METHOD FOR DETERMINING PERFORMANCE PARAMETERS IN REAL TIME

Abstract

Embodiments herein determine performance parameters for a balance of plant estimator of a power plant controller configured to control a renewable power plant comprising a plurality of power generating units, wherein the balance of plant estimator is configured to provide an internal power loss estimation of the renewable power plant. The embodiments include providing at least one first pair of associated first and second power values in a first power range, providing at least one second pair of associated first and second power values in a second power range, determining a representative of the first pair, and determining a representative of the second pair in accordance with predetermined rules, and calculating a first set of performance parameters using the representatives of the first and second pairs of associated first and second power values.

Claims

1. A method for determining performance parameters for a balance of plant estimator of a power plant controller configured to control a renewable power plant comprising a plurality of power generating units, wherein the balance of plant estimator is configured to provide an internal power loss estimation of the renewable power plant, the method comprising: providing at least one first pair of associated first and second power values in a first power range; providing at least one second pair of associated first and second power values in a second power range; determining a representative of the first pair of associated first and second power values, and determining a representative of the second pair of associated first and second power values in accordance with predetermined rules; and calculating a first set of performance parameters using the representatives of the first and second pairs of associated first and second power values.

2. The method of claim 1, further comprising: providing at least one third pair of associated first and second power values in a third power range; providing at least one fourth pair of associated first and second power values in a fourth power range; determining a representative of the third pair of associated first and second power values, and determining a representative of the fourth pair of associated first and second power values in accordance with predetermined rules; calculating a second set of performance parameters using the representatives of the third and fourth pairs of associated first and second power values; and comparing the first and second sets of performance parameters and applying one of them in the balance of plant estimator of the power plant controller when they deviate less than a predetermined amount.

3. The method of claim 2, wherein each first power value of the first, second, third and fourth pairs of power values equals a total amount of produced active power from the plurality of power generating units, and wherein each second power value of the first, second, third and fourth pairs of power values equals a measured active power at a point of measurement.

4. The method of claim 2, wherein the plurality of calculated performance parameters to be applied in the balance of plant estimator comprise three performance parameters.

5. The method of claim 2, wherein a plurality of first, second, third and fourth pairs of associated first and second power values are provided.

6. The method of claim 5, wherein applying the predetermined rules comprises selecting the first, second, third and fourth pairs of associated first and second power values when said first, second, third and fourth pairs of associated first and second power values deviate less than a predetermined amount from respective preceding first, second, third and fourth pairs of associated first and second power values.

7. The method of claim 5, wherein applying the predetermined rules comprises calculating respective average values of the plurality of first, second, third and fourth pairs of associated first and second power values.

8. The method of claim 2 wherein the first and third power ranges are between 0 and 0.5 pu, and wherein the second and fourth power ranges are between 0.5 pu and 1 pu.

9. The method of claim 1, further comprising providing at least one pair of associated first and second power values in each of a number of additional power ranges, and determining a representative of the pairs of associated first and second power values in each of the additional power ranges in accordance with predetermined rules.

10. The method of claim 1, wherein providing the first and second pairs of associated first and second power values is performed at predetermined events, including during time periods of essentially stable power conditions.

11. The method of claim 1, wherein the first and second pairs of associated first and second power values are deleted when associated performance parameters have been calculated.

12. A computer program product for performing the method according to claim 1 when said computer program product is run on a computer processing unit of a power plant controller.

13. A power plant controller configured to control a renewable power plant comprising a plurality of power generating units, the power plant controller comprising a balance of plant estimator configured to provide an internal power loss estimation of the renewable power plant, the power plant controller comprising: a sensor arrangement adapted to provide: at least one first pair of associated first and second power values in a first power range; at least one second pair of associated first and second power values in a second power range; a processor adapted to: determine a representative of the first pair of associated first and second power values, and determining a representative of the second pair of associated first and second power values in accordance with predetermined rules; and calculate a first set of performance parameters for the balance of plant estimator using the representatives of the first and second pairs of associated first and second power values.

14. A power plant controller according to claim 13, wherein the sensor arrangement is furthermore adapted to provide: at least one third pair of associated first and second power values in a third power range; and at least one fourth pair of associated first and second power values in a fourth power range; and wherein the processor is furthermore adapted to: determine a representative of the third pair of associated first and second power values and determining a representative of the fourth pair of associated first and second power values in accordance with predetermined rules; calculate a second set of performance parameters for the balance of plant estimator using the representatives of the third and fourth pairs of associated first and second power values; and compare the first and second sets of performance parameters and applying one of them in the balance of plant estimator of the power plant controller when they deviate less than a predetermined amount.

15. A power plant controller according to claim 14, wherein each first power value of the first, second, third and fourth pairs of power values equals a total amount of produced active power from the plurality of power generating units, and wherein each second power value of the first, second, third and fourth pairs of power values equals a measured active power at a point of measurement.

16. A power plant controller according to claim 14, wherein the plurality of calculated performance parameters to be applied in the balance of plant estimator comprise three performance parameters.

17. A power plant controller according to claim 13 wherein the first and third power ranges are between 0 and 0.5 pu, and wherein the second and fourth power ranges are between 0.5 pu and 1 pu.

18. A power plant controller according to claim 13, wherein the first and second pairs of associated first and second power values are deleted when associated performance parameters have been calculated.

19. A wind power plant comprising a power plant controller according to claim 13.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0054] The present invention will now be explained in further details with reference to the accompanying figures, wherein

[0055] FIG. 1 shows variations in available produced active power, P.sub.prod,

[0056] FIG. 2 shows an estimated power loss curve, and

[0057] FIG. 3 shows a flow-chart illustrating the method according to the present invention.

[0058] While the invention is susceptible to various modifications and alternative forms specific embodiments have been shown by way of examples in the drawings and will be described in details herein. It should be understood, however, that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE INVENTION

[0059] In a general aspect the present invention relates to a method for determining BoP estimator performance parameters from real time measurements and update said performance parameters in accordance with predetermined rules, such as automatically. The updated performance parameters may be uploaded and applied in a power loss estimation algorithm, such as a second order power loss estimation algorithm, of the BoP estimator in accordance with a predetermined set of rules as it will be disclosed in further details below.

[0060] The method according to the present invention will in the following be explained with reference to a number of steps—more particularly with reference to seven steps. In terms of implementation the following steps will form part of an active power control scheme for power plants. The steps may not necessarily be carried out in the order outlined below.

[0061] In step 1 the active power loop of the power plant controller is initialized with a set of default or predetermined BoP estimator performance parameters. This approach could however lead to limited performance of the control loop. Depending on the type of the active power control scheme non-optimized BoP parameters typically lead to limited performance of the control loop.

[0062] In step 2, an allowed variation (peak-to-peak) of the available produced active power, P.sub.prod, over a specified time period should be decided. The peak-to-peak variation of the available produced active power may depend on the rated active power level of the power plant, and the specified time period may also depend on various parameters.

[0063] FIG. 1 depicts how the available produced active power, P.sub.prod, typically vary over time. FIG. 1 further shows examples of three specified time periods t.sub.1, t.sub.2 and t.sub.3 as well as three associated peak-to-peak values of P.sub.prod being denoted ΔP.sub.1, ΔP.sub.2 and ΔP.sub.3.

[0064] The allowed variation of the available produced active power, P.sub.prod, may for example be decided on the basis of known power loss data for various power plant sizes. Generally, the variation of P.sub.prod will depend on how much the power loss changes as a function of produced active power according to known power curves.

[0065] When the variation of P.sub.prod is measured to be within an allowed limit over the the following quantities are measured and stored: [0066] 1) the sum of the produced active power from the WTGs, i.e. P.sub.prod [0067] 2) the power measured, P.sub.meas, at a point of measurement (PoM)

[0068] FIG. 2 shows a typical power loss curve where the internal power loss, P.sub.loss, of the power plant is depicted as a function of the produced power, P.sub.prod, of the power plant. The estimated internal power loss curve shown in FIG. 2 follows a second order dependency of the type

P.sub.loss=aP.sub.prod.sup.2+bP.sub.prod+c

where the three coefficients a, b and c correspond to the performance parameters to be determined by the method of the present invention.

[0069] As depicted in FIG. 2 the power loss changes less (P.sub.loss2) in the low-power region between P.sub.prod=0 pu and P.sub.prod=0.5 pu compared to the power loss changes (P.sub.loss1) in the high-power region between P.sub.prod=0.5 pu and P.sub.prod=1 pu.

[0070] In step 3 the number of measurement points and/or power regions necessary to extract the BoP performance parameters is decided. As an example one or more measurement points within the following power regions may be selected 0.1-0.3 pu, 0.3-0.5 pu, 0.5-0.6 pu, 0.6-0.7 pu, 0.7-0.75 pu, 0.75-0.8 pu, 0.8-0.85 pu, 0.85-0.9 pu, 0.9-0.92 pu, 0.92-0.94 pu, 0.94-0.96 pu, 0.96-0.98 pu and 0.98-1 pu.

[0071] The selected power region may also be based on available power loss data from various power plant sizes.

[0072] In order to minimize the risk of making inaccurate measurements, the measurements of P.sub.prod and P.sub.meas is repeated until the measurements falls within predefined tolerances, i.e. that at least two consecutive measurements of P.sub.prod and P.sub.meas fall within the predefined tolerances

[0073] When the power data, P.sub.prod and P.sub.meas, for all selected power regions are available, i.e. stored, a calculation that extracts the BoP performance parameters from the loss information is performed as step 4 of the method according to the present invention. The calculation that extracts the BoP performance parameters may be based on common mathematical models, such as a mathematical model involving polynomial curve fitting.

[0074] In order to make sure that the performance parameters are extracted correctly different power regions and/or different variations of P.sub.prod may be defined in a step 5. Based on the different power regions and/or different variations of P.sub.prod steps 3 and 4 may be repeated. The set of performance parameters are then compared, and if the sets are within defined tolerances, one of the sets is selected and subsequently prepared for being uploaded to the BoP estimator of the power plant controller.

[0075] In step 6 it is decided when to calculate the performance parameters for the BoP estimator. This decision may for example be based on monitoring the estimated internal power losses based on power set-points, and comparing the estimated internal power losses to measured power losses in some sort of “steady state” conditions. The “steady state” condition may be defined in various ways, including looking at the variation of the available produced active power, P.sub.prod, as discussed in relation to method step 2. If the difference between the estimated and measured internal power losses is larger than a specified limit then the calculation of the performance parameters for the BoP estimator is initiated.

[0076] Deciding, in a step 7, when to upload the updated performance parameters to the BoP estimator may be based on a variety of inputs including user instructions or other events, such as active power loop initialization, predetermined time intervals (such as once a year/month/week), as soon as the performance parameters fulfil certain requirements, then an alarm is raised etc. It should be noted that method step 6 may also trigger an alarm.

[0077] The method for determining the performance parameters for the BoP estimator is illustrated in FIG. 3 where the active power loop is initiated as the first step 301. In a second step 302, the allowed variation (peak-to-peak) of the available produced active power, P.sub.prod, over a specified time period is decided. Moreover, the number of measurement points and/or power regions necessary to extract the BoP performance parameters is also decided in step 302. The available produced active power, P.sub.prod, is then measured via a plurality of measurements during the specified time period in step 303.

[0078] In step 304 it is determined whether variations of P.sub.prod are within the allowed limit. If the answer is “No”, i.e. P.sub.prod varies more than allowed, further measurements P.sub.prod are performed. If the answer is “Yes” associated values of P.sub.prod and P.sub.meas are stored.

[0079] In step 305 it is decided whether the measurements of P.sub.prod are stable and thus fall within predefined tolerances, i.e. that at least two consecutive measurements of variations of P.sub.prod fall within the predefined tolerances. If the answer is “No” further measurements P.sub.prod are performed. If the answer is “Yes” a first set of BoP estimator performance parameters are calculated in step 306.

[0080] As discussed above the method steps 302 to 306 may be repeated in order to make sure that the BoP estimator performance parameters are extracted correctly. The method steps 302 to 306 leads to a second set of performance parameters which are compared to the first set of performance parameters. If the first and second sets of performance parameters are within predefined tolerances, one of the sets is selected and subsequently prepared for being uploaded to the BoP estimator of the power plant controller.