The submitted paper describes travelling wave fault location algorithm used for high voltage (HV) lines, based on wavelet transform, which was implemented in a prototype device and tested in laboratory conditions. Hardware and software parts of the fault locator, testing methodology and results are included in this paper.
This document presents the work done in the ReactivHome project for the development of algorithms for automatic identification of electrical equipment and their parameters by using the electricity consumption signal. Several employees of the CEA-INES were asked to perform measurements on their own electrical appliances. The library of measure will be used as reference for identification phase. Several indicators will be determined by expert as cycle, duration, power consumption. In this phase, the fuzzy logic is used for applying these indicators calculated on the electrical measurements. In order to build a simple power consumption of household appliance, a parametric modelling is used. This identification mechanism was integrated in ReactivHome system and functionally.
Phasor Measurement Unit (PMU) performances are the basis for successful implementation of PMUs in power system security monitoring and control, and they are greatly affected by systematic errors caused by phasor estimation algorithm. In this paper, the Normal-Fitting Index (NFI) is proposed to identify PMU systematic errors in probability and statistics way. It reflects influences of systematic errors on PMU measurements. Besides, Weighted Least Square (WLS) curve-fitting method is applied here to identify systematic errors due to Discrete Fourier Transform (DFT) via analyzing the features of phasor estimations under dynamic conditions. Several PMUs are tested in laboratory and the results are used for analysis by the two methods above, which reveal that problems exist in PMU dynamic performances.
This paper presents the results of transient stability analysis in power system with high levels of photovoltaic (PV) penetration. In response to an increase of PV capacity, the capacity of conventional synchronous generator needs to be reduced relatively. This leads to the lower system inertia and the higher generator reactance, and hence the power system transient stability may negatively be affected. In particular, the impact on the transient stability may become more serious when the considerable amounts of PV systems are disconnected simultaneously during voltage sag. In this work, the potential impact of significant PV penetration on the transient stability is assessed by a numerical simulation using PSCAD/EMTDC.
With the development of smart grid, power quality is becoming a more important issue in distribution network. Distribution system could decide, or be obliged by users, to supply their users with different power quality levels at different prices. This paper presents a novel unified power quality conditioner configuration - Multiple Terminal Unified Power Quality conditioned (MT-UPQC) which is consisted of one series active filter and multiple shunt active filters. The MT-UPQC can compensate for voltage quality problems, harmonic currents fully and reactive current differently according to the requirements of users. The functions of the MT-UPQC as well as the adopted control algorithm are illustrated in the generalized way. A three terminal-UPQC (3T-UPQC) is built up on the PSCAD/EMTDC platform to undergo the detailed design, simulation and verification. The simulation result shows that the proposed approach is effective and flexible.
This work develops a microgrid stability controller to support microgrid switching its operation mode and provide DG units in the microgrid with the additional functionality of working in island mode without changing their control strategies. When microgrid works in grid connected mode, microgrid stability controller compensate power variation and reduces power fluctuation. When the main grid is not available, microgrid operates in island mode, microgrid stability controller provide output voltage and frequency reference for DG units. Its operation is analyzed by studying its control strategies, islanding detection techniques and black box arc model of circuit breaker at the Point of Common Coupling (PCC). Furthermore this paper analyzes its transient characteristics based on the dynamic performance of the microgrid during a fault in distribution network. Simulation and experimental results validates the feasibility of the microgrid stability controller.
Large scale wind power has impact on the power system's security and stability. For a large scale wind turbines tripping off accident happening in the region of Guyuan in North China, this paper explains the accident development process, analyzes the main reason for the cascading wind turbines tripping off, builds the simulation model according to the actual data of the North China Grid and the wind power integration system, and reconstructs the accident process based on the simulation, discusses the countermeasures to avoid this kind of cascading accident.
This paper researches economic operation of wind-PV-ES hybrid micro-grid. Firstly, operational strategy of micro-grid and its energy system are proposed. Then the economic operation optimization model is built and particle swarm optimization algorithm is simulated with MATLAB. Based on a practical wind-PV-ES hybrid micro-grid, the simulated results give the optimization cost according to the load and wind power/PV output prediction under kinds of typical weather condition. The results comparison shows that the proposed optimization method is useful to reduce operational cost.
The low-voltage microgrid, a typical three phase asymmetric system, usually consists of many distributed generations (DGs) and loads, the injection power of them are mostly uncertain. In this paper, a novel method to calculate the probabilistic load flow of low-voltage microgrid is proposed. The three-phase model of each component in the network is established, then the time series probability models are built, respectively, due to the time variations of load, and the output power of DGs, such as photovoltaic and wind power. Then the algorithm called “fixed-point iteration” is adopted to solve the basic asymmetric load flow, and Monte Carlo method is used to simulate probability. Experimental results on IEEE 123 node test feeder case show that the proposed method can effectively solve the hard problems in the low-voltage microgrid, such as unbalanced load flow, non-all-phase operation and uncertain injection power.
Climate change has become one of the most serious problems nowadays. Electric power industry, as a major emitter of greenhouse gas CO2, has been demanded to develop in an environmental friendly way. This paper presents economic dispatch model considering carbon reduction policies, as well as basic data analysis to determine the impact of policy-guided carbon emission reduction strategies on power system operation and dispatch. Carbon reduction mechanisms are simulated and discussed in different case studies. By analyzing the effect of different carbon reduction policies, this model can be used to help regulators with decision making and system operators with economical and environmental operation.
Wind power short-term prediction method generally depends on the meteorological data at present. This paper proposed time series power prediction method which is based on multi-scale tuple matching and can predict wind power well by making full use of historical data without affecting the computational efficiency to predict wind power on the occasion where power series can be obtained but the meteorological data not. This method used the multi-scale tuple matching technology to search target sequence quickly and accurately. Then calculate some characteristic parameters through the comparison analysis of the search results and use historical data and the characteristic parameters to predict future output. Simulation studies are carried to test the performance of this method using the data obtained from a wind farm in Northwest China. Results show that this method can predict power effectively. It is characterized by independence of meteorological information, cost saving, high prediction precision and strong real-time compared with traditional method.
The effects that wind power brought on power system protective configuration is analyzed, and the protective allocation of all electrical components when doubly-fed wind turbines connected to power grid is elaborated. Based on analysis of network connection in China, the basic mode of grid framework change during faults has been analyzed and concrete criteria for corresponding fault modes are put forward to implement fast sensing and diagnosis of faults. Taking the characteristics of protective action for wind generators into account, the action mode of protective relaying is constructed. Finally, the effectiveness of the proposed method is verified by an actual fault case in China.
The increase of integration of distributed generations (DG) requires the network management to be more active. This paper investigates an active voltage control approach by coordinating the reactive power of DG and the operation of onload tap changer (OLTC). A sensitivity model of the V-Q coupling in distribution systems is used in the optimization of the coordinated voltage regulation. The performance of voltage control has been verified and compared with the conventional OLTC control. The results show that this approach is very promising.
Conventional overcurrent protection settings are fixed to detect faults. Power system operation mode varies while the settings of protection devices remain constant. As a result, overcurrent protection has a small protection range and a long operating time because it is incapable of adjusting its setting online. Wide Area Measurements System (WAMS) provides synchronized and real time data which can be utilized in new protection devices. This paper proposes a novel online setting scheme which utilizes online system data to calculate real-time system operation mode. Based on the real-time operation mode, real-time fault current is calculated before fault occurring. Settings of the protection devices are by this means adjusted in real time to expand the protection area and shorten the operating time. The calculation is expanded from single source model to multi-source with Π model. In addition, interval time of settings adjustment Tchange is proposed and calculated by using hyperbolic function model. Based on this method, power system real-time operation condition can be better monitored and the real-time short circuit current can be obtained to improve protection performance.
This work is related to protection systems on MV distribution networks. Most of these grids are currently protected by a single relay installed at the beginning of each feeder. The Smart Grids transition is more and more essential for the future grids willing to attain a higher reliability, accessibility and enhance a sustainable development of the society. These more complex grids with Distributed Generation (DG) interconnection could require a more complex protection system to achieve high quality service and enhance the grid stability. This work proposes non communicating, distributed distance protective relays for MV radial networks. These deployed relays would divide the feeder in smaller protected areas leading to shorter outage occurrence and duration for loads and producers. The system would also benefit of a communications free protection scheme, making it more reliable thanks to the independency of the relays. The proposed method was tested on most types of grids with overhead lines, cables and a mix of both, for several different neutral groundings of the HV/MV substation and with or without DG existence.
This paper presents a method for determining the offer price of collaborative power generators. The method considers an alliance formed by G generators with n independent offer prices. They collaboratively propose an offer price to the electricity wholesale market. The binary knapsack problem aimed at finding the best generation share of each generator that yields the maximum return to the alliance is used to represent the problem. It is solved with a hybrid algorithm consisting genetic algorithm and dynamic programming. The method is intended for promoting the participation of new power generators in the electricity market by way of horizontal supply chain integration.
The research work presented in this paper analyzes the impact of wind energy, phasing out central power plants and cross border power exchange on dynamic security of Danish Power System. Contingency based decision tree (DT) approach is used to assess the dynamic security of present and future Danish Power System. Results from offline time domain simulation for large number of possible operating conditions (OC) and critical contingencies are organized to build up the database, which is then used to predict the security of present and future power system. The proposed approach is implemented in DIgSILENT PowerFactory environment and applied to western Danish Power System which is experiencing a phase of major transformation. The results have shown that phasing out central power plants coupled with large scale wind energy integration and more dependence on international ties can have significant impact on dynamic security of Danish power system in future, if alternative measures are not considered seriously.
The paper is focusing on Particle Swarm Optimization (PSO) algorithm. Several variants of the PSO algorithm are studied. To evaluate their performances a software tool has been developed in Matlab environment. Three reference mathematical test functions have been used for this purpose. This paper represents a necessary step requested by the optimal power flow (OPF) computing approach. Currently the authors are focusing on developing a PSO based OPF computing algorithm. The most suitable PSO algorithm variant is provided based on the analyses within the current paper.
Voltage control in distribution networks is an important task in electrical engineering systems. This paper deals with the development of control strategies for low voltage networks with a high penetration level of distributed generation. In order to improve load flow conditions and ensure power quality in the presence of decentralized power injections a model-based optimization algorithm is developed leading to changes in the network topology. Two voltage control strategies are presented including in their objective functions the node voltage deviations and the number of switching events. The optimization problem is stated as a constraint optimization problem, where the node voltages should remain in a certain band.
This paper presents a methodology for coordinated tuning of power system stabilizers taking into account a set of pre-specified operating conditions. The tuning procedure is formulated as an optimization problem which aims to maximize the system damping ratio. The proposed methodology is based on the bio-inspired Modified Cuckoo Search method. The methodology is applied for coordinated stabilizer tuning to New England test system. The results obtained are compared with a genetic algorithm approach.
