Improved Pulse Width Modulation Research Articles

A new modulation for three‐phase current source converter

AbstractThis brief proposes an improved pulse width modulation (PWM) scheme, which uses diode voltage clamping characteristics to achieve the direct control of three‐phase current source converter without any logical transformation. Compared with the traditional indirect carrier modulation scheme—mapping‐PWM, the proposed scheme can solve the disadvantages of low DC current utilization, high switching loss, and complex control process. The generation mechanism of IPWM is analyzed in this brief. Then, based on the generation mechanism, the output characteristics of the system under IPWM are analyzed and compared with the traditional modulation scheme. Finally, the experimental results verify the effectiveness the proposed modulation scheme.

NÂNG CAO CHẤT LƯỢNG ĐIỆN ÁP RA NGHỊCH LƯU CẦU H NHỜ GIẢM TỔNG LƯỢNG SÓNG HÀI BẰNG CÁCH THAY ĐỔI THỜI GIAN PHÂN BỐ TRẠNG THÁI ĐIỆN ÁP 0 VÀ KHÁC 0

This article proposes a plan to improve the quality of the output AC voltage of the H-bridge inverter based on the change of the law of distribution of zero and non-zero voltage states of the inverter when controlling the H-bridge inverter. The results were surveyed, analyzed, compared, and evaluated by simulation model on Matlab-Simulink software. In which the fundamental harmonic level index and the total harmonic distortion (THD) are used to compare, analyze and evaluate the quality of H-bridge inverter output voltages in different switching modes such as pulse width modulation according to sine law (sinPWM), pulse width adjustment (SIR) and the proposed improved pulse width modulation law. The results show that the H-bridge inverter output voltage form with improved sequential switching law gives better quality than the original. This result has practical significance in the research and design of power conversion circuits for AC power transmission systems.

Enhancing grid‐connected solar PV systems with a novel three‐phase hybrid multilevel inverter

SummaryThis paper presents a novel three‐phase hybrid multilevel inverter (TPHMLI) designed for grid‐connected solar photovoltaic (SPV) systems. The TPHMLI combines series‐connected bridge topologies of half and full circuits to generate 11 stages of line load voltages, reducing the need for DC sources. It also introduces an improved pulse width modulation (PWM) approach, addressing computational challenges and high‐frequency triggering issues. Practical validation in a laboratory setting demonstrates the MLI's functionality and effectiveness. Furthermore, the advanced MLI topology successfully addresses design issues in grid‐integrated SPV structures, including power quality, efficiency, and reliability. It excels in managing reactive power and fault obstructive capabilities. Extensive simulations using MATLAB/Simulink confirm its superior performance, making it a promising solution for power conditioning units in grid‐connected solar PV systems. This research contributes to clean and sustainable energy conversion technologies, enhancing power quality and cost‐effectiveness, with significant potential for practical applications in the renewable energy sector.

An Improved PWM Method of Five-Leg VSI Fed Dual-PMSM System With Duty Cycles Regulation

The five-leg voltage source inverter dual motors system has been widely studied in recent years for its advantage of fewer power switching devices. The traditional modulation method generates the voltage vectors needed by the two motors alternately in one control period, in which active voltage vectors of one motor can operate for a short time thus limit the speed ranges of the two motors. Regarding the deficiency, the relationship between the basic active voltage vectors of the two motors is futher analyzed and an improved pulsewidth modulation (PWM) method is proposed in this article, by which the duty cycles of five-phase PWM signals are modified as a whole. Under the premise that the common leg pulse width meets the requirements of the two motors in one control period, the effective time of the active voltage vectors of the two motors is tremendously expanded with no hardware added, and the speed ranges of the two motors are thus greatly expanded. When one motor runs at a relatively low speed, the speed range of the other motor can be effectively expanded with this method, compared with the traditional one. Simulations and experiments also verify the accuracy of the theoretical analysis and the feasibility of the proposed method.

A Novel Predictive Torque Controller for Switched Reluctance Motor Drives

AbstractThis paper proposes a novel deadbeat predictive torque control (DPTC) scheme to minimize the torque ripple of switched reluctance motor (SRM) drives. The proposed DPTC consists of torque inverse model and flux‐linkage controller. The torque inverse model is used to realize the nonlinear mapping from the desired torque to the flux‐linkage. On this basis, the flux‐linkage controller predicts the required voltage for a given reference torque at each digital time step. Besides, an improved pulse width modulation (PWM) control is developed to offset the losses caused by power converter and winding resistance. And the digital delay in the actual implementation of the proposed DPTC algorithm is compensated through the estimation + prediction technology. Both simulation and experimental testing are carried out to verify the effectiveness of the proposed control scheme. The results show that the proposed DPTC method has better torque ripple suppression performance than the conventional direct torque control (DTC) scheme. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Improved Modulation Strategy for Singe-Phase Cascaded H-Bridge Multilevel Inverter

In this letter, two new improved pulsewidth modulation (PWM) techniques are proposed for single-phase cascaded H-bridge inverter. Compared with the conventional modulation methods, including phase-shifted PWM (PS-PWM), level-shifted PWM (LS-PWM), discontinuous modulation (D-PWM), only PS-PWM can ensure the output quality and maintain the power balance between each module. That is why it is widely used. However, the switch with PS-PWM always operates in a high-frequency mode, resulting in the high switching losses and low efficiency. In order to solve the problem, two improved cascaded H-bridge multilevel PWM methods are proposed in this letter. With the proposed PWM methods, the power can be evenly distributed among modules, the utilization rate of switching devices is the same, while the switching times are reduced, which improves the system efficiency. Finally, the experimental tests are carried out on a digital-control single-phase cascaded H-bridge seven-level inverter. And the experimental results verify the effectiveness of the proposed solution.

Improved Capacitor Voltage Balancing Algorithm for a Single-phase T-type Inverter

The paper proposes an improved pulse width modulation algorithm to solve the voltage imbalance on DC capacitors for single-phase T-type inverter. By changing the modulation index, the residual states can be applied to the discharge/charge state on the DC capacitors to balance the voltage. The proposed algorithm is validated for application in single-phase T-type inverters in independent mode. The simulation and experimental results have confirmed the effectiveness of the improved pulse width modulation method for single-phase T-type inverter. The paper proposes an improved pulse width modulation algorithm to solve the voltage imbalance on DC capacitors for single-phase T-type inverter. By changing the modulation index, the residual states can be applied to the discharge/charge state on the DC capacitors to balance the voltage. The proposed algorithm is validated for application in single-phase T-type inverters in independent mode. The simulation and experimental results have confirmed the effectiveness of the improved pulse width modulation method for single-phase T-type inverter.

PWM Strategy for MW-Scale “SiC+Si” ANPC Converter in Aircraft Propulsion Applications

In this article, an improved pulsewidth modulation (PWM) strategy is introduced for three-level active neutral point clamped converters based on a hybrid configuration of silicon carbide (SiC) mosfets and silicon (Si) insulated gate bipolar transistor (IGBTs). Compared with the conventional PWM strategies in the literature, this proposed PWM strategy enables the SiC switches only to interface with small commutation loops, thus the turn-off voltage overshoots caused by the parasitic loop inductance and high <b xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">di</b> / <b xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dt</b> are much lower. Soft switching is achieved across all the IGBTs, and the switching losses of the converter only dissipate from the SiC mosfets, leading to high efficiency of the converter. Also, with this improved PWM strategy, the conduction loss at zero voltage output of this converter is reduced due to the turn-on of two parallel conduction paths. Furthermore, this proposed PWM strategy can protect the body diodes of the SiC mosfets from conducting large load current. All these advantages with the proposed PWM strategy are experimentally verified in a megawatt-scale three-phase three-level “SiC+Si” hybrid active neutral point clamped inverter developed for electric aircraft propulsion applications.

Characterization and Modeling of Soft Magnetic Materials for Improved Estimation of PWM-Induced Iron Loss

This article investigates the iron loss properties of soft magnetic materials under conditions of high excitation frequency and varying premagnetized dc-bias fields (i.e., different magnetization states). Using measured iron loss data collected from the customized test equipment, a modified dynamic Jiles–Atherton model has been developed specifically for the purpose of achieving improved pulsewidth modulation (PWM)-induced iron loss estimation. The accuracy and scalability of the proposed prediction model for different conditions are evaluated including the flux ripple amplitude, excitation frequency, dc-bias field, and symmetry of the triangular waveform. Experimental results have confirmed that the proposed model can accurately predict the dynamic hysteresis loop and corresponding iron loss over a wide range of operating conditions. By introducing a companion iron loss model developed for fundamental and low-order harmonic fields, the total iron loss under inverter PWM voltage excitation is explored. The results show that model parameters derived from a limited number of tests can be used to predict the iron loss in a much broader operating range, which makes it a promising tool for PWM-induced iron loss estimation in new machine designs intended for demanding operating conditions.

SiC‐based active quasi‐Z‐source inverter with improved PWM control strategy

In this study, an improved pulse width modulation (PWM) scheme was proposed for an active quasi-Z source inverter (AqZSI). Compared to the quasi-Z-source inverter (qZSI), the AqZSI with improved PWM strategy can operate in a wide range of input voltage with higher efficiency. Furthermore, the AqZSI can operate with a higher modulation index, a lower inductor current stress, and a reduced shoot-through current. A procedure flowchart is presented for the optimal selection of the shoot-through duty cycle, the switching ratio of the additional switch, and the modulation index for AqZSI. Moreover, some comparative results between the AqZSI, qZSI and conventional two-stage inverter with a boost DC–DC converter are shown in detail. Finally, 1.2 kVA SiC-based three-phase inverter prototypes are built to verify the agreement between theory and measurement.

An Improved Modulation Strategy for Fast Capacitor Voltage Balancing of Three-Level NPC Inverters

This paper presents an improved pulsewidth modulation strategy in conjunction with an optimal compensator for fast capacitor voltage balancing in three-level neutral-point-clamped (NPC) inverter. The voltage balancing compensator is designed in such a way that it produces optimal unbalance compensation coefficient according to the inherent limitations related to the variability range of modulating signals. It generates maximum compensating neutral current for the full modulation depth extending into overmodulation region and throughout the entire range of load power factor angles, and thus improves the unbalance compensation ability for all the operating conditions of the inverter. The optimal compensation offset signal corresponding to each operating point is determined from the boundary limit of the auxiliary modulating signals. Particle swarm optimization is applied for such purpose. The performance of the proposed optimal compensator for different combinations of modulation index and load power factors are evaluated through extensive simulation study using Matlab/Simulink and validated in experimentation using a three-level NPC inverter prototype with induction motor load. Finally, the voltage balancing performances of the proposed compensator are compared with that available in literature to confirm the usefulness of the proposed concept.

Experimental Verification of Three phase quasi Switched Boost Inverter with an Improved PWM Control

&lt;p&gt;In this paper, an experimental investigation of a three phase quasi Switched Boost Inverter (qSBI) topology is proposed and analysed with an improved Pulse Width Modulation strategy. The qSBI is capable of providing both boost and inversion actions in a single stage. The improved PWM control technique can provide a higher boost with the reduced duty ratio. The theoretical analysis presented in this work is validated using an experimental set up of 100W qSBI topology and hardware results are shown for verification. The improved PWM strategy is implemented and firing pulses are generated in FPGA SPARTAN 3E kit. With the duty ratio of 0.05, the peak ac load voltage of 80 V is obtained. The performance of three phase qSBI is analysed with both conventional PWM strategy and improved PWM strategy. The observations are presentated in detail.&lt;/p&gt;

Experimental Investigations on Single-Phase Shunt APF to Mitigate Current Harmonics and Switching Frequency Problems Under Distorted Supply Voltage

ABSTRACT This paper presents an experimental validation of, phase-lock loop less modified control strategy for single-phase shunt active power filter (APF) to compensate current harmonics and reactive power in single-phase distribution system under distorted supply voltage. The control technique is divided into two parts: first associated with selected frequency signal extraction by using Hilbert transform-based adaptive tuned filter from distorted supply voltage followed by reference current signal generation using DC-link energy balance method. Second deals with an improved pulse width modulation technique which reduces switching ripple and switching frequency for voltage source inverter used as a shunt APF. The overall control scheme is simulated using MATLAB/Simulink environment in the steady state and transient condition of the load. A detailed hardware design and other parameters of proposed system have been presented. A laboratory prototype has been developed using dSPACE DS1104 controller card having TMS320F240 as a slave DSP to verify the simulation results. Simulated and experimental results show that the proposed control technique gives a flexible and fast dynamic response in single-phase distribution system. The harmonic spectral performance of the proposed technique is as per the recommendation of IEEE-519 standards.

An Improved PWM Strategy for Z-Source Inverter With Maximum Boost Capability and Minimum Switching Frequency

Z-source inverter provides a competitive single-stage dc–ac power conversion with the capability of both buck and boost voltage regulation. In order to maximize voltage gain and to increase efficiency, this paper proposes an improved pulse-width modulation (PWM) strategy. By adjusting the shoot-through duty ratio of one-phase leg, it regulates the average value of intermediate dc-link voltage, which is the same as the instantaneous maximum of three-phase line voltage in one switching time period $(T_{s})$ . And the other two-phase legs maintain the fixed switching states. Thus, the equivalent switching frequency of power devices in the inverter bridge is reduced to $1/ 3f_{s}$ ( $f_{s}$ is the frequency corresponding to $T_{s}$ ). The operating principles and closed-loop controller design are analyzed and verified by simulation and experiments. Compared with the existing PWM strategies, the improved PWM (IPWM) strategy demonstrates higher efficiency under full operation range of low voltage gain (1.27-2) application. However, with the IPWM strategy, the inductor current and capacitor voltage contain six-time-line-frequency ripples, which consequently require large size of the passive components when the output frequency is very low. Thus, it is also suitable for 400–800-Hz medium frequency aircraft and vessel power supply system due to a relatively high output line frequency. Furthermore, the idea of IPWM strategy can be extended to other kinds of three-phase impedance network-based inverters.

An Improved Pulse Width Modulation Method for Chopper-Cell-Based Modular Multilevel Converters

In this paper, an improved pulse width modulation (PWM) method for chopper-cell (or half-bridge)based modular multilevel converters (MMCs) is proposed. This method can generate an output voltage with maximally 2N+1 (where N is the number of submodules in the upper or lower arm of MMC) levels, which is as great as that of the carrier-phase-shifted PWM (CPSPWM) method. However, no phase-shifted carrier is needed. Compared with the existing submodule unified pulse width modulated (SUPWM) method, the level number of the output voltage is almost doubled and the height of the step in the staircase voltage is reduced by 50%. Meanwhile, the equivalent switching frequency in the output voltage is twice that of the conventional SUPWM method. All these features lead to much reduced harmonic content in the output voltage. What is more, the voltages of the submodule capacitors can be well balanced without any close-loop voltage balancing controllers which are mandatory in the CPSPWM schemes. Simulation and experimental results on a MMC-based inverter show validity of the proposed method.

A High-Efficiency Dimmable LED Driver for Low-Power Lighting Applications

This paper presents a dimmable light-emitting diode (LED) driver with adaptive feedback control for low-power lighting applications. An improved pulsewidth modulation dimming technique is studied for regulating the LED current and brightness. Under universal input voltage operation, high efficiency and high power factor can be achieved by a coupled inductor single-ended primary inductance converter power factor correction (PFC) converter with a simple commercial transition-mode PFC controller. The operation principles and design considerations of the studied LED driver are analyzed and discussed. A laboratory prototype is also designed and tested to verify the feasibility.