Reactive power regulation
View Patent ↗The present invention relates to a method of reactive power regulation in a wind turbine comprising a local reactive power control system adapted to operate in a central control mode and a local control mode, a method of reactive power regulation in a wind park connected to an electrical grid, and to a wind park.
1. A method of reactive power regulation in a wind park connected to an electrical grid:
the wind park comprising a plurality of wind turbines and a central reactive power control system, wherein at least a first portion of the plurality of wind turbines each comprise a local reactive power control system adapted to work in a central control mode and a local control mode, wherein
the central reactive power control system sends commands indicative of local reactive power demands to the local reactive power control systems in accordance with at least one measured variable of the grid, and wherein
in a central control mode, the local reactive power control system operates the wind turbine to generate reactive power in accordance with the commands received from the central reactive power control system, and wherein
in a local control mode, the local reactive power control system determines an amount of reactive power to be generated and controls the wind turbine to generate said amount of reactive power regardless of the commands received from the central reactive power control system.
2. A method according to claim 1 , wherein the local reactive power control system switches from the central control mode to the local control mode when a measured local variable passes a local limit value for the wind turbine.
3. A method according to claim 2 , wherein the local reactive power control system switches from the central control mode to a local control mode when a measured local variable passes a local limit value for the wind turbine during at least a predetermined period of time.
4. A method according to claim 2 , wherein said local limit value for the wind turbine is such that in normal grid conditions, the local reactive control system operates in the central control mode and that in or near exceptional grid conditions, the local reactive control system operates in the local control mode.
5. A method according to claim 2 , wherein the local limit value for each wind turbine is a voltage and the measured local variable is a local voltage.
6. A method according to claim 5 , wherein the local limit value for each wind turbine comprise a minimum and a maximum voltage.
7. A method according to claim 2 , wherein the local limit value is a constant.
8. A method according to claim 2 , wherein the local limit value is determined in accordance with at least one measured variable.
9. A method according to claim 1 , wherein in the local control mode, the amount of reactive power to be generated is the maximum or minimum amount of reactive power the wind turbine can generate.
10. A method according to claim 9 , wherein said maximum and minimum amount of reactive power the wind turbine can generate is determined in accordance with operational conditions of the wind park and/or the wind turbine.
11. A method according to claim 1 , wherein the local reactive power control system switches from the central control mode to the local control mode when an absolute value of a rate of change of a measured local variable surpasses a local limit rate.
12. A method according to claim 1 , wherein the local reactive power control system switches from the central control mode to the local control mode when a sudden change of a measured local variable surpasses local limit proportions.
13. A method according to claim 11 , wherein the measured local variable is a local voltage.
14. A method according to claim 2 , wherein the local limit value and/or local limit rates and/or local limit proportions are determined by the central reactive power control system and supplied to each of the local reactive power control systems.
15. A method according to claim 2 , wherein the local limit value and/or local limit rates and/or local limit proportions are determined by each of the local reactive power control systems.
16. A method according to claim 1 , wherein the local reactive power control systems switch from the local control mode to the central control mode after a predetermined amount of time of operating in the local control mode has passed.
17. A method according to claim 1 , wherein the local reactive power control system switches from the local control mode to the central control mode in accordance with operational conditions of the wind park and/or electrical grid and/or other wind turbines.
18. A method of reactive power regulation implemented in a local reactive power control system of a wind turbine comprising:
receiving commands indicative of a local reactive power demand from a wind park central reactive power control system,
obtaining a maximum and a minimum local voltage,
obtaining an instantaneous value of the local voltage from a measuring device and comparing said instantaneous value for the local voltage with the maximum and minimum local voltage, and
sending control commands to at least one wind turbine component for generating the maximum available inductive reactive power if the local voltage is more than the maximum voltage, and
sending control commands to at least one wind turbine component for generating the maximum available capacitive power if the local voltage is less than the minimum local voltage.
19. A method according to claim 18 , further comprising obtaining an absolute rate of change limit of a local voltage,
determining a rate of change of a local voltage based on the obtained values of the local voltage from the measuring device, and
locally determining the amount of reactive power to be generated, and sending control commands to at least one wind turbine component for generating said amount of reactive power, if an absolute determined voltage rate of change is more than an absolute rate of change limit.
20. A method according to claim 19 , further comprising sending control commands to at least one wind turbine component for generating reactive power in accordance with the commands received from the central reactive power control system if the absolute determined voltage rate of change is less than the absolute rate of change limit and the local voltage is between the maximum and the minimum local voltage.
21. A method according to claim 18 , wherein obtaining the maximum and a minimum local voltage comprises receiving the maximum and minimum local voltage from the central reactive power control system.
22. A method according to claim 18 , wherein obtaining the maximum and a minimum local voltage comprises calculating the maximum and minimum local voltage.
23. A method according to claim 18 , further comprising obtaining an absolute rate of change limit of a local voltage including receiving the absolute rate of change limit from the central reactive power control system.
24. A method according to claim 19 , wherein obtaining an absolute rate of change limit of a local voltage comprises calculating the absolute rate of change limit.
25. A non-transitory computer readable medium storing program instructions for causing a computing system of a wind turbine local reactive power control system to perform a method according to claim 18 .
26. A wind park connected to an electrical grid and comprising a plurality of wind turbines, wherein
at least a portion of the plurality of wind turbines each comprises a local reactive power control system capable of controlling the reactive power the wind turbine generates, the wind park further comprising:
a central reactive power control system capable of determining commands indicative of local reactive power demands for each of the local reactive power control systems in response to at least one measured variable of the grid, and sending the commands to the local reactive power control systems, and
the local reactive power control systems being adapted to work in a central control mode and a local control mode, wherein
in a central control mode, the local reactive power control system controls the corresponding wind turbine to generate reactive power in accordance with a command received from the central reactive power control system, and wherein
in a local control mode, the local reactive power control system determines an amount of reactive power to be generated by the corresponding wind turbine and controls the wind turbine to generate said amount of reactive power.
27. A wind park according to claim 26 , wherein the local reactive power control systems are capable of switching between the central control mode and the local control mode in response to at least one measured variable.
28. A wind park according to claim 26 , wherein the central control system can determine a reactive power demand for the wind park based on a measured grid voltage.
29. A wind park according to claim 26 , wherein the local reactive power controls are adapted to control a converter and/or a pitch system.