Venkata Dinavahi

Interharmonics: Theory and Modeling

Some of the most remarkable issues related to interharmonic theory and modeling are presented. Starting from the basic definitions and concepts, attention is first devoted to interharmonic sources. Then, the interharmonic assessment is considered with particular attention to the problem of the frequency resolution and of the computational burden associated with the analysis of periodic steady-state waveforms. Finally, modeling of different kinds of interharmonic sources and the extension of the classical models developed for power system harmonic analysis to include interharmonics are discussed. Numerical results for the issues presented are given with references to case studies constituted by popular schemes of adjustable speed drives.

Detailed modeling of CIGRE HVDC benchmark system using PSCAD/EMTDC and PSB/SIMULINK

This paper focuses on a comparative study of the modeling and simulation of the first CIGRE HVDC benchmark system using two simulation tools PSCAD/EMTDC and PSB/SIMULINK; an interface between them (PSCAD-SIMULINK) has also been implemented and used as a simulator. The CIGRE HVDC system and its controller has been carefully modeled in all three simulation environments so that the differences are minimal. Comparison of steady-state and transient situations have been carried out, and a high degree of agreement in most of the cases has been observed.

FPGA-Based Real-Time Emulation of Power Electronic Systems With Detailed Representation of Device Characteristics

This paper presents a field-programmable gate array (FPGA)-based real-time digital simulator for power electronic apparatus based on a realistic device-level behavioral model. A three-level 12-pulse voltage source converter (VSC)-fed induction machine drive is implemented on the FPGA. The VSC model is computed at a fixed time step of 12.5 ns, allowing a realistic representation of insulated-gate bipolar transistor (IGBT) nonlinear switching characteristics and power losses. The simulator also models a squirrel-cage induction machine, a direct field-oriented control system, and a pulsewidth modulator to achieve the real-time simulation of the complete drive system. All the models have been implemented using very high speed integrated circuit hardware description language (VHDL). Real-time simulation results have been validated using the measured device-level IGBT characteristics.

A versatile cluster-based real-time digital simulator for power engineering research

This paper presents the development of a unique parallel and distributed real-time digital simulator for power engineering research at the University of Alberta. The simulator is built entirely from commodity-off-the-shelf (COTS) hardware and software components, making it very flexible and scalable. In parallel multi-tasking operations, a combination of real-time Linux operating system and an ultra-fast network forms the backbone for the internal communication between the 16 powerful processors of the Xeon-Cluster. Field programmable gate array (FPGA)-based multi-channel digital and analog I/O ports are interfaced to communicate with the external hardware components. The model development software utilized for power applications is based on the highly customizable industry-standard MATLAB/SIMULINK environment. A detailed case study of the real-time simulation of a three-level 12-pulse vector-controlled ac drive is presented to illustrate the precision capabilities of the simulator. Multiple integration algorithms and multirate computation have been applied for the simulation of the system, with slow (machine) and fast (converter) dynamic components. Real-time simulation of the entire system has been achieved with a maximum computation time of 5.35 /spl mu/s on a step-size of 10 /spl mu/s for the first time. Results obtained from the real-time simulation have been validated with an offline simulation using PSCAD/EMTDC.

Simulation Tools for Electromagnetic Transients in Power Systems: Overview and Challenges

This paper presents an overview on available tools and methods for the simulation of electromagnetic transients in power systems. Both off-line and real-time simulation tools are presented and discussed. The first objective is to give the reader an overview on the modeling and simulation capabilities in currently available state-of-the-art tools. The second objective is to provide perspectives on research topics and needed enhancements.

Experimental Validation of Nonlinear Control for a Voltage Source Converter

In this brief, we consider reactive power and DC voltage tracking control of a three-phase voltage source converter (VSC). This control problem is important in many power system applications including power factor correction for a distribution static synchronous compensator (D-STATCOM). Traditional approaches to this problem are often based on a linearized model of the VSC and proportional-integral (PI) feedback. In order to improve performance, a flatness-based tracking control for the VSC is proposed where the nonlinear model is directly compensated without a linear approximation. Flatness leads to straightforward open-loop control design. A full experimental validation is given as well as a comparison with the industry-standard decoupled vector control. Robustness of the flatness-based control is investigated and setpoint regulation for unbalanced three-phase voltage is considered.

Dynamic System Equivalents: A Survey of Available Techniques

This paper presents a brief review of techniques available for reducing large systems to smaller equivalents. The paper is divided into High Frequency Equivalents, Low Frequency Equivalents, and Wide-band Equivalents.

A review of power converter topologies for wind generators

Wind energy conversion systems have become a focal point in the research of renewable energy sources. This is in no small part due to the rapid advances in the size of wind generators as well as the development of power electronics and their applicability in wind energy extraction. This paper provides a comprehensive review of past and present converter topologies applicable to permanent magnet generators, induction generators, synchronous generators and doubly fed induction generators. The many different generator-converter combinations are compared on the basis of topology, cost, efficiency, power consumption and control complexity. The features of each generator-converter configuration are considered in the context of wind turbine systems

Interfacing Issues in Real-Time Digital Simulators

This paper deals with the current state-of-the-art in interfacing issues related to real-time digital simulators employed in the simulation of power systems and power-electronic systems. This paper provides an overview of technical challenges encountered and their solutions as the real-time digital simulators evolved. Hardware-in-the-loop interfacing for controller hardware and power apparatus hardware are also presented.

SIMD-Based Large-Scale Transient Stability Simulation on the Graphics Processing Unit

This paper presents a single-instruction-multiple-data (SIMD) based implementation of the transient stability simulation on the Graphics Processing Unit (GPU). Two programming models to implement the standard method of the transient stability simulation are proposed and implemented on a single GPU. In the first model the CPU is responsible for part of the simulation, while the onerous computations were offloaded to the GPU, creating a hybrid GPU-CPU simulator. In the second model, the GPU performs all the computations, while the CPU simply monitors the flow of the simulation. The accuracy of the proposed methods are validated using the PSS/E software for several large test systems. A substantial increase in speed was observed for the GPU-based simulations.