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with the continuous expansion of the scale of distributed new energy grid-connected power generation in the distribution network and the continuous improvement of penetration rate, the problem of distribution network voltage out of limit caused by distributed new energy grid connected can not be ignored. This paper analyzes the basic principle of voltage out of limit caused by the connection of distributed new energy sources to the distribution network,and analyzes the factors affecting the reactive power and voltage of the active distribution network with distributed new energy sources through BPA simulation, The compensation effects of the distributed series reactor and distributed shunt reactor are compared.

Regarding the initial value sensitivity issues commonly found in Newton-like power flow calculation algorithms, a zero-injection initialization numerical method for ill-conditioned power flow is proposed in this paper, which improves the convergence of power flow calculation in ill-conditioned power systems. Based on the initial power flow provided by this method, the unbalanced active power of each bus (the slack bus excluded) relates to the net injection of active power of that bus and the unbalanced reactive power of each PQ bus relates to the net injection of reactive power of that bus, thus avoiding significant power unbalance. The method put forward herein can provide a reasonable initial value for the power flow calculation so that difficulty in power flow convergence caused by the unreasonable initial power flow is effectively avoided. The Newton’s method and the optimal multiplier method are implemented respectively on a small-scale ill-conditioned test system to verify the feasibility of the proposed zero-injection initialization numerical method.

In recent years, with the rapid expansion of urban power grids, the automatic voltage control (AVC) system develops some new characteristics. Based on the technology of big data analysis and mining, this paper expounds an AVC system for urban power network with high load density based on the integrated dispatch and operation mode. This paper introduces several different application modes, and shows the operation characteristics of the multi-point distribution mode and the integrated control mode. The big data mining technology is used to discovering the hidden troubles and defects in AVC system. This paper also presents some other AVC key technologies such as security check of remote control, self-adaption analysis method and so on.