Abstract
　　　The flow calculation is the most fundamental and most commonly used in the calculation of the power system. Under the given operating conditions of the system, network wiring and component parameters by flow calculation can determine the bus voltage (magnitude and phase angle), each branch of the power flow, the power loss of the entire system. The trend is calculated to achieve the necessary means of power generation and supply of power system security and economy and an important aspect of our work.  
　　　Therefore, the flow calculation in power system planning, have a wide range of applications in the production run, scheduling management and scientific computing.
Flow calculation in mathematics multivariate nonlinear equations, solving There are many ways, when the system is relatively simple, the number of nodes is relatively small, we can obtain the parameters by hand count, but when the system is a complex network by hand calculation of the parameters is clearly impossible, which set forth requirements for the emergence of computer algorithms.
    The preparation of the power flow calculation program written in C or Matlab language, more complex grid containing ring network power flow calculation, the output node voltage (pu and famous value), branch current and apparent power (standard verify the correctness of the unitary values ​​and the well-known value), the calculation of the IEEE test systems.

    Keywords: flow calculation; Matlab; IEEE

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