Proposed Pulse Width Modulation Research Articles

Pulse Width Modulation Methods for Minimizing Commutation Torque Ripples in Low Inductance Brushless DC Motor Drives

This paper proposes pulse width modulation (PWM) methods for low inductance brushless DC (BLDC) motor drives that minimize the commutation torque ripples. An uneven current of non-commutation phase generates the commutation torque ripples. In the low inductance BLDC motor drives, two types of time delays in PWM also induce critical torque ripples. In this paper, the analyses of the time delays in PWM and their effects are introduced. Then, two PWM methods are proposed to eliminate the time delays in the commutation region and the conduction region, respectively. The commutation period is controlled to be synchronized to the switching period. In addition, the proposed methods synchronize the switching period to the commutation interrupt. As a result, the proposed methods effectively maintain the minimum commutation period as well as minimize the commutation torque ripples in the low inductance BLDC motor drives. The validity of the proposed methods is demonstrated by the simulation and experimental results in various driving conditions. The results show that the commutation period is remarkably shortened and the commutation torque ripples are reduced by 27.6% in comparison to the conventional method.

Optimal PWM in Three-Level Inverter for THD Minimization with Quarter Wave Symmetry Relaxed

Background: Previous works on total harmonic distortion (THD) minimization for multilevel inverters (MLI’s) has made a symmetrical approach that imposes Quarter Wave Symmetry (QWS) and Half Wave Symmetry (HWS) with the aim to restrict the computational difficulties to solve the finalized non-linear expressions. Objective: However, QWS constraint can be abolished, which leads to more generalized formulations and multiple solutions corresponding to minimum THD for complete modulation index-range. Methods: A systematic search approach using MATLAB in-build function is adopted to investigate ideal angles of switching related to three-level, three-phase inverter restricted to only HWS as a constraint for two and three (i.e., N= 2 and 3) switching transitions per quarter cycle. Results: On account of the effective minimization of the dominant low-order odd line voltage harmonics, the proposed pulse-width-modulation (PWM) scheme proved its superiority based on minimum THD% performance compared to the previously reported PWM techniques with both HWS and QWS being retained. Conclusion: The simulation, as well as experimental results to confirm the efficacy of the proposed non-symmetrical PWM scheme over the traditional PWM method restricted to QWS and HWS symmetries over the entire modulation-index range with added advantage of general formulation and multiple solutions.

Pulse Width Modulation Switching Schemes for Two-Level Five-Phase Voltage Source Inverter

This paper proposes pulse width modulation schemes for a two-level five-phase voltage source inverter. According to the literature, the generation of a pure sinusoidal waveform requires an (n-1) number of vectors for 'n' number of phases, so in a five-phase system, a minimum of four-vectors is needed to generate a sinusoidal waveform. The author uses only two large vectors in this paper for a five-phase voltage source inverter. Vector diagram, switching table, and switching waveform have presented for two adjacent large space vectors. The performance for each PWM scheme is analyze based on fundamental components and total harmonic distortion. In last, results have verified in the Simulink environment.

Space vector modulation with reduced common mode voltage for six-phase drives

Purpose This paper aims to present a modified space vector pulse width modulation (SVPWM) technique for six-phase induction motor drive based on common-mode voltage (CMV) and current losses which are two important issues affecting drive system behavior and quality. Design/methodology/approach It is shown that the presence of z-component currents and the presence of CMV in six-phase drive system are two major limiting factors in space vector selection. The behavior of several space vector selections in a two-level inverter considering minimum CMV and z-components is investigated. Then, the space vectors in a three-level inverter is analyzed and tried to explore an SVM technique with better behavior. Findings The analyses show that all the problems cannot be solved in a six-phase drive system with two-level inverter despite having 64 space vectors; this study tried to overcome the limitations by exploring space vectors in a three-level inverter. Originality/value The proposed pulse width modulation (PWM) strategy leads to minimum current distortion and undesired current components with zero CMV and modest torque ripple.

A Temporary Overvoltages Mitigation Strategy for Grid-Connected Photovoltaic Systems Based on Current-Source Inverters

Temporary overvoltages (TOVs) typically caused by short-circuit faults and switching events can impose considerable damage on power system equipment. Furthermore, the penetration of distributed generations into the utility grids may intensify the problem arising from the TOVs. Despite recent research advancements, the TOV problems with current-source inverter (CSI)-based photovoltaic (PV) systems have not been investigated comprehensively. This paper proposes a combination of virtual impedance and modified switching strategy for grid-connected CSI-based PV systems. The virtual impedance-based control damps current and voltage oscillations. On the other hand, the proposed pulse width modulation strategy restricts power injection during the fault conditions. Simulation results confirm that the proposed approach effectively mitigates the TOV without controller mode switching between the standard and fault conditions.

Fuzzy logic-based multi-level shunt active power filter for harmonic reduction

In this paper, using a three level diode clamped multilevel inverter and DC capacitor, a shunt active power filter (SAPF) is implemented to mitigate the supply current harmonics and compensate reactive power drawn from nonlinear load. The advantage of using three-level inverter paves way to reduced harmonic distortion and switching losses. Fuzzy logic control and unit sine vector control are proposed in this paper for generating reference current for the SAPF. The advantage of fuzzy control is that it is based on a linguistic description and does not require a mathematical model of the system. The implementation of fuzzy logic control (FLC) algorithm is executed using MATLAB fuzzy logic tool box. The proposed pulse width modulation (PWM) method produces the switching signals to the inverter from the sampled reference phase voltage magnitudes as in the case of conventional space vector PWM (SVPWM). The simulation results illustrate that the proposed three-level SAPF with low harmonic content in supply current and in phase with the line voltage. The simulation results are validated with prototype model for demonstrating the effectiveness of the system.

Fuzzy logic-based multi-level shunt active power filter for harmonic reduction

In this paper, using a three level diode clamped multilevel inverter and DC capacitor, a shunt active power filter (SAPF) is implemented to mitigate the supply current harmonics and compensate reactive power drawn from nonlinear load. The advantage of using three-level inverter paves way to reduced harmonic distortion and switching losses. Fuzzy logic control and unit sine vector control are proposed in this paper for generating reference current for the SAPF. The advantage of fuzzy control is that it is based on a linguistic description and does not require a mathematical model of the system. The implementation of fuzzy logic control (FLC) algorithm is executed using MATLAB fuzzy logic tool box. The proposed pulse width modulation (PWM) method produces the switching signals to the inverter from the sampled reference phase voltage magnitudes as in the case of conventional space vector PWM (SVPWM). The simulation results illustrate that the proposed three-level SAPF with low harmonic content in supply current and in phase with the line voltage. The simulation results are validated with prototype model for demonstrating the effectiveness of the system.

Carrier-Based Discontinuous PWM Method for Five-Leg Inverter

This paper proposes a rotation carrier-based discontinuous pulse width modulation (CB-DPWM) method for the five-leg inverter (FLI). The FLI based on two-level topology consists of 10 switching devices for driving dual motors. Therefore, two switching devices can be reduced to compare the configuration using two three-leg inverters for driving dual motors. The proposed pulse width modulation (PWM) method is based on the reference signals which are used in existing carrier-based continuous pulse width modulation (CB-CPWM) method for FLI. In the proposed rotation CB-DPWM method, one of five-leg is periodically clamped to V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dc</sub> /2 or - V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dc</sub> /2 by adding the offset voltage to the reference voltages of the existing CB-CPWM method. The five reference voltages for all legs are considered to calculate the offset voltage of the proposed rotation CB-DPWM method. Consequently, since the proposed rotation CB-DPWM method has less switching than the existing CB-CPWM, the switching loss can be reduced and it results in the efficiency improvement. Simulation and experimental results confirm the effectiveness and feasibility of the proposed method.

An Adaptive Voltage Scaling Buck Converter with Preset Circuit

An Adaptive voltage scaling (AVS) buck converter with Preset circuit (P-AVS), which can adaptively scale the output voltage fast, is presented. The voltage scaling loop in the proposed Pulse width modulation (PWM) buck with P-AVS is divided into coarse scaling loop and fine scaling loop, which can regulate the reference voltage adaptively according to load status. The coarse scaling loop can set quickly a coarse value of reference voltage according to the operation frequency of the load by a preset block, and the fine scaling loop is designed to scale voltage finely. The proposed P-AVS buck converter, with 3.3V input and 2MHz switching frequency, is fabricated in a 0.13mm standard CMOS process. The output voltage and the frequency of the load are designed from 0.7V to 1.5V and 30MHz to 120MHz respectively. Compared with a typical AVS buck, the proposed P-AVS converter can save 17ms scaling up from 0.7V to 1.1V.

Self generating square/triangular wave and pulse width modulator using a single MO-CCCDTA

A self-generating square/triangular wave and pulse width modulator (PWM) using multiple output current controlled current differencing transconductance amplifier (MO-CCCDTA) is presented. To obtain all the three functions simultaneously from the same topology, the MO-CCCDTA is modified a little bit. The characterisation of the modified MO-CCCDTA structure shows that the parasitic resistances at input terminals (n and p) can be varied via bias current. The maximum useful frequency range is found to be 635 MHz, which is higher than the available literature. The waveform generator and PWM circuit use only one MO-CCCDTA, one grounded capacitor and no resistor; hence suitable for IC implementation. The duty cycle of proposed pulse width modulation can be tuned by bias current of MO-CCCDTA over a wide range. The performances of the proposed block and its applications (square/triangular/PWM) are verified by PSPICE simulation using TSMC 0.35 µm technology. The power consumption is about 1.12 mW. To verify experimentally, a prototype of MO-CCCDTA has been made using commercially available ICs (AD844AN and CA3080) on printed circuit board. The simulation and experimental results verify theoretical proposition well. Monte carlo simulation is carried out, which proves satisfactory performance of the proposed circuit against mismatches. The performance of the proposed circuit is also verified through pre-layout and post-layout simulation results. The required chip area is only 22.415 × 14.6 µm2.

Single-Phase Inverter With Energy Buffer and DC–DC Conversion Circuits

This paper proposes a new single-phase inverter topology and describes the control method for the proposed inverter. The inverter consists of an energy buffer circuit, a dc–dc conversion circuit and an H-bridge circuit. The energy buffer circuit and H-bridge circuit enable the proposed inverter to output a multilevel voltage according to the proposed pulse width modulation (PWM) technique. The dc–dc conversion circuit can charge the buffer capacitor continuously because the dc–dc conversion control cooperates with the PWM. Simulation results confirm that the proposed inverter can reduce the voltage harmonics in the output and the dc–dc conversion current in comparison to a conventional inverter consisting of a dc–dc conversion circuit and H-bridge circuit. Experiments demonstrate that the proposed inverter can output currents of low total harmonic distortion and have higher efficiency than the conventional inverter. In addition, it is confirmed that these features of the proposed inverter contribute to the suppression of the circuit volume in spite of the increase in the number of devices in the circuit.

Maximum Boost Control Method for Single-Phase Quasi-Switched-Boost and Quasi-Z-Source Inverters

The maximum boost control method for a single-phase switched-boost inverter (SBI) and single-phase Z-source inverter (ZSI) is proposed in this paper. In the proposed method, the low frequency voltage is added to the constant voltage for generating the variable shoot-through time intervals. For improving the AC output quality of the inverter, an active power switch is used to replace one of the diodes in the single-phase SBI. The operating principles and circuit analysis using the proposed maximum boost control method for single-phase inverters are presented. Laboratory prototypes are built to verify the operation of the proposed pulse-width modulation (PWM) control method for both single-phase quasi-ZSI and single-phase quasi-SBI.

Input‐series‐output‐parallel connected modular high frequency isolated AC–AC converters with positive compensation of inner‐current loop

A control strategy for input-series-output-parallel (ISOP) connected modular high frequency isolated AC–AC converter is proposed in this study. The circulating currents among all the constituent modules are avoided by the proposed pulse width modulation sequence generation method. Based on the revealed relationship between input voltage sharing (IVS) and output current sharing (OCS), a stable control strategy is proposed by using an output voltage loop and positive inner-current compensation loops. The individual input voltage sharing loops are eliminated. With the proposed control strategy, OCS or IVS can be achieved well for ISOP modular AC–AC converters under both steady and dynamic state, even in the case when the parameters of individual modules are mismatched. Simulation and experimental results are presented to verify the effectiveness of the control strategy.

Pulse width modulation for multi-agent systems

This paper studies the consensus problem for multi-agent systems. A distributed consensus algorithm is developed by constructing homogeneous pulse width modulators for agents in the network. In particular, a certain percentage of the sampling period named duty cycle is modulated according to some state difference with respect to the neighbors at each sampling instant. During each duty cycle, the amplitude of the pulse is fixed. The proposed pulse width modulation scheme enables all agents to sample asynchronously with arbitrarily large sampling periods. It provides an alternative digital implementation strategy for multi-agent systems. We show that consensus is achieved asymptotically under the proposed scheme. The results are compared with the self-triggered ternary controller.

A Novel Soft Switched Cycloinverter

A novel soft switched insulated-gate bipolar transistor (IGBT)-based cycloinverter, which is capable of converting voltage at the main frequency to voltage at high frequency, is proposed to improve the previously proposed pulse width modulation cycloinverter. An auxiliary switch, along with an inductor, is used to have simultaneous zero-current switching and zero-voltage switching for turn-on transitions of the IGBT in order to mitigate the internal losses and total harmonic distortion factor in the inverter. The principle of operation and design consideration are presented. The proposed cycloinverter is compared with a conventional hard switched cycloinverter, and it has been demonstrated that the losses have been reduced approximately 50% by this new switching technique and the efficiency of the inverter is increased significantly. A prototype of the cycloinverter is developed in the laboratory for verification of the simulation results. Experimental results are found in good agreement to the simulated results.

Fuzzy PWM based on Genetic Algorithm for battery charging

This paper investigates the use of fuzzy logic control together with Genetic Algorithm (GA) to tune corresponding membership functions in a pulse width modulation voltage (PWM)-based converter for battery charging. For quick charging purposes, a current-charging mode is built on the charging battery series with small impedance resistance. Once the rechargeable battery voltage reaches the preset output voltage value during the current-charging mode, constant voltage-charging mode should take to do the battery charging. No matter what you use a voltage/current mode for battery charging, the PWM converter with tuning duty cycle is necessary to obtain various output voltages to charge battery. The proposed pulse width modulation (PWM) control strategy based on fuzzy logic systems is applied to charge batteries for buck converter. A simulation is proposed to illustrate the efficiency of the design proposed in this paper.

New Hybrid Pulsewidth Modulation Technique to Reduce Current Distortion and Extend Current Reconstruction Range for a Three-Phase Inverter Using Only DC-link Sensor

This paper proposes a new modulation technique that can reduce the current distortion and extend the current reconstruction range for a three-phase inverter using only dc-link sensor. The proposed pulsewidth modulation (PWM) technique is a hybrid method which consists of space vector modulation method and the PWM method without using null switching states. The former provides low current distortion; however, it is with narrower current reconstruction range. In contrast, the latter extends the current reconstruction range at the cost of higher current distortion. For the proposed method, in the measurable region of space vector modulation method, space vector modulation is used to reduce the current distortion. Moreover, as the modulation range is out of the measurable region, the PWM method without using null switching states is applied to extend the current reconstruction range. Furthermore, the current reconstruction limitation using only dc-link sensor is analyzed. The analysis shows that the reduction of PWM switching frequency and acquisition time can extend the current reconstruction range. Comparison of experimental results derived from a field-programmable gate array-based controlled inverter is included. It will be demonstrated that using the proposed hybrid PWM technique, the three-phase current signals of the inverter can be reconstructed even under very low modulation index range while providing low current harmonic distortion of inverter output.

Single-Phase AC–DC–AC Three-Level Three-Leg Converter

In this paper, a three-level three-leg ac-dc-ac converter for single-phase applications is investigated. The operating principles and control strategies for the topology are presented. It is shown that dc-link voltage balancing and its reduction are important objectives in the system design. The proposed pulsewidth modulation (PWM) strategy permits the dc-link capacitor voltage balance and also its reduction. The three-level converter is compared to the two-level converter in terms of rms switch currents, harmonic distortion, losses, and costs. Experimental and simulation results are presented to validate the theoretical studies.