Muhammad Shoaib Khalid

Design of Wind Turbine Dynamic Trip-Off Risk Alarming Mechanism for Large-Scale Wind Farms

The wind power in China is being developed mainly in terms of large scale, long distance, and high clustering. In this scenario, the uncertainty of wind farm operation gradually becomes a significant factor that power grid dispatcher needs to deal with. Among which, trip-off risk of wind turbine results from system disturbance, fault and fault removal of wind farm, etc. Besides, the geographical distribution of wind turbine usually also has the impact on the trip-off risk of wind farm. In view of above factors, existing security analysis methodology is difficult to satisfy the requirement of real-time alarming due to extreme analytical difficulty and huge computing complexity. Therefore, reasonable design of trip-off risk measure index of wind turbine becomes a key issue to implement a dynamic trip-off real-time alarming system. In this paper, a wind turbine trip-off decision tree system is constructed with the discrete characteristics of wind turbine distribution in wind farms taken into account. The decision trees can perform data mining using online information and make fast prediction on wind turbine voltage out-of-limit and trip-off situations under anticipated accident sets. The trip-off risk measure indexes are then output in light of the prediction results, which can provide intuitive risk level information and decision references for operators in wind farms and power systems. The results of case studies show that the proposed method can meet the requirement of prediction accuracy and resolve the contradictions between the amount of modeled nodes, the diversity of anticipated faults and the computation time when performing over-voltage early warning and control strategies.

Multi-objective chance constrained programming model for operational-planning of V2G integrated microgrid

This paper presents a novel chance constrained programming model for the operational-planning of a microgrid containing renewable energy sources like wind and solar, and vehicle to grid (V2G) storage. The model investigates the economic implications of the V2G storage on the microgrid operation. The microgrids consisting of intermittent renewable energy sources always need additional backup to mitigate the fluctuating power. This additional backup results in increased investment and operational costs. The V2G storage in such a situation can act as energy buffer and can supply the microgrid with balancing services at low costs. However the availability of the power from the V2G storage is also intermittent in nature because of the random plug-in pattern of electric vehicles. In this paper a microgrid containing a wind, PV and diesel generation and energy storage (V2G/flxed) is connected to an external grid. The external grid has the problem of capacity shortage. Because of the intermittent energy sources, a novel multi-objective stochastic chance constrained programming model is developed for the operational-planning of microgrid. The multiple objectives include the minimization the total net present cost and the operating hours of the diesel generation subject to constraints. The time series data for wind speed, solar radiation, V2G plug-in pattern and load fluctuation is estimated by using the Metropolis-Hastings algorithm, which is a Markov chain Monte Carlo Method. Due to the conflicting objectives, the non-dominant solutions are sorted out and presented using the Pareto front. The simulation results show confidence levels of provision of power by V2G storage and renewable energy sources. The results further show substantial economic implications of V2G storage on microgrid operation in terms of minimization of the total net present cost.

A New Distance Protection Method Considering TCSC-FCL Dynamic Impedance Characteristics

Ignoring the dynamic impedance characteristics of a thyristor-controlled series-capacitor-type fault current limiter (TCSC-FCL) may lead to maloperation/fail-to-trip or slow response of distance protection. To solve the above problem, the TCSC-FCL dynamic impedance analysis model was established. Taking the special operation mode of the TCSC-FCL into account, the time-varying characteristics of the TCSC-FCL during the whole process from the series compensation mode to the current-limiting mode were analyzed. Then, this paper proposed the function expression of dynamic impedance characteristics of the TCSC-FCL and put forward the distance protection setting strategy based on a dynamic offset impedance circle in order to eliminate the influence of TCSC-FCL dynamic impedance characteristics to the distance protection operation. By establishing a typical simulation model including the TCSC-FCL, the correctness of dynamic features analytic expression and the distance protection setting strategy is proved with extensive simulation results.

Field studies on the Inrush Current for 33/11kV transformer and the effect on voltage interruption during switching operation of 10MW wind farm

The Inrush Current for transformer switching operation study is an electromagnetic transient analysis (EMT) and are performed in order to investigate the network response after the energized the two 33/11 kV, 7.75MVA transformers in the Layafa S/S. The Inrush current associated with transformer energizing can cause some reactions that may adversely affect other loads in the power networks system, for instance voltage sags or over-voltage phenomena which could cause nuisance tripping for protective devices or loads. Protection devices may mis-interpret these events as fault currents, if the protection devices are not properly coordinated well. In this paper, the inrush current analysis was performed for the generators-transformers of the wind farm switching operation. In the study analysis, the 33/11 kV transformers will not be energized at the same time. Each transformer will be energized at no load condition, with the tap changer set to the maximum step of the HV side (higher voltage) in order to minimize the inrush current values. The simulation analysis was performed which the aid of DigSilent and EMT computer simulation to establish this study while considering the minimum short circuit power in the grid and the Wind Farm disconnection from the system. This paper is based on the field results test of the newly installed wind farm generator-transformer in relation to network interruption on the 33 kV and 11 kV systems during the switching on operation especially transient voltage phenomena.