Pitch system and method for test of a power bank and use of the pitch system for performing the method

Abstract

Pitch system (1) comprising at least one pitch motor drive (3) connected an electrical network (5). Each pitch motor drive (3) is connected to a power bank, and the pitch system comprises a test module adapted to be activated in a test position. The test module comprises a brake module (8) each connected to a pitch motor drive (3), and each brake module (8) is adapted to load a pitch motor drive (3) with a certain load Rb. Hereby a voltage drop takes place over the power bank (6). The power bank (6) is separated into a number of power blocks (9) and the voltage drop V of each power block (9) is adapted to be registered by the test module when the brake module (8) is activated.

Claims

1. A pitch system for identifying a defective power block in a DC-power block having a plurality of power blocks utilized in a wind turbine or a marine energy installation having at least one pitch motor drive, each pitch motor drive is adapted to communicate with units comprising a motor which is connected to the pitch motor drive for positioning of a rotor blade, each pitch motor drive is connected to an electrical supply network, and each pitch motor drive is coupled to the DC-power bank, the pitch system comprising: a test module configured to be activated in a test position of the pitch system that disconnects the electrical supply network from the pitch motor drive, the test module comprises: a brake module connected to the at least one pitch motor drive, and the brake module is configured to load a pitch motor drive with a load/resistance RB by which a voltage drop V is provided in each of the power blocks, the test module is configured to register the voltage drop V for each of the power blocks starting at activation of the brake module and loading of the pitch motor drive with the load/resistance Rb until just prior to removal of the load/resistance Rb; the test module is configured to convert a registered voltage drop V to a resistance value Ri.sub.x for each power block having the number x, the test module is configured to convert a registered voltage drop V to a capacitance value Ci.sub.x for each power block having the number x, the test module is configured to compare the resistance value Ri.sub.x and the capacitance value Ci.sub.x for each power block having the number x with corresponding values for each of the power blocks, the test module is configured to report an error for the defective power block having the number x for Ci.sub.x and Ri.sub.x values of the block that deviate from predefined intervals (Ci; Ci) and (Ri; Ri), wherein end-values of the intervals comprise a capacitance value Ci and a resistance value Ri for the entire DC-power bank, and the test module is configured to report an error for the defective power block having Ri.sub.x and the Ci.sub.x values that are different from a predefined deviate value Ai between each of the power blocks.

2. The pitch system according to claim 1, wherein the power bank comprises replaceable batteries and that the power bank is divided into a number of power blocks each comprising a number of serial connected batteries.

3. The pitch system according to claim 1, wherein the resistance value Ri.sub.x for each power block is converted to a corresponding resistance value at a predefined temperature.

4. The pitch system according to claim 1, wherein the pitch system comprises at least two pitch motor drives each adapted to surveille and control the motor for pitching the rotor blade.

5. The pitch system according to claim 1, wherein that Rb is a predefined resistance-value.

6. The pitch system according to claim 1, the voltage drop V of each power block is adapted to be registered by the test module, in the interval from the brake module is activated and is loading the pitch motor drive with the load/resistance Rb and just prior to the load Rb is removed, which is until 1/100 sec.- 5/100 sec before the load Rb is removed.

7. A method for identifying and replacing a defective power block in a DC-power block having a plurality of power blocks connected to a pitch system for a wind turbine or a marine energy installation, said pitch system comprises at least one pitch motor drive adapted to communicate with connected units including a motor, connected to the pitch motor drive for positioning a rotor blade, said pitch motor drive(s) is/are connected to a supply network and each pitch motor drive is connected to the power bank, the method comprising: providing a test module comprising a brake module connected to the at least one pitch motor drive; activating by the test module a test position that disconnects the supply network to the pitch motor drive(s); loading by the test module a load/resistance Rb to each pitch motor drive; registering by the test module a voltage drop V for each of the power blocks from activation of the brake module and loading of the pitch motor drive with the load/resistance Rb until just prior to removal of the load/resistance Rb; converting by the test module the registered voltage drop V to a resistance value Ri.sub.x for each power block having the number x; converting by the test module the registered voltage drop V to a capacitance value Ci.sub.x for each power block having the number x; comparing by the test module the resistance value Ri.sub.x and the capacitance value Ci.sub.x for each power block having the number x with corresponding values for each of the power blocks; reporting by the test module an error for the defective power block having the number x for Ci.sub.x and Ri.sub.x values of the block that deviate from predefined intervals (Ci; Cr) and (Ri; Ri), wherein end-values of the intervals comprise a capacitance value Ci and a resistance value Ri for the entire DC-power bank; reporting by the test module an error for the defective power block having Ri.sub.x and the Ci.sub.x values that are different from a predefined deviate value Ai between each of the power blocks; and replacing the defective power block with a non-defective power block.

8. The method according to claim 7, wherein the power bank comprises replaceable batteries and that the power bank is divided into a number of power blocks each comprising serial connected batteries and that each power block supplies a voltage which is approximately the same as the other power blocks when the blocks are in faultless condition, and the test module measures the voltage drop V across each energy block.

9. The method according to claim 7, wherein the test module is activated after a specific time interval whereby a message concerning the power state of each battery block is activated.

10. The method according to claim 7, wherein the brake module is loading the motor at a normal operation of the pitch system.

11. The method according to claim 7, wherein the interval values Ri,Ri and Ci,Ci are determined by empiric data or by measuring the voltage drop Vi of the entire power bank, and calculating average acceptable values for each power block.

12. The method according to claim 7, wherein the power bank is exposed for a time-short load before the test module is activated whereby a truthful start position for the module is provided.

13. The method according to claim 7, wherein the value of the load/resistance Rb is defined before the load/resistance Rb is activated and is loading the pitch motor drive.

14. The method according to claim 7, wherein the voltage drop V of each power block is registered by the test module, in the interval running from the brake module is activated and is loading the pitch motor drive with the load/resistance Rb and just prior to the load Rb is removed, which is until 1/100 sec.- 5/100 sec before the load Rb is removed.

15. Use of the pitch system according to claim 1 for performing the method according to claim 7.

Description

(1) The invention will be explained with reference to the drawing.

(2) FIG. 1 shows a pitch system according to the invention and external units connected to the pitch system

(3) FIG. 2 shows a sub element of FIG. 1 comprising, inter alia, a pits motor drive and a brake.

(4) FIG. 3 shows a brake module for loading the pitch motor drive.

(5) FIGS. 4A and B show a diagram for the voltage drop when the brake module is activated.

(6) FIG. 1 shows a pitch system 1 according to the invention. The pitch system 1 is connected to a number of units. 4,4, 4. The pitch system 1 is shown in connection with a system for driving a wind turbine comprising three rotor blades but could also be used for a system for driving a wind turbine comprising 2 rotor blades or a system used for off shore installations. The pitch system 1 comprises three pitch motor drives 3 as a consequence of being shown for a wind turbine comprising three rotor blades. Each pitch motor drive 3 is connected to a motor 4,2 and a replaceable power bank 6. Typically, the power bank 6 comprises reloadable batteries such as lead batteries, lithium batteries or ultra-caps. Each power bank 6 connected to a pitch motor drive 3 is separated into blocks 9 as explained below.

(7) The pitch system 1 communicates with a slip ring 4a unit that transfers electrical signals and power from a fixed part to a rotating part, and a nacelle 4 comprising a main controller 11 and a supply network 5.

(8) Each electrical motor 2an actuatormoves a rotor blade (not shown at the figure). A typically wind turbine has as mentioned three rotor blades which causes the number of individual driven motors 2 to be three. The electrical pitch system 1 has an interface to the electrical system of the nacelle 4 and receives an electrical current from the grid 5 in order to drive the motors 2/the rotor blades.

(9) The pitch system 1 has two primary functions, one is the normal operation where the pitch system 1 is used to optimize the regulation of the rotor blades in all wind/flow situations and the other is to brake the rotor blades. This brake function takes place by moving the rotor blade away from the operation areawhich is from 0 to 30 depending on the actual average wind speedto a vane position, this is 90. In this situation, the leading edge is facing the wind/wave direction. The three motors must be controlled individually and independent of each other.

(10) FIG. 2 shows a sub element of FIG. 1 comprising, inter alia, a pitch motor drive 3 and a brake 8. The pitch motor drive 3 is connected a power bank 6 which in this example is divided into four energy blocks 9, namely, block 1, block 2, block 3, block 4. The power bank 6 is a replaceable power bank, and when it is divided into a number of blocks 9whose resistance Ri.sub.x and capacitance Ci.sub.x can be calculated from the voltage drop V when the brake is appliedit is possible to identify, whether there is one of the blocks 9 that are defective and therefore needs to be replaced. Alternatively, it is possible to detect if one of the blocks 9 shortly will be defective and should be replaced before damage is done.

(11) FIG. 3 shows a brake module 8 for loading a pitch motor drive 3. The load 13 is provided by applying a resistance Rb, after the test module has been activated and after the EL supply network has been interrupted. This results in a voltage drop V of each block 1,2,3,4.

(12) The voltage drop V is registered over the interval from the moment the load Rb sets in on time T1 until time T2 that is about 1/100 seconds before time T3, which is the time when the load Rb is removed. The voltage drop Vi for all the blocks is registered and the voltage drop V for each single block is registered.

(13) The voltage drop V of each block 9 causes the capacitance value Ci.sub.x for each block 9 and the resistance value Ri.sub.x for each block 9 may be calculated from an algorithm:

(14) Calculation of Ri.sub.xwhich is the resistance of each block with the number xis calculated from the following:
Ri.sub.x=[(UT1.sub.,xUT2.sub.,x)*Rb]/UT2

(15) Calculation of C.sub.ix, which is the capacitance of each block with the number xis calculated from the following:
Ci.sub.x=(UT2.sub.,xUT2.sub.,x-i)*UT2/[(Rb*(T3T1)]

(16) The symbols are as follows: Ci The capacitance for the entire power bank [F] Ci.sub.,average The capacitance. Average value for each block [F] Ci.sub.x The capacitance for the block with the number x [F], X=1 . . . 4 Ri The resistance for the entire power bank [] Ri.sub.,average The resistance. The average value for each block [] Ri.sub.x The resistance for the block with the number x Rb Resistance, brake/load resistance []. T1 The time where Rb is activated [s] T2 Time for registered minimum voltage. [s] T3 Time where Rb is removed. [s] UT1 Voltage measured at time T1 for the entire power bank [V] UT1.sub.,x Voltage at the time T1 for block x [V], x=1 . . . 4 UT2 Voltage at the time T2 for the entire power bank [V] UT2.sub.,x Voltage at the time T2 for block x x [V], x=1 . . . 4 UT3 Voltage at the time T3 for the entire power bank [V]

(17) The voltage drop Vi for all the blocks 9 causes that the capacitance value Ci for all the blocks and the resistance value Ri for all the blocks (that is the entire power bank 6) may be calculated using an algorithm:

(18) Ci is then calculated:
Ci=UT2*UT2/[Rb*(T3T1)]

(19) Moreover, Ri is then calculated:
Ri=(UT1UT2)*Rb/UT2

(20) A mean value for each power block is then calculated:
Ri.sub.,average: Ri/number of blocks
Ci.sub.,average: Ci*number of blocks

(21) Limiting values for what leads to an error message will be a certain percentage P for example, 10% of the average values for the resistance and capacitance.

(22) When a value for P of 10% is used the error occur at

(23) Error signal:
Ri=Ri.sub.,average*(1+0,1)Ri.sub.xRi.sub.,average*(10,1)=Ri
Ci=Ci.sub.,average*(1+0,1)Ci.sub.xCi.sub.,average*(10,1)=Cr

(24) If one of the above two equations is not valid, there is an error to be reported.

(25) In addition, the algorithm includes that the resistance value Ri.sub.x and the capacitance value Ci.sub.x for each power block 9 is compared with corresponding values for the other power blocks 9. The test module reports an error when the Ri.sub.x and Ci.sub.x value of a power block 9 is different from a predefined deviation value Ai between the power blocks 9.

(26) FIGS. 4A and B thus shows the principle of the measurement taking place for each block and the entire block as for x=0 it is the entire block that is measures and for x=1,2,3,4 it is each single block as in this example 4 blocks are used. However, the number of blocks could off course be different: it could be more or less.

(27) FIG. 4A shows the voltage drop for the entire block between T1 and T2 and measured between UT1.sub.,x and UT2.sub.,x. FIG. 4B shows the voltage drop for each block 1,2,3,4 and using the nomenclature as mentioned above.

(28) All the blocks 9 are tested using a specific loadthe break resistance Rb. The load is set so that a test sequence simulates current and a time when the motor will need to position the blade to its zero position. A brake chopper starts/stops the brake.

(29) The values for Ri, Ci, Ri.sub.x and Ci.sub.x are all saved during time in such a way that the values may be evaluated.

(30) The resistance value Ri for each power block 9 is converted by an algorithm converted to an equivalent resistance value at a predefined temperature.

(31) The resistance is normalized to a temperature at 20 C. which means that the specific temperature coefficient is 0,00393 1/ C. at 20 C.

(32) This gives:
R.sub.normalized=Ri.Math.(1+0,0039.Math.(20-temperature)).

(33) By the invention a reliable test module is provide. The invention is saving costs as the batterieswhich are still functionalcontinue to operate until they reach a level where the test module reveals they must be replaced. The invention makes the maintenance of batteries more robust and decreases the risk of malfunction and hazardous situations. A decay of important performance parameters is also monitored over time.