Utilising stored wind energy by hydro-pumped storage to provide frequency support at high levels of wind energy penetration

Wind farms (WFs) contribution in frequency deviations curtailment is a grey area, especially when WFs replace large conventional generation capacities. This study offers an algorithm to integrate hydro-pumped storage station (HPSS) to provide inertial and primary support, during frequency drops by utilising stored wind energy. However, wind turbines follow maximum power tracking, and do not apply frequency support methods, thus the wasted wind energy is mitigated. First, HPSS rated power and energy capacity are determined based on several givens, including wind speed and load characteristics. Thus, HPSS major aspects are estimated [e.g. pump(s), reservoir layout and generator(s)]. Second, offered algorithm coordinates energy storage, and releasing through several dynamic and static factors. HPSS output is continuously controlled through a timed approach to provide frequency support. A hypothetical system is inspired from Egyptian grid and real wind speed records at recommended locations to host WFs. Case studies examine the algorithm impact on frequency recovery, at 40% wind power penetration. The responses of thermal generation and HPSS are analysed to highlight the influence of tuning the parameters of the proposed algorithm. The assessment of several frequency metrics insures the positive role of HPSS in frequency drops curtailment. Simulation environments are MATLAB and Simulink

WIND ENERGY PENETRATION IMPACT ON GRID FREQUENCY DURING NORMAL OPERATION AND FREQUENCY DEVIATIONS

The fluctuating nature of output from wind farms in relation to wind speed conditions at each wind turbine causes a severe burden on conventional generators, and such wind power variations have a considerable impact on grid frequency and voltage stability. In addition, such fluctuations in output create economic problems, as most of system operators apply financial penalties on wind farms owners when generation levels deviate from forecasted schedules by certain ratios. This thesis focuses on the negative impacts of moderate and high levels of wind power contribution to grid generation capacities on the frequency response. Particularly, integrated wind farms replace certain ratios from conventional generation capacity. Retired conventional capacity is decided according to estimated annual energy production of installed wind farms

Wind energy penetgration impact on grid frequency during normal operation and frequency deviations

The fluctuating nature of output from wind farms in relation to wind speed conditions at each wind turbine causes a severe burden on conventional generators, and such wind power variations have a considerable impact on grid frequency and voltage stability. In addition, such fluctuations in output create economic problems, as most of system operators apply financial penalties on wind farms owners when generation levels deviate from forecasted schedules by certain ratios. This thesis focuses on the negative impacts of moderate and high levels of wind power contribution to grid generation capacities on the frequency response. Particularly, integrated wind farms replace certain ratios from conventional generation capacity. Retired conventional capacity is decided according to estimated annual energy production of installed wind farms

Control and quantification of kinetic energy released by wind farms during power system frequency drops

High wind energy penetration levels in modern power systems draw attention towards wind farms expected role during frequency drops. Wind farms positive contribution required by system operators basically depends on the amount of kinetic energy stored in wind turbines rotating parts and how to manage it during frequency deviations elimination. This study presents an algorithm to estimate and control the quantity of extractable kinetic energy stored in a wind farm during frequency drops. Moreover, it manages stored kinetic energy release within a given time span to achieve positive participation in frequency drops clearance. The proposed method is based on tuning the tip speed ratio before and during the frequency drop according to several factors. The recovery time required by the wind turbine to retain its normal speed is also a function of several parameters including turbine inertia and the incoming wind speed. The proposed algorithm's impact on power system frequency is analysed by assessing the expected enhancement in frequency deviation. A hypothetical grid is considered as the benchmark including detailed modelling for wind speeds, wind turbine and wind farm to improve the creditability of the obtained results. Presented research work outcomes highlight the impact of wind farms replacement for conventional generators. Executed simulations proved that applying the proposed algorithm neutralises wind energy penetration influence on system frequency response, even more, it causes solid improvements unless the incident wind speed is too slow or the frequency drop is too high. Simulation environments are MATLAB and Simulink