Optimal Design of Wind-hydro-gas System for Stochastic Power Fluctuation Smoothing in Wind Farms

In order to reduce the ramping capacity required by large-scale wind farms, both hydro and gas station were used to mitigate the stochastic fluctuation of wind power. Fluctuation frequency was defined as the index of joint output fluctuation, and was used to avoid capacity redundancy. Mathematical model of wind-hydro-gas system design was established with fluctuation frequency. Hydro regulation rate and gas station capacity were co-optimized with the objective of hydro regulation cost, gas investment cost and expected fuel cost minimization using the probability density function of wind power fluctuation. Markovian steady-state analysis was proposed to solve efficiently. Analytical expressions of fluctuation frequency and expected fuel cost were obtained. Numerical results show: when a certain hydro regulation rate is provided, the non-fluctuation frequency can achieve 96% with a little cost increment and a gas station capacity of about 12% wind farm capacity; the proposed steady-state analysis method is fast and accurate.