METHOD FOR CONTROLLING AN ACTIVE RECTIFIER OF A WIND POWER INSTALLATION

Abstract

A method for controlling a converter, preferably a generator-side active rectifier of a power converter of a wind power installation, comprising: specifying a target value for the converter; specifying a carrier signal for the converter; capturing an actual value; determining a distortion variable from the target value and the actual value; and determining driver signals for the converter on the basis of the distortion variable and the carrier signal.

Claims

1. A method for controlling a generator-side active rectifier of a power converter of a wind power installation, the method comprising: specifying a target value for the converter; specifying a carrier signal for the converter; receiving an actual value indicative of a current of an electrical system of the generator; determining a distortion variable from the target value and the actual value; and determining driver signals for the converter based on the distortion variable and the carrier signal.

2. The method according to claim 1, wherein determining the distortion variable takes into account a closed-loop control difference and/or a database.

3. The method according to claim 1, wherein determining the driver signals includes comparing the distortion variable and/or a modulation signal, which is based on the distortion variable, with the carrier signal.

4. The method according to claim 1, wherein determining the driver signals are based on an offset.

5. The method for controlling a converter according to claim 4, wherein the offset is a precalculated offset, which takes an operating point into account.

6. The method according to claim 1, wherein the target value is a target current value for a current of an electrical system of a generator of a wind power installation.

7. The method according to claim 1, wherein the carrier signal is for setting a single-phase current of an electrical system of the generator of the wind power installation.

8. The method according to claim 1, wherein the carrier signal is generated by a signal generator and has at least one of the following forms: triangular; sinusoidal; and square-wave.

9. The method according to claim 1, wherein the actual value is an actual current value of the electrical system of the generator of the wind power installation.

10. The method according to claim 1, wherein: the target value, the distortion variable, a compensation value are in d/q coordinates, and/or the actual value is present in abc coordinates.

11. A method for controlling a wind power installation, comprising: operating a converter of the wind power installation in a first operating mode; and operating the converter of the wind power installations in a second operating mode, wherein the converter is operated in the second operating mode using the method according to claim 1.

12. The method according to claim 11, wherein the converter is operated in the first operating mode using a tolerance band method.

13. The method according to claim 11, wherein the converter is operated in the first operating mode using constant band limits.

14. The method according to claim 11, wherein the converter is operated in the second operating mode using modulated band limits.

15. The method according to claim 11, wherein the converter is operated in the second operating mode first using a first carrier signal or a first modulated band limit for a predetermined time, and then the converter is operated using a second carrier signal or a second modulated band limit.

16. The method according to claim 11, comprising: changing from the first operating mode to the second operating mode if: a) at least one of the wind power installation or the generator has an acoustic variable above a predetermined limit value, or b) the wind power installation controller specifies instructions to do so.

17. A wind power installation comprising: a converter; and a controller, wherein the converter is a power converter and is configured to be operated by the controller using the method according to claim 1.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0126] The present invention is explained in more detail below on the basis of the accompanying figures, wherein the same reference signs are used for identical or similar components or assemblies.

[0127] FIG. 1 schematically shows, by way of example, a perspective view of a wind power installation in one embodiment.

[0128] FIG. 2 schematically shows, by way of example, a structure of an electrical phase section of a wind power installation in one embodiment.

[0129] FIG. 3 schematically shows, by way of example, the structure of a converter.

[0130] FIG. 4A schematically shows, by way of example, the structure of a control unit (e.g., controller of a converter in one embodiment. FIG. 4B schematically shows, by way of example, the structure of a control unit (e.g., controller of a converter in a further preferred embodiment.

[0131] FIG. 4C schematically shows, by way of example, a control module (e.g., control circuit) of a control unit for varying a frequency of the signal.

[0132] FIG. 5 schematically shows, by way of example, the sequence of a method for controlling a converter in one embodiment.

[0133] FIG. 6 schematically shows, by way of example, determination of a driver signal for the converter on the basis of the distortion variable and the carrier signal.

DETAILED DESCRIPTION

[0134] FIG. 1 schematically shows, by way of example, a perspective view of a wind power installation 100.

[0135] The wind power installation 100 is in the form of a buoyancy rotor with a horizontal axis and three rotor blades 200 on the windward side, in particular as horizontal rotors.

[0136] The wind power installation 100 has a tower 102 and a nacelle 104.

[0137] An aerodynamic rotor 106 with a hub 110 is arranged on the nacelle 104.

[0138] Preferably exactly three rotor blades 108 are arranged on the hub 110, in particular in a symmetrical manner with respect to the hub 110, preferably in a manner offset by 120°.

[0139] FIG. 2 schematically shows, by way of example, an electrical phase section 100′ of a wind power installation 100, as preferably shown in FIG. 1.

[0140] The wind power installation 100 has an aerodynamic rotor 106 which is mechanically connected to a generator 120 of the wind power installation 100.

[0141] The generator 120 is preferably in the form of a 6-phase synchronous generator, in particular with two three-phase systems 122, 124 which are phase-shifted through 30° and are decoupled from one another.

[0142] The generator 120 is connected to an electrical supply network 2000 or is connected to the electrical supply network 2000 via a converter 130 and by means of a transformer 150.

[0143] In order to convert the electrical power generated by the generator 120 into a current iG to be fed in, the converter 130 has in each case at least one converter module 130′, 130″ for each of the electrical systems 122, 124, wherein the converter modules 130′, 130″ are substantially structurally identical.

[0144] The converter modules 130′, 130″ have an active rectifier 132′ at a converter module input. The active rectifier 132′ is electrically connected to an inverter 137′, for example, via a DC voltage line 135′ or a DC voltage intermediate circuit.

[0145] The converter 130 or the converter modules 130′, 130″ is/are preferably in the form of (a) direct converter(s) (back-to-back converter).

[0146] The method of operation of the active rectifiers 132′, 132″ of the converter 130 and the control thereof are explained in more detail in FIG. 3, in particular.

[0147] The two electrically three-phase systems 122, 124 which are decoupled from one another on the stator side are combined, for example, on the network side, at a node 140 to form a three-phase overall system 142 which carries the total current iG to be fed in.

[0148] In order to feed the total current iG to be fed in into the electrical supply network 2000, a wind power installation transformer 150 is also provided at the output of the wind power installation, which transformer is preferably star-delta connected and connects the wind power installation 100 to the electrical supply network 2000.

[0149] The electrical supply network 2000, to which the wind power installation 100, 100′ is connected by means of the transformer 150, may be, for example, a wind farm network or an electrical supply or distribution network.

[0150] In order to control the wind power installation 100 or the electrical phase section 100′, a wind power installation control unit (e.g., controller) 160 is also provided.

[0151] In this case, the wind power installation control unit 160 is configured, in particular, to set a total current iG to be fed in, in particular by controlling the active rectifiers 132′, 132″ or inverters 137′, 137″.

[0152] In this case, the active rectifiers 132′, 132″ are controlled, in particular, as described herein, preferably by means of or on the basis of the driver signals T.

[0153] The wind power installation control unit 160 is preferably also configured to capture the total current iG using a current capture means 162. The currents of each converter module 137′ in each phase are preferably captured for this purpose, in particular.

[0154] In addition, the control unit also has voltage capture means 164 which are configured to capture a network voltage, in particular of the electrical supply network 2000.

[0155] In one particularly preferred embodiment, the wind power installation control unit 160 is also configured to also capture the phase angle and the amplitude of the current iG to be fed in.

[0156] The wind power installation control unit 160 also comprises a control unit (e.g., controller) 1000, described herein, for the converter 130.

[0157] The control unit 1000 is therefore configured, in particular, to control the entire converter 130 with its two converter modules 130′, 130″, in particular as shown in FIG. 4, using driver signals T.

[0158] FIG. 3 schematically shows, by way of example, the structure of a converter 130, in particular of active rectifiers 132′, 132″, as shown in FIG. 2.

[0159] In this case, the converter 130 comprises, in particular, two active rectifiers 132′, 132″:

[0160] a first active rectifier 132′ for a or the first electrically three-phase system 122 and a second active rectifier 132″ for a or the second electrically three-phase system 124.

[0161] The active rectifiers 132′, 132″ are each connected, on the generator side, to a system 122, 124 of a or the generator 120 and are connected to an inverter 137′, 137″ via a DC voltage 135′, 135″, for example, as shown in FIG. 2, in particular.

[0162] The active rectifiers 132′, 132″ are each controlled using drive signals T by means of the control unit 1000 described herein and/or by means of a method described herein, in particular in order to respectively inject a three-phase alternating current ia′, ib′, ic′, ia″, ib″, ic″ in the stator of the generator 120.

[0163] FIG. 4A schematically shows, by way of example, the structure of a control unit 1000 of a converter 130, in particular for an active rectifier 132′, 132″.

[0164] The control unit 1000 determines a distortion variable E from a target value S* and an actual value S.

[0165] The target value S* and the actual value S are preferably physical variables of the converter, for example, an alternating current to be generated by the active rectifier 132′, 132″.

[0166] The distortion variable E is determined from the target value and the actual value, preferably by means of a difference. The distortion variable can therefore also be referred to as a closed-loop control error or measurement error. If the target value S* is a target current and the actual value S is an actual current, the distortion variable E can also be referred to as a distortion current. The difference is preferably determined from abc coordinates, in particular as shown in FIG. 4B.

[0167] The distortion variable E, in particular the distortion current, is compared with a signal R, for example, a ramp signal, in order to generate the driver signals T for the converter 130, in particular the active rectifier 132′, 132″.

[0168] For example, the distortion variable E can be functionally compared with the carrier signal R in such a manner that each point of intersection between the distortion variable E and the carrier signal R is used as a trigger point for a driver signal T, in particular as shown in FIG. 6.

[0169] For this purpose, the carrier signal R may be, for example, in the form of a triangular signal, in particular with or without hysteresis.

[0170] The control unit 1000 is therefore in the form of a (ramp) comparison controller, in particular.

[0171] FIG. 4B schematically shows, by way of example, the structure of a control unit of a converter in a further preferred embodiment, in particular for an active rectifier 132′, 132″.

[0172] The control unit 1000 is constructed substantially as in FIG. 4A, wherein the target value S*, the compensation value i_compd, i_compq and the parameters i.sub.d_LUT, i.sub.q_LUT are present in d/q coordinates and the actual value S is present in abc coordinates.

[0173] The target value S* is a target current value i.sub.d*, i.sub.q* in d/q coordinates. The compensation value i i.sub.d_comp, i.sub.q_comp is likewise a current value and is based on a closed-loop control difference i.sub.a_diff, i.sub.b_diff, i.sub.c_diff and/or on a parameter i.sub.d_LUT, i.sub.q_LUT in a database LUT.

[0174] The d component of the target current id* and the q component of the target current iq* are first of all transformed into abc coordinates. A closed-loop control difference i.sub.a_diff, i.sub.b_diff, i.sub.c_diff is then determined from the target currents i.sub.a**, i.sub.b**, i.sub.c**, transformed into abc coordinates, and the actual values i.sub.a, i.sub.b, i.sub.c, in particular for each coordinate a, b, c individually.

[0175] This closed-loop control difference i.sub.a_diff, i.sub.b_diff, i.sub.c_diff is transformed back into d/q coordinates in order to determine the compensation values id_comp, iq_comp therefrom. A filter 1060 is preferably used to determine the compensation values id_comp, iq_comp.

[0176] In one embodiment, the compensation values id_comp, iq_comp are used to convert the target values i.sub.d*, i.sub.q* into a distortion variable i d**, iq**, which are transformed into abc coordinates and are used to determine the driver signals T using a carrier signal R.

[0177] In another embodiment, the parameters i.sub.d_LUT, i.sub.q_LUT in the database are used to convert the target values i.sub.d*, i.sub.q* into a distortion variable i.sub.d**, i.sub.q**, which are transformed into abc coordinates and are used to determine the driver signals T using a carrier signal R.

[0178] The current i.sub.a, i.sub.b, i.sub.c generated by the active rectifier can be optimized, in particular noise-optimized, by means of the compensation values id_comp, iq_comp or the parameters i.sub.d_LUT, i.sub.q_LUT.

[0179] In one preferred embodiment, depending on the operating mode of the converter and/or the wind power installation, the control unit 1000 chooses between the compensation values id_comp, iq_comp and the parameters id_LUT, iq_LUT in the database LUT. For this purpose, the control unit 1000 has a closed-loop controller changeover means 1050, for example. The control unit 1000 therefore has both open-loop control based on a database LUT and closed-loop control based on a closed-loop control difference. Depending on the operating mode, the control unit can choose between open-loop control and closed-loop control.

[0180] The control variables id**, iq** represent, in particular, the total closed-loop control error of a (stator) system of the generator and are broken down into abc coordinates ia**, ib**, ic** corresponding to the phases a, b, c of the system and are compared with the actual currents ia, ib, ic of the respective phase a, b, c, are then possibly amplified and compared with a triangular signal R, in particular in order to determine the driver signals T for the switches of the active rectifier.

[0181] Each electrical system 122, 124 preferably has an active rectifier 132′, 132″ which is respectively controlled by a control unit 1000 described herein using the driver signals T.

[0182] FIG. 4C schematically shows, by way of example, a control module (e.g., control circuit) 1010 of a control unit 1000 for varying a frequency of the signal.

[0183] The control module 1010 is configured to change the frequency f.sub.R of the signal R, for example, in a predetermined frequency range Δf.

[0184] This can be carried out using a ramp r, for example.

[0185] The slope or rise of the ramp r is based in this case on the predetermined frequency range Δf and the period duration of the stator currents T.sub.s, for example, on the basis of the number of pole pairs p of the generator and/or the rotor speed n.sub.rot of the generator, preferably by means of

[00001]$T_s=\frac{60}{n_{rot}*p}.$

[0186] For example, if the rotor speed is approximately 7.7 rpm and the number of pole pairs of the generator is 57, the period duration of the stator currents is approximately 136.7 ms.

[0187] In one preferred embodiment, and if the generator has two (stator) systems, this frequency change or smearing is selected for both systems.

[0188] The frequency variation for smearing is, for example, 5% of the frequency of the carrier signal. If the carrier signal has a frequency of 700 Hz, for example, the frequency variation for smearing is 35 Hz.

[0189] It is therefore also proposed, in particular, to select the same smearing for a plurality of systems.

[0190] FIG. 5 schematically shows, by way of example, the sequence of a method 500 for controlling a converter 130, in particular an active rectifier 132′, 132″, in one embodiment.

[0191] The converter is first of all operated in a first operating mode MODE1, for example, in a power-optimized operating mode MODE1. This is indicated by block 505.

[0192] If the wind power installation, for example, then exceeds a predetermined limit value for an acoustic variable, there is a changeover to a second operating mode MODE2, in particular as described herein.

[0193] The second operating mode MODE2 is noise-optimized, for example, and is designed, in particular, as described below.

[0194] In a first step 510 of the second operating mode MODE2, at least one target value S* is specified for the converter 130, preferably a target current value in d/q coordinates.

[0195] In addition, in a further step 520 of the second operating mode MODE2, a carrier signal R is specified for the converter 130, preferably a sawtooth signal.

[0196] In a further step 530 of the second operating mode MODE2, an actual value S is then captured, in particular an actual current value of the converter 130, preferably in abc coordinates. In a further step 540, a distortion variable E is then determined from the target value S* specified in this manner and the actual value S captured in this manner, in particular as shown in FIGS. 4A and 4B. The distortion variable E is preferably determined using a compensation value COMP and/or an offset. The compensation value COMP is preferably determined by means of closed-loop control and the offset is specified by a database.

[0197] A driver signal T for the converter 130, and in particular for the switches of the converter 130, is determined from the distortion variable E determined in this manner and the signal R, for example, by means of comparison. This is indicated by block 550.

[0198] FIG. 6 schematically shows, by way of example, determination of a driver signal T for the converter on the basis of the distortion variable E and the carrier signal R.

[0199] The carrier signal R is designed as described herein.

[0200] In particular, the carrier signal R has an amplitude R and a frequency fR.

[0201] The distortion variable E, for example, is compared with this carrier signal R in order to generate corresponding driver signals T.

[0202] The distortion variable E is likewise designed as described herein.

[0203] In particular, the distortion variable E has an amplitude E{circumflex over ( )} and a frequency fE.

[0204] For example, a carrier signal R in the form of a triangle and the distortion variable E are used to determine the driver signals T.

[0205] The carrier signal R has a frequency of approximately 700 Hz, for example. The distortion variable has a frequency of approximately 50 Hz, for example. In addition, the amplitude of the carrier signal is at least twice as large as the amplitude of the distortion variable.

[0206] If the present value of the distortion variable E is greater than the carrier signal R, the driver signal T is equal to 1 and accordingly a switch of the converter is at position 1, that is to say is switched on, for example.

[0207] If the distortion variable E, for example, then falls below the carrier signal R at the time t1, the driver signal T becomes equal to 0 and the corresponding switch of the converter is switched to position 0, that is to say is switched off, for example.

[0208] If the distortion variable E then exceeds the carrier signal R again at the time t2, the driver signal T becomes equal to 1 and the corresponding switch of the converter is switched to position 1 again.

[0209] A corresponding procedure then takes place at the times t3 and t4.

[0210] However, the driver signals T can also be accordingly determined using the extended distortion variable E* described herein or the modulation signal U described herein.

[0211] The various embodiments described above can be combined to provide further embodiments. These and other changes can be made to the embodiments in light of the above-detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the disclosure.