Wind speed interval prediction plays an increasingly important role in wind power production. The intermittent and fluctuant characteristics of wind power make high-quality prediction interval (PI) challenging. In this paper, a novel hybrid model based on gated recurrent unit (GRU) neural network and variational mode decomposition (VMD) is proposed for the wind speed interval prediction. At first, VMD is employed to decompose the complex wind speed time series into simplified modes, interval prediction model (IPM) and point prediction model (PPM) based on GRU are designed to conduct interval prediction on primary mode and point prediction on the rest modes before a composition and construction of the prediction interval. Then, error prediction model based on GRU is proposed to enhance the model performance by error correction. Eight cases from two wind fields are used to test and verify the proposed method. The results indicate that the proposed method is a high qualified method which is in possession of much higher PI coverage probability and narrower PI width.

This paper investigates the nonlinear modeling and stability of a doubly-fed variable speed pumped storage power station (DFVSPSPS). Firstly, the mathematical model of DFVSPSPS with surge tank considering nonlinear pump turbine characteristics was derived and established. Then, Hopf bifurcation analysis of DFVSPSPS was performed. The stable region was identified and verified by example analysis. Moreover, the effect mechanism of nonlinear pump turbine characteristics on the stability of DFVSPSPS was explored. Finally, the influence of factors on the stability and dynamic response of DFVSPSPS was studied. The results indicate that the emerged Hopf bifurcation of DFVSPSPS is supercritical and the region on the low side of the bifurcation line is the stable region. Nonlinear head characteristics have a significant influence on the stability and dynamic response of DFVSPSPS. Nonlinear speed characteristics have an obvious effect on the stability and dynamic response of DFVSPSPS only under positive load disturbance and unstable surge tank. Nonlinear head characteristics are unfavorable for the stability of DFVSPSPS under positive load disturbance and favorable under negative load disturbance. A smaller flow inertia of penstock, a smaller head loss of penstock and a greater unit inertia time constant are favorable for the stability of DFVSPSPS. The stable region under the positive disturbance of active power is larger than that under the negative disturbance of active power. The time constant of the surge tank presents a saturation characteristic on the stability of DFVSPSPS.