Power Angle Control Scheme for Integration of UPQC in Grid Connected PV System

The quality of electric power is greatly affected by the proliferation of non-linear loads in electrical energy processing applications like switched mode power supplies, electric motor drives, battery chargers, etc., The custom power devices like UPQC has gained more importance in power quality arena as it gives the best solution for all power quality issues. UPQC is the combination of both shunt and series active power filters connected through a common DC link capacitor. The shunt active power filter is the most corrective measure to remove the current related problems, power factor improvement by supplying reactive power and regulates DC link voltage. The series APF acts as controlled voltage source and corrects voltage related problems, like sag or swell, flickering, harmonics, etc.,. As a combination of both of these, UPQC improves service reliability. In the present work, shunt inverter control is based on modified active- reactive (p-q) power theory, uses High selectivity filter (HSF) for reference current generation. The series APF uses Power Angle Control (PAC) scheme for compensating sag/swell, interruption and voltage related problems along with sharing a part of load reactive power demand with shunt APF and thus ease its loading and makes the utilization of UPQC to be optimal. The topology uses three phase three leg inverters for both shunt APF and series APF. The gating signals were generated using Hysteresis controller. The output of High step-Up DC-DC Converter is used to work as DC voltage source for both APFs. The input voltage for the converter is provided by Photo Voltaic array incorporated with P&O MPPT technique. The use of high step-up DC-DC converter is for high voltage gain with better efficiency. The present topology avoids the PLL in shunt active power filter. The simulation results are presented to show the effectiveness of the three phase, three-wire PV-UPQC and here obtained an acceptable THD for source current and kept load voltag

Power loss investigation of series-connected current source inverters

Current-source inverters (CSIs) are a type of direct current (DC) to alternating current (AC) converters that generate a defined AC output current waveform from a DC current supply. As the counterpart of voltage source inverters (VSIs), they feature a simple converter structure, low switching dv/dt on the ac-side, and reliable short-circuit protection. These advantages have made CSIs widely used in high power medium voltage drives. Besides, they have also been studied in other applications, such as wind energy conversion systems, superconducting magnetic energy storage (SMES) systems, and microgrid systems. Different topologies of CSIs and modulation schemes have been evolved to tailor various application requirements. For those applications with a higher power rating, two or more CSIs can be connected in series to form series-connected CSIs (SC-CSIs) to increase the power handling capability. To the best of the author’s knowledge, three topologies of SC-CSIs have been developed so far. The first topology referred to as topology A is constructed by connecting several identical CSIs in series. These CSIs are identical in terms of topology, modulation, and control. A multi-winding transformer is employed at the output to provide a clear current path for each CSI and step up the voltage if necessary. In the second topology designated as topology B, the multi-winding transformer is replaced by a phase-shifting transformer, and a phase-shifting modulation scheme is implemented. This topology features an increased DC current utilization, decreased switching losses, and reduced passive components. The third topology denominated as topology C adopts a different arrangement of switches leading to a reduced number of switching devices. A multi-winding transformer is used at the output in this topology. Power losses are an important attribute of SC-CSIs since they have a significant impact on the efficiency of the system. Besides, it is necessary to find out the power loss distribution of inverters to design an appropriate cooling system. However, the power losses and the power loss distribution of these three topologies have not been figured out. [...

Multilevel Converters: An Enabling Technology for High-Power Applications

| Multilevel converters are considered today as the state-of-the-art power-conversion systems for high-power and power-quality demanding applications. This paper presents a tutorial on this technology, covering the operating principle and the different power circuit topologies, modulation methods, technical issues and industry applications. Special attention is given to established technology already found in industry with more in-depth and self-contained information, while recent advances and state-of-the-art contributions are addressed with useful references. This paper serves as an introduction to the subject for the not-familiarized reader, as well as an update or reference for academics and practicing engineers working in the field of industrial and power electronics.Ministerio de Ciencia y Tecnología DPI2001-3089Ministerio de Eduación y Ciencia d TEC2006-0386

The Essential Role and the Continuous Evolution of Modulation Techniques for Voltage-Source Inverters in the Past, Present, and Future Power Electronics

The cost reduction of power-electronic devices, the increase in their reliability, efficiency, and power capability, and lower development times, together with more demanding application requirements, has driven the development of several new inverter topologies recently introduced in the industry, particularly medium-voltage converters. New more complex inverter topologies and new application fields come along with additional control challenges, such as voltage imbalances, power-quality issues, higher efficiency needs, and fault-tolerant operation, which necessarily requires the parallel development of modulation schemes. Therefore, recently, there have been significant advances in the field of modulation of dc/ac converters, which conceptually has been dominated during the last several decades almost exclusively by classic pulse-width modulation (PWM) methods. This paper aims to concentrate and discuss the latest developments on this exciting technology, to provide insight on where the state-of-the-art stands today, and analyze the trends and challenges driving its future

A comprehensive analysis of SVPWM for a Five-phase VSI based on SiC devices applied to motor drives

© 2019 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.This paper presents a comprehensive analysis of SVPWM for a five-phase VSI based on SiC devices applied to motor drives. The modulation techniques analyzed use medium and large vectors to reach the reference vector. The 2L SVPWM uses two large space vectors, and the generated output signal contain low frequency harmonics. 2L+2M SVPWM uses two large and two medium space vectors. This technique provides good power loss distribution. 4L SVPWM works with the activation of four large space vectors. This modulation is able to generate low common-mode voltage. The performance and main features are analyzed using Matlab/Simulink and PLECS blockset software. Power losses, total harmonic distortion and common-mode voltage are compared and evaluated.Postprint (author's final draft

Reduction of switching losses and passive components rating in series-connected current source inverters

The current source inverter (CSI) is widely used in medium voltage drives due to its simple configuration, reliable short-circuit protection, and low dv/dt issue. Conventional series-connected current source inverters (SC-CSI) are constituted of several current source inverters (CSIs) connected in series through multi-winding transformers to enhance the power capacity. It is very promising in high-voltage applications. Switching losses of the semiconductor switches significantly impact the power efficiency of SC-CSIs. Therefore, inverter design must consider these losses, which depend on factors, such as switching frequency, modulation schemes and semiconductor parameters. This thesis aims to reduce the switching losses of conventional SC-CSIs by decreasing the switching frequency from 540 Hz to 360 Hz and eventually to 60 Hz. In Chapter 2, the switching frequency is reduced to 360 Hz for the switching loss reduction. The active damping control is implemented to mitigate the increase in filter capacitance caused by the lower switching frequency. Chapter 3 is to further reduce the switching losses by reducing the switching frequency to 60 Hz. However, this strategy results in a significant increase in the passive components. To address this issue, the multi-winding transformer is replaced with a phase-shifting transformer, as the active damping method applied in Chapter 2 is no longer effective at this reduced frequency. The switching losses and the passive components of SC-CSIs are investigated with switching frequencies of 540Hz, 360Hz and 60 Hz. Simulations are conducted using MATLAB/SIMULINK to verify the investigation

Multiphase induction motor drives - a technology status review

The area of multiphase variable-speed motor drives in general and multiphase induction motor drives in particular has experienced a substantial growth since the beginning of this century. Research has been conducted worldwide and numerous interesting developments have been reported in the literature. An attempt is made to provide a detailed overview of the current state-of-the-art in this area. The elaborated aspects include advantages of multiphase induction machines, modelling of multiphase induction machines, basic vector control and direct torque control schemes and PWM control of multiphase voltage source inverters. The authors also provide a detailed survey of the control strategies for five-phase and asymmetrical six-phase induction motor drives, as well as an overview of the approaches to the design of fault tolerant strategies for post-fault drive operation, and a discussion of multiphase multi-motor drives with single inverter supply. Experimental results, collected from various multiphase induction motor drive laboratory rigs, are also included to facilitate the understanding of the drive operatio

New Modulation Technique to Mitigate Common Mode Voltage Effects in Star-Connected Five-Phase AC Drives

Star-connected multiphase AC drives are being considered for electromovility applications such as electromechanical actuators (EMA), where high power density and fault tolerance is demanded. As for three-phase systems, common-mode voltage (CMV) is an issue for multiphase drives. CMV leads to shaft voltages between rotor and stator windings, generating bearing currents which accelerate bearing degradation and produce high electromagnetic interferences (EMI). CMV effects can be mitigated by using appropriate modulation techniques. Thus, this work proposes a new Hybrid PWM algorithm that effectively reduces CMV in five-phase AC electric drives, improving their reliability. All the mathematical background required to understand the proposal, i.e., vector transformations, vector sequences and calculation of analytical expressions for duty cycle determination are detailed. Additionally, practical details that simplify the implementation of the proposal in an FPGA are also included. This technique, HAZSL5M5-PWM, extends the linear range of the AZSL5M5-PWM modulation, providing a full linear range. Simulation results obtained in an accurate multiphase EMA model are provided, showing the validity of the proposed modulation approach.This work has been supported in part by the Government of the Basque Country within the fund for research groups of the Basque University system IT978-16 and in part by the Government of the Basque Country within the research program ELKARTEK as the project ENSOL (KK-2018/00040)

Drive systems for operation on deep-sea ROVs

Power systems for thruster actuators and other auxiliaries employed on work-class deep-sea ROVs subject to 300bar ambient pressures, are considered. Emphasis on 3×3 matrix converters for thrusters and 3×2 matrix converters for system auxiliaries, is given, along with experimental results showing operation during pressure cycling consistent with typical operational duties