The current OLTC adjustment method does not fully consider renewable energy consumption and avoid voltage violation together. Therefore, this paper proposes a OLTC dynamic adjustment method considering the promotion of renewable energy consumption and uncertain voltage security risks. In this method, the chance constraints are used to describe the multivariate constraints, improving the anti-disturbance ability of the model. The method avoids unreasonable OLTC adjustment which can cause uncertain voltage security risk or decline of energy consumption. The proposed method is tested in the IEEE 33 Bus System and an actual system in southern of China. The results show that the renewable energy consumption can be increased by 30%.

In order to more accurately calculate the power variation of the active rural distribution networks with the doubly-fed-introduction generator after different types of faults occur, a new transient power deviation model (TPD) based on the branch flow model is proposed in this paper. The TPD model includes the inter-phase coupling factor and the dynamic interaction factor between buses. Based on the electromagnetic coupling between distribution cables and the dynamic interaction between buses, these two coefficients are used to calculate the transient power of the bus. Therefore, the TPD model offers a more intuitive representation of the active and reactive power deviations at the buses in the distribution system. Subsequently, based on the TPD model, the modified voltage-transient power control strategy (MV-TPC) is proposed. By redesigning the rotor-side converter side controller of DFIG, the impact of the faults, which cannot be repaired in a short period, on system stability is reduced. And the voltage stability at the point of common coupling of the DFIG is improved. Finally, simulations are conducted using the RTDS simulator on an IEEE 34-Buses distribution system in Arizona, USA, with the distribution DFIG to verify the effectiveness of MV-TPC in suppressing voltage fluctuations. The research results demonstrate its potential application in improving the stability of the distribution systems with wind farms.

The time evolution stochastic dynamics (TESD) and the unexpected stochastic event driven (USED) are significantly increased to change the dynamic characteristics of the power system operation. In this paper, a new algebraic differential model for the doubly-fed-induction generator (DFIG) in the wind farm is constructed to reflect the stochasticity of the TESD and the USED in the power system more intuitively, which is based on the Lyapunov transient stability theory and the noise to state stable (NSS) control theory. Sequentially, a new torque stochastic robust controller (TSRC) model construction method is proposed to apply more reliable and effective control to weaken the influence of the stochasticity on the whole system and reduce the pressure on the collaborative control of the power system in case of the stochastic large-scale system failure. This model shows that the wind farm system with the torque stochastic robust controller has higher robustness. Finally, a simulation of the New England 9-bus system with the DFIG is conducted to verify the applicability of the algebraic differential model in a deterministic system and the results show its potential application for the robust controller considering the power system with the wind farm.

With a large number of renewable energy connected, the penetration rate of grid connected inverter increases rapidly, and the interaction between converter and power grid and between converter and converter becomes more and more intense. The assumption that power grid is regarded as infinite power supply is no longer tenable. And a large number of new energy resource will change the transient instability mode of the power system and increase the risk of security and stability. In the process of simulation, how to establish a reduced order aggregate equivalent model of converter suitable for transient stability simulation becomes an urgent problem to be solved in the research of new energy resource connected. In this paper, based on singular perturbation theory, the reduced order modeling of DFIG (Doubly fed induction generator) converter is carried out. Firstly, according to the typical triggering criteria of DFIG relay protection action in transient stability problem, the modeling principles of relay protection and low voltage ride through behavior are analyzed, so as to accurately simulate the transient instability behavior of generator tripping. Secondly, a combined system of synchronous generator and DFIG wind turbine model is built. Different instability modes are classified by the time period and time scale of instability, and the influence of DFIG power supply on grid voltage instability is analyzed.