System and method for converging iterations for loadflow solutions in a hybrid loadflow computer arrangement having transient stability analysis capability

Claim 2

A hybrid loadflow computer arrangement with transient stability analysis capability comprising a DC analog simulator of an AC network, said simulator including a plurality of bus, generator, load, tie line and line DC circuits interconnected to correspond to the AC network, a digital computer, analog input and output systems for transferring signals between said computer and said simulator, said signals including tie line currents and external voltages, and load currents and voltages transferred to said digital computer, said computer including means for determining corresponding tentative tie powers and load powers as a function of said tie line and load currents and voltages, and for determining whether said tentative powers are within predetermined tolerances, said computer and said simulator including means for determining in successive iterations new tie line and load powers as a function of tie line and load powers in the next preceding iteration so as to produce convergence to a loadflow solution in successive iterations.

Claim 3

A machine method for making loadflow solutions for an electric power system, the steps of said method comprising using a DC analog simulator of an AC network to generate representations of predetermined network variables including tie line and load powers, using a digital computer to generate representations of whether said tie line and load powers are within predetermined tolerances, and operating said computer and said simulator to generate in successive iterations representations of new tie line and load powers as a function of tie line and load powers in the next preceding iteration so as to produce convergence to a loadflow solution in successive iterations.

Claim 4

A machine method for making loadflow solutions for an electric power system, the steps of said method comprising using a DC analog simulator of an AC network to generate representations of predetermined network variables including tie line and load powers, using a digital computer to generate representations of whether said tie line and load powers are within predetermined tolerances, and operating said computer and said simulator to generate in successive iterations representations of new tie line and load powers as a function of tie line and load powers in the next preceding iteration so as to produce convergence to a loadflow solution in successive iterations.

Claim 5

A hybrid loadflow computer arrangement with transient stability analysis capability comprising a DC analog simulator of an AC network, said simulator including a plurality of bus, generator, load, tie line and line DC circuits interconnected to correspond to the AC network, a digital computer, said digital computer including means for determining generator mechanical powers and generator terminal voltage magnitudes, first and second load admittances for each load, load real and reactive power, external tie bus voltages, and tie line real and reactive power, analog input and output systems for transferring signals between said computer and said simulator, said computer including means for generating representative signals of said generator mechanical powers and generator terminal voltage magnitudes, said first and second load admittances for each load, and said external tie bus voltages, means for applying said representative signals to corresponding generator, load and tie line DC circuits, each of said bus DC circuits including means for responding to generator, load, tie line and line phasor input current signals and for generating an output bus voltage phasor signal, each of said generator DC circuits including means for responding to the difference between generator mechanical power and generator electrical power input signals and the difference between generator terminal voltage input signals and bus voltage phasor input signals, and for generating a generator swing angle output signal and a generator phasor current output signal, each of said load DC circuits including means for responding to applied bus voltage phasor signals, means for receiving and representing said first and second load admittance signals, and means for generating a bus to load current phasor output signals, each of said tie line and line DC circuits including means for responding to the difference between applied bus voltage phasor signals and generating an output line phasor current signal in accordance with at least the equivalent series branch impedance, one of said applied bus voltage phasor signals to each of said tie line circuits being a digital computer determined external tie bus voltage signal, said digital computer including means for determining tentative real and reactive tie line and load powers as a function of corresponding external tie bus and load voltages and tie line and bus to load currents, said digital computer including means for determining whether said tentative powers are within preselected tolerances, said digital computer including means for determining in successive iterations new first and second load admittances as a function of load power and bus to load voltage values in the next preceding iteration, and for determining in successive iterations new external tie bus voltages as a function of tie line power and tie line current values in the next preceding iteration so as to produce convergence to a loadflow solution in successive iterations, said computer including means for determining when a solution is reached.

Claim 6

A hybrid loadflow computer arrangement with transient stability analysis capability comprising a DC analog simulator of an AC network, said simulator including a plurality of bus, generator, load, tie line and line DC circuits interconnected to correspond to the AC network, a digital computer, said digital computer including means for determining generator mechanical powers and generator terminal voltage magnitudes, first and second load admittances for each load, load real and reactive power, external tie bus voltages, and tie line real and reactive power, analog input and output systems for transferring signals between said computer and said simulator, said computer including means for generating representative signals of said generator mechanical powers and generator terminal voltage magnitudes, said first and second load admittances for each load, and said external tie bus voltages, means for applying said representative signals to corresponding generator, load and tie line DC circuits, each of said bus DC circuits including means for responding to generator, load, tie line and line phasor input current signals and for generating an output bus voltage phasor signal, each of said generator DC circuits including means for responding to the difference between generator mechanical power and generator electrical power input signals and the difference between generator terminal voltage input signals and bus voltage phasor input signals, and for generating a generator swing angle output signal and a generator phasor current output signal, each of said load DC circuits including means for responding to applied bus voltage phasor signals, means for receiving and representing said first and second load admittance signals, and means for generating a bus to load current phasor output signals, each of said tie line and line DC circuits including means for responding to the difference between applied bus voltage phasor signals and generating an output line phasor current signal in accordance with at least the equivalent series branch impedance, one of said applied bus voltage phasor signals to each of said tie line circuits being a digital computer determined external tie bus voltage signal, said digital computer including means for determining tentative real and reactive tie line and load powers as a function of corresponding external tie bus and load voltages and tie line and bus to load currents, said digital computer including means for determining whether said tentative powers are within preselected tolerances, said digital computer including means for determining in successive iterations new first and second load admittances as a function of load power and bus to load voltage values in the next preceding iteration, and for determining in successive iterations new external tie bus voltages as a function of tie line power and tie line current values in the next preceding iteration so as to produce convergence to a loadflow solution in successive iterations, said computer including means for determining when a solution is reached.

Claim 7

A machine method for making loadflow solutions for an electric power system, the steps of said method comprising determining and storing in a digital computer representations of values including unit generation mechanical powers and terminal voltage magnitudes, first and second load admittances for each load, load real and reactive powers, external tie bus voltages and tie line real and reactive powers for the system, applying representative signals of said generator mechanical powers and terminal voltage magnitudes, said first and second load admittances and said external tie bus voltages to an analog network simulator which includes DC bus, generator, load, tie line and line circuits interconnected to simulate the power system, operating the digital computer to determine representations of tentative real and reactive tie line and load powers as a function of corresponding external tie bus and load voltages, and tie line and bus to load currents, operating said digital computer to determine representations of whether said tentative powers are within preselected tolerances, operating said digital computer to determine in successive iterations representations of new first and second load admittances as a function of load power and bus to load voltage values in the next preceding iteration, and to determine in successive iterations representations of new external tie bus voltages as a function of the tie line power and tie line current values in the next preceding iteration, so as to produce convergence to a loadflow solution in successive iterations, and operating said digital computer to a representation of when a loadflow solution has been reached.

Claim 8

A machine method for making loadflow solutions for an electric power system, the steps of said method comprising determining and storing in a digital computer representations of values including unit generation mechanical powers and terminal voltage magnitudes, first and second load admittances for each load, load real and reactive powers, external tie bus voltages and tie line real and reactive powers for the system, applying representative signals of said generator mechanical powers and terminal voltage magnitudes, said first and second load admittances and said external tie bus voltages to an analog network simulator which includes DC bus, generator, load, tie line and line circuits interconnected to simulate the power system, operating the digital computer to determine representations of tentative real and reactive tie line and load powers as a function of corresponding external tie bus and load voltages, and tie line and bus to load currents, operating said digital computer to determine representations of whether said tentative powers are within preselected tolerances, operating said digital computer to determine in successive iterations representations of new first and second load admittances as a function of load power and bus to load voltage values in the next preceding iteration, and to determine in successive iterations representations of new external tie bus voltages as a function of the tie line power and tie line current values in the next preceding iteration, so as to produce convergence to a loadflow solution in successive iterations, and operating said digital computer to a representation of when a loadflow solution has been reached.