Patent Document ID: 20090182518
Application ID: 12013629
Patent Flag: 0

Claim One:
1. A method of calculating power flow solution of a power grid that includes generalized power flow controllers, the power grid comprising a plurality of buses, a plurality of transmission lines, a plurality of generators, a plurality of loads, and at least one generalized power flow controller; the generalized power flow controller having one shunt branch, and a plurality of series branch; the shunt branch having a sending-end connecting in parallel with a bus of the power grid, and comprising a shunt voltage sourced converter and a shunt coupling transformer, being modeled by an equivalent shunt voltage source in series with an impedance; each of the series branches having a sending-end and a receiving end, connecting in series with a transmission line of the power grid, and comprising a series voltage sourced converter and a series coupling transformer, being modeled by an equivalent series voltage source in series with an impedance; the AC side of the shunt voltage sourced converter connecting to the power grid through the shunt coupling transformer, and AC side of each of the series voltage converter connecting to the power grid through the series coupling transformer; the DC sides of the shunt voltage sourced converter and the series voltage sourced converters jointly connecting to a DC capacitor to share the same DC bus; the power flow solution including the voltage of each bus, the active and reactive power flow of each transmission line, the reactive power generated from each generator and the equivalent voltages of the voltage sourced converters of each generalized power flow controller; the method characterized in that the variable related to the generalized power flow controller being expressed in d-q components, wherein the d component is in phase with a reference phasor, and the q component leads the reference phasor by 90 degree; the method comprising the steps of: (A) setting the initial values of state vector, wherein the elements of the state vector, called state variables, comprising the voltage magnitudes of all buses excluding the bus connected to the shunt branch of the generalized power flow controller, the phase angles of all buses, the d-q components of the shunt branch current of the generalized power flow controller; (B) constructing the mismatch vector of the power grid ignoring the generalized power flow controller; (C) establishing the corresponding Jacobian matrix using the first order derivatives of the mismatch vector obtained in step (B); (D) performing a d-q decomposition on the voltage of the receiving-end of each series branch; (E) calculating the equivalent load of the shunt branch; (F) judging whether there exists a series voltage sourced converter, if it exists, go to step (G), otherwise, go to step (H); (G) calculating the equivalent loads at the sending-end and receiving-end of each series branch, from the 2 nd to n th series branch, wherein n is the number of the voltage sourced converters; (H) calculating the total active power generated from voltage sourced converters; (I) modifying the mismatch vector according to the equivalent load of the shunt branch, the equivalent loads of each of the series branch, and the total active power generated from voltage sourced converters; (J) modifying the Jacobian matrix using the first order derivatives of the modified mismatch vector obtained in step (I); (K) substituting the modified mismatch vector obtained in step (I) and the modified Jacobian matrix obtained in step (J) into the iterative formula of Newton Raphson algorithm to update the state vector; (L) judging whether the state vector converges within specified tolerance, if it does not, go back to step (B), otherwise, proceeds to step (M); (M) calculating the equivalent voltages of the shunt converter and series converters; (N) calculating the power flow solution according to the state vector and the equivalent voltages of the shunt converter and series converters.