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EP-4740286-A1 - CONTROL SYSTEM PROVIDING DROOP CONTROL AND WIND TURBINE

EP4740286A1EP 4740286 A1EP4740286 A1EP 4740286A1EP-4740286-A1

Abstract

A control system for reducing a power imbalance in a power grid (200) is provided. The control system (10) is configured to control the operation of a power converter (150), the power converter (150) being configured to convert electrical power of a power source (110) and to provide the converted electrical power to the power grid (200). The control system (10) comprises a droop control, wherein the droop control comprises a first droop control circuit (20) configured to adjust the output power of the power converter (150) in dependence on a first frequency deviation (Δf, Δf1) between a frequency reference (f Ref ) and a first monitored frequency (f M , f M1 ) and a second droop control circuit (40) configured to adjust the output power of the power converter (150) in dependence on a second frequency deviation (Δf, Δf2) between the frequency reference (f Ref ) and the first monitored frequency (f M , f M1 ) or a second monitored frequency (f M2 ). The first droop control circuit (20) operates at a first operation speed higher than an operation speed of the second droop control circuit (40).

Inventors

  • BROGAN, PAUL BRIAN
  • ELLIOTT, DOUGLAS
  • KNUEPPEL, THYGE

Assignees

  • Siemens Gamesa Renewable Energy A/S

Dates

Publication Date
20260513
Application Date
20240801

Claims (13)

  1. 1. A control system for reducing an active power imbalance in a power grid (200) , wherein the control system (10) is configured to control the operation of a power converter (150) , the power converter (150) being configured to convert electrical power of a power source (110) and to provide the converted electrical power to the power grid (200) , wherein the control system (10) comprises a droop control, wherein the droop control comprises: a first droop control circuit (20) configured to adjust the active output power of the power converter (150) in dependence on a first frequency deviation (Af, Afl) between a frequency reference (f Re f) and a first monitored frequency (f M , fni) , wherein the first monitored frequency is indicative of a frequency of electrical power provided by the power converter (150) and/or a frequency of the power grid (200) ; and a second droop control circuit (40) configured to adjust the active output power of the power converter (150) in dependence on a second frequency deviation (Af, Af2) between the frequency reference (f Re f) and the first monitored frequency (f M , fni) or a second monitored frequency (f M2 ) , wherein the second monitored frequency ( f MR ) is indicative of a frequency of electrical power provided by the power converter (150) and/or a frequency of the power grid (200) , wherein the first droop control circuit (20) operates at a first operation speed and wherein the second droop control circuit (40) operates at a second operation speed, the first operation speed being higher than the second operation speed, wherein the control system (10) is configured to operate at least in a grid supporting mode and/or in a grid forming mode to support the power grid (200) , wherein the control system (10) is configured to provide said droop control at least during the grid supporting mode and/or during the grid forming mode, respectively, wherein the control system is configured to operate the power converter (150) as a virtual synchronous generator when operating the power converter (150) in the grid supporting mode and/or in the grid forming mode .
  2. 2. The control system according to claim 1, wherein the first droop control circuit (20) is configured to receive an adjusted power reference (P A ) for an output power of the power converter (150) from the second droop control circuit (40) and to apply thereto a first power offset (API) using droop control based on the first frequency deviation (Af, Afl) , and wherein the second droop control circuit (40) is configured to generate the adjusted power reference (P A ) by receiving a power reference (P re f) for an output power of the power converter (150) and applying thereto a second power offset (AP2) using droop control based on the second frequency deviation (Af, Af2) .
  3. 3. The control system according to claim 1 or 2, wherein the first droop control circuit (20) and the second droop control circuit (40) employ separate droop functions (21, 41) to generate a respective first power offset and a second power offset from the first frequency deviation (Afl) and the second frequency deviation (Af2) , respectively, or wherein the first frequency deviation (Af) is identical to the second frequency deviation (Af) and the first droop control circuit (20) and the second droop control circuit (40) use the same droop function (21, 41) to generate a power offset (AP) from the frequency deviation (Af ) , the power offset being employed by both the first droop control circuit (20) and the second droop control circuit (40) to provide said droop control.
  4. 4. The control system according to any of the preceding claims, wherein the control system (10) is configured to limit the adjustment of the output power of the power converter (150) by the first droop control circuit (20) at an amplitude of the first frequency deviation or at a rate of change or frequency of change of the first frequency deviation at which the second droop control circuit (40) is operable to adjust the output power of the power converter (150) .
  5. 5. The control system according to claim 4, wherein the first control circuit (20) comprises a high pass filter to filter the first frequency deviation or a power offset generated from the first frequency deviation, or comprises a low pass filter (32) to filter the first frequency deviation or a power offset (AP) generated from the first frequency deviation and a summation node (33) to subtract the filtered quantity from the first frequency deviation or from the generated power offset, respectively, and/or wherein the first control circuit (20) comprises a filter (26) configured to pass the first frequency deviation only if its amplitude exceeds a predetermined threshold.
  6. 6. The control system according to any of the preceding claims, wherein the first droop control circuit (20) is configured to apply a power offset (API) to generate an adjusted power reference (PAA) for an output power of the power converter (150) , wherein the first droop control circuit (20) comprises a limiter (23) configured to limit positive and/or negative changes to the adjusted power reference by the power offset (API) to a respective maximum value, wherein preferably, the limiter (23) is configured to limit the adjusted power reference to a maximum output power that the power converter (150) can provide based on an electrical power made available by the power source (110) and/or to limit a power reduction of the adjusted power reference to a maximum value.
  7. 7. The control system according to any of the preceding claims, wherein the control system (10) comprises a converter controller (120) configured to control a modulation of power electronic switches of the power converter (150) , wherein the first droop control circuit (10) is implemented in the converter controller (120) .
  8. 8. The control system according to any of the preceding claims, wherein the control system (10) comprises a power generation system controller (140) , wherein the power generation system controller (140) is configured to control the operation of the power source (110) , and wherein at least part of the second droop control circuit (40) is implemented in the power generation system controller (140) .
  9. 9. The control system according to claim 8, wherein the power generation system controller (140) is configured to control a speed and/or an output power of the power source (110) , wherein the power generation system controller (140) comprises a power reference controller (141, 51) configured to adjust or limit an adjusted power reference generated by the second droop control circuit (40) in dependence on an operation parameter of the power source (110) .
  10. 10. The control system according to claim 8 or 9, wherein the power source (110) is a power generation system of a wind turbine (100) , and wherein the power generation system controller (140) is a wind turbine controller or wherein the power generation system controller (140) is a wind farm controller configured to supply a power reference to the wind turbine (100) .
  11. 11. A wind turbine comprising a power source (110) in form of a power generation system and comprising a power converter (150) configured to convert electrical power provided by the power source (110) and to provide the converted electrical power to a power grid (200) , wherein the wind turbine (100) comprises a control system (10) according to any of the preceding claims, the control system (10) controlling the power converter (150) .
  12. 12. A method of controlling the operation of a power converter (150) to reduce an active power imbalance in a power grid (200) , the power converter (150) being configured to convert electrical power of a power source (110) and to provide the converted electrical power to the power grid (200) , wherein the method comprises: adjusting, by a first droop control circuit (20) , the active output power of the power converter (150) in dependence on a first frequency deviation (Af, Afl) between a frequency reference and a first monitored frequency (f M , fni) , wherein the first monitored frequency (f M , fni) is indicative of a frequency of electrical power provided by the power converter (150) and/or a frequency of the power grid (200) ; and adjusting, by a second droop control circuit (40) , the active output power of the power converter (150) in dependence on a second frequency deviation (Af, Af2) between the frequency reference and the first monitored frequency (f M , fni) or a second monitored frequency ( f M2 ) , wherein the second monitored frequency (f M2 ) is indicative of a frequency of electrical power provided by the power converter (150) and/or a frequency of the power grid (200) , wherein the first droop control circuit (20) operates at a first operation speed and wherein the second droop control circuit (40) operates at a second operation speed, the first operation speed being higher than the second operation speed, wherein the method operates the power converter at least in a grid supporting mode and/or in a grid forming mode to support the power grid (200) , wherein the method provides said droop control at least during the grid supporting mode and/or during the grid forming mode, respectively, wherein the method operates the power converter (150) as a virtual synchronous generator when operating the power converter (150) in the grid supporting mode and/or in the grid forming mode .
  13. 13. A computer program for operating a control system configured to control the operation of a power converter (150) , the power converter (150) being configured to convert electrical power of a power source (110) and to provide the converted electrical power to the power grid (200) , wherein the computer program comprises control instructions which, when executed by a processing unit of the control system (10) , causes the processing unit to perform the method of claim 12.

Description

Description Control System Providing Droop Control and Wind Turbine FIELD OF THE INVENTION The present invention relates to a control system for reducing a power imbalance in power grid, wherein the control system comprises a droop control . It further relates to a wind turbine comprising such control system, to a method of controlling a power converter, and to a respective computer program . In an electrical power grid, to keep the frequency of the electrical power constant , the electrical power drawn by loads from the power grid should be in balance with the electrical power provided into the power grid by power sources , such as power plants . Several conditions exist in which such balance may become disturbed . For example , an additional load may draw power from the grid, or a load or a power source may be disconnected from the grid . In particular in island networks in which a predetermined limited number of power sources feed power into the grid, and in electrical islands that may for example result from disconnecting a part of a power grid from a main grid ( e . g . due to a fault or the like ) , such changes in the electrical power drawn from the grid or provided into the grid may result and relatively large changes of grid frequency . An increasing frequency indicates a power surplus , whereas a declining frequency indicates a power deficit in the respective power grid . The speed or rate by which the frequency changes ( the so-called rate of change of frequency, RoCoF) is related to the si ze of the power imbalance AP relative to the inertia of the system : df/dt = AP * f0 / ( 2 * H * SBase ) = RoCoF wherein f0 is the nominal grid frequency, H the inertial constant of the system and S the base load at disconnection . When one or more wind turbines (WT ) are operating in and supporting an electrical island, the wind turbine or wind farm must automatically change its power output to support the load balance . A solution to the problem of providing a respective power balance by a wind farm is provided in the document WO 2019/ 166290 Al , wherein the power provided by the individual wind turbines of the wind farm is allowed to vary and will be di f ferent (unless there is wind for full power production) , wherein the distributed nature of wind turbines within the wind farm is considered . In particular, not all wind turbines must contribute equally to the load balance as long as the sum of the power output of the wind turbines balances the load on the electrical island . In the prior art solutions , load changes on an electrical island are however still a challenge . In particular, the reaction to a large sudden power imbalance , such as the disconnection of a large load or of a generator (which may for example be tripped due to a fault ) still generates challenges . This in in particular the case for situations in which wind turbines or other converter-based power sources feed electrical power into the power grid . As a result , the imbalance in the power grid may cause the electrical frequency to deviate signi ficantly from the desired value , such as from a desired 50 Hz or 60 Hz grid frequency, which may result in the triggering of protection mechanisms . Document US 2020/ 176993 Al discloses a connecting structure , which can be coupled to an electric supply grid . The connecting structure comprises a voltage-impressing unit , which has an inverter that generates a voltage at its output , and a current-impressing unit , which has a current-impressing inverter that controls to an output current . Document US 2022 / 0140602 Al discloses a method for controlling frequency-converter-based infeeders . The frequency-converter-based infeeders have di f ferent droops , i . e . control characteristics in dependence on the grid voltage . The di f ferent infeeders can be reali zed as di f ferent wind turbines . The di f ferent droops overlap to form a total droop . Document KR 20140048395 A outlines a method and apparatus for controlling distributed energy sources by measuring output and frequency and calculating droop coef ficients to determine load distribution . This enables power control and independent operation when disconnected from the main grid . The use of variable droop characteristics improves control near the generators ' output limits . SUMMARY Accordingly, there is a need to mitigate at least some of the drawbacks outlined above and to provide an improved way of balancing the electrical power in a power grid . This need is met by the features of the independent claims . The dependent claims describe embodiments and/or examples of the invention . According to an aspect , a control system for reducing a power imbalance in a power grid is provided . The control system is configured to control the operation of a power converter, wherein the power converter is configured to convert electrical power of a power source and to provide the converted electrical power to the power grid . The contro