An Improved DC Power Flow Algorithm with Consideration of Network Loss

DC power flow is widely used in power system analysis such as power flow adjusting and fast security assessment, which mainly attributes to its advantages of linearity and rapidity. The active power balance problem caused by the network loss in DC power flow algorithm is researched in this paper. An improved DC power flow algorithm is proposed to reduce the power flow error which is mainly because of the neglect of the active power loss in transmission lines and transformers. In this improved DC power flow algorithm, the active power loss of each branch in the network is simulated with equivalent loads located at both ends of the branch, and so the power injection at each node contains an extra virtual equivalent load in order to balance the active power loss produced by the connected branches. Using this equivalent load model, one of the most critical problems is to calculate the equivalent loads added to the power grid as accurately as possible. If convergent initial power flow results calculated by AC power flow are available, the equivalent loads can be calculated directly and accurately. But in some cases, it is not convenient to obtain a convergent power flow especially when the topology or power injection of power grid model is changed greatly. In order to apply this equivalent load model without dependence on convergent initial power flow, a new effective iteration method is also presented to calculate the equivalent loads. The improved DC power flow algorithm proposed in this paper preserves the linearity and rapidity of standard DC power flow algorithm, but significantly achieves an advantage of much higher calculation accuracy. Plenty of actual calculation examples show that the improved DC power flow algorithm is effective and practical, as the power flow result calculated by the improved algorithm is much closer to the actual value than by the standard algorithm.