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. The method includes 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, comprising: converting the distortion variable to form an extended distortion variable or a modulation signal.

3. The method according to claim 2, wherein the extended distortion variable or the modulation signal takes into account at least one system state of the converter.

4. The method according to claim 2, wherein converting the distortion variable includes amplifying or integrating the distortion variable.

5. The method according to claim 2, wherein determining the driver signals includes comparing the distortion variable, the extended distortion variable, or the modulation signal with the carrier signal.

6. The method according to claim 1, wherein determining the driver signals includes: determining the driver signals based on an offset that takes an operating point into account; or determining the driver signals by feeding forward the target value.

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

8. The method according to claim 1, comprising: setting a single-phase current of the electrical system based on the carrier signal.

9. The method The method according to claim 1, comprising: generating the carrier signal as a triangular signal, a sinusoidal signal, or a square-wave signal.

10. The method according to claim 2, wherein: the carrier signal has an amplitude and a frequency, the distortion variable has an amplitude and a frequency, the extended distortion variable has an amplitude and a frequency, the modulation signal has an amplitude and a frequency, and wherein: the amplitude of the carrier signal is greater than the amplitude of the distortion variable, the amplitude of the extended distortion variable, or the amplitude of the modulation signal, or the frequency of the carrier signal is greater than the frequency of the distortion variable, the frequency of the extended distortion variable, or the frequency of the modulation signal.

11. The method according to claim 10, wherein: the amplitude of the carrier signal is five times greater than the amplitude of the distortion variable, the amplitude of the extended distortion variable, or the amplitude of the modulation signal, and/or the frequency of the carrier signal is ten times greater than the frequency of the distortion variable, the frequency of the extended distortion variable, or the frequency of the modulation signal.

12. The method according to claim 1, wherein the actual value representative of the current includes a three-phase overall system and each phase of the three-phase overall system.

13. The method according to claim 1, wherein the target value, the actual value, the distortion variable, and/or an offset are in d/q coordinates.

14. The method according to claim 1, wherein: the target value is first target value of a first electrical system of the generator, the carrier signal is a first carrier signal of the first electrical system, the actual value is a first actual value of the first electrical system, the distortion variable is a first distortion variable of the first electrical system and the driver signals are first driver signals of the first electrical system, the method includes: specifying a second target value of a second electrical system of the generator; specifying a second carrier signal of the second electrical system of the generator; receiving a second actual value representative of a current of the second electrical system of the generator; determining a second distortion variable of the second electrical system of the generator; and determining second driver signals of the second electrical system of the generator, the first carrier signal and the second carrier signal are identical and are offset from each other by a phase angle.

15. The method according to claim 14, wherein the phase angle is between 30° and 120°.

16. The method according to claim 1, comprising: varying the carrier signal during operation.

17. The method according to claim 16, wherein the carrier signal is varied using a ramp function and based on a rotor speed of the generator and by a value in a frequency range between 0 and 10 per cent.

18. A controller, comprising: an input; and an output configured to be coupled to a converter, wherein the controller is configured to: specify a target value for the converter; specify a carrier signal for the converter; receive an actual value representative of a current of an electrical system of a generator; determine a distortion variable from the target value and the actual value; and determine driver signals for the converter based on the distortion variable and the carrier signal.

19. A wind power installation, comprising: a controller as claimed in claim 18; and the converter, wherein the output of the controller is coupled to the controller.

20. The wind power installation according to claim 19, wherein the converter has at least one generator-side active rectifier that is operated using the controller.

21. The wind power installation according to claim 19, wherein: the generator includes two stator systems that are offset from each other and coupled to an active rectifier, and the controller separately controls each stator system of the two stator systems.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0104] 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.

[0105] FIG. 1 schematically shows, by way of example, a perspective view of a wind power installation in one embodiment.

[0106] FIG. 2 schematically shows, by way of example, a structure of an electrical phase section of a wind power installation in one embodiment.

[0107] FIG. 3 schematically shows, by way of example, the structure of a converter.

[0108] FIG. 4A schematically shows, by way of example, the structure of a control unit (e.g., controller) of a converter in one embodiment.

[0109] FIG. 4B schematically shows, by way of example, the structure of a control unit (e.g., controller of a converter in one preferred embodiment.

[0110] FIG. 4C schematically shows, by way of example, the structure of a control unit (e.g., controller of a converter in a further preferred embodiment.

[0111] FIG. 4D schematically shows, by way of example, a control module (e.g., control circuit) of a control unit (e.g., controller) for varying a frequency of the signal.

[0112] FIG. 5 schematically shows, by way of example, the sequence of a method for controlling a converter in one embodiment.

[0113] 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

[0114] FIG. 1 schematically shows, by way of example, a perspective view of a wind power installation 100.

[0115] 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.

[0116] The wind power installation 100 has a tower 102 and a nacelle 104.

[0117] An aerodynamic rotor 106 with a hub 110 is arranged on the nacelle 104.

[0118] 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°.

[0119] 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.

[0120] The wind power installation 100 has an aerodynamic rotor 106 which is mechanically connected to a generator 120 of the wind power installation 100.

[0121] 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.

[0122] 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.

[0123] 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.

[0124] The converter modules 130′, 130″ have an active rectifier 132′ at a converter module input.

[0125] 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.

[0126] The converter 130 or the converter modules 130′, 130″ is/are preferably in the form of (a) direct converter(s) (back-to-back converter).

[0127] 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.

[0128] 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.

[0129] 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.

[0130] 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.

[0131] 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.

[0132] 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

[0133] 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.

[0134] 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.

[0135] 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.

[0136] 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. The wind power installation control unit 160 also comprises a control unit (e.g., controller) 1000, described herein, for the converter 130.

[0137] 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.

[0138] 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.

[0139] In this case, the converter 130 comprises, in particular, two active rectifiers 132′, 132″:

[0140] 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.

[0141] 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.

[0142] 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 i.sub.a′, i.sub.b′, i.sub.c′, i.sub.a″, i.sub.b″, i.sub.c″ in the stator of the generator 120.

[0143] FIG. 4A schematically shows, by way of example, the structure of a control unit (e.g., controller) 1000 of a converter 130, in particular for an active rectifier 132′, 132″.

[0144] The control unit 1000 determines a distortion variable E from a target value S* and an actual value S.

[0145] The target value S* and the actual value S are preferably physical variables of the converter, for example an alternating current Lso11 to be generated by the active rectifier 132′, 132″ or an alternating current List generated by the active rectifier 132′, 132″.

[0146] The distortion variable E is preferably determined from a difference between the target value S* and the actual value S and can therefore also be referred to as a closed-loop control error or measurement error. If the target value S* is a target current I_soll and the actual value S is an actual current I_ist, the distortion variable E can also be referred to as a distortion current.

[0147] 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″.

[0148] 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.

[0149] For this purpose, the carrier signal R may be, for example, in the form of a triangular signal, in particular with or without hysteresis.

[0150] The control unit 1000 is therefore in the form of a (ramp) comparison controller, in particular.

[0151] FIG. 4B schematically shows, by way of example, the structure of a control unit 1000 of a converter 130 in one preferred embodiment, in particular for an active rectifier 132′, 132″.

[0152] The control unit 1000 determines a distortion variable E from a target value S* and an actual value S.

[0153] The target value S* and the actual value S are, for example, physical variables generated by the converter, for example a current generated by the converter.

[0154] The distortion variable E may be determined, for example, from a difference between the target value S* and the actual value S and may therefore also be referred to as a closed-loop control error, for example.

[0155] The distortion variable E is then integrated by means of a PI element to form an extended distortion variable E*.

[0156] Depending on the design of the controller 1000 and/or the physical variables used, a gain k of the distortion variable E and/or a gain of the extended distortion variable E* by a factor of k may be expedient, where k is preferably between 2 and 10.

[0157] In addition, the target value S* is fed forward and is added to an offset A or a compensation value to form an extended offset A*.

[0158] The offset A or compensation value takes into account an operating point of the converter, for example.

[0159] The extended offset A* is then added to the extended distortion variable E* to form a control variable U which is compared with a carrier signal R in order to generate driver signals T for the converter 130.

[0160] For example, the control variable U can be functionally compared with the carrier signal R in such a manner that each point of intersection between the control variable U and the carrier signal R is used as a trigger point for a driver signal T.

[0161] FIG. 4C schematically shows, by way of example, the structure of a control unit 1000 of a converter 130 in a further preferred embodiment, in particular for an active rectifier 132′, 132″.

[0162] The control unit 1000 is constructed substantially as in FIG. 2, wherein the target value S*, the actual value S and the offset A are present in d/q coordinates and are additionally converted into abc coordinates.

[0163] The target value S* is a target current value i.sub.d*, i.sub.q* in d/q coordinates.

[0164] The d component of the target current i.sub.d* is first of all compared with the d component of the actual current i.sub.d. In particular, a difference is formed from the d component of the target current i.sub.d* and the d component of the actual current i.sub.d in order to determine a d component of the distortion current E.sub.d.

[0165] The distortion current E.sub.d is then passed via a PI element or PI controller in order to obtain an integrated distortion current E.sub.d*.

[0166] In addition, the d component of the target current i.sub.d* is fed forward and is added to a d component of a compensation current i_.sub.compd and is added to the integrated distortion current E.sub.d* in order to obtain a control variable i.sub.d**.

[0167] Furthermore, the q component of the target current iq* is first of all compared with the q component of the actual current iq. In particular, a difference is formed from the q component of the target current iq* and the q component of the actual current i.sub.q in order to determine a q component of the distortion current E.sub.q.

[0168] The distortion current E.sub.q is then passed via a PI element or PI controller in order to obtain an integrated distortion current E.sub.q*.

[0169] In addition, the q component of the target current i.sub.q* is fed forward and is added to a q component of a compensation current i_.sub.compq and is added to the integrated distortion current E.sub.q* in order to obtain a control variable i.sub.q**.

[0170] The control variables i.sub.d**, i.sub.q** represent, in particular, the total closed-loop control error of a (stator) system of the generator and are broken down into abc coordinates i.sub.a**, i.sub.b**, i.sub.c** corresponding to the phases a, b, c of the system and are compared with the actual currents i.sub.a, i.sub.b, i.sub.c 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.

[0171] 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.

[0172] FIG. 4D 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.

[0173] 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.

[0174] This can be carried out using a ramp r, for example.

[0175] 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]$T_s=\frac{60}{n_{rot}*p}.$

[0176] 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.

[0177] In one preferred embodiment, and if the generator has two (stator) systems, this frequency change or smearing is selected for both systems.

[0178] 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.

[0179] It is therefore also proposed, in particular, to select the same smearing for a plurality of systems.

[0180] 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.

[0181] In a first step 510, at least one target value S* is specified for the converter 130.

[0182] In addition, in a further step 520, a signal R is specified for the converter 130.

[0183] In a further step 530, an actual value S, in particular of the converter 130, is then captured.

[0184] 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.

[0185] 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.

[0186] 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.

[0187] The carrier signal R is designed as described herein.

[0188] In particular, the carrier signal R has an amplitude {circumflex over (R)} and a frequency f.sub.R.

[0189] The distortion variable E, for example, is compared with this carrier signal R in order to generate corresponding driver signals T.

[0190] The distortion variable E is likewise designed as described herein.

[0191] In particular, the distortion variable E has an amplitude Ê and a frequency f.sub.E.

[0192] 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.

[0193] 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.

[0194] 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.

[0195] 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.

[0196] 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.

[0197] A corresponding procedure then takes place at the times t3 and t4.

[0198] 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.

LIST OF REFERENCE SIGNS

[0199] 100 Wind power installation

[0200] 100′ Electrical phase section, in particular of the wind power installation

[0201] 100″ Detail of the electrical phase section

[0202] 102 Tower, in particular of the wind power installation

[0203] 104 Nacelle, in particular of the wind power installation

[0204] 106 Rotor, in particular of the wind power installation

[0205] 108 Rotor blade, in particular of the wind power installation

[0206] 110 Hub, in particular of the wind power installation

[0207] 120 Generator, in particular of the wind power installation

[0208] 122 First electrical system, in particular of the generator

[0209] 124 Second electrical system, in particular of the generator

[0210] 130 Converter, in particular power converter of a wind power installation

[0211] 130′ Converter module, in particular for the first electrical system

[0212] 130″ Converter module, in particular for the second electrical system

[0213] 132 Active rectifier

[0214] 132′ Active rectifier module, in particular for the first electrical system

[0215] 132″ Active rectifier module, in particular for the second electrical system

[0216] 135′ DC voltage, in particular for the first electrical system

[0217] 135″ DC voltage, in particular for the second electrical system

[0218] 137 Inverter

[0219] 137′ Inverter module, in particular for the first electrical system

[0220] 137″ Inverter module, in particular for the second electrical system

[0221] 140 Node

[0222] 150 Transformer, in particular of the wind power installation

[0223] 160 Wind power installation control unit

[0224] 162 Current capture, in particular of the wind power installation control unit

[0225] 162 Voltage capture, in particular of the wind power installation control unit

[0226] 500 Method for controlling a converter

[0227] 510 Step: Specify a target value

[0228] 520 Step: Specify a signal

[0229] 530 Step: Capture an actual value

[0230] 540 Step: Determine a distortion variable

[0231] 550 Step: Determine a driver signal

[0232] 1000 Control unit, in particular of the converter

[0233] 1010 Control module, in particular of the control unit

[0234] 2000 Electrical supply network

[0235] f.sub.R Frequency, in particular of the signal

[0236] i_compCompensation current, in particular for the active rectifier

[0237] i_comp.sub.d d component, in particular of the compensation current

[0238] i_comp.sub.q q component, in particular of the compensation current

[0239] ig Total current, in particular of a system of the generator

[0240] iG Total current, in particular of the converter

[0241] i.sub.d d component, in particular of the actual alternating current

[0242] i.sub.q q components, in particular of the actual alternating current

[0243] i.sub.d* d component, in particular of the target alternating current

[0244] i.sub.q* q components, in particular of the target alternating current

[0245] i.sub.d** d component, in particular of the distortion current

[0246] i.sub.q** q components, in particular of the distortion current

[0247] i.sub.a Alternating current of a first phase, in particular of the generator

[0248] i.sub.b Alternating current of a second phase, in particular of the generator

[0249] i.sub.c Alternating current of a third phase, in particular of the generator

[0250] i.sub.a′ First alternating current, in particular of a first active rectifier

[0251] i.sub.b′ Second alternating current, in particular of a first active rectifier

[0252] i.sub.c′ Third alternating current, in particular of a first active rectifier

[0253] i.sub.a″ First alternating current, in particular of a second active rectifier

[0254] i.sub.b″ Second alternating current, in particular of a second active rectifier

[0255] i.sub.c″ Third alternating current, in particular of a second active rectifier

[0256] i_ist Actual alternating current, in particular of the active rectifier

[0257] i_soll Target alternating current, in particular of the active rectifier

[0258] n.sub.rot Speed, in particular of the generator

[0259] p Number of pole pairs of the generator

[0260] r Ramp, in particular for changing the frequency

[0261] A Offset

[0262] A* Extended offset

[0263] E Distortion variable, in particular distortion current

[0264] E* Extended distortion variable

[0265] R Carrier signal

[0266] S Actual value, in particular of an electrical current

[0267] S* Target value, in particular of the electrical current

[0268] T Driver signals, in particular for the active rectifier

[0269] T.sub.s Period duration, in particular of a ramp

[0270] U Modulation signal

[0271] ΦPhase angle, in particular between the first signal and the second signal

[0272] 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.