Pulse Width Modulation Excitation Research Articles

A Stable and Computationally Efficient Spatial Harmonic Model for Predicting the DC Winding Induced Voltage in WFSF Machine

In order to predict the DC winding induced voltage under pulse width modulation excitation in the wound field switched flux (WFSF) machine with consideration of the impact of magnetic coupling among <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i> -, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q</i> -axis and the DC winding, lamination magnetic saturation and current harmonics in both AC and DC windings, the field-circuit coupling method based on the high-fidelity spatial harmonic (SH) model is applied in this paper, including the inductance-based SH model and flux-linkage-based SH model. However, it is found that the inductance-based SH model of the WFSF machine suffers from numerical instability in dynamic operation due to the high condition number of the inductance matrix caused by the magnetic coupling among <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i> -, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q</i> -axis and the DC winding, resulting in prediction errors of the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i> -, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q</i> -axis flux-linkages, and that of the DC winding. To solve this problem, a flux-linkage-based SH model is proposed for the WFSF machine in this paper, and it shows that the proposed flux-linkage-based SH model is numerically stable during the dynamic operation. In addition, the calculation speed of the flux-linkage-based SH model is 147 times faster than the inductance-based one, due to the exemption of the calculation of the partial derivation equations. Finally, the analyzed 24-stator-slot/10-rotor-pole WFSF machine is built and tested to validate the flux-linkage-based SH model, and the experimental results agree well with those of the SH model.

A Method of Ultra-Low Power Consumption Implementation for MEMS Gas Sensors

In recent years, there has been a growing need for the development of low-power gas sensors. This paper proposes pulse heating and a corresponding measurement strategy using a Pulse Width Modulation (PWM) signal to realize the ultra-low power consumption for metal oxide semiconductor (MOS) gas sensors. A Micro-Hot-Plate (MHP) substrate was chosen to investigate the temperature and power characteristics of the MHP under different applied heating methods. The temperature of this given substrate could respond to the applied voltage within 0.1 s, proving the prac ticability of a pulse heating strategy. In addition, Pd-doped SnO2 was synthesized as the sensing material in the implementation of an ultra-low power gas sensor. The sensing performance and power consumption under different conditions were compared in the detection of reducing gases such as ethanol (C2H5OH) and formaldehyde (HCHO). Additionally, the results revealed that the sensor could work under PWM excitation while reducing the operating power to less than 1mW. The features shown in the measurements provide the feasibility for MOS gas sensors’ application in wearable and portable devices.

An Analytical Method for Fast Calculation of Inductor Operating Space for High-Frequency Core Loss Estimation in Two-Level and Three-Level PWM Converters

Along the advances of wide-bandgap power devices, the pulsewidth modulation (PWM) converters are developing toward higher switching frequencies in recent years. Accurate estimation of the high-frequency power losses of magnetic components, the core loss in particular, has been a challenge for PWM converters. While the conventional approaches based on Steinmetz equation lose the accuracy in PWM excitations, the “loss map” approach has been proposed recently as a practical method to accurately estimate the inductor core loss. To calculate the core loss, the inputs of the loss map need to be retrieved from the steady-state inductor voltage/current waveforms. As a supplement to the loss map approach, this work proposes an analytical method to rapidly generate the inputs (inductor operating space) for the loss map to replace the efforts in building simulation models and experimental rigs. The proposed approach relies on the operation and modulation principles of PWM converters and enables computerized calculation of the operating space and the inductor core loss. The proposed approach is developed for both two-level and three-level converters and validated by experiments. The results reveal that a three-level converter running the same inductor generates less than half the core loss compared to a two-level converter, when the maximum current ripple is kept equivalent. The proposed approach is based on the operation principles of the converter topology and, therefore, can be applied generally regardless of the core material or the design of the inductor, as long as the loss map of the inductor is preproduced.

A Practical Inductor Loss Testing Scheme and Device With High Frequency Pulsewidth Modulation Excitations

Voltages across magnetic components of power converters are generally pulsewidth modulation (PWM) waveforms, whereas the parameters of present magnetic core loss models are often tested under sinusoidal excitation by most magnetic material manufacturers. This leads to a significant difference with a PWM excitation and then impacts the testing accuracy of inductor losses. A testing device, based on dc law, has been designed to generate different kinds of PWM waveforms, and a corresponding testing scheme is proposed to accurately measure total inductor losses of different inductances with high frequency PWM excitations. Finally, experiments have been conducted to verify the effectiveness and correctness of the proposed scheme. The results show that the proposed testing scheme can accurately test the total inductor loss. Moreover, the proposed loss model of the testing device is in exact agreement with the actual device's loss with the fitting error within 1%, ensuring the accuracy of the proposed testing scheme.

Assessment of motor core loss, copper loss and magnetic flux density with PAM inverter under dissimilar excitation angles

This study is the first research to present a detailed assessment of core loss, copper loss and magnetic flux density of the interior permanent magnet synchronous motor (IPMSM) with pulse-amplitude modulation (PAM) inverter under different excitation angles in both no-load and load conditions. The PAM method automatically controls the amplitude of changeable DC-link voltage, and the excitation angle for switches in the inverter is varied from 120° to 180° according to a 12-step switching pattern designed particularly for the PAM-based inverter of IPMSM. For reference purpose, the pulse-width modulation excitation with a very high voltage modulation index is performed. Various conditions with changes in speed and torque are examined. Experimental results show that harmonic components produced by the PAM inverter in the IPMSM current, voltage and magnetic flux density have large effects on the motor core and copper losses; physics-based explanations and insights are also presented. The PAM under 135° excitation angle has an excellent performance in reducing IPMSM core and copper losses since it can significantly decrease the harmonic components in motor current, voltage and magnetic flux density. Furthermore, simulations using the finite element method are conducted to validate the experimental results of IPMSM core loss with the PAM excitations.

Position Sensorless Permanent Magnet Synchronous Machine Drives—A Review

Owing to the competitive advantages of cost reduction, system downsizing, and reliability enhancement, position sensorless control methods for permanent magnet synchronous machine drives have drawn increasing attention from academia to industrial applications. In this article, a survey of the major sensorless control techniques for a wide speed range from low to high speeds is presented. The different high frequency signal injection schemes, fundamental pulsewidth modulation excitation methods, and model-based sensorless control are displayed and compared, which is able to facilitate the sensorless control implementation.

A Hybrid Sensorless Controller of an Interior Permanent Magnet Synchronous Machine Using Current Derivative Measurements and a Sliding Mode Observer

The ability of current-derivative based speed and position estimation of IPMSMs over a full speed range has recently been demonstrated. However, at high-speeds, the modulation index becomes limited because the extension of the zero-voltage vectors and current waveforms become distorted. This article proposes a hybrid position and speed estimation technique which uses current derivatives at the first active-voltage vector during each pulsewidth modulation (PWM) switching period for enhancing the performance of a sliding mode observer at low and very low speeds. This article presents the theoretical analysis and experimental evaluation of the proposed sensorless method for an IPMSM over a full speed range from zero to rated speed. The experimental results have shown a significant improvement in speed and position estimation accuracy at low speeds and a considerable reduction of the current distortion over the full speed range, compared to the existing fundamental PWM excitation sensorless control methods.

Structure-borne Noise at PWM Excitation using an Extended Field Reconstruction Method and Modal Decomposition

Pulse-Width Modulation (PWM) represents a carrier-frequency-dependent structural excitation. The PWM’s excitation harmonics are also reflected in the air gap’s electromagnetic forces, the vibration response and the resulting structure-borne noise. The last of these can be numerically predicted with a multiphysics finite-element-analysis (FEA) containing electronic, electromagnetic, mechanical and acoustic field problems. The multiphysics FEA are precise, but computationally inefficient and consequently inadequate for parametric studies. This paper introduces a method for a fast structure-borne noise prediction at PWM excitation. The presented approach contains the Extended Field Reconstruction Method (EFRM) to handle the magnetic saturation and slotting effects in magnetics, and the modal decomposition to couple the electromagnetic and mechanical domains. Finally, the structure-borne sound power level is calculated via the vibration-velocity response. Indeed, this approach demands a pre-calculation of the basis functions and modal parameters from the FEA, but afterwards the effect of the different PWM excitation cases can be evaluated in a few seconds. The proposed method can calculate the structure-borne noise at PWM excitation accurately and is more than 104 times faster than the conventional multiphysics FEA approach.

Online Stator Inductance Estimation for Permanent Magnet Motors Using PWM Excitation

The permanent-magnet motors are widely used especially in traction and power steering motor drive applications in automotive. Accurate knowledge of machine parameters, such as the inductance, is essential for efficient and optimal control of the machine. There are numerous methods proposed in the literature for online as well as off-line learning of machine parameters. They differ in accuracy and measurement techniques. This paper proposes an online measurement of inductance using the relationship with the current derivative. An adaptive observer is used to calculate the inductance parameters from the current measured. The proposed method uses no external injection but relies on the pulsewidth modulation excitation used for normal motor drive control. The simulation and experimental results show the feasibility and performance of the proposed technique.

A Modified Sensorless Control Scheme for Interior Permanent Magnet Synchronous Motor Over Zero to Rated Speed Range Using Current Derivative Measurements

This paper proposes a modified sensorless control technique for an interior permanent magnet synchronous motor over its full-speed range based on current derivative measurements and fundamental pulsewidth modulation excitation (FPE). The proposed method employs measurement of the current derivative at only one active-voltage vector at low speeds, and at one active-voltage vector and one zero-voltage vector at medium and high speeds during each pulsewidth modulation (PWM) cycle, in contrast to two active- and two zero-voltage vectors in the conventional FPE method. The theoretical analysis is developed based on the three-phase model of the machine. The rotor position and speed are estimated at PWM frequency. In addition, the selection voltage vectors for current derivative measurement as well as the pulse stretching scheme for extending and compensating the selected voltage vectors is proposed in order to improve the accuracy of the current derivative measurement and to minimize the current distortion. The experimental results show that the proposed method results in a considerable improvement of the estimation accuracy at low speeds, a significant reduction of current distortion compared to the conventional FPE method and a full-speed range operation from no load to full load.

A Combining FPE and Additional Test Vectors Hybrid Strategy for IPMSM Sensorless Control

This paper proposes a hybrid strategy by combining fundamental pulsewidth modulation excitation (FPE) and additional test vectors, which is used in interior permanent-magnet synchronous motor (IPMSM) sensorless control. In contrast to the typical indirect flux detection by on-line reactance measurement-based methodology where the rotor position is calculated and updated in every three successive pulsewidth modulation (PWM) cycles, the proposed hybrid strategy can achieve the one-cycle acquisition of the rotor position by utilizing both response currents of FPE and additional test vectors, which makes the proposed strategy more robust and suitable in higher speed or load sudden change conditions. Meanwhile, a new PWM scheme for four-space-vector PWM (FSVPWM) is presented, which sharply simplifies the implementation process. Furthermore, for the case that the amplitude of the object fundamental voltage is so small that it cannot satisfy minimum time demand for the slopes of response currents sampling, a compensation technique is presented. In addition, the multiple-point current sampling (MPCS) technology and linear least square fitting method are used to decrease the current sampling disturbance, which improves obviously the accuracy of position estimation. Finally, the experimental results confirm that the proposed strategy can obtain the rotor position accurately and simply.

Ladder Circuit Modeling of Dynamic Hysteretic Property Representing Excess Eddy-Current Loss

Bertotti’s model for excess eddy-current (EC) loss is combined with the dynamic hysteresis model represented by a Cauer circuit and the play model. The excess EC field of the Cauer circuit is represented by nonlinear resistors. A formulation of excess EC field based on nonlinear current conduction is developed for the finite-element EC analysis, which is applied to the physical Cauer circuit. The proposed models improve the ac iron-loss evaluation under sinusoidal excitation of frequencies up to 20 kHz and achieve an accurate $B$ – $H$ loop representation under pulse-width modulation excitations.

Analysis on iron loss of switched reluctance motor under PWM mode

PurposeThis paper aims to establish a modified variable coefficient calculation model to analyse the control parameter effect on the iron loss of switched reluctance motor under pulse width modulation (PWM) mode.Design/methodology/approachThe finite element model is solved to get the flux density by python language. Due to non-sinusoidal flux density feature and the effect of PWM excitation, the Fourier transform is applied in consideration of harmonic components. To improve the accuracy of iron loss computation, the effect of minor loops is considered by using the rain-flow counting method.FindingsWhen the speed fluctuates around the set speed and the fluctuations are relatively small, it is useful to reduce the iron loss with smaller duty ratio and turn-on angle or greater duty ratio and smaller turn-off angle. The iron loss is less affected by chopping frequency, while the iron loss increases obviously with higher conduction angles. The iron loss under non-energy-returnable-voltage-chop mode is greater than energy-returnable-voltage-chop mode.Originality/valueThe modified variable coefficient MIEM5 iron loss model is proposed to improve the accuracy of iron loss calculation. Then the control parameters such as duty ratio, chopping frequency, turn on angle and turn off angle are analysed under PWM mode.

Macroscopic Description of the Magnetostrictive Behavior of Electrical Steel in the Presence of High-Order Harmonics in the Magnetization

Magnetostrictive behavior of the electrical steel cores of transformers and electrical machines has been studied under well-known excitation waveforms, e.g., purely sinusoidal. However, the magnetization may contain higher harmonics due to the grid harmonics for the application in transformers or due to pulse width modulation excitation in the case of induction machines. We have reported the presence of a single low-order harmonic in magnetization, but in reality, a superposition of several low- and high-order harmonics is present, which needs to be studied. Thus, in this paper, the magnetostrictive behavior of electrical steel is measured under a sinusoidal magnetization with high-order harmonics. A macroscopic description of the magnetostrictive behavior is presented afterward.

Cauer Circuit Representation of the Homogenized Eddy-Current Field Based on the Legendre Expansion for a Magnetic Sheet

Using the Legendre expansion of the magnetic field distribution, we derive the standard Cauer circuit representation of the frequency-dependent properties of magnetic sheets and discuss its physical meaning. The representation of non-linear inductors is derived so as to apply the Cauer circuit in the dynamic hysteresis modeling of silicon steel. This circuit accurately reconstructs the hysteretic property under pulsewidth modulation excitation using only one or two hysteretic elements.

Equivalent circuit modeling of dynamic hysteretic property of silicon steel under pulse width modulation excitation

This paper describes the development of an efficient and accurate dynamic hysteresis model that combines the Cauer circuit representations with the play model. The physical meaning of the standard Cauer circuit is discussed and is used to derive a mathematical representation of hysteretic inductors. The iron-loss and hysteresis loops of silicon steel that were obtained using the proposed model agree with experimental data measured under sinusoidal and pulse width modulation excitations.

Motor Temperature Monitoring Based on Impedance Estimation at PWM Frequencies

This paper proposes a noninvasive temperature measurement technique of indirect type, applicable in the permanent magnet synchronous motor (PMSM) drives. The motor temperature is required for protection and monitoring purposes, as well as for updating temperature-dependent control parameters. Direct measurement with dedicated sensors requires peripherals and cabling; hence, it is quite involved and often avoided. Temperature estimation based on test signal injection contributes to torque ripple and often relies on other motor parameters. A solution is proposed here, which makes the use of intrinsic pulse-width modulation excitation and does not use electrical or thermal parameters of the considered PMSM. The temperature of the stator winding is estimated from the motor input impedance ZIN(ω) calculated over the range of frequencies starting at and going well beyond fPWM. The paper includes analytical considerations, implementation details and experimental verification obtained with a 4.5-kW PMSM used in battery-supplied propulsion systems.

Behavior of Minor Loop and Iron Loss Under Constant Voltage Type PWM Inverter Excitation

The pulse width modulation (PWM) inverter is widely used for the control of motors. We showed that the iron loss under PWM inverter excitation is affected by the impedance of the excitation circuit. The dc voltage of PWM inverter, which is widely used, is constant and the control of motor is carried out by changing the modulation index. Therefore, the evaluation of iron loss under PWM excitation with constant dc voltage is necessary in order to investigate the behavior of iron loss in an actual motor. In this paper, we measured iron losses of non-oriented electrical steel sheets under the shingle-phase full-bridge PWM inverter excitation and examined the influence of modulation index m, carrier frequency fc and dc voltage Vdc on the iron losses. It is shown that the iron loss under PWM inverter excitation can be reduced when dc voltage Vdc is reduced and modulation index m is increased.

Dynamic Finite Element Hysteresis Model for Iron Loss Calculation in Non-Oriented Grain Iron Laminations Under PWM Excitation

This paper introduces a dynamic finite element model for calculating iron loss in ferromagnetic non-oriented grain laminations under pulse-width modulation (PWM) excitation. The proposed methodology accounts for static hysteresis, classical eddy currents and anomalous losses and has been validated by measurements in Epstein device in different cases of PWM voltage waveforms. The model is based on a particular 2-D finite-element technique by using standard static iron lamination characteristics and offers sufficient accuracy in all studied cases.

Comparison of the Effects of Continuous and Discontinuous PWM Schemes on Power Losses of Voltage-Sourced Inverters for Induction Motor Drives

In this paper, losses in a 4-kVA three-phase voltage-sourced inverter designed to drive an induction machine, are investigated. A comparison of inverter losses with sinusoidal pulsewidth modulation (PWM), space vector PWM and discontinuous PWM (DPWM) is presented, concluding that DPWM is the method of choice. These PWM schemes are implemented using a field-programmable gate array and modeled in Pspice. PWM excitation models are combined with an inverter model that incorporates the Hefner model for the insulated gate bipolar transistors. After verification of the complete inverter model with calorimetric measurements, the model is used to predict inverter losses under various conditions of modulation index, switching frequency, and gate resistance for each of the PWM scheme. A breakdown of losses into conduction and switching losses is presented. Moreover, the effects of different DPWM variants on inverter losses are also being considered. Overall, the use of DPWM is found to give minimum losses as a consequence of the reduced number of switching transitions.