CN114172213B - Power control method of brushless doubly-fed motor - Google Patents
Power control method of brushless doubly-fed motor Download PDFInfo
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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
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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
- H02J3/381—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
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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
- H02J3/50—Controlling the sharing of the out-of-phase component
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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
- 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
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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
- 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
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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
- 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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- 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 doubly-fed motor, which adopts the same directional control strategy under the independent operation/grid-connected operation working condition of a system, simplifies the control program and ensures the unified control architecture of a power generation system. The method is based on a control strategy of controlling winding current orientation, expands the conversion angle of the control winding into the new control degree of freedom for adding the new control degree of freedom, specifically analyzes the amplitude of the control winding for controlling the active power of the system, and outputs reactive power by the angle control system, thereby realizing effective control of the active power and the reactive power of the system. The novel control scheme is provided for the grid-connected control system, the control complexity of the system is simplified, and the safety and stability of the system are improved.
Description
Technical Field
The invention relates to the technical field of motor control, in particular to a power control method of a brushless doubly-fed motor.
Background
A brushless doubly-fed machine (BDFM) can realize variable-speed constant-frequency power generation by only rotating a power capacity by a factor of the difference of the required frequency converter, meanwhile, because the special structural design is adopted, the electric brush and the slip ring are omitted, the running reliability of the motor is improved, and the maintenance and operation cost is reduced, so that the electric generator has a wide application prospect in a power generation system.
In the power generation application, especially in micro-grid application such as wind power generation, ship shaft-belt power generation and the like, in order to improve the power supply reliability, uninterrupted power supply to critical loads needs to be ensured, and the brushless doubly-fed motor should have the capabilities of independently carrying, jointly carrying 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 is a research hot spot at present. 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 aiming at different control targets.
The independent operation control system controls the target to output voltage amplitude and frequency, the brushless double-fed independent operation power generation system is researched in the prior literature, the literature [7] adopts a single-loop vector control thought, and controls the dq component of the power winding by utilizing the dq axis component of the voltage of the control winding; the literature [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-loop control system has the advantages of strong non-ideal load capacity, easy realization of output current limiting protection, rapid dynamic response and the like [9-10] and becomes a main stream control scheme. Different orientation modes of the double-loop control system often determine the control difficulty of the system, wherein the documents [11-12] adopt control winding current orientation schemes, and the orientation schemes are implemented on the control winding side without acquiring power winding side electric quantity information, so that the measurement structure of the control system is simplified, meanwhile, the running state of the system is not influenced by load impact, and the advantages of convenience in current limiting control, great guarantee of the safety of the system and the like become a better alternative control scheme.
The grid-connected operation control system aims at outputting active power and reactive power, and has been mentioned in literature for a brushless double-fed grid-connected control system. The main control method includes 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.
The vector control is divided into different orientation modes, and the literature [22] adopts a rotor flux linkage orientation mode to realize the control of the brushless doubly-fed motor, but the electric quantity value of a rotor winding is difficult to measure and is obtained by calculating the electric quantity of a control winding and a power winding, so that the realization difficulty is increased; the 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 the control of the output power is better realized, but the orientation is implemented at the power winding side, so that the control winding is inconvenient to carry out current limiting control, and meanwhile, the stability of the power grid fault is poor.
In order to avoid the system control algorithm complexity caused by the switching of the system directional control strategy when the independent operation and grid-connected operation modes are switched, and simultaneously, the special advantages of controlling the winding current orientation under the independent operation are adopted, the brushless doubly-fed grid-connected system control winding current orientation lower control strategy is provided for completing the unification of the independent operation and grid-connected operation control framework, and meanwhile, the protection of the whole system can be better completed when the power grid faults such as low voltage ride-through are conducted after the grid connection of the control side, so that the safety of the system is greatly enhanced, and the requirements of the power generation system in the independent mode and the grid connection mode are met.
Disclosure of Invention
The invention aims to provide a power control method of a brushless doubly-fed motor, which aims to solve the problems that the control complexity is increased and the grid connection instant has impact due to the directional control algorithm switching when the working condition of an independent/grid connection double-mode operation system is switched.
In order to solve the technical problems, the technical scheme of the invention is as follows: provided is a power control method of a brushless doubly-fed motor, comprising the steps of:
S1, detecting three-phase current of a control winding and performing abc/dq coordinate transformation on the three-phase current to obtain a d-axis component i cd and a q-axis component i cq of the control winding current;
Detecting three-phase current of the power winding and performing abc/dq coordinate transformation on the three-phase current to obtain a d-axis component i pd and a q-axis component i pq of the current of the power winding;
Detecting the three-phase line voltage of the power winding, converting the three-phase line voltage into phase voltage, and obtaining a d-axis component u pd and a q-axis component u pq of the power winding after abc/dq coordinate transformation of the phase voltage;
S2, transforming the d-axis component i pd and the q-axis component i pq of the power winding current and the d-axis component u pd and the q-axis component u pq of the power winding voltage to the control winding current orientation i cq =0 through the internal relation of the motor to obtain the d-axis component of the power winding voltage in the control winding coordinate system Q-axis component/>Power winding current d-axis component i d p, q-axis component/>
S3, carrying out grid-connected system power calculation based on a brushless doubly-fed motor equivalent circuit, and controlling power winding voltage under a winding coordinate system after S2 conversionAnd power winding current i d p,/>Calculating to obtain expressions of output active power P s and reactive power Q s;
S4, converting the output power P s、Qs expression obtained in the S3 into a form of a control winding current vector i c and a power winding flux linkage vector ψ p through the internal relation of the brushless doubly fed motor;
S5, based on control winding current orientation, a small signal mode is applied, and the relation DeltaI c between the active power variation DeltaP and the control winding current amplitude variation is solved specifically and is used as the current inner ring d-axis input;
Meanwhile, the relation delta theta c between the active power variable delta Q and the control winding current angle variable is solved specifically, and is used as a control winding angle transformation increment value;
S6, obtaining a power control relation of the brushless doubly-fed motor under the control of the current orientation of the winding through the steps S1-S6, wherein the current amplitude I c of the control winding is used for controlling the system to output active power, and the transformation angle theta c is used for controlling the system to output reactive power.
Further, the step S2 includes:
S2-1, obtaining the mechanical angular velocity omega m of the motor rotor by installing a code wheel on the rotor;
S2-2, obtaining a control winding current angular frequency omega c according to the power winding pole pair number p p, the control winding pole pair number p c, the current angular frequency omega p of the power winding and the mechanical angular speed omega m of the rotor:
S2-3, inputting the angular frequency omega c of the control winding current into an integration link to obtain the angle of the control winding current, and transforming the angle to an angle theta c required by a unified reference dq coordinate system;
S2-4, detecting a control winding three-phase current i ca、icb、icc, taking theta c as a coordinate transformation angle, and obtaining a control winding current d-axis component i cd and a q-axis component i cq after converting the control winding current from a static abc coordinate to a unified reference dq coordinate system through Park coordinate transformation:
S2-5, obtaining a transformation angle theta p used for transforming the power winding current from a static abc coordinate to a unified reference dq coordinate system according to the transformation angle theta c of the control winding coordinate and the rotor position angle theta r in the step S2-3;
s2-6, detecting a three-phase current i pa、ipb、ipc of the power winding, taking theta p as a coordinate transformation angle, and converting the power 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 pd and a q-axis component i pq of the power winding current:
S2-7, converting detected three-phase line voltage u pab、upbc、upca of the power winding into phase voltage u pa、upb、upc, using theta p as a coordinate transformation angle, and converting the current of the power winding from a static ABC coordinate to a unified reference dq coordinate system through Park coordinate transformation to obtain d-axis component u pd and q-axis component u pq of the voltage of the power winding;
S2-8, transforming the power winding current i pd、ipq in the steps S2-6 and S2-7, and the voltage u pd、upq to the lower components of the control winding current directional coordinate system through the internal model relation of the motor to be respectively
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:
Wherein, ψ c p、uc p、ic c are the power winding voltage flux linkage vector, voltage vector and control winding current amplitude under control winding current orientation; r p、rr is the impedance of the power winding and the rotor winding, and L sp、Lr is the self-inductance of the power winding and the rotor winding; m pr、Mcr is the mutual inductance between the power winding and the rotor winding, and between the control winding voltage and the rotor winding; omega p、ωsr respectively power winding angular frequency and slip frequency; s is a differential operator; j is a complex operator;
s3-2, the same way, the power winding current is expressed as a power winding flux linkage and a control winding current form according to a motor model:
wherein the parameters are consistent with step S3-1;
S3-3, obtaining a system power expression by using the power winding voltage and the power winding current obtained in the steps S3-1 and S3-2:
Wherein S is apparent power, and P s、Qs respectively represents active power and reactive power of the system;
S3-4, under the control of winding current orientation, based on a phase angle control thought, the active power P s and the reactive power Q s of the system are expressed as:
wherein |ψ c p|、|Ic c | represents the power winding flux linkage amplitude and the control winding current amplitude, respectively; and theta is the included angle between the flux linkage of the power winding and the current of the control winding under the current coordinate system of the control winding.
Further, the step S4 includes:
S4-1, the active power variation delta P s and the reactive power variation delta Q s are respectively as follows:
Wherein I c c_ini is the initial value of the current amplitude of the control winding, I c'c_fin is the final value of the current of the control winding, delta theta is the angle variation of the control winding, and the rest parameters are consistent with those in the step S3-2;
S4-2, relative to the control winding current amplitude I c, when the angular change is small, it can be considered that:
cosΔθ≈1,sinΔθ≈Δθ；
s4-3, arranging the power variation expression in S4-1 according to the steps can be finally expressed as follows:
Wherein Δi c c_amp is the amount of change caused by the control winding current amplitude, and Δi c c_ang is the amount of change caused by the control winding angle.
Further, the step S5 includes:
S5-1, analyzing the active power control of the system according to the step S4 to obtain a control equation:
Wherein the method comprises the steps of The control of the active power of the system can be realized according to the relation;
S5-2, recording the change quantity of the control winding caused by the change quantity of active power in the step S5-1 as delta I c1;
s5-3, analyzing reactive power control of the system by using a small signal analysis tool to obtain a specific control equation:
wherein Q s is a reactive power given value, and the reactive power of the system can be controlled according to the above relation;
s5-4, recording the angle change quantity of the control winding obtained from the reactive power change quantity in the step S5-3 as: Δθ c1.
Further, the step S6 includes:
S6-1, designing a power outer loop controller according to the step S5, and setting the values K Pq＝KPd KIq＝KId of the proportional coefficient K Pq and the integral coefficient K Iq of an outer loop d-axis PI controller, wherein the proportional coefficient K Pd and the integral coefficient K Id of the d-axis PI controller are obtained empirically;
S6-2, inputting a difference value (P s *-Ps) between the active power outer loop reference value P s * and the actual value P s into a PI controller to obtain an output of delta I c2;
S6-3, adding the control winding current amplitude variation delta I c1 obtained in the step S5-2 and the control winding current amplitude output delta I c2 obtained in the step S6-2 to obtain a control winding current inner ring d-axis given value I c d*;
s6-4, the reactive power outer loop reference value Difference from the actual value Q s/>The input PI controller obtains the output of the PI controller as delta theta c2;
s6-5, adding the control winding angle change quantity delta theta c1 obtained in the step S5-4 and the control winding angle output quantity delta theta c2 obtained in the step S6-4 to obtain the total control winding angle change quantity as follows: Δθ c;
S6-6, superposing the angle change quantity delta theta c obtained in the step S6-5 to a control winding transformation angle theta c to obtain a transformation angle reference value which is:
Further, the step S7 includes:
s7-1, an inner ring expression of the motor is obtained by a motor mathematical model:
Wherein the method comprises the steps of
S7-2, multiplying the electric quantity obtained in the step S2 by motor parameters to obtain the compensation quantity;
s7-3, superposing the obtained d-axis q-axis compensation quantity to the current inner loop output, so that feedforward compensation is completed, and the system influence speed is improved.
Further, the step S8 includes:
S8-1, setting a value K pq＝Kpd Kiq＝Kid of a proportional coefficient K pq and an integral coefficient K iq of the q-axis PI controller, wherein the proportional coefficient K pd and the integral coefficient K id of the d-axis PI controller are obtained empirically;
S8-2, controlling the d-axis reference value of the winding current And d component/>Difference/>The input d-axis PI controller obtains the output PI d of the d-axis controller; control winding current q-axis reference value/>And q-axis component/>Difference/>The input q-axis PI controller obtains an output PI q of the q-axis controller;
S8-3, obtaining a specific expression of a system current inner loop according to a dq mathematical model in the brushless doubly-fed motor:
wherein R sc、Lsc is single-phase resistance and inductance of the brushless doubly-fed motor control winding, and K 1、K2 and K 3 are equivalent parameters obtained after series connection and parallel connection of motor inductances;
S8-4, controlling the winding current angle theta * c in the step S6-6 And obtaining a three-phase reference value u ca *、ucb *、ucc * of the control winding voltage after Park inverse transformation, and sending the three-phase reference value u ca *、ucb *、ucc * to 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 closed-loop control of the control winding current of the brushless double-fed motor.
Further, the control winding voltage three-phase reference u ca *、ucb *、ucc * is:
Wherein, The d-axis component and the q-axis component of the control winding voltage obtained in step S8 are respectively, and θ× c is the control winding angle obtained in step S6.
The power control method of the brushless doubly-fed motor provided by the invention has the beneficial effects that:
According to the technical scheme, grid-connected control of the brushless doubly-fed motor is realized under the condition that the current of the control winding is oriented, the grid-connected control is completed under the condition that the orientation mode is not changed, and the system control architecture is unified. The unified control architecture established by the system simplifies the control difficulty, is oriented to the control side system, is convenient for current limiting, has good stability in coping with power grid faults, and provides great guarantee for the safety and stability of the whole system
Drawings
The invention is further described below with reference to the accompanying drawings:
FIG. 1 is a schematic diagram of a brushless doubly fed motor stand alone/grid-connected operation;
FIG. 2 is a schematic diagram of obtaining the control winding current dq component in a unified reference dq coordinate system; wherein, (a) is a control winding current dq rotation coordinate system; (b) three-phase ABC to two-phase dq conversion for control winding current;
FIG. 3 is a schematic diagram of obtaining the power winding voltage, current dq components 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 for power winding charge;
FIG. 4 is a graph of the correct component acquisition of the power winding in the control winding current coordinate system;
FIG. 5 is a brushless doubly fed motor equivalent circuit;
FIG. 6 is a graph showing the coordinate relationship of the windings of the current direction of the control winding according to the present invention;
FIG. 7 is a graph of the active and reactive coordinate transformation;
FIG. 8 is a reactive control small signal control relationship diagram;
FIG. 9 is a schematic block diagram of a control winding current closed loop control system according to the present invention;
FIG. 10 is a general diagram of experimental waveforms for grid-tie control operation;
FIG. 11 is a steady-state waveform of grid-tie operation;
fig. 12 is a system active power hopping waveform;
fig. 13 is a system reactive power jump waveform.
Detailed Description
The power control method of the brushless doubly-fed motor according to the present invention will be described in further detail with reference to the accompanying drawings and specific embodiments. Advantages and features of the invention will become more apparent from the following description and from the claims. It is noted that the drawings are in a very simplified form and utilize non-precise ratios, and are intended to facilitate a convenient, clear, description of the embodiments of the invention.
The invention provides a brushless doubly-fed motor grid-connected control strategy for controlling winding current orientation, which realizes grid-connected instant, simultaneously meets the requirements of running a wind power system in an independent mode and a grid-connected mode in the future, does not change an orientation scheme under the independent/grid-connected dual-mode running, and builds a unified control framework.
In order to meet the independent grid-connected dual-mode operation condition and establish a unified control framework of the power generation system, the invention provides a control winding current orientation grid-connected control method which is simple to realize, has strong universality of control structure, is applicable to various on-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 independent operation research of the existing brushless double-fed motor and fully utilizes the advantages of simplified design, 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 doubly-fed motor equivalent circuit model with the current of the control winding oriented downwards, active power is output by the system, reactive power is expressed into a flux linkage of the output power winding and a current amplitude form of the control winding, the relation between the current amplitude of the control winding and the active power is analyzed through a small signal form, the relation between a conversion angle of the control winding and the reactive power is controlled, the conversion angle is designed into a new control degree of freedom according to the mathematical relation, the reactive power of the system is controlled, the q-axis of the current of the control winding is forced to be oriented, and therefore independent/grid connection is achieved by adopting the same oriented control strategy, algorithm switching during mode switching is avoided, a control algorithm is greatly simplified, and system stability is guaranteed.
The method comprises the following specific steps:
(1) The control winding three phase currents, i.e., i ca、icb、icc, are detected. As shown in the principle of fig. 2, the control winding current is converted from a stationary three-phase abc coordinate system to a unified reference dq coordinate system to obtain a d-axis component i cd and a q-axis component i cq of the control winding current;
The power winding three phase current is sensed as i pa、ipb、ipc. Converting the power winding current from the static abc coordinate system to a reference dq coordinate system according to the principle shown in fig. 3 to obtain a d-axis component i pd and a q-axis component i pq of the power winding current;
The power winding three-phase voltage is sensed as u pab、upbc、upca. Converting the power winding wire voltage into phase voltage according to the principle shown in fig. 3, and then converting the phase voltage from a static abc coordinate system into a reference dq coordinate system to obtain a d-axis component u pd and a q-axis component u pq of the power winding voltage;
(2) Transforming the d-axis component i pd and the q-axis component i pq of the power winding current and the d-axis component u pd and the q-axis component u pq of the power winding voltage to the lower electric quantity of the control winding current directional coordinate system through the electric quantity relation between the motors, as shown in fig. 4, respectively
(3) Establishing an equivalent circuit diagram of the brushless doubly-fed system, as shown in fig. 5;
(4) Calculating the system output steady power P s and reactive power Q s according to the steps (2) and (3), and expressing the system output steady power P s and the reactive power Q s as a form of controlling a winding current amplitude I c and a power winding flux linkage ψ p;
(5) Carrying out small signal analysis on the active power change rate delta P to obtain the relation between the active power change rate delta P and the control winding current change quantity delta I c; the small signal analysis is carried out on the reactive power change rate delta Q to obtain the relation between the small signal analysis and the control winding transformation angle delta theta c, as shown in figure 7;
(6) A closed loop control system for controlling the dq component of the winding current is constructed according to the principle shown in fig. 9. Converting the power side electric quantity to a control winding coordinate system, namely, converting the control winding current i cd、icq obtained by the detection in the step (3) and a corresponding closed loop reference value The error of the (a) is respectively input into a d-axis proportional-integral controller (Proportion Integration controller) and a q-axis proportional-integral controller (PI controller); d. the output PI d,PIq of the q-axis PI controller obtains the dq component reference value of the control winding voltageThe reactive power is superimposed on the control winding transformation angle theta c by the obtained output delta theta c,/>Obtaining the three-phase reference value/>, of the control winding voltage through Park inverse transformationWill/>The pulse width modulation module is input to generate a driving signal of the machine side converter, and the machine side converter is driven to generate a required control winding three-phase voltage u ca、ucb、ucc to realize the control winding current dq component/>For closed loop reference value/>Is a closed loop tracking of (1); meanwhile, the outer ring also adopts a PI controller to complete the rapid control of the system.
The power control method can finish grid-connected control under the current orientation of the control winding of the system, meet the independent/grid-connected unified architecture and simplify the control algorithm of the system.
The step (1) comprises the following steps, and the principle of the steps is as shown in fig. 2 and 3:
(11) The mechanical angular speed omega m of the motor rotor is obtained by installing a code wheel on the rotor;
(12) The voltage of a power winding which is independently started and sent by the brushless double-fed motor is constant at 50Hz, and the angular frequency omega p is constant at 100 pi rad/s. According to the operation characteristics of the brushless doubly-fed motor, the pole pair number p p of the power winding, the pole pair number p c of the control winding, the current angular frequency 100 pi rad/s of the power winding and the mechanical angular speed omega m of the rotor are substituted into (8), so that the current angular frequency omega c of the control winding is obtained:
ωc＝(pp+pc)Ωm-100π……(1)
(13) Inputting omega c into an integration link to obtain an angle theta c required by the current transformation of the control winding to a unified reference dq coordinate system;
(14) Detecting a control winding three-phase current, such as i ca、icb、icc; using theta c as a coordinate transformation angle, transforming 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 i cd、icq:
(15) Substituting the control winding coordinate transformation angle theta c and the rotor position angle theta r in the step (23) into the step (3) to obtain a transformation angle theta p used for transforming the power winding current from the static abc coordinate to the unified reference dq coordinate system:
θp＝(pp+pc)θr-θc……(3)
(16) Detecting three-phase currents of a power winding, such as i pa、ipb、ipc; using theta p as 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 dq axis component i pd、ipq of the power winding current:
(17) Detecting the three-phase line voltage of the power winding, and converting the three-phase line voltage into phase voltage u pa、upb、upc as u pab、upbc、upca; using theta p as 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 u pd、upq:
the step (2) comprises the following steps, and the principle of the step is shown in fig. 4:
(21) By setting the control winding current q-axis Realizing forced orientation of control winding current so as to determine a reference coordinate system;
(22) Detecting the three-phase line voltage of the power winding, for example u pab、upbc、upca, converting the three-phase line voltage into phase voltage u pa、upb、upc, and taking the electric quantity of the two-phase stationary coordinate system of the power winding voltage
(23) Detecting the three-phase current of the power winding, for example, i pa、ipb、ipc, and taking the electric quantity of the two-phase stationary coordinate system of the power winding current
(24) The electric quantity relation of the motor under the unified dq coordinate system of the brushless doubly-fed motor is obtained:
in the above formula, Z a、Zb is a motor parameter, and is assumed to be a known quantity.
(25) Since the control winding current has been forced to orient, i.eAfter the control winding current amplitude is measured, the power winding electric quantity is jointly obtained and is transformed into the control winding current orientation coordinate system, and the angle is as follows:
In the above
(26) Carrying the sine and cosine obtained in the step (25) into a d-axis component u d p, a q-axis component u q p and a d-axis component i d p and a q-axis component i q p of the power winding voltage under the control of the winding current orientation obtained in the step (24);
the principle of the step (3) is as shown in fig. 5:
(31) After the system adopts orientation, the control winding voltage vector, the control winding current and the output voltage vector are at a fixed angle. In order to keep the advantage of independently running 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 brushless doubly-fed motor equivalent circuit model, the output power P s、Qs is expressed as a power winding flux linkage and a control winding current form as follows:
Wherein, P s、Qs is the active power and reactive power output by the system respectively; psi c p is the power winding flux linkage vector under the control winding current coordinate system; i c c is a control winding voltage vector, and L sp、Lr is the inductive reactance of the power winding and the rotor winding respectively; m pr、Mcr is used for respectively carrying out mutual inductance on the power winding, the control winding and the rotor winding; omega p is the power winding angular frequency and j is the complex operator.
(33) Further finishing the power expression in the step (32), and expressing the output power P s、Qs as the form of the included angle between the flux linkage amplitude and the control winding current amplitude: :
Wherein |ψ c p | is the power winding flux linkage amplitude; i c c is the power winding flux linkage amplitude; θ is the angle between the power winding flux linkage magnitude |ψ c p | and the control winding current magnitude |i c c |.
The step (4) includes the following steps, as shown in fig. 6:
(41) In order to analyze the control relation between the active power P s of the system and the current amplitude I c of the control winding, small signal analysis is carried out on the control winding to obtain the variable quantity expression of the control winding:
wherein I c'c_fin is the final value of the control winding current after the active power is changed; and I c c_ini is the initial value of the current of the control winding before the active power is changed.
(42) Meanwhile, for analyzing the control relation between the reactive power Q s of the system and the transformation angle theta c of the control winding, small signal analysis is carried out on the reactive power Q s, and the variable quantity expression is obtained as follows:
Wherein Q * s is a reactive power given value; Δθ c is the control winding angle change value.
The step (5) includes the steps of:
(51) Setting a proportional coefficient K pd and an integral coefficient K id of the d-axis PI controller to be smaller according to design experience, wherein the parameters are equal to each other correspondingly:
Kpq＝Kpd Kiq＝Kid……(15)
(52) Control winding current d-axis reference value And d component/>Difference/>The d-axis PI controller is input, and the output of the d-axis PI controller is PI d; control winding current q-axis reference value/>And q-axis component/>Difference/>The q-axis PI controller is input, and the output of the q-axis PI controller is PI q;
(53) The mathematical relationship of the formula (16) exists in the brushless doubly-fed motor mathematical model, wherein R sc、Lsc is the single-phase resistance and inductance of the brushless doubly-fed motor control winding respectively, K 1、K2 is the comprehensive parameters obtained by series-parallel connection of motor inductance and K 3 respectively:
Therefore, on the basis that the control effect 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 q axis is the d axis reference value of the control winding voltage And q-axis reference value/>
(54) The change quantity delta theta c of the reactive power output angle superimposed by theta c in the step (3) is the control winding transformation angle theta * c And obtaining a three-phase reference value u ca *、ucb *、ucc * of the control winding voltage through Park inverse transformation:
And u ca *、ucb *、ucc * is sent to a pulse width modulation module to obtain a switch driving signal of the machine side converter, and the converter is driven by the signal to output corresponding control winding three-phase voltage u ca、ucb、ucc, so that closed-loop control of the current of the control winding of the brushless doubly-fed motor is realized.
The brushless doubly-fed motor power generation system provided by the invention is based on control winding current orientation grid-connected control, and has the following advantages compared with the prior art:
(1) The method is characterized in that the independent operation and the grid-connected operation adopt control winding current orientation strategies, the system has a unified control architecture, the complex control algorithm switching during the independent operation and the grid-connected operation control is avoided, the adaptability is higher, and the control complexity is reduced;
(2) The method adopts a control winding current directional control strategy for grid connection, provides a scheme for expanding the rotation control reactive power of a coordinate system, and provides a new idea for control.
In order to further explain the grid-connected power control method of the brushless doubly-fed motor provided by the embodiment of the invention, the following is described in detail by combining with a specific example:
embodiment one:
the following takes a brushless doubly-fed motor with a 32kW wound rotor structure in a power generation mode as an example, and the implementation of the present invention will be further described with reference to fig. 1 to 8.
The brushless doubly-fed motor is a nonlinear, strongly coupled, multivariable system, and for simplicity of analysis, only the effect of the brushless doubly-fed motor air-gap fundamental magnetic field is generally considered, and the following assumptions are made: (1) The influence of tooth grooves of a stator and a rotor is not considered, the inner surface of the stator and the outer surface of the rotor are smooth, and the air gap is uniform; (2) Irrespective of the influence of saturation, hysteresis and eddy current of ferromagnetic materials, linearizing parameters; (3) 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.
When the brushless doubly-fed motor adopts the generator convention, the mathematical model of the brushless doubly-fed motor under the double synchronous rotation dq coordinate system can be obtained according to the coordinate transformation relation. Wherein, the voltage equation is:
Wherein: u pd、upq、ucd、ucq is the dq axis voltage component of the power winding and the control winding respectively; i pd、ipq、icd、icq、ird、irq is the dq axis current component of the power winding, the control winding and the rotor winding respectively; psi pd、Ψpq、Ψcd、Ψcq、Ψrd、Ψrq is the dq axis flux linkage component of the power winding, the control winding and the rotor winding respectively; r sp、Rsc、Rr is the single-phase resistance value of the power winding, the control winding and the rotor winding respectively; omega p is the power winding electric quantity angular frequency; omega m is the mechanical angular frequency of the rotor; p p、pc is the pole pair number of the power winding and the control winding respectively; s is the Laplace operator.
The flux linkage equation is:
Wherein: l sp、Lsc、Lr is the single-phase self-inductance value of the power winding, the control winding and the rotor winding respectively; m pr、Mcr is the single-phase mutual inductance value of the power winding and the rotor winding, and the control winding and the rotor winding respectively.
The electromagnetic torque equation is:
In the mathematical model of the double synchronous coordinate system, the dq coordinate system of the power winding, the control winding and the rotor winding rotates in space at the electric angular velocity of omega p、(pp+pc)Ωm﹣ωp、ωp﹣ppΩm respectively.
According to the mathematical model of the brushless doubly-fed motor, a mathematical relationship exists between the individual electric quantities. Under the simple closed loop control of the current of the control winding, after independent no-load or on-load starting, the electric quantity steady-state value of the sampling system is utilized in the synchronous grid-connection stage, the motor rotating speed is sampled instantaneously, the sagging coefficient is calculated, and the simple mathematical calculation is combined, so that the instantaneous sagging control of the brushless doubly-fed motor under the independent/grid-connection operation working condition is realized. The implementation process comprises the following steps:
as shown in the principle of fig. 2, the control winding current dq component in the unified reference dq coordinate system is obtained.
(1) The mechanical angular speed omega m of the motor rotor is obtained by installing a code wheel on the rotor;
(2) Calculating the current angular frequency omega c of the control winding according to the pole pair number p p of the power winding, the pole pair number p c of the control winding, the current angular frequency omega p of the power winding and the mechanical angular speed omega m of the rotor:
ωc＝(pp+pc)Ωm-ωp……(25)
(3) Inputting the calculated omega c into an integration link to obtain an angle theta c, wherein s is a Laplacian:
(4) Detecting three-phase currents of the control winding, for example, i ca、icb、icc, converting the current of the control winding from a static abc coordinate to a unified reference dq coordinate system by Park coordinate conversion with theta c as a coordinate conversion angle to obtain i cd、icq:
As shown in the principle of fig. 3, the voltage and current dq components of the power winding under the unified reference dq coordinate system are obtained.
(5) A code disc is arranged on a rotor of the brushless doubly-fed motor, and a rotor position angle theta r is obtained;
(6) Combining the power winding pole pair number p p, the control winding pole pair number p c, the theta c in the step (1) and the rotor position angle theta r, and calculating to obtain an angle theta p：θp＝(pp+pc)θr-θc … … (28)
(7) Detecting the three-phase line voltage of the power winding, such as u pab、upbc、upca, and converting the three-phase line voltage into phase voltage u pa、upb、upc; using theta p as a coordinate transformation angle, converting the power winding voltage from a static abc coordinate to a unified reference dq coordinate system through Park coordinate transformation to obtain a component u pd、upq:
(8) Detecting three-phase currents of a power winding, such as i pa、ipb、ipc; using theta p as 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 component i pd、ipq:
As shown in fig. 4, the power winding voltage, current d, q quantities are obtained for the control winding current orientation.
(9) Detecting the three-phase line voltage of the power winding, converting the three-phase line voltage into phase voltage u pa、upb、upc if u pab、upbc、upca is detected, and taking the electric quantity u α p、uβ p of a two-phase static coordinate system;
(10) Detecting three-phase currents of the power winding, for example, i pa、ipb、ipc, and taking the electric quantity i α p、iβ p of a two-phase static coordinate system;
(11) And obtaining the electric quantity relation of the motor under the unified dq coordinate system:
/>
in the above formula, Z a、Zb is a motor parameter, and is assumed to be a known quantity.
(12) Because the control winding current is forced to be oriented, i.e. i q c =0, the control winding current amplitude is measured, and then the power winding electric quantity is jointly obtained, and the angle of the power winding electric quantity is transformed into the control winding current orientation coordinate system is as follows:
In the above
(13) Carrying the sine and cosine obtained in the step (12) into the steps (32) and (33) to obtain the power winding voltage current d and q values u d p、uq p、id p、iq p with the control winding current oriented;
As shown in fig. 9, a closed loop control system required for the brushless doubly-fed motor power generation system is built.
(14) Calculating the voltage, the current d and the Q components u d p、uq p、id p、iq p of the power winding obtained in the step (13) to obtain the active power P s and the reactive power Q s of the system output;
(15) The active power variation formula is as follows:
Recording the current variation delta I c c_amp of the control winding obtained by the active power variation as delta I c c1;
(16) The active power P s is compared with a given reference value P * s to obtain a difference value (P s *﹣Ps) and is input into a d-axis PI controller, and the d-axis PI controller output delta I c c2 is obtained according to experience K P＝1KI =25 … … (37);
(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 i cq *;
(18) The active power variation formula is as follows:
The angle change of the control winding obtained by the reactive power change is recorded as delta theta c1;
(19) The active power Q s is compared with a given reference value Q * s to obtain a difference value (Q s *﹣Qs) which is input into a PI controller, and the output value delta theta c2 of the transformation angle of the control winding is obtained according to experience K P＝0.25KI =0.006 … … (39);
(20) Adding the control winding angle change values obtained in the step (18) and the step (19) to obtain a control winding angle change value delta theta c;
(21) According to design experience, the proportional coefficient K pd、Kpq and the integral coefficient K id、Kiq of the d-axis PI controller and the q-axis PI controller are respectively: k pq＝Kpd＝3Kiq＝Kid =75: 75 … … (40)
(22) Comparing the d-axis component i cd of the control winding current with a reference value i cd * to obtain a difference value (i cd *﹣icd) and inputting the difference value into a d-axis PI controller to obtain d-axis PI controller output PI d:
Comparing the q-axis component i cq of the control winding current with a reference value i cq * to obtain a difference value (i cq *﹣icq) and inputting the difference value into a q-axis PI controller to obtain a q-axis PI controller output PI q:
(23) The control winding coordinate transformation reference value theta * c obtained in the step (20) is as follows:
(24) By inverse transformation of theta * c and Park Three-phase reference value u ca *、ucb *、ucc * of control winding voltage is obtained:
Sending u ca *、ucb *、ucc * into an SVPWM module to obtain a switch driving signal of a machine side converter, driving the converter by the signal to obtain a corresponding control winding three-phase voltage u ca、ucb、ucc, and applying the voltage to a control winding of the brushless doubly-fed motor to realize closed-loop control of control winding current;
(25) The current of the control winding is controlled to be in grid connection under the condition of the brushless double-fed motor power generation operation, and a set of control frames can be used for independent/grid connection to complete system control.
Detailed description of the preferred embodiments
Motor parameters and experimental waveforms for this example are given below in conjunction with fig. 10-13. The example consists of a wound rotor brushless doubly-fed motor, a load, a power grid, a back-to-back power electronic converter and a controller using the method of the invention.
The brushless doubly-fed motor was operated at 400 rpm and grid connection was controlled by the control method described above.
Fig. 10 shows the active and reactive jump waveforms during the grid connection control of the brushless doubly-fed motor, and fig. 11 shows the steady-state operation waveforms of the brushless doubly-fed motor system, so that the output current waveforms have better sine degree under the control scheme, and the grid connection requirement is met;
As shown in fig. 12, the power control active power jump waveform after the brushless doubly fed motor is in grid-connected operation; fig. 13 is a reactive power jump waveform. As can be seen from the figure, the q-axis of the system control winding current remains zero all the time, completing the orientation. The control winding changes the angle and jumps in order to meet the reactive power requirement when the reactive power jumps. The invention does not change the whole control architecture of the system during independent/grid-connected operation, thereby ensuring the uniformity of the system.
In summary, the grid-connected control method can use a set of directional control structure under independent/grid connection, simplifies a system switching control algorithm, effectively improves the safety and stability of the system, and has great flexibility and adaptability.
What is not described in detail in this specification is prior art known to those skilled in 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 characteristics 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 (5)
1. A power control method of a brushless doubly-fed motor, comprising the steps of:
S1, detecting three-phase current of a control winding and performing abc/dq coordinate transformation on the three-phase current to obtain a d-axis component i cd and a q-axis component i cq of the control winding current;
Detecting three-phase current of the power winding and performing abc/dq coordinate transformation on the three-phase current to obtain a d-axis component i pd and a q-axis component i pq of the current of the power winding;
Detecting the three-phase line voltage of the power winding, converting the three-phase line voltage into phase voltage, and obtaining a d-axis component u pd and a q-axis component u pq of the power winding after abc/dq coordinate transformation of the phase voltage;
S2, transforming the d-axis component i pd and the q-axis component i pq of the power winding current and the d-axis component u pd and the q-axis component u pq of the power winding voltage to the control winding current orientation i cq =0 through the internal relation of the motor to obtain the d-axis component of the power winding voltage under the control winding coordinate system Q-axis component/>Power winding current d-axis component i d p, q-axis component/>
S3, carrying out grid-connected system power calculation based on a brushless doubly-fed motor equivalent circuit, and controlling power winding voltage under a winding coordinate system after S2 conversionAnd power winding current i d p,/>Calculating to obtain expressions of output active power P s and reactive power Q s;
S4, converting the output power P s、Qs expression obtained in the S3 into a form of a control winding current vector i c and a power winding flux linkage vector ψ p through the internal relation of the brushless doubly fed motor;
S5, based on control winding current orientation, a small signal mode is applied, and the relation DeltaI c between the active power variation DeltaP and the control winding current amplitude variation is solved specifically and is used as the current inner ring d-axis input;
meanwhile, the relation between the active power variation delta Q and the control winding current angle variation delta theta c is solved specifically, and the relation is used as a control winding angle transformation increment value;
S6, obtaining a power control relation of the brushless doubly-fed motor under the control of the current orientation of the winding through steps S1-S5, wherein the current amplitude I c of the control winding is used for controlling the system to output active power, and the transformation angle theta c is used for controlling the system to output reactive power;
The step S2 includes:
S2-1, obtaining the mechanical angular velocity omega m of the motor rotor by installing a code wheel on the rotor;
S2-2, obtaining a control winding current angular frequency omega c according to the power winding pole pair number p p, the control winding pole pair number p c, the current angular frequency omega p of the power winding and the mechanical angular speed omega m of the rotor:
S2-3, inputting the angular frequency omega c of the control winding current into an integration link to obtain the angle of the control winding current, and transforming the angle to an angle theta c required by a unified reference dq coordinate system;
S2-4, detecting a control winding three-phase current i ca、icb、icc, taking theta c as a coordinate transformation angle, and obtaining a control winding current d-axis component i cd and a q-axis component i cq after converting the control winding current from a static abc coordinate to a unified reference dq coordinate system through Park coordinate transformation:
S2-5, obtaining a transformation angle theta p used for transforming the power winding current from a static abc coordinate to a unified reference dq coordinate system according to the transformation angle theta c of the control winding coordinate and the rotor position angle theta r in the step S2-3;
s2-6, detecting a three-phase current i pa、ipb、ipc of the power winding, taking theta p as a coordinate transformation angle, and converting the power 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 pd and a q-axis component i pq of the power winding current:
S2-7, converting detected three-phase line voltage u pab、upbc、upca of the power winding into phase voltage u pa、upb、upc, using theta p as a coordinate transformation angle, and converting the current of the power winding from a static ABC coordinate to a unified reference dq coordinate system through Park coordinate transformation to obtain d-axis component u pd and q-axis component u pq of the voltage of the power winding;
S2-8, transforming the power winding current i pd、ipq in the steps S2-6 and S2-7, and the voltage u pd、upq to the lower components of the control winding current directional coordinate system through the internal model relation of the motor to be respectively
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:
Wherein, ψ c p、uc p、ic c are the power winding voltage flux linkage vector, voltage vector and control winding current amplitude under control winding current orientation; r p、rr is the impedance of the power winding and the rotor winding, and L sp、Lr is the self-inductance of the power winding and the rotor winding; m pr、Mcr is the mutual inductance between the power winding and the rotor winding, and between the control winding voltage and the rotor winding; omega p、ωsr respectively power winding angular frequency and slip frequency; s is a differential operator; j is a complex operator;
s3-2, the same way, the power winding current is expressed as a power winding flux linkage and a control winding current form according to a motor model:
wherein the parameters are consistent with step S3-1;
S3-3, obtaining a system power expression by using the power winding voltage and the power winding current obtained in the steps S3-1 and S3-2:
Wherein S is apparent power, and P s、Qs respectively represents active power and reactive power of the system;
S3-4, under the control of winding current orientation, based on a phase angle control thought, the active power P s and the reactive power Q s of the system are expressed as:
Wherein |ψ c p|、|Ic c | represents the power winding flux linkage amplitude and the control winding current amplitude, respectively; θ is the included angle between the flux linkage of the power winding and the current of the control winding under the current coordinate system of the control winding;
The step S4 includes:
S4-1, the active power variation delta P s and the reactive power variation delta Q s are respectively as follows:
Wherein I c c_ini is the initial value of the current amplitude of the control winding, I c' c_fin is the final value of the current of the control winding, delta theta is the angle variation of the control winding, and the rest parameters are consistent with those in the step S3-2;
S4-2, relative to the control winding current amplitude I c, when the angle change is small, consider:
cosΔθ≈1,sinΔθ≈Δθ；
S4-3, arranging the power variation expression in S4-1 according to the steps, and finally expressing as follows:
Wherein Δic c_amp is the variation caused by controlling the current amplitude of the winding, and Δic c_ang is the variation caused by controlling the angle of the winding;
The step S5 includes:
S5-1, analyzing the active power control of the system according to the step S4 to obtain a control equation:
Wherein the method comprises the steps of The control of the active power of the system is realized according to the relation;
S5-2, recording the change quantity of the control winding caused by the change quantity of active power in the step S5-1 as delta I c1;
s5-3, analyzing reactive power control of the system by using a small signal analysis tool to obtain a specific control equation:
Wherein Q s is a reactive power given value, and the reactive power of the system is controlled according to the relation;
s5-4, recording the angle change quantity of the control winding obtained from the reactive power change quantity in the step S5-3 as: Δθ c1.
2. The power control method of a brushless doubly-fed motor as claimed in claim 1, wherein said step S6 includes:
S6-1, designing a power outer loop controller according to the step S5, and setting the values K Pq＝KPd KIq＝KId of the proportional coefficient K Pq and the integral coefficient K Iq of an outer loop d-axis PI controller, wherein the proportional coefficient K Pd and the integral coefficient K Id of the d-axis PI controller are obtained empirically;
s6-2, the active power outer loop reference value Difference from the actual value P s/>Inputting the PI controller to obtain the output of the PI controller as delta I c2;
S6-3, adding the control winding current amplitude variation delta I c1 obtained in the step S5-2 and the control winding current amplitude output delta I c2 obtained in the step S6-2 to obtain a control winding current inner ring d-axis given value I c d*;
s6-4, the reactive power outer loop reference value Difference from the actual value Q s/>The input PI controller obtains the output of the PI controller as delta theta c2;
s6-5, adding the control winding angle change quantity delta theta c1 obtained in the step S5-4 and the control winding angle output quantity delta theta c2 obtained in the step S6-4 to obtain the total control winding angle change quantity as follows: Δθ c;
S6-6, superposing the angle change quantity delta theta c obtained in the step S6-5 to a control winding transformation angle theta c to obtain a transformation angle reference value which is:
3. The power control method of a brushless doubly-fed motor as claimed in claim 2 further comprising step S7; the step S7 includes:
s7-1, an inner ring expression of the motor is obtained by a motor mathematical model:
Wherein the method comprises the steps of
S7-2, multiplying the electric quantity obtained in the step S2 by motor parameters to obtain the compensation quantity;
s7-3, superposing the obtained d-axis q-axis compensation quantity to the current inner loop output, so that feedforward compensation is completed, and the system influence speed is improved.
4. The power control method of a brushless doubly-fed motor as claimed in claim 3 further comprising step S8; the step S8 includes:
S8-1, setting a value K pq＝Kpd Kiq＝Kid of a proportional coefficient K pq and an integral coefficient K iq of the q-axis PI controller, wherein the proportional coefficient K pd and the integral coefficient K id of the d-axis PI controller are obtained empirically;
S8-2, controlling the d-axis reference value of the winding current And d component/>Difference/>The input d-axis PI controller obtains the output PI d of the d-axis controller; control winding current q-axis reference value/>And q-axis component/>Difference/>The input q-axis PI controller obtains an output PI q of the q-axis controller;
S8-3, obtaining a specific expression of a system current inner loop according to a dq mathematical model in the brushless doubly-fed motor:
wherein R sc、Lsc is single-phase resistance and inductance of the brushless doubly-fed motor control winding, and K 1、K2 and K 3 are equivalent parameters obtained after series connection and parallel connection of motor inductances;
S8-4, controlling the winding current angle theta * c in the step S6-6 And obtaining a three-phase reference value u ca *、ucb *、ucc * of the control winding voltage after Park inverse transformation, and sending the three-phase reference value u ca *、ucb *、ucc * to 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 closed-loop control of the control winding current of the brushless double-fed motor.
5. The method of power control of a brushless doubly-fed machine according to claim 4 wherein said control winding voltage three-phase reference u ca *、ucb *、ucc * is:
Wherein, The d-axis component and the q-axis component of the control winding voltage obtained in step S8 are respectively, and θ * c is the control winding angle obtained in step S6.
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| CN109412478A (en) * | 2018-09-21 | 2019-03-01 | 华中科技大学 | A kind of power droop control method of brushless dual-feed motor |
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| CN109412478A (en) * | 2018-09-21 | 2019-03-01 | 华中科技大学 | A kind of power droop control method of brushless dual-feed motor |
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