Review on Adjustable Speed Drive Techniques of Matrix Converter Fed Three-Phase Induction Machine

Adjustable Speed Drive (ASD) fed Matrix Converter is an interesting topic and is widely discussed in several articles. ASD provides many advantages, especially in the industrial sector because it increases work efficiency so as to reduce production costs. The induction machines construction is sturdy and its relatively inexpensive maintenance makes it more desirable in industrial process applications. Whereas the Matrix Converter (MC) construction without dc-link capacitors makes it more compact compared to conventional converters. This article discussed the ASD control modulation technique by using MC on a three-phase induction motor

Analysis and design of matrix converters for adjustable speed drives and distributed power sources

Recently, matrix converter has received considerable interest as a viable alternative to the conventional back-to-back PWM (Pulse Width Modulation) converter in the ac/ac conversion. This direct ac/ac converter provides some attractive characteristics such as: inherent four-quadrant operation; absence of bulky dc-link electrolytic capacitors; clean input power characteristics and increased power density. However, industrial application of the converter is still limited because of some practical issues such as common mode voltage effects, high susceptibility to input power disturbances and low voltage transfer ratio. This dissertation proposes several new matrix converter topologies together with control strategies to provide a solution about the above issues. In this dissertation, a new modulation method which reduces the common mode voltage at the matrix converter is first proposed. The new method utilizes the proper zero vector selection and placement within a sampling period and results in the reduction of the common mode voltage, square rms of ripple components of input current and switching losses. Due to the absence of a dc-link, matrix converter powered ac drivers suffer from input voltage disturbances. This dissertation proposes a new ride-through approach to improve robustness for input voltage disturbances. The conventional matrix converter is modified with the addition of ride-through module and the add-on module provides ride-through capability for matrix converter fed adjustable speed drivers. In order to increase the inherent low voltage transfer ratio of the matrix converter, a new three-phase high-frequency link matrix converter is proposed, where a dual bridge matrix converter is modified by adding a high-frequency transformer into dc-link. The new converter provides flexible voltage transfer ratio and galvanic isolation between input and output ac sources. Finally, the matrix converter concept is extended to dc/ac conversion from ac/ac conversion. The new dc/ac direct converter consists of soft switching full bridge dc/dc converter and three phase voltage source inverter without dc link capacitors. Both converters are synchronized for zero current/voltage switching and result in higher efficiency and lower EMI (Electro Magnetic Interference) throughout the whole load range. Analysis, design example and experimental results are detailed for each proposed topology

Low Voltage Ride-Through for Indirect Matrix Converter Based Open-End Winding Drives

University of Minnesota Ph.D. dissertation. September 2017. Major: Electrical Engineering. Advisor: Ned Mohan. 1 computer file (PDF); viii, 58 pages.Adjustable speed drives (ASD) are one of the major load components in power systems and with the advent of wide band gap devices, which provide efficiencies greater than 95%, variable frequency drives will continue to grow and integrate into the systems. ASDs serve a varied set of processes including HVACs, oilrigs and recently many electric vehicles (EV). The most commonly employed types are the DC-to-AC or AC-to-AC drives with DC/AC drives being more popular in storage and EV applications. AC/AC drives have been dominated by converters using large capacitors with DC bus viz. back-to-back converters. These converters are becoming more reliable and have been tested with new advancements in the industry. In addition, the DC bus capacitor provides an inbuilt energy storage mechanism, which could be used for ride-through operations during fault conditions. In some applications like wind turbines, the presence of large capacitive and reactive components in the drive could be a drawback due to lesser reliability and increased weight. Hence, converters that eliminate the need for large capacitors (viz. cycloconverters and matrix converters) are advantageous in such applications. Matrix converters (MC) have been in research and development for almost three decades, and several topologies and new modulation techniques have been proposed. In addition to elimination of the bulky DC bus capacitor, MCs provide sinusoidal input and output waveforms with lesser harmonics, and have inherent bi-directional power flow capability while offering full input power factor control. In industry, MCs are produced by few manufacturers and is still a niche product. High frequency common mode voltage (CMV) switching is a by-product of the ASDs operating at medium to high frequencies and cause bearing currents to flow, which damage the machine and reduce their lifetime. Elimination or reduction of common mode voltage is a well-researched topic and it has been addressed with plenty of solutions for different kind of drives. One of the recently developed solution is the usage of open-end winding drive modulated using rotating space vectors. Open-end winding machine is constructed by opening the shorted side of an induction machine, which is supplied by another similar converter. Different types of converters including MCs have been used to construct this drive. Matrix converter based open-end winding drive have two types including direct and indirect matrix converter based drives and, this dissertation concentrates on the usage of a three-level indirect matrix converter based open-end winding. It is important that the ASDs are reliable and dependable during fault conditions in the power system. They should be able to ride-through the fault, supply the losses, and maintain the flux in the motor since re-building it could affect the operations. System faults could create over-voltages or voltage sags (sags are more frequent than over-voltages) and many commercial drives address the voltage sag problem with a ride-through solution for up to 30 cycles of interruption. Ride-through solutions include usage of storage devices, modification of the drive or use of inherent kinetic energy. Matrix converters lack an inbuilt storage device and modification of the drive could be expensive. This dissertation proposes a low voltage ride-through method for a three-level indirect matrix converter based open-end winding drive using the input filter capacitor. The three-level indirect MC drive has an advantage over other matrix converter based drives, that it can provide a ride-through solution without the need for modifications or addition of storage devices. The input filter capacitor on the three-level bus between the front-end converter and the two three level inverters is used as the voltage source during the fault while its voltage is maintained by using the kinetic energy from the motor. This is achieved by modification of control loops in a traditional vector control configuration to control the capacitor voltage by drawing power from the motor. In summary, this dissertation describes a three-level indirect matrix converter for an open-end winding drive to eliminate the high frequency common-mode voltage, and proposes a low voltage ride-through method for the operation of the drive during fault conditions using the input filter capacitors as an energy transfer device. The method has been presented with detailed derivations and analyses and been verified using simulations and experimental results using a two-level inverter drive

Improved vector control methods for brushless double fed induction generator during inductive load and fault conditions

A Brushless Double-Fed Induction Generator (BDFIG) has shown tremendous success in wind turbines due to its robust brushless design, less maintenance, smooth operation, and variable speed characteristics. These generators are composed of two back-to-back voltage source converters, a Grid Side Converter (GSC) and a Rotor Side Converter (RSC). Existing control techniques use a “trial and error” method that results in a poor dynamic response in machine parameters during the absence of load. The RSC control is used for reactive current control during the inductive load insertion. However, it is more suitable for stabilizing steady-state behaviour, but it suffers from slow response and introduces a double fundamental frequency component to the Point of Common Coupling (PCC) voltage. In addition, generally, a Low Voltage Ride Through (LVRT) fault is detected using a hysteresis comparison of the power winding voltage. The LVRT capability is provided by using fixed reference values to control the winding current. This approach results in an erroneous response, sub-optimal control of voltage drops at PCC, and false alarms during transient conditions. This thesis aims to solve the mentioned issues by using an improved vector control method. Internal Model Control (IMC) based Proportional-Integral (PI) gains calculation is used for GSC and RSC. These are controlled to enhance the transient response and power quality during no-load, inductive load, and fault conditions. Firstly, a GSC-based vector control method is proposed to suppress the PCC voltage fluctuations when a large inductive load is suddenly connected. The proposed technique is based on an analytical model of the transient behaviour of the voltage drop at the PCC. To block a double fundamental frequency component as a result of reactive current compensation, a notch filter is designed. Secondly, an RSC-based vector control method is proposed using an analytical model of the voltage drop caused by a short circuit. Moreover, using a fuzzy logic controller, the proposed technique employs the voltage frequency in addition to the power winding voltage magnitude to detect LVRT conditions. The analytical model helps in reducing the power winding voltage drop while the fuzzy logic controller leads to better response and faster detection of faults. However, the reference value for reactive current compensation is analysed using an analytical model of the voltage drop at the PCC in the event of a short-circuit fault. The results obtained from MATLAB/Simulink show that the GSC-based vector control method technique can effectively reduce about 10% voltage drop at PCCs. Total Harmonics Distortion (THD) is improved to 22.3% by notch filter in comparison with an existing technique such as instantaneous reactive power theory. The RSC-based vector control method can achieve up to 11% voltage drop reduction and improve the THD by 12% compared to recent synchronous control and flux tracking methods

Unified Power Quality Conditioner for Grid Integration of Wind Generators

A Unified Power Quality Conditioner (UPQC) is relatively a new member of the custom power device family. It is a comprehensive custom power device, with integrated shunt and series active filters. The cost of the device, which is higher than other custom power/FACTS devices, because of twin inverter structure and control complexity, will have to be justified by exploring new areas of application where the cost of saving power quality events outweighs the initial cost of installation. Distributed generation (such as wind generation) is one field where the UPQC can find its potential application. There has been a considerable increase in the power generation from wind farms. This has created the necessity for wind farms connectivity with the grid during power system faults, voltage sags and frequency variations. The application of active filters/custom power devices in the field of wind generation to provide reactive power compensation, additional fault ride through capability and to maintain Power Quality (PQ) at the point of common coupling is gaining popularity. Wind generation like other forms of distributed generation often relies on power electronics technology for flexible interconnection to the power grid. The application of power electronics in wind generation has resulted in improved power quality and increased energy capture. The rapid development in power electronics, which has resulted in high kVA rating of the devices and low price per kVA, encourages the application of such devices at distribution level. This work focuses on development of a laboratory prototype of a UPQC, and investigation of its application for the flexible grid integration of fixed and variable speed wind generators through dynamic simulation studies. A DSP based fully digital controller and interfacing hardware has been developed for a 24 kVA (12 kVA-shunt compensator and 12 kVA-series compensator) laboratory prototype of UPQC. The modular control approach facilitates the operation of the device either as individual series or shunt compensator or as a UPQC. Different laboratory tests have been carried out to demonstrate the effectiveness of developed control schemes.A simulation-based analysis is carried out to investigate the suitability of application of a UPQC to achieve Irish grid code compliance of a 2 MW Fixed Speed Induction Generator (FSIG). The rating requirement of the UPQC for the wind generation application has been investigated. A general principle is proposed to choose the practical and economical rating of the UPQC for this type of application. A concept of UPQC integrated Wind Generator (UPQC-WG) has been proposed. The UPQC-WG is a doubly fed induction machine with converters integrated in the stator and rotor circuits and is capable of adjustable speed operation. The operation of UPQC-WG under sub and super-synchronous speed range has been demonstrated. The Irish grid code compliance of the same has been demonstrated with a detailed dynamic simulation

Cumulative index to NASA Tech Briefs, 1963-1965

Annotated bibliography of NASA technical briefs on electrical, energy sources, materials, life sciences, and mechanical informatio

Mitigation of power quality issues due to high penetration of renewable energy sources in electric grid systems using three-phase APF/STATCOM technologies: a review.

This study summarizes an analytical review on the comparison of three-phase static compensator (STATCOM) and active power filter (APF) inverter topologies and their control schemes using industrial standards and advanced high-power configurations. Transformerless and reduced switch count topologies are the leading technologies in power electronics that aim to reduce system cost and offer the additional benefits of small volumetric size, lightweight and compact structure, and high reliability. A detailed comparison of the topologies, control strategies and implementation structures of grid-connected high-power converters is presented. However, reducing the number of power semiconductor devices, sensors, and control circuits requires complex control strategies. This study focuses on different topological devices, namely, passive filters, shunt and hybrid filters, and STATCOMs, which are typically used for power quality improvement. Additionally, appropriate control schemes, such as sinusoidal pulse width modulation (SPWM) and space vector PWM techniques, are selected. According to recent developments in shunt APF/STATCOM inverters, simulation and experimental results prove the effectiveness of APF/STATCOM systems for harmonic mitigation based on the defined limit in IEEE-519

Index to NASA Tech Briefs, January - June 1966

Index to NASA technological innovations for January-June 196

Review of the State-of-the-Art in Power Electronics Suitable for 10-KW Military Power Systems

The purpose of this report is to document the technological opportunities of integrating power electronics-based inverters into a TEP system, primarily in the 10-kW size range. The proposed enhancement offers potential advantages in weight reduction, improved efficiency, better performance in a wider range of generator operating conditions, greater versatility and adaptability, and adequate reliability. In order to obtain strong assurance of the availability of inverters that meet required performance and reliability levels, a market survey was performed. The survey obtained positive responses from several manufacturers in the motor drive and distributed generation industries. This study also includes technology reviews and assessments relating to circuit topologies, reliability issues, vulnerability to pulses of electromagnetic energy, potential improvements in semiconductor materials, and potential performance improvement through cryogenics