Pulse Width Modulation Voltage Research Articles

Short-Circuit Fault Diagnosis for Three-Phase Inverters Based on Voltage-Space Patterns

This paper introduces a fault detection and isolation (FDI) method for faulty metal-oxide-semiconductor field-effect transistors in a three-phase pulsewidth-modulated (PWM) voltage source inverter. Short-circuit switch faults are the leading cause of failure in power converters. It is extremely vital to detect them in the early stages to prevent unwanted shutdown and catastrophic failures in motor drives and power generation systems. Against the common FDI methods for power electronic inverters that use phase currents and PWM gate control signals, the proposed method only uses the inverter output voltages. This method analyzes the PWM switching signals in a time-free domain that is called the voltage space. For a healthy inverter, the projection of the state transitions in the voltage space results in a cubic pattern. Each short-circuit switch fault uniquely changes the voltage-space pattern that allows isolating the faulty switch. The fault detection time is only within one PWM carrier period, which is significantly faster than current-based conventional methods. The FDI result does not depend on the load, the PWM switching frequency, and the feedback loop. This method can address the reliability problem of multilevel inverters in renewable electrical generation systems and can dramatically reduce the number of required sensors.

A Simple and Direct Dead-Time Effect Compensation Scheme in PWM-VSI

This paper presents the direct compensation of the switching interval error of the effective voltage vectors by the dead time of a pulsewidth modulation voltage source inverter (PWM-VSI). The output voltages of a three-phase PWM-VSI are distorted and have voltage errors from the dead time to avoid the shoot-through of inverter arms and the time delay of the gate drive. Voltage distortion increases the harmonics of the output voltages and decreases control performance. This paper presents a simple and direct compensation technique to solve this problem in a three-phase VSI. The practical switching output voltages are determined by the dc-link voltage, the switching signals of each phase, the dead time, the time delay, and the current polarities of each phase. For these reasons, output voltage errors are not constant. In order to analyze the dead-time effect in the actual switching voltages of each phase, the practical switching voltages in a sampling period of a space vector PWM (SVPWM) method are calculated according to the current polarity. In the calculation, the dead time, the time delay of devices, and the voltage drops on power devices are included to consider nonlinear voltage distortion. From these practical switching voltages during the switching intervals in a sampling period, the average output voltages of each phase can be derived, and the output voltage errors between the voltage commands and the average output voltages of each phase are obtained. The SVPWM switching intervals of each phase can be derived by the average output voltages that are calculated according to the current polarity and nonlinear voltage distortion to compensate for the output voltage errors. With the simple detection of the current polarity, the practical errors of the switching intervals of each phase can be compensated by the addition of the compensated switching time. Simulation and experimental results validating the proposed compensation method are presented in this paper.

Study on the Driving Circuit of Carbon Nanotube Field Emission Display Based on Luminance Control

Carbon nanotube field emission display (CNT-FED) is one of the most significant subjects due to its unique qualities and perfect performance. But there are still some problems in FED, for example, the modulation of each pixel unit of field emission display device is discrete, and the traditional voltage pulse-width modulation driving mode cannot solve luminance non-uniformity and non-linearity of FED. So a novel driving circuit based on cathode current source is proposed. The current driving circuit can be fabricated on Si substrate in advance, and then carbon nanotube is grown at room temperature, carbon nanotube and constant current source circuits are integrated on the same Si substrate. Current source circuit and cathode emission part are integrated together, which not only can solve the FED luminance problem, but also can meet FED thin design.

Shuffled frog leaping algorithm‐based static synchronous compensator for transient stability improvement of a grid‐connected wind farm

The shuffled frog leaping algorithm (SFLA) is presented, to optimally design multiple proportional-integral (PI) controllers of the static synchronous compensator (STATCOM) system with the purpose of improving the transient stability of a grid-connected wind farm. The control strategy of the STATCOM system depends on a sinusoidal pulse width modulation voltage source converter, which is controlled by the cascaded PI control scheme. The response surface methodology is used to establish a second-order fitted model of the transient voltage responses at the point of common coupling in terms of PI controllers' parameters. For realistic responses, a three-mass drive train model is used for the wind turbine generator system because of its great influence on the dynamic analyses. The SFLA code is built using MATLAB software. The effectiveness of optimised PI-controlled STATCOM by the SFLA is then compared to that optimised by genetic algorithms technique taking into consideration symmetrical and unsymmetrical fault conditions. The proposed control scheme is applied to a real grid-connected wind farm system at Hokkaido Island, Japan. The validity of the proposed system is verified by the simulation results, which are performed using PSCAD/EMTDC software environment. With the proposed SFLA-based STATCOM, the transient stability of a grid-connected wind farm can be enhanced.

Simulation and Implementation of Single Phase Boost – Buck Rectifier Using SPMC Topology with Reduced Input Current THD

Simulation of single phase buck boost rectifier with reduced input current THD using single phase matrix converter topology is describing in this paper. Due to the bidirectional feather the operation for buck-boost rectifier can be made through matrix converter topology. And this is possible by the proper switching algorithm to control the switches for their boost and buck operation. The input current nature is almost sinusoidal with low current total current harmonics and the level of THD is below than limit that was defined in the standards of IEEE. With the proper variation in modulation index corresponding changes in the output voltage is observed of buck-boost rectifier. For the synthesis of the output voltage Pulse width modulation (PWM) technique is used. The simulation results using MATLAB/Simulink are providing to validate the feasibility of this proposed method

Circulating current elimination scheme for parallel operation of common dc bus inverters

In this paper, a circulating current elimination scheme for common dc bus parallel inverter system is proposed. A dead-time elimination sinusoidal pulse width modulation (SPWM) is presented to overcome the circulating current caused by dead-time effects. The circulating current elimination scheme combines dead-time elimination SPWM and double loop control method, which is compose of an outer voltage loop and an inner current loop. Synchronizing the pulse width modulation (PWM) signals of each parallel unit, the instantaneous output PWM voltages of the parallel units can be kept the same, apart from the zero crossing of load current. The proposed scheme is easy to be implemented on the digital control board using digital signal processing (DSP) and field-programmable gate array (FPGA). Experimental results are depicted to demonstrate the validity and features of the proposed circulating current elimination scheme.

Wind-Solar-Storage Hybrid Micro grid Control Strategy Based on SVPWM Converter

Distributed generator (DG) is an increasing interest in using not only to inject power into the grid, but also to enhance the power quality. In this paper, a space voltage pulse width modulation (SVPWM) control method and current double closed loop control strategy is proposed for DG converter in a wind-solar-storage hybrid micro grid system. This method is based on the proper topology of three-phase voltage controller. Power fluctuation is existed in among wind system, photovoltaic (PV) system and both side of the storage unit system when the wind-solar-storage hybrid micro grid is disconnected to the grid because of troubleshooting or repairing of hybrid micro grid system, it can make a big shock, it also affects the normal work of the other DG and power quality of important load, and it even makes the whole system paralysis seriously. So, the topological structure of DG controller and control method are discussed in detail and simulation results are presented. The results demonstrate the effectiveness of the proposed method in the wind-solar-storage hybrid micro grid

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.

A Dual-loop Model Predictive Voltage Control/Sliding-mode Current Control for Voltage Source Inverter Operation in Smart Microgrids

The design of a robust controller for the voltage source inverter is essential for reliable operation of distributed energy resources in future smart microgrids. The design problem is challenging in the case of autonomous operation subsequent to an islanding situation. In this article, a dual-loop controller is proposed for voltage source inverter control. The outer loop is designed for microgrid voltage and frequency regulation based on the model predictive control strategy. This outer loop generates reference inverter currents for the inner loop. The inner loop is designed using a sliding-mode control strategy, and it generates the pulse-width modulation voltage commands to regulate the inverter currents. A standard space vector algorithm is used to realize the pulse-width modulation voltage commands. Performance evaluation of the proposed controller is carried out for different loading scenarios. It is shown that the proposed dual-loop controller provides the specified performance characteristics of an islanded microgrid with different loading conditions.

Robust Sensorless Sliding Mode Flux Observer for DTC-SVM-based Drive with Inverter Nonlinearity Compensation

This paper presents a robust and speed-sensorless stator flux estimation for induction motor direct torque control. The proposed observer is based on sliding mode approach. Stator electrical equations are used in the rotor orientation reference frame to eliminate the observer dependence on rotor speed. Lyapunov’s concept for systems stability is adopted to confine the observer gain. Furthermore, the sensitivity of the observer to parameter mismatch is recovered with an adaptation technique. The nonlinearities of the pulse width modulation voltage source inverter are estimated and compensated to enhance stability at low speeds. Therefore, a new method based on the model reference adaptive system is proposed. Simulation and experimental results are shown to verify the feasibility and effectiveness of the proposed algorithms.

Analysis and Modeling of Converter with PWM Output for Two-Phase Motor Applications

This paper presents a steady state analysis of two-phase voltage-source converters with pulse width modulation (PWM) and output voltage control for small two-phase motor drives. The mathematical models of the different converter connections are built on condition of assumption of idealized semiconductor devices. A complex Fourier series approach is used to predict to terminal voltage and current waveforms. DOI: http://dx.doi.org/10.5755/j01.eee.20.1.6160

Analysis and assessment of VSC excitation system for power system stability enhancement

The voltage source converter (VSC) excitation system is a novel excitation system based on pulse-width modulation (PWM) voltage source converter, which is proposed as improved alternatives to the conventional thyristor excitation systems. This paper aims to provide theoretical confirmation of power system stability enhancement by the VSC excitation system. The reactive current injected to generator terminals by the VSC excitation system can be controlled flexibly. Its capability of enhancing power system stability is investigated in this paper. The simplified model of VSC excitation system suitable for use in system stability studies is developed. An extended Philips–Heffron model of a single-machine infinite bus (SMIB) system with VSC excitation system is established and applied to analyze the damping torque contribution of the injected reactive current to the power system. This paper also gives a brief explanation on why the VSC excitation system can enhance the transient stability in light of equal area criterion. The results of calculations and simulations show that the injected reactive current of VSC excitation system contributes to system damping significantly and has a great effect on the transient stability. When compared with conventional thyristor excitation systems, the VSC excitation system can not only improve the small-signal performance of the power system, but also can improve the system transient stability limit.

Practical Implementation of an Improved Standby Boost Uninterruptible Power Supply

This paper proposes a single phase pulse-width modulated (PMW) voltage source uninterruptible power supply known as an improved standby boost uninterruptible power supply (ISBUPS) which centers on keeping the output voltage of the inverter system of the UPS at constant voltage of 220V AC and ripple free when utility power supply fails. This concept is achieved by incorporating proportional integral (PI) controller, boost converter and L-C filter at inverter control section. In this research, apart from stabilizing the inverter output voltage of inverter at 220VAC in standby mode, 0.96 modulation index is also realized. The total harmonic distortion of the system is reduced down to 5.05%. This proposed system has its applications at homes, offices and in business centers especially in Nigeria where electrical power instability is high now.

Dynamic Response of a Stand Alone DC Side Wind Energy Conversion System with Battery Energy Storage

The study concerns particularly the DC side of the wind system, the continuity of the AC one being already studied in [1]. Then, this work elaborates an analysis of the DC components, particularly the system conversion and storage of the wind system conversion. Indeed, the battery is a storage buffer essential in our case for isolated network. We emphasize its importance by evaluating its various features. The AC study concerned the analysis and simulation of a low speed Permanent Magnet Synchronous Generator (PMSG) driven by a vertical wind turbine through a Pulse-Width Modulation (PWM) voltage inverter.Renewable resources are in constant fluctuation. Therefore, in order to maximize the efficiency of the renewable energy system it is necessary to track the maximum power point of the input source. In this system, the maximizing is assured while considering the optimal power curve as load characteristic, with the knowledge of the turbine characteristic Cp (λ).The study was accomplished on MATLAB/Simulink and Script platforms.

Research of a self-tuning algorithm for industrial micro-grid power conversion

With more and more attention on the grid current harmonic in recent years, many control schemes of the Pulse Width Modulation Voltage Source Converter PWM-VSC have been investigated. Conventional PI controller has limitations in sensitivity subject to load and system parameter variation. Even the stability of the system can be threatened under a large and sudden load change. In this paper, the practical situation of a VSC for industrial Micro Grid MG is considered and an Artificial Neural Network ANN based control method is employed to solve the problem. Meanwhile, an online parameter tuning algorithm is introduced for its advantage of self-tuning and system character identification. The proposed control scheme is verified through simulation and prototype experiment. The experiment is performed to demonstrate the advantages of the proposed controller under different situations.

Adaptive Fuzzy Sliding Mode Controller for Grid Interface Ocean Wave Energy Conversion

This paper presents a closed-loop vector control structure based on adaptive Fuzzy Logic Sliding Mode Controller (FL-SMC) for a grid-connected Wave Energy Conversion System (WECS) driven Self-Excited Induction Generator (SEIG). The aim of the developed control method is to automatically tune and optimize the scaling factors and the membership functions of the Fuzzy Logic Controllers (FLC) using Multi-Objective Genetic Algorithms (MOGA) and Multi-Objective Particle Swarm Optimization (MOPSO). Two Pulse Width Modulated voltage source PWM converters with a carrier-based Sinusoidal PWM modulation for both Generator- and Grid-side converters have been connected back to back between the generator terminals and utility grid via common DC link. The indirect vector control scheme is implemented to maintain balance between generated power and power supplied to the grid and maintain the terminal voltage of the generator and the DC bus voltage constant for variable rotor speed and load. Simulation study has been carried out using the MATLAB/Simulink environment to verify the robustness of the power electronics converters and the effectiveness of proposed control method under steady state and transient conditions and also machine parameters mismatches. The proposed control scheme has improved the voltage regulation and the transient performance of the wave energy scheme over a wide range of operating conditions.

PD properties when varying the smoothness of synthesized waveforms

The increased use of power electronic components in power systems makes it important to understand how rapidly rising voltages affect insulation systems. One vital aspect of this challenge is the measurement of partial discharges, PDs, which are considered as being a sign of weakness and can affect the life of insulation considerably. In this paper an approach is presented to measure PDs in a dielectrically insulated cavity when exposed to pulse width modulated (PWM) voltage shapes with different degree of smoothness. This is a continuation of our earlier investigations on the different behavior of PDs where voltages characterized by different rise times were applied. The present investigation shows that the PD amplitude decreases significantly already at a moderate level of PWM voltage smoothness to a magnitude that is about the same as for sinusoidal voltage shape. For the phase resolved PD (PRPD) pattern to become similar to the normal AC pattern it is required that the remains from PWM steps are lower than the extinction voltage. This work elucidates how PDs are affected by synthesized waveforms and limits for a sufficient smoothing level are found, which is of importance when designing insulation systems exposed to fast transients.

Transient stability enhancement of wind farms connected to a multi-machine power system by using an adaptive ANN-controlled SMES

This paper presents a novel adaptive artificial neural network (ANN)-controlled superconducting magnetic energy storage (SMES) system to enhance the transient stability of wind farms connected to a multi-machine power system during network disturbances. The control strategy of SMES depends mainly on a sinusoidal pulse width modulation (PWM) voltage source converter (VSC) and an adaptive ANN-controlled DC–DC converter using insulated gate bipolar transistors (IGBTs). The effectiveness of the proposed adaptive ANN-controlled SMES is then compared with that of proportional-integral (PI)-controlled SMES optimized by response surface methodology and genetic algorithm (RSM–GA) considering both of symmetrical and unsymmetrical faults. For realistic responses, real wind speed data and two-mass drive train model of wind turbine generator system is considered in the analyses. The validity of the proposed system is verified by the simulation results which are performed using the laboratory standard dynamic power system simulator PSCAD/EMTDC. Notably, the proposed adaptive ANN-controlled SMES enhances the transient stability of wind farms connected to a multi-machine power system.

The X‐connected inverter: a topology with higher fundamental and reduced low‐order harmonic voltages

A new inverter topology is presented in the paper, which produces a reduced low-order harmonic voltage waveform because of a natural harmonic cancellation process. Two switches of each limb operate at low switching frequency, whereas the other two switches of the same limb operate at higher switching frequency in conjunction with two additional capacitors. The four switches in each limb are controlled in such a way that the sequence of switching along with the voltage of two additional capacitors cancels out the low-frequency harmonics, thereby creating a pulse-width modulation (PWM) voltage with reduced low-order harmonics at the output with respect to the dc midpoint. By selection of the PWM pattern, the magnitude of fundamental voltage produced at the output can be higher than what would be achieved using sinusoidal PWM from the same dc bus voltage, without bothering about its inherent lower-order harmonics as they would be anyway cancelled. It is thus possible to achieve maximum possible dc bus utilisation theoretically.

Analysis of Losses and Thermal in Induction Motors

This paper presents an investigation into the losses and thermal characteristics of induction motors operated from pulse width-modulated (PWM) voltage supply in comparison to that operated from sinusoidal voltage supply. It was concluded that due to the abundant harmonics in the PWM waveforms, significant losses are induced in the motor by the inverter supply. The temperature ascends correspondingly. Experiments were conducted with no load and with load conditions. The losses and thermal characteristics were calculated using finite element analysis (FEA) and validated by the experiments.