CN114172213A - Power control method of brushless double-fed motor - Google Patents

Power control method of brushless double-fed motor Download PDF

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CN114172213A
CN114172213A CN202111403263.3A CN202111403263A CN114172213A CN 114172213 A CN114172213 A CN 114172213A CN 202111403263 A CN202111403263 A CN 202111403263A CN 114172213 A CN114172213 A CN 114172213A
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winding
power
control
current
angle
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CN114172213B (en
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张德斌
马季军
吉裕晖
屈诚志
王胜佳
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Shanghai Institute of Space Power Sources
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
    • H02J3/48—Controlling the sharing of the in-phase component
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/381—Dispersed generators
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/388—Islanding, i.e. disconnection of local power supply from the network
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
    • H02J3/50—Controlling the sharing of the out-of-phase component
    • 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
    • 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
    • H02P9/008—Arrangements for controlling electric generators for the purpose of obtaining a desired output wherein the generator is controlled by the requirements of the prime mover
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
    • H02J2300/20—The dispersed energy generation being of renewable origin
    • H02J2300/28—The renewable source being wind energy
    • 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

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Control Of Ac Motors In General (AREA)
  • Control Of Motors That Do Not Use Commutators (AREA)

Abstract

The invention discloses a power control method of a brushless double-fed motor, which adopts the same directional control strategy under the working condition of independent operation/grid-connected operation of a system, simplifies a control program and ensures a unified control framework of a power generation system. The method is based on a control winding current fixed-down control strategy, and is used for expanding a control winding conversion angle into a new control degree of freedom for adding the new control degree of freedom, specifically analyzing that the control winding amplitude is used for controlling the active power of a system, and the angle control system outputs reactive power, so that the active power and the reactive power of the system are effectively controlled. A new control scheme is provided for the grid-connected control system, the control complexity of the system is simplified, and the safety and the stability of the system are improved.

Description

Power control method of brushless double-fed motor
Technical Field
The invention relates to the technical field of motor control, in particular to a power control method of a brushless double-fed motor.
Background
A brushless doubly-fed motor (BDFM) can realize variable-speed constant-frequency power generation only by rotating difference times of power capacity of a required frequency converter, and meanwhile, an electric brush and a slip ring are eliminated by adopting a special structural design, so that the operation reliability of the motor is improved, the maintenance and operation cost is reduced, and the BDFM has a wide application prospect in a power generation system.
In power generation applications, particularly in micro-grid applications such as wind power generation and ship shaft power generation, in order to improve power supply reliability, uninterrupted power supply to critical loads needs to be ensured, and a brushless double-fed motor simultaneously has the capabilities of carrying loads independently, carrying loads together with a power grid, and transferring loads to the power grid, so that a power generation system with independent/grid-connected dual-mode operation capability currently becomes a research hotspot. In the dual-mode power generation system, the control targets of independent and grid-connected operation are generally the amplitude and frequency of output voltage and active and reactive power respectively, so that different control systems are adopted under two working conditions according to different control targets.
The control target of the independent operation control system is output voltage amplitude and frequency, the existing literature researches a brushless double-fed independent operation power generation system, and a document [7] adopts a single-loop vector control idea and respectively realizes the control of a dq component of a power winding by using a dq axis component of a control winding voltage; document [8] adopts a double-loop control system, and the system realizes the stable operation of a brushless double-fed independent power generation system; the double-ring control system becomes a mainstream control scheme because of the advantages of strong non-ideal load capacity, easy realization of output current-limiting protection, rapid dynamic response and the like [9-10 ]. Different orientation modes of a double-ring control system often determine the control difficulty of the system, wherein documents [11-12] adopt a control winding current orientation scheme, the orientation scheme is implemented at a control winding side, electric quantity information at a power winding side is not required to be acquired, a measurement structure of the control system is simplified, meanwhile, the running state of the system is not influenced by load impact, the current-limiting control is facilitated, the safety of the system is greatly guaranteed, and the like, and the control scheme becomes a better alternative control scheme.
The control target of the grid-connected operation control system is to output active power and reactive power, and documents are provided for a brushless double-fed grid-connected control system. The main control methods comprise scalar control [13], direct torque control [14-15], direct power control [16], vector control [17-22], variable structure control [23] and other intelligent control [24-26], wherein the vector control is most widely applied due to the advantages of simple control, rapid dynamic response, high stability and the like.
Vector control is divided into different orientation modes, and document [22] adopts a rotor flux linkage orientation mode to realize control of a brushless double-fed motor, but the electric quantity value of a rotor winding is difficult to measure and needs to be obtained by calculating the electric quantities of a control winding and a power winding, so that the realization difficulty is increased; documents [18-20] propose a control strategy for power winding side electric quantity orientation, the control realizes decoupling of output active power and reactive power, and better realizes control of output power, but the orientation is implemented on the power winding side, so that current-limiting control is inconvenient to be performed on a control winding, and meanwhile, the stability of coping with grid faults is poor.
In order to avoid the problem that the system control algorithm is complex due to the switching of the system directional control strategy when the independent operation mode and the grid-connected operation mode are switched, and simultaneously, the unique advantage of controlling the winding current direction under the independent operation mode is used, the invention provides the brushless double-fed grid-connected system to control the winding current directional control strategy to finish the unification of the independent operation and the grid-connected operation control framework, and simultaneously, the protection of the whole system can be better finished when the low-voltage ride-through electric network has faults after the control side is connected to the grid, so that the safety of the system is greatly enhanced, and the requirements of the power generation system under the independent and grid-connected modes are met.
Disclosure of Invention
The invention aims to provide a power control method of a brushless doubly-fed motor, and aims to solve the problems that control complexity is increased and impact is caused at the moment of grid connection due to directional control algorithm switching when working conditions of an independent/grid-connected dual-mode operation system are switched.
In order to solve the technical problems, the technical scheme of the invention is as follows: the power control method of the brushless doubly-fed motor is provided, and comprises the following steps:
s1, detecting the three-phase current of the control winding and carrying out abc/dq coordinate transformation on the three-phase current to obtain a d-axis component i of the control winding currentcdAnd q-axis component icq；
Detecting three-phase current of the power winding and carrying out abc/dq coordinate transformation on the three-phase current to obtain a d-axis component i of the power winding currentpdAnd q-axis component ipq；
Detecting three-phase line voltage of the power winding, converting the three-phase line voltage into phase voltage, and performing abc/dq coordinate transformation on the phase voltage to obtain a d-axis component u of the power winding voltagepdAnd q-axis component upq；
S2, winding the power current d-axis component ipdAnd q-axis component ipqAnd d-axis component u of power winding voltagepdAnd q-axis component upqCurrent orientation i converted to control winding by motor internal relationcqObtaining d-axis component of power winding voltage under control winding coordinate system under 0
Figure BDA0003371831940000031
Component of q axis
Figure BDA0003371831940000032
And d-axis component i of power winding currentd pQ-axis component
Figure BDA0003371831940000033
S3, calculating the power of the grid-connected system based on the equivalent circuit of the brushless double-fed motor, and controlling the voltage of the power winding under the winding coordinate system after S2 transformation
Figure BDA0003371831940000034
And power winding current id p、
Figure BDA0003371831940000035
Calculating to obtain output active power PsReactive power QsThe expression of (1);
s4, converting the output work obtained in S3 through the internal relation of the brushless doubly-fed motorRate Ps、QsThe expression is converted into a control winding current vector icFlux linkage vector Ψ with the power windingpForms thereof;
s5, based on the control winding current orientation, applying a small signal mode to specifically solve the relation delta I between the active power variation delta P and the control winding current amplitude variationcThe current is used as the d-axis input of the current inner ring;
at the same time, the relation delta theta between the active power variation delta Q and the control winding current angle variation is solvedcTaking the control winding angle transformation increment value as a control winding angle transformation increment value;
s6, obtaining the power control relation under the orientation of the brushless dual-feeder control winding current through the steps S1-S6, and controlling the winding current amplitude IcUsed for controlling the system to output active power and change the angle thetacUsed for controlling the system to output reactive power.
Further, the step S2 includes:
s2-1, mounting code disc on the rotor to obtain mechanical angular speed omega of the motor rotorm；
S2-2, according to the pole pair number p of the power windingpControl the number p of pole pairs of the windingcAngular frequency omega of the current of the power windingpAnd rotor mechanical angular velocity omegamObtaining the angular frequency omega of the control winding currentc：
S2-3, controlling the angular frequency omega of the winding currentcThe current angle of the control winding is obtained by an input integration link and is converted to the angle theta required by a unified reference dq coordinate systemc；
S2-4, detecting and controlling three-phase current i of windingca、icb、iccAnd by thetacAs a coordinate transformation angle, converting the control winding current from a static abc coordinate to a unified reference dq coordinate system through Park coordinate transformation to obtain a d-axis component i of the control winding currentcdAnd q-axis component icq：
S2-5, controlling the winding coordinate transformation angle theta according to the step S2-3cRotor position angle thetarObtaining a transformation of the power winding current from a stationary abc coordinateTransformation angle theta for transformation to a unified reference dq coordinate systemp；
S2-6, detecting three-phase current i of power windingpa、ipb、ipcAnd by thetapAs a coordinate transformation angle, converting the power winding current from a static abc coordinate to a unified reference dq coordinate system through Park coordinate transformation to obtain a power winding current d-axis component ipdAnd q-axis component ipq：
S2-7, detecting the voltage u of the three-phase line of the power windingpab、upbc、upcaConverted into phase voltage upa、upb、upcAnd is given by thetapAs a coordinate transformation angle, converting the power winding current from a static ABC coordinate to a unified reference dq coordinate system through Park coordinate transformation to obtain a power winding voltage d-axis component updAnd q-axis component upq；
S2-8, converting the power winding current i in the steps S2-6 and S2-7pd、ipqVoltage upd、upqThe components of the current are respectively converted into a control winding current directional coordinate system through the relation of an internal model of the motor
Figure BDA0003371831940000051
Further, the step S3 includes:
s3-1, representing the power winding voltage as a power winding flux linkage and a control winding current form according to a motor model:
Figure BDA0003371831940000052
therein, Ψc p、uc p、ic cRespectively controlling the current orientation lower power winding voltage flux linkage vector, the voltage vector and the control winding current amplitude; r isp、rrImpedance of power winding and rotor winding, Lsp、LrThe self inductive reactance of the power winding and the rotor winding are respectively; mpr、McrAre power windings andthe mutual inductance between the rotor winding, the control winding voltage and the rotor winding; omegap、ωsrRespectively carrying out power winding angular frequency and slip frequency; s is a differential operator; j is a complex operator;
s3-2, similarly, representing the power winding current as a power winding flux linkage and control winding current form according to the motor model:
Figure BDA0003371831940000053
wherein the parameters are in accordance with step S3-1;
s3-3, obtaining a system power expression by the power winding voltage and the power winding current obtained in the steps S3-1 and S3-2:
Figure BDA0003371831940000054
where S is the apparent power, Ps、QsRespectively representing active power and reactive power of the system;
s3-4, controlling the current orientation of the winding, and controlling the active power P of the system based on the phase angle control thoughtsReactive power QsExpressed as:
Figure BDA0003371831940000061
Figure BDA0003371831940000062
where | Ψc p|、|Ic cI respectively represents the flux linkage amplitude of the power winding and the current amplitude of the control winding; theta is the included angle between the flux linkage of the power winding and the current of the control winding in the current coordinate system of the control winding.
Further, the step S4 includes:
s4-1, active power variation delta PsAnd reactive power variation Δ QsRespectively as follows:
Figure BDA0003371831940000063
wherein Ic c_iniFor controlling the initial value of the amplitude of the winding current, Ic'c_finIn order to control the final value of the winding current, delta theta is the angle variation of the control winding, and other parameters are consistent with those in the step S3-2;
s4-2, current amplitude I relative to control windingcWhen the angle change is small, it can be considered that:
cosΔθ≈1,sinΔθ≈Δθ；
s4-3, the power change expression in S4-1 is finished according to the steps, and finally the expression can be expressed as follows:
Figure BDA0003371831940000064
wherein Δ Ic c_ampTo control the amount of change, Δ I, due to the magnitude of the winding currentc c_angCausing a variation in order to control the winding angle.
Further, the step S5 includes:
s5-1, according to the analysis of the system active power control in the step S4, the control equation is obtained as follows:
Figure BDA0003371831940000065
wherein
Figure BDA0003371831940000066
The active power of the system can be controlled according to the relational expression;
s5-2, marking the variation of the control winding caused by the variation of the active power in the step S5-1 as delta Ic1；
S5-3, analyzing the reactive power control of the system by using a small signal analysis tool to obtain a specific control equation as follows:
Figure BDA0003371831940000071
wherein QsThe given value of the reactive power can realize the control of the reactive power of the system according to the relational expression;
s5-4, recording the angle variation of the control winding obtained by the reactive power variation in the step S5-3 as: delta thetac1。
Further, the step S6 includes:
s6-1, designing a power outer ring controller according to the step S5, and setting a proportional coefficient K of an outer ring d-axis PI controllerPqAnd integral coefficient KIqValue K ofPq＝KPd KIq＝KIdWhere the proportionality coefficient K of the d-axis PI controllerPdAnd integral coefficient KIdObtaining according to experience;
s6-2, converting the active power outer loop reference value Ps *And the actual value PsDifference (P) ofs *-Ps) Input to PI controller to obtain output of Δ Ic2；
S6-3, obtaining the control winding current amplitude variation delta I obtained in the step S5-2c1And step S6-2, obtaining the output quantity Delta I of the current amplitude of the control windingc2Adding to obtain d-axis given value i of inner ring of current of control windingc d*；
S6-4, carrying out outer loop reference value on reactive power
Figure BDA0003371831940000073
And the actual value QsDifference of (2)
Figure BDA0003371831940000072
The input PI controller obtains its output as delta thetac2；
S6-5, controlling the winding angle variation delta theta obtained in the step S5-4c1And the control winding angle output quantity delta theta obtained in the step S6-4c2The total variation of the control winding angle obtained by adding is as follows: delta thetac；
S6-6, changing the angle delta theta obtained in the step S6-5cSuperimposed on the control winding for varying the angle thetacThe transformation angle reference value is obtained as:
Figure BDA0003371831940000081
further, the step S7 includes:
s7-1, obtaining an inner ring expression by a motor mathematical model as follows:
Figure BDA0003371831940000082
wherein
Figure BDA0003371831940000083
S7-2, multiplying the electric quantity obtained in the step S2 by the motor parameter to obtain the compensation quantity;
and S7-3, superposing the obtained d-axis q-axis compensation quantity to the current inner loop output, so that the feedforward compensation is completed, and the influence speed of the system is improved.
Further, the step S8 includes:
s8-1, setting q-axis PI controller proportionality coefficient KpqAnd integral coefficient KiqValue K ofpq＝Kpd Kiq＝KidWhere the proportionality coefficient K of the d-axis PI controllerpdAnd integral coefficient KidObtaining according to experience;
s8-2, controlling the d-axis reference value of the winding current
Figure BDA0003371831940000084
And d component
Figure BDA0003371831940000085
Difference of (2)
Figure BDA0003371831940000086
Inputting d-axis PI controller to obtain output of d-axis controllerOut of PId(ii) a Will control the q-axis reference value of the winding current
Figure BDA0003371831940000087
And q-axis component
Figure BDA0003371831940000088
Difference of (2)
Figure BDA0003371831940000089
Obtaining an output PI of a q-axis controller by an input q-axis PI controllerq；
S8-3, obtaining a system current inner ring specific expression according to the internal dq mathematical model of the brushless doubly-fed motor:
Figure BDA0003371831940000091
wherein R issc、LscSingle-phase resistance, inductance, K, of the control winding of the brushless dual-feed machine1、K2And K3Equivalent parameters obtained after series connection and parallel connection of the motor inductors are respectively obtained;
s8-4, controlling the winding current angle theta in the step S6-6* cWill be provided with
Figure BDA0003371831940000092
Obtaining a three-phase reference value u of the control winding voltage after Park inverse transformationca *、ucb *、ucc *And sending the signal to a pulse width modulation module to obtain a switch driving signal of a machine side converter, and driving the converter by using the signal to output a corresponding control winding three-phase voltage uca、ucb、uccAnd the closed-loop control of the control winding current of the brushless dual-feeder is realized.
Further, three-phase reference value u of control winding voltageca *、ucb *、ucc *Comprises the following steps:
Figure BDA0003371831940000093
wherein the content of the first and second substances,
Figure BDA0003371831940000094
the d-axis component and the q-axis component, θ x, of the control winding voltage obtained in step S8cThe control winding angle obtained in step S6.
The power control method of the brushless double-fed motor provided by the invention has the beneficial effects that:
the technical scheme of the invention realizes the grid-connected control of the brushless double-fed motor under the condition of controlling the winding current orientation, completes the grid-connected control under the condition of not changing the orientation mode, and unifies the system control framework. The unified control architecture established by the system simplifies the control difficulty, is oriented to the control side system to facilitate current limiting, has good stability for dealing with the power grid fault, and provides great guarantee for the safety and stability of the whole system
Drawings
The invention is further described with reference to the accompanying drawings:
FIG. 1 is a schematic diagram of the independent/grid-connected operation of a brushless doubly-fed motor;
FIG. 2 is a schematic diagram of obtaining a control winding current dq component in a unified reference dq coordinate system; wherein, (a) is a rotating coordinate system for controlling the winding current dq; (b) three-phase ABC to two-phase dq conversion is performed for controlling winding current;
FIG. 3 is a schematic diagram of obtaining voltage and current dq components of a power winding in a unified reference dq coordinate system; wherein, (a) is a power winding current dq rotation coordinate system; (b) three-phase ABC to two-phase dq conversion is performed on the electric quantity of the power winding;
FIG. 4 is a diagram illustrating the acquisition of correct components of the power winding in the control winding current coordinate system;
FIG. 5 is an equivalent circuit of a brushless doubly-fed motor;
FIG. 6 is a graph of the coordinate relationship of the windings for controlling the orientation of the winding current required by the present invention;
FIG. 7 is a diagram of the active and reactive coordinate transformation relationship;
FIG. 8 is a diagram of reactive power control small signal control relationship;
FIG. 9 is a schematic block diagram of a control winding current closed loop control system required by the present invention;
FIG. 10 is a general diagram of a waveform of a grid-connected control operation experiment;
FIG. 11 is a grid-tied steady state waveform;
FIG. 12 is a system active power jump waveform;
fig. 13 is a system reactive power jump waveform.
Detailed Description
The power control method of the brushless doubly-fed machine according to the present invention is further described in detail with reference to the accompanying drawings and specific embodiments. Advantages and features of the present invention will become apparent from the following description and from the claims. It is to be noted that the drawings are in a very simplified form and are all used in a non-precise ratio for the purpose of facilitating and distinctly aiding in the description of the embodiments of the invention.
The invention provides a set of brushless doubly-fed motor grid-connected control strategy for controlling the grid-connected moment of a winding current orientation, simultaneously meets the requirements of a future wind power system in an independent mode and a grid-connected mode, does not change an orientation scheme under the independent/grid-connected dual-mode operation, and constructs a unified control framework.
In order to meet the independent grid-connected dual-mode operation working condition and establish a unified control framework of a power generation system, the invention provides a control winding current fixed-down grid-connected control method which is simple to realize, has strong control structure universality and is suitable for various load working conditions and industrial application occasions and various brushless double-fed motor types based on the current orientation of a control winding commonly used in the existing brushless double-fed motor independent operation research and fully utilizes the advantage of simplified design of the control winding, and establishes a corresponding grid-connected control system so as to reduce the complexity of a control algorithm and improve the stability of the system.
The grid-connected control method is based on a brushless double-fed motor equivalent circuit model under control winding current orientation, system output active power and reactive power are expressed in the forms of output power winding flux linkage and control winding current amplitude, the relation between the control winding current amplitude and the active power and the relation between a control winding conversion angle and the reactive power are analyzed through a small signal form, the conversion angle is designed into a new control freedom degree according to the mathematical relation to realize the control of the reactive power of the system, and the control winding current q axis completes 'forced orientation', so that the independent/grid-connected control method adopts the same orientation control strategy, the algorithm switching during mode switching is avoided, the control algorithm is greatly simplified, and the system stability is ensured.
The method comprises the following specific steps:
(1) detecting three-phase currents of control windings, e.g. ica、icb、icc. According to the principle shown in FIG. 2, the control winding current is converted from a static three-phase abc coordinate system to a unified reference dq coordinate system to obtain a d-axis component i of the control winding currentcdAnd q-axis component icq；
Detecting three-phase currents of power windings, e.g. ipa、ipb、ipc. According to the principle shown in FIG. 3, the d-axis component i of the power winding current is obtained by converting the power winding current from a static abc coordinate system to a dq coordinate systempdAnd q-axis component ipq；
Sensing three-phase line voltage of power winding, e.g. upab、upbc、upca. According to the principle shown in FIG. 3, the voltage of the power winding wire is converted into phase voltage, and then the phase voltage is converted into a unified reference dq coordinate system from a static abc coordinate system to obtain the d-axis component u of the voltage of the power winding wirepdAnd q-axis component upq；
(2) D-axis component i of power winding currentpdAnd q-axis component ipqAnd d-axis component u of power winding voltagepdAnd q-axis component upqThe electric quantity is converted to the electric quantity under the control winding current directional coordinate system through the electric quantity relation among the motors, as shown in figure 4, respectively
Figure BDA0003371831940000121
(3) Establishing an equivalent circuit diagram of the brushless doubly-fed system, as shown in fig. 5;
(4) calculating the stable power P of the system output according to the steps (2) and (3)sReactive power QsAnd subjecting it toExpressed as control winding current amplitude IcWith power winding linkage ΨpForms thereof;
(5) the active power change rate delta P is analyzed by small signals to obtain the active power change rate delta P and the current change delta I of the control windingcThe relationship between; carrying out small signal analysis on the reactive power change rate delta Q to obtain the reactive power change rate delta Q and the control winding conversion angle delta thetacThe relationship between them, as shown in FIG. 7;
(6) according to the principle shown in FIG. 9, a closed-loop control system for controlling the dq component of the winding current is constructed. Converting the electric quantity of the power side into a control winding coordinate system, and detecting the control winding current i obtained in the step (3)cd、icqWith corresponding closed-loop reference values
Figure BDA0003371831940000122
The error of (2) is inputted to a d-axis proportional-integral controller (PI controller); d. output PI of q-axis PI controllerd，PIqTo obtain the reference value of the dq component of the control winding voltage
Figure BDA0003371831940000123
The reactive power is output delta thetacSuperimposed on the control winding for varying the angle thetacIn the above-mentioned manner,
Figure BDA0003371831940000124
obtaining a three-phase reference value of the control winding voltage through Park inverse transformation
Figure BDA0003371831940000125
Will be provided with
Figure BDA0003371831940000126
Inputting the pulse width modulation module to generate a driving signal of the machine side converter, and driving the machine side converter to generate the required three-phase voltage u of the control windingca、ucb、uccTo control the winding current dq component
Figure BDA0003371831940000127
For closed loop parameterExamination value
Figure BDA0003371831940000128
Closed loop tracking of (1); and meanwhile, the outer ring also adopts a PI controller to finish the quick control of the system.
The power control method can complete the grid-connected control under the current fixed direction of the system control winding, meet the independent/grid-connected unified framework and simplify the control algorithm of the system.
The step (1) comprises the following steps, the principle of which is shown in fig. 2 and 3:
(11) the mechanical angular speed omega of the motor rotor is obtained by mounting a code disc on the rotorm；
(12) The power winding voltage generated by the independent start of the brushless double-fed motor is constant at 50Hz, and the angular frequency omega ispConstant at a constant of 100 π rad/s. According to the operating characteristics of the brushless doubly-fed motor, the number p of pole pairs of the power winding is adjustedpControl the number p of pole pairs of the windingcCurrent angular frequency of 100 pi rad/s of power winding and mechanical angular speed omega of rotormSubstituting formula (8) to obtain the angular frequency omega of the control winding currentc：
ωc＝(pp+pc)Ωm-100π……(1)
(13) Will omegacInputting an integral link to obtain an angle theta required by converting the control winding current to a unified reference dq coordinate systemc；
(14) Detecting three-phase currents of control windings, e.g. ica、icb、icc(ii) a At thetacAs a coordinate transformation angle, converting the control winding current from a static ABC coordinate to a unified reference dq coordinate system through Park coordinate transformation to obtain a control winding current dq component icd、icq：
Figure BDA0003371831940000131
(15) Converting the coordinate of the control winding in the step (23) into an angle thetacRotor position angle thetarSubstitution of equation (3) results in the transformation of the power winding current from the stationary abc coordinate toTransformation angle theta for unified reference dq coordinate systemp：
θp＝(pp+pc)θr-θc……(3)
(16) Detecting three-phase currents of power windings, e.g. ipa、ipb、ipc(ii) a At thetapAs a coordinate transformation angle, converting the power winding current from a static abc coordinate to a unified reference dq coordinate system through Park coordinate transformation to obtain a power winding current dq axis component ipd、ipq：
Figure BDA0003371831940000141
(17) Sensing three-phase line voltage of power winding, e.g. upab、upbc、upcaConvert it into phase voltage upa、upb、upc(ii) a At thetapAs a coordinate transformation angle, converting the power winding current from a static abc coordinate to a unified reference dq coordinate system through Park coordinate transformation to obtain a power winding voltage dq axis component upd、upq：
Figure BDA0003371831940000142
The step (2) comprises the following steps, the principle of which is shown in fig. 4:
(21) by setting the control winding current q-axis
Figure BDA0003371831940000143
Realizing the forced orientation of the control winding current, and determining a reference coordinate system;
(22) sensing three-phase line voltage of power winding, e.g. upab、upbc、upcaConvert it into phase voltage upa、upb、upcTaking the electric quantity of the power winding voltage two-phase static coordinate system
Figure BDA0003371831940000144
(23) Detecting three-phase currents of power windings, e.g. ipa、ipb、ipcTaking the electric quantity of the power winding current two-phase static coordinate system
Figure BDA0003371831940000145
(24) The relation of the electric quantity of the motor under a unified dq coordinate system of the brushless doubly-fed motor is obtained:
Figure BDA0003371831940000146
Figure BDA0003371831940000147
Figure BDA0003371831940000148
in the above formula Za、ZbRespectively, motor parameters, assumed to be known quantities.
(25) Since the control winding current has been forced to orient, i.e.
Figure BDA0003371831940000151
After the current amplitude of the control winding is measured, the angles under which the electric quantity of the power winding is transformed to the current orientation coordinate system of the control winding are jointly obtained are as follows:
Figure BDA0003371831940000152
in the above formula
Figure BDA0003371831940000153
(26) Substituting sine and cosine obtained in the step (25) into a component u of a power winding voltage d axis under the control winding current orientation obtained in the step (24)d pQ-axis component uq pAnd d-axis component i of power winding currentd pQ-axis component iq p；
The principle of the step (3) is shown in fig. 5:
(31) after the system adopts the orientation, the voltage vector of the control winding, the current of the control winding and the output voltage vector form a fixed angle. In order to continue to use the advantage of independent operation control winding current orientation, the whole grid-connected system still adopts a control winding current orientation control strategy, and the angle between an output voltage vector and a control winding current vector is delta;
(32) based on the established equivalent circuit model of the brushless doubly-fed motor, the output power P is obtaineds、QsThe form of the flux linkage of the power winding and the current of the control winding is expressed as follows:
Figure BDA0003371831940000154
wherein, Ps、QsRespectively outputting active power and reactive power for the system; Ψc pA power winding flux linkage vector under a control winding current coordinate system; i.e. ic cFor controlling the winding voltage vector, Lsp、LrThe inductive reactance of the power winding and the rotor winding are respectively; mpr、McrMutual inductance of the power winding, the control winding and the rotor winding is respectively realized; omegapFor power winding angular frequency, j is the complex operator.
(33) Further processing the power expression in step (32) to obtain the output power Ps、QsExpressed as the flux linkage amplitude and the control winding current amplitude and the included angle between them: :
Figure BDA0003371831940000161
wherein, | Ψc pI is the flux linkage amplitude of the power winding; ic cI is the flux linkage amplitude of the power winding; theta is the power winding flux linkage amplitude | Ψc pAnd control winding current amplitude Ic cThe included angle between | s.
The step (4) includes the following steps, as shown in fig. 6:
(41) for analysing the active power P of the systemsAnd control winding current amplitude IcAnd (3) carrying out small signal analysis on the control relation to obtain a variable quantity expression as follows:
Figure BDA0003371831940000162
wherein, | Ic'c_finI is the final value of the current of the control winding after the active power is changed; ic c_iniAnd | is the initial value of the control winding current before the active power changes.
(42) With simultaneous reactive power Q for the analysis systemsBy varying the angle theta with respect to the control windingcAnd (3) carrying out small signal analysis on the control relation to obtain a variable quantity expression as follows:
Figure BDA0003371831940000163
wherein Q is* sA given value of reactive power is obtained; delta thetacTo control the winding angle variation value.
The step (5) includes the following steps, as shown in fig. 8:
(51) setting the proportionality coefficient K of the d-axis PI controller according to design experiencepdAnd integral coefficient KidFor smaller values, the parameters are correspondingly equal:
Kpq＝Kpd Kiq＝Kid……(15)
(52) will control the winding current d-axis reference value
Figure BDA0003371831940000164
And d component
Figure BDA0003371831940000165
Difference of (2)
Figure BDA0003371831940000166
Inputting a d-axis PI controller, outputting PI by the d-axis controllerd(ii) a Will control the q-axis reference value of the winding current
Figure BDA0003371831940000171
And q-axis component
Figure BDA0003371831940000172
Difference of (2)
Figure BDA0003371831940000173
Inputting a q-axis PI controller, wherein the output of the q-axis PI controller is PIq；
(53) Mathematical relation of formula (16) exists in the mathematical model of the brushless doubly-fed motor, wherein Rsc、LscSingle-phase resistance, inductance, K, of the control winding of the brushless dual-feed machine1、K2Is a sum of K3Respectively obtaining comprehensive parameters of the motor inductors through series-parallel connection:
Figure BDA0003371831940000174
therefore, on the basis that the control action of the set current inner loop PI controller is strong enough, the output superposition feedforward control quantity of the current inner loop d axis and the current inner loop q axis is the d axis reference value of the control winding voltage
Figure BDA0003371831940000175
And q-axis reference value
Figure BDA0003371831940000176
(54) Using θ in step (3)cSuperimposed reactive power output angle variation delta thetacI.e. to control the winding transformation angle theta* cWill be
Figure BDA0003371831940000177
After the inverse partial transformation, the inverse partial transformation is carried out,obtaining three-phase reference values u of control winding voltageca *、ucb *、ucc *：
Figure BDA0003371831940000178
Will uca *、ucb *、ucc *Sending the signal into a pulse width modulation module to obtain a switch driving signal of a machine side converter, and driving the converter by using the signal to output a corresponding control winding three-phase voltage uca、ucb、uccAnd the closed-loop control of the control winding current of the brushless dual-feeder is realized.
Compared with the prior art, the brushless double-fed motor power generation system provided by the invention has the following advantages that the power generation system is based on control winding current fixed-down grid-connected control:
(1) the method adopts control winding current orientation strategies for independent operation and grid-connected operation, the system has a uniform control framework, complex control algorithm switching during independent operation and grid-connected operation control is avoided, high adaptability is achieved, and control complexity is reduced;
(2) the method adopts a control winding current directional control strategy for grid connection, provides a scheme for expanding the coordinate system to control the reactive power through rotation, and provides a new idea for control.
For further explanation of the grid-connected power control method of the brushless doubly-fed machine provided in the embodiment of the present invention, the following detailed description is made with reference to specific examples:
the first embodiment is as follows:
the following takes a brushless doubly-fed machine with a 32kW wound rotor structure in a power generation mode as an example, and further details an implementation process of the present invention with reference to fig. 1 to 8.
The brushless doubly-fed machine is a nonlinear, strong-coupling and multivariable system, and in order to simplify analysis, only the action of the air gap fundamental wave magnetic field of the brushless doubly-fed machine is generally considered, and the following assumptions are made: (1) stator without counting the influence of stator and rotor tooth slotThe inner surface and the outer surface of the rotor are smooth, and the air gap is uniform; (2) the influences of ferromagnetic material saturation, magnetic hysteresis and eddy current are not counted, and parameters are linearized; (3) considering only the pole pair number p in the magnetic field generated by stator winding and rotor windingpNumber of sum pole pairs pcThe effect of the fundamental wave ignores the influence of harmonic magnetic field.
When the brushless doubly-fed motor adopts a generator convention, a brushless doubly-fed motor mathematical model under a double synchronous rotation dq coordinate system can be obtained according to the coordinate transformation relation. Wherein the voltage equation is:
Figure BDA0003371831940000181
Figure BDA0003371831940000182
Figure BDA0003371831940000183
in the formula: u. ofpd、upq、ucd、ucqDq-axis voltage components of the power winding and the control winding respectively; i.e. ipd、ipq、icd、icq、ird、irqDq-axis current components of the power winding, the control winding and the rotor winding respectively; Ψpd、Ψpq、Ψcd、Ψcq、Ψrd、ΨrqDq-axis flux linkage components of the power winding, the control winding and the rotor winding respectively; rsp、Rsc、RrThe single-phase resistance values of the power winding, the control winding and the rotor winding are respectively; omegapThe angular frequency of the electric quantity of the power winding; omegamIs the mechanical angular frequency of the rotor; p is a radical ofp、pcThe pole pairs of the power winding and the control winding are respectively; s is the laplace operator.
The flux linkage equation is:
Figure BDA0003371831940000191
Figure BDA0003371831940000192
Figure BDA0003371831940000193
in the formula: l issp、Lsc、LrThe single-phase self-inductance values of the power winding, the control winding and the rotor winding are respectively; mpr、McrThe single-phase mutual inductance values of the power winding and the rotor winding and the single-phase mutual inductance values of the control winding and the rotor winding are respectively.
The electromagnetic torque equation is:
Figure BDA0003371831940000194
in the mathematical model of the double synchronous coordinate system, dq coordinate systems of the power winding, the control winding and the rotor winding are respectively represented by omegap、(pp+pc)Ωm﹣ωp、ωp﹣ppΩmIs rotated in space.
According to the mathematical model of the brushless doubly-fed motor, mathematical relations exist among all electric quantities. Under the simple closed-loop control of the control winding current, after independent no-load or on-load starting, the electric quantity steady-state value of the sampling system is utilized in the synchronous grid-connected stage, meanwhile, the rotating speed of the motor is sampled instantaneously, the droop coefficient of the motor is calculated, and the grid-connected instantaneous droop control of the brushless doubly-fed motor under the independent/grid-connected operation working condition is realized by combining simple mathematical calculation. The implementation process comprises the following steps:
the control winding current dq component in the unified reference dq coordinate system is obtained as shown in principle in fig. 2.
(1) The mechanical angular speed omega of the motor rotor is obtained by mounting a code disc on the rotorm；
(2) According to the number of pole pairs p of the power windingpControl the number p of pole pairs of the windingcAngular frequency omega of the current of the power windingpMechanical angular velocity omega of rotormCalculating the angular frequency omega of the current of the control windingc：
ωc＝(pp+pc)Ωm-ωp……(25)
(3) The calculated omegacInputting the integral link to obtain an angle thetacWherein s is the laplace operator:
Figure BDA0003371831940000201
(4) detecting three-phase currents of control windings, e.g. ica、icb、iccAt θcConverting the control winding current from a static abc coordinate to a unified reference dq coordinate system by Park coordinate transformation as a coordinate transformation angle to obtain icd、icq：
Figure BDA0003371831940000202
The voltage and current dq components of the power winding in the unified reference dq coordinate system are obtained according to the principle shown in fig. 3.
(5) Mounting code disc on brushless double-fed motor rotor to obtain rotor position angle thetar；
(6) Combined power winding pole pair number ppControl the number p of pole pairs of the windingcIn the step (1), thetacRotor position angle thetarCalculating to obtain the angle thetap：θp＝(pp+pc)θr-θc……(28)
(7) Sensing three-phase line voltage of power winding, e.g. upab、upbc、upcaConverting it into a phase voltage upa、upb、upc(ii) a At thetapConverting the power winding voltage from a stationary abc coordinate to a unified reference dq coordinate system by Park coordinate transformation as a coordinate transformation angle to obtain a component upd、upq：
Figure BDA0003371831940000211
(8) Detecting three-phase currents of power windings, e.g. ipa、ipb、ipc(ii) a At thetapAs a coordinate transformation angle, the power winding current is transformed from a stationary abc coordinate to a unified reference dq coordinate system by Park coordinate transformation, resulting in a component ipd、ipq：
Figure BDA0003371831940000212
According to the diagram of fig. 4, the power winding voltage, current d, q quantities under the control winding current orientation are obtained.
(9) Sensing three-phase line voltage of power winding, e.g. upab、upbc、upcaConvert it into phase voltage upa、upb、upcTaking the electric quantity u of the two-phase stationary coordinate systemα p、uβ p；
(10) Detecting three-phase currents of power windings, e.g. ipa、ipb、ipcTaking the electric quantity i of the two-phase static coordinate systemα p、iβ p；
(11) And obtaining the relation of the electric quantity of the motor under the unified dq coordinate system:
Figure BDA0003371831940000213
Figure BDA0003371831940000214
Figure BDA0003371831940000215
in the above formula Za、ZbRespectively, motor parameters, assumed to be known quantities.
(12) Since the control winding current has been forced to orient, i.e. iq cWhen the current amplitude of the control winding is measured, the angle of the power winding electric quantity transformed to the control winding current orientation coordinate system is obtained in a combined mode as follows:
Figure BDA0003371831940000221
in the above formula
Figure BDA0003371831940000222
(13) Substituting the sine and cosine obtained in step (12) into the values u of the voltage and current d and q of the power winding under the control winding current orientation obtained in steps (32) and (33)d p、uq p、id p、iq p；
According to the figure 9, a closed-loop control system required by the brushless double-fed motor power generation system is built.
(14) The voltage, current d and q components u of the power winding obtained in the step (13)d p、uq p、id p、iq pCalculating the output active power P of the systemsReactive power Qs；
(15) The active power variation formula is as follows:
Figure BDA0003371831940000223
the change quantity delta I of the current of the control winding obtained by the active power change quantityc c_ampIs described as Δ Ic c1；
(16) Active power PsWith a given reference value P* sComparing to obtain a difference value (P)s *﹣Ps) And input d-axis PI controlDevice, according to experience KP＝1KI25 … … (37), the d-axis PI controller output Δ I is obtainedc c2；
(17) Adding the control winding current values obtained in the step (15) and the step (16) to obtain a control winding current inner loop given reference value icq *；
(18) The active power variation formula is as follows:
Figure BDA0003371831940000224
recording the angle variation of the control winding obtained by the reactive power variation as delta thetac1；
(19) Active power QsWith a given reference value Q* sComparing to obtain a difference value (Q)s *﹣Qs) Inputting into PI controller, and empirically KP＝0.25KI0.006 … … (39), the control winding conversion angle output value delta theta is obtainedc2；
(20) Adding the angle change values of the control windings obtained in the step (18) and the step (19) to obtain the angle change value delta theta of the control windingc；
(21) Setting the proportionality coefficient K of the d-axis PI controller and the q-axis PI controller according to design experiencepd、KpqAnd integral coefficient Kid、KiqRespectively as follows: kpq＝Kpd＝3Kiq＝Kid＝75……(40)
(22) The d-axis component i of the winding current will be controlledcdWith a reference value icd *Comparing to obtain a difference value (i)cd *﹣icd) And input into a d-axis PI controller to obtain an output PI of the d-axis PI controllerd：
Figure BDA0003371831940000231
The q-axis component i of the winding current will be controlledcqWith a reference value icq *Comparing to obtain a difference value (i)cq *﹣icq) And input into q-axis PI controller to obtain q-axis PI controller output PIq：
Figure BDA0003371831940000232
(23) Obtaining the control winding coordinate transformation reference value theta from the step (20)* cComprises the following steps:
Figure BDA0003371831940000233
(24) using theta* cAnd inverse Park transformation, consisting of
Figure BDA0003371831940000235
Obtaining three-phase reference values u of control winding voltageca *、ucb *、ucc *：
Figure BDA0003371831940000234
Will uca *、ucb *、ucc *Sending the signal into an SVPWM module to obtain a switch driving signal of a machine side converter, and driving the converter by using the signal to obtain a corresponding control winding three-phase voltage uca、ucb、uccApplying the voltage to a control winding of the brushless doubly-fed motor to realize closed-loop control on the current of the control winding;
(25) the control of the constant-down grid-connected control of the winding current under the power generation operation of the brushless doubly-fed motor is completed, and a set of control framework can be used for independent/grid-connected control to complete system control.
The second embodiment is as follows:
the motor parameters and experimental waveforms of the present embodiment are given below with reference to fig. 10 to 13. The present embodiment consists of a wound rotor brushless double-fed motor, a load, a power grid, a back-to-back power electronic converter and a controller using the method of the present invention.
And when the brushless doubly-fed motor generates electricity and operates at 400 rpm, controlling the grid connection according to the control method.
Fig. 10 shows an active and reactive power jump waveform during the grid-connected control of the brushless doubly-fed motor, and fig. 11 shows a steady-state operation waveform of the brushless doubly-fed motor system, and it can be seen that the output current waveform has better sine degree under the control scheme, and meets the grid-connected requirement;
as shown in fig. 12, after the brushless doubly-fed machine is operated in a grid-connected mode, the power control active power jump waveform; fig. 13 is a reactive power jump waveform. As can be seen from the figure, the system controls the winding current q axis to be always kept at zero, and the orientation is completed. And controlling the winding conversion angle to jump to meet the reactive power requirement when the reactive power jumps. The invention does not change the whole control framework of the system during the independent/grid-connected operation, thereby ensuring the uniformity of the system.
In conclusion, the grid-connected control method can use a set of directional control structure under independent/grid-connected conditions, simplifies the system switching control algorithm, effectively improves the safety and stability of the system, and has great flexibility and adaptability.
Those not described in detail in this specification are within the skill of the art. It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Claims (9)

1. A power control method of a brushless doubly-fed machine is characterized by comprising the following steps:
s1, detecting three-phase current of the control winding and converting the abc/dq coordinate of the three-phase currentObtaining d-axis component i of control winding currentcdAnd q-axis component icq；
Detecting three-phase current of the power winding and carrying out abc/dq coordinate transformation on the three-phase current to obtain a d-axis component i of the power winding currentpdAnd q-axis component ipq；
Detecting three-phase line voltage of the power winding, converting the three-phase line voltage into phase voltage, and performing abc/dq coordinate transformation on the phase voltage to obtain a d-axis component u of the power winding voltagepdAnd q-axis component upq；
S2, winding the power current d-axis component ipdAnd q-axis component ipqAnd d-axis component u of power winding voltagepdAnd q-axis component upqCurrent orientation i converted to control winding by motor internal relationcqObtaining d-axis component of power winding voltage under control winding coordinate system under 0
Figure FDA0003371831930000011
Component of q axis
Figure FDA0003371831930000012
And d-axis component i of power winding currentd pQ-axis component
Figure FDA0003371831930000013
S3, calculating the power of the grid-connected system based on the equivalent circuit of the brushless double-fed motor, and controlling the voltage of the power winding under the winding coordinate system after S2 transformation
Figure FDA0003371831930000014
And power winding current id p、
Figure FDA0003371831930000015
Calculating to obtain output active power PsReactive power QsThe expression of (1);
s4, obtaining the output power P of the S3 through the internal relation of the brushless doubly-fed motors、QsConversion of expression intoControl winding current vector icFlux linkage vector Ψ with the power windingpForms thereof;
s5, based on the control winding current orientation, applying a small signal mode to specifically solve the relation delta I between the active power variation delta P and the control winding current amplitude variationcThe current is used as the d-axis input of the current inner ring;
at the same time, the relation delta theta between the active power variation delta Q and the control winding current angle variation is solvedcTaking the control winding angle transformation increment value as a control winding angle transformation increment value;
s6, obtaining the power control relation under the orientation of the brushless dual-feeder control winding current through the steps S1-S5, and controlling the winding current amplitude IcUsed for controlling the system to output active power and change the angle thetacUsed for controlling the system to output reactive power.
2. The power control method of brushless doubly fed machine as claimed in claim 1, wherein said step S2 comprises:
s2-1, mounting code disc on the rotor to obtain mechanical angular speed omega of the motor rotorm；
S2-2, according to the pole pair number p of the power windingpControl the number p of pole pairs of the windingcAngular frequency omega of the current of the power windingpAnd rotor mechanical angular velocity omegamObtaining the angular frequency omega of the control winding currentc：
S2-3, controlling the angular frequency omega of the winding currentcThe current angle of the control winding is obtained by an input integration link and is converted to the angle theta required by a unified reference dq coordinate systemc；
S2-4, detecting and controlling three-phase current i of windingca、icb、iccAnd by thetacAs a coordinate transformation angle, converting the control winding current from a static abc coordinate to a unified reference dq coordinate system through Park coordinate transformation to obtain a d-axis component i of the control winding currentcdAnd q-axis component icq：
S2-5, controlling the winding coordinate transformation angle theta according to the step S2-3cRotor position angle thetarObtaining a transformation angle theta for transforming power winding current from a stationary abc coordinate to a unified reference dq coordinate systemp；
S2-6, detecting three-phase current i of power windingpa、ipb、ipcAnd by thetapAs a coordinate transformation angle, converting the power winding current from a static abc coordinate to a unified reference dq coordinate system through Park coordinate transformation to obtain a power winding current d-axis component ipdAnd q-axis component ipq：
S2-7, detecting the voltage u of the three-phase line of the power windingpab、upbc、upcaConverted into phase voltage upa、upb、upcAnd is given by thetapAs a coordinate transformation angle, converting the power winding current from a static ABC coordinate to a unified reference dq coordinate system through Park coordinate transformation to obtain a power winding voltage d-axis component updAnd q-axis component upq；
S2-8, converting the power winding current i in the steps S2-6 and S2-7pd、ipqVoltage upd、upqThe components of the current are respectively converted into a control winding current directional coordinate system through the relation of an internal model of the motor
Figure FDA0003371831930000021
3. The power control method of brushless doubly fed machine as claimed in claim 2, wherein said step S3 comprises:
s3-1, representing the power winding voltage as a power winding flux linkage and a control winding current form according to a motor model:
Figure FDA0003371831930000031
therein, Ψc p、uc p、ic cRespectively controlling the current orientation lower power winding voltage flux linkage vector, the voltage vector and the control winding current amplitude; r isp、rrImpedance of power winding and rotor winding, Lsp、LrThe self inductive reactance of the power winding and the rotor winding are respectively; mpr、McrMutual inductance between the power winding and the rotor winding and between the control winding voltage and the rotor winding are respectively; omegap、ωsrRespectively carrying out power winding angular frequency and slip frequency; s is a differential operator; j is a complex operator;
s3-2, similarly, representing the power winding current as a power winding flux linkage and control winding current form according to the motor model:
Figure FDA0003371831930000032
wherein the parameters are in accordance with step S3-1;
s3-3, obtaining a system power expression by the power winding voltage and the power winding current obtained in the steps S3-1 and S3-2:
Figure FDA0003371831930000033
where S is the apparent power, Ps、QsRespectively representing active power and reactive power of the system;
s3-4, controlling the current orientation of the winding, and controlling the active power P of the system based on the phase angle control thoughtsReactive power QsExpressed as:
Figure FDA0003371831930000041
Figure FDA0003371831930000042
where | Ψc p|、|Ic cI respectively represents the flux linkage amplitude of the power winding and the current amplitude of the control winding; theta is a control windingAnd the current included angle between the power winding flux linkage and the control winding under the current coordinate system.
4. The power control method of brushless doubly fed machine as claimed in claim 3, wherein said step S4 comprises:
s4-1, active power variation delta PsAnd reactive power variation Δ QsRespectively as follows:
Figure FDA0003371831930000043
wherein Ic c_iniFor controlling the initial value of the amplitude of the winding current, Ic' c_finIn order to control the final value of the winding current, delta theta is the angle variation of the control winding, and other parameters are consistent with those in the step S3-2;
s4-2, current amplitude I relative to control windingcWhen the angle change is small, it can be considered that:
cosΔθ≈1,sinΔθ≈Δθ；
s4-3, the power change expression in S4-1 is finished according to the steps, and finally the expression can be expressed as follows:
Figure FDA0003371831930000044
wherein Δ Ic c_ampTo control the amount of change, Δ I, due to the magnitude of the winding currentc c_angCausing a variation in order to control the winding angle.
5. The power control method of brushless doubly fed machine as claimed in claim 4, wherein said step S5 includes:
s5-1, according to the analysis of the system active power control in the step S4, the control equation is obtained as follows:
Figure FDA0003371831930000045
wherein
Figure FDA0003371831930000051
The active power of the system can be controlled according to the relational expression;
s5-2, marking the variation of the control winding caused by the variation of the active power in the step S5-1 as delta Ic1；
S5-3, analyzing the reactive power control of the system by using a small signal analysis tool to obtain a specific control equation as follows:
Figure FDA0003371831930000052
wherein QsThe given value of the reactive power can realize the control of the reactive power of the system according to the relational expression;
s5-4, recording the angle variation of the control winding obtained by the reactive power variation in the step S5-3 as: delta thetac1。
6. The power control method of brushless doubly fed machine as claimed in claim 5, wherein said step S6 includes:
s6-1, designing a power outer ring controller according to the step S5, and setting a proportional coefficient K of an outer ring d-axis PI controllerPqAnd integral coefficient KIqValue K ofPq＝KPdKIq＝KIdWhere the proportionality coefficient K of the d-axis PI controllerPdAnd integral coefficient KIdObtaining according to experience;
s6-2, converting the active power outer loop reference value
Figure FDA0003371831930000053
And the actual value PsDifference of (2)
Figure FDA0003371831930000054
Input to PI controller to obtain output of Δ Ic2；
S6-3, obtaining the control winding current amplitude variation delta I obtained in the step S5-2c1And step S6-2, obtaining the output quantity Delta I of the current amplitude of the control windingc2Adding to obtain d-axis given value i of inner ring of current of control windingc d*；
S6-4, carrying out outer loop reference value on reactive power
Figure FDA0003371831930000055
And the actual value QsDifference of (2)
Figure FDA0003371831930000056
The input PI controller obtains its output as delta thetac2；
S6-5, controlling the winding angle variation delta theta obtained in the step S5-4c1And the control winding angle output quantity delta theta obtained in the step S6-4c2The total variation of the control winding angle obtained by adding is as follows: delta thetac；
S6-6, changing the angle delta theta obtained in the step S6-5cSuperimposed on the control winding for varying the angle thetacThe transformation angle reference value is obtained as:
Figure FDA0003371831930000061
7. the power control method of brushless doubly fed machine as claimed in claim 6, further comprising step S7; the step S7 includes:
s7-1, obtaining an inner ring expression by a motor mathematical model as follows:
Figure FDA0003371831930000062
wherein
Figure FDA0003371831930000063
S7-2, multiplying the electric quantity obtained in the step S2 by the motor parameter to obtain the compensation quantity;
and S7-3, superposing the obtained d-axis q-axis compensation quantity to the current inner loop output, so that the feedforward compensation is completed, and the influence speed of the system is improved.
8. The power control method of brushless doubly fed machine as claimed in claim 7, further comprising step S8; the step S8 includes:
s8-1, setting q-axis PI controller proportionality coefficient KpqAnd integral coefficient KiqValue K ofpq＝Kpd Kiq＝KidWhere the proportionality coefficient K of the d-axis PI controllerpdAnd integral coefficient KidObtaining according to experience;
s8-2, controlling the d-axis reference value of the winding current
Figure FDA0003371831930000064
And d component
Figure FDA0003371831930000065
Difference of (2)
Figure FDA0003371831930000066
Obtaining output PI of d-axis controller by input d-axis PI controllerd(ii) a Will control the q-axis reference value of the winding current
Figure FDA0003371831930000067
And q-axis component
Figure FDA0003371831930000068
Difference of (2)
Figure FDA0003371831930000069
Obtaining an output PI of a q-axis controller by an input q-axis PI controllerq；
S8-3, obtaining a system current inner ring specific expression according to the internal dq mathematical model of the brushless doubly-fed motor:
Figure FDA0003371831930000071
Figure FDA0003371831930000072
wherein R issc、LscSingle-phase resistance, inductance, K, of the control winding of the brushless dual-feed machine1、K2And K3Equivalent parameters obtained after series connection and parallel connection of the motor inductors are respectively obtained;
s8-4, controlling the winding current angle theta in the step S6-6* cWill be provided with
Figure FDA0003371831930000073
Obtaining a three-phase reference value u of the control winding voltage after Park inverse transformationca *、ucb *、ucc *And sending the signal to a pulse width modulation module to obtain a switch driving signal of a machine side converter, and driving the converter by using the signal to output a corresponding control winding three-phase voltage uca、ucb、uccAnd the closed-loop control of the control winding current of the brushless dual-feeder is realized.
9. A power control method for brushless doubly fed machine as claimed in claim 8, characterized in that the three phase reference values u of the winding voltage are controlledca *、ucb *、ucc *Comprises the following steps:
Figure FDA0003371831930000074
wherein the content of the first and second substances,
Figure FDA0003371831930000075
the d-axis component and the q-axis component, θ x, of the control winding voltage obtained in step S8cThe control winding angle obtained in step S6.
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