Voltage stability monitoring device and method

1. A voltage stability monitoring device which monitors voltage stability of a power system comprising:

a processor;

a memory storing a program which, when executed, causes the processor to:

produce a plurality of assumed change scenarios indicating a scenario of a change that is assumed based on at least one of a system configuration of the power system and a change of a tide state;

calculate the voltage stability using the assumed change scenario;

calculate a voltage stability margin indicating margin degree of the voltage stability, based on the voltage stability;

select an assumed change scenario with high severity of the voltage stability for each assumed change scenario, based on the voltage stability margin;

calculate which of buses in the power system is a vulnerable bus that decreases voltage stability, based on the assumed change scenario which is selected; and

change a monitoring target of the voltage stability, based on information of the vulnerable bus.

2. The voltage stability monitoring device according to claim 1 , wherein the assumed change scenario includes at least one of a failure location, a failure aspect, an assumed renewable energy change amount, and failure removal timing, as a failure case which is assumed in the power system, and includes at least one of solar power generation, wind power generation, an output change amount of mega solar or wind farm, and simultaneous drooping out of wind farm, as the assumed renewable energy change amount.

3. The voltage stability monitoring device according to claim 1 , wherein the processor calculates a change of a node voltage with respect to total demand of power system or demand of each node, and calculates at least one of a P-V curve and V-Q curve.

4. The voltage stability monitoring device according to claim 1 , wherein the P-V curve uses repetition of ti de calculation or continuation type tide calculation.

5. The voltage stability monitoring device according to claim 4 , wherein control of a step width of predictor calculation in the continuation type tide calculation determines the step width by using a binary search method or a method of increasing or decreasing the step width using at least one of the number of times of convergence calculation of modifier calculation.

6. The voltage stability monitoring device according to claim 4 , wherein, in a case where calculation of low solution of a voltage in the continuation type tide calculation is not completed, control of a step width of predictor calculation is recalculated until calculation of the low solution of a voltage is completed, by changing an integer which is an index that increases and decreases a step width according to the number of times of convergence calculation of modifier calculation.

7. The voltage stability monitoring device according to claim 1 , wherein the unit processor calculates at least one of an active power deviation or a voltage deviation between an operation point and limit power, and a reactive power deviation between a point of zero and limit power of reactive power, using a P-V curve or a V-Q curve which is calculated by the voltage stability calculation unit.

8. The voltage stability monitoring device according to claim 1 , wherein the processor determines sequence by sorting the assumed change scenarios in an ascending order of the voltage stability.

9. The voltage stability monitoring device according to claim 1 , further comprising:

a database with a threshold of the severity for selecting the assumed change scenario.

10. The voltage stability monitoring device according to claim 1 , further comprising:

a database with a threshold for selecting the vulnerable bus.

11. The voltage stability monitoring device according to claim 1 , wherein the processor determines the vulnerable bus, using a P-V curve, at least one of a voltage deviation between high solution and low solution of an operation point and a voltage change rate with respect to active power of the low solution, and the threshold.

12. The voltage stability monitoring device according to claim 1 , wherein the processor determines the vulnerable bus using a V-Q curve, a reactive power deviation between a point of zero and limit power of reactive power, and the threshold.

13. The voltage stability monitoring device according to claim 1 , wherein the processor determines a vulnerable bus which is the most vulnerable in the vulnerable buses, using at least one of voltage deviations between high solution and low solution of an operation point, a voltage change rate with respect to active power of the low solution, and reactive power deviation between a point of zero and limit power of reactive power, and displays the determined vulnerable bus on a screen of a display unit.

14. The voltage stability monitoring device according to claim 1 , further comprising:

a restriction database which is used for the vulnerable bus calculation, and includes at least one piece of restriction data of active power restriction, reactive power restriction, and power factor restriction of each node.

15. A voltage stability monitoring method of monitoring voltage stability of a power system with a voltage stability monitoring device that includes a processor and a memory storing a program which, when executed, causes the processor to execute the method comprising:

producing a plurality of assumed change scenarios indicating a scenario of a change that is assumed based on at least one of a system configuration of the power system and a change of a tide state;

calculating the voltage stability using the assumed change scenario;

calculating a voltage stability margin indicating margin degree of the voltage stability, based on the voltage stability;

selecting an assumed change scenario with high severity of the voltage stability for each assumed change scenario, based on the voltage stability margin;

calculating which of buses in the power system is a vulnerable bus that decreases voltage stability, based on the assumed change scenario which is selected; and

changing a monitoring target of the voltage stability, based on information of the vulnerable bus.