A new voltage instability detection index based on real-time synchronophasor measurements

This paper demonstrates the performance of the Reactive Power Loss Based Voltage Instability Detection Index (QLVIDI), previously introduced in [1], under various testing conditions applied to the New England 39 bus test system using time-based simulations in the Power System Analysis Toolbox (PSAT) in MATLAB. The proposed scheme calculates an instantaneous time series of reactive power losses taking into account the direction of active power flow in every node in the system by considering the reactive power limits of the generators. This time series data is then used to evaluate a cumulative reactive power loss and the degree of deviation from the base case loss for developing QLVIDI. The effectiveness of the proposed index in early detection of imminent voltage collapse scenarios has been tested in various cases and also compared with already existing Improved voltage instability monitoring index(IVIMI)

Operational Planning and Optimisation in Active Distribution Networks using Modern Intelligent Power Flow Controllers

In this paper, a centralised control framework is introduced for day-ahead operational planning of active distribution networks which accommodate high levels of distributed generation resources. The purpose of the framework is to plan network operation in order to minimise power curtailment from distributed generation and maintaining acceptable levels of voltage regulation throughout the network. For this purpose, both power flow control and rapid network reconfiguration have been considered as various acceptable levels of control available to the network operator to provide required levels of operational flexibility. The power flow control within the network is promised by the application of fully controlled back-back voltage source converters placed in key points (both normally-open and normally-close) in the network. Meanwhile, the network reconfiguration constraints guarantee that radial topology is always maintained in order to avoid tremendous changes in the protection system coordination. The operation of a modified 33-bus system exemplar is analysed in three case studies namely, passive network (base case), active network using remote-controlled switches and active network using intelligent power converters. Results show a significant saving in terms of operational costs as well as transmission losses in active cases despite the radial constraint condition in place

Modelling and Evaluation of Wind Speed Time Series for Reliability Analysis of Offshore Wind Farms

This paper outlines proposed testing criteria for wind speed time series (WSTS) models. The objective is to assess their suitability for reliability analysis that is dependent on an accurate representation of weather patterns. Two WSTS models were analysed for their suitability against these criteria. The Markov model was found to be suitable for resource assessment, but would require modification before it could represent weather patterns, whilst the random sampling model could represent weather patterns more accurately, but could not be used for resource assessment

Determining the Wind Speed Distribution within a Wind Farm considering Site Wind Characteristics and Wake Effects

This paper introduces a wind speed model for simulating the distribution of wind speeds within a wind farm. The model combines a macro scale wind speed time series (WSTS) model based on a continuous Markov process with a wake flow model, based on the Jensen model, to produce wind speeds upwind of every wind turbine. This model has been designed for use in the testing of turbine coordinated control algorithms and for use in detailed reliability analysis. An example analysis was carried out to investigate the Annual Energy Not Produced (AENP) due to wake effects on a single string wind farm. It was found that the wakes accounted for a 20.2% reduction in energy production compared to the wakeless scenario, highlighting the need to model these wake effects

Impact of high wind penetration on variability of unserved energy in power system adequacy

This paper presents results on variability of out-turn shortfalls about the expected value indices which are usually presented in resource adequacy studies, for a range of Loss of Load Expectation (LOLE) levels and installed wind capacities in a test system generally representative of future Great Britain system scenarios. While the details of results will clearly vary between systems, one very general conclusion is possible. In the results presented, for a given LOLE level, the probability of very severe out-turn in a future peak season is much greater at high installed wind capacity. Thus for this system, as the installed wind capacity increases, a constant level of LOLE cannot be taken as an indicator of an unchanging overall risk profile of the system. This further demonstrates that in any system, LOLE cannot be assumed to be a good summary statistic of risk profile as the installed variable generation (VG) capacity increases, and that it might be necessary to reconsider the near-universal use of expected value risk indices as the main headline indices in utility adequacy studies