This paper proposes a second-order active disturbance rejection control (ADRC)-based control strategy with an integrated design of the flux damping method, for the fault ride-through (FRT) improvement in wind power generation systems with a doubly-fed induction generator (DFIG). First, a first principles model of the rotor and grid side converter of DFIG is developed, which is then used to theoretically analyze the system characteristics and show the damage caused to the DFIG system by a grid voltage fault. Then, the flux damping method is used to suppress the rotor current during a fault ride-through. In order to enhance the robustness and effectiveness of the flux damping method under complex working conditions, an ADRC approach is proposed for disturbance attenuation of the DFIG systems. Finally, a comparison of the proposed method with three other control approaches on a 1.5-MV DFIG system benchmark is performed. It is shown that the proposed method can adaptively and effectively improve the system performance during an FRT.

With the gradually widely usage of the air conditioning (AC) loads in developing countries, the urban power grid load has swiftly increased over the past decade. Especially in China, the AC load has accounted for over 30% of the maximum load in many cities during summer. This paper proposes a scheme of constructing a virtual peaking unit (VPU) by public buildings' cool storage central AC (CSCAC) systems and non-CSCAC (NCSCAC) systems for the day-ahead power network dispatching (DAPND). Considering the accumulation effect of different meteorological parameters, a short term load forecasting method of public building's central AC (CAC) baseline load is firstly discussed. Then, a second-order equivalent thermal parameters model is established for the public building's CAC load. Moreover, the novel load reduction control strategies for the public building's CSCAC system and the public building's NCSCAC system are respectively presented. Furthermore, based on the multiple-rank control strategy, the model of the DAPND with the participation of a VPU is set up. The VPU is composed of large-scale regulated public building's CAC loads. To demonstrate the effectiveness of the proposed strategy, results of a sample study on a region in Nanjing which involves 22 public buildings' CAC loads are described in this paper. Simulated results show that, by adopting the proposed DAPND scheme, the power network peak load in the region obviously decreases with a small enough deviation between the regulated load value and the dispatching instruction of the VPU. The total electricity-saving amount accounts for 7.78% of total electricity consumption of the VPU before regulation.

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The fluctuation of wind power may easily cause the great impact on the grid while it was integrated in the grid in large scale, and resulted in the generally existed phenomenon of abandoned wind power and power brownouts accordingly. Aiming to such problem the academic circles have proposed the method of hydrogen production to consume the excessive wind power. In this paper, with the consideration of the power supply scheme for micro grid, it aims to enable the wind power better providing power for hydrogen production, and designs its structure according to the working principles of each module, and completes the system modeling of such micro grid based on Dig SILENT Power Factory software and carries out the flow analysis on such model and simulation of power control model, it proves that this system can be run stably theoretically.