Voltage versus VAr/power-factor regulation on synchronous generators
ABSTRACT When paralleled to the utility bus, synchronous generators can be controlled using either terminal voltage or VAr/power factor (PF) control. Selection is dependent upon the size of the generator and the stiffness of the connecting utility bus. For large generators where the kVA is significant, these machines are usually terminal voltage regulated and dictate the system's bus voltage. When smaller terminal voltage regulated generators are synchronized to a stiff utility bus, the system voltage will not change as the smaller generator shares reactive loading. However, if the system voltage changes significantly, the smaller generator, with its continuous acting terminal voltage regulator, will attempt to maintain the voltage set point. As the voltage regulator follows its characteristic curve, it may cause either over or under excitation of the smaller generator. Excessive system voltage may cause a small generator to lose synchronizing torque, while low system voltage may cause excessive heating on the generator or excessive overcurrent operation of the excitation system. Maintaining a constant reactive load on the smaller generating unit can reduce the generator field current variations and, thus, reduce the maintenance of the collector rings and brushes. This paper illustrates the effect of changing system bus voltage on small generators utilizing voltage versus VAr/PF regulation.
- SourceAvailable from: Mostafa Eidiani
- "ﺑﺎ اﻣﺎ ﻳ اﮔ ﻛﻪ داﺷﺖ ﺗﻮﺟﻪ ﺪ ا از ﺮ ﻳ روش ﻦ ﺑﺮا ﺗﻨﻬﺎ ي ﺟﺒﺮاﻧﺴﺎز ي ﺷـﻮد اﺳﺘﻔﺎده ﻣﻘﺎ در ﻳ ﺟﺒﺮاﻧﺴـﺎز ﺑـﺎ ﺴـﻪ ي ﺧـﺎزﻧ ﻲ ﻧﺎﭘﺎ ﻳـ ﭘ و ﺪارﺗﺮ ﺮﻫﺰ ﻳ ﺑـﻮد ﺧﻮاﻫـﺪ ﺗـﺮ ﻨـﻪ .     "
Conference Paper: ارائه يك روش عصبي هوشمند جهت تصحيح ضريب توان در يك سيستم قدرتاولين همايش منطقه اي مهندسي برق, Tehran, Iran; 01/2011
[Show abstract] [Hide abstract]
- "However, when operated in the voltage control mode, it may cause either over or under excitation of the small generator as it will attempt to maintain the voltage at a set point with its continuously acting terminal voltage regulator . Also, an excessive reactive current may result in overload or loss of generator synchronism . According to , small generators' operation at the VAr/power factor control mode is justifiable. "
ABSTRACT: Islanding operation of distribution systems with distributed generations (DG) is becoming a viable option for economical and technical reasons. However, there are various issues to be resolved before it can be a reality. One of the main issues is control of the DG. Control strategies, that may work fine while a DG is connected to a grid, might not work as desired while it is islanded and vise versa. This paper presents a strategy to operate distribution systems with a small gas turbine generator (GTG), which is capable of supplying local loads, in both islanding and grid connected conditions. Separate strategies are used to control the GTG while it is connected to the grid and while it is islanded. Switching between the control strategies is achieved through a state detection algorithm that includes islanding and grid re-connection detections. An existing islanding detection technique has been used and a grid re-connection detection algorithm has been developed. Simulation results show that the proposed method is effective in operating GTG optimally while it is either connected to the grid or islanded.Transmission and Distribution Conference and Exposition, 2010 IEEE PES; 05/2010
[Show abstract] [Hide abstract]
- "The capacity at each site is a decision variable in the problem, as opposed to a fixed parameter. As is common with DG , the generators are assumed to be run in constant power factor mode (i.e. with no voltage control), although alternative operational modes are possible. The only customised constraint in this model before security constraints are added is the Kirchhoff current law, where the capacity of any DG expansion site must be added to the net power injection at each bus. "
ABSTRACT: The capacity of distributed generation (DG) connected in distribution networks is increasing, largely as part of the drive to connect renewable energy sources. The voltage step change that occurs on the sudden disconnection of a distributed generator is one of the areas of concern for distribution network operators in determining whether DG can be connected, although there are differences in utility practice in applying limits. To explore how voltage step limits influence the amount of DG that can be connected within a distribution network, voltage step constraints have been incorporated within an established optimal power flow (OPF) based method for determining the capacity of the network to accommodate DG. The analysis shows that strict voltage step constraints have a more significant impact on ability of the network to accommodate DG than placing the same bound on voltage rise. Further, it demonstrates that progressively wider step change limits deliver a significant benefit in enabling greater amounts of DG to connect.IEEE Transactions on Power Systems 03/2010; 25(1-25):296 - 304. DOI:10.1109/TPWRS.2009.2030424 · 2.81 Impact Factor