牛拉法算潮流，输入节点数，输入支路数，输入平衡母线节电号，输入误差精度，输入由支路参数形成的矩阵即可计算(The method calculates the input power, the input node number, the input branch number, the input power of the balanced bus, the input error precision and the input matrix formed by the branch parameters)