Oleg Vodyakho

Three-Level Inverter-Based Shunt Active Power Filter in Three-Phase Three-Wire and Four-Wire Systems

This paper presents a direct current-space-vector control of an active power filter (APF) based on a three-level neutral-point-clamped (NPC) voltage-source inverter. The proposed method indirectly generates the compensation current reference by using an equivalent conductance of the fundamental component using APFs dc-link voltage control. The proposed control can selectively choose harmonic current components by real-time fast Fourier transform to generate the compensation current. The compensation current is represented in a rotating coordinate system with chosen switching states from a switching table implemented in a field-programmable gate array. In addition, a three-phase four-wire APF based on a three-level neutral-point-clamped inverter is also presented. The proposed APF eliminates harmonics in all three phases as well as the neutral current. A three-phase three-wire NPC inverter system can be used as a three-phase four-wire system since the split dc capacitors provide a neutral connection. To regulate and balance the split dc-capacitor voltages, a new control method using a sign cubical hysteresis controller is proposed. The characteristics of the APF system with an LCL-ripple filter are investigated and compared with traditional current control strategies to evaluate the inherent advantages. The simulation and experimental results validated the feasibility of the proposed APF.

Synchronization of three-phase converters and virtual microgrid implementation utilizing the Power-Hardware-in-the-Loop concept

This paper addresses the timely issues of synchronization and application of three-phase power converters connected in parallel utilizing the Power-Hardware-in-the-Loop concept. Without proper synchronization, distinguishing the currents circulating between the converters are unclear. The paper centers on control methodology for achieving precise phase synchronization for equal load sharing, with minimum current circulation between the paralleled power converter modules, and robust dynamic system control under different transient conditions. One of the possible applications for the configuration presented in this paper is the conceptual virtual microgrid, which utilizes the reactive power compensation ability of the Static Synchronous Compensator (STATCOM). The microgrid behavior and load dynamics are simulated with a real-time digital simulator which generates appropriate control commands to a power electronics based voltage amplifier interfaced via a cascaded LC-LC type filter to a variable speed drive (VSD). This is necessary as reactive power control is a critical consideration in improving the power quality of power systems. To compensate for reactive power, the STATCOM controller will be developed and integrated into the proposed virtual microgrid system. This concept provides a solution for de-risking these costs as it utilizes the PHIL concept in conjunction with high-fidelity microgrid model and detailed load dynamics. Selected experimental results on two, 25-kVA and 15-kVA, converters in parallel are presented.

An Induction Machine Emulator for High-Power Applications Utilizing Advanced Simulation Tools With Graphical User Interfaces

In this paper, a method is presented for removing the risk associated with the testing and development of novel drive system topologies, prototype electrical machines, advanced control system strategies, or a combination of the aforementioned without using any real motors/generators. The test platforms for low-power machines are relatively inexpensive and accessible; however, as power levels increase into the upper kilowatt and megawatt range, validation of prototype machines and drives becomes costly. The proposed induction machine emulator (IME) platform utilizes the power hardware-in-the-loop concept in conjunction with a high-fidelity machine model and load dynamics. The electrical machine and its load dynamics are simulated with a real-time digital simulator, which generates appropriate control commands to a power electronics-based voltage amplifier that interfaces to a variable speed drive (VSD). Specifically, the current draw is recreated by altering the phase and magnitude of a voltage amplifier connected to a VSD under test via a unique transformer-based LCL-type coupling network. Based on the proposed concept, the use of a multiwinding, tap-changing transformer establishes a truly versatile and universal test platform for a wide range of power levels. In addition, this paper presents a control strategy in the synchronously rotating reference frame in dq coordinates for the power electronic converters in IME operation. Experimental results at the 25-kVA power level validate the feasibility and highly dynamic performance of the proposed test platform.

Four-leg based Matrix Converter with Fault Resilient Structures and Controls for Electric Vehicle and Propulsion Systems

A study of four-leg based fault-tolerant matrix converter is presented for remedial topological structures and control techniques against both open-faults and short-faults occurring in the AC-AC matrix converter drive based electric vehicles and propulsion systems. Topologies of the matrix converter drives with additional backup leg have been proposed to allow the matrix converter based drives for tolerating both open and short phase failures. Switching function algorithms with closed form expressions, based on switching matrices, have been developed to provide the matrix converter drives with continuous and disturbance-free operation after opened phase faults and shorted phase failures. The developed switching function matrix and modified topological configuration allow to synthesize redefined output waveforms under open-switch, open-phase, and shorted load motor winding faults. In addition, the proposed matrix converter topology can produce three-phase balanced sinusoidal output currents even after short-switch failures. Simulation and experimental results show the feasibility of the proposed topologies and the developed switching function techniques in case of both the open and short faults.

Design of a solid state fault isolation device for implementation in power electronics based distribution systems

This paper addresses the timely issues of modeling of, and defining selection criteria for, a solid state fault isolation device (SSFID) to be used in power electronic based distribution systems. The paper derives the SSFID parameters by mapping the characteristics of a conventional medium-voltage distribution system onto that of the power electronic based Future Renewable Electric Energy Delivery and Management (FREEDM) system envisioned under a new multi-university Engineering Research Center funded by the National Science Foundation. Major drawbacks of all SSFID solutions presented so far are material costs and on-state losses. Power semiconductor devices are briefly compared considering the requirements of a solid state switch integrated into a 15 kV class medium voltage grid. A design of a high frequency Solid State Transformer (SST) is presented and evaluated. The simulation results verify the functionality and feasibility of SST. Utilizing an average-value simulation model of a SST, as the interface of the power electronics based distribution system to the legacy system, is used to derive key parameters of the SSFID. Circuit interruption requirements and SSFID location in power electronics based distribution system are discussed in this paper. The simulation and experimental results in low voltage single phase system validated the feasibility of the proposed SSFID topology. Finally, the conceptual Power Hardware-in-the-Loop setup for SSFID testing is presented and discussed in this paper.

Novel Direct Current-Space-Vector Control for shunt active power filters based on three-Level inverters

The permanently growing number of electric drives with non-sinusoidal line currents has given increased interest in active power filters (APF), to avoid grid problems caused by harmonic distortions. In this paper, a novel direct current-space-vector control scheme (DCSVC) is presented for a three-level, neutral- point-clamped voltage-source inverter, which is employed as an active power filter. The proposed method works in the time domain, generating the equivalent ohmic conductance indirectly by means of the dc-link voltage control of the APF. Based on the Fast Fourier Transform (FFT) the compensation of the reactive fundamental current can be cancelled, confining the operation to only harmonic compensation and thus saving the APFs apparent power. The novel direct current-space-vector controller, operating in synchronously rotating coordinates is implemented in a field programmed gate array (FPGA), realizing the switching states from switching tables. The proposed control reduces the average switching frequency and thus, the switching power loss significantly, compared with a previous direct current-space-vector control, operating in stationary coordinates. Simulation and experimental results validate the feasibility and highly dynamic performance of the proposed control, both for harmonic and total non-active current compensation.

Power semiconductor loss evaluation in voltage source IGBT converters for three-phase Induction Motor drives

This paper addresses the timely issues of power loss calculation methods in the most common voltage source three phase PWM converters (VSC). There are mainly two kinds of power semiconductor losses to be considered, the conduction losses and the switching losses. A reconfigurable Induction Motor (IM) drive is controlled by the conventional PWM and space vector PWM based methods. The power losses will be evaluated with the different control strategies and verified based on the test-bed using a control system rapid prototyping environment such as dSPACE.

Virtual battery charging station utilizing power-hardware-in-the-loop: Application to V2G impact analysis

With the issues of fuel cost and environmental impact on the rise, the concept of replacing conventional vehicles with plug-in hybrid electric vehicles (PHEVs) has become essential. The main goal of PHEV implementation focuses on the ability to utilize electrical propulsion to assist the internal combustion engine. However, the batteries for the PHEV must be recharged using grid energy. This paper will study the effects of PHEV charging at the sub-transmission level through modeling/simulation and power hardware in the loop including an actively controlled drive system and controllable load.

Fuel Cell Hybrid Electric Scooter

In this article, the structure and control of a fuel cell hybrid electric scooter for mass production are presented. The development of a zero-emission scooter can improve air quality and protect the environment, especially in Asia and Europe, where more than 25 million scooters are produced annually. The generic advantages of low-pressure hydrogen storage of the fuel-cell-powered scooter are explained, and the control strategies of the hybrid scooter are presented. Additionally, experimental verifications and discussions are presented based on a prototype system controller.

Development of solid-state fault isolation devices for future power electronics-based distribution systems

This paper addresses the timely issues of modeling, and defining selection criteria for, a solidstate fault isolation device (FID) intended for use in power electronics-based distribution systems (PEDS). The paper subsequently derives the FID parameters in the PEDS envisioned under a new multi-university Engineering Research Center funded by the US National Science Foundation. When conventional circuit breakers are used in distribution systems, they have relatively long clearing times, causing feeder voltages to be reduced for a significant amount of time. Although acceptable in convention systems, this relatively long clearing time would cause significantly long, complete voltage collapses in a PEDS. Sensitive loads such as computers would fail even if the voltage returns within a few seconds. However, if a semiconductor circuit breaker were to be used instead of the conventional system, it would be able to switch fast enough to keep the time of voltage disturbances within acceptable limits. This paper discusses the management of the overvoltage resulting from very fast circuit breaker operation through the use of passive clamping devices and di/dt control during turn-off. The paper includes experimental results at medium voltage from a developed hardware prototype. In addition, a validated simulation model of a medium voltage FID was developed for future studies. Simulation results are presented.