Hybrid analyzer for fast load flow and transient solution of power systems

Claim 2

A minimum element DC circuit for representing an electric power system transmission line in accordance with preselected stability criteria and comprising a first circuit for generating an output current signal corresponding to a first coordinate component of at least the series branch equivalent current in the actual system transmission line, said first circuit having as inputs voltage phasor signals representative of first coordinate components of actual voltages at buses to which the transmission line is connected, a second circuit for generating an output current signal corresponding to a second coordinate component of at least the series branch equivalent current in the actual system transmission line, said second circuit having as inputs voltage phasor signals representative of second coordinate components of actual voltages at said buses to which said transmission line is connected, means for representing at least the series branch impedance of the actual transmission line interconnected between said first and second circuits in accordance with said preselected stability criteria allowing for minimum element simulation.

Claim 3

The DC circuit of claim 1, wherein said first circuit input signals are different to generate said first circuit output current signal, and said second circuit inputs are different to generate said second circuit output current signal.

Claim 4

The DC circuit of claim 1, wherein said first and second circuits include amplifier means for receiving as inputs corresponding voltage phasor signals and generating as outputs corresponding output current signals.

Claim 5

The DC circuit of claim 3, wherein said amplifier means are high gain operational amplifiers.

Claim 6

The DC circuit of claim 4, wherein said output current signals are generated in accordance with the differences of corresponding input voltage phasor signals.

Claim 7

The DC circuit of claim 3, wherein said output current signals are generated in accordance with the differences of corresponding input voltage phasor signals.

Claim 8

The DC circuit of claim 1, wherein said means for representing at least the series branch equivalent impedance of said transmission line includes a plurality of gain devices for representing any combination of at least the series branch, resistance and reactance of the transmission line.

Claim 9

The DC circuit of claim 7, wherein said gain devices are set to represent preselected gains in accordance with the application of Nyquist stability criteria for all possible polarities of said coordinate components of bus voltages to assure stable circuit operation.

Claim 10

The DC circuit of claim 8, wherein only one additional amplifier means is connected to one of said gain devices dependent on the setting of said preselected gains, thereby providing for minimum element operation.

Claim 11

The DC circuit of claim 7, wherein said plurality of gain devices are potentiometers.

Claim 12

A minimum element DC circuit for representing an electric power system bus in accordance with preselected stability criteria and comprising a first circuit for generating an output voltage signal corresponding to a first coordinate component of the bus voltage at the actual system bus, said first circuit having as an input a current phasor signal representative of a first coordinate component of the net current flowing into said actual bus from system transmission lines to which the bus connects, a second circuit for generating an output voltage signal corresponding to a second coordinate component of the voltage at the actual system bus, said second circuit having as an input a current phasor signal representative of a second coordinate component of the net current flowing into said actual bus from system transmission lines, and means for representing the bus to ground admittance of the actual bus interconnected between said first and second circuits in accordance with said preselected stability criteria, allowing for minimum element simulation.

Claim 13

A minimum element DC circuit for representing an electric power system bus in accordance with preselected stability criteria and comprising a first circuit for generating an output voltage signal corresponding to a first coordinate component of the bus voltage at the actual system bus, said first circuit having as an input a current phasor signal representative of a first coordinate component of the net current flowing into said actual bus from system transmission lines to which the bus connects, a second circuit for generating an output voltage signal corresponding to a second coordinate component of the voltage at the actual system bus, said second circuit having as an input a current phasor signal representative of a second coordinate component of the net current flowing into said actual bus from system transmission lines, and means for representing the bus to ground admittance of the actual bus interconnected between said first and second circuits in accordance with said preselected stability criteria, allowing for minimum element simulation.

Claim 14

The DC circuit of claim 11, wherein said first and second circuits include amplifier means for receiving as inputs corresponding current phasor signals and generating as outputs corresponding output voltage signals.

Claim 15

The DC circuit of claim 12, wherein said amplifier means are high gain operational amplifiers.

Claim 16

The DC circuit of claim 12, wherein said first and second circuits include means for establishing proportional plus integral control connected across each of said amplifier means to provide low proportional gain for a high damped response and to bring any steady state error towards zero.

Claim 17

The DC circuit of claim 11, wherein said means for representing the bus to ground admittance of the actual bus includes a plurality of gain devices for representing any combination of the bus to ground conductance and susceptance of the bus.

Claim 18

The DC circuit of claim 15, wherein said gain devices are set to represent preselected gains in accordance with the application of a Nyquist stability criteria for all possible polarities of said first and second coordinate components of net current, to assure stable circuit operation.

Claim 19

The DC circuit of claim 15, wherein said plurality of gain devices are digital to analog multipliers, the values of which are set digitally.

Claim 20

The DC circuit of claim 15, wherein the selection of combinations of bus to ground conductances and susceptances are chosen in dependence upon the type of bus to be represented.

Claim 21

The DC circuit of claim 18, wherein said means for establishing proportional plus integral control includes a serial combination of resistance and capacitance adjustable for desired performance.

Claim 22

A hybrid load flow computer arrangement for generating electric power system load flow solutions, and comprising a digital computer, connected to an analog network simulator, said analog network simulator including a plurality of DC circuit modules for representing system transmission lines and buses, said transmission line modules connected to preselected bus modules through nodal equation circuitry, each of said transmission line modules including first and second circuits for receiving corresponding signals representing differences between first coordinate components and second coordinate components of actual voltages at buses to which the transmission line is connected, and generating first and second coordinate component current signals representing actual components of transmission line current and means for representing at least the series branch impedance of the actual transmission line interconnected between said first and second circuits in accordance with preselected stability criteria allowing for minimum element simulation, each of said bus modules including first and second circuits for receiving first and second coordinate components of net current into the actual bus and generating first and second coordinate component voltage signals representing components of actual bus voltage and means for representing the bus to ground admittance of the actual bus interconnected between said first and second circuits of said bus modules in accordance with preselected stability criteria, said nodal equation circuitry receiving coordinate component current signals from said transmission line modules and generating net current signals as inputs to said bus modules, said digital computer providing preselected parameter values to said simulator, storing bus voltage values and net current values from said simulator, and operating to guide the analog simulator to a load flow solution through digital to analog adjustment of said bus module admittance representing means in accordance with preselectEd load flow solution relationship between bus voltages and line currents.

Claim 23

A hybrid load flow computer arrangement for generating electric power system load flow solutions, and comprising a digital computer, connected to an analog network simulator, said analog network simulator including a plurality of DC circuit modules for representing system transmission lines and buses, said transmission line modules connected to preselected bus modules through nodal equation circuitry, each of said transmission line modules including first and second circuits for receiving corresponding signals representing differences between first coordinate components and second coordinate components of actual voltages at buses to which the transmission line is connected, and generating first and second coordinate component current signals representing actual components of transmission line current and means for representing at least the series branch impedance of the actual transmission line interconnected between said first and second circuits in accordance with preselected stability criteria allowing for minimum element simulation, each of said bus modules including first and second circuits for receiving first and second coordinate components of net current into the actual bus and generating first and second coordinate component voltage signals representing components of actual bus voltage and means for representing the bus to ground admittance of the actual bus interconnected between said first and second circuits of said bus modules in accordance with preselected stability criteria, said nodal equation circuitry receiving coordinate component current signals from said transmission line modules and generating net current signals as inputs to said bus modules, said digital computer providing preselected parameter values to said simulator, storing bus voltage values and net current values from said simulator, and operating to guide the analog simulator to a load flow solution through digital to analog adjustment of said bus module admittance representing means in accordance with preselectEd load flow solution relationship between bus voltages and line currents.

Claim 24

The hybrid load flow computer arrangement of claim 20, wherein each of said first and second circuits of said transmission line modules include amplifier means for receiving said corresponding signals representing differences between first coordinate components and second coordinate components of actual bus voltages and generating corresponding output current signals.

Claim 25

The hybrid computer arrangement of claim 21, wherein said amplifier means are high gain operational amplifiers.

Claim 26

The hybrid computer arrangement of claim 21, wherein said means for representing at least the series branch of equivalent impedance of each of said transmission lines includes a plurality of gain devices for representing any combination of at least the series branch resistance and reactance of the transmission line.

Claim 27

The hybrid computer arrangement of claim 23, wherein said transmission line gain devices are set to represent preselected gains in accordance with the application of Nyquist stability criteria for all possible polarities of said coordinate components of bus voltages to assure stable circuit operation.

Claim 28

The hybrid computer arrangement of claim 24, wherein only one additional amplifier means is connected to one of said gain devices, dependent on the setting of said preselected gains, thereby providing for minimum element operation.

Claim 29

The hybrid computer arrangement of claim 23, wherein said plurality of gain devices are potentiometers.

Claim 30

The hybrid computer arrangement of claim 20, wherein each of said first and second circuits of said bus modules include amplifier means for receiving corresponding coordinate component signals of net bus current and generating corresponding output voltage component signals.

Claim 31

The hybrid computer arrangement of claim 27, wherein said amplifier means are high gain operational amplifiers.

Claim 32

The hybrid computer arrangement of claim 27, wherein said means for representing the bus to ground admittance of each bus includes a plurality of gain devices for representing any combination of bus to ground conductance and susceptance.

Claim 33

The hybrid computer arrangements of claim 29, wherein said bus gain devices are set to represent preselected gains in accordance with the application of Nyquist stability criteria for all possible polarities of said coordinate components of net bus current, to assure stable circuit operation.

Claim 34

The hybrid computer arrangement of claim 29, wherein said plurality of bus gain devices are digital to analog multipliers, the values of which are set by said digital computer through digital to analog channel devices connected from said digital computer to said analog simulator bus modules.

Claim 35

The hybrid computer arrangement of claim 27, wherein each of said first and second circuits of said bus modules include means for establishing proportional plus integral control connected across each of said amplifier means to provide low proportional gain for a high damped response and to bring any steady state error towards zero.

Claim 36

The hybrid computer arrangement of claim 32, wherein said means for establishing proportional plus integral control includes a serial combination of resistance and capacitance adjustable for desired performance.

Claim 37

The hybrid computer arrangement of claim 20, wherein said digital computer receives values of net bus currents and bus voltage components through analog to digital multiplexing means connected from bus module circuitry and nodal equation circuitry to said digital computer.

Claim 38

The hybrid computer arrangement of claim 20, wherein said nodal equation circuitry includes a plurality of capacitor means for receiving first transmission line component current signals and generating first coordinate components of net bus current for transmission lines connected to a corresponding bus, and for receiving second transmission line component current signals and generating secOnd coordinate components of net bus current for transmission lines connected to said corresponding bus.

Claim 39

The hybrid computer arrangement of claim 20, wherein one of said bus modules is chosen as a slack or reference bus.