Research And Application On Reactive Optimized Compensation Technology For Power Grid

With the rapid development of national economy and modern power electronic technology, nonlinear equipments have been widely used in the power system, the load of power grid increases rapidly,and the design capacity of power equipment increasing constantly,the capacity of transformers, asynchronous electric motors also have a significant increase in the corresponding system, which have adverse effects on power quality and network loss. Therefore, it is particularly important for power system to optimize reactive power compensation,which is also beneficial to improve power quality, reduce losses, save energy, make full use of electrical equipment , ensure the safe operation and so on.Optimal reactive power compensation means that power quality is improved and network losses is reduced with the maximum reactive compensation equipment as little as possible,and it guarantee to meet the various operating constraints at the same time. The main work of this paper is as follows:Sensitivity and margin is analyzed in this paper.The differential algebraic equations (DAE) of power system is linearized at the operating point and derived a function style ofΔP andΔQ. At last to be introduced for the reduction Jacobian matrix of voltage sensitivity. Jacobi matrix is inversed, its diagonal elements into its two complementary dimension reduction of the inverse Jacobian matrix diagonal elements, and 2m+n-1 complementary reduction Jacobian matrix, the diagonal element of reduced order Jacobian matrix in No.i is the sensitivity of V-Q at bus i.The slip voltage equations of power system are transformed for the form of active component and reactive component, get branch voltage and branch currents of the active component and reactive component, It is combined by the end of the output power, eliminating its current components, to amend active and reactive power to form and calculate the branch admittance.The equations after transformed is binary quadratic equation group based on the voltage component,the circle center and radius is calculatated after standard form transformed, and reactive power margin is defined as two radius minus the distance between the two circle center. Load flow is calculated using Newton - Raphson method in the system, the trend analysis system for the distribution of low voltage nodes in the region by adding a virtual camera adjusted to keep the node voltage, change the voltage, integrated voltage and reactive power margin sensitivity the algorithm, to be fitted the Q-V curve of system. In the Q-V curve, the lowest point of the absolute value of the system reactive power margin, stable point of the slope of the voltage sensitivity. Using voltage sensitive and reactive margin analysis of the data out of the system is relatively weak and reactive nodes relatively large gap, the voltage sensitivity in descending order, reactive power margin by ascending order, combining the node voltage before compensation,select the bus of large voltage sensitivity and small reactive margin as the system reactive power compensation point.The capacity optimization and the relationship between the total reactive power compensation capacity and average power factor in system is researched, Reactive power optimization objective is to minimize the total loss, this loss under the other criteria listed in the system a slight increase of rate of loss and reactive power compensation between the partial differential equations, when the total system power loss compensation capacity of each point of the partial derivative same time, the whole network capacity is optimal distribution of compensation. Equations are listed after the system select the appropriate interpolation points, using Newton-Raphson power flow method to calculate the interpolation node loss.The use of Lagrange interpolation method to transform loss and the relationship between the conversion of reactive power compensation from the Lagrange interpolation polynomial, the derivative of its offspring into the partial differential equations, the partial differential equations into linear equations, simplifying the calculation. Set in the process of solving iteration, the compensation will be calculated on a capacity for the next cycle for calculating the interpolation nodes, through error analysis, when the precision to meet the requirements out of circulation, to ensure optimization of reactive power compensation capacity of the accuracy of the results nature.The IEEE-14 system and the two actual network of 70 bus and 205 bus is analyzed.The original compensation is removed and power flow is calculated in the IEEE-14 system, combined with trend data, fitting all Q-V curve of the system, voltage sensitivity and reactive power margin of the system is analyzed, larger voltage sensitivity and less reactive power margin is selected as the reactive power compensation point, the point of re-election system after the optimization calculation of reactive power compensation capacity of the system of compensation and flow calculation, the compensation for the former, the original compensation to optimize the voltage and loss compensation are compared to prove the rationality of the proposed method. Power flow is calculated in 70 bus system,follow the low voltage point, first elected to compensate for low voltage point, and then through the Q-V curve, select a different compensation point, through the compensated voltage and contrast loss can be seen, Not all low-voltage points are subject to compensation, Q-V curves method is obtained reasonable. the original compensation point in the 205 bus actual network,based on the use of such a slight increase of loss rate and numerical methods for solving the system capacity optimization, it is compared between the voltage and power loss with and without optimization, the results show that the lower loss after capacity optimized is lower, the optimization method is feasible.