Atousa Yazdani

Fault Detection and Mitigation in Multilevel Converter STATCOMs

Many static synchronous compensators (STATCOMs) utilize multilevel converters due to the following: 1) lower harmonic injection into the power system; 2) decreased stress on the electronic components due to decreased voltages; and 3) lower switching losses. One disadvantage, however, is the increased likelihood of a switch failure due to the increased number of switches in a multilevel converter. A single switch failure, however, does not necessarily force an (2n + 1)-level STATCOM offline. Even with a reduced number of switches, a STATCOM can still provide a significant range of control by removing the module of the faulted switch and continuing with (2n - 1) levels. This paper introduces an approach to detect the existence of the faulted switch, identify which switch is faulty, and reconfigure the STATCOM. This approach is illustrated on an eleven-level STATCOM and the effect on the dynamic performance and the total harmonic distortion (THD) is analyzed.

An Improved Nonlinear STATCOM Control for Electric Arc Furnace Voltage Flicker Mitigation

Electric arc furnaces (EAF) are prevalent in the steel industry to melt iron and scrap steel. EAFs frequently cause large amplitude fluctuations of active and reactive power and are the source of significant power quality disturbances. Static Synchronous Compensators (STATCOMs) provide a power electronic-based means of embedded control for reactive power support and power quality improvement. This paper introduces a new nonlinear control for the STATCOM that provides significant reduction in EAF-induced aperiodic oscillations on the power system. This method is compared with traditional PI controls and shown to have improved performance.

Application of STATCOM for power quality improvement

The application of a STATCOM can help to alleviate some of the power quality issues encountered within a refinery consisting of large induction machine loads. The intent of this paper is to demonstrate the improvements obtained with STATCOM for this purpose and also to evaluate economical benefits obtained with it. First, the paper identifies the power quality and other issues around the refinery in the Southern California Edison system. Computer simulations show that the application of a STATCOM can help the big motor load to survive under the most severe contingencies occurring in the area. The analysis also demonstrates that the STATCOM with appropriate controller can be very effective in harmonic reduction.

Southern California Edison High Penetration Photovoltaic Project - Year 1

This report discusses research efforts from the first year of a project analyzing the impacts of high penetration levels of photovoltaic (PV) resources interconnected onto Southern California Edisons (SCEs) distribution system. SCE will be interconnecting a total of 500 MW of commercial scale PV within their service territory by 2015. This Year 1 report describes the need for investigating high-penetration PV scenarios on the SCE distribution system; discusses the necessary PV system modeling and distribution system simulation advances; describes the available distribution circuit data for the two distribution circuits identified in the study; and discusses the additional inverter functionality that could be implemented in order to specifically mitigate some of the undesirable distribution system impacts caused by high-penetration PV installations.

Control and monitoring requirements for distribution systems with high penetration of renewable energy sources

Proliferation of renewable and alternative energy resources as part of distribution systems is changing the paradigm of design and operation. This paper describes some of the expected issues due to integrating renewable energy resources at distribution levels and investigates the needs for deployment and/or enhancement of additional/existing measurement devices and controls on distribution grids. The aim is to determine the requirement for installation of accurate meters, how the data will be used, and what analytical applications are needed to detect and mitigate a power quality issues before it becomes widespread and causes cascading failure.

Frequency dependent line modeling and equipment sizing for a transmission level wind farm integration

Due to environmental impacts of traditional energy production, the integration of renewable energy in high volume has become more favorable. A series of analytical studies are required prior to integration of windfarms into the transmission system. For instance, equipment sizing and high voltage analysis are some of the crucial assessments. Equipment sizing in high voltage substation is done considering Transient Over Voltage (TOV) quantity that any device may tolerate due to experiencing surge and/or switching. The high elevation levels that windfarms are installed, make them more susceptible to TOVs related to lightning strikes. This paper focuses on sizing the required protecting devices in a windfarm interconnected to transmission system through a high voltage substation. The study methodology is suitable for fast transient analysis such as lightning analysis.

Enhancement of power system stability with VSC-HVDC transmission

The bulk power system is renovated with the introduction of power electronic devices and renewable energy. Maintaining the stability of the renovated system has been a concern for many years. HVDC transmission system has the advantage of transmitting vast electric power over a long distance with less amount of voltage drop or electric losses. With increase in power electronics technology, HVDC transmission is becoming the primary choice in power industry when dealing with long transmission lines. An advanced technology with Voltage Source Converter (VSC) in HVDC have the ability can provide secure lossless power delivery. This paper presents a study of power system stability using a VSC-HVDC link in a hybrid 8 bus transmission system. The purpose of this study is to show the modifying effect of HVDC system based on VSC technology on power system stability. Several cases studies are tested to push the system to its operational limits by applying single phase and three phase faults.

Distributed generation effects on voltage profile of distribution grid with SVC and Smart Inverter

Increased penetration levels of Distributed Generation (DG) can cause steady state and transient voltage issues and possible overloading conditions. This paper aims to verify the overvoltage and overloading issues caused by DG at high penetration levels. A typical utility distribution feeder was selected using cluster analysis for simulations. DG at various penetration levels was interconnected at 4 different locations on the feeder. Summer Peak (SP), Partial Peak (PP) and Winter Peak (WP) loading conditions have been studied. Solar Photo-Voltaic (PV) is used as DG for all simulations. Static VAr Compensators (SVC) and Smart Inverters (SI) and their mitigating effects have been reported as possible solutions. Acceptable DG penetration levels have been proposed depending on DG locations and associated voltage or overloading issues. Two special cases, one involving simultaneous high and low voltage conditions and the other related to high voltages at multiple locations have also been studied and reported.