| Today's social development and energy consumption are inextricably linked.The discharge of fossil energy has caused problems such as environmental pollution and the greenhouse effect,making economic development unsustainable.Therefore,the development and utilization of new energy has become an inevitable choice for sustainable development.However,the increasing capacity of distributed power access has gradually changed the power flow distribution of the power system and changed the voltage distribution.Moreover,due to the randomness,intermittentness and volatility of distributed power supply,it will lead to voltage fluctuations at the grid connection point,frequent voltage overshoot and other issues,affecting the safe and stable operation of the power system.On the other hand,the traditional power system voltage regulation method fails to make full use of the reactive power adjustment capability of the distributed power plant itself,relying solely on the adjustment of the transformer tap and the switching of the discrete reactive power compensation device.In actual production,there are problems such as frequent adjustment of taps and frequent switching of capacitors,and this problem will be more prominent after distributed power supply access.Therefore,the operating personnel need to improve the reactive power control strategy after the distributed power supply is connected to ensure the safe and economic operation of the distributed power grid after the grid is connected.In view of this,this paper starts with the following three aspects:(1)The preliminary analysis of the influence of photovoltaic access on the voltage distribution of the distribution network node,and the actual 20kV distribution network in a certain area as an example,the simulation verified the influence of distributed power supply and reactive power regulation on the voltage characteristics of the distribution network.Firstly,after the photovoltaic access,the distribution of the distribution network nodes and the principle of line overvoltage are theoretically analyzed;Then,it is modeled on the PSD-BPA software platform,and simulation examples are carried out in various scenarios such as overvoltage caused by sudden increase in photovoltaic output and tidal current reversal caused by sudden increase in photovoltaic output;Combined with a 20kV distribution network system in a certain area,the simulation verified the tidal current reversal problem caused by PV spurt and the voltage cross-border problem,and analyzed the influence of the re-power supply on the voltage variation of the distribution network.(2)A comprehensive index considering voltage out of bounds and stability is proposed.The adaptability and performance of three sets of branch voltage stability indexes are simulated and analyzed.Combined with the more adaptable Lpqu index(the branch voltage stability indicator independent of the line model mentioned later),a comprehensive evaluation index considering voltage crossing and voltage stability is proposed,and the simple branch system is used respectively.The actual distribution network system simulation verifies the correctness and effectiveness of the indicator.(3)A time-based progressive reactive power optimization method based on photovoltaic access and considering network loss and voltage crossing is proposed.The comprehensive index of voltage crossing and stability is added into the objective function,and the mathematical model of single-time section reactive power optimization is established.The optimization process is based on the load change trend and the photovoltaic power output characteristics for time-phase multi-objective optimization.The actual 20kV distribution network in the region demonstrates the effectiveness of the proposed method. |
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