM) or dc bias ripple voltage excitations. A special hysteresisgraph was built to measure toroidal samples under pulsed voltages. An experimental methodology, based on the principles of ferromagnetism, was implemented to investigate minor loop losses in toroidal samples of oriented and nonoriented FeSi. Triangular induction waveforms with constant dB/dt were generated. The results demonstrated that minor loops produced by PWM voltage, do not affect the major hysteresis loop losses nor the losses of other minor loops measured at different points of the major loop. In these experiments, minor loop losses under PWM voltage were very similar to minor loop losses under dc bias ripple voltage. Aspects of the behavior of minor loop losses as a function of amplitude and magnetic flux density are reported in this work.

Up to now, the performance of current control for field-oriented control of the induction machine using pulsewidth-modulated (PWM) voltage source inverter have the problem that it can not provide high-accuracy and quick-tracking response simultaneously. For improvement, two variable structure approaches are proposed in this paper. One is the so called Discontinuous Damping System method implemented by software alone, which is suitable when switching frequency of inverter is higher. The other is a combination of software PI controller and hardware hysteresis comparator, which is necessary in the case of lower switching frequency. Experimental results show that both approaches have the dynamic response as fast as that of a hysteresis controller as well as an accurate static response with the least harmonic currents. An optimum PWM pattern of the inverter based on the space vector concept was also implemented so that not only the harmonic currents are limited but also, with the proposed methods, it becomes easy to compensate the dead-time of the inverter and to sample motor current eliminating the distortions.

End turn grading with resistive–capacitive coupling experiences severe electrothermal stress when subjected to pulse width modulation (PWM) voltage. In this paper, several experiments and simulations were carried conducted for four types of end turn grading. First of all, the temperature rise in the end turn grading increased with a decrease in rise time. When the rise time was less than 500 ns, the temperature rise at the terminal was higher owing to the increased capacitive current coupled from the main wall insulation. Further, the current in the linear region exhibited minimal variation at different fundamental frequencies resulting in synchronized the temperature rise at the terminal and overlap. Furthermore, the jump voltage was the key factor influencing temperature rise in end turn grading, confirmed by comparing different voltage magnitudes. Finally, the transient behaviour of the maximum field in the stress grading material was determined at rise time. The experimental and simulation results indicate that balancing and interdependently addressing the electrical and thermal stress protection in end turn grading is crucial. The study aims to provide an experimental and theoretical foundation for an insulation system of inverter‐fed rotating machinery operating under PWM voltage.

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

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 deals with a wind energy conversion system (WECS), based on a doubly fed induction generator (DFIG) and an electromechanical active power filter (APF). The objective is to respond simultaneously to electric energy requirement and power quality concerns. The proposed WECS is able not only to track the maximum power point of the wind energy but also to dampen harmonic currents from the grid line. To achieve these purposes, back-to-back pulse width modulation (PWM) voltage source converters (VSCs) are employed to excite the DFIG rotor. To control the power converters, two regulation loops, following the field oriented control (FOC) method, have been conceived. The first loop, dedicated to the rotor converter, enables a decoupled control of active and reactive powers flows. As well, it permits the cancellation of the most noteworthy harmonics from the utility current. The second loop, devoted to the front-end converter (FEC), makes it possible to regulate the DC-bus voltage shared between the two converters. Furthermore, the paper provides a study of the DFIG sub and super-synchronous operating modes which can be reached by acting on the wind speed. To demonstrate the performance of aforementioned WECS, a Matlab/Simulink model was established and simulated. Results seem to be very promising.

Saliency-based position sensorless drive with the pulse width modulation (PWM) voltage injection has advantages of high estimation bandwidth and low acoustic noise. However, multiple currents should be sampled every PWM cycle for spatial saliency calculation. Considering the standard SVPWM control, the PWM voltage injection distorts the symmetric voltage pattern with additional position estimation errors. This paper proposes a modified PWM through the measurement vector insertion (MVI) for PWM injection based position estimation. By integrating the MVI with discontinuous PWM (DPWM), the proposed PWM injection maintains the symmetric voltage pattern for FOC. This MVIPWM injection is compared to other PWM injection methods on an interior PM machine. All the advantages of MVIPWM on the saliency-based drive are verified by experimental results.

Transient stability enhancement of wind farms connected to a multi-machine power system by using an adaptive ANN-controlled SMES