PWM Switching Frequency Research Articles

COMPUTER OPTIMIZATION OF SWITCHING FREQUENCY OF TRANSISTOR PULSE-WIDTH CONVERTERS

The aim of the work is to develop algorithm for determining the optimal switching frequency of a transistor pulse-width converter (PWM) to minimize the total electrical losses in a DC drive. Electrical losses in the armature winding and in PWM transistors are divided into two components: static from the direct current component and dynamic. The latter include losses in the armature winding from the harmonic components of the current and losses in transistors from transient switching currents. Since the dynamic losses in transistors increase with increasing frequency, and in the armature winding from current harmonics they decrease, there is an optimal switching frequency value at which the total dynamic losses in the PWM drive will be minimal. This aim is achieved by solving the problem of determining the analytical dependence of dynamic electrical losses in the armature winding on the PWM switching frequency and computer simulation of a transistor DC drive. As a result of the research, an analytical expression was obtained for calculating the relative dynamic electrical losses in the armature winding with polyharmonic power supply. An algorithm is proposed for determining the optimal switching frequency of the PWM: 1) on computer models of the DC motor and PWM, the dependences of dynamic electrical losses on the switching frequency are determined; 2) build a graph of the dependence of the total dynamic electrical losses, on the which determine the point of minimum losses, which corresponds to the optimal value of the switching frequency. The novelty of the work lies in the fact that the theory of electrical losses in the armature windings with polyharmonic power has been further developed.

Analysis and Approximation of THD and Torque Ripple of Induction Motor for SVPWM Control of VSI

This article presents a harmonic analysis of the stator currents of a squirrel-cage induction motor fed by a voltage source inverter with PWM space vector control (SVPWM). The influence of PWM switching frequency and dead time (dead band) of controlled transistors on THD and electromagnetic torque ripple is shown. The aim is to determine the lowest switching frequency of the transistors for which the drive will operate correctly. Characteristics were determined as functions in the form of THD (fPWM), where the least square approximation was used for stator current measurements when the PWM switching frequency was changed. The approximations were realized for simulation and experimental results. To clarify the results, the operation of hardware PWM circuits in microcontrollers is analyzed.

The Output Voltage Estimation of Power Transformer Integrated with a Three Phase T-Type Inverter

The issues related to integrating these systems into the grids continue to gain importance with the increasing use and importance of renewable energy sources. Therefore, the importance of power distribution transformers is increasing. Besides, these power distribution transformers are connected to the grid with power electronics circuits and inverters. Considering the modular inverter structures, ease of maintenance, and connection, three-level T-type inverters are chosen for this study. The secondary output voltage of the power transformer is estimated by using circuit parameters such as the dead time of the inverter circuit, PWM switching frequency, and modulation rate. Based on the finite element analysis analysis according to the selected parameters, 810 data are obtained with time-dependent parametric analysis. The adaptive neuro-fuzzy inference system model is constructed by considering the simulation data to estimate the secondary output of the power transformer of these parameters. In the training phase of the model, 648 randomly selected data from 810 data obtained by ANSYS-Electronics/Simplorer are used. The remaining 162 data are used in the testing process to measure system performance. As a result of the analysis made by ANFIS, the Root Mean Square Error (RMSE) error is found as 2.475%. Since the values obtained in the estimation process of the study are very close to the simulation values, the ANFIS method can be used as an estimation method that will give accurate results during the design phase.

Minimization Electric Losses in Transistor DC Drives

This work is devoted to develop the algorithm for determining the optimal switching frequency of a transistor pulse-width converter (PWM) to minimize the total electric losses in a DC drive. Electric losses in the armature winding and in the PWM transistors are divided into two compo-nents: static, from the direct current component, and dynamic. The latter include losses in the armature winding from the harmonic components of the current and losses in transistors from transient switching currents. Since the dynamic losses in transistors increase with increasing frequency, and in the armature winding they decrease from current harmonics, there is an optimal switching frequency value at which the total dynamic losses in the PWM drive will be minimal. This aim is achieved by solving the problem of determining the analytical dependence of dynamic electric losses in the armature winding on the PWM switching frequency and computer simulation of a transistor DC drive. As a result of the research, an analytical expression was obtained for calculating the relative dynamic electric losses in the armature winding with polyharmonic power supply. An algorithm was proposed for determining the optimal switching frequency of the PWM: 1) on computer models of the DC motor and PWM, the dependences of dynamic electrical losses on the switching frequency were determined; 2) the graph was built showing the dependence of the total dynamic electric losses, on which the point was determined of minimum losses, which corresponds to the optimal value of the switching frequency. The novelty of the work was that the theory of electric losses in the armature windings with polyharmonic power was further developed.

Feedback Linearization Based Flow Rate Control for Centrifugal Pump in Coupled-Tank Water Meter Testing System

A permanent magnet direct current (PMDC) motor centrifugal pump is intended to be used as the water supply unit in a feedback linearization based coupled-tank water meter testing system. Flow rate generated by the pump corresponds to the input variable for implementing the input-output feedback linearization to this single-input-single-output (SISO) system. The pump motor is driven by an Arm Cortex M7 based microcontroller applying the pulse-width modulation (PWM) strategy at various frequencies and pwm methods. It is aimed to determine a suitable PWM frequency and driving method in order to provide a stable flow rate at the desired duty cycle values. An H-Bridge driver integrated circuit (L298N) is used in both fast decay and slow decay modes for driving the pump motor. Flow rate measurements are carried out at 4 range of frequencies between 100 Hz and 20 kHz for each mode. Fast decay mode in low pwm frequency (100Hz) results in higher deviations at the steady-state flow rate. However, slow decay mode provides a faster reduction in motor speed despite the slower current decay, which improves the flow rate stability and minimize deviations at constant pwm duty cycle values. High pwm switching frequencies increase the energy losses resulting in a lower driving voltage range, which reduces the effective range of selection for pwm duty cycle setting of flow rate adjustment. 1 kHz PWM frequency combined with the slow-decay driving mode achieves good performance in terms of linear regression and wider range for pwm duty cycle to flow rate transformation.

Fast‐converging robust PR‐P controller designed by using symmetrical pole placement method for current control of interleaved buck converter‐based PV emulator

AbstractIn this study, the interleaved buck converter‐based photovoltaic (PV) emulator current control is presented. A proportional‐resonant‐proportional (PR‐P) controller is designed to resolve the drawbacks of conventional PI controllers in terms of phase management, which means balancing currents evenly between active phases to avoid thermally stressing and provide optimal ripple cancelation in the presence of parameter uncertainties. The resonant path of the controller (PR) with a constant proportional unity gain is designed considering the changing dynamics of a notch filter by pole placement method (adding mutually complementary poles to the notch transfer function) at PWM switching frequency. The proportional gain path (P) of the controller is used to determine the compatibility of the controller with parameter uncertainty of the phases and designed by utilizing loop‐shaping method. The proposed controller shows superior performance in terms of 10 times faster‐converging transient response, zero steady‐state error with significant reduction in current ripple. Equal load sharing that constitutes the primary concern in multiphase converters is achieved with the proposed controller. Implementing of robust control theory involving comprehensive time and frequency domain analysis reveals 13% improvement in the robust stability margin and 12‐degree bigger phase toleration with the PR‐P controller. In addition to these, the proposed unconventional design process of the controller reduces the computational complexity and provides cost‐effectiveness and simple implementation. Moreover, implementing of auxiliary resistor‐capacitor (RC) circuits parallel with the inductors to sense the current in each phase removes the need for current measurement sensors that contribute to overall cost of the system.

Induction Motor Direct Torque Control with Synchronous PWM

A novel induction motor direct torque control (DTC) algorithm with synchronous modulation is presented. Compared to the traditional DTC method, whose main drawback is the presence of low-frequency torque harmonics (sub-harmonics), in the proposed method, the PWM switching frequency is imposed to be an integer multiple of the main supply frequency. This is achieved by continuously adjusting the PWM switching period to significantly reduce low-frequency harmonics. The devised algorithm has been tested on an inverter-fed induction motor drive system, and the obtained results show an important reduction of the sub-harmonic spectral content of the developed torque with respect to a conventional direct torque control while maintaining at the same time a high dynamic response.

Combined Optimal Torque Feedforward and Modal Current Feedback Control for Low Inductance PM Motors

Small sized electric motors providing high specific torque and power are required for many mobile applications. Air gap windings technology allows to create innovative lightweight and high-power electric motors that show low phase inductances. Low inductance leads to a small motor time constant, which enables fast current and torque control, but requires a high switching frequency and short sampling time to keep current ripples and losses in an acceptable range. This paper proposes an optimal torque feedforward control method, minimizing either torque ripples or motor losses, combined with a very robust and computation-efficient modal current feedback control. Compared to well-known control methods based on the Clarke-Park Transformations, the proposed strategy reduces torque ripples and motor losses significantly and offers a very fast implementation on standard microcontrollers with high robustness, e.g., against measurement errors of rotor angle. To verify the accuracy of the proposed control method, an experimental setup was used including a wheel hub motor built with a slotless air gap winding of low inductance, a standard microcontroller and GaN (Gallium Nitride) Power Devices allowing for high PWM switching frequencies. The proposed control method was validated first by correlation of simulation and experimental results and second by comparison to conventional field-oriented control.

Development of Maximum Power Point Tracking Solar Charge Controller for 120 Volt Battery System at Pandansimo Hybrid Power Plant

Pandansimo Hybrid Power Plant (HPW) is located at Pandansimo Beach, Bantul, Yogyakarta. It has a maximum capacity of 57.5 kW, combining solar and wind energy technologies. Currently a part of it (4 kWp solar panel system) is used for ice maker machine with an efficiency merely of 60% in average. To increase efficiency of system and safety of battery charging, a special Maximum Power Point Tracking (MPPT) Solar Charge Controller is developed. This system is developed to optimize power transfer from solar panel array to battery, which is shown as solar panel characteristic in a I-V curve. The purpose of this research is to develop the MPPT Solar Charge Controller with PID algorithm for 120 volt battery system and 4 kWp solar panel. The Solar Charge Controller (SCC) design uses microcontroller system that is easy to repair and improve. The SCC component can be found easily in local electronic components stores around Yogyakarta. The SCC design involves several main parameter: PWM switching frequency 50 kHz, mosfet IRFP260 power switching device, 120 Volt battery, rated current charge of 40 ampere, and three state battery charge sequential. The result of this research are the MPPT SCC with average efficiency of more than 90%, real charge current of 30 Ampere, and PV voltage optimum of 165 Volt.

An Improved Rotor Position Estimation Method for PMSM Based on Pulsating Square-Wave-Type Voltage Injection

This paper presents a pulsating high-frequency square-wave-type voltage signal injection based sensorless rotor position estimation method for permanent magnet synchronous motors (PMSM). In order to increase the injection frequency so as to enhance the control system’s bandwidth, square-wave-type voltage is injected instead of sinusoidal voltage. To avoid disturbances, the sampling frequency is set as equal to the PWM switching frequency so that the injection frequency can be half of the switching frequency. Due to the characteristics of the square-wave-type voltage, the signal processing is further simplified without the use of filters, which can eliminate the time delay and increase the system’s computational efficiency and feasibility. As a result, the rotor position estimation performance is improved and the sensorless control system’s dynamics is enhanced. Results of simulation verify the effectiveness of the proposed method and its applicability to PMSM sensorless control systems.

Impact of the Switching Frequency on the Welding Current of a Spot-Welding System

This paper deals with an analysis of a middle-frequency resistance spot-welding (RSW) system with a dc welding current controlled by a pulsewidth modulated inverter, which supplies a welding transformer with a full-wave rectifier mounted at the secondary. Welding transformers in the automotive industry are usually mounted on the arm of a moving robot, so the weight is important. To achieve the same welding power with a large welding current, the transformer's weight can be reduced with a higher PWM switching frequency. This higher frequency allows a reduction in the transformer's iron-core cross section with shorter primary and secondary windings. Unfortunately, the leakage inductances prevent the RSW system from achieving the same nominal welding current at higher frequencies. The frequency-dependent maximum welding current is a characteristic behavior of the RSW system, which can be determined by sophisticated and time-consuming simulations or with the expensive measurements. The third option presented in this paper is determination of an analytical solution, which allows calculation of the maximum welding current as function of frequency or any parameter of the RSW system circuit model. The analytically calculated frequency-dependent function of the maximum welding current was completely confirmed by measurements on an industrial RSW system and by numerical simulations.

Large-signal stabilization of AC grid supplying voltage-source converters with LCL-filters

A robust tool compensating stability problems occurring in interconnected voltage-source rectifier loads with input passive LCL filter is developed. An LCL filter can reduce the harmonics introduced by PWM switching frequency and guarantee low currents THD using small component values comparing to the well-known L filter solution. Nevertheless, the additional poles introduced by the LC part induce resonance in the system and may lead to instability. To deal with this issue, a large-signal stabilizing supervisor based on the direct Lyapunov theorem is proposed in this contribution. The use of Lyapunov theory allows constructing feedback stabilizing signals which keep both the damping performance and robustness of the proposed stabilizer. The stability phenomenon is highlighted and the effectiveness of the proposed solution is validated by experimental results.

사파이어 실리콘 결정 성장용 80kW 10kA PWM 컨버터 시스템 개발

This paper is research result for a development of sapphire silicon ingot glowing(SSIG) PWM converter system for 80kW 10kA. The system include 3-phase AC-DC diode rectifier of input voltage AC 380V and 60Hz, DC-AC single phase full bridge PWM inverter of high frequency, AC-DC single-phase full wave rectifier using center-tapped of transformer for low voltage 8.0V and large current 10,000A of output specification, tungsten resistor load 0.1[㏁]. PWM switching frequency for IGBT inverter control set 30kHz. The suggested researching contents are designed data sheets of power converter system, PSIM simulation, operating characteristics and analysis results of developed SSIG system. This paper propose

Investigating and controlling noise of axial-flux motors for electric bicycles

Featured with high torque density and slim pancake shape, axial-flux permanent magnet (AFPM) motors fulfill most of the integration requirements for electrified vehicles. AFPM traction motors as the core of propelling power, however, may cause noise annoyance and degrade ride quality if improperly designed. A modified electric bicycle equipped with an AFPM motor was used as the research platform. The developing AFPM motor has high operating noise problem with irregular abnormal noise occurrences. This study investigates the effects of structural and motor drive designs on the noise generated by AFPM motors. The noise sources and their potential transfer paths were addressed. The relationships between the electromagnetic related frequencies and dominant noise frequencies were fully explored. In addition to examining electromagnetic frequencies, manipulating waveforms of phase currents was proposed as an effective countermeasure for noise control. Data on noise, vibration, motor structural design and motor drive are correlated and explored by using time signature, spectrum and cepstrum analyses. By establishing an index ?ph that is related to phase currents, this study showed excellent correlation between the index and the abnormal noise occurrence. Validation tests showed the motor drive scheme relating with current waveforms and PWM switching frequency was a crucial attribute to the motor vibration and noise. Furthermore, permeance variations because of the stator slotting effect caused high operating noise. With comprehensive cause-effect analysis and the effective remedies, this study reduced the operating noise from 65 dB to below 60 dB and eliminated the abnormal noise.

태양전지 실리콘 결정 성장용 120kW 3kA PWM 컨버터 시스템 개발

This paper is research result for a development of solar cell silicon ingot glowing(SCSIG) PWM converter system for 120[kW] 3[kA]. The system include 3-phase AC-DC rectifier diode converter of input voltage AC 460[V] and 60[Hz], DC-AC single phase full bridge PWM inverter of high frequency, AC-DC single-phase full wave rectifier using center-tapped of transformer for low voltage 50[V] and large current 3,000[A], carbon resistor load 0.2[mΩ]. PWM switching frequency for IGBT inverter control set 15KHz. The suggested researching contents are designed data sheets of power converter system, PSIM simulation, operating characteristics and analysis results of developed SCSIG system.

Non-isolated multiphase boost converter for a fuel cell with battery backup power system

This work describes a step-up non-isolated DC/DC converter aimed for fuel cell stand-alone power systems. The proposed converter has the following features: simple structure based on the basic boost topology that reduces the number of components; it uses the interleaving technique in order to reduce the current ripple at the input and output sides, reduction of the inductors size, higher frequency that reduce the output filter capacitor and easier power losses management. In addition, the use of an inner current control loop in the input side assures power sharing and easy module parallelization. The converter feeds a backup battery that maintains a DC voltage level at the main bus. An outer battery-charging loop controls the converter. Experimental validation is given for a four-phases 1 kW prototype at 100 kHz PWM switching frequency connected to a Nexa Ballard (1.2 kW–46 A) PEM fuel cell.

A Wideband Low-Pass Filter for Differential Mode Distortion

This paper deals with the solution for a wideband low-pass filter that can be used for filtering the input currents of switching converters, which are distorted by the switching frequency of PWM. Initially, the filter was proposed for the special type of AC converter, which is described in the paper. However, these solutions can also be used in the inputs of active PFC converters and in the outputs of PWM converters, where there are similar problems with switching frequency.The frequency band of the filter is given by the switching frequency of the filtered device and by the demands of EMC standards. This makes the filter able to work in the frequency band from 10 kHz to 30 MHz. To ensure such a frequency band, the filter should be proposed with two sections, each for a specific part of the band.

Multimode Digital Controller for Synchronous Buck Converters Operating Over Wide Ranges of Input Voltages and Load Currents

This paper describes a digital pulsewidth modulation/pulse-frequency modulation (PWM/PFM) controller with input-voltage feedforward (IVFF) for synchronous buck dc-dc converters. The controller includes automatic PWM/PFM mode switching and effective synchronous operation with a minimum number of active components and without the need for current sensing in PFM mode of operation. IVFF improves efficiency and dynamic performance over a wide range of input voltages. Controller parameters, including the PWM switching frequency, the PFM pulse period, and the mode transition point are programmable, which enables efficiency optimization. Experimental results are shown for a synchronous buck converter with 5-12 V input voltage, and 1.3 V, 0-10 A output.

The Estimation on Switching Technique via Output Power Source Analysis of Power Conversion System in an Electric Railway Vehicle

Abstract - This paper presents the estimation on switching technique via output power source analysis of power conversion unit in electric railway vehicle. The focus of this study suggested an alternative on critical problems by using head electric power(HEP). To achieve this, we have measured output power of HEP, and measurement devices set up at output of transformer connected HEP to analysis quality on output power source of head electric power(HEP) unit in electric railway vehicle. Using results of measurement of it, parameters are assumed for simulation to confirm estimation on switching technique. It is confirmed that switching technique is Selected Harmonic Elimination PWM(SHEPWM) and inverter switching frequency is less than 500[Hz].Throughout experiment and simulation, it is estimated that switching technique used HEP is advanced SHEPWM and switching frequency is about 300[Hz]. Also leakage inductance in transformer is about 180[μH] less than 365[μH] known.Key Words : Switching Technique, Head Electric Power(HEP), Selected Harmonic Elimination PWM(SHEPWM)

Reliability through increased safety insulation systems: the effect of high-speed switching on the motor insulation system

The dominant electrical machine in industrial general-purpose drives continues to be the efficient, robust, reliable inexpensive induction motor. Continuous development ensures they can accommodate electronic waveforms, although less than 10% are currently used with drives. Higher PWM switching frequencies combined with faster switching devices in the last ten years have caused a ten-fold increase in the rate of change of voltage applied to a motor. This can be accompanied with an increased peak voltage due to the pulse train propagation to the motor and reflection, dependent on the rise time and cable length. Although these waveforms age the insulation system, the reduced reliability is overcome through modern increased safety insulation systems. This article summarises the principles that provide user confidence in modern improved insulation systems. It provides a challenge to drive manufacturers to review their approach to future products.