IET Generation, Transmission & Distribution
Volume 7, Issue 11, November 2013
Volumes & issues:
Volume 7, Issue 11
November 2013
Influence of sympathetic inrush on voltage dips caused by transformer energisation
- Author(s): Jinsheng Peng ; Haiyu Li ; Zhongdong Wang ; Foroozan Ghassemi ; Paul Jarman
- Source: IET Generation, Transmission & Distribution, Volume 7, Issue 11, p. 1173 –1184
- DOI: 10.1049/iet-gtd.2012.0166
- Type: Article
- + Show details - Hide details
-
p.
1173
–1184
(12)
Energising a transformer with other adjacent transformers in service may induce sympathetic inrush that could lead to long duration voltage dips. This study addresses this issue through analysing voltage dip events observed on a 400/132 kV grid when energisations of several generator step-up transformers were performed. With the help of a number of field measurements of voltage dips involving sympathetic inrush, a detailed network model in alternative transients program/electromagnetic transients program has been developed and validated. Based on the network model, comprehensive simulation studies have been performed. In addition, because of the nature of multiple controlling parameters, sensitivity assessment has been carried out to identify the key influential parameters. It is found that the sympathetic inrush, although does not affect voltage dip magnitude, can prolong voltage dip duration by 143% under the worst energisation condition. The sympathetic inrush occurring in substation transformers gives rise to a network-wide sympathetic interaction, resulting in further prolonged voltage dips on the 132 kV grid. Finally, it is proven that application of static var compensator is able to speed up the voltage dip recovery.
New model for overhead lossy multiconductor transmission lines
- Author(s): Juan C. Escamilla ; Pablo Moreno ; Pablo Gómez
- Source: IET Generation, Transmission & Distribution, Volume 7, Issue 11, p. 1185 –1193
- DOI: 10.1049/iet-gtd.2012.0284
- Type: Article
- + Show details - Hide details
-
p.
1185
–1193
(9)
A new model for time-domain electromagnetic transient analysis of overhead multiconductor transmission lines with frequency-dependent electrical parameters is presented. The model is based on the method of characteristics, which has been used before by means of the application of finite difference schemes. Conversely to the regular method of characteristics, the model presented here does not require the spatial discretisation along the line. Also, the frequency dependence of the electrical parameters is included by means of a transient resistance matrix. To validate the model, the results are compared to those from a frequency-domain method, the alternative transients program/electromagnetic transients program (ATP/EMTP) and the electromagnetic transients program-restructured version (EMTP-RV).
Revisiting the power flow problem based on a mixed complementarity formulation approach
- Author(s): Mehrdad Pirnia ; Claudio A. Cañizares ; Kankar Bhattacharya
- Source: IET Generation, Transmission & Distribution, Volume 7, Issue 11, p. 1194 –1201
- DOI: 10.1049/iet-gtd.2012.0592
- Type: Article
- + Show details - Hide details
-
p.
1194
–1201
(8)
A novel optimisation-based model of the power flow (PF) problem is proposed using complementarity conditions to properly represent generator bus voltage controls, including reactive power limits and voltage recovery processes. This model is then used to prove that the Newton–Raphson (NR) solution method for solving the PF problem is basically a step of the generalised reduced gradient algorithm applied to the proposed optimisation problem. To test the accuracy, flexibility and the numerical robustness of the proposed model, the IEEE 14-bus, 30-bus, 57-bus, 118-bus and 300-bus test systems and large real 1211-bus and 2975-bus systems are used, benchmarking the results of the proposed PF model against the standard NR method. It is shown that the proposed model yields adequate solutions, even in the case when the NR method fails to converge.
Maximum undergrounding degree of HV subtransmission networks as dictated by unscheduled power flows
- Author(s): Stefano Lauria and Francesco Palone
- Source: IET Generation, Transmission & Distribution, Volume 7, Issue 11, p. 1202 –1209
- DOI: 10.1049/iet-gtd.2012.0295
- Type: Article
- + Show details - Hide details
-
p.
1202
–1209
(8)
Meshed HV subtransmission networks are subject to undesirable parallel (unscheduled) active power flows from the EHV system. The phenomenon is worsened by conversion of HV overhead lines to underground cables (UGCs), which increases parallel flows through the HV network because of the attendant reduction in HV line reactance; the effect increase with network extension and are compounded by UGC charging power. The study deals with the assessment of the maximum undergrounding degree for a given subtransmission network. An analytical formulation of maximum HV line extension length as a function of EHV power flow and undergrounding degree is given; optimum UGC shunt compensation requirements are evaluated. Application to a typical 150 kV–50 Hz network is presented, showing a very good agreement with power flow simulation. In particular, the case study evidences that complete undergrounding of the HV network is possible if line length is under 50 km; the proposed shunt compensation effectively raises this limit to 70 km.
Outer-approximation method for security constrained unit commitment
- Author(s): Juan P. Ruiz ; Jianhui Wang ; Cong Liu ; Gengyang Sun
- Source: IET Generation, Transmission & Distribution, Volume 7, Issue 11, p. 1210 –1218
- DOI: 10.1049/iet-gtd.2012.0311
- Type: Article
- + Show details - Hide details
-
p.
1210
–1218
(9)
In this study, the authors present an outer-approximation method to solve the mixed-integer non-linear security constrained unit commitment problem. The main idea lies in solving sequentially a set of mixed-integer linear programs (MILP) to obtain lower bounds (LBs) of the global optimum and perform function evaluations on the incumbent solution of the MILP problem to obtain upper bounds (UBs). The algorithm stops when the LB and UB are sufficiently close. The authors also present a heuristic method that builds on the proposed framework to improve the quality of the solution obtained from the piecewise linear method. The authors show through a set of numerical examples the performance of this approach.
Individual-phase decoupled P–Q control of three-phase voltage source converter
- Author(s): Seyed Mahdi Fazeli ; Hew Wooi Ping ; Nasrudin Bin Abd Rahim ; Boon Teck Ooi
- Source: IET Generation, Transmission & Distribution, Volume 7, Issue 11, p. 1219 –1228
- DOI: 10.1049/iet-gtd.2012.0417
- Type: Article
- + Show details - Hide details
-
p.
1219
–1228
(10)
Individual-phase control has six control degrees of freedom: P- and Q-control for each phase. The six control degrees are applied to a distribution static compensator (D-STATCOM): (i) to support the AC voltages against voltage droop arising from weak transmission lines; (ii) to balance the active and reactive powers at the sending-end although the three-phase load is unbalanced; and (iii) to balance the voltages across the unbalanced load. A second contribution is a method to suppress DC voltage imbalance of D-STATCOM capacitors caused by zero sequence transients. Proof of concept is by simulations. The simulation tool used is EMTDC-PSAD.
Modelling and analysis of current and potential distribution paths for grounding devices
- Author(s): Yury Chikarov ; Tek Tjing Lie ; Nirmal Kumar C. Nair
- Source: IET Generation, Transmission & Distribution, Volume 7, Issue 11, p. 1229 –1243
- DOI: 10.1049/iet-gtd.2012.0510
- Type: Article
- + Show details - Hide details
-
p.
1229
–1243
(15)
This study proposes and develops a mathematical formulation that helps to clearly understand the current and voltage distribution in the damaged and physically integrated horizontal elements of grounding systems. This realistic mathematical model of the grounding device with damaged elements will help to estimate the current and voltage distribution at the generating substation and will improve safety conditions for staff and equipment and reducing damages associated with equipment failures. It will also provide the basis for developing novel grounding integrity detection techniques.
Implementation of distribution static compensator for power quality enhancement using learning vector quantisation
- Author(s): Sabha Raj Arya and Bhim Singh
- Source: IET Generation, Transmission & Distribution, Volume 7, Issue 11, p. 1244 –1252
- DOI: 10.1049/iet-gtd.2012.0689
- Type: Article
- + Show details - Hide details
-
p.
1244
–1252
(9)
An implementation of a three-phase distribution static compensator (DSTATCOM) using learning vector quantisation (LVQ) control algorithm is presented for compensation of loads in a distribution system. The DSTATCOM is used for harmonics elimination, load balancing and reactive power compensation with self-supporting dc bus in distribution system. The LVQ-based control algorithm is used for extraction of fundamental weighted values of active and reactive power components of load currents which are required for estimation of reference supply currents. It is based on a double supervisory system where each weighted vector is modified by input weights. The input weights are trained outputs of the first stage learning weights. It is needed for accurate estimation of compensation currents from the voltage source converter (VSC) used in DSTATCOM. A prototype of the VSC-based DSTATCOM is developed using a digital signal processor to validate the proposed control approach and its performance is studied under a steady state and dynamic conditions. The performance of the DSTATCOM is found satisfactory with the proposed control algorithm under linear and non-linear loads which are commonly used in the distribution system. The dc bus voltage of the VSC of DSTATCOM has a negligible effect on varying loads.
Cobweb theory-based generation maintenance coordination in restructured power systems
- Author(s): Mohammad Amin Latify ; Hossein Seifi ; Habib Rajabi Mashhadi ; Mohammad Kazem Sheikh-El-Eslami
- Source: IET Generation, Transmission & Distribution, Volume 7, Issue 11, p. 1253 –1262
- DOI: 10.1049/iet-gtd.2012.0370
- Type: Article
- + Show details - Hide details
-
p.
1253
–1262
(10)
A cobweb theory-based maintenance coordination algorithm is proposed in this study. It is an iterative process in which, initially, the independent market operator (IMO) declares the interval electricity price for the period of concern. The generation companies (GenCos) would then provide the independent system operator (ISO) and the IMO with their own maintenance proposals; based on their own objectives and constraints. The ISO would evaluate the impact of the maintenance proposals on the reliability indices and assign some penalties/rewards to the GenCos; in proportion to their contributions in reliability index violation from a desirable level. On the other hand, the IMO would declare the new electricity prices, considering the new maintenance proposals. These two signals would be used by the GenCos to review and modify their maintenance proposals. The procedure is repeated until an equilibrium point is reached. For convergence assurance, a memory rate is introduced by which the GenCos earlier experiences in providing the ISO with the maintenance proposals are, somehow, taken into account. The capabilities of the proposed algorithm are assessed and evaluated on IEEE reliability test system.
Coordination of storage and generation in power system frequency control using an H∞ approach
- Author(s): Dinghuan Zhu and Gabriela Hug-Glanzmann
- Source: IET Generation, Transmission & Distribution, Volume 7, Issue 11, p. 1263 –1271
- DOI: 10.1049/iet-gtd.2012.0522
- Type: Article
- + Show details - Hide details
-
p.
1263
–1271
(9)
This study proposes a novel H∞ -based approach called advanced frequency control (AFC) to integrate storage into frequency control. The objective is to split the task of balancing frequency deviations introduced by renewable energy source (RES) and load variations according to the capabilities of storage and generators. Hence, via frequency dependent weighting functions, a so-called frequency separation objective is achieved: the conventional generators mainly balance the low-frequency components of the RES and load variations while the energy storage devices compensate the high-frequency components. First, a state-space structure-preserving model of the power system is derived, which is needed for the design of the controller. In order to enable the controller design for storage devices located at buses with no generators, a model for the frequency at such a bus is developed. Then, AFC controllers are synthesised through decentralised static output feedback to reduce the complexity in the practical implementation of such controllers. An existing linear matrix inequality algorithm is improved and employed to solve the involved H∞ problem. Finally, the WECC 9-bus test system is used to verify the performance of the AFC design.
Solid-state transient limiter for capacitor bank switching transients
- Author(s): Teymoor Ghanbari ; Ebrahim Farjah ; Amir Zandnia
- Source: IET Generation, Transmission & Distribution, Volume 7, Issue 11, p. 1272 –1277
- DOI: 10.1049/iet-gtd.2012.0495
- Type: Article
- + Show details - Hide details
-
p.
1272
–1277
(6)
Transient overvoltage and inrush current are two major transient phenomena which occur because of capacitor switching. In addition to power quality degradation, these transients lead to shortening the lifetime of the capacitor and switching device. In order to reduce these transients, a solid-state capacitor switching transient limiter (SSCSTL) is proposed in this study. The proposed SSCSTL has two operation modes: limiting mode and bypass mode. During the capacitor energising, a DC reactor and a varistor suppress inrush current and transient overvoltage, respectively. During the steady-state mode, the DC reactor is bypassed by a thyristor, so the SSCSTL acts as short-circuit and has no considerable effect on the circuit. The thyristor is triggered by using a new simple structure auto-triggering technique in normal condition. The proposed SSCSTL with a very simple structure as well as fast and reliable performance is an efficient solution to assure the capacitor switching without any transient overvoltage and inrush current. A prototype single-phase SSCSTL is simulated by electromagnetic transient program and tested. The simulation and experiment results show that the proposed SSCSTL considerably reduces the inrush current and transient overvoltage during switching of the capacitor.
Decoupled recursive-least-squares technique for extraction of power system synchronised phasors under fault conditions
- Author(s): Iman Sadinezhad and Vassilios G. Agelidis
- Source: IET Generation, Transmission & Distribution, Volume 7, Issue 11, p. 1278 –1288
- DOI: 10.1049/iet-gtd.2012.0235
- Type: Article
- + Show details - Hide details
-
p.
1278
–1288
(11)
This study presents application of the decoupled recursive-least-squares (DRLS) technique for extraction of power system synchronised phasors under fault conditions. The proposed DRLS technique demonstrates robust performance during faults, subsequent operation of circuit breakers and reclosing of a transmission line. The proposed DRLS technique also significantly reduces the computational burden of the conventional RLS technique for implementation on digital signal processors (DSPs). The modification of decomposition of single-phase into orthogonal components frequency estimation technique for three-phase power systems is also applied to adapt the DRLS estimation with frequency drifts. The performance of the proposed DRLS technique has been evaluated through presetting selected simulation results in DigSilent Power Factory and MATLAB-Simulink. DSP implementation of the DRLS technique also confirms considerable computational efficiency improvement when compared with that of the conventional RLS technique.
Improved model for tap-changing transformer
- Author(s): Carlos Aparecido Ferreira and Ricardo Bernardo Prada
- Source: IET Generation, Transmission & Distribution, Volume 7, Issue 11, p. 1289 –1295
- DOI: 10.1049/iet-gtd.2012.0466
- Type: Article
- + Show details - Hide details
-
p.
1289
–1295
(7)
The model for tap-changing transformers currently in widespread use consists of an impedance, measured in a short-circuit test with a nominal tap, in series with an ideal transformer. The use of this model in voltage stability studies leads to qualitatively incorrect results. For demonstration purpose, a small circuit and the concepts of maximum load, equivalent load impedance and voltage control effects are used. An improved model that takes into account laboratory results, circuit laws and voltage stability theory is proposed. Using IEEE test systems, different results are shown for the conventional and proposed models.
Use of local bus measurements for operational planning of a power system
- Author(s): Durlav Hazarika ; Bani Kanta Talukdar ; Ranjay Das
- Source: IET Generation, Transmission & Distribution, Volume 7, Issue 11, p. 1296 –1309
- DOI: 10.1049/iet-gtd.2012.0521
- Type: Article
- + Show details - Hide details
-
p.
1296
–1309
(14)
This study describes a method to prepare operational planning of a power system using the measurements of bus variables. For this purpose, voltage and current phasors of a target bus have to be measured for two consecutive time instances. These measurements are then used to determine the Thevenin's equivalent voltage and impedance of the system. The Thevenin's equivalent voltage, impedance and bus voltage of the target bus are used to derive sensitivity relations for change in real and reactive powers with respect to change in the bus voltage of the target bus. The sensitivity relations are utilised in the decision-making process, during operational planning of a power system.
Interoperability of voltage source converters in dc grids
- Author(s): Grain Philip Adam ; Stephen Jon Finney ; Barry Williams
- Source: IET Generation, Transmission & Distribution, Volume 7, Issue 11, p. 1310 –1317
- DOI: 10.1049/iet-gtd.2012.0768
- Type: Article
- + Show details - Hide details
-
p.
1310
–1317
(8)
This study examines the possibility of operating different voltage source converter topologies in high-voltage direct current grids. The investigation is motivated by growing concern from the utility companies and transmission system operators regarding the compatibility of these converters, especially the behaviour of resultant multi-vendor dc grids during ac and dc network faults. In an attempt to establish the credibility of the expressed concerns, the transient response of illustrative multi-vendor six-terminal dc grids that consists of four two-level converters, a two-switch modular converter and a H-bridge modular converter are examined during ac and dc network faults. The main results obtained and observations drawn are highlighted and discussed.
Robust transmission system expansion considering planning uncertainties
- Author(s): Behnam Alizadeh ; Shahab Dehghan ; Nima Amjady ; Shahram Jadid ; Ahad Kazemi
- Source: IET Generation, Transmission & Distribution, Volume 7, Issue 11, p. 1318 –1331
- DOI: 10.1049/iet-gtd.2012.0137
- Type: Article
- + Show details - Hide details
-
p.
1318
–1331
(14)
This study presents a novel approach for transmission expansion planning (TEP) addressing the inherent uncertainties associated with the estimated investment costs of candidate transmission lines and the forecasted electricity demands during long-term planning horizon. The proposed TEP approach employs a renovated mixed integer linear programming formulation holding the optimality and low computation burden of linear modelling techniques. The above mentioned uncertainties are encountered through robust optimisation methodology enabling the system's planner to assess different levels of uncertainty and conservation throughout planning horizon. The proposed robust TEP procedure is successfully applied to Garver 6-bus, IEEE 30-bus and IEEE 118-bus test systems. Simulation results demonstrate that the uncertainty level of investment costs and electricity demands escalates the total expansion costs based on the scale of power system.
Extended smart meters-based remote detection method for illegal electricity usage
- Author(s): Byambasuren Bat-Erdene ; Bumjoo Lee ; Min-Young Kim ; Tae Hong Ahn ; Donghan Kim
- Source: IET Generation, Transmission & Distribution, Volume 7, Issue 11, p. 1332 –1343
- DOI: 10.1049/iet-gtd.2012.0287
- Type: Article
- + Show details - Hide details
-
p.
1332
–1343
(12)
Power delivery systems that use power lines can communicate with other electrical systems, monitor the quality of electrical energy and provide an economical solution for automatic meter reading (AMR). Energy meters can be connected to a low-voltage power system by power line carriers for all consumers. Illegal electricity usage in the power delivery system can be easily detected if AMR is installed in the system, which consists of a terminal smart meter (TSM) and a gateway smart meter (GSM). This study proposes a novel remote detection method for illegal electricity usage that uses both TSM and GSM, where the TSM and the GSM are installed on the power system of each consumer and on the node of the power system feeder, respectively. TSM and GSM simultaneously disconnect an electrical source for a very short period of time. After this, the proposed detection method sends a low-voltage signal with a high frequency from the TSM to the GSM during the time of disconnection. Once the signal has passed, the proposed detection method detects illegal electricity usage by measuring the amount of time it was disconnected. This study presents the structure of the proposed detection method as well as the mathematical model, proof, simulation and experimental results.
Switching function analysis of half- and full-bridge modular multi-level converters for HVDC applications
- Author(s): Sawata R. Deore ; Pranav B. Darji ; Anil M. Kulkarni
- Source: IET Generation, Transmission & Distribution, Volume 7, Issue 11, p. 1344 –1356
- DOI: 10.1049/iet-gtd.2012.0034
- Type: Article
- + Show details - Hide details
-
p.
1344
–1356
(13)
This study presents a theoretical analysis of half- and full-bridge modular multi-level converters for HVDC transmission applications. The constraints and the degrees of freedom in the choice of switching functions, and the harmonic content of the sum and difference of arm voltages and currents, are highlighted by the analysis. The authors prove that under balanced switching conditions, dc and even harmonic components are absent from the difference variables and odd harmonics are absent from the sum variables, whereas the pole voltages are free from harmonics. Using an energy function approach, it is shown that the sorting strategy for module voltage balancing is stable and practically independent of the dynamics of the rest of the system. The module voltages settle down to a band around the average value because of the finite switching frequency, for which an upper bound is provided.
Most viewed content
Most cited content for this Journal
-
Retracted: Energy storage system and demand response program effects on stochastic energy procurement of large consumers considering renewable generation
- Author(s): Habib Allah Aalami and Sayyad Nojavan
- Type: Article
-
Grey wolf optimisation for optimal sizing of battery energy storage device to minimise operation cost of microgrid
- Author(s): Sharmistha Sharma ; Subhadeep Bhattacharjee ; Aniruddha Bhattacharya
- Type: Article
-
Non-cooperative game theory based energy management systems for energy district in the retail market considering DER uncertainties
- Author(s): Mousa Marzband ; Masoumeh Javadi ; José Luis Domínguez-García ; Maziar Mirhosseini Moghaddam
- Type: Article
-
Optimal capacitor placement in distribution systems for power loss reduction and voltage profile improvement
- Author(s): Adel Ali Abou El-Ela ; Ragab A. El-Sehiemy ; Abdel-Mohsen Kinawy ; Mohamed Taha Mouwafi
- Type: Article
-
Comparative study on the performance of many-objective and single-objective optimisation algorithms in tuning load frequency controllers of multi-area power systems
- Author(s): Masoud Hajiakbari Fini ; Gholam Reza Yousefi ; Hassan Haes Alhelou
- Type: Article