Optimized configuration method of capacitor type device against DC magnetic bias with the least device quantity

Abstract

In order to prevent transformer magnetic bias made by HVDC monopolar operation, for the time being, the devices to against DC magnetic bias are mainly installed in several stages. At first, DC current is obtained by simulation or measure value in substation. Second, the places to deploy the device to against DC bias are decided based on that if DC current beyond the standard in the spot. Then, DC current is measured in the operation to judge following device placement scheme. Repeat steps upside, the device to defense DC magnetic bias will be set into the necessary place and the DC current will be restrained lower than standard ultimately. In this way, it is a long cycle and hard work to achieve the whole process. Furthermore, the comprehensive solution of device placement can't be obtained only according to the existing engineering measurement value or simple simulation calculation based on fixed operation condition. The paper proposes a simple and comprehensive method to complete device configuration. In each procedure, for placement of devices to against DC magnetic bias, DC current distribution in various AC power grid operation modes are calculated with PSCAD/EMTDC simulation software, then, different device placement solutions may derived. The paper establishes an AC power grid simulation model for actual AC system adjacent to DC grounded pole, then, a voltage source is accessed to transformer neutral point as an equivalent circuit to DC current influence. finally, DC current distribution in AC system can be calculated. A set of configuration rules is proposed in the paper. Based on the rules, there are several initial configuration solutions of device against DC magnetic bias. Subsequently, the initial solution can be refined as follows: the equivalent circuit of capacity type device to against DC magnetic can be accessed to transformer neutral point, repeat the process of calculating DC current and accessing the device equivalent circuit against DC bias. As a conclusion, there are several solutions obtained. An estimate scheme is set up to evaluate the solutions proposed. The evaluation goal is to make the number of the device installment least, and the final optimization result is given. The study shows that: the solution proposes in the paper utilizes simulation method, which can give an integrative and economic scheme. Also, it can be easily realized.