A static analysis method to determine the availability of kinetic energy from wind turbines

This paper introduces definitions and an analysis method for estimating how much kinetic energy can be made available for inertial response from a wind turbine over a year, and how much energy capture must be sacrificed to do so. The analysis is based on the static characteristics of wind turbines, Weibull distributions of wind speed, and standard definitions of turbulence intensity. A control scheme is presented that extracts an appropriate amount of kinetic energy based on operating point. The tradeoff of wholesale energy revenue for potential kinetic energy revenue is explored. The break-even point is compared with marginal prices for kinetic energy obtained in the literature, and found to be favourable for one example of a full-converter interface wind turbine having a wide speed range

Prediction of power fluctuation classes for photovoltaic installations and potential benefits of dynamic reserve allocation

During partly cloudy conditions, the power delivered by a photovoltaic array can easily fluctuate by three quarters of its rated power in 10 s. Fluctuations from photovoltaics of this size and on this time scale may necessitate adding an additional component to power system secondary and primary reserves to regulate frequency. This study quantifies the benefit of dynamically sizing a reserve component to cover photovoltaic fluctuations so that the additional reserves are different for each hour. The concept of categorising an hour as belonging to one of three possible fluctuation classes is presented. Based on historical array data and weather forecast information, several methods of forecasting these classes are evaluated, including persistence, Markov chains and a neural network. A practical tool based on class forecasting is proposed to aid in estimating a photovoltaic reserve requirement ahead of time for horizons ranging from 1 to 24 h. Results indicate that of a 10% possible reduction in total reserves held, most of this benefit (8%) can be obtained for hour-ahead scheduling with persistence forecasting and that a similar benefit may be possible for four-hour ahead scheduling if neural networks based on weather forecast information are introduced

Network fault response of wind power plants in distribution systems during reverse power flows. Part II

Abstract—The ability of wind power park modules to control their response to transmission network faults allows for specification of new control features directed at stabilising the power system response during and after disturbances. However, the ‘effectiveness’ of these features in situations where wind power park modules are connected to ‘weak’ systems needs further clarification. The objective of the paper is to study the response of wind power park modules in distribution systems to transmission network faults during reverse power flows. The focus lies on the ‘effectiveness’ of their fast voltage control. A sensitivity analysis is performed to understand the differences made by the pre-fault operating point, the wind power park module’s fault and post-fault control modes and their settings, and the load modelling. The results show that correct load modelling is very important, the post-fault transmission system voltage recovery is worsened during reverse power flows, and that reactive current injection significantly affects the post-fault voltage recovery. Certain grid connection requirements worsened voltage recovery or even caused instability for some control settings

Unit commitment and economic dispatch for operations planning of power systems with significant installed wind power capacity

No abstract

Contribution of negative-sequence controlled distributed generation to power system stability under unbalanced faults : a discussion paper

The transformation of the power system in terms of efficiency and sustainability will further lead to increasing converter-coupled generation and demand. This changes the system's characteristics and influences its stability. Despite these fundamental changes, the secure operation of the power system must be maintained at all times. DG and any converter-coupled generation of relevant size are requested to stay connected to keep power equilibrium and to support the voltage during faults. The balanced fast voltage control currently applied for all types of faults could be improved by an unbalanced injection of short-circuit current among the three phases depending on the fault. A technical solution is an active control of the negative-sequence during unbalanced faults. However, introducing a general requirement, e.g. in grid codes, for this new feature must be well justified. This paper is intended to start a structured discussion of unbalanced fast voltage control by converter-coupled generation for unbalanced faults from a system perspective

Operating reserves and wind power integration : an international comparison

This paper provides a high-level international comparison of methods and key results from both operating practice and integration analysis, based on an informal International Energy Agency Task 25: Large-scale Wind Integration