Frequency Pulse Width Modulation Research Articles

Study of complex dynamics of DC-DC buck converter

Switched-mode power converter circuits are non-linear and time varying in nature. In this work, non-linear dynamics for both voltage- and current-mode-controlled DC-DC buck converter has been investigated through simulation and practical study. The converter is controlled by naturally sampled constant frequency pulse width modulation signals in continuous conduction mode and converter exhibits fundamental, subharmonics and chaotic oscillations for the variation of circuit parameters. In computational study, the model of buck converter is simulated by non-autonomous differential equations and finally the computational waveforms have been verified with experimental results. Here, the main objective of this research work is to study the experimental chaos and to identify the subharmonic and chaotic oscillation zones for specific parameter values that will help the power electronic engineers to design chaos-free power supply. It has been observed that the route to chaos is achieved by period doubling in the buck converter. In order to verify the computational study, laboratory prototype of closed-loop buck converter has been fabricated. The results obtained from simulation and experimental study have been presented and compared.

A Low Frequency PWM Based Multilevel DC-Link Inverter with Cascaded Sources

This paper presents a novel Cascaded Sources Multilevel DC Link (CSMLDCL) configuration to an H-bridge inverter, which effectively reduces the number of components to achieve a preferred voltage level. The CSMLDCL topology provides a dc output voltage with the shape of a staircase approximating the rectified shape of a desired sinusoidal wave. A set of area equalization based low frequency Pulse Width Modulation (PWM) techniques suitable for multi-level inverters is suggested. The objective of the new switching strategies is to lower the Total Harmonic Distortion (THD) apart from minimizing the switching losses. Simulation and experimental results of a seven-level inverter are included to illustrate the operating principle and highlight the merits of the proposed strategy.

High Frequency High Power Full Bridge Converter for Plasma Torches

This paper presents a full bridge converter with a high speed rectifier and filter for plasma torches. Full bridge circuit with high frequency pulse width modulation control is used and high frequency transformer to insulate is adopted. For Argon (Ar) gas Plasma Torches, and by increasing the pulse width the average power consumption has modified from 1KW to 5.6KW (positive load). For Nitrogen (N2) gas Plasma Torches, and by increasing the pulse width the average power consumption has reduced from 7.7KW down to 3KW (negative load). For the Plasma Torches load the frequency of converter was steady at 50KHz.

Features of modes of a multizone integrating controller with an even number of relay elements

Operation modes of an integrating multizone controller with pulse-width modulation frequency and an even number of relay elements are discussed. Integrating multizone controllers have high noise protection, precision, multifunctionality, and simple technical realization. Due to such properties, they make it possible to solve an entire complex of technical problems to improve the resource and energy-efficiency characteristics of systems of technological process control based on these controllers. A block scheme of a multizone regulator with an even number of relay elements is given. Time diagrams of a multizone controller with two and four relay elements are shown so as to explain the principles of its operation. Based on this analysis, recommendations are given for the use of a multizone controller in low-voltage information devices, in particular, in regulators, sensors, etc. The field of application of integrating multizone controllers in control systems of electric drives in technological devices is determined. In particular, an example of construction of a discrete control system of a group of electric drives with parallel control channels is discussed. The block scheme of a discrete control system of the group with an odd number of asynchronous electric water-pump drives controlled by thyristor regulators is presented. Such a solution provides soft-start electric drives with a predetermined limiter of starting current. In the proposed scheme, the main disadvantage of a multizone system with an even number of relay elements is eliminated. In particular, blocking of additional relay element commutation is implemented when the multizone controller switches from one modulation zone to another.

Influence of Driving Current on Photometric Performances of a White Light OLED

In this paper, we demonstrate how driving current affects photometric performances of a white light organic light emitting diode (OLED) for general lighting purpose. Experiments reveal that a ripple current with 40% amplitude, 50-Hz–100-kHz frequency, and sinusoidal and triangle waveform has little influence on the test OLED. In the pulse-width modulation mode, both duty cycle and frequency of pulse current affect OLED's performance, and more particularly, their efficacy and correlated color temperature. Such influences become worse at high frequency and low duty cycle. The reason for this influence is a considerable difference between electron and hole mobility, and a time-dependent distribution of charge carrier within the structure leading to a movement of recombination zone therefrom.

Volume Flow Characterization of PWM-Controlled Fast-Switching Pneumatic Valves

In this paper we present results of an experimental analysis of the dependence of volume flow on pulse width modulation (PWM) control signal through a fast-switching pneumatic valve. The main goal of this study is to determine how the PWM frequency and duty cycle (pulse width) influence the volume flow and if there is a correlation between them. The highest PWM signal frequencies that can control the tested fastswitching valve were used. This way we minimised the influence of pressure pulsation that can make a pneumatic system, pressure regulator and flow sensor unstable at lower frequencies. The aim was also to determine if pressure difference and PWM frequency have any influence on the shortest pulse needed to open the valve. The volume flow was measured with a state-of-the-art mass flow sensor that can calculate average volume flow and isn’t influenced by high-frequency pressure pulsation. We also made temperature measurement in a valve solenoid and pressure chamber during an 8-hour excitation with a PWM signal.

Piezoelectric transformer-based high conversion ratio interface for driving dielectric actuator in microrobotic applications

Dielectric actuators are utilized to convert electrical power into mechanical strain with considerable potential in microrobotic applications. However, critical challenges that need to be addressed include high-voltage interface with high conversion ratio, light weight, small size, and high power density. This study proposes a high piezoelectric transformer-based high conversion ratio interface that is integrated with a direct current/direct current high conversion ratio boost stage and a direct current/alternating current high-voltage driving stage. A piezoelectric transformer-based class-E zero voltage switching direct current/direct current interface is controlled by a hybrid pulse frequency modulation and pulse width modulation control strategies to obtain the desired high step-up ratio in the direct current/direct current stage. A half-bridge converter with special digital control algorithm in the direct current/alternating current stage is designed to convert high direct current voltage into arbitrary unipolar signal driving dielectric actuators. A prototype 23.3 g and 4 W interface has been fabricated for experimental validation to verify its ability to drive a 1 kV input dielectric actuator at 5 Hz in microrobotic applications.

Modeling, Dynamics, Bifurcation Behavior and Stability Analysis of a DC–DC Boost Converter in Photovoltaic Systems

A study of a DC–DC boost converter fed by a photovoltaic (PV) generator and supplying a constant voltage load is presented. The input port of the converter is controlled using fixed frequency pulse width modulation (PWM) based on the loss-free resistor (LFR) concept whose parameter is selected with the aim to force the PV generator to work at its maximum power point. Under this control strategy, it is shown that the system can exhibit complex nonlinear behaviors for certain ranges of parameter values. First, using the nonlinear models of the converter and the PV source, the dynamics of the system are explored in terms of some of its parameters such as the proportional gain of the controller and the output DC bus voltage. To present a comprehensive approach to the overall system behavior under parameter changes, a series of bifurcation diagrams are computed from the circuit-level switched model and from a simplified model both implemented in PSIM© software showing a remarkable agreement. These diagrams show that the first instability that takes place in the system period-1 orbit when a primary parameter is varied is a smooth period-doubling bifurcation and that the nonlinearity of the PV generator is irrelevant for predicting this phenomenon. Different bifurcation scenarios can take place for the resulting period-2 subharmonic regime depending on a secondary bifurcation parameter. The boundary between the desired period-1 orbit and subharmonic oscillation resulting from period-doubling in the parameter space is obtained by calculating the eigenvalues of the monodromy matrix of the simplified model. The results from this model have been validated with time-domain numerical simulation using the circuit-level switched model and also experimentally from a laboratory prototype. This study can help in selecting the parameter values of the circuit in order to delimit the region of period-1 operation of the converter which is of practical interest in PV systems.

Natural Balancing of the Neutral Point Potential of a Three-Level Inverter with Improved Firefly Algorithm

Modern power systems driven by high-power converters have become inevitable in view of the ever increasing demand for electric power. The total power loss can be reduced by limiting the switching losses in such power converters; increased power efficiency can thus be achieved. A reduced switching frequency that is less than a few hundreds of hertz is applied to power converters that produce output waveforms with high distortion. Selective harmonic elimination pulse width modulation (SHEPWM) is an optimized low switching frequency pulse width modulation method that is based on offline estimation. This method can pre-program the harmonic profile of the output waveform over a range of modulation indices to eliminate low-order harmonics. In this paper, a SHEPWM scheme for three-phase three-leg neutral point clamped inverter is proposed. Aside from eliminating the selected harmonics, the DC capacitor voltages at the DC bus are also balanced because of the symmetrical pulse pattern over a quarter cycle of the period. The technique utilized in the estimation of switching angles involves the firefly algorithm (FA). Compared with other techniques, FA is more robust and entails less computation time. Simulation in the MATLAB/SIMULINK environment and experimental verification in the very large scale integration platform with Spartan 6A DSP are performed to prove the validity of the proposed technique.

Fault-tolerant design approach for reliable offshore multi-megawatt variable frequency converters

Inverters play a key role in realizing reliable multi-megawatt power electronic converters used in offshore applications, as their failure leads to production losses and impairs safety. The performance of high power handing semiconductor devices with high speed control capabilities and redundant configurations helps in realizing a fault-tolerant design. This paper describes the reliability modeling done for an industry standard, 3-level neutral point clamped multi-megawatt inverter, the significance of semiconductor redundancy in reducing inverter failure rates, and proposes methods for achieving static and dynamic redundancy in series connected press pack type insulated gate bipolar transistors (IGBT). It is identified that, with the multi megawatt inverter having 3+2 IGBT in each half leg with dynamic redundancy incorporated, it is possible to reduce the failure rate of the inverter from 53.8% to 15% in 5 years of continuous operation. The simulation results indicate that with dynamic redundancy, it is possible to force an untriggered press pack IGBT to short circuit in <1s, when operated with a pulse width modulation frequency of 1kHz.

State dependent model predictive control for orbital rendezvous using pulse-width pulse-frequency modulated thrusters

This paper studies the pulse-width pulse-frequency modulation based trajectory planning for orbital rendezvous and proximity maneuvering near a non-cooperative spacecraft in an elliptical orbit. The problem is formulated by converting the continuous control input, output from the state dependent model predictive control, into a sequence of pulses of constant magnitude by controlling firing frequency and duration of constant-magnitude thrusters. The state dependent model predictive control is derived by minimizing the control error of states and control roughness of control input for a safe, smooth and fuel efficient approaching trajectory. The resulting nonlinear programming problem is converted into a series of quadratic programming problem and solved by numerical iteration using the receding horizon strategy. The numerical results show that the proposed state dependent model predictive control with the pulse-width pulse-frequency modulation is able to effectively generate optimized trajectories using equivalent control pulses for the proximity maneuvering with less energy consumption.

Integrated platform for motor stator sound power determination

This paper presents a unique approach for integrating the electromagnetic forces of a motor with the sound pressure level radiated from its stator frame. In addition, the effects of the inverter's pulse-width modulation (PWM) carrier frequency on the level of radiated noise are analysed. Four ANSYS modules, namely, Simplorer, Maxwell, Mechanical, and Acoustics, are used to develop the control circuit, to calculate the electromagnetic forces of the motor, to simulate the mechanical structure of the stator frame, and, finally, to predict the radiated noise. A Prius 2004 internal permanent magnet motor was selected for the study due to the availability of this motor's design details. An optimum PWM frequency was identified and a trap filter was designed for the noise reduction. A simple experiment setup was built to validate the correlation of the PWM switching frequency with the motor's radiated noise.

A PWM and PFM Hybrid Modulated Three-Port Converter for a Standalone PV/Battery Power System

A pulsewidth modulation (PWM) and pulse frequency modulation (PFM) hybrid modulated three-port converter (TPC) interfacing a photovoltaic (PV) source, a storage battery, and a load is proposed for a standalone PV/battery power system. The TPC is derived by integrating a two-phase interleaved boost circuit and a full-bridge $LLC$ resonant circuit. Hence, it features a reduced number of switches, lower cost, and single-stage power conversion between any two of the three ports. With the PWM and PFM hybrid modulation strategy, the dc voltage gain from the PV to the load is wide, the input current ripple is small, and flexible power management among three ports can be easily achieved. Moreover, all primary switches turn ON with zero-voltage switching (ZVS), while all secondary diodes operate with zero-current switching over full operating range, which is beneficial for reducing switching losses, switch voltage stress, and electromagnetic interference. The topology derivation and power transfer analysis are presented. Depending on the resonant states, two different operation modes are identified and explored. Then, main characteristics, including the gain, input current ripple, and ZVS, are analyzed and compared. Furthermore, guidelines for parameter design and optimization are given as well. Finally, a 500-W laboratory prototype is built and tested to verify the effectiveness and advantages of all proposals.

Mathematical modeling of spacecraft guidance and control system in 3D space orbit transfer mission

Spacecraft performance in an orbital maneuver relies on guidance and control systems which manage the thrust direction within orbit transfer. In this article, the guidance and control approach for spacecraft having a 3D orbit transfer mission is proposed. To derive the optimal variation of steering angles with initial and terminal constraints on the space orbits, a mathematics polynomial function of the guidance command with unknown coefficients is introduced, one of which is determined to achieve the transfer accuracy requirement between space orbits. Genetic Algorithm is employed in finding optimal variation of guidance command and the optimal initial states within the transfer. The attitude control system is also modeled to evaluate the spacecraft response with respect to generated commands by the guidance system. Gas thrusters are considered as attitude actuators for space mission and linear controller with pulse-width pulse-frequency modulator and unconstrained control allocation is employed for controlling steering angles. Results indicate that the presented approach for guidance and control system fairly satisfies the mission requirement.

Anticogging: Torque ripple suppression, modeling, and parameter selection

Smooth motion is critical to some robotic applications such as haptics or those requiring high precision force control. These systems are often direct-drive, so any torque ripple in the motor output must be minimal. Unfortunately, low-torque ripple motors are expensive. Low cost brushless direct current motors are becoming more prevalent, especially from the hobby remote control community. These motors often have the required high-torque density; however, they also have significant torque ripple. This paper presents a low cost method for anticogging, the compensation of cogging torque. While other methods exist to compensate for current-based torque ripple (mutual or reluctance torque), none have addressed cogging torque, except by adding expensive force sensors. This paper presents two methods that use a position sensor (already present for servo motors) to map cogging torque to rotor position. The map is played back according to position reported from the sensor to cancel the cogging torque. The design and testing of a low cost haptic arm using anticogging shows validation; however, the approach is much broader, and can be applied to any precision force application. A model of torque ripple sources are included as a function of pulse-width modulation frequency to help choose the optimal pulse-width modulation frequency to minimize torque ripple. Test results on eleven different motors show a removal of up to 88% of torque ripple with no added cost in robotic servo applications, and in some cases having better performance than motors that are over nine times as expensive.

Using d–q Transformation to Vary the Switching Frequency for Interior Permanent Magnet Synchronous Motor Drive Systems

The switching frequency is one of the most important control parameters of the dc/ac inverter. In most motor drives for transportation, it is set as a constant value at some specific torque or speed. The variable switching frequency pulse width modulation (VSFPWM), which changes the switching frequency cycle to cycle based on a current ripple prediction method, has been proposed in previous literatures and realized in resistance—inductance (RL) loads and induction motors (IMs). It proves effective to increase the overall system efficiency and improve electromagnetic interference (EMI) performance. However, the previous current ripple prediction method encounters difficulty in dealing with more complex motors, e.g., interior permanent magnet (IPM) motors, which is widely used in electric vehicles. As a result, the benefits of VSFPWM cannot be fully utilized for IPM drive systems. This paper proposed a new current ripple prediction method using the d–q transformation instead of the conventional Thevenin equivalent circuit method and successfully implemented VSFPWM to IPM drives. Simulation and experiments on a 400-V IPM test bench validated the effectiveness of the method, which will vary the switching frequency from cycle to cycle in order to 1) restrain the three-phase current ripples; 2) increase the overall system efficiency; and 3) enhance the system electromagnetic capability (EMC).

Novel Full-Bridge PWM Resonant Converter: Analysis and Implementation

ABSTRACTA soft-switching full-bridge converter for renewable energy conversion applications is presented. Phase-shifted full-bridge DC/DC converter with a resonant tank is used to realize zero-voltage switching turn-on for switches and zero-current switching for rectifier diodes within nearly entire load range. Therefore, the switching losses of switches and rectifier diodes are improved. To overcome the drawback of a wide range of switching frequency in the conventional resonant converters, fixed frequency pulse-width modulation is adopted to generate the switching signals and also to regulate the output voltage. The transformer primary and secondary windings are connected in parallel and series, respectively, to reduce the current ratings of transformer primary windings and also balance the primary currents for low input voltage applications. Full-bridge diode rectifier is used to reduce the voltage ratings of rectifier diodes for high output voltage applications. Experiments are provided to verify the theoretical analysis and performance of the proposed circuit.

An Analysis Approach for the Assessment of Pulse-width Modulated Carrier Frequency Spectral Components in Power Distribution Systems with Photovoltaic Resources

Power distribution systems may have photovoltaic resources, and these resources may interface with the AC system via pulse-width modulated inverters. The pulse-width modulated currents have high-frequency spectra due to the switching frequency, which is typically 2.0–20 kHz. These carrier frequency components are asynchronous to the “power frequency” (the “baseband,” which is 50 or 60 Hz). Residential photovoltaic resources are in the 2–5 kW range, and “utility-scale” photovoltaic resources may be in the range of 500 kW. The pulse-width modulated carrier frequency components of voltage and current propagate in the power distribution system, and the details of this propagation are described. Note that the pulse-width modulated voltages are not harmonics of the 60-Hz baseband frequency, nor are the several pulse-width modulated voltages generally synchronous with each other. The objective is to describe an analytical approach for the assessment of carrier frequency spectra in distribution systems with photovoltaic resources. Analysis tools and experience with those tools are given. Information is given to distribution engineers faced with systems with pulse-width modulated inverter resources and advice on frequency ranges of study, potential modeling inaccuracies, and software tools. The results of a study on an actual high penetration solar photovoltaic feeder are given.

Three-Phase High-Power and Zero-Current-Switching OBC for Plug-In Electric Vehicles

In this paper, an interleaved high-power zero-current-switching (ZCS) onboard charger (OBC) based on the three-phase single-switch buck rectifier is proposed for application to plug-in electric vehicles (EVs). The multi-resonant structure is used to achieve high efficiency and high power density, which are necessary to reduce the volume and weight of the OBC. This study focuses on the border conditions of ZCS converting with a battery load, which means the variation ranges of the output voltage and current are very large. Furthermore, a novel hybrid control method combining pulse frequency modulation (PFM) and pulse width modulation (PWM) together is presented to ensure a driving frequency higher than 10 kHz, and this will reduce the unexpected inner resonant power flow and decrease the total harmonic distortion (THD) of the input current under a light load at the end of the charging process. Finally, a prototype is established, and experiments are carried out. According to the experimental results, the conversion efficiency is higher than 93.5%, the THD about 4.3% and power factor (PF) 0.98 under the maximum power output condition. Besides, a three-stage charging process is also carried out the experimental platform.

Full quaternion based finite-time cascade attitude control approach via pulse modulation synthesis for a spacecraft

In the aspect of further development of investigations in the area of spacecraft modeling and analysis of the control scheme, a new hybrid finite-time robust three-axis cascade attitude control approach is proposed via pulse modulation synthesis. The full quaternion based control approach proposed here is organized in association with both the inner and the outer closed loops. It is shown that the inner closed loop, which consists of the sliding mode finite-time control approach, the pulse width pulse frequency modulator, the control allocation and finally the dynamics of the spacecraft is realized to track the three-axis referenced commands of the angular velocities. The pulse width pulse frequency modulators are in fact employed in the inner closed loop to accommodate the control signals to a number of on–off thrusters, while the control allocation algorithm provides the commanded firing times for the reaction control thrusters in the overactuated spacecraft. Hereinafter, the outer closed loop, which consists of the proportional linear control approach and the kinematics of the spacecraft is correspondingly designed to deal with the attitude angles that are presented by quaternion vector. It should be noted that the main motivation of the present research is to realize a hybrid control method by using linear and nonlinear terms and to provide a reliable and robust control structure, which is able to track time varying three-axis referenced commands. Subsequently, a stability analysis is presented to verify the performance of the overall proposed cascade attitude control approach. To prove the effectiveness of the presented approach, a thorough investigation is presented compared to a number of recent corresponding benchmarks.