Frequency Pulse Width Modulation Research Articles

Design and implementation of an innovative single-phase direct AC-AC bipolar voltage buck converter with enhanced control topology

Direct AC–AC converters are strong candidates in the power converting system to regulate grid voltage against the perturbation in the line voltage and to acquire frequency regulation at discrete step levels in variable speed drivers for industrial systems. All such applications require the inverted and non-inverted form of the input voltage across the output with voltage-regulating capabilities. The required value of the output frequency is gained with the proper arrangement of the number of positive and negative pulses of the input voltage across the output terminals. The period of each such pulse for low-frequency operation is almost the same as the half period of the input grid or utility voltage. These output pulses are generated by converting the positive and negative input half cycles in noninverting and inverting forms as per requirement. There is no control complication to generate control signals used to adjust the load frequency as the operating period of the switching devices is normally greater than the period of the source voltage. However, high-frequency pulse width modulated (PWM) control signals are used to regulate the output voltage. The size of the inductor and capacitor is inversely related to the value of the switching frequency. Similarly, the ripple contents of voltage and currents in these filtering components are also inversely linked with PWM frequency. These constraints motivate the circuit designer to select high PWM frequency. However, the alignment of the high-frequency control input with the variation in the input source voltage is a big challenge for a design engineer as the switching period of a high-frequency signal normally lies in the microsecond. It is also required to operate some high-frequency devices for various half cycles of the source voltage, creating control complications as the polarities of the half cycles are continuously changing. This requires at least the generation of two high-frequency signals for different intervals. The interruption of the filtering inductor current is a big source of high voltage surges in circuits where the high-frequency transistors operate in a complementary way. This may be due to internal defects in the switching transistors or some unnecessary inherent delay in their control signals. In this research work, a simplified AC–AC converter is developed that does not need alignment of high-frequency control with the polarity of the source voltage. With this approach, high-frequency signals can be generated with the help of any analog or digital control system. By applying this technique, only one high-frequency control signal is generated and applied in AC circuits, as in a DC converter, without applying a highly sensitive polarity sensing circuit. So, controlling complications is drastically simplified. The circuit and configuration always avoid the current interruption problem of filtering the inductor. The proposed control and circuit topology are tested both in computer-based simulation and practically developed circuits. The results obtained from these platforms endorse the effectiveness and validation of the proposed work.

Performance analysis for induction motor fed by reduced switch symmetrical multilevel inverter topology

Due to its capacity to supply more voltage levels than conventional 2-level inverters, multilevel inverters have attracted a lot of attention in recent years. Multilevel inverters may produce output waveforms that nearly approximate sinusoidal waveforms because to this characteristic, which also significantly lowers harmonic distortion. In many different power conversion systems, the introduction of reduced switch symmetrical multilevel inverter topologies has drawn significant interest. Numerous benefits, such as higher output voltage quality, reduced harmonic distortions, and increased power conversion efficiency, are provided by these novel topologies. The inclusion of these inverters in the feeding of induction motors is one of their many prominent uses. In this paper, a generalized topology is presented that generates nine levels using nine switching devices. To reduce complexity, switching pulses are generated using a low frequency pulse width modulation technique. MATLAB/Simulink is used to analyze the performance assessment of a unique three-phase symmetric cascaded multilevel inverter-based reduced switch symmetrical inverter fed induction motor drive, brushless DC (BLDC) motor and grid has been verified. According to the findings the total harmonic distortion (THD) is found to be 15% for a three-phase system and as the number of levels increases to 17 level the THD is 7.10%.

PCC Voltage Switching Harmonic Mitigation by Periodic Carrier Frequency Pulsewidth Modulation for SiC High-Frequency Active Power Filter

PCC Voltage Switching Harmonic Mitigation by Periodic Carrier Frequency Pulsewidth Modulation for SiC High-Frequency Active Power Filter

A novel unloading strategy for solar sails using reflectivity control device

For near-Earth spacecraft, many environmental forces are utilized to unload reaction wheels. However, effects like magnetic force or atmospheric friction hardly exist in deep-space environments where solar sails operate. Thus, this paper proposes an unloading method that uses reflectivity control devices to generate Solar Radiation Pressure (SRP) torque to conduct the unloading process of solar sails operating in deep space. Firstly, the basic principles of the Reflectivity Control Device (RCD), satellite kinetic model, and Pulse Width Pulse Frequency (PWPF) modulator are given. Secondly, based on the torque envelope obtained by traversing all switch combinations of RCD, a novel strategy using a PWPF modulator is specially designed to achieve efficient unloading. In the end, we carry out numerical simulations and analyze the influence of different parameters, through which the validity of the proposed torque resolution scheme is demonstrated.

Formation of magnetic double emulsions under steady and variable magnetic fields from a 3D-printed coaxial capillary device

BackgroundDouble emulsions (DEs) have attracted researchers’ attention to be utilized as a promising platform in biomedical and chemical applications. Several actuation mechanisms have been proposed for the generation of DEs. The conventional DE formation approaches (e.g. two-stage emulsification) suffer from low monodispersity. The electric actuation (i.e. coaxial electrospray technology) has been demonstrated as a controllable method for the DE formation, while the capability of magnetic actuation has not been studied yet. ResultIn the present study, the generation of ferrofluid double emulsions (FDEs), made from water-based ferrofluid as a core and oil as a shell, under the magnetic actuation of a permanent magnet with a steady magnetic field and an electromagnet with DC and pulse width modulation (PWM) magnetic fields was investigated with a simple controllable setup fabricated using 3D printing. The effect of various parameters affecting the FDE formation, such as the fluid flow rates, the magnetic field type, the magnetic flux density, and the PWM frequency and duty cycle, on the FDE formation characteristics, including the inner and outer equivalent diameters, and the formation frequency was studied. Under the steady magnetic field, two regimes of the FDE formation were identified: inertia-dominated and magnet-dominated. SignificanceWireless power-free magnetic actuation provides better control over the FDE formation, enhancing this process by increasing the FDE formation frequency with high monodispersity. The PWM magnetic field offers excellent controllability over the FDE formation with low-volume or no, in some cases, satellite droplets by tuning the PWM frequency and the duty cycle.

Design of Brushless DC Motor Driver Based on Bootstrap Circuit

Brushless DC (BLDC) motor is a three-phase motor that cannot work directly with DC current but requires electronic commutation to replace the brush function in DC motor. This paper aims to implement BLDC motor driver integration based on bootstrap circuit using Autodesk Eagle. The driver board consist of bootstrap circuit based on IR2110, MOSFETs, three voltage regulator, ESP32 microcontroller and ACS712 current sensor connection, logic level converter, and BLDC hall effect signal sensor conditioning. The research proposes bootstrap capacitor calculation based on charging/discharging capacitor principle and the minimum motor speed rotation. The implemented driver has 14x10 cm dimension tested to drive 24V/135W/6000rpm sensored BLDC motor using six steps commutation with pulse width modulation (PWM) inserted programmatically in ESP 32 to drive the high side MOSFET of the driver without AND gate circuit. The effect of pwm frequency and dutycycle variation to the speed and current of the motor is investigated. The results showed that the driver with both 12 V and 24 V voltage source and 68 μF bootstrap capacitor work optimally in 20 KHz PWM frequency both in open loop and closed loop speed control test. The motor reach 129 W for the largest power and 5250 rpm for the fastest speed in 24 V supply.

Application of soft computing algorithms for hybrid modular multilevel inverters

This study utilized Harris Hawk optimization to analyze the harmonic distortions of a symmetric capacitor based multilevel converter. The proposed multilevel converter uses identical and symmetric DC sources in its input. The proposed topology for a multilevel converter uses fewer switches than typical cascaded designs. It can output 9-level outputs and can be scaled up to higher levels. The proposed multilevel converter can be improved by implementing a low frequency pulse width modulation technique to reduce the stress on the switches. The optimization of the switching angles using Harris Hawk was able to solve the non-linear aspects of the Selective Harmonic Elimination Pulse Width Modulation. The output voltage's THD was compared with that of other optimization methods, such as ant colony and particle swarm. The comparison shows that the output THD of the Harris Hawk optimizer is lower than that of other methods, which is about 5 %, according to the standards of IEEE-519.

A High-Capacity Interleaved Parallel Full-Bridge LLC Converter for External Charging Applications

This paper explores innovative converter designs tailored to meet the evolving demands of modern electric vehicle (EV) charging and power conversion systems. The first investigation centres on an AC to DC converter featuring an input series inductor and an output capacitor, enhancing power factor correction, reducing harmonics, and optimizing voltage regulation through advanced simulation tools. Comparative analysis highlights its superior power factor maintenance and efficiency. The second proposal introduces an interleaved parallel LLC (Inductor-Inductor-Capacitor) DC/DC converter, incorporating hybrid pulse frequency modulation (PFM) and pulse width modulation (PWM) control. This design extends the adjustable output voltage range, ensuring precise voltage control. A meticulous analysis and parametric design demonstrate an output voltage range of 50–80 V and a maximum power of 20 kW through simulation results. These innovations hold promise for various applications, including renewable energy, electronic device power supplies, and EV charging, offering practical solutions to enhance energy efficiency and power quality across modern electrical systems and EV infrastructure.

Сравнительный анализ математических описаний и методов широтно-импульсной модуляции

The article considers the mathematical description and comparison of the most common methods of pulse-width modulation (PWM) for a three-phase voltage inverter, namely vector PWM, PWM with third harmonic premodulation and classical PWM. In contrast to the classical mathematical description of PWM, a description is presented that is close to the implementation of modulation using modern microcontroller technology. The classic representation of PWM is based on comparing two signals. In this representation, the modulation pulse occurs at the moment when the modulating function is greater in value than the reference signal. When implementing PWM by a microcontroller, the pulse is placed within the period symmetrically with respect to the middle of the interval, while the pulse width is determined by the average value of the voltage modulating function. With a different mathematical description of PWM, the pulse is located differently within the modulation interval. There are presented the results of modeling and compares the mathematical descriptions of PWM methods according to the criterion of minimum dispersion of the current flowing in the load. As a result of the comparison, it was revealed that the same, differently described PWM algorithm gives different results. A comparison of vector PWM with a modified vector PWM was made. The modification consists in applying a dynamic pulse shift algorithm in such a way as to obtain a minimum of current dispersion in the load. Comparison of PWM methods was carried out at different frequencies of the reference signal; a static RL circuit was used as a load when simulating a three-phase voltage inverter. The results obtained allow us to recommend a pulse shift algorithm for implementing PWM in voltage inverters operating at relatively low PWM frequencies. Minimization of the current dispersion makes it possible to obtain improved energy and vibration-noise characteristics of the electric drive.

A control method for acoustic radiation force of ultrahigh frequency ultrasound based on variable frequency pulse width modulation

Ultrahigh frequency ultrasound (>60 MHz) has emerged as a crucial actuating mechanism for non-contact manipulation, owing to its unique acoustic field properties. The acoustic field traps microparticles mainly via the gradient force of acoustic radiation force (ARF) on the transverse plane, which is up to hundreds of nanonewtons. In theory, directly using ARF can strengthen the manipulation force. Currently, the direct implementation of ARF is restricted to a specific frequency and magnitude range, which lacks a comprehensive and versatile control method. Additionally, it lacks an ARF calibration method that accommodates a wide magnitude and frequency range. We propose a variable frequency pulse width modulation-based control method for ARF, which uses an atomic force microscope microcantilever as a mechanical sensor to calibrate the magnitude and frequency. The precise control of ARF emitted by an 85 MHz transducer was achieved with a resolution of hundreds of piconewtons, magnitude range spanning from nanonewtons to micronewtons, and frequency range of 1 kHz to hundreds of kilohertz. This control method breakthrough holds great promise for expanding the application of ultrahigh frequency ultrasound in noncontact manipulation.

Highly Efficient Three-Phase Bi-Directional SiC DC–AC Inverter for Electric Vehicle Flywheel Emulator

Flywheels are nowadays a solution for the dynamic charging of electric vehicles since they act as transient energy storage. The need for a top efficient reversible power converter for the flywheel system is crucial to assure high dynamic performance. The paper presents the design of a 50 kW highly efficient reversible three-phase DC–AC inverter involving the most recent silicon carbide metal oxide semiconductor field effect transistors, and its experimental validation on a home-made emulator. Highest efficiency in reversible mode, compactness, and thermal enhancement are the targeted objectives that have been achieved. The power converter prototype evaluated on an original pulse width modulation testing-bench is able to emulate the working of the flywheel system. High frequency pulse width modulation switching, speed cycle operating, and thermal losses are evaluated. In addition, an efficiency above 99% for the converter has been attained, enabling robust functioning of the flywheel system emulator to perform specific charging profiles for electric vehicles.

Photovoltaic Power Generation Based on Three-port DC-DC Step-down Circuit

In this paper, the photovoltaic cell is combined with the analog battery pack and the load through a three-port DC-DC Buck circuit, which gives power to the analog battery pack and load. From the perspective of simulation, the photovoltaic cell is lowered to reach respective specific values through the two Buck circuits at the output end of it and to give power to the load and the simulated battery pack. The influence of Pulse Width Modulation (PWM) duty ratio output on voltage and the influence of PWM frequency on load voltage and current limiting resistance of the power supply system is studied from the angle of power conversion. The results show that when the PWM duty ratio is changed, the actual output voltage does not reach the theoretical value, and is somewhat less than the theoretical value. When the frequency is less than 100 KHz and the inductance value is less than or equal to 100 uH, under the same other conditions, the load voltage decreases first and then increases with the increase of frequency. The larger the inductance value is, the faster the voltage drops, and the smaller the inductance value is, the faster the voltage increases. When the inductance reaches 250 uH, the inductance value continues to increase, which has little influence on the load voltage, and the load voltage generated by different inductance values only has a small error. If the output frequency of PMW is too high or too low, the output voltage will be reduced. The maximum voltage value is between 90 and 100 KHz. When the current limiting resistance is 18.5 Ω, it is close to and does not exceed the maximum charging voltage of the analog battery string.

Keeping a Constant Level of Losses in the Low-Voltage Cells of a High-Voltage Multilevel Frequency Converter in Emergency Modes of Its Operation

High-voltage adjustable-frequency drives require special inverters for their operation. A cascaded multilevel frequency converter constructed on the basis of a multi-winding transformer and a set of low-voltage cells has received a widespread use. The main advantage of this converter topology are a low harmonic distortion level of the output voltage and current waveforms, as well as high reliability owing to the possibility to exclude a failed cell from operation without the need to shut down the drive. For equalizing the losses among the converter’s power cells, a pulse-width modulation (PWM) algorithm with a “walking” cell has been developed. Owing to a series connection of the cells, the effective PWM frequency is increased in proportion to the number of cells. However, if one cell fails, the switching frequency of the cells remained in operation increases in comparison with the switching frequency of phase cells when all of them are in the healthy state. This results in a growth of switching losses in the phase with one of its cells taken out from operation. The article discusses a control algorithm with which the nominal level of losses is kept in the cells of all phases under emergency operation conditions. The proposed algorithm has been verified on a model, in which a uniform distribution of losses and high quality of the output voltage have been obtained.

Variable switching frequency PWM for quasi‐Z‐Source inverter based on DC current ripple prediction

AbstractHerein, a variable switching frequency pulse width (VSFPWM) modulation strategy for quasi‐Z‐source inverter (qZSI) based on a recently proposed modulation method, named as ZSVM8, is proposed. The formulae of quasi‐Z‐source inverter inductor current ripple of ZSVM8 are deduced in detail, and a prediction model for the current ripple is obtained. Combining with the VSFPWM technique, an improved modulation method named ZSVM8 VSFPWM is proposed to further reduce the switching times without increasing the maximum inductor current ripple. As a result, the switching losses can be reduced compared with the conventional ZSVM8. Besides, ZSVM8 VSFPWM also suppresses electromagnetic interference noise, such as current EMI and common‐mode voltage. Simulations and hardware experimental results are implemented to verify the efficacies of the proposed modulation method.

Assessment of PWM Solenoid Valves to Manipulate Hollow-Cone Nozzles with Different Modulation Frequencies

HighlightsTwelve industrial PWM valves were investigated to manipulate high-pressure agricultural hollow-cone nozzles.Modulation frequencies ranged between 5 and 50 Hz and duty cycles between 10% and 100%.Upstream and downstream pressure profiles were used to determine maximum duty cycle ranges.Two out of 12 PWM valves could be potentially used for future variable-rate orchard sprayer designs.Abstract. Integration of high-speed pulse-width-modulation (PWM) solenoid valves into variable-rate orchard sprayers is needed to accurately regulate spray outputs for matching changes in plant canopy structure characteristics. Capability of 12 PWM valves to modulate hollow-cone nozzles for variable-rate applications was investigated with PWM frequencies of 5 to 50 Hz and duty cycles of 10% to 100%. The PWM valves were assembled on a laboratory spray system with a hollow-cone disc-core nozzle of 2.84 L min-1 flow capacity operated at 1380 kPa pressure. The upstream and downstream pressures on the PWM valves were recorded and analyzed to determine the maximum functional duty cycle ranges and maximum PWM frequency at which the PWM valves could manipulate the nozzle functionally. Test results showed that there were noticeable differences in the modulation capability among the 12 PWM valves due to their design differences. Two out of 12 valves were able to manipulate the hollow-cone nozzles with duty cycles ranging from 30% or 40% to 70% at the modulation frequency of 40 Hz. These two PWM valves performed the highest capability among the 12 valves to manipulate the hollow-cone nozzle. As a result, these two valves would be selected for future investigations on their flow rate modulation accuracy and droplet size distributions before they could be recommended for adaptation in the variable-rate orchard sprayers. Keywords: Duty cycle, Flow control, Orchard sprayer, Pesticide, Precision farming, Pulse width modulation.

A Hybrid Pulse Frequency Modulation Control Strategy for L-LLC Resonant Converter

The traditional control strategy for the L-LLC resonant converter is the synchronous unequal width pulse frequency modulation (SUW PFM). However, this strategy causes a large circulating power in the forward buck and reverse boost modes, especially when the voltage gain deviates from 1. To solve the limitations of the SUW PFM, a novel constant width PFM (CW PFM) is proposed in this article, which can reduce the circulating power and improve the converter efficiency in the forward buck and reverse boost modes. Furthermore, a hybrid PFM control strategy is proposed by merging the appropriate working conditions of the CW PFM and the SUW PFM, which can flexibly switch the two modulations depending on the gain and load conditions. Therefore, the L-LLC resonant converter has good soft-switching characteristics in entire load and gain ranges. Finally, a 7.5-kW L-LLC resonant converter prototype is built to verify the validity and superiority of the proposed control strategy.

Isolated Boost Type Resonant Converter With Fixed Frequency PWM and Load-Independent Voltage Gain

This article proposes an isolated boost type resonant converter (IBTRC) with fixed frequency pulsewidth modulation (PWM), which has load-independent gain characteristics. Only one magnetic component and two active switches are used in the proposed IBTRC. Therefore, compared with the two-stage converter and the current-fed resonant converter (CFRC), the number of magnetic components and switches of the proposed IBTRC is reduced. Moreover, with the proposed modulation, the converter obtains the benefits of load-independent voltage gain characteristics. Under wide load and voltage range, all switches can realize zero-voltage switching (ZVS) and all diodes can realize zero-current switching (ZCS). The operation mode, characteristics, and parameters design process of the proposed solution are also described in detail. Finally, a 600-W prototype is built to verify the validity and the advantages of the proposed scheme.

An Integrated Circuit Based, Single-Inductor-Dual-Output Buck LED Driver for Dimmable and Color Temperature Tunable Indoor Lighting Application

Tunability of correlated color temperature (CCT) and dimmability are the two major sought after features of functional solid-state lighting. This paper presents a low-cost, efficient, single-inductor-dual-output buck driver that facilitates CCT-control and dimming of a light emitting diode (LED) module composed of cool-white and warm-white chips. The proposed driver is designed based on two familiar integrated circuits (ICs), namely LM2596 and NE556. LM2596 serves as the main switching regulator and amplitude modulation (AM) controller whereas NE556 serves as the constant-frequency, dual-output pulse-width-modulation (PWM) controller. The exponential model of LED is exploited for improved estimation of the design parameters of the LED module and the driver circuit. The developed driver prototype is tested for its electrical, photometric, and colorimetric performances. The driver offers a full-load efficiency of about 90% for a 12-W test LED module. Under different operating modes, the LED system can produce warm, cool, or neutral white light and at the same time, the produced illuminance can be varied over a wide range. Moreover, the light flicker is imperceptible since the PWM frequency is set according to IEEE-1789 guideline.

A DC Arc Fault Detection Method Based on AR Model for Photovoltaic Systems

DC arc faults are dangerous to photovoltaic (PV) systems and can cause serious electric fire hazards and property damage. Because the PV inverter works in a high−frequency pulse width modulation (PWM) control mode, the arc fault detection is prone to nuisance tripping due to PV inverter noises. An arc fault detection method based on the autoregressive (AR) model is proposed. A test platform collects the database of this research according to the UL1699B standard, in which three different types of PV inverters are taken into consideration to make it more generalized. The arc current can be considered a nonstationary random signal while the noise of the PV inverter is not. According to the difference in randomness features between an arc and the noise, a detection method based on the AR model is proposed. The Burg algorithm is used to determine model coefficients, while the Akaike Information Criterion (AIC) is applied to explore the best order of the proposed model. The correlation coefficient difference of the model coefficients plays a role as a criterion to identify if there is an arc fault. Moreover, a prototype circuit based on the TMS320F28033 MCU is built for algorithm verification. Test results show that the proposed algorithm can identify an arc fault without a false positive under different PV inverter conditions. The fault clearing time is between 60 ms to 80 ms, which can meet the requirement of 200 ms specified by the standard.

A Three-Level RF-PWM Method Based on Phase-Shift Control and MPWM for ADTx

A radio frequency pulse width modulation (RF-PWM) scheme based on phase-shift control and mapping PWM (MPWM) is described. Pulse coding is the key to improving the coding efficiency, flexibility, and configurability of the all-digital transmitter (ADTx). To solve the problem that the real-time performance of the system is limited by the time resolution, the phase-shift control principle is adopted to constrain the output pulse state. It decomposes the original signal into two phase-modulated constant envelope signals, and directly converts the two-level pulse waveform by MPWM. Finally, the fast generation of the three-level digital RF modulated signal is completed by vector synthesis. In this way, the rear power amplifier can be directly driven, and the difficulty of physical implementation is greatly reduced. Different from the traditional mapping strategy of traversal search, the proposed scheme does not require complicated error calculation and comparison. Simulation and offline experiments show that the proposed scheme has better comprehensive performance than other mapping schemes. For 16QAM modulated signals at a 300 MHz carrier, the proposed scheme can achieve nearly 70% coding efficiency (CE), less than −50 dBc, and 1% adjacent channel power ratio (ACPR) and error vector magnitude (EVM).