Frequency Pulse Width Modulation Research Articles

The Impact of VSFPWM on DQ Current Control and a Compensation Method

The variable switching frequency pulsewidth modulation (VSFPWM) is varying the carrier frequency of pulsewidth modulation (PWM) based on the prediction model to reduce the switching losses and lower the electromagnetic interference (EMI). However, it may cause some deterioration in digital dq current control of voltage source converters. This article takes the L -type grid-connected converter as the research object, and first presents the generation mechanism of the varying time delay caused by VSFPWM. In the case of proportional-integral current regulator implemented with VSFPWM, the varying time delay is accompanied by the frame rotation, which causes a varying phase lag in output voltages, degrading the system performance. Subsequently, an analytical method based on complex coefficient transfer functions is developed to provide an accurate explanation of the relation between the VSFPWM and the corresponding impacts. A compensation method is then proposed to eliminate the varying phase lag of output voltages when the VSFPWM is employed, improving the steady state and dynamic performance of dq current control. Finally, the simulation and experimental results are presented to verify the analysis and the effectiveness of the proposed compensation method.

Non‐isolated LLC resonant converter with suppressed circulating current and automatic resonant frequency matching capability

This study proposed a novel non-isolated half-bridge Inductor-Inductor-Capacitor (HB LLC) resonant converter with automatic resonant frequency adjustment ability and a circulating current suppression auxiliary circuit. The proposed converter employs a hybrid modulation technique based on frequency modulation (FM) and pulse width modulation (PWM) to regulate the output voltage. At the nominal operating point, all the excellent attributes of a conventional LLC converter over the entire load range are maintained and output voltage control is achieved with FM. However, when the input voltage decreased to a level that LLC output voltage cannot be maintained with FM, the primary switches will operate at the minimum switching frequency and the auxiliary switch will be turned ON with PWM. The auxiliary switch is turned ON with zero-voltage switching and automatically matching the circuit resonant frequency with the switching frequency for optimal operation. The effective resonant inductor is energised directly from the dc bus storing more energy which is later released to the load to achieving high gain while maintaining the desired output voltage with a narrow frequency span. In addition, the converter exhibits low circulating current under an enhanced gain condition. Experimental results are presented on a 60 W prototype to validate the theoretical prediction. The proposed converter has a peak efficiency of 97%.

Baseband Model for Uniformly Sampled RF-PWM

A baseband model for a polar RF modulator based on uniform sampling (US) pulse width modulation (PWM) is presented. RF-PWM allows to encode a complex baseband signal (amplitude and phase) into the pulse width and pulse position of a binary signal towards an efficient and fully digital RF transmitter implementation. We extend the well-known derivation of the naturally sampled (NS) RF-PWM to obtain a detailed model of the US RF-PWM which includes the intrinsic inband and side-bands distortion. In RF-PWM the carrier frequency is equal to the PWM frequency (first PWM harmonic). We develop the model such that the first or any other higher harmonic of the PWM can be used as the carrier signal. The distortion signal is analyzed in detail and a discrete-time implementation of the model which relates to previous approaches is presented. This model is key to the analysis, characterization and simulation of a fully digital transmitter.

Zero-Voltage-Switching Current Source Inverter Fed PMSM Drives With Reduced EMI

The silicon carbide (SiC) devices have attracted more and more attention due to the capability of withstanding higher blocking voltage, higher switching frequency, and higher temperature. However, challenges for SiC devices applied in voltage-source-inverter fed motor drives such as electromagnetic interference (EMI) issues and limited over-current capability still limit the further application of SiC devices. In this article, a novel SiC devices based zero-voltage-switching (ZVS) current-source-inverter (CSI) is proposed for permanent-magnet synchronous motor (PMSM) drive. The key is to propose an auxiliary resonant circuit, which achieves ZVS conditions for all switches in power circuits and reduces the dv/dt of high speed SiC devices. The resonant capacitor in the auxiliary circuit can clamp overvoltage caused by possible open-circuit faults. To further reduce the EMI, the random switching frequency pulsewidth modulation is designed for the proposed CSI motor drive. The system configuration, working principle, circuit design, and control schemes are described in detail. Both simulations and experiments are presented to verify the effectiveness of the proposed ZVS-CSI fed PMSM drive system.

Saliency-Based Permanent Magnet Machine Position Sensorless Drive Using Proposed PWM Injection and Shunt-Based Current Sensing for Position Estimation

For saliency-based position sensorless drives, the switching frequency pulsewidth modulation (PWM) voltage injection can achieve noise-free position estimation which is suited for high-performance motion systems. However, considering the switching frequency injection, multiple phase currents should be sampled per PWM cycle instead of single average current. It leads to the implementation issue on the space-vector PWM (SVPWM) inverter using shunt resistor current sensing for machine control. In this article, a modified PWM injection instead of SVPWM injection is proposed for the saliency-based drive using shunt current sensing. It is concluded that at least two transient currents can be sampled per PWM cycle based on the proposed PWM control. More importantly, the field-oriented control is maintained when the saliency-based drive is applied. A 2 kW permanent magnet (PM) machine is used for the experimental verification. This article includes the position estimation comparison using either the proposed PWM injection with shunt resistors or standard SVPWM with Hall-effect sensors.

The Essence of the Little Box Challenge-Part A: Key Design Challenges & Solutions

In order to expedite the development of power electronic systems towards higher power density and efficiency at a lower cost of implementation, Google and IEEE initiated the Google Little Box Challenge (GLBC) aiming for the worldwide smallest 2 kVA / 450 V DC / 230 V AC single-phase PV inverter with η > 95 % CEC weighted efficiency and an air-cooled case temperature of less than 60 °C by using latest power semiconductor technology and innovative topological concepts. This paper, i.e., Part A of a discussion of The Essence of the Little Box Challenge, documents all important RD Part B is intended to convey the main findings and lessons learned from the participation in the GLBC. First, the key technical challenges of the GLBC are discussed and the technologies and concepts selected by the authors among different options are described in detail. Relevant design considerations, such as constant frequency pulse width modulation (PWM) or triangular current mode (TCM) operation of the bridge-legs, selection of power semiconductor technology, interleaving of bridge-legs, sizing of the power buffer capacitor, limitation of ground/leakage currents, etc., to achieve an ultra-compact implementation are discussed. Based on this overview, two promising inverter concepts to tackle the GLBC, (i) an H-bridge based inverter with DC-link referenced output filter and (ii) a DC/|AC| buck-stage with series-connected low-frequency (LF) |AC|/AC unfolder inverter, are then analyzed in detail. Based on the results of a multi-objective ηρ-Pareto optimization, a comparative evaluation of the performance in terms of efficiency (η) and power density (ρ) of the two considered inverter concepts is provided. It is shown that with the DC/|AC| buck-stage and |AC|/AC H-bridge unfolder inverter operated with 140 kHz PWM a power density of 14.7 kW/dm 3 (240 W/in 3 ) with a maximum efficiency of 98.1% at 2 kW output power can be achieved. These claims are then verified in Part B by means of experimental results obtained from prototype realizations and compared to the achievements of other GLBC finalists. The conclusions are of general importance and are providing key guidelines for the future development of ultra-compact power electronic converters.

On pulse-width pulse-frequency modulator control strategy: An adaptation-based describing function representation

This research describes an adaptation-based control strategy to deal with the pulse-width pulse-frequency modulator. The subject behind the research is to control the above-referenced modulators the hard limiter block via closed-loop describing function representation. In a word, this modulator has a set of parameters, which are all in need of adjusting, accurately, in order to guarantee its high performance, in the entire areas of overall systems under control. The investigated results indicate that parameter’s adjustment of the aforementioned pulse-width pulse-frequency modulator can be recognized as the state-of-the-art outcomes via adaptation rules.

Методи боротьби з кондуктивною завадоемісією у зворотноходових перетворювачах

Pulsed power supplies of various topologies (return running, forward running, half-bridge and full-bridge converters) generate high-frequency common-mode noise through their high-frequency mode of pulse-width modulation. Electrical and electronic equipment is known to comply with electromagnetic compatibility standards such as CISPR, IEC, EN, FCC. If necessary, to reduce the converter mass, the pulse-width modulation frequency will increase. As a result, the electromagnetic noise of the power source also becomes larger. Therefore, electromagnetic compatibility problems become one of the most difficult to design power supplies.The article presents methods for reducing conducted noise emission, namely the suppression of common-mode noise in switching power supplies. In particular, schematic methods and methods with constructive changes, physical harmonics compensation methods (interleaving), and methods based on special control methods are presented. The structural and compensation approach allows achieving significant results in reducing the level of common-mode noise. The structural approach includes grounding and shielding. The compensation approach includes three methods: the first is the method of mutual compensation of noise sources; the second is the method of quasicompensation of noise sources; the third is the method of active compensation. The conducted simulation confirmed the decrease in the emission of higher harmonics of the input current in the power network.

THD Reduction in Multi Level Inverters based on Multicarrier Pulse Width Modulation Technique

Due to the advent of technology, electronic equipments are much more sensitive to harmonic and its analysis play an important role whereby reducing the distortion due to harmonics needs attention. To meet the requirements of the industries, harmonic free-high rating power sources are in high demand. Total Harmonic Distortion (THD) is an indicator of AC voltage source quality. In case of inverters, one such way to reduce THD would be the use of Pulse Width Modulation (PWM). The existing methods mainly use the low frequency pulse width modulation techniques for the switching. Control methods employing high frequency switching techniques held in controlling THD with proper application of filters. This paper analyses THD in multilevel inverters using multicarrier PWM technique with five pulse width modulation technique through MATLAB simulations. Finally, a comparison is done to find the less harmonic generated PWM method using fewerfilters.

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.

The Influence of LC Filter on the Current Control of PWM-Fed Induction Motor Considering the Effect of Back-EMF

The high switch speed pulse width modulation (PWM) significantly improves the performance of induction motor. However, this mode of control generates PWM ripples and a wide spectrum of over-voltages at the motor terminal which stress the motor insulation and cause bearing current and electromagnetic interference (EMI). To solve this problem, LC passive filter is widely used because of its effectiveness on limit overvoltage and PWM ripples. This paper discuss the influence of LC filter on PWM-fed induction motor in a different view. The impedance of the motor is decided by its inductance and resistance in traditional research. In this paper, a more accuracy model is built up involving the effect of back electromotive force (EMF). Based on which, the situation of current control is investigated when the LC filter is employed. It is revealed that the inductance of the filter is the key factor of control bandwidth and a method to enhance current control bandwidth while avoid the loss of suppression ability of differential-mode PWM frequency components is given.

Research on Modified Hybrid Frequency Modulation Technology of Type-III Asymmetric CHB Multilevel Inverters

Asymmetric Cascaded H-bridge (ACHB) level inverters can output more voltage waveforms with fewer cascaded units while ensuring the quality of output voltage waveforms, so they have attracted more and more attention. Taking the topology of Type-III asymmetric CHB multilevel inverters as the research object, a Modified Hybrid Frequency Pulse Width Modulation (MHF-PWM) strategy is proposed in this paper. This modulation strategy overcomes the local overshoot of low-voltage unit in the presence of traditional Hybrid Frequency Pulse Width Modulation (HF-PWM), thus completely eliminating the low frequency harmonics in the output voltage waveform of Type-III ACHB nine-level inverters, and the Total Harmonic Distortion (THD) of output line voltage of the modulation strategy is lower than that of PS-PWM strategy in the whole modulation degree, which effectively improves the quality waveform of the output line voltage. At the same time, the strategy can also improve the problems of current backflow and energy feedback caused by the high-voltage unit pouring current to the low-voltage unit, thereby reducing the imbalance of the output power of the high-voltage and low-voltage units. Finally, the Matlab/Simulink simulation model and experimental platform are established to verify the validity and practicality of the modulation strategy.

Estimation of PWM-Induced Iron Loss in IPM Machines Incorporating the Impact of Flux Ripple Waveshape and Nonlinear Magnetic Characteristics

This article presents an improved estimation model to predict the additional iron loss due to pulsewidth modulation (PWM) switching in interior permanent magnet (IPM) machines. The input current including the predicted PWM-induced current ripple is fed to two-dimensional (2-D) finite-element analysis to calculate the PWM-induced flux ripple distribution in the analyzed machine. A special frequency decomposition method is proposed to separate the predicted flux ripple into 1x and 2x PWM frequency components. Combining these results with the modified dynamic Jiles-Atherton model, the PWM-induced iron loss is calculated incorporating the impact of the actual flux ripple waveshape and the lamination steel's nonlinear magnetic characteristics. Experiments have been conducted to evaluate the prediction accuracy and investigate the impact of several factors on PWM-induced core losses (i.e., both iron and magnet loss) in IPM machines. These results demonstrate that the model offers promising estimation accuracy over a wide range of machine and inverter operating conditions.

A Simple Torque Estimator for In-Service Efficiency Determination of Inverter-Fed Induction Motors

This article deals with air-gap torque estimation in inverter-fed induction motors. Torque estimation is an important stage in the methods used to evaluate energy consumption and efficiency. Those methods are essential to monitoring electric motors and processes in mining and metal industries. As some of the drives have voltage and current sensors already installed in them for condition monitoring, it is very attractive to use measurement data available to perform torque and efficiency estimation. It is highly desirable to implement these functions without process interruption and/or requiring minimum changes in the drive configuration. Most of the torque estimation algorithms require two or three voltage and current measurements to be implemented. Aiming to reduce the number of sensors and obtain a lower cost setup, a strategy to estimate torque that requires data acquisition of the current and voltage of only one phase suited to be used in algorithms of efficiency estimation of in-service induction motors was presented in a previous article by the same authors. There, the performance of the method was investigated when applied to induction motors directly connected to the power grid. In a second published article, the performance of the method was additionally investigated for induction motors supplied by means of pulsewidth-modulated frequency inverters. The effects of unbalance in voltage supply were also described and analyzed there. In this article, in addition to the analysis performed in the last published article, a measurement uncertainty analysis is done. Simulation and experimental results are used to check the validity and performance of the proposed technique.

Design and implementation of a 350-watt BLDC motor driver using an Insulated Gate Bipolar Transistor (IGBT)

IGBT device was not commonly used as a BLDC motor speed controller. This paper described the successful of using IGBTs in a 350Watt BLDC motor speed controller. Triple bridge configuration with PWM (Pulse Width Modulation) wave signal for power tuning was mainly integrated as a main switching method in order to drive the current commutation cycle. Also, an efficient bootstrap IC was designated to perform as the high and low side driver. The data were measured by using a current sensor and a DC voltage sensor to measure the current and the voltage delivered from the power source. Then, IGBT device was activated based on triple bridge commutation cycle and phase based on motor hall effect sensor triggering signal. The performance was also tested by varying the duty cycle input ratio and its PWM frequency. It can conclude that the BLDC motor controller can be made by using an IGBT and added gate drivers for the IGBT. Meanwhile, to adjust the commutation cycle, a high speed processor was used to generate gate activation and PWM signal. Changing the PWM duty cycle starting from 10% to 90% by turning the setting point, observed that BLDC motor rotates successfully without load and maximum power used was 111.20 watts with 2,32 amperes current at 48 volts supply voltage.

A Boost CLLC Converter Controlled by PWM and PFM Hybrid Modulation for Photovoltaic Power Generation

When an input terminal is connected to a solar panel with a low voltage level and large power range fluctuation, a Boost type CLLC converter controlled by fixed frequency pulse width modulation (PWM) reduces the utilization of PV electric energy, and the synchronous drive of the secondary side and primary side ensures that the converter operates with low efficiency when the duty cycle is shifted by 0.5. To maximize the utilization of photovoltaic (PV) energy in a PV power generation system and improve the conversion efficiency, this paper studies a Boost CLLC converter with high gain and soft switching controlled by PWM-pulse frequency modulation (PFM) hybrid modulation for PV power generation. By controlling the duty cycle and switching frequency of the primary MOSFETs, the converter can stabilize the output voltage while tracking the PV maximum power point. Under such a hybrid control, the resonant gain of the converter is greater than 1, the voltage gain is large, one of the MOSFETs at the primary side is in a zero-voltage-switching-open (ZVS-ON) state, two diodes are used to realize zero-current-switching (ZCS) soft switching on the secondary side, and the efficiency of the converter is high. In addition, this paper studies the phenomenon of backflow power in the resonant circuit and the influence of a change in the switching frequency on the magnitude of the backflow power. Finally, a 500W experimental prototype was constructed to verify the accuracy of the theoretical analysis and the feasibility of the control method.

Study of complex dynamics in DC-DC boost converter with dSPACE-based real time controller

Switching converter circuits are nonlinear and time-varying in nature. In this paper, the complex dynamics in voltage mode controlled (VMC) DC-DC boost converter has been investigated through simulation and experimentation. The converter is controlled by naturally sampled constant frequency pulse width modulation (PWM) signals in continuous conduction mode (CCM) and converter exhibits fundamental, quasi-periodic and chaotic oscillations for the variation of circuit parameters. In simulation study, the model of boost converter is computed by non-autonomous differential equations and finally, the computational waveforms have been verified with experimental results. In order to verify simulation study, a laboratory scale prototype of closed-loop boost converter has been fabricated. The closed-loop converter is controlled by dSPACE in real-time platform. The results obtained from simulation and experimental study have been presented and compared. It has been observed that the route to chaos is achieved by the slow-scale instability in this proposed study.

Speed Control of Induction Motor Driving a Pump Supplied by a Photovoltaic Array

The integration of renewable energies in electrical systems is a research area that is becoming more and more important. In this context, this work aims regulation of induction motor speed that drives a pump supplied by a photovoltaic array. The objective of this study is to calculate the reference speed corresponding to the maximum power supplied by the photovoltaic generator at each climate change and control the motor to achieve it. The system is formed by a boost converter and a three-phase inverter connected to a three-phase LC filter. Numerical management, including the maximum power point algorithm of type perturbs and observe to control the boost converter and sinusoidal pulse width modulation of variable frequency to control the inverter is used. The sinusoidal pulse width modulation frequency is given by the PI regulator that compares motor speed with reference speed. The reference speed is calculated through a program based on climate changes and photovoltaic maximum power. The program is implemented as a Matlab function block. The simulation results show that the PV output voltage and current converge to values corresponding to the maximum power. The motor speed follows the reference speed which approves the good functioning of the PI regulator.

Quasi-Z-Source Inverter using Sliding Mode Controller with Impedance Network

Quasi inverter is designed in this paper to enhanced gain operation using sliding mode controller (SMC) with Z-source inverter (ZSI). It has boost voltage conversion at low ratio in duty cycle and output voltage quality is improved by high modulation index. Direct current (DC) is converted to alternating current (AC) with higher frequency pulse width modulation (PWM) signals. To reduce the inrush current in starting period it draws a low voltage at capacitors. This proposed inverter consists of common ground to source as well as bridge rectifier. Moreover, the ripple current is almost negligible in this ZSI. This paper proposes the ZSI with impedance of two switches network and the theoretical analysis done also it is confirmed in MATLAB/Simulink.

Sensorless Low Switching Frequency Explicit Model Predictive Control of Induction Machines Fed by Neutral Point Clamped Inverter

This paper proposes an explicit predictive current control scheme implemented with a low carrier frequency pulsewidth modulation (PWM) on an induction machine fed by a three-level neutral point clamped inverter. The PWM carrier and the main current sampling frequency are both set to 1 kHz, resulting in a 500 Hz average switching frequency per device, which is very suitable for large drive applications. The explicit predictive control is introduced to optimize the available bandwidth provided by such a low sampling frequency, maximizing the dynamic performance. The strategy has been tested in a 2.2-kW induction motor experimental prototype.