CN115333414B - Coordinate transformation initial angle identification method for brushless doubly-fed independent power generation system - Google Patents
Coordinate transformation initial angle identification method for brushless doubly-fed independent power generation system Download PDFInfo
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- 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
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- 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
- H02P21/0003—Control strategies in general, e.g. linear type, e.g. P, PI, PID, using robust control
- H02P21/0017—Model reference adaptation, e.g. MRAS or MRAC, useful for control or parameter estimation
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- 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
- H02P21/14—Estimation or adaptation of machine parameters, e.g. flux, current or voltage
- H02P21/18—Estimation of position or speed
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Abstract
The invention relates to the technical field of brushless doubly-fed motors, and particularly discloses a coordinate transformation initial angle identification method of a brushless doubly-fed independent power generation system. Under any steady-state working condition, the initial angle of the coordinate transformation is reversely adjusted according to the error of the measured value of the voltage of the control winding and the adjustable model, and when the error of the adjustable model and the measured voltage enters an acceptable range, the accurate identification of the required initial angle of the coordinate transformation can be realized, so that reliable guarantee is provided for accurate coordinate transformation and vector orientation control. The method can cancel the code wheel, improve the reliability of the system, ensure the accuracy of coordinate transformation, and is suitable for brushless doubly-fed motors with different structures.
Description
Technical Field
The invention relates to the technical field of brushless doubly-fed motors, in particular to a coordinate transformation initial angle identification method of a brushless doubly-fed independent power generation system.
Background
The China is vigorous in developing clean energy, and wind power generation is one of hot spots. The brushless doubly-fed motor is a novel motor developed on the basis of the traditional brushed doubly-fed motor, the special double-stator and other structural designs of the brushless doubly-fed motor can retain the advantages of slip power capacity, flexible speed-changing constant-frequency power generation control, low construction cost and the like of the brushed doubly-fed motor, meanwhile, the brush slip ring structure is canceled, the running reliability of the motor is improved, the maintenance and operation cost is reduced, and the brushless doubly-fed motor has outstanding advantages in severe environments and difficult maintenance occasions such as offshore wind power, remote mountain areas and the like.
For brushless doubly-fed power generation application, various control strategies have been proposed currently based on a unified dq reference frame model, wherein vector control is widely applied in brushless doubly-fed power generation control due to higher flexibility and accuracy. Such as various flux linkages, voltage directional control in independent power generation applications, dual mode control in grid-connected power generation applications, low voltage ride through control, unbalanced condition control, and the like. These control strategies require accurate coordinate transformation results of the voltage and current, and transformation accuracy is highly dependent on the brushless doubly fed motor transformation angle used. If the coordinate transformation angle has errors, the obtained voltage and current dq component does not meet the mathematical relationship of the motor dq model, and the actual performance of the control strategy is affected. Therefore, it is necessary to acquire accurate motor angle information for the coordinate transformation requirement.
Currently, methods for acquiring motor angle information can be classified into two types, i.e., a speed sensor method and a no-speed sensor method. The speed sensor method is characterized in that a code disc is arranged on a motor rotor, angle information of the motor rotor is obtained through the code disc, and then coordinate transformation and Vector orientation services are provided, for example, a document named as Vector Control DESIGN AND Experimental Evaluation for the Brushless Doubly FED MACHINE, author Dongsheng Zhou, exit IET-Electric Power Applications 3 (4), 2009:247-256 obtains rotating speed and rotor position angle information of a brushless doubly-fed motor through the code disc, and then stator power winding magnetic flux orientation Control is achieved. The method is simple and easy to realize, but the rotation characteristic and maintenance requirement of the speed sensor can reduce the reliability of the brushless doubly-fed power generation system.
Therefore, various speed-free sensor methods are proposed, rotor position angle information of the brushless doubly-fed motor is indirectly obtained through means of electric quantity sampling, mathematical fitting and the like, a code wheel is further omitted, and system reliability is improved. For example, the literature named "An MARS Speed Observer Based on Control Winding Flux for Sensorless Control of Stand-Alone BDFIGs", author Wei Xu, origin IEEE Transactions on Power Electronics 35 (7), 2020:7271-7281 takes control winding flux linkage as an object, and a model reference adaptive method is adopted to obtain rotor position angle information, so that accurate vector orientation control is realized; the Chinese patent application with the name of a method and a system for identifying the rotating speed of a brushless doubly-fed motor, publication number CN106411205B, publication date 2017, 2 and 15, proposes a method for obtaining basic rotating speed based on voltage and current under control of winding current setting, adding the basic rotating speed with the rotating speed trimming amount obtained by frequency error, and obtaining actual rotating speed information; the patent application of China, publication No. CN104518713B, publication No. 2015, 4 month and 15 days, proposes a method for regulating and controlling the current amplitude of a winding in a closed loop mode according to the deviation between the actual rotating speed and the expected rotating speed, and further realizing the speed regulation of the motor; the method is named as a speed identification method of a brushless doubly-fed motor, and is disclosed in China patent application No. CN106953573A, publication No. 2017, 7-14, and finally obtains rotor position angle and rotating speed information by taking an error of a current included angle under a synchronous speed coordinate system of a power winding as an object and performing closed-loop adjustment through a PI controller.
However, although the existing speed-free sensor method aiming at the brushless doubly-fed motor is intuitive in principle and simple to realize, only the rotating speed information can be identified, and the angle information cannot be acquired as accurate coordinate transformation service; or the rotor position angle is firstly identified, then the coordinate transformation angle required by orientation is indirectly obtained, and errors can be introduced in the middle process to influence the accuracy.
Disclosure of Invention
The invention provides a coordinate transformation initial angle identification method of a brushless doubly-fed independent power generation system, which solves the technical problems that: the existing brushless doubly-fed motor speed-free sensor method is mostly electric application service, only recognizes rotation speed information, or needs to recognize rotor position angle information first and acquire coordinate transformation angle information again, and errors can be introduced in the middle process to influence transformation accuracy.
In order to solve the technical problems, the invention provides a coordinate transformation initial angle identification method of a brushless doubly-fed independent power generation system, which comprises the following steps:
S1, detecting three-phase line voltage u pab、upbc、upca, and then carrying out coordinate transformation, arcsine calculation and differential calculation to obtain actual power winding frequency omega p;
S2, the expected value omega p * of the power winding frequency is differed from the actual power winding frequency omega p, the obtained error is input into a first PI controller to obtain the control winding frequency omega c, and then integration is carried out to obtain the control winding coordinate transformation angle theta c;
S3, performing Park inverse transformation on the coordinate transformation angle theta c of the control winding, a set d-axis given value u cd * of the control winding voltage and a set q-axis given value u cq * of the control winding voltage, and performing pulse width modulation on the basis of the transformation result so as to control the converter to generate a required three-phase voltage u ca、ucb、ucc of the control winding and drive the brushless doubly-fed motor to operate under an open-loop control condition;
S4, detecting three-phase current i ca、icb、icc of the control winding, and converting the three-phase current i ca、icb、icc of the control winding from a static ABC coordinate system to a uniform reference dq coordinate system based on a control winding coordinate conversion angle theta c after the brushless double-fed motor reaches a steady-state working condition to obtain a d-axis component i cd and a q-axis component i cq of the control winding current;
S5, detecting a three-phase current i pa、ipb、ipc of a power winding and a three-phase line voltage u pab、upbc、 upca of the power winding, and carrying out coordinate transformation on the three-phase current i pa、ipb、ipc of the power winding and the three-phase line voltage u pab、upbc、upca of the power winding based on an actual power winding frequency omega p after the brushless double-fed motor reaches a steady-state working condition to obtain a d-axis component u 'pd of the quasi-power winding voltage, a q-axis component u' pq of the quasi-power winding voltage, a d-axis component i 'pd of the quasi-power winding current and a q-axis component i' pq of the quasi-power winding current;
S6, inputting an actual power winding frequency omega p, a control winding frequency omega c, a control winding current d-axis component i cd, a control winding current q-axis component i cq, a quasi-power winding voltage d-axis component u 'pd, a quasi-power winding voltage q-axis component u' pq, a quasi-power winding current d-axis component i 'pd and a quasi-power winding current q-axis component i' pq into a brushless doubly fed machine universal steady-state dq coordinate system model to obtain a control winding voltage d-axis component adjustable model u ^ cd and a control winding voltage q-axis component adjustable model u ^ cq;
S7, constructing an objective function based on the set control winding voltage d-axis given value u cd *, the control winding voltage q-axis given value u cq *, the control winding voltage d-axis component adjustable model u ^ cd and the control winding voltage q-axis component adjustable model u ^ cq:
S8, inputting an error epsilon obtained by the objective function into a second PI controller to obtain a coordinate transformation initial angle theta p0; superposing the theta p0 with the quasi-power winding coordinate transformation angle theta' p to obtain a power winding transformation angle theta p; then theta p is used for replacing theta' p to carry out coordinate transformation on the power winding; when epsilon reaches an acceptable range and theta p0 is a stable output value, theta p0 at the moment is the initial position angle of the required coordinate transformation.
Further, the step S1 specifically includes the steps of:
S11, detecting the three-phase line voltage u pab、upbc、upca of the power winding, and obtaining the three-phase line voltage u pa、upb、upc of the power winding through mathematical calculation of the following formula:
S12, converting the three-phase voltage u pa、upb、upc of the power winding from a static ABC coordinate system to an alpha beta static coordinate system by Clark conversion of the following formula to obtain a component u pα、upβ:
S13, performing arcsine operation on u pα or u pβ, and further performing differential calculation on the operation result and obtaining an absolute value to obtain the actual power winding frequency omega p.
Further, the step S2 specifically includes the steps of:
S21, the expected value omega p * of the power winding frequency is differed from the actual power winding frequency omega p, the obtained error is input into a first PI controller to calculate the following formula, and the control winding frequency omega c is obtained:
Wherein k p_c、ki_c is a proportional coefficient and an integral coefficient of the first PI controller respectively, and 1/s is an integral link;
S22, inputting the control winding frequency omega c into an integration module for integration to obtain a control winding coordinate transformation angle theta c.
Further, the step S3 specifically includes the steps of:
S31, setting a control winding voltage d-axis given value u cd * and a control winding voltage q-axis given value u cq * as any safe operation values;
S32, performing Park inverse transformation on the control winding voltage d-axis given value u cd * and the control winding voltage q-axis given value u cq * by using a control winding coordinate transformation angle theta c to obtain a three-phase given value u ca *、ucb *、ucc * of the control winding voltage:
S33, sending a three-phase given value u ca *、ucb *、ucc * of the control winding voltage into a pulse width modulation module to obtain a switch driving signal of the machine side converter;
S34, driving the converter by using a switch driving signal of the converter to output corresponding control winding three-phase voltage u ca、ucb、ucc, so as to realize the starting and open-loop operation of the brushless doubly-fed motor.
Further, in the step S4, the control winding three-phase current i ca、icb、icc is converted from the stationary ABC coordinate system to the unified reference dq coordinate system to obtain a control winding current d-axis component i cd and a control winding current q-axis component i cq:
further, the step S5 specifically includes the steps of:
S51, detecting three-phase current i pa、ipb、ipc of a power winding;
S52, integrating the actual power winding frequency omega p to obtain a quasi-power winding coordinate transformation angle theta' p;
S53, performing Park coordinate transformation on the power winding three-phase voltage u pa、upb、upc and the power winding three-phase current i pa、ipb、ipc obtained in the step S11 by using a quasi power winding coordinate transformation angle theta ' p to obtain a quasi power winding voltage d-axis component u ' pd, a quasi power winding voltage q-axis component u ' pq, a quasi power winding current d-axis component i ' pd and a quasi power winding current q-axis component i ' pq as shown in the following formula:
further, the step S6 specifically includes the steps of:
S61, substituting the actual power winding frequency omega p, the quasi-power winding voltage d-axis component u 'pd, the quasi-power winding voltage q-axis component u' pq, the quasi-power winding current d-axis component i 'pd and the quasi-power winding current q-axis component i' pq into the following formula of a general steady-state dq coordinate system model of the brushless doubly-fed motor to obtain a rotor winding current d-axis component calculated value i ^ rd and a rotor winding current q-axis component calculated value i ^ rq:
Wherein r p is a power winding resistor, r c is a control winding resistor, L p is a power winding self-inductance, L c is a control winding self-inductance, M pr is a mutual inductance between the power winding and the rotor, and M cr is a mutual inductance between the control winding and the rotor;
S62, substituting the calculated rotor winding current d-axis component calculated value i ^ rd, the rotor winding current q-axis component calculated value i ^ rq, the control winding frequency omega c, the control winding current d-axis component i cd and the control winding current q-axis component i cq into the following formula of a general steady-state dq coordinate system model of the brushless doubly-fed motor to obtain a control winding voltage d-axis component adjustable model u ^ cd and a control winding voltage q-axis component adjustable model u ^ cq:
Further, the step S8 specifically includes the steps of:
S81, inputting the error epsilon obtained by the objective function in the step S7 into a second PI controller to perform the following operation to obtain a coordinate transformation initial angle theta p0:
wherein k p_θ、ki_θ is the proportional coefficient and the integral coefficient of the second PI controller respectively, and 1/s is the integral link;
S82, superposing the coordinate transformation initial angle theta p0 and the quasi-power winding coordinate transformation angle theta' p to obtain a power winding transformation angle theta p;
S83, replacing a quasi-power winding coordinate transformation angle theta' p with a power winding transformation angle theta p to perform dq coordinate transformation on the power winding three-phase voltage u pa、upb、upc and the power winding three-phase current i pa、ipb、ipc:
S84, when the error epsilon obtained by the objective function reaches an acceptable range and the initial coordinate transformation angle theta p0 is a stable output value, the theta p0 at the moment is the initial position angle of the required coordinate transformation.
Aiming at the coordinate transformation angle information requirement in the brushless doubly-fed independent power generation application, the coordinate transformation initial angle identification method provided by the invention is based on a universal dq coordinate coefficient mathematical model of a brushless doubly-fed motor, and based on a simple and visual model reference self-adaptive principle, a control winding voltage adjustable model is constructed, and a target error function is further constructed on the basis. Under any steady-state working condition, the initial angle of the coordinate transformation is reversely adjusted according to the error of the measured value of the voltage of the control winding and the adjustable model, and when the error of the adjustable model and the measured voltage enters an acceptable range, the accurate identification of the required initial angle of the coordinate transformation can be realized, so that reliable guarantee is provided for accurate coordinate transformation and vector orientation control. The method can cancel the code wheel, improve the reliability of the system, ensure the accuracy of coordinate transformation, and is suitable for brushless doubly-fed motors with different structures.
Drawings
FIG. 1 is a schematic diagram of a power winding Clark conversion provided by an embodiment of the present invention;
FIG. 2 is a schematic diagram of power winding frequency acquisition provided by an embodiment of the present invention;
FIG. 3 is a schematic diagram of the coordinate transformation angle acquisition of the control winding provided by the embodiment of the invention;
FIG. 4 is a schematic diagram of open loop control of a brushless doubly-fed power generation system provided by an embodiment of the invention;
FIG. 5 is a schematic diagram of acquisition of the dq component of the control winding current provided by an embodiment of the present invention;
FIG. 6 is a schematic diagram of the acquisition of the dq component of the voltage of the quasi-power winding provided by an embodiment of the present invention;
FIG. 7 is a schematic diagram of initial angle identification of power winding coordinate transformation provided by an embodiment of the present invention;
FIG. 8 is a waveform diagram of a target error ε provided by an embodiment of the invention;
FIG. 9 is a diagram of the recognition result of the initial angle θ p0 according to the embodiment of the present invention;
fig. 10 is a waveform diagram of a brushless doubly-fed independent operation system based on accurate dq conversion according to an embodiment of the present invention.
Detailed Description
The following examples are given for the purpose of illustration only and are not to be construed as limiting the invention, including the drawings for reference and description only, and are not to be construed as limiting the scope of the invention as many variations thereof are possible without departing from the spirit and scope of the invention.
The embodiment of the invention provides a coordinate transformation initial angle identification method of a brushless doubly-fed independent power generation system, which comprises steps S1 to S8.
S1, detecting three-phase line voltage u pab、upbc、upca, and then carrying out coordinate transformation, arcsine calculation and differential calculation to obtain actual power winding frequency omega p.
As shown in fig. 1 and 2, the step S1 specifically includes the steps of:
S11, detecting the three-phase line voltage u pab、upbc、upca of the power winding, and obtaining the three-phase line voltage u pa、upb、upc of the power winding through mathematical calculation of the following formula:
S12, converting the three-phase voltage u pa、upb、upc of the power winding from a static ABC coordinate system to an alpha beta static coordinate system by Clark conversion of the following formula to obtain a component u pα、upβ:
S13, performing arcsine operation on u pα or u pβ, and further performing differential calculation on the operation result and obtaining an absolute value to obtain the actual power winding frequency omega p.
S2, the expected value omega p * of the power winding frequency is differed from the actual power winding frequency omega p, and the obtained error is input into a first PI controller to obtain the control winding frequency omega c and then integrated to obtain the control winding coordinate transformation angle theta c.
As shown in fig. 3, the step S2 specifically includes the steps of:
S21, the expected value omega p * of the power winding frequency is differed from the actual power winding frequency omega p, the obtained error is input into a first PI controller to calculate the following formula, and the control winding frequency omega c is obtained:
Wherein k p_c、ki_c is a proportional coefficient and an integral coefficient of the first PI controller respectively, and 1/s is an integral link;
S22, inputting the control winding frequency omega c into an integration module for integration to obtain a control winding coordinate transformation angle theta c.
S3, performing Park inverse transformation on the coordinate transformation angle theta c of the control winding, the set d-axis given value u cd * of the control winding voltage and the set q-axis given value u cq * of the control winding voltage, and performing pulse width modulation on the basis of the transformation result to control the converter to generate the required three-phase voltage u ca、ucb、ucc of the control winding so as to drive the brushless double-fed motor to operate under an open-loop control condition.
As shown in fig. 4, the step S3 specifically includes the steps of:
S31, setting a control winding voltage d-axis given value u cd * and a control winding voltage q-axis given value u cq * as any safe operation values;
S32, performing Park inverse transformation on the control winding voltage d-axis given value u cd * and the control winding voltage q-axis given value u cq * by using a control winding coordinate transformation angle theta c to obtain a three-phase given value u ca *、ucb *、ucc * of the control winding voltage:
S33, sending a three-phase given value u ca *、ucb *、ucc * of the control winding voltage into a pulse width modulation module to obtain a switch driving signal of the machine side converter;
S34, driving the converter by using a switch driving signal of the converter to output corresponding control winding three-phase voltage u ca、ucb、ucc, so as to realize the starting and open-loop operation of the brushless doubly-fed motor.
S4, detecting three-phase current i ca、icb、icc of the control winding, and after the brushless double-fed motor reaches a steady-state working condition, as shown in FIG. 5, converting the three-phase current i ca、icb、icc of the control winding from a static ABC coordinate system to a uniform reference dq coordinate system based on a control winding coordinate conversion angle theta c to obtain a d-axis component i cd and a q-axis component i cq of the control winding current.
In this step S4, the control winding three-phase current i ca、icb、icc is converted from the stationary ABC coordinate system to the unified reference dq coordinate system to obtain the control winding current d-axis component i cd, the control winding current q-axis component i cq, using the following:
S5, detecting a power winding three-phase current i pa、ipb、ipc and a power winding three-phase line voltage u pab、upbc、 upca, and carrying out coordinate transformation on the power winding three-phase current i pa、ipb、ipc and the power winding three-phase line voltage u pab、upbc、upca based on an actual power winding frequency omega p after the brushless double-fed motor reaches a steady-state working condition to obtain a quasi-power winding voltage d-axis component u 'pd, a quasi-power winding voltage q-axis component u' pq, a quasi-power winding current d-axis component i 'pd and a quasi-power winding current q-axis component i' pq.
As shown in fig. 6, the step S5 specifically includes the steps of:
S51, detecting three-phase current i pa、ipb、ipc of a power winding;
S52, integrating the actual power winding frequency omega p to obtain a quasi-power winding coordinate transformation angle theta' p;
S53, performing Park coordinate transformation on the power winding three-phase voltage u pa、upb、upc and the power winding three-phase current i pa、ipb、ipc obtained in the step S11 by using a quasi power winding coordinate transformation angle theta ' p to obtain a quasi power winding voltage d-axis component u ' pd, a quasi power winding voltage q-axis component u ' pq, a quasi power winding current d-axis component i ' pd and a quasi power winding current q-axis component i ' pq as shown in the following formula:
s6, inputting the actual power winding frequency omega p, the control winding frequency omega c, the control winding current d-axis component i cd, the control winding current q-axis component i cq, the quasi-power winding voltage d-axis component u 'pd, the quasi-power winding voltage q-axis component u' pq, the quasi-power winding current d-axis component i 'pd and the quasi-power winding current q-axis component i' pq into a brushless doubly-fed machine universal steady-state dq coordinate system model to obtain a control winding voltage d-axis component adjustable model u ^ cd and a control winding voltage q-axis component adjustable model u ^ cq.
S7, constructing an objective function based on the set control winding voltage d-axis given value u cd *, the control winding voltage q-axis given value u cq *, the control winding voltage d-axis component adjustable model u ^ cd and the control winding voltage q-axis component adjustable model u ^ cq:
S8, inputting an error epsilon obtained by the objective function into a second PI controller to obtain a coordinate transformation initial angle theta p0; superposing the theta p0 with the quasi-power winding coordinate transformation angle theta' p to obtain a power winding transformation angle theta p; then theta p is used for replacing theta' p to carry out coordinate transformation on the power winding; when epsilon reaches an acceptable range and theta p0 is a stable output value, theta p0 at the moment is the initial position angle of the required coordinate transformation.
As shown in fig. 7, the step S8 specifically includes the steps of:
S81, inputting the error epsilon obtained by the objective function in the step S7 into a second PI controller to perform the following operation to obtain a coordinate transformation initial angle theta p0:
wherein k p_θ、ki_θ is the proportional coefficient and the integral coefficient of the second PI controller respectively, and 1/s is the integral link;
S82, superposing the coordinate transformation initial angle theta p0 and the quasi-power winding coordinate transformation angle theta' p to obtain a power winding transformation angle theta p;
S83, replacing a quasi-power winding coordinate transformation angle theta' p with a power winding transformation angle theta p to perform dq coordinate transformation on the power winding three-phase voltage u pa、upb、upc and the power winding three-phase current i pa、ipb、ipc:
S84, when the error epsilon obtained by the objective function reaches an acceptable range and the initial coordinate transformation angle theta p0 is a stable output value, the theta p0 at the moment is the initial position angle of the required coordinate transformation.
The following takes a brushless doubly-fed motor with a 30kW wound rotor structure as an example, and the implementation of the invention is further described in detail with reference to the accompanying drawings.
Brushless doubly-fed machines are a nonlinear, strongly coupled, multivariable system, and for simplicity of analysis, only the effect of the brushless doubly-fed machine air-gap fundamental field is generally considered, and it is assumed that:
The influence of tooth grooves of a stator and a rotor is not counted, the inner surface of the stator and the outer surface of the rotor are smooth, and the air gap is uniform;
Irrespective of the influence of saturation, hysteresis, eddy currents of the ferromagnetic material, linearization of the parameters;
only the effect of the fundamental wave of the pole pair number p p and the pole pair number p c is considered in the magnetic fields generated by the stator winding and the rotor winding, and the influence of the harmonic magnetic field is ignored.
Based on the assumption, by adopting a generator convention and according to a coordinate transformation relation, a unified synchronous coordinate system dq model of the brushless doubly-fed motor which is most widely applied at present can be obtained:
r p is a power winding resistor, r c is a control winding resistor, L p is a power winding self-inductance, L c is a control winding self-inductance, M pr is a mutual inductance between the power winding and the rotor, and M cr is a mutual inductance between the control winding and the rotor. The remaining parameters are: a power winding current d-axis component i pd, a power winding current q-axis component i pq, a control winding current d-axis component i cd, a control winding current q-axis component i cq, a rotor winding current d-axis component i rd, and a rotor winding current q-axis component i rq.
According to the dq mathematical model of the brushless doubly-fed motor, there is a mathematical relationship between the motor parameters and the respective electric quantities. Under simple open loop control, the identification of the initial angle of the brushless doubly-fed motor can be realized by utilizing data under the working conditions of steady-state no-load and resistive load and combining simple mathematical calculation. The implementation process comprises the following steps:
(1) According to the principle shown in fig. 1, the three-phase line voltage u pab、upbc、upca of the power winding is detected, and the three-phase line voltage u pa、upb、upc of the power winding is obtained through mathematical calculation:
(2) The power winding three-phase voltage u pa、upb、upc is converted from the constant amplitude value of the static ABC coordinate system to the alpha beta static coordinate system through Clark conversion, and the component u pα、upβ is obtained:
(3) Substituting u pα to perform arcsine operation according to the principle shown in fig. 2, and performing differential calculation on the operation result to obtain an absolute value to obtain the actual power winding frequency omega p;
(4) According to the principle shown in fig. 3, the parameter k p_c＝-1,ki_c = -5 of the first PI controller is set, the power winding frequency given value ω p * = 100 PI rad/s; inputting errors of omega p * and omega p into a PI controller to obtain omega c; further inputting omega c into an integration link to obtain an angle theta c:
(5) The brushless double-fed motor operates under the pure resistive load working condition of 450 revolutions per minute and 10 omega with load. According to the principle shown in fig. 4, a d-axis given value u cd * =30V, q axis given value u cq * =0v of the control winding voltage is set, and u cd *、ucq * is subjected to Park inverse transformation by using θ c to obtain a three-phase given value u ca *、ucb *、ucc * of the control winding voltage:
Sending u ca *、ucb *、ucc * into a pulse width modulation module to obtain a switch driving signal of the machine side converter, and driving the converter by using the signal to output a corresponding control winding three-phase voltage u ca、ucb、ucc, so as to realize open-loop control of the brushless double-fed motor;
(6) According to the principle shown in fig. 5, detecting the three-phase current i ca、icb、icc of the power winding; and (3) performing Park coordinate transformation based on the theta c obtained in the step (2), and converting the control winding current from a static ABC coordinate to a uniform reference dq coordinate to obtain a dq component i cd、icq:
(7) Integrating the power winding frequency omega p obtained in the step (1) to obtain a quasi-power winding coordinate transformation angle theta' p;
(8) According to the principle shown in fig. 6, detecting the three-phase current i pa、ipb、ipc of the power winding; converting the power winding current from a static ABC coordinate to a uniform reference dq coordinate through Park coordinate conversion based on the quasi-power winding coordinate conversion angle theta 'p in the step (7) to obtain a quasi-power winding current dq component i' pd、i'pq;
(9) Detecting the three-phase line voltage u pab、upbc、upca of the power winding, and obtaining the three-phase line voltage u pa、upb、upc of the power winding through mathematical calculation:
(10) Based on the quasi-power winding coordinate transformation angle θ 'p in step (7), converting the power winding phase voltage from the stationary ABC coordinate to the uniform reference dq coordinate through Park coordinate transformation to obtain a quasi-power winding voltage dq component u' pd、u'pq:
(11) Substituting omega p obtained in the step (1) and u' pd、u'pq、i'pd、i'pq obtained in the step (4) into a rotor current calculation formula Obtaining a rotor winding current d-axis component calculated value i ^ rd and a rotor winding current q-axis component calculated value i ^ rq;
(12) Substituting i ^ rd、i^ rq obtained by calculation and ω c =10pi rad/s obtained by the step (2) and i cd、icq obtained by the step (3) into the control winding dq voltage adjustable model Calculating to obtain a d-axis component u ^ cd and a q-axis component u ^ cq of the control winding voltage adjustable model;
(13) Substituting u cd *、ucq *、u^ cd、u^ cq into Obtaining a target error function epsilon:
(14) According to the principle shown in fig. 7, a parameter k p_θ＝0.001,ki_θ =0.01 of the second PI controller is set, the target error function epsilon is input into the second PI controller, and the second PI controller outputs a coordinate transformation initial angle theta p0; superimposing theta p0 on theta' p to jointly serve as a power winding transformation angle theta p, and performing dq transformation on the power winding voltage and current;
(15) When epsilon is smaller than 0.1 and theta p0 is a stable output value, at the moment, theta p0 =1.2pi rad is the initial position angle of the required coordinate transformation.
The identification of the initial angle theta p0 of the coordinate transformation of the brushless doubly-fed motor under the open loop load working condition is completed, and the obtained initial angle can be used for Park transformation to obtain an accurate voltage current dq component of the power winding.
The motor parameters and the identification waveforms of the present example are given below in conjunction with fig. 8-10. The example consists of a wound rotor brushless doubly-fed motor, an independent load, a back-to-back type power electronic converter and a common current inner loop-voltage outer loop double-loop controller.
Firstly, when the brushless double-fed motor generates power and runs at 450 revolutions per minute and is loaded with 10 omega resistive load, the coordinate transformation initial angle identification method provided by the patent is applied. As can be seen from the waveform diagram of the target error epsilon shown in fig. 8 and the identification result diagram of the initial angle theta p0 shown in fig. 9, the target error function epsilon gradually converges to 0, and meanwhile, the initial angle theta p0 gradually converges to-2.525 rad, thereby verifying the feasibility of the proposed method.
Further, after the initial angle identification is realized, the open loop control system used in the patent is switched to be a common current inner loop-voltage outer loop double loop controller (the bandwidth of the inner loop is set to be 10 pi rad/s, and the bandwidth of the outer loop is set to be 2 pi rad/s). Fig. 10 shows dynamic waveforms of the power winding line voltage u pab and the power winding current i pa when the brushless doubly-fed independent operation system is switched to a common double-loop controller and is put into a 16kW load from an idle load. It can be seen that after coordinate transformation and control are performed based on the initial angle obtained by identification, the output power winding voltage u pab of the brushless doubly-fed independent operation system can be recovered and stabilized only by one period when no load is suddenly put into load, and the accuracy of the angle obtained by identification is verified.
In summary, according to the method for identifying the initial angle of coordinate transformation of the brushless doubly-fed independent power generation system, which is provided by the embodiment of the invention, aiming at the information requirement of the angle of coordinate transformation in the application of brushless doubly-fed independent power generation, a universal dq coordinate coefficient model of a brushless doubly-fed motor is taken as a basis, a voltage adjustable model of a control winding is constructed based on a simple and visual model reference self-adaptive principle, and a target error function is further constructed on the basis. Under any steady-state working condition, the initial angle of the coordinate transformation is reversely adjusted according to the error of the measured value of the voltage of the control winding and the adjustable model, and when the error of the adjustable model and the measured voltage enters an acceptable range, the accurate identification of the required initial angle of the coordinate transformation can be realized, so that reliable guarantee is provided for accurate coordinate transformation and vector orientation control. The method can cancel the code wheel, improve the reliability of the system, ensure the accuracy of coordinate transformation, and is suitable for brushless doubly-fed motors with different structures. In short, the identification method provided by the invention can accurately obtain the initial angle theta p0 of the brushless doubly-fed motor, and the accuracy of coordinate transformation can be ensured by applying the initial angle theta p0 to an independent operation control system, so that the independent operation control system is ensured to realize the expected design performance.
The above examples are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above examples, and any other changes, modifications, substitutions, combinations, and simplifications that do not depart from the spirit and principle of the present invention should be made in the equivalent manner, and the embodiments are included in the protection scope of the present invention.
Claims (8)
1. The method for identifying the coordinate transformation initial angle of the brushless doubly-fed independent power generation system is characterized by comprising the following steps of:
S1, detecting three-phase line voltage u pab、upbc、upca, and then carrying out coordinate transformation, arcsine calculation and differential calculation to obtain actual power winding frequency omega p;
S2, the expected value omega p * of the power winding frequency is differed from the actual power winding frequency omega p, the obtained error is input into a first PI controller to obtain the control winding frequency omega c, and then integration is carried out to obtain the control winding coordinate transformation angle theta c;
S3, performing Park inverse transformation on the coordinate transformation angle theta c of the control winding, a set d-axis given value u cd * of the control winding voltage and a set q-axis given value u cq * of the control winding voltage, and performing pulse width modulation on the basis of the transformation result so as to control the converter to generate a required three-phase voltage u ca、ucb、ucc of the control winding and drive the brushless doubly-fed motor to operate under an open-loop control condition;
S4, detecting three-phase current i ca、icb、icc of the control winding, and converting the three-phase current i ca、icb、icc of the control winding from a static ABC coordinate system to a uniform reference dq coordinate system based on a control winding coordinate conversion angle theta c after the brushless double-fed motor reaches a steady-state working condition to obtain a d-axis component i cd and a q-axis component i cq of the control winding current;
S5, detecting a three-phase current i pa、ipb、ipc of a power winding and a three-phase line voltage u pab、upbc、upca of the power winding, and carrying out coordinate transformation on the three-phase current i pa、ipb、ipc of the power winding and the three-phase line voltage u pab、upbc、upca of the power winding based on an actual power winding frequency omega p after the brushless double-fed motor reaches a steady-state working condition to obtain a d-axis component u 'pd of the quasi-power winding voltage, a q-axis component u' pq of the quasi-power winding voltage, a d-axis component i 'pd of the quasi-power winding current and a q-axis component i' pq of the quasi-power winding current;
S6, inputting an actual power winding frequency omega p, a control winding frequency omega c, a control winding current d-axis component i cd, a control winding current q-axis component i cq, a quasi-power winding voltage d-axis component u 'pd, a quasi-power winding voltage q-axis component u' pq, a quasi-power winding current d-axis component i 'pd and a quasi-power winding current q-axis component i' pq into a brushless doubly fed machine universal steady-state dq coordinate system model to obtain a control winding voltage d-axis component adjustable model u ^ cd and a control winding voltage q-axis component adjustable model u ^ cq;
S7, constructing an objective function based on the set control winding voltage d-axis given value u cd *, the control winding voltage q-axis given value u cq *, the control winding voltage d-axis component adjustable model u ^ cd and the control winding voltage q-axis component adjustable model u ^ cq:
S8, inputting an error epsilon obtained by the objective function into a second PI controller to obtain a coordinate transformation initial angle theta p0; superposing the theta p0 with the quasi-power winding coordinate transformation angle theta' p to obtain a power winding transformation angle theta p; then theta p is used for replacing theta' p to carry out coordinate transformation on the power winding; when epsilon reaches an acceptable range and theta p0 is a stable output value, theta p0 at the moment is the initial position angle of the required coordinate transformation.
2. The method for identifying the initial angle of the coordinate transformation of the brushless doubly-fed independent power generation system according to claim 1, wherein the step S1 specifically comprises the steps of:
S11, detecting the three-phase line voltage u pab、upbc、upca of the power winding, and obtaining the three-phase line voltage u pa、upb、upc of the power winding through mathematical calculation of the following formula:
S12, converting the three-phase voltage u pa、upb、upc of the power winding from a static ABC coordinate system to an alpha beta static coordinate system by Clark conversion of the following formula to obtain a component u pα、upβ:
S13, performing arcsine operation on u pα or u pβ, and further performing differential calculation on the operation result and obtaining an absolute value to obtain the actual power winding frequency omega p.
3. The method for identifying the initial angle of the coordinate transformation of the brushless doubly-fed independent power generation system according to claim 1, wherein the step S2 specifically comprises the steps of:
S21, the expected value omega p * of the power winding frequency is differed from the actual power winding frequency omega p, the obtained error is input into a first PI controller to calculate the following formula, and the control winding frequency omega c is obtained:
Wherein k p_c、ki_c is a proportional coefficient and an integral coefficient of the first PI controller respectively, and 1/s is an integral link;
S22, inputting the control winding frequency omega c into an integration module for integration to obtain a control winding coordinate transformation angle theta c.
4. The method for identifying the initial angle of the coordinate transformation of the brushless doubly-fed independent power generation system according to claim 2, wherein the step S3 specifically comprises the steps of:
S31, setting a control winding voltage d-axis given value u cd * and a control winding voltage q-axis given value u cq * as any safe operation values;
S32, performing Park inverse transformation on the control winding voltage d-axis given value u cd * and the control winding voltage q-axis given value u cq * by using a control winding coordinate transformation angle theta c to obtain a three-phase given value u ca *、ucb *、ucc * of the control winding voltage:
S33, sending a three-phase given value u ca *、ucb *、ucc * of the control winding voltage into a pulse width modulation module to obtain a switch driving signal of the machine side converter;
S34, driving the converter by using a switch driving signal of the converter to output corresponding control winding three-phase voltage u ca、ucb、ucc, so as to realize the starting and open-loop operation of the brushless doubly-fed motor.
5. The method for identifying the initial angle of the coordinate transformation of the brushless doubly-fed independent power generation system according to claim 2, wherein in the step S4, the control winding three-phase current i ca、icb、icc is converted from a stationary ABC coordinate system to a uniform reference dq coordinate system by the following formula to obtain a control winding current d-axis component i cd and a control winding current q-axis component i cq:
6. the method for identifying the initial angle of the coordinate transformation of the brushless doubly-fed independent power generation system according to claim 2, wherein the step S5 specifically comprises the steps of:
S51, detecting three-phase current i pa、ipb、ipc of a power winding;
S52, integrating the actual power winding frequency omega p to obtain a quasi-power winding coordinate transformation angle theta' p;
S53, performing Park coordinate transformation on the power winding three-phase voltage u pa、upb、upc and the power winding three-phase current i pa、ipb、ipc obtained in the step S11 by using a quasi power winding coordinate transformation angle theta ' p to obtain a quasi power winding voltage d-axis component u ' pd, a quasi power winding voltage q-axis component u ' pq, a quasi power winding current d-axis component i ' pd, and a quasi power winding current q-axis component i ' pq, where the quasi power winding voltage d-axis component u ' pd, the quasi power winding voltage q-axis component u ' pq are as follows:
7. The method for identifying the initial angle of the coordinate transformation of the brushless doubly-fed independent power generation system according to claim 2, wherein the step S6 specifically comprises the steps of:
S61, substituting the actual power winding frequency omega p, the quasi-power winding voltage d-axis component u 'pd, the quasi-power winding voltage q-axis component u' pq, the quasi-power winding current d-axis component i 'pd and the quasi-power winding current q-axis component i' pq into the following formula of a general steady-state dq coordinate system model of the brushless doubly-fed motor to obtain a rotor winding current d-axis component calculated value i ^ rd and a rotor winding current q-axis component calculated value i ^ rq:
Wherein r p is a power winding resistor, r c is a control winding resistor, L p is a power winding self-inductance, L c is a control winding self-inductance, M pr is a mutual inductance between the power winding and the rotor, and M cr is a mutual inductance between the control winding and the rotor;
S62, substituting the calculated rotor winding current d-axis component calculated value i ^ rd, the rotor winding current q-axis component calculated value i ^ rq, the control winding frequency omega c, the control winding current d-axis component i cd and the control winding current q-axis component i cq into the following formula of a general steady-state dq coordinate system model of the brushless doubly-fed motor to obtain a control winding voltage d-axis component adjustable model u ^ cd and a control winding voltage q-axis component adjustable model u ^ cq:
8. The method for identifying the initial angle of the coordinate transformation of the brushless doubly-fed independent power generation system according to claim 2, wherein the step S8 specifically comprises the steps of:
S81, inputting the error epsilon obtained by the objective function in the step S7 into a second PI controller to perform the following operation to obtain a coordinate transformation initial angle theta p0:
wherein k p_θ、ki_θ is the proportional coefficient and the integral coefficient of the second PI controller respectively, and 1/s is the integral link;
S82, superposing the coordinate transformation initial angle theta p0 and the quasi-power winding coordinate transformation angle theta' p to obtain a power winding transformation angle theta p;
S83, replacing a quasi-power winding coordinate transformation angle theta' p with a power winding transformation angle theta p to perform dq coordinate transformation on the power winding three-phase voltage u pa、upb、upc and the power winding three-phase current i pa、ipb、ipc:
S84, when the error epsilon obtained by the objective function reaches an acceptable range and the initial coordinate transformation angle theta p0 is a stable output value, the theta p0 at the moment is the initial position angle of the required coordinate transformation.
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