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To meet the global warming, renewable energy sources like wind, solar and biomass generations are dramatically increasing. Cogeneration systems are also ever-growing to save consumers' energy costs among factories, buildings and homes where lots of thermal loads are expected. According to these dispersed generators growth, their negative impacts to commercial power systems quality become non-negligible, because their unstable output causes network voltage and frequency fluctuation. Micro-grid technology comes to the front to solve the problem and many demonstrative field tests are now going all over the world. This paper presents the control paradigm and its application to Hachinohe micro-gird project, especially focusing on the power quality at isolated operation on which strict condition is imposed.

A new circuit of parallel-type voltage sag compensator is proposed in this paper. The proposed voltage sag compensator can reduce the necessary capacity of the energy storage capacitor for compensation by boost-type power factor correction rectifier charging the capacitor during a voltage sag. As a result the proposed system can reduce the size and maintenance of the apparatus. Copyright © 2004 Wiley Periodicals, Inc. This paper shows the principle and control system of the proposed circuit. Compensation characteristics were demonstrated by simulation and experiment. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 159(2): 19–33, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20261

This paper presents high-order harmonic resonance phenomena of voltage-sourced converters (VSC). When a voltage-sourced converter is connected to a power system with cables, there is a possibility that minute high-order harmonic voltages of a voltage-sourced converter are magnified by a series resonance and a parallel resonance, and high-order harmonic resonance phenomena are determined by this study. The cause of high-order harmonic resonance phenomena is investigated and elucidated by the analysis using EMTP. In addition, it is verified that high-order harmonic resonance phenomena occur as a practical matter. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 150(3): 26–35, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20054

This paper presents high-order harmonic resonance phenomena of voltage sourced converter (VSC). When a voltage sourced converter is connected to power system with cables, there is possibility that minute high-order harmonic voltages of a voltage sourced converter are magnified by a series resonance and a parallel resonance, and high-order harmonic resonance phenomena are found by this study. The cause of high-order harmonic resonance phenomena is investigated and figured out by the analysis using EMTP. In addition, it is verified that high-order harmonic resonance phenomena occur as a practical matter.

This paper presents a new concept for back-to-back (BTB) dc systems. The main feature of the proposed BTB is referred to as “massively parallel.” This massively parallel BTB system consists of a number of small or mediumcapacity inverter units that are connected in parallel. The concept of transmission power control using the massively parallel BTB is investigated using MATLAB for a case where a fault occurs. In addition, a method for modeling the proposed BTB in EMTP is investigated. The work presented in this paper shows that the proposed BTB system is very promising for large power system applications because the losses of the system are very small compared to conventional BTB using VSC (voltage source converter). The massively parallel BTB can keep operating even if an inverter unit fails, thus improving overall power transmission capability. © 2001 Scripta Technica, Electr Eng Jpn, 138(3): 34–42, 2002

Georgia Transmission Corporation (GTC) commissioned the Barrow County Static Var Compensator (SVC) with a continuous rating of 0 to +260 Mvar in June of 2008. This paper presents the northern Metro Atlanta Georgia area transmission system, the requirements for voltage and var support, the dynamic performance study used to verify performance of the SVC, and provides an overview of the SVC design and control strategy, including the SVC's response to an actual power system disturbance. The Barrow County SVC is connected to the 230 kV bus at the Winder Primary Substation to effectively manage the exposure to fault-induced delayed voltage recovery (FIDVR), where the system voltage remains low (≪80%) for several seconds following a disturbance and potentially leading to voltage collapse. The SVC configuration includes two thyristor-switched capacitors for rapid insertion of reactive power following a disturbance to decrease voltage recovery time and control the system's dynamic performance.

Southern California Edison (SCE) commissioned the rector static Var compensator (SVC) with a continuous rating of -120 to +200 Mvar in June of 2007. This paper presents the big creek corridor portion of the San Joaquin Valley transmission system, the requirements for voltage and var support, the planning and dynamic performance studies used in rating and verifying performance of the SVC, and provides an overview of the SVC design and control strategy. The rector SVC is connected to the 230 kV bus at SCE's Rector substation for dynamic var support to meet the transient voltage dip reliability requirements of the Western Electricity Coordinating Council (WECC), and to enhance local and remote steady-state voltage control. The SVC configuration includes six thyristor valve controlled/switched branches, six harmonic filter branches, and employs coordinated control of a local 230 kV mechanically switched capacitor (MSC) bank to ensure sufficient dynamic vars remain available for system disturbances.

PacifiCorp commissioned the St. George static VAr system (SVS) with a continuous rating of -35 to +100 MVar (transient rating -70 to +278 MVar) in June of 2006. This paper presents the Southwest Utah area transmission system, the requirements for voltage support, the planning and dynamic performance studies used in rating and verifying performance of the SVS, and provides an overview of the design and coordinated control strategy. An overview of the SVS stability model with integrated "smooth" and "stepped" susceptance control is also discussed.The St. George SVS is connected to the 138 kV bus of the St. George substation to enhance voltage control and dynamic VAr support for major disturbances in the Southwest Utah 138 kV and 345 kV transmission systems. The SVS coordinated control strategy employs local and remote shunt reactive devices to reduce SVS reactive steady-state output and to regulate the voltage at the local St. George 138 kV bus and at the remote Red Butte 138/345 kV substation

Appropriately modeling load characteristics is important for power system analysis, in particular for voltage instability phenomena. Load modeling is becoming ever more important with the increasing penetration of power electronic based loads. In order to improve the process and accuracy of power system planning and to be able to make rational and economical decisions based on studies, appropriate load models for planning studies are critical. Thus, to improve load modeling, a study based on actual field data was carried out and is described in this paper.