Description:FORM 2

THE PATENTS ACT, 1970
(39 of 1970)
AND
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)

1. TITLE OF THE INVENTION:

“METHOD FOR CONTROLLING RENEWABLE ENERGY PARK”
2. APPLICANT:

(a) Name : Suzlon Energy Limited
(b) Nationality : Indian
(c) Address : Shrimali Society, Near Shri Krishna
Complex, Navrangpura, Ahmedabad 380 009, Gujarat, India

3. PREAMBLE TO THE DESCRIPTION:

The following specification particularly describes the invention and the manner in which it is to be performed.
TITLE OF INVENTION

METHOD FOR CONTROLLING RENEWABLE ENERGY PARK

FIELD OF INVENTION

The present invention is directed to a method for controlling renewable energy park, a method for operating a renewable energy park, a renewable energy park controller for performing the method for controlling renewable energy park and a renewable energy park comprising the renewable energy park controller.

BACKGROUND

It is known from prior art that power grids inside of renewable energy plants con-nect individual wind turbine generators of a wind power plant or photovoltaic generators of a solar farm to a point of common coupling (PoCC) - where all generated power is collected. The point of control (PoC) can be at this point of common coupling or at a remote Point of Interconnection (POI) where the wind or solar power feeds into the transmission lines. In order to control the power at Point of Interconnection (POI) the impedance of the power grid between PoCC of the wind and/or solar park and the Point of Interconnection (POI) has to be taken into consideration. Especially as the point of interconnection often is where the renewable energy park has to fulfill the requirement in the grid code, i.e. grid connection specification.

The impedance of the power lines connecting PoCC of the renewable energy park to the POI causes non-linear relation between power at PoCC and POI, as the power lines supply reactive power when lightly loaded and absorb reactive power when fully loaded.

Wind and solar power parks are often controlled by a park controller connected at PoCC where the measurement of electrical parameters is done. The park con-troller controls and communicates with the wind turbines and other components in the wind power park or with the solar generator in PV parks. In order to control the wind turbines or solar generators some measured electrical parameters are needed. The power park controller and the measurement sensors may be located remotely from the point of interconnection (POI), where the control applies, so due to the impedance in the grid the controlled parameters are not the same at the point of measurement at PoCC and the point of interconnection. It may be seen as an object of the embodiments of the present invention to provide a power plant controller that ensures proper values of electrical parameters in a point different from the point of measurement and even to have a smooth control transfer and stable operation in case of communication failures between power meter at POI and power plant controller.

Typically measurement and control of grid parameter of renewable energy re-sources such as wind parks or solar parks is accomplished by a renewable energy park controller at the pooling substation at PoCC where a number of individual units are electrically connected and jointly controlled by the renewable energy park controller. Typically pooling substation at PoCC is situated at remote loca-tions with long connecting high voltage (HV) or medium voltage (MV) lines to a point of interconnection (POI) to the transmissions grid. According to IEV 601-01-28 the boundaries between medium- and high-voltage levels overlap and de-pend on local circumstances and history or common usage. Nevertheless the band 30 kV to 100 kV frequently contains the accepted boundary between medium and high voltage.

A transmission system operator demands control of voltage and frequency at point of interconnection (POI) where grid parameter need to be maintained with-in a limited, defined range to ensure continuous stable and balanced operation of renewable energy resources and utility grid.

OBJECT OF THE INVENTION

Line losses along the connecting high voltage (HV) or medium voltage (MV) lines between pooling substation at PoCC and point of interconnection vary with actual power generation, line parameters and other conditions. This leads to dif-ferent voltages at pooling substation and point of interconnection. Further the voltage deviation is not constant; it varies with generation and other conditions. To keep the grid in stable operating conditions the voltage needs to be main-tained at a desired level at point of interconnection through reactive power con-trol.

There are two disadvantages with the prior art:
1. In many cases a direct measurement at point of interconnection is not available or cannot be accessed for various reasons.
2. Even if a measurement at point of interconnection is available, a fallback solution for communication delays or interruptions due to network faults is required for smooth control transfer and stable operation of power grid.

It is an object of the present invention to overcome these disadvantages.

SUMMARY OF THE INVENTION

An aspect of the present invention to solve the above-mentioned object is di-rected to a method for controlling renewable energy park comprising at least two renewable energy resources. The method comprises the steps of:
- measuring a power output of renewable energy park at point of measure-ment,
- obtaining at least one required utility grid parameter at point of inter-connection,
- determining electrical power offset based on line losses between point of measurement and point of interconnection for compensating the line loss-es and for matching with required utility grid parameter, and
- adding an electrical power offset to a control set point of the at least one renewable energy resource at a renewable energy park controller for con-trolling the at least one renewable energy resource.

This method overcomes the disadvantages of the prior art without adding addi-tional hardware. At the same time grid code compliance of the renewable energy park is provided at point of interconnection. This method can be applied in new installed renewable energy parks as well as in existing ones without the need to install additional equipment. Furthermore this method gives an opportunity for a smooth fallback control and stable operation in renewable energy parks with me-tering at point of interconnection when the network communication fails. When measuring a power output of renewable energy park at POI, using the calculated offset during fallback mode to ensure smooth transfer of control and stable operation of control.

According to a preferred embodiment of the method for controlling renewable energy park comprising at least two renewable energy resources, the method fur-ther comprises the step of calculating line losses based on measurement and at least one line parameter of a high voltage (HV) or middle voltage (MV) line con-necting pooling substation and POI.

According to a more preferred embodiment of the method of controlling renewa-ble energy park the at least one line parameter for calculating line losses is re-sistance, impedance, susceptance or length or a combination thereof. Advanta-geously, for calculating line losses the line parameters resistance, impedance, susceptance and length will be used.

According to a preferred embodiment of the method of controlling renewable energy park, electrical power is active power and/or reactive power.

According to a preferred embodiment of the method of controlling a renewable energy park; the method further comprises the step of calculating the at least one grid parameter at point of interconnection.

According to a preferred embodiment of the method of controlling a renewable energy park; wherein the at least one grid parameter comprises grid voltage at point of interconnection (POI), power factor at point of interconnection (POI) and/or reactive power at point of interconnection (POI).

Another aspect is directed to a renewable energy park controller for performing said method for controlling the renewable energy park. The renewable energy park controller comprises a measuring unit for measuring a power output of the renewable energy park at the point of measurement, an obtaining unit for obtain-ing at least one required utility grid parameter at the point of interconnection, a determination unit for determining an electrical power offset based on line losses between the point of measurement and the point of interconnection for compen-sating the line losses and for matching with required utility grid parameter, and a summation unit for adding the electrical power offset to a control set point of the at least one renewable energy resource at a renewable energy park controller for controlling the at least one renewable energy source.

According to a preferred embodiment of the renewable energy park controller, the controller is a renewable energy park controller connected to each of the re-newable energy resources.

Another aspect of the present invention is directed to a method for operating a renewable energy park comprising said renewable energy park controller per-forming the method for controlling renewable energy park.

According to a preferred embodiment of the method for operating a renewable energy park, the method further comprises the step of operating at least one of the renewable energy resources with power offset to compensate line losses.

According to a more preferred embodiment of the method for operating a renew-able energy park, wherein operating at least one of the renewable energy re-sources with reactive power offset.

Another aspect of the present invention is directed to a renewable energy park. This comprises said renewable energy park controller and at least two renewable energy resources.

According to a preferred embodiment of the renewable energy park, this com-prises at least one wind turbine park having at least one wind turbine, photovolta-ic park having at least one photovoltaic device, biomass park having at least one biomass device or hydro park having at least one hydro device or a combination thereof as renewable energy resource.

Another aspect of the present invention is directed to a computer program prod-uct which comprises instructions which, when the program is executed by a com-puter, cause the computer to carry out the steps of said method for controlling renewable energy park.

The present invention serves several advantages, namely:

- Stabilized grid voltage at point of interconnection to ensure grid code compliance of renewable energy generating park where control is re-quested by transmission system operator;
- No need for additional equipment which saves costs;
- Can be updated in any existing renewable energy park;
- Fast, real time measurement with built-in power meter at pooling substa-tion are used for offset calculations, no additional network connection re-quired;
- Does not require a back-up procedure for disturbed connection to point of interconnection meter;
- Can form a back-up for safe, smooth transfer of control at point of inter-connection without having access to measurement devices at point of in-terconnection;
- Possible increase in revenue by stabilized generation thus reducing the need for curtailment or generation stop;
- Possible increased generation by avoiding or reducing precautionary wind farm curtailments due to lack of metering at point of interconnection in existing wind or solar farms.

BRIEF DESCRIPTION OF DRAWINGS

The invention will now be explained in more detail with respect to exemplary embodiments with reference to the enclosed drawings, wherein:

Figure 1 shows a wind turbine (prior art),

Figure 2 shows a renewable energy park comprising a plurality wind turbines;

Figure 3 shows a hybrid renewable energy park comprising different energy resources and

Figure 4 shows a flow diagram of the method according to the pre-sent invention.

The foregoing and other aspects will become apparent from the following de-tailed description of the invention when considered in conjunction with the ac-companying drawing figures.

DETAILED DESCRIPTION OF THE INVENTION

Figure 1 depicts a schematic view of a wind turbine 1 with a tower 2 and a na-celle 3. Depending on given requirements the wind turbine 1 can be used for off-shore or onshore applications. The nacelle 3 is rotatable mounted on the tower 2 which is indicated by a double arrow at the tower 2. The nacelle 3 incorporates a number of components like a drive train chain 4 comprising a rotor shaft 5 (also known as slow-speed-shaft) connecting a rotor 6 with a gear box 7. A high-speed-shaft 8 connects the gear box 7 with a generator 9. The generator 9 is connected with a plurality of electrical components indicated by box 10. Further the nacelle 3 comprises a yaw system 11 for rotating the nacelle 3 indicated by double arrow at tower 2. The rotor 6 comprises three rotor blades 12 which are mounted to a hub body (not shown). Latter is connected to the rotor shaft 5 of the drive train chain 4. The rotor blades 12 are adjustably mounted on the hub body indicated by double arrows at the rotor blade 12. This is realized by means of pitch drives 13, said pitch drives (not shown) being part of a pitch system 13. The pitch system controls the rotor speed to given set points. By means of pitch-drives, the rotor blades 12 may be moved about a rotor blade axes into different pitch positions which is indicated by double arrows at the rotor blade 13. Said rotor blade 6 axis extends in an axial direction of the rotor blades 13. Each rotor blade 13 is con-nected to the hub body via its blade bearing (not shown). The nacelle 3 is covered by a nacelle cover 14. The hub body is covered by a spinner 15, wherein the hub body and spinner 11 forming a hub 16.

Figure 2 depicts a renewable energy park 17 comprising a plurality wind turbines 1. Each wind turbine 1 is electrically connected via an associated transformer 18 to a pooling substation 19. Latter comprises a connection point 20 for connecting power output of all wind turbines 1 and a renewable energy park controller 21. The pooling substation 19 further comprises a transformer 22 at PoCC, and a point of measurement 30 is preferably at the high voltage side, but can also be at the low voltage side and is in signal connection with the renewable energy park controller 21. The renewable energy park controller 21 measures the combined generation of all wind turbines 1 at PoCC, and is controllably connected to each wind turbine 1. Further the transformer 22 is electrically connected to a point of interconnection 23. In context of this disclosure the point of interconnection 23 is the point where the transmission system operator overtakes the control of electri-cal parameters.

Between the point of measurement 30 and point of interconnection can be a dis-tance up to several hundred kilometres. This leads to the disadvantages that in many cases a direct measurement at point of interconnection is not available or cannot be accessed for various reasons. Even if a measurement at point of inter-connection is available, there might be communication failures/delays.

Facing this challenge the inventors came to the conclusion if transmission line impedance between the point of measurement 30 and point of interconnection 23 is known then the renewable energy park 17 can be operated with a power offset to compensate line losses caused by transmission line impedance.

For this the renewable energy park controller 21 comprises a measuring unit 24 which continuously measures the power output of renewable energy park 17 at point of measurement 30, an obtaining unit 25 which obtains at least one required utility grid parameter at point of interconnection 23, a determination unit 26 which determines electrical power offset based on line losses between point of measurement 30 and point of interconnection 23 for compensating the line losses and for matching with required utility grid parameter, and summation unit 27 which provides electrical power offset to a control set point of the at least one wind turbine 1 at a renewable energy park controller 21 for controlling the at least one wind turbine 1.

The measuring unit 24 measures the power output as well as electrical parame-ters like voltage and/or current of the renewable energy park 17. By obtaining via the obtaining unit 25 at least one line parameter of a high voltage (HV) or middle voltage (MV), like resistance, impedance, susceptance or a combination thereof the calculation of line losses can be executed. Latter based on measured electri-cal parameters like voltage or current or a combination thereof of the renewable energy park 17 and at least one obtained line parameter of a high voltage (HV) or middle voltage (MV) line connecting to the pooling substation 19. Furthermore the length between the point of measurement 30 and the point of interconnection 23 will be considered to calculate line losses. With these line losses together with the measured power output of the renewable energy park 17 the provided power at the point of interconnection 23 can be calculated. This calculated power output at point of interconnection 23 can be compared with the required power output at the point of interconnection 23 for the utility grid. The electrical power output is active power and reactive power. The difference between calculated and required power output determines the electrical power offset via the determination unit 26. At the summation unit 27 the electrical power offset will be added to the electrical power setpoint of at least one wind turbine 1. The electrical power off-set and number of wind turbines 1 depends on the difference between provided and required power output at the point of interconnection 23. The bigger the dif-ference is the bigger is the required electrical power offset. The electrical power offset can be provided by increasing number of wind turbines 1 with higher pow-er output.

In the following, based on Figure 3 it should be explained a further embodiment of the present invention. Components described before which have the same functions, but differs under constructions, are numbered with an “a”.

Figure 3 depicts a hybrid energy park 17a comprising at least one wind turbine 1, at least one photovoltaic device 28 and at least one biomass device 29 or any other electric energy resource. Each wind turbine 1 is electrically connected via an associated transformer 18 to a pooling substation 19a. Each photovoltaic de-vice 28 is electrically connected via an associated transformer 18a to a hybrid pooling substation 19a. Each biomass device 29 is electrically connected via an associated transformer 18b to a pooling substation 19a. Latter comprises a hybrid connection point 20a for connecting power output of all wind turbines 1, all pho-tovoltaic devices 28 and all biomass devices 29 and a hybrid park controller 21a. The hybrid pooling substation 19a further comprises a transformer 22 and a point of measurement 30. Latter is preferably arranged at the high voltage side, but can also be at the low voltage side, and is in signal connection with the hybrid park controller 21a, which is also controllably connected to each wind turbine 1, each photovoltaic device 28 and biomass device 29. Further the transformer 22 is elec-trically connected to a point of interconnection 23. In context of this disclosure the point of interconnection 23 is the point where the transmission system opera-tor overtakes the control of electrical parameters.

Between the point of measurement 30 and point of interconnection can be a dis-tance of up to several hundred kilometres. This leads to the disadvantages that in many cases a direct measurement at point of interconnection is not available or cannot be accessed for various reasons. Even if a measurement at point of inter-connection is available, there might be communication failures/delays.

Facing this challenge the inventors come to the conclusion if transmission line impedance between the point of measurement 30 and point of interconnection 23 is known then the hybrid energy park 17a can be operated with a power offset to compensate line losses caused by transmission line impedance.

For this the hybrid energy park controller 21a comprises a measuring unit 24 which measures the power output of a hybrid energy park 17a at the point of measurement 30, an obtaining unit 25 which obtains at least one required utility grid parameter at the point of interconnection 23, a determination unit 26 which determines the electrical power offset based on line losses between the point of measurement 30 and the point of interconnection 23 for compensating the line losses and for matching with required utility grid parameter, and a summation unit 27 which provides an electrical power offset to a control set point of the at least one wind turbine 1, to the at least one photovoltaic device 28 and/or to the at least one biomass device 29 at the hybrid park controller 21a.

The measuring unit 24 measures the power output as well as electrical parame-ters like voltage and/or current of the hybrid energy park 17a. By obtaining via the obtaining unit 25 at least one line parameter of a high voltage (HV) or middle voltage (MV), like resistance, impedance, susceptance or a combination thereof the calculation of line losses can be executed. Latter based on measured electri-cal parameters like voltage or current or a combination thereof of the hybrid en-ergy park 17a and at least one obtained line parameter of a high voltage (HV) or middle voltage (MV) line connecting to the hybrid pooling substation 19a. Fur-thermore the length between the point of measurement 30 and the point of inter-connection 23 will be considered to calculate line losses. With these line losses together with the measured power output of the hybrid energy park 17a the pro-vided power at the point of interconnection 23 can be calculated. This calculated power output at the point of interconnection 23 can be compared with the re-quired power output at the point of interconnection 23 for the utility grid. The electrical power output is active power and reactive power. The difference be-tween calculated and required power output determines the electrical power off-set via the determination unit 26. At the summation unit 27 the electrical power offset will be added to the electrical power setpoint of at least one wind turbine 1, at least one photovoltaic device 28 and/or biomass device 29. The electrical power offset and number of wind turbines 1, photovoltaic devices 28 and/or bio-mass devices 29 depends on the difference between provided and required power output at the point of interconnection 23. The bigger the difference is the bigger is the electrical power offset and the number of wind turbines 1, photovoltaic devices 28 and/or biomass devices 29 with higher power output.

Figure 4 depicts a flow diagram of method for controlling renewable energy park 17, 17a comprising at least two renewable energy resources 1, 28, 29. The meth-od according to the present invention works for the renewable energy park 17 or the hybrid energy park 17a in same way. This method also works for controlling a hybrid power plant comprising of at least two different types of power plants including a renewable-energy park having at least one wind turbine 1 and a re-newable-energy park having at least one photovoltaic device 28.

In general the in following described method works for renewable energy parks as well as for hybrid energy parks which are also under the scope of protection of the present invention. The method will be described with embodiment of a re-newable energy park 17, but the same works in same way for a hybrid energy park 17a. The method comprises the steps S1 to S4 for controlling renewable energy park comprising at least two renewable energy resources.

Step S1 comprises measuring a power output of renewable energy park 17 at point of measurement 30. The measuring unit 24 of the renewable energy park controller 21 measures the power output as well as electrical parameters like voltage and/or current of the renewable energy park 17.

Step S2 comprises obtaining at least one required utility grid parameter at point of interconnection 23. The at least one line parameter is resistance, impedance, susceptance or length or a combination thereof. By obtaining via the obtaining unit 25 at least one line parameter of a high voltage (HV) or middle voltage (MV), like resistance, impedance, susceptance or a combination thereof the cal-culation of line losses can be executed. The calculation of line losses based on measurement and at least one line parameter of a high voltage (HV) or middle voltage (MV) line connecting to the pooling substation 19. Electrical power is active power and/or reactive power. Based on measured electrical parameters like voltage or current or a combination thereof of the renewable energy park 17 and at least one obtained line parameter of a high voltage (HV) or middle voltage (MV) line connecting to the pooling substation 19. Furthermore the length be-tween the point of measurement 30 and the point of interconnection 23 will be considered to calculate line losses. With these line losses together with the meas-ured power output of the renewable energy park 17 the provided power at the point of interconnection 23 can be calculated.

Step S3 comprises determining an electrical power offset based on line losses between point of measurement 30 and point of interconnection 23 for compensat-ing the line losses and for matching with required utility grid parameter. The cal-culated power output of Step S2 at the point of interconnection 23 can be com-pared with the required power output at the point of interconnection 23 for the utility grid. The difference between calculated and required power output deter-mines the electrical power offset via the determination unit 26.

Step S4 comprises adding electrical power offset to a control set point of at least one wind turbine 1 at a renewable energy park controller 21 for controlling the at least one renewable energy resource. At the summation unit 27 the electrical power offset will be added to the electrical power setpoint of at least one wind turbine 1. The electrical power offset depends on the difference between provid-ed and required power output at the point of inter-connection 23. The bigger the difference is the bigger is the electrical power offset and the number of wind tur-bines 1 with higher power output.

Another aspect of the present invention is directed to a method of operating a renewable energy park 17, wherein the renewable energy park controller 21 is configured to perform the method for controlling renewable energy park 17 as described above. The method of operating a renewable energy park 17 comprises the step of operating at least one of the wind turbines 1 with electrical power off-set to compensate line losses. The electrical power offset for the at least one wind turbine 1 is a reactive power offset. Same applies for the hybrid energy park 17a having a hybrid park controller 21a which is configured to perform the method for controlling hybrid energy park 17a as described above.

The above mentioned method can be executed by a computer program product comprising instructions which, when the program is executed by a computer, cause the computer to carry out the steps of the method for controlling renewable energy park described above.

LIST OF REFERENCE SIGNS

1 wind turbine
2 tower
3 nacelle
4 drive train chain
5 rotor shaft
6 rotor
7 gear box
8 high-speed-shaft
9 generator
10 electrical components
11 yaw system
12 rotor blades
13 pitch system
14 nacelle cover
15 spinner
16 hub
17 renewable energy park
17a hybrid energy park
18 transformer
19 pooling substation
19a hybrid pooling substation
20 connection point
20a hybrid connection point
21 renewable energy park con-troller
21a hybrid park controller
22 transformer
23 point of interconnection
24 measuring unit
, Claims:We Claim:

1. A method for controlling renewable energy park comprising of at least two renewable energy resources, the method comprises the steps of:
- measuring a power output of a renewable energy park at point of measurement (30),
- obtaining at least one required utility grid parameter at point of inter-connection (23),
- determining an electrical power offset based on line losses between point of measurement (30) and point of interconnection (23) for com-pensating the line losses and for matching with required utility grid parameter, and
- adding an electrical power offset to a control set point of the at least one renewable energy resource (1, 28, 29) at a renewable energy park controller (21, 21a) for controlling the at least one renewable energy resource (1, 28, 29).

2. The method of controlling renewable energy park according to claim 1, wherein calculating line losses based on measurement and at least one line parameter of a high voltage (HV) or middle voltage (MV) line connecting to the pooling substation (19, 19a).

3. The method of controlling renewable energy park according to claim 2, wherein the at least one line parameter is resistance, impedance, suscep-tance or length or a combination thereof.

4. The method of controlling a renewable energy park according to one of the preceding claims 1 to 3, wherein electrical power is active power and/or re-active power.

5. The method of controlling a renewable energy park according to one of the preceding claims 1 to 4, wherein calculating the at least one grid parameter at point of interconnection (23).

6. The method of controlling a renewable energy park according to one of the preceding claims 1 to 5, wherein the at least one grid parameter comprises grid voltage at point of interconnection (POI), power factor at point of in-terconnection (POI) and/or reactive power at point of interconnection (POI).

7. A renewable energy park controller for performing a method for controlling renewable energy park according to claim 1, comprising of
- a measuring unit (24) for measuring a power output of renewable en-ergy park at point of measurement (30),
- an obtaining unit (25) for obtaining at least one required utility grid parameter at point of interconnection (23),
- a determination unit (26) for determining electrical power offset based on line losses between point of measurement (30) and point of interconnection (23) for compensating the line losses and for match-ing with required utility grid parameter, and
- a summation unit (27) for adding electrical power offset to a control set point of the at least one renewable energy resource (1, 28, 29).

8. The renewable energy park controller according to claim 7, wherein the controller is a renewable energy park controller (21, 21a) connected to each of the renewable energy resources (1, 28, 29).

9. A method for operating a renewable energy park comprising a renewable energy park controller (21, 21a) according to one of the claims 7 and 8 for performing the method for controlling renewable energy park according to one of the claims 1 to 6.

10. The method for operating a renewable energy park according to claim 9, wherein the method comprises the step of operating at least one of the re-newable energy resources (1, 28, 29) with power offset to compensate line losses.

11. The method for operating a renewable energy park according to claim 10, wherein operating at least one of the renewable energy resources (1, 28, 29) with reactive power offset.

12. A renewable energy park comprising a renewable energy park controller (21, 21a) according to claim 7 and at least two renewable energy resources (1, 28, 29).

13. The renewable energy park according to claim 12, comprises at least one wind turbine park having at least one wind turbine (1), photovoltaic park having at least one photovoltaic device (28), biomass park having at least one biomass device (29) or hydro park having at least one hydro device or a combination thereof as renewable energy resource (1, 28, 29).

14. A computer program product comprising instructions which, when the pro-gram is executed by a computer, cause the computer to carry out the steps of the method for controlling renewable energy park (17, 17a) according to one of the claims 1 to 6.

Dated this 18th day of September, 2023