Voltage Regulation Study Of City Receiving-End HV Distribution Network During The Light Load Period Based On PSASP

Safe and reliable power quality is a basic requirement for modern power grid, and the network' voltage control & management is an important part of the power system, as a consequence, the most critical task for power dispatching and operation department is to guarantee the voltage to run near its rated value. The study found that in the Spring Festival as well as other periods of light load, due to the sharp decrease of electricity load within the network, the network itself can't effectively absorb the reactive power, resulting in the regular occurrence of reactive surplus and the bus voltage violating its upper limit in the urban 110 k V distribution network. For the receiving-end network, the situation will be more severe owning to the lack of effective voltage regulating measures. In the case of the conventional voltage regulating used up, how to adjust the voltage becomes a serious problem. Based on the analysis of mechanism and characteristic about voltage running above the upper limit in the city receiving-end HV distribution network during the aforementioned time periods, the paper proposed two mutually exclusive schemes based on network reconfiguration and improved complex network's key identification, and the two regulating algorithms are actualized on the Visual Studio and electricity system analysis program(Power system analysis Software Package, PSASP). Practical urban grid of Sichuan of China indicates the proposed methods can greatly optimize the voltage profile and reduce the limit nodes' percentage of the total network, furthermore it avoids the shortcomings of traditional optimization algorithm such as: long computational time and curse of dimensionality, etc. The introduced schemes are simple and feasible and beams broad engineering application prospects.The paper has introduced the urban receiving-end distribution network from the aspects of s voltage levels, types of power supply, connecting modes, stability analysis and so on. Based on the fact that in the actual operation most 110 k V substations are supplied by the Mid-side of 220 k V transformers,it proved that eliminating the phenomenon of 220 k V substation Mid-side bus voltage's over-limit can effectively improve the associated 110 k V bus voltage profile, thus to solve the wide range of voltage running over the upper-limit problem fundamentally, and the above opinion becomes the fundamental to establish the voltage regulation methods. Meanwhile the paper has built mathematical mode on the main electrical components including: high voltage distribution network in the main electrical components cable lines, loads and three-phase-three-winding on-load tap changing transformers, taking into account of the compatibility with PSASP software based on the classical model in the educational material, a certain amount of simplification and improvement is executed.When the voltage regulation measures are exhausted, a new voltage regulation method based on 110 k V urban distribution network reconfiguration is introduced. The strategy takes example by medium voltage network reconfiguration and considers the restraint of line thermal stability, transformer capacity and switching power flow on boundary, through changing original 110 k V substation connection mode, we finally optimizes the network voltage deviation degree. It is using contribution rate index to assess the influence of related substations' different connection mode on network-wide voltage amplitude, according to the calculated results we regulate the grid connection modes. The introduced method explore the network's own resources to regulate voltages without relying on external conditions.Under the same physical background, the paper proposed another method: based on identification of key points in the improved complex network. It combines the complex network theory and classical electrical analysis, and abstract the complex urban HV distribution network to the topological graph consisting of nodes(substations) and lines(power transmission lines). On account of the electric connection characteristic of the power system, it's equivalently replaced “degree” with the concept of “electrically coupled degree(EECD) to describe the importance of electrical nodes' location in the network. According to its cumulative distribution function, it's easy to identify the grid's physical nature. The paper points that in the heterogeneous scale-free network, through adjusting the spare line's switch status which connects to the key nodes, the whole network's voltage quality can be improved. WSCC-36 standard calculation examples and real urban receiving-end HV distribution network of Sichuan of China confirmed the effectiveness of the program.To achieve the above voltage regulation scheme, we choose VC++6.0 as the programming language, and utilize Visual Studio to call PASAS software executing power flow calculation, after the completion, Visual Studio can read the feedback results, according to the comparison with algorithm, it automatically modifies relative data model which is established in PSASP, Relying on the two software, the proposed voltage regulation algorithm can be implemented.