WO2006030183A1 - Controle d'un generateur asynchrone a alimentation double - Google Patents

Controle d'un generateur asynchrone a alimentation double Download PDF

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Publication number
WO2006030183A1
WO2006030183A1 PCT/GB2005/003471 GB2005003471W WO2006030183A1 WO 2006030183 A1 WO2006030183 A1 WO 2006030183A1 GB 2005003471 W GB2005003471 W GB 2005003471W WO 2006030183 A1 WO2006030183 A1 WO 2006030183A1
Authority
WO
WIPO (PCT)
Prior art keywords
stator
signal
controller
rotor
auxiliary
Prior art date
Application number
PCT/GB2005/003471
Other languages
English (en)
Inventor
Mike Hughes
Original Assignee
The University Of Manchester
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from GB0420416A external-priority patent/GB0420416D0/en
Priority claimed from GB0508618A external-priority patent/GB0508618D0/en
Application filed by The University Of Manchester filed Critical The University Of Manchester
Publication of WO2006030183A1 publication Critical patent/WO2006030183A1/fr

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Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P9/00—Arrangements for controlling electric generators for the purpose of obtaining a desired output
    • H02P9/007—Control circuits for doubly fed generators
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03D—WIND MOTORS
    • F03D7/00—Controlling wind motors 
    • F03D7/02—Controlling wind motors  the wind motors having rotation axis substantially parallel to the air flow entering the rotor
    • F03D7/0272—Controlling wind motors  the wind motors having rotation axis substantially parallel to the air flow entering the rotor by measures acting on the electrical generator
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03D—WIND MOTORS
    • F03D9/00—Adaptations of wind motors for special use; Combinations of wind motors with apparatus driven thereby; Wind motors specially adapted for installation in particular locations
    • F03D9/20—Wind motors characterised by the driven apparatus
    • F03D9/25—Wind motors characterised by the driven apparatus the apparatus being an electrical generator
    • F03D9/255—Wind motors characterised by the driven apparatus the apparatus being an electrical generator connected to electrical distribution networks; Arrangements therefor
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P21/00—Arrangements or methods for the control of electric machines by vector control, e.g. by control of field orientation
    • H02P21/05—Arrangements or methods for the control of electric machines by vector control, e.g. by control of field orientation specially adapted for damping motor oscillations, e.g. for reducing hunting
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P21/00—Arrangements or methods for the control of electric machines by vector control, e.g. by control of field orientation
    • H02P21/06—Rotor flux based control involving the use of rotor position or rotor speed sensors
    • H02P21/10—Direct field-oriented control; Rotor flux feed-back control
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P9/00—Arrangements for controlling electric generators for the purpose of obtaining a desired output
    • H02P9/48—Arrangements for obtaining a constant output value at varying speed of the generator, e.g. on vehicle
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
    • F05B2270/00—Control
    • F05B2270/30—Control parameters, e.g. input parameters
    • F05B2270/327—Rotor or generator speeds
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P2101/00—Special adaptation of control arrangements for generators
    • H02P2101/15—Special adaptation of control arrangements for generators for wind-driven turbines
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P2207/00—Indexing scheme relating to controlling arrangements characterised by the type of motor
    • H02P2207/07—Doubly fed machines receiving two supplies both on the stator only wherein the power supply is fed to different sets of stator windings or to rotor and stator windings
    • H02P2207/073—Doubly fed machines receiving two supplies both on the stator only wherein the power supply is fed to different sets of stator windings or to rotor and stator windings wherein only one converter is used, the other windings being supplied without converter, e.g. doubly-fed induction machines
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/70—Wind energy
    • Y02E10/72—Wind turbines with rotation axis in wind direction

Definitions

  • the present invention relates to a controller for a doubly-fed induction generator (DFIG) and to a method of controlling the same.
  • DFIG doubly-fed induction generator
  • the method allows improved control of the power supply and terminal voltage of a DFIG.
  • the method also allows the provision of support to an electricity network under fault conditions.
  • a synchronous generator comprises a rotor having a winding, which is supplied with a DC rotor voltage via slip rings. This rotor voltage gives rise to a rotor flux described by a vector.
  • the rotor rotates within a stator which comprises a three phase winding connected to an electricity network. Therefore, the stator winding has a stator flux described by a vector rotating at a stator frequency.
  • the stator frequency is fixed by the frequency on the electricity network.
  • the rotor is driven by a turbine at a rotational speed substantially synchronised to the rotational speed of the stator flux vector. Power is transferred from the rotor to the stator due to the interaction of the rotor and stator flux vectors.
  • the magnitude of the power supply output of the stator is dependent on the power output of the prime mover of the system.
  • the prime mover is normally a steam, gas or hydraulic turbine.
  • the angular position of the rotor flux vector relative to the stator flux vector is dependent upon the stator power supply output.
  • the magnitude of the stator terminal voltage of a synchronous generator can be controlled by varying the magnitude of the DC voltage supplied to the rotor.
  • This type of control is known as Automatic Voltage Regulation and is implemented by a controller known as an Automatic Voltage Regulator (AVR).
  • AVR Automatic Voltage Regulator
  • the grid code includes the requirement of the capability to provide voltage support and the ability to remain connected to the network following short term system faults.
  • the most commonly considered system fault is a three phase short circuit to ground that is quickly isolated by the opening of switchgear connected to the affected power line.
  • AVR supplies this level of control.
  • Wind turbines operate most efficiently if they are allowed to operate at a variable rotational speed.
  • the power extracted from the wind by a wind turbine can be maximised if the speed of the turbine is adjusted in accordance with the prevailing wind speed.
  • a synchronous generator requires the rotor to be rotated at a speed substantially synchronised to the stator frequency. Therefore, a wind generator is only able to run close to its maximum efficiency over a narrow band of wind speeds. At other times fixed speed wind generators run at reduced efficiency.
  • a squirrel cage induction generator An alternative form of generator known for simple wind farms is a squirrel cage induction generator.
  • Squirrel cage induction generators are used in the simplest form of wind farms.
  • a squirrel cage induction generator has a rotor comprising a cylinder of short circuited bars and operates at a substantially fixed rotational speed. This substantially fixed speed operation of a squirrel cage induction generator therefore does not permit the wind turbine to operate at maximum efficiency.
  • squirrel cage induction generators perform badly when faced with network fault conditions and usually require power factor correction equipment to satisfy operational requirements.
  • a synchronous generator requires a controlled excitation system, unlike a squirrel cage induction generator. Therefore, due to economy and simplicity squirrel cage induction generators are used in earlier forms of wind farm in preference to synchronous generators, though neither is ideal.
  • a DFIG comprises a rotor having a three phase winding supplied with a rotor voltage, which can be described by a vector via slip rings from a converter system.
  • the converter system is powered by the stator terminals.
  • the stator comprises a three phase winding having a stator flux described by a vector rotating at the stator frequency.
  • the stator frequency is fixed by the frequency of the electricity network.
  • the converter system provides a variable frequency three phase voltage supply to the rotor. The magnitude and phase of the rotor voltage vector, with respect to the stator flux vector, can be controlled.
  • the rotational speed of the rotor flux vector is equal to the rotational speed of the stator flux vector.
  • the rotor speed (the speed of physical rotation of the rotor) can be faster or slower than the rotational speed of the stator flux vector.
  • the difference between the rotational speed of the rotor flux vector and the rotational speed of the rotor is known as the slip speed.
  • the slip speed is the speed at which the stator flux vector rotates relative to the rotor. Under steady state conditions the slip speed depends upon whether the rotor speed is greater than the rotational speed of the stator flux vector (super-synchronous operation) or slower (sub-synchronous operation).
  • the rotor flux vector rotates synchronously with the stator flux vector, as is the case with synchronous generators. Consequently, the rotational speed of the rotor can vary, in order to maximise the output torque of the wind turbine according to the prevailing wind conditions, and hence to maximise the power developed by the wind turbine and hence the power supply of the DFIG based wind farm.
  • the rotational speed of the rotor flux vector relative to the rotor can be controlled by varying the frequency of the rotor voltage vector.
  • the magnitude and the angular position of the rotor voltage vector demanded of the converter system are controlled by a controller.
  • the converter system provides the rotor with a three phase rotor voltage, which affects the magnitude and angular position of the rotor flux vector.
  • Conventional DFIG controllers to date have concentrated on the provision of an adjustable operating speed of the rotor to maximise turbine power output, the maintenance of the required stator terminal voltage and power supply and the control of the generator torque to match that of the wind turbine.
  • the rotor voltage vector is calculated in terms of direct and quadrature (d and q) components referenced to a synchronously rotating reference frame.
  • the d axis of the frame can be arranged to coincide with the stator flux vector.
  • the d component of the rotor voltage vector is used to exercise control over the stator terminal voltage magnitude or the power factor.
  • the power factor defines the phase relationship between the stator terminal voltage and the stator current.
  • the d axis rotor current error is processed to provide the demanded value of the d axis component of the rotor voltage vector.
  • the q axis component of rotor voltage is used to exercise control over the generator torque via control over the q axis value of the rotor current.
  • the q axis rotor current error is processed to provide the demanded value of the q axis component of the rotor voltage vector.
  • a DFIG controller that provides substantially independent control of the stator terminal voltage and the stator electrical power supply via control of the magnitude and the angular position of the rotor flux vector.
  • a DFIG controller with operational and control compatibility with conventional power stations and with the ability to contribute to network support and operation as required by the grid code. This can include one or more of the ability to contribute to voltage support and recovery following network faults, a positive contribution to overall network damping and the provision of short term frequency support to the network in the event of loss of network generation.
  • the present invention provides a controller for a doubly-fed induction generator, the doubly-fed induction generator comprising: a stator comprising stator terminals arranged to provide a three phase stator terminal voltage supply, and a three phase winding arranged to provide a stator flux described by a vector rotating at a stator frequency, and arranged to provide a stator electrical power supply at the stator frequency; and a rotor comprising a three phase winding arranged to provide a rotor flux described by a vector rotating at substantially the stator frequency at an angular position relative to the stator flux vector; wherein the controller is arranged to determine a control signal to cause a change substantially only in the magnitude of the rotor flux vector in response to a stator terminal voltage error signal, and to determine a control signal to cause a change substantially only in the angular position of the rotor flux vector relative to the stator flux vector, in response to a stator electrical power supply error signal.
  • a DFIG controller By providing independent control of the magnitude and the angular position of the rotor flux vector, substantially independent control over the stator terminal voltage vector and the power supply can thus be achieved.
  • This independent control allows a DFIG controller to emulate the control of a controller for a synchronous generator.
  • the control of the stator terminal voltage is similar to that provided by an Automatic Voltage Regulator (AVR) for a synchronous generator.
  • AVR Automatic Voltage Regulator
  • the control of the stator electrical power supply output from the DFIG provides the ability to maintain the generator power (or torque) at a value that matches that of a wind turbine driving the generator.
  • AVR Automatic Voltage Regulator
  • Such a controller allows the provision of a DFIG satisfying the grid code requirements for fault ride through. This enables DFIGs to contribute to network operation by providing voltage support and recovery following network faults.
  • stator terminal voltage error signal is indicative of the difference between the magnitude of the stator terminal voltage and the magnitude of a predetermined stator terminal voltage reference signal.
  • stator electrical power supply error signal is indicative of the difference between the stator electrical power supply and a predetermined stator electrical power supply reference signal.
  • the stator electrical power supply may be indicative of a torque exerted by the rotor.
  • control signals are indicative of a desired rotor voltage described by a vector, for supply to the rotor three phase winding.
  • the controller may be arranged to output said control signals in polar coordinate form, with respect to a reference frame rotating at stator frequency.
  • the controller can be arranged to output said control signals in rectangular coordinate form, with respect to a reference frame rotating at stator frequency.
  • the controller may be arranged to determine said control signals by comparing a rotor flux vector magnitude reference value and a value indicative of the actual magnitude of the rotor flux vector and comparing a rotor flux vector angular position reference value and a value indicative of the actual angular position of the rotor flux vector relative to the stator flux vector.
  • the controller may comprise a first compensator arranged to receive the stator terminal voltage error signal and determine a rotor flux vector magnitude reference value.
  • the first compensator comprises a proportional plus integral controller and a phase compensation element.
  • the controller may comprise a second compensator arranged to receive the stator electrical power supply error signal and determine a rotor flux vector angular position reference value relative to the stator flux vector angular position.
  • the second compensator may comprise a proportional plus integral controller and a phase compensation element.
  • the controller may further comprise at least one auxiliary controller, each auxiliary controller being arranged to determine an auxiliary control signal in response to at least one of a rotor speed signal, a stator electrical power supply signal, a slip signal and a stator frequency signal, the controller being arranged to utilise the auxiliary control signal to modify the value of a signal indicative of the desired angular position of the rotor flux vector relative to the stator flux vector.
  • a first auxiliary controller may be arranged to determine a first auxiliary control signal from a first auxiliary input signal comprising at least one of the rotor speed signal and the slip signal, the first auxiliary controller comprising a washout filter, an integrator, a compensator and an output value limiter.
  • a second auxiliary controller may be arranged to determine a second auxiliary control signal from a second auxiliary input signal comprising at least one of the rotor speed signal, the stator electrical power supply signal, the slip signal and the signal indicative of the stator frequency, the second auxiliary controller comprising a washout filter, a compensator, an amplifier and an output value limiter.
  • a third auxiliary controller may be arranged to determine a third auxiliary control signal from the stator frequency signal and at least one of the rotor speed signal and the slip signal, the third auxiliary controller being arranged to: determine a first resultant signal by washout filtering, first compensating, output value limiting and second compensating the stator frequency signal; determine a second resultant signal by washout filtering at least one of the rotor speed signal and the slip signal; determine an auxiliary error signal from the difference between the resultant signals; and determine the third auxiliary control signal by third compensating the auxiliary error signal.
  • the controller is arranged to selectively inhibit the operation of the first auxiliary controller, when the third auxiliary controller operates.
  • the signal indicative of the desired angular position of the rotor flux vector relative to the stator flux vector may comprise the rotor flux vector angular position reference value, the controller being arranged to utilise at least one of the auxiliary control signals to modify the rotor flux vector angular position reference value relative to the stator flux vector angular position.
  • the signal indicative of the desired angular position of the rotor flux vector relative to the stator flux vector may comprise the predetermined stator electrical power supply reference signal, the controller being arranged to utilise at least one of the auxiliary control signals to modify the predetermined stator electrical power supply reference signal.
  • the signal indicative of the desired angular position of the rotor flux vector relative to the stator flux vector may comprise an angular position of the desired rotor voltage vector, the controller being arranged to utilise at least one of the auxiliary control signals to modify the angular position of the desired rotor voltage vector.
  • the present invention provides a doubly-fed induction generator comprising a controller as described above.
  • the present invention provides a method of controlling a doubly-fed induction generator, the doubly-fed induction generator comprising: a stator comprising stator terminals arranged to provide a three phase stator terminal voltage supply, and a three phase winding arranged to provide a stator flux described by a vector rotating at a stator frequency and arranged to provide a stator electrical power supply at the stator frequency; and a rotor comprising a three phase winding arranged to provide a rotor flux described by a vector rotating at substantially the stator frequency at an angular position relative to the stator flux vector; the method comprising: determining a control signal to cause a change substantially only in the magnitude of the rotor flux vector in response to a stator terminal voltage error signal; and determining a control signal to cause a change substantially only in the angular position of the rotor flux vector relative to the stator flux vector, in response to a stator electrical power supply error signal.
  • the present invention provides a controller for a doubly-fed induction generator, the doubly-fed induction generator comprising: a stator comprising a three phase winding arranged to provide a stator flux described by a vector rotating at a stator frequency and arranged to provide a stator electrical power supply at the stator frequency; and a rotor comprising a three phase winding arranged to provide a rotor flux described by a vector rotating at substantially the stator frequency at an angular position relative to the stator flux vector; wherein the controller comprises at least one auxiliary controller, each auxiliary controller being arranged to determine an auxiliary control signal in response to at least one of a rotor speed signal, a slip signal, a stator frequency signal and a stator electrical power supply signal, the controller being arranged to utilise the auxiliary control signal to modify the value of a signal indicative of the desired angular position of the rotor flux vector relative to the stator flux vector.
  • a first auxiliary controller may be arranged to determine a first auxiliary control signal from a first auxiliary input signal comprising at least one of the rotor speed signal and the slip signal, the first auxiliary controller comprising a washout filter, an integrator, a compensator and an output value limiter.
  • a second auxiliary controller may be arranged to determine a second auxiliary control signal from a second auxiliary input signal comprising at least one of the rotor speed signal, the stator electrical power supply signal, the slip signal and the stator frequency signal, the second auxiliary controller comprising a washout filter, a compensator, an amplifier and an output value limiter.
  • a third auxiliary controller may be arranged to determine a third auxiliary control signal from the stator frequency signal and at least one of the rotor speed signal and the slip signal, the third auxiliary controller being arranged to: determine a first resultant signal by washout filtering, first compensating, output value limiting and second compensating the stator frequency; determine a second resultant signal by washout filtering at least one of the rotor speed signal and the slip signal; determine an auxiliary error signal from the difference between the resultant signals; and determine the third auxiliary control signal by third compensating the auxiliary error signal.
  • the controller is arranged to selectively inhibit the operation of the first auxiliary controller.
  • the controller may be arranged to determine a control signal to cause a change substantially only in the stator electrical power supply, in response to a stator electrical power supply error signal indicative of the difference between the stator electrical power supply and a predetermined stator electrical power supply reference signal, and the signal indicative of the desired angular position of the rotor flux vector relative to the stator flux vector may comprise the predetermined stator electrical power supply reference signal and the controller may be arranged to utilise at least one of the auxiliary control signals to modify the predetermined stator electrical power supply reference signal.
  • the signal indicative of the desired angular position of the rotor flux vector relative to the stator flux vector may comprise a signal indicative of a desired rotor voltage described by a vector, for supply to the rotor three phase winding, and the controller may be arranged to utilise at least one of the auxiliary control signals to modify the angular position of the desired rotor voltage vector.
  • the present invention provides a doubly-fed induction generator comprising a controller as described above.
  • the present invention provides a method of controlling a doubly-fed induction generator, the doubly-fed induction generator comprising: a stator comprising a three phase winding arranged to provide a stator flux described by a vector rotating at a stator frequency and arranged to provide a stator electrical power supply at the stator frequency; and a rotor comprising a three phase winding arranged to provide a rotor flux described by a vector rotating at substantially the stator frequency at an angular position relative to the stator flux vector; the method comprising: determining an auxiliary control signal in response to at least one of a rotor speed signal, a slip signal, a stator frequency signal and the stator electrical power supply signal; and utilising the auxiliary control signal to modify the value of a signal indicative of the desired angular position of the rotor flux vector relative to the stator flux vector.
  • the present invention provides a data carrier carrying computer program code means to cause a computer to carry out a method as described above.
  • the present invention provides a computer apparatus comprising: a program memory containing processor readable instructions; and a processor for reading and executing the instructions contained in the program memory; wherein said processor readable instructions comprise instructions controlling the processor to carry out a method as described above.
  • a further advantage of embodiments of the present invention is that the dynamic characteristic of the DFIG presented to the network can be made to resemble that of a synchronous generator.
  • a further advantage of embodiments of the present invention is that a DFIG generator can act as a power system stabiliser, and therefore provide damping to the network.
  • a further advantage of embodiments of the present invention is that in the event of the disconnection of a generator on the network a DFIG controller can provide a short term increase in power supply in order to provide frequency support. Further advantages of embodiments of the present invention will become readily apparent from the following description.
  • Figure 1 schematically illustrates a DFIG in combination with a controller in accordance with an embodiment of the present invention
  • Figure 2 illustrates a vector diagram representation of the operation of a synchronous generator
  • Figure 3 illustrates a vector diagram representation of the operation of a DFIG
  • Figure 4 schematically illustrates a controller for a DFIG in accordance with an embodiment of the present invention
  • Figure 5 schematically illustrates a first optional part of the controller for a DFIG of Figure 4;
  • Figure 6 schematically illustrates a second optional part of the controller for a DFIG of Figure 4.
  • Figure 7 schematically illustrates a controller for a DFIG in accordance with a further embodiment of the present invention.
  • Figure 8 schematically illustrates a first auxiliary controller in accordance with embodiments of the present invention
  • Figure 9 schematically illustrates a second auxiliary controller in accordance with embodiments of the present invention.
  • Figure 10 schematically illustrates a third auxiliary controller in accordance with embodiments of the present invention.
  • Figure 11 schematically illustrates a controller for a DFIG in accordance with a further embodiment of the present invention
  • Figure 12 schematically illustrates a controller for a DFIG in accordance with an additional embodiment of the present invention
  • Figure 13 schematically illustrates a controller for a DFIG in accordance with a further embodiment of the present invention
  • Figure 14 schematically illustrates a controller for a DFIG in accordance with an additional embodiment of the present invention
  • Figure 15 schematically illustrates a controller for a DFIG in accordance with a further embodiment of the present invention.
  • FIG. 1 this illustrates a DFIG 1 controlled by a controller 2 in accordance with an embodiment of the present invention.
  • the DFIG comprises a rotor 3, having a three phase winding 4, and a stator 5 having a three phase winding 6.
  • the rotor 3 rotates within the stator 5, and is driven by a wind turbine 7.
  • Stator 5 has three phase voltage terminals 8 which supply a stator terminal voltage V 5 and an electrical power supply P e to transformer 9.
  • Transformer 9 steps up the stator terminal voltage V 8 to a suitable level for provision to the network 10.
  • the stator three phase winding 6 provides a stator flux described by a vector ⁇ s which rotates at a stator frequency co s fixed by the network frequency.
  • a vector has a magnitude value and an angular position value.
  • DFIG 1 further comprises a converter system 11.
  • Converter system 11 comprises first and second converters 12 and 13.
  • First converter 12 has a three phase voltage input supplied by the stator terminals 8 and converts this to a DC voltage.
  • First converter 12 is fed from the stator terminals 8 via a reactive link.
  • First converter 12 supplies the DC voltage to second converter 13 via DC bus 14.
  • DC bus 14 is bridged by capacitor 15 to substantially remove any AC voltage component.
  • Second converter 13 converts the DC voltage to a rotor voltage described by a vector Vj.
  • the rotor voltage is supplied to the three phase winding 4 on the rotor 3 via slip rings.
  • the magnitude and phase of the rotor voltage vector V 1 are controllable.
  • Controller 2 determines a control signal Vj dem (desired rotor voltage vector) that is supplied to the second converter 13 to adjust V 1 .
  • Converter system 11 permits the two way transfer of power between the rotor 3 and the stator 5 connection to transformer 9. At super-synchronous speeds (the rotor 3 rotating faster than the stator flux vector ⁇ s ) the converter system 11 transfers power from the rotor 3 to the stator terminals 8. At sub-synchronous speeds (the rotor 3 rotating slower than the stator flux vector ⁇ s ) the rotor 3 absorbs power via the converter system 11 from the stator terminals 8.
  • the controller 2 in accordance with embodiments of the present invention can utilise a number of input signals derived from the DFIG 1 in order to control the desired rotor voltage vector V ⁇ em - These can include one or more of the stator electrical power supply P e supplied by the stator 5, the three phase values of the stator terminal voltage V 8 , the stator current Ij 8 , the rotor current Ir, the stator frequency co s , the slip speed s and the rotor speed ⁇ r . If the stator terminal voltage V 3 and the stator current Ij 3 are included as input signals, then other signals, for instance the stator electrical power supply P e , may be calculated, rather than require further inputs.
  • the controller 2 exercises independent control over the stator terminal voltage V 5 and the stator electrical output power supply P e by independently controlling the magnitude and angular position respectively of the rotor flux vector ⁇ r .
  • Control over the rotor flux vector ⁇ r can be achieved by controlling the desired rotor voltage vector V rd e m -
  • predetermined values for the desired values of the stator terminal voltage V 8 ⁇ and the power supply P eref are input to the controller 2.
  • the desired value for the stator output power supply P ere f can be calculated from the slip speed s by power controller 16.
  • stator terminal voltage and transient variations in the stator electrical power supply of a DFIG are separately controllable.
  • a DFIG controlled according to embodiments of the present invention satisfies the grid code requirements for fault ride through. Additionally, it is desirable that a DFIG provides the same level, or better, of network support and operation as provided by synchronous generators. If this capability is not provided then the operational characteristics of the network will vary widely as the proportion of synchronous generators and DFIGs varies. This would present severe difficulties to the network operator in providing the required level of stability and security.
  • Using conventional DFIG controllers such as the one described in the paper by Ekanayake et al whilst it is possible to provide control over the stator terminal voltage and the electrical power supply an undesirable level of interaction exists between the two.
  • a convenient method of representing a generator for the purposes of analysis, simulation and control is in terms of a synchronously rotating reference frame having direct and quadrature axes (d and q axes), with the q axis chosen to align with one of the vector quantities within the generator.
  • the controller 2 utilises a control strategy that aims to emulate the control action of a conventional synchronous generator.
  • a vector diagram representation of the operating conditions of such a conventional round rotor synchronous generator is illustrated in Figure 2.
  • E g represents an internally generated voltage within the stator.
  • the q axis is chosen to align with the internally generated voltage Eg.
  • the internally generated voltage E g rotates synchronously at the stator frequency ⁇ s . Therefore, all other rotating vectors can be described in terms of their magnitude and angular position relative to the internally generated voltage E g within the same reference frame.
  • the magnitude of the internally generated voltage E g is determined by a rotor flux vector ⁇ fd, with the internally generated voltage E g being 90° out of phase with the rotor flux vector ⁇ fc i- Therefore the rotor flux vector ⁇ fd is aligned with the d axis of the reference frame.
  • the physical position of the field winding of the rotor with respect to a rotating stator terminal voltage vector E t defines the position of the rotor flux vector ⁇ fd and is aligned with the d axis of the chosen synchronously rotating reference frame.
  • the internally generated voltage E g has the same magnitude as the field voltage E fd , which is the DC voltage, supplied to the rotor.
  • the magnitude of the stator terminal voltage vector E 1 is dependent upon the magnitude of the internally generated voltage E g .
  • the difference between the two vectors can be calculated from the stator current vector L 5 , as jX s I s , where X 8 is the synchronous reactance of the generator. Therefore the stator terminal voltage vector E t can be controlled by controlling the magnitude of the field voltage E fd supplied to the rotor.
  • the rotor angle ⁇ r is defined as the angle between the internally generated voltage Eg and the stator terminal voltage vector E t .
  • the rotor angle ⁇ r is determined by the output power of the generator.
  • control can be exercised only over the field voltage magnitude, so that independent control of the stator terminal voltage vector E t and transient variations in the stator electrical power supply is not possible.
  • the magnitude of the rotor flux vector can be adjusted by the excitation control scheme, the position of the rotor flux vector is fixed by the physical position of the rotor itself.
  • FIG 3 illustrates an equivalent vector diagram representation of the operating conditions of a DFIG.
  • Ej g represents the internally generated voltage vector in the stator (often referred to as the voltage behind the transient reactance).
  • the magnitude of the internally generated voltage vector E; g depends on the magnitude of the rotor flux vector ⁇ f .
  • the rotor flux vector ⁇ r is dependent upon the generator stator and rotor currents, but can be manipulated by adjustment of the rotor voltage vector Y x .
  • the magnitude of the stator terminal voltage vector V 8 is dependent upon the magnitude of the internally generated voltage Ejg. Assuming negligible stator resistance, the difference between the two vectors can be calculated from the stator current vector Ij 5 , as jX'Ij s , where X' is the transient reactance of the generator.
  • the transient reactance X' can be calculated from the stator self inductance L ss , the mutual inductance between the stator and the rotor L m and the rotor self inductance L rr as follows:
  • the stator terminal voltage vector V 8 can be controlled by controlling the magnitude of the rotor voltage vector Vj supplied to the rotor.
  • a synchronously rotating reference frame is normally defined with the q axis chosen to align with the stator terminal voltage vector V 3 .
  • the stator terminal voltage vector V 5 rotates synchronously with a stator flux vector ⁇ s .
  • a pseudo rotor angle ⁇ ; g exists between the internally generated voltage vector Ej g and the stator terminal voltage vector V 5 .
  • the pseudo rotor angle ⁇ j g is determined by the output power supply P e of the generator.
  • pseudo rotor angle ⁇ j g refers to the fact that the physical position of the rotor can be varying with respect to the synchronously rotating reference frame. However, with the addition of the appropriate variable frequency rotor voltage vector Vj, the internally generated voltage vector Ej g can be held at a desired angular position with respect to the stator terminal voltage vector V 8 .
  • independent control of the stator terminal voltage V 8 and transient variations in the stator electrical power supply P e of a DFIG can be achieved by independent control of the magnitude and the angular position respectively of the internally generated voltage Ej g .
  • the internally generated voltage Ej g is directly related to the rotor flux vector ⁇ r (Eig - j ⁇ r (L m /L rr )) then it is also true that this independent control can be achieved by independent control of the magnitude and the angular position respectively of the rotor flux vector ⁇ r .
  • a controller and a method are described for generating a control signal to cause a change substantially only in the magnitude of the rotor flux vector in response to a stator terminal voltage error signal, and to determine a control signal to cause a change substantially only in the angular position of the rotor flux vector relative to the stator flux vector, in response to a power supply error signal.
  • the controller is able to emulate the control of a synchronous generator with respect to the control over the magnitude of the rotor flux. Furthermore, by exercising transient control over the angular position of the rotor flux vector with respect to the stator flux vector, control over transient power variations is enabled. For a synchronous generator, such control over the angular position of the rotor flux vector and hence the transient power variations of the stator electrical power supply could only be achieved through refined turbine governor control of a form not currently available. Consequently, embodiments of the present invention offer a control capability beyond the scope of a conventional synchronous generator.
  • the preferred embodiment of the present invention provides a means of controlling the magnitude and the angular position (with respect to the stator flux vector ⁇ _ s ) of the rotor flux vector ⁇ r (or equivalently the magnitude and the angular position of the internally generated voltage Ej g ).
  • FIG. 4 illustrates a controller 20 for a DFIG in accordance with an embodiment of the present invention.
  • the controller 20 comprises two distinct control loops.
  • the controller 20 calculates a stator terminal voltage error signal V serr equal to the difference between the magnitude of the stator terminal voltage V 8 and a predetermined stator terminal voltage reference signal V sre f at a first summing junction 22.
  • the stator terminal voltage error signal V serr is processed by a first compensator 23.
  • the first compensator 23 comprises a proportional plus integral controller and a phase compensation element.
  • the phase compensation is in order to ensure suitable margins of loop stability.
  • the output is a rotor flux vector magnitude reference value ⁇ rmagref-
  • the controller calculates a power supply error signal P eerr equal to the difference between the power supply P e and a predetermined power supply reference signal P eref at a second summing junction 26.
  • the power supply error signal P eer r is processed by a second compensator 27.
  • the second compensator 27 comprises a proportional plus integral controller and a phase compensation element.
  • the phase compensation is in order to ensure suitable margins of loop stability.
  • the output is a rotor flux vector angular position reference value ⁇ rangref, relative to the stator flux vector ⁇ g.
  • the magnitude and angular position reference values of the rotor flux vector, ⁇ rmagref and ⁇ rangre f t are passed to a sub-controller 29.
  • Sub-controller 29 compares the reference values and actual values of the magnitude and angular position of the rotor flux vector, ⁇ r mag and ⁇ ran g-
  • the resultant error signals are passed through appropriate control elements to derive a control signal equal to the desired rotor voltage vector Vrdem-
  • the desired rotor voltage vector Vrd em can be passed to the second converter 13 in either polar coordinate or rectangular coordinate form in order for the converter to generate the rotor voltage vector to supply to the three phase winding 4 on the rotor 3.
  • the actual value of the rotor flux vector ⁇ r can be obtained from measured values of the stator current Ij 8 and the rotor current Ij r together with known quantities for the rotor self inductance L n - and the mutual inductance between the rotor and the stator L m as follows:
  • Sub-controller 29 can take one of two forms illustrated respectively in Figures 5 and 6. Referring to Figure 5 sub-controller 29 comprises two control loops 40 and 41. In control loop 40, sub-controller 29 calculates a rotor flux vector magnitude error signal ⁇ rma g e ⁇ - from the difference between the actual value of the magnitude of the rotor flux vector ⁇ rma g and the rotor flux vector magnitude reference value ⁇ rma gref-
  • the rotor flux vector magnitude error signal ⁇ rmag e rr is processed by a proportional plus integral controller 42 and a compensator 43 to ensure adequate margins of loop stability and an output value limiter 47 to produce the desired magnitude of the rotor voltage vector Vjmagdem-
  • sub-controller 29 calculates a rotor flux vector angular position error signal ⁇ ran g err from the difference between the actual value of the angular position of the rotor flux vector ⁇ ran g and the desired value of the rotor flux vector angular position reference value ⁇ r a ngr ef -
  • the rotor flux vector angular position error signal ⁇ ran gerr is processed by a proportional plus integral controller 44 and a compensator 45 to ensure adequate margins of loop stability and an output value limiter 48 to produce the desired angular position of the rotor voltage vector Vrang d em-
  • the desired rotor voltage vector V 1 - can be defined in terms of polar coordinates Vrmagdem an ⁇ Yrangdem or in terms of rectangular coordinates Vrddem and Vrqdem by passing the coordinates Yrmagdem an( ⁇ Vrangdem through a polar to rectangular coordinate converter 46.
  • Figure 6 illustrates an alternative form of the sub controller 29.
  • the rotor flux vector reference value ⁇ r is firstly converted from polar coordinates to rectangular coordinates by polar to rectangular coordinate converter 50. These rectangular coordinates are then compared with the actual values of the rotor flux vector ⁇ r to calculate a rotor flux vector error signal ⁇ r err in rectangular coordinate form.
  • the transient performance of synchronous generators on the network is also improved over that experienced by a network comprising only synchronous generators.
  • the DFIG controller provides a more stable and better damped dynamic performance than that achieved by a conventional synchronous generator with AVR control.
  • Such a controlled DFIG is also capable of withstanding longer duration faults than is the case with synchronous generators, before full loss of synchronisation with the network is lost.
  • FIG. 7 this illustrates a controller 60 for a DFIG in accordance with a further embodiment of the present invention.
  • the basic controller as illustrated in Figure 4 is enhanced by one or more optional auxiliary controllers 61, 62, 63.
  • Each of the auxiliary controllers generates an auxiliary control signal U auxl , U auX2 , U aU ⁇ 3 -
  • the auxiliary control signals are combined at summing junction 64.
  • the auxiliary control signals are used to modify a signal indicative of the desired angular position of the rotor flux vector relative to the stator flux vector. In Figure 7 this is achieved by adding the combined auxiliary control signals to the rotor flux vector angular position reference value ⁇ rangref at summing junction 65.
  • auxiliary controllers allow the rotor flux vector angular position reference value ⁇ r a ngre f to be manipulated, and thus allows additional control over the actual position of the rotor flux vector angular position ⁇ j an g- In this manner, and dependent upon the construction of each auxiliary controller and how they are used in combination, the dynamic response of the DFIG can be modified.
  • the synchronising power characteristics of a synchronous generator can be emulated. Additionally, the DFIG can make a contribution to network damping and a contribution to frequency regulation in the event of a loss of power generation on the network.
  • Each one of the auxiliary controllers 61, 62, 63 provides a auxiliary control signal U auxl , U auX 2, U auX3 in response to at least one of a rotor speed signal co r , a slip signal s, the stator frequency ⁇ s and the power supply P e .
  • First auxiliary controller 1 allows the DFIG to emulate the synchronising power (or torque) characteristics of a synchronous generator.
  • First auxiliary controller 61 generates a "pseudo rotor angle" signal U auxl by integrating over time the rotor speed variation of the DFIG. This can be used to adjust the rotor flux vector angular position reference value ⁇ rangref- Manipulation of the actual rotor flux vector angular position ⁇ ran g produces variations in the stator power P e and torque T e , which result in the stator power P e and torque T e oscillations equivalent to those of a synchronous generator during a network transient condition.
  • One method of generating the "pseudo rotor angle" signal U auxl as shown in Figure 8 is by passing either the rotor speed ⁇ r or slip s signal through a washout filter 70 to remove any steady state component. The signal output from the washout filter is then integrated over time by integrator 71 and compensated in compensator 72.
  • the term "compensator” used herein is to be interpreted broadly as comprising phase and / or amplitude compensation. If a compensator is arranged to provide only phase compensation, an amplifier may also be provided.
  • Compensator 72 provides the "pseudo rotor angle" signal at an appropriate magnitude, lagging the rotor speed variations by substantially 90° at the system oscillation frequency.
  • the "pseudo rotor angle” signal is then passed through an output value limiter 73. The output limiter ensures that the value of the first auxiliary control signal does not go beyond predetermined threshold values.
  • the provision of a synchronous generator like dynamic response helps to minimise the change produced in the network operating conditions as networks change from purely synchronous generators to a mix of generator types. This is of increasing importance as the proportion of electricity generated from wind farms increases.
  • the first auxiliary controller in combination with the basic controller does not on its own offer any improvement to the dynamic response of the network as a whole.
  • Figure 9 illustrates the arrangement of the second auxiliary controller 62. This allows a controller for a DFIG to contribute to the damping of the power network.
  • the angular position of the rotor flux vector ⁇ ran g can be manipulated in such a way that damping torques are induced in of the synchronous generators on the network. Therefore, a significant contribution to system damping can be provided.
  • the variation in the rotor flux vector angular position reference value ⁇ ra n g re f is given by U aux2 .
  • the second auxiliary control signal U aux2 can be calculated by passing the appropriate network variable through a washout filter 80, to remove any steady state contribution and prevent the second auxiliary controller from operating during steady state conditions.
  • the signal is then passed through a compensator 81 to provide the necessary phase shift and an amplifier 82 to provide the necessary gain.
  • the compensator and the amplifier provide variations in the demanded angular position of the rotor flux vector of sufficient magnitude and appropriate phase with respect to the network oscillations that increased damping torques are induced in the synchronous generators on the network.
  • the signal is passed through an output value limiter 83 to provide the second auxiliary control signal U auX 2-
  • the second auxiliary controller 62 when based on rotor speed ⁇ r , slip speed s or stator electrical power supply P e , can be used to provide improved system damping either independently or in combination with either the first or the third auxiliary controllers. Simulation results indicate that a network incorporating at least one DFIG controlled by a controller including a second auxiliary controller has an appreciable improvement in the damping of the synchronous generators on the network, compared with a network comprising synchronous generators alone. Additionally, the performance of the second auxiliary controller, when based on rotor speed ⁇ r , slip speed s or stator electrical power supply P e , continues to provide significant improvements in network damping when operated in combination with the first auxiliary controller.
  • Network frequency is fixed by the synchronous generators on the network.
  • the generators allocated for frequency regulation that remain connected then need to increase power output as rapidly as possible, to avoid the network frequency falling below the level that demands load disconnection.
  • a DFIG Although the input power of the wind turbine cannot be increased on demand, the asynchronous operation of a DFIG enables the stored mechanical energy of the rotor shaft system to be tapped to provide a rapid increase in generated power over the critical first few seconds following loss of network generation.
  • the rotor shaft system comprises the turbine and the generator rotors together with the connecting gear box. The kinetic energy these hold can be rapidly converted to electrical energy to provide a temporary boost in the power supply P e , at the expense of slowing the rotational speed of the rotor shaft system.
  • the third auxiliary controller 63 comprises an inner control loop 90, which serves to drive down the rotor speed over the initial period following loss of power generation, so that stored energy is released, and output power temporarily increased.
  • the stator frequency ⁇ s (which is equal to and set by the network frequency) is processed to provide a rotor speed reference point ⁇ n - ef -
  • the stator frequency signal ⁇ s is passed through a washout filter 91 to eliminate any steady state contribution and then through a first compensator 92, an output value limiter 93 and a second compensator 94 to provide the required transient profile for the rotor speed reference set point oo r ref.
  • a measure of the rotational speed of the rotor shaft system is passed through a washout filter 95 to remove any steady state condition. The measure may be based on the rotor speed ⁇ r or the slip signal s.
  • the signal is then compared with the rotor speed reference point O r re f at summing junction 96 to provide an auxiliary error signal.
  • the auxiliary error signal is passed through a compensator 97 that offers the facility for adjusting the loop stability margins, to provide the third auxiliary control signal U auX3 .
  • Compensator 97 is arranged to provide lead lag compensation.
  • the effect of the third auxiliary control signal U auX3 is to increase the rotor flux vector angular position reference value ⁇ r a ngref- This produces an increase in generator torque and a consequent reduction in rotor speed ⁇ r .
  • the rotor speed is driven down to follow the transient swing in the derived rotor speed reference set point corre f -
  • the rotor speed ⁇ r returns to the original value when the network has returned to a steady state condition.
  • the third auxiliary controller 63 may be operated on its own or with the second auxiliary controller 62. However, the effect of driving down the rotor speed causes the first auxiliary controller 61 to have a negative effect. Therefore, if the third auxiliary controller 63 is used in combination with the first auxiliary controller 61, then when a loss of network generation is detected the first auxiliary controller is preferably temporarily inhibited or disconnected.
  • the auxiliary control signals U aU ⁇ l5 U auX2 , U auX3 are shown being added to the rotor flux vector angular position reference value ⁇ ran g ref in order to modify the signal indicative of the desired angular position of the rotor flux vector relative to the stator flux vector.
  • the auxiliary control signals may be added to the power supply reference P ere f either individually or in combination at summing junction 26 as illustrated in Figure 11. Whether added individually or in combination the auxiliary control signals indirectly modify the signal indicative of the desired angular position of the rotor flux vector relative to the stator flux vector.
  • Figure 11 illustrates another embodiment of the present invention. Components in Figure 7 that are similar to components in Figure 7 are referred to using the same reference number.
  • the auxiliary controllers 61, 62, 63 effectively manipulate the power supply reference value P eref , and therefore indirectly the value of the signal indicative of the desired angular position of the rotor flux vector ⁇ ran gre f -
  • the arrangement of the auxiliary controllers remains the same as before, with gain and phase shift requirements altered to suit the new arrangement of the controller 101.
  • auxiliary control loops can be used to modify the power supply reference value Peref in general for any DFIG control scheme employing a power (or torque) feed back loop.
  • Such auxiliary control loops can provide similar benefits in terms of a synchronising power characteristic, network damping and network frequency regulation to a generic DFIG controller, as provided to the controller illustrated in Figure 11. This additional embodiment of the present invention is illustrated in Figure 12.
  • Controller 110 has a power supply feedback loop and may optionally have one or more feedback loops monitoring other parameters of the DFIG' s operation, as shown by the variable A feedback loop.
  • the variable A feedback loop comprises an input measured value of parameter A derived from sensors connected to the DFIG and an input reference value for parameter A.
  • An error signal A err is calculated. This error signal A e ⁇ is used as an input to the controller.
  • Sub-controller 111 converts the measured error signals to the desired rotor voltage vector Vj dem -
  • auxiliary control signals U auxl , U aux2 , U auX3 can be used to modify the signal indicative of the desired angular position of the rotor flux vector relative to the stator flux vector by modifying the desired angular position of the rotor voltage vector V ra ngdem.
  • One example of this implementation is illustrated in Figure 13, where only the second auxiliary control signal U auX2 is shown being added to the desired angular position of the rotor voltage vector V ran g dem at summing junction 121. It will be appreciated that all three auxiliary control signals can be added to the desired angular position of the rotor voltage vector Vrangd em at summing junction 121.
  • auxiliary controllers 61, 62, 63 When used to modify the desired angular position of the rotor voltage vector Y ran g de m the auxiliary controllers 61, 62, 63 effectively manipulate the value of the signal indicative of the desired angular position of the rotor flux vector ⁇ ran gref.
  • the auxiliary controllers remain the same as in Figures 8, 9 and 10, with gain and phase shift requirements altered to suit the new arrangement of the controller 120.
  • the second auxiliary controller 62 which corresponds to a power system stabiliser, is preferably applied to the desired angular position of the rotor voltage vector Vrangdem- In order to provide rapid and effective damping, the second auxiliary controller is preferably able to modify the signal indicative of the desired angular position of the rotor flux vector ⁇ r a ngref as directly as possible.
  • the first auxiliary controller 61 is preferably disabled in order to avoid detrimental interaction.
  • the auxiliary control loops can be used to modify the desired angular position of the rotor voltage vector Y ran g dem for any DFIG control scheme employing a power (or torque) feed back loop.
  • the auxiliary control loops may provide similar benefits as provided to the controller of Figure 13 in terms of a synchronising power characteristic, network damping and network frequency regulation to a generic DFIG controller.
  • This additional embodiment of the present invention is illustrated in Figure 14, which shows the second auxiliary control signal U aU ⁇ 2 being applied to the desired angular position of the rotor voltage vector Yrangdem at a summing junction 131.
  • the other two auxiliary control signals are arranged to alter to power supply reference value P ere f.
  • Controller 130 has a power supply feedback loop. Controller 130 may optionally have one or more feedback loops monitoring other parameters of the DFIG' s operation, as shown by the variable A feedback loop, as described above in relation to Figure 12. Similar components in Figures 12 and 14 are referred to by the same reference numbers.
  • Sub-controller 132 converts the measured error signals to the desired rotor voltage vector V rdem -
  • the auxiliary control signals can be applied to alter desired angular position of the rotor voltage vector V ran g dem for any DFIG controller, which is arranged to provide a control signal comprising the rotor voltage vector Vj dem -
  • the auxiliary controllers provide similar benefits in terms of a synchronising power characteristic, network damping and network frequency regulation to any generic DFIG controller.
  • An example of such an additional embodiment of the present invention is illustrated in Figure 15.
  • Controller 140 has two feedback loops monitoring parameters of the DFIG's operation, depicted as the variable A feedback loop and the variable B feedback loop. Each feedback loop shown has as an input a reference value A ref and B ref respectively. These reference values are supplied to the controller along with measured values of the variables A and B. The measured values and the reference values are used in the respective feedback loops to generate error signals A s ⁇ and B err - Variables A and B may be any measured or calculated parameter relating to the DFIG. Similar components in Figures 12 and 15 are referred to by the same reference numbers.
  • Sub- controller 141 converts the measured error signals to the desired rotor voltage vector Y rdem - Figure 15 shows all three auxiliary control signals being applied to the desired angular position of the rotor voltage vector V ran g de m at summing junction 142.
  • the second auxiliary control input U 311X2 is used in order to provide more effective damping to the network. Applying any of the auxiliary control signals to the desired rotor voltage vector Vj dem can improve overall dynamic performance.
  • auxiliary control inputs U auxl , U auX 2, U auX 3 can be used to modify the performance of the DFIG by adding them into the controller at different points and in different combinations.
  • the auxiliary control inputs U auxl , U aux2 , U aux3 may be added to any one or more of the rotor flux vector angular position reference value ⁇ rangrefi the power supply reference value P ere f and the desired angular position of the rotor voltage vector Vrangdem- I n eacn case > one > two or three auxiliary control inputs may be added to the controller at each point.
  • the three auxiliary controllers 61, 62, 63 need not all be present for all DFIG controllers. Indeed, for many applications only the second auxiliary controller 62 is likely to be used to modify the desired angular position of the rotor voltage vector Vr an gd em to provide a power system stabiliser capability for any generic DFIG controller.
  • Air gap power is given as:
  • Stator power differs from the air gap power only by the resistance losses of the stator. As stator power is more readily determined from the available voltage and current measurements this is the preferred choice. Stator power is given by:
  • the controller described herein can be viewed in terms of manipulating the rotor flux vector ⁇ ,- or the internally generated voltage Ej g as these terms are directly related.
  • the controller may be implemented in hardware. Alternatively the controller may be implemented in software.
  • auxiliary controllers may be implemented within any DFIG controller in any combination.

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Abstract

L'invention concerne un contrôleur pour un générateur asynchrone à alimentation double. Le générateur asynchrone à alimentation double comprend un stator et un rotor. Le stator comprend des bornes de stator agencées pour fournir une tension de borne de stator triphasée, et un bobinage triphasé agencé pour fournir un flux de stator décrit par un vecteur en rotation à une fréquence de stator. Le stator fournit une alimentation électrique de stator à la fréquence de stator. Le rotor comprend un bobinage triphasé agencé pour fournir un flux de rotor décrit par un vecteur tournant sensiblement à la fréquence du stator, à une certaine position angulaire par rapport au vecteur de flux de stator. Le contrôleur de l'invention est agencé pour déterminer un signal de contrôle pour provoquer un changement sensiblement seulement sur la magnitude du vecteur de flux de rotor, en réaction à un signal d'erreur de tension de borne de stator. Le contrôleur est également agencé pour déterminer un signal de contrôle pour provoquer un changement sensiblement uniquement dans la position angulaire du vecteur de flux de rotor par rapport au vecteur de flux de stator, en réaction à un signal d'erreur d'alimentation électrique du stator.
PCT/GB2005/003471 2004-09-14 2005-09-09 Controle d'un generateur asynchrone a alimentation double WO2006030183A1 (fr)

Applications Claiming Priority (4)

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GB0420416.0 2004-09-14
GB0420416A GB0420416D0 (en) 2004-09-14 2004-09-14 Control of a doubly-fed induction generation
GB0508618.6 2005-04-28
GB0508618A GB0508618D0 (en) 2005-04-28 2005-04-28 Control of a doubly-fed induction generator

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WO2006091497A3 (fr) * 2005-02-22 2007-04-12 Xantrex Technology Inc Procede et appareil de conversion de l'electricite eolienne en electricite a frequence constante destinee a un reseau general
US7215035B2 (en) * 2005-02-22 2007-05-08 Xantrex Technology, Inc. Method and apparatus for converting wind generated electricity to constant frequency electricity for a utility grid
DE102007014728A1 (de) 2007-03-24 2008-10-02 Woodward Seg Gmbh & Co. Kg Verfahren und Vorrichtung zum Betrieb einer doppeltgespeisten Asynchronmaschine bei transienten Netzspannungsänderungen
US8264209B2 (en) 2007-03-24 2012-09-11 Woodward Kempen Gmbh Method of and apparatus for operating a double-fed asynchronous machine in the event of transient mains voltage changes
US7800243B2 (en) 2007-04-30 2010-09-21 Vestas Wind Systems A/S Variable speed wind turbine with doubly-fed induction generator compensated for varying rotor speed
ES2386436A1 (es) * 2009-01-21 2012-08-21 Mondragon Goi Eskola Politeknikoa Metodo de control para una instalacion eolica de generacion electrica
US8219256B2 (en) 2009-07-14 2012-07-10 Siemens Aktiengesellschaft Bang-bang controller and control method for variable speed wind turbines during abnormal frequency conditions
WO2011008637A3 (fr) * 2009-07-14 2011-05-12 Siemens Energy, Inc. Contrôleur par tout ou rien et procédé de commande pour turbines éoliennes à vitesse variable dans des conditions de fréquences anormales
KR101447470B1 (ko) * 2009-07-14 2014-10-06 지멘스 악티엔게젤샤프트 비정상 주파수 조건에서 변속 풍력 터빈을 위한 뱅뱅 제어기 및 제어 방법
CN102868353A (zh) * 2011-07-08 2013-01-09 Abb公司 用于双馈感应机器的控制系统
EP2544358A1 (fr) * 2011-07-08 2013-01-09 ABB Oy Système de commande de machine à induction à double alimentation
US20130009610A1 (en) * 2011-07-08 2013-01-10 Abb Oy Control system for doubly-fed induction machine
CN105221353A (zh) * 2015-11-10 2016-01-06 华北电力大学（保定） 双馈风力发电机组的叶轮气动不对称故障的诊断方法
CN108799011A (zh) * 2017-04-28 2018-11-13 北京金风科创风电设备有限公司 对风电机组的叶片进行监测的设备和方法
CN108799011B (zh) * 2017-04-28 2020-01-31 北京金风科创风电设备有限公司 对风电机组的叶片进行监测的设备和方法

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