Block Diagram Description Method Of Power Transmission Relationship In The Steady-State Power Grid

With the continuous development of modern power system, people demand a higher level of system reliability and economy. This inspires the researchers try to reveal the transmission law within the power values in order to adapt with the high level optimizing operation.The paper, basing on the consistency of block diagram description and algebraic equation description, proposed the block diagram description method to describe the power transmission rule. First, by analytical analysis, the power transmission relationship in the one-source steady-state circuit was indicated in the paper. And two characteristics were concluded as follows:each node and branch has independent power transmission relationship, and the power parameter has head-to-tail characteristics at the connection point of each node and branch. According to the first characteristic, each node or branch was chosen as a basic power transmission unit. And the ratio of the output power to the input power of each unit was defined as the unit’s power transmission gain. Different units’ transmission gain was then acquired by analytical analysis. Since the block diagram is the graphic solution of the algebraic equations, the derived transmission gain can be converted into the block diagram. The block diagram of each node and branch was established basing on the conversion thoughts. According to the second characteristic, a block diagram of the whole power grid can be drawn in accordance with the connection relationship among the basic units. In case analysis, the IEEE9 system’s power flow results were calculated first. The transmission gain of each basic unit and the block diagram of the whole power grid were then acquired. The comparative analysis with the calculation results proves the correctness of the block diagram description method. This method provides a new mathematical approach for power flow analysis.