An Investigation of Series and Parallel Configurations for Hybrid Power Amplifiers

Power Hardware-in-the-Loop (PHIL) is becoming increasingly popular for compartmentalized testing of electric power equipment in several areas such as in electric drive systems and distributed power generation systems. The fundamental idea of PHIL is to create flexible conditions for Devices under Test (DUT) to be properly assessed in real time and dynamic conditions with their rated power levels. Connected to the DUT is the Power Amplifier (PA), which is responsible for increasing the voltage and current levels, given from the Real-Time Simulator (RTS). The DUT is a physical equipment and high-complexity models are used to control the PAs to emulate necessary conditions for the DUT to be evaluated. One of the main benefits of PHIL is that it can provide a platform for conducting a number of severe tests without risking damaging the equipment that is being emulated, while testing the actual response of the DUT. It can also help with the preliminary design and performance assessment of new types of machines, drivers and controllers, thus significantly reducing the time to market of new equipment. The flexibility of PHIL is also one of its main assets, since the combination of the RTS and the PA can be used for various applications only by changing the model and/or parameters of the emulated element. This thesis will evaluate the main architectures, control strategies and PHIL applications of PAs. Linear Power Amplifiers (LPA) provide an overall great performance due to its high bandwidth but are expensive, mostly at increased power ratings. For high PAs with fast dynamic response and reduced waveform distortion, the Hybrid Power Amplifier (HPA) configuration provides a good cost-performance compromise. HPAs are built essentially with the association of a low-cost Switch Mode Power Amplifier (SMPA) and an LPA. The first configuration to be investigated is the series connected HPA intended for high voltage systems. The SMPA consists of a Cascaded H-Bridge Multilevel (CHBM) converter for increased modularity. A single-pulse per H-bridge modulation technique called Nearest Level of Control (NLC) is used for minimizing the switching losses. However, this leads to unbalanced power consumption by the H-bridges when the SMPA provides relatively low output voltages, thus compromising the reliability and power quality of the SMPA. A new modulation technique called Split-Voltage Fist-In First-Out (SV-FIFO) that mitigates this issue is proposed. Its implementation requires the use of a supplemental, but simple, control loop based on the magnitude and frequency of the reference output voltage. Experimental results are presented to validate the design approach and demonstrate the high performance achieved with SV-FIFO. The parallel connected HPA is also evaluated in this thesis. In a similar way to the series connected HPA, the LPA provides high bandwidth (BW) and active power filtering while the bulk of the power is provided by the SMPA. The SMPA is realized with a three-phase Voltage Source Converter (VSC) and three single-phase LPAs. The contribution relies on proposing a new topology and current control strategy that aims to reduce the size of the required LPA, which is costly. This is achieved by using the reference current of the HPA for the current control loop of the LPA, and the actual HPA current as the reference for the SMPA current loop. By making the bandwidth of the current loop of the LPA higher than that the SMPA one, the first provides the fast transient components and harmonic filtering while the second, the bulk of the HPA current. Additionally, this thesis also covers the evaluation of techniques for Amplitude, Phase Angle and Frequency (APAF) detection for single-phase systems. Amplitude, phase and frequency detection is a key feature for the control of the series HPA, but it is also useful for other important applications, such as the synchronization of renewable sources to Alternate Current (AC) grids, which is a largely growing practice. APAF for single-phase systems are more challenging since they require additional and more complex techniques to determine the phase angle. Usually, both single and three-phase systems are designed for a single and known frequency, usually the grid’s frequency. However, a wider range of frequencies is necessary for other applications such as HPAs. This thesis will examine two proposed techniques for APAF. The first is based on the combination of the integral and derivative actions and the second is based on the modification of a zero-crossing detection system. Both systems are discussed in detail and validated experimentally

Industrial and Technological Applications of Power Electronics Systems

The Special Issue "Industrial and Technological Applications of Power Electronics Systems" focuses on: - new strategies of control for electric machines, including sensorless control and fault diagnosis; - existing and emerging industrial applications of GaN and SiC-based converters; - modern methods for electromagnetic compatibility. The book covers topics such as control systems, fault diagnosis, converters, inverters, and electromagnetic interference in power electronics systems. The Special Issue includes 19 scientific papers by industry experts and worldwide professors in the area of electrical engineering

CAPACITOR VOLTAGE BALANCING, FAULT DETECTION, AND FAULT TOLERANT CONTROL TECHNIQUES OF MODULAR MULTILEVEL CONVERTERS

Modular Multilevel Converters (MMCs) are distinguished by their modular nature that makes them suitable for wide range of high power and high voltage applications. However, they are vulnerable to internal faults because of the large number of series connected Sub-Modules. Additionally, it is highly recommended not to block the converter even if it is subjected to internal faults to secure the supply, to increase the reliability of the system and prevent unscheduled maintenance. This thesis introduces a fault tolerant control system for controlling the MMC in normal as well as abnormal operating conditions. This is done through developing a new adaptive voltage balancing strategy based on capacitor voltage estimation utilizing ADAptive LInear NEuron (ADALINE) and Recursive Least Squares (RLS) algorithms. The capacitor voltage balancing techniques that have been proposed in literature are based on measuring the capacitor voltage of each sub-module. On contrary, the proposed strategy eliminates the need of these measurements and associated communication links with the central controller. Furthermore, the thesis presents a novel fault diagnosis algorithm using the estimated capacitor voltages which are utilized to detect and localize different types of sub-module faults. The proposed fault diagnosis algorithm surpasses the methods presented in literature by its fast fault detection capability without the need of any extra sensing elements or special power circuit. Finally, a new Fault Tolerant Control Unit (FTCU) is proposed to tolerate the faults located inside the MMC submodules. The proposed FTCU is based on a sorting algorithm which modifies the parameters of the voltage balancing technique in an adaptive manner to overcome the reduction of the active submodules and secure the MMC operation without the need of full shut-down. Most of fault tolerant strategies that have been proposed by other researchers are based on using redundant components, while the proposed FTCU does not need any extra components. The dynamic performance of the proposed strategy is investigated, using PSCAD/EMTDC simulations and hardware in the loop (HIL) real-time simulations, under different normal and faulty operating conditions. The accuracy and the time response of the proposed fault detection and tolerant control units result in stabilizing the operation of the MMC under different types of faults. Consequently, the proposed integrated control strategy improves the reliability of the MMC

Single-Phase 13-Level Power Conditioning System for Peak Power Reduction of a High-Speed Railway Substation

The control and operation of a single-phase 13-level power conditioning system (PCS) for peak power reduction of a high-speed railway substation (HSRS) are proposed. This PCS is a single-phase 3100 V, 2 MVA 13-level H-bridge multi-level inverter structure. It has excellent power quality. It is easy to serialize by voltage. In addition, the DC bus power of each cell inverter is supplied by lithium-ion batteries. The generalized reduction gradient optimization algorithm based on past load pattern is applied to the power management system for peak power reduction of HSRS. The phase detector and power controller for the control of a single-phase PCS based on virtually coordinated axes using an all-pass filter are expected to be robust to external disturbances with fast response characteristics. This study also proposes an adapted select switch (ASS) method that can change the switching depending on the operation state of PCS and the state of charge (SOC) of the battery to minimize battery imbalance by controlling each cell inverter of the H-bridge. The validity of the proposed system was confirmed by PSiM simulation and experiments using a demonstration system of 6 MW PCS and 2.68 MWh batteries at one of Gyeongbu high-speed line substations in Korea. Document type: Articl

Emerging Power Electronics Technologies for Sustainable Energy Conversion

This Special Issue summarizes, in a single reference, timely emerging topics related to power electronics for sustainable energy conversion. Furthermore, at the same time, it provides the reader with valuable information related to open research opportunity niches

Emerging Power Electronics Technologies for Sustainable Energy Conversion

This Special Issue summarizes, in a single reference, timely emerging topics related to power electronics for sustainable energy conversion. Furthermore, at the same time, it provides the reader with valuable information related to open research opportunity niches

Power and Energy Student Summit 2019: 9 – 11 July 2019 Otto von Guericke University Magdeburg ; Conference Program

The book includes a short description of the conference program of the "Power and Energy Student Summit 2019". The conference, which is orgaized for students in the area of electric power systems, covers topics such as renewable energy, high voltage technology, grid control and network planning, power quality, HVDC and FACTS as well as protection technology. Besides the overview of the conference venue, activites and the time schedule, the book includes all papers presented at the conference

AVERAGE-VALUE MODELING OF HYSTERESIS CURRENT CONTROL IN POWER ELECTRONICS

Hysteresis current control has been widely used in power electronics with the advantages of fast dynamic response under parameter, line and load variation and ensured stability. However, a main disadvantage of hysteresis current control is the uncertain and varying switching frequency which makes it difficult to form an average-value model. The changing switching frequency and unspecified switching duty cycle make conventional average-value models based on PWM control difficult to apply directly to converters that are controlled by hysteresis current control. In this work, a new method for average-value modeling of hysteresis current control in boost converters, three-phase inverters, and brushless dc motor drives is proposed. It incorporates a slew-rate limitation on the inductor current that occurs naturally in the circuit during large system transients. This new method is compared with existing methods in terms of simulation run time and rms error. The performance is evaluated based on a variety of scenarios, and the simulation results are compared with the results of detailed models. The simulation results show that the proposed model represents the detailed model well and is faster and more accurate than existing methods. The slew-rate limitation model of hysteresis current control accurately captures the salient detail of converter performance while maintaining the computational efficiency of average-value models. Validations in hardware are also presented

Prädiktive Regelung und Finite-Set-Beobachter für Windgeneratoren mit variabler Drehgeschwindigkeit

This dissertation presents several model predictive control (MPC) techniques and finite-position-set observers (FPSOs) for permanent-magnet synchronous generators and doubly-fed induction generators in variable-speed wind turbines. The proposed FPSOs are novel ones and based on the concept of finite-control-set MPC. Then, the problems of the MPC techniques like sensitivity to variations of the model parameters and others are investigated and solved in this work.Die vorliegende Dissertation stellt mehrere unterschiedliche Verfahren der modellprädiktiven Regelung (MPC) und so genannte Finite-Position-Set-Beobachter (FPSO) sowohl für Synchrongeneratoren mit Permanentmagneterregung als auch für doppelt gespeiste Asynchrongeneratoren in Windkraftanlagen mit variabler Drehzahl vor und untersucht diese. Für die Beobachter (FPSO) wird ein neuartiger Ansatz vorgestellt, der auf dem Konzept der Finite-Control-Set-MPC basiert. Außerdem werden typische Eigenschaften der MPC wie beispielsweise die Anfälligkeit gegenüber Parameterschwankungen untersucht und kompensiert

Applications of MATLAB in Science and Engineering

The book consists of 24 chapters illustrating a wide range of areas where MATLAB tools are applied. These areas include mathematics, physics, chemistry and chemical engineering, mechanical engineering, biological (molecular biology) and medical sciences, communication and control systems, digital signal, image and video processing, system modeling and simulation. Many interesting problems have been included throughout the book, and its contents will be beneficial for students and professionals in wide areas of interest