CN113422551A - Switched reluctance motor speed control system with power factor correction - Google Patents
Switched reluctance motor speed control system with power factor correction Download PDFInfo
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- CN113422551A CN113422551A CN202110597745.0A CN202110597745A CN113422551A CN 113422551 A CN113422551 A CN 113422551A CN 202110597745 A CN202110597745 A CN 202110597745A CN 113422551 A CN113422551 A CN 113422551A
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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
- H02P21/12—Stator flux based control involving the use of rotor position or rotor speed sensors
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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
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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
- H02P25/00—Arrangements or methods for the control of AC motors characterised by the kind of AC motor or by structural details
- H02P25/02—Arrangements or methods for the control of AC motors characterised by the kind of AC motor or by structural details characterised by the kind of motor
- H02P25/08—Reluctance motors
- H02P25/0805—Reluctance motors whereby the speed is regulated by measuring the motor speed and comparing it with a given physical value
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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
- H02P27/00—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage
- H02P27/04—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage
- H02P27/06—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage using dc to ac converters or inverters
- H02P27/08—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage using dc to ac converters or inverters with pulse width modulation
- H02P27/085—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage using dc to ac converters or inverters with pulse width modulation wherein the PWM mode is adapted on the running conditions of the motor, e.g. the switching frequency
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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
- H02P27/00—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage
- H02P27/04—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage
- H02P27/06—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage using dc to ac converters or inverters
- H02P27/08—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage using dc to ac converters or inverters with pulse width modulation
- H02P27/12—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage using dc to ac converters or inverters with pulse width modulation pulsing by guiding the flux vector, current vector or voltage vector on a circle or a closed curve, e.g. for direct torque control
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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
- H02P2207/00—Indexing scheme relating to controlling arrangements characterised by the type of motor
- H02P2207/05—Synchronous machines, e.g. with permanent magnets or DC excitation
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Abstract
The invention discloses a speed control system of a switched reluctance motor with power factor correction, which consists of a three-phase alternating current module, a two-level voltage source inverter, a conduction pulse correction module, a drive control module with overcurrent protection, a dead-beat prediction direct power control system, a reference speed setting module and an asymmetric Space Vector Pulse Width Modulation (SVPWM) module, wherein the conduction pulse correction module capable of correcting conduction pulses is adopted under the condition of considering the motor performance and the interference on external speed control, the drive control module with overcurrent protection is combined to improve the power factor and the electric energy quality, an expected voltage vector is synthesized by the asymmetric SVPWM method to reduce the switching frequency, the control complexity of the system is reduced by connecting the two-level voltage source inverter and an asymmetric half-bridge converter in series, meanwhile, the dead-beat prediction direct power control is utilized to realize stable and enhanced direct current bus voltage, fast speed regulation is ensured by bi-directionally manipulating the energy flow in a two-level voltage source inverter.
Description
Technical Field
The invention belongs to the technical field of motor control application, and particularly relates to a speed control system of a switched reluctance motor, which is used for adjusting the speed of the switched reluctance motor.
Background
Most of the existing vehicle motors are induction motors and permanent magnet motors, and the induction motors have poor speed regulation performance, are difficult to accurately control and have high requirements on a control system of the motors; for a permanent magnet motor, stability under high temperature and high magnetic field environment is difficult to guarantee due to the existence of permanent magnet materials. The switched reluctance motor is a vehicle motor quickly because the switched reluctance motor does not need rare earth permanent magnets, has low cost and high reliability and outputs direct current voltage. Because the switched reluctance motor and other loads for vehicles need direct current input, alternating current generated by a generator and an alternating current network needs to be rectified by a rectifier, however, a conventional diode rectifier often reduces power factor and electric energy quality, which reduces energy conversion efficiency and even brings potential threats to electric equipment. In response to this problem, a conventional method is to add a power factor correction front-end circuit to improve the power factor, however, in this method, the total harmonic distortion of the current and the quality of the electric energy are still not ideal, and the control complexity of the system is increased.
Disclosure of Invention
The invention aims to overcome the defects of power factor and electric energy quality reduction when alternating current generated by a generator and an alternating current power grid is rectified, and provides a speed control system of a switched reluctance motor powered by a two-level voltage source inverter with power factor correction.
The technical scheme adopted by the invention comprises the following steps:the invention consists of a three-phase alternating current module, a two-level voltage source inverter, a conduction pulse correction module, a drive control module with overcurrent protection, a dead-beat prediction direct power control system, a reference speed setting module and an asymmetric Space Vector Pulse Width Modulation (SVPWM) module, and is connected with a switched reluctance motor system comprising a switched reluctance motor, wherein the three-phase alternating current module outputs three-phase alternating current voltage ea,eb,ecAnd current ia,ib,icThree-phase AC voltage ea,eb,ecInput to a two-level voltage source inverter, three-phase AC voltage ea,eb,ecAnd current ia,ib,icThe two-level voltage source inverter outputs a DC bus voltage U which is commonly input into a dead-beat prediction direct power control systemdcTo the switched reluctance motor system, the outputs of the switched reluctance motor system are a position angle θ, a velocity ω, and a phase current imThe output end of the switched reluctance motor system is respectively connected with the input ends of the conduction pulse correction module, the drive control module with overcurrent protection and the dead-beat prediction direct power control system, the speed omega is respectively input into the conduction pulse correction module and the dead-beat prediction direct power control system, and the position angle theta and the phase current imThe current-carrying current-carrying'on，θ’offCorrected on pulse θ'on，θ’offInputting the input signal into a drive control module with overcurrent protection, and outputting a switch drive signal S by the drive control module with overcurrent protectioniTo a switched reluctance motor system; the reference speed omega output by the reference speed given module is input into the dead-beat prediction direct power control system, and the output of the dead-beat prediction direct power control system is a voltage vector uα,uβThe output end of the dead-beat prediction direct power control system is sequentially connected with the asymmetric SVPWM module and the two-level voltage source inverter, and the output end of the dead-beat prediction direct power control system isVoltage vector uα,uβVoltage vector uα,uβThe switching signal S is input into an asymmetric SVPWM module which outputsjThe switching signal SjThe voltage is input into a two-level voltage source inverter.
The invention has the advantages that:
1. the invention adopts the conduction pulse correction module capable of correcting the conduction pulse and combines with the drive control module with the overcurrent protection under the condition of considering the motor performance and the interference on the external speed control, thereby improving the current curve and improving the power factor and the electric energy quality.
2. The invention controls the speed of the switched reluctance motor by adjusting the active power of the front end, thereby eliminating a direct current bus voltage control loop, effectively simplifying the whole control scheme and realizing the stepless adjustment and power factor correction of the direct current bus voltage.
3. The invention utilizes the characteristic that the rotating speed of the motor can be directly controlled by controlling the voltage of the direct current bus in the switched reluctance motor, not only can realize stable and enhanced direct current bus voltage, but also can ensure rapid speed regulation by bidirectionally operating the energy flow in the two-level voltage source inverter.
4. The power tracking reference value is obtained by dead-beat prediction direct power control, and the accuracy of system control is ensured.
5. The invention adopts the improved asymmetric SVPWM, synthesizes the expected voltage vector obtained from the dead-beat prediction direct power control system by the asymmetric SVPWM method, can reduce the switching frequency and reduce the switching loss.
6. The invention fully considers the power factor correction, the electric energy quality and the control complexity of the system, the system reduces the control complexity of the system by connecting the two-level voltage source inverter and the asymmetric half-bridge converter in series, simultaneously utilizes dead beat prediction to directly control the power, not only can realize stable and enhanced direct current bus voltage, but also can ensure quick speed regulation by bidirectionally operating the energy flow in the two-level voltage source inverter, and in addition, because of improving the current curve, the system power factor and the electric energy quality are also improved.
Drawings
FIG. 1 is a block diagram illustrating the structure and control of a switched reluctance motor speed control system with power factor correction according to the present invention;
FIG. 2 is a block diagram of the components of the switched reluctance motor system 10 of FIG. 1;
fig. 3 is a block diagram of the two-level voltage source inverter 20 of fig. 1;
FIG. 4 is a graph of conduction angle versus speed for the conduction pulse modification module 23 of FIG. 1;
fig. 5 is a block diagram of the drive control module 30 with overcurrent protection in fig. 1;
FIG. 6 is a block diagram of the components of the deadbeat prediction direct power control system 50 of FIG. 1 and a connection diagram to a reference speed setter 55, a three-phase AC power module 56;
fig. 7 is a diagram of base vectors and sector divisions in a conventional SVPWM.
In the figure: 10. a switched reluctance motor system; 11. a switched reluctance motor; 12. a position detection module; 13. a speed calculation module; 14. a current detection module; 15. an asymmetric half-bridge converter; 20. a two-level voltage source inverter; 23. a conduction pulse correction module; 30. the drive control module is provided with overcurrent protection; 31. a logic judgment module; 32. an overcurrent protection module; 33. a logical AND module; 50. a deadbeat prediction direct power control system; a Clarke variation module; 52. an instantaneous power calculation module; 53. a dead beat prediction direct power control module; a PI speed controller; 55. a reference speed setting module; 56. a three-phase alternating current module; 60. and the asymmetric SVPWM module.
Detailed Description
As shown in fig. 1 and fig. 2, the present invention comprises a three-phase ac module 56, a two-level voltage source inverter 20, a conduction pulse correction module 23, a drive control module 30 with overcurrent protection, a dead-beat prediction direct power control system 50, a reference speed setting module 55, and an asymmetric SVPWM module 60, and is connected to a switched reluctance motor system 10 including a switched reluctance motor 11, and the switched reluctance motor system is connected to the switched reluctance motor systemThe switched reluctance motor 11 in 10 is controlled. Wherein, the three-phase AC module 56 is connected to an external power supply to output a three-phase AC voltage ea,eb,ecAnd current ia,ib,icThe output end of the three-phase alternating current module 56 is respectively connected with the two-level voltage source inverter 20 and the dead-beat prediction direct power control system 50 to convert the three-phase alternating current voltage ea,eb,ecIs inputted to a two-level voltage source inverter 20 to convert the three-phase AC voltage ea,eb,ecAnd current ia,ib,icAre commonly input to a deadbeat prediction direct power control system 50. The two-level voltage source inverter 20 outputs a dc bus voltage UdcThe output end of the switch reluctance motor system 10 is connected with the input end of the switch reluctance motor system, and the direct current bus voltage U is applieddcIs input to the switched reluctance motor system 10 as a first input to the switched reluctance motor system 10. The second input of the switched reluctance motor system 10 is a switch drive signal S input by the drive control module with overcurrent protection 30iThe outputs of the switched reluctance motor system 10 are the position angle θ, the velocity ω, and the phase current im。
The output end of the switched reluctance motor system 10 is respectively connected with the input ends of the conduction pulse correction module 23, the drive control module 30 with overcurrent protection and the dead-beat prediction direct power control system 50, wherein the speed omega is respectively input into the conduction pulse correction module 23 and the dead-beat prediction direct power control system 50, the position angle theta and the phase current imAre commonly input to the drive control module 30 with overcurrent protection. The output end of the conduction pulse correction module 23 is sequentially connected with the overcurrent protection driving control module 30 and the switched reluctance motor system 10, and the conduction pulse correction module 23 outputs the corrected conduction pulse theta'on，θ’offAnd the corrected ON pulse θ'on，θ’offThe input signal is inputted into the drive control module 30 with overcurrent protection, and the drive control module 30 with overcurrent protection outputs a switch drive signal SiInto the switched reluctance motor system 10.
The output of the reference velocity setting module 55 is connected to the dead beat predictionThe input end of the direct power control system 50, the reference speed omega output by the reference speed setting module 55 is input into the dead-beat prediction direct power control system 50, and the dead-beat prediction direct power control system 50 outputs a voltage vector uα,uβ. The output end of the dead-beat prediction direct power control system 50 is sequentially connected with the asymmetric SVPWM module 60 and the two-level voltage source inverter 20, and the voltage vector uα,uβThe input signal is an asymmetric SVPWM module 60, and the output signal of the asymmetric SVPWM module 60 is a switching signal SjThe switching signal SjIs input to a two-level voltage source inverter 20.
As shown in fig. 2, the switched reluctance motor system 10 is composed of a switched reluctance motor 11, a position detection module 12, a speed calculation module 13, a current detection module 14, and an asymmetric half-bridge converter 15. Switched reluctance motor system 10 uses dc bus voltage UdcSwitching drive signal SiFor input, the position angle theta, the speed omega and the phase current imIs the output. The output end of the asymmetric half-bridge converter 15 is respectively connected with the input ends of the switched reluctance motor 11 and the current detection module 14, the output end of the switched reluctance motor 11 is connected with the speed calculation module 13 and the direct current bus voltage U through the position detection module 12dcAnd a switch drive signal SiInput to an asymmetric half-bridge converter 15, a switch drive signal SiIs a square wave driving signal with a voltage of 15V, which is used for controlling the on-off of the power switch device of the corresponding phase in the asymmetric half-bridge converter 15 to realize the on-off of each phase, thereby providing a direct current bus voltage U provided by the outsidedcApplied to the windings of the conducting phases, energises the phase windings to cause the switched reluctance motor 11 to rotate. The position detection module 12 outputs a position angle θ signal using a position sensor mounted on the motor. The velocity calculation module 13 calculates the velocity ω using the position angle θ signal output from the position detection module 12. Current detection module 14 outputs phase current i using a current sensor connected in series with the power converter circuitmA signal.
As shown in FIG. 3, the two-level voltage source inverter 20 is used for voltage stabilization rectification and power factor correction, and is composed of a filter resistor RgFilter inductor Lg6 IGBT switchesPipe Sa1，Sa2，Sb1，Sb2，Sc1，Sc2And a filter capacitor CdcOf three-phase AC voltage ea，eb，ecAnd switching signal S of IGBT switching tubejThe output is DC bus voltage UdcThe output end is connected with the input end of the switched reluctance motor system 10 in series and the DC bus voltage UdcAs a first input to the switched reluctance motor system 10. Three-phase alternating voltage e can be supplied by means of a two-level voltage source inverter 20a，eb，ecConverting into DC bus voltage Udc. Filter resistor RgAnd a filter inductance LgSeries, filter inductance LgAnd the emitter of the upper IGBT switch tube and the collector of the lower IGBT switch tube of the three phases a, b and c are respectively connected. The collector of the upper IGBT switch tube of the three phases a, b and c is connected with the positive end of the power supply, and the emitter of the lower IGBT switch tube is connected with the negative end of the power supply. The grid of the IGBT switching tube is controlled by the input switching signal Sj(j ═ a1, a2, b1, b2, c1, c 2). Filter capacitor CdcThe anode of the anode is connected with the positive end of the power supply, and the cathode of the anode is connected with the negative end of the power supply.
From the basic circuit of the switched reluctance motor 11, the voltage balance equation can be written as:
wherein, Um,，RmBus voltage and winding resistance of m phases respectively; magnetic linkage psim(imTheta) is with respect to phase current imAnd rotor position theta, and can use m-phase inductance Lm(imTheta) and phase current imRepresents the product of:
ψm＝ψm(im,θ)＝Lm(im,θ)im (2)
phase inductance L due to magnetic circuit saturation nonlinearity of the switched reluctance motor 11m(imTheta) also with the phase current imAnd rotor position theta. The belt of the formula (2)The following can be obtained in step (1):
as can be seen from equation (3), the phase voltage of the m-th phase is balanced with three voltage drops in the circuit, including a resistance drop (equation first term), a transformer electromotive force, i.e., an electromotive force induced by flux linkage change due to current change (equation second term), and a moving electromotive force, i.e., an electromotive force induced by flux linkage change in the winding due to rotor position change (equation third term). The transformer electromotive force is converted into energy stored in the magnetic field, and the motion electromotive force is converted into mechanical energy and output through a motor shaft. Before the maximum inductance zone, if a switch of one phase is closed at the same time, a part of magnetic field energy storage is converted into mechanical energy, and the rest of the magnetic field energy storage flows back to a bus capacitor in the demagnetization process to cause voltage fluctuation. Further, it can be found from the equation (3) that the dc bus voltage U applied to the m-phase is higher as the motor speed ω is higherm,＝UdcAnd when the current is constant, the slower the rate di/dt of the current increase, and correspondingly, the smaller the peak value of the current in a fixed time. Therefore, in order to quickly establish the current, it is necessary to make the conduction angle θ in the minimum inductance regiononIn advance, to improve the performance of the motor. That is, the conduction angle θonThe partial adjustment is based on the motor speed omega. Within a certain speed range, the larger the speed omega, the larger the conduction angle thetaonThe more advanced, i.e. thetaonThe smaller the value. As shown in fig. 4, through experiments on a four-phase switched reluctance motor, the conduction angle θ corresponding to the motor in a certain speed range and obtaining the best operation performance is obtainedonAngle of conduction thetaonThe relationship with the speed ω is shown in fig. 4. Obtaining the corresponding conduction angle theta at the best running performance under different speeds omegaonGenerating a look-up table module for determining the predefined conduction angle thetaonAngle of turn-off thetaoffAnd a speed omega to obtain a corrected on pulse theta'on，θ’offThis forms the on pulse correction module 23. As shown in fig. 1, of the on-pulse correction module 23Input as a preset conduction angle thetaonOff angle thetaoffAnd real-time motor speed ω 'and the output is a corrected on pulse θ'on，θ’off. Corrected on pulse θ'on，θ’offInput into the drive control module 30 with overcurrent protection. In the actual control, the off-angle θ is usually fixedoffFor conduction angle theta onlyonAnd (6) correcting.
As shown in fig. 5, the driving control module 30 with overcurrent protection is composed of a logic judgment module 31, an overcurrent protection module 32, and a logical and module 33. The input of the logic determination module 31 is the corrected on pulse θ 'output from the on pulse correction module 23'on，θ’offAnd the position angle theta output by the switched reluctance motor system 10, and the logic judgment module 31 inputs the conduction pulse theta'on，θ’offThe position angle theta is judged through logic and a square wave signal S is output1：
The input of the overcurrent protection module 32 is the phase current i output by the switched reluctance motor system 10mAnd a predefined maximum limit value i for the currentmaxThe overcurrent protection module 32 is used for comparing the phase current imAnd a maximum current limit value imaxOutputting square wave signal S by logic judgment2：
The output ends of the logic judgment module 31 and the overcurrent protection module 32 are both connected to the input end of the logic and module 33, and the logic and module 33 respectively outputs the square wave signal S according to the logic judgment module 31 and the overcurrent protection module 321，S2Outputs a switch driving signal S required by a power switch device in the switched reluctance motor system 10 through logic and judgmenti. Therefore, the drive control module 30 with overcurrent protection can be repairedOn pulse of just after θ'on，θ’offAngular position θ, phase current imAnd a predefined maximum limit i for the currentmaxFor inputting, outputting a switch driving signal Si。
As shown in fig. 6, the deadbeat predictive direct power control system 50 is comprised of a Clarke variation module 51, an instantaneous power calculation module 52, a deadbeat predictive direct power control module 53 and a PI speed controller 54. The output ends of the PI speed controller 54 and the Clarke change module 51 are respectively connected with the instantaneous power calculation module 52 and the dead beat prediction direct power control module 53.
In the switched reluctance motor 11, the motor speed can be directly controlled by controlling the dc bus voltage, so that the difference between the reference speed ω output from the reference speed setting module 55 and the speed ω output from the switched reluctance motor system 10 is input to the PI speed controller 54, the PI speed controller 54 outputs the reference active power P, and the reference active power P is input to the dead-beat prediction direct power control module 53 for speed regulation of the drive system. If delta omega is larger than zero, the direct current bus voltage U is increaseddcIncreasing P to increase the motor speed; otherwise, the DC bus voltage U is reduceddcTo decrease P to decrease the motor speed. In the control scheme of power factor correction, the reference reactive power Q is always zero. In order to track the reference power P, a dead-beat predictive direct power control method is employed.
Three-phase alternating voltage e output by three-phase alternating current module 56a,eb,ecAnd current ia,ib,icThe three-phase AC voltage e sampled from the three-phase AC module 56 is input to the Clarke variation module 51 by the Clarke variation module 51a,eb,ecAnd current ia,ib,icConverted into a voltage e in a two-phase stationary alpha beta coordinate systemα,eβAnd current iα,iβWherein the voltage eα,eβAnd current iα,iβInput to instantaneous power calculation module 52, voltage eα,eβInput to the homodyneBeat prediction direct power control module 53. The instantaneous power calculation module 52 obtains an instantaneous active power p and a reactive power q according to an instantaneous power theory:
wherein e isα,eβThe components of the AC voltage in the alpha and beta axes, iα,iβThe components of the alternating current in the alpha and beta axes, respectively.
The dynamic equations for the active power p and the reactive power q are established as follows:
wherein:
Emand w 2 pi f is the amplitude and angular frequency of the ac power source.
Establishing a mathematical model of the two-level voltage source inverter 20 in a two-phase stationary α β coordinate system:
wherein e isαβ,iαβ,uαβ,Rg,LgRespectively, alternating voltage, alternating current, rectified voltage, filter resistance and inductance.
Decomposing the formula (12) to obtain an alternating current iα,iβThe differential equation of (a) is as follows:
substituting equations (10) - (14) into equations (8), (9) to obtain the dynamic equations of the instantaneous active power p and the reactive power q as follows:
the heart of the deadbeat control is to calculate the required variable by assuming that the system achieves the desired behavior at the end of each control cycle, i.e. the instantaneous power at time k +1 equals the reference power at time k, i.e. pk+1＝P*，qk+1Q. Thus, by applying a forward Euler discretization to (15) and (16) at time k, calculating the voltage vector that brings the active and reactive powers at time k +1 to P and Q, we obtain:
wherein:
Tsfor the sampling period, filter resistance and inductance Rg,LgIs constant and typically takes 1-10k Ω and 1-10 mH.
Therefore, the dead-beat prediction direct power control module 53 inputs the instantaneous active power p and the reactive power q, and the component e of the alternating voltage on the alpha axis and the beta axisα,eβAnd the reference active power P and the reference reactive power Q can be output to track the voltage vector u of the reference power P and Qα,uβ. Thus, the input to the deadbeat prediction direct power control module 50 is the AC voltage e output by the three-phase AC power module 56a,eb,ecAnd current ia,ib,icThe reference speed ω output by the reference speed setting module 55 and the real-time speed ω output by the switched reluctance motor system 10 are output as voltage vectors u for tracking the reference powers P and Qα,uβ. The output end of the dead-beat prediction direct power control module 53 is connected with the asymmetric SVPWM module 60, and the voltage vector u is connected with the output end of the asymmetric SVPWM moduleα,uβInput to the asymmetric SVPWM module 60.
As shown in fig. 7, using a voltage vector uα,uβThe output is used for controlling an IGBT switching tube S in the two-level voltage source inverter 20a1，Sa2，Sb1，Sb2，Sc1，Sc2On-off switch signal Sj. In conventional SVPWM, u is calculated for synthesisα,uβIt should be decomposed into two adjacent basis vectors selected according to sector decision, the role of each basis vector being controlled by adjusting their dwell time. The 8 base voltage vectors and sector divisions are shown in fig. 7. Suppose desired uα,uβLocated in sector i, the switching sequence and assigned dwell time for each basis vector is shown in table 1 below:
TABLE 1
t0、t1、t2Representing the residence time of vectors u0, u1, u2, respectively. The switching sequence of the base vector of each sector is fixed and predefined for unnecessary switching operation of the IGBT switching tube. In the control period, the switching sequence starts and ends with a zero vector (000), so that the switching frequency of each IGBT switching tube is equal to the control frequency, and another zero vector (111) is applied in the middle of the control period. There are seven switching patterns during each control.
To reduce switching losses, the present invention employs a modulation method at half the switching frequency to synthesize the desired voltage vector u obtained from the dead-beat prediction direct power control module 50α,uβ. The various steps of the improved modulation method are the same as the conventional modulation method before the dwell time calculation of the basis vectors. Tables 2 and 3 below are switching sequences of the improved asymmetric SVPWM method when two consecutive desired vectors are located in the same sector and different sectors, respectively:
TABLE 2
TABLE 3
Unlike conventional SVPWM, the enhanced asymmetric SVPWM is only in one period TsWhere the selected basis vector is executed once. The switching sequence starts with one zero voltage vector (000) and ends with another zero voltage vector (111). In the following period TsIn the sequence, the start vector and the last period TsThe vectors implemented at the end are identical. The enhanced asymmetric SVPWM doubles the dwell time of the base vectors compared to the conventional SVPWM. Although the pulse excitation is in one control periodThe pulse excitation is asymmetric, but since the duty cycle does not vary much in two consecutive control periods, the pulse excitation is approximately symmetric in the two consecutive control periods. By adopting the modulation mode, the switching frequency can be reduced to 50 percent of the traditional modulation mode, and the switching frequency is reduced. This means that during a control period TsThe effect of the implementation of the inner required voltage vector may be equivalent to the effect of the implementation of several base vectors.
As shown in FIG. 1, during operation of the present invention, the three-phase AC voltage e output by the three-phase AC module 56a,eb,ecOutputting a stable DC bus voltage U by a two-level voltage source inverter 20dcDC bus voltage UdcAs an input of the switched reluctance motor system 10, an excitation voltage is supplied to the winding of the switched reluctance motor 11, thereby driving the switched reluctance motor 11 to rotate.
The conduction pulse correction module 23 of the invention can correct the conduction angle theta according to the motor speed omegaonThe current establishing speed is high, voltage fluctuation caused by demagnetization is reduced, and the best running performance of the motor is ensured; the drive control module 30 with overcurrent protection combines overcurrent protection and drive control to prevent the conduction angle theta from being affectedonAnd excessive exciting current is generated in advance, a current curve is improved, and the power factor and the electric energy quality are improved. The dead-beat prediction direct power control module 50 controls the speed omega of the switched reluctance motor 11 by adjusting the active power P at the front end, thereby eliminating a direct current bus voltage control loop, effectively simplifying the whole control scheme, realizing the stepless adjustment and the power factor correction of the direct current bus voltage, and simultaneously, outputting a voltage vector uα,uβThe energy flow in the two-level voltage source inverter 20 can be bi-directionally manipulated through the asymmetric SVPWM module 60 to achieve fast speed regulation. In addition, the dead-beat prediction direct power control module 53 calculates the required rectifier voltage vector using the power model derived in the stationary α β coordinate system without performing rotation transformation, reducing the control complexity of the system. The asymmetric SVPWM module 60 may reduce the switching frequency and reduce the switching losses.
The invention utilizes the characteristic that the rotating speed of the motor can be directly controlled by controlling the direct current bus voltage in the switched reluctance motor 11, not only can realize stable and enhanced direct current bus voltage, but also can ensure rapid speed regulation by bidirectionally operating the energy flow in the two-level voltage source inverter. The power tracking reference value is obtained by dead-beat prediction direct power control, and the accuracy of system control is ensured.
Claims (10)
1. A switched reluctance motor speed control system with power factor correction is characterized in that: the three-phase alternating current motor system consists of a three-phase alternating current module (56), a two-level voltage source inverter (20), a conduction pulse correction module (23), a drive control module (30) with overcurrent protection, a dead-beat prediction direct power control system (50), a reference speed setting module (55) and an asymmetric SVPWM module (60), and is connected with a switched reluctance motor system (10) comprising a switched reluctance motor (11), wherein the three-phase alternating current module (56) outputs a three-phase alternating current voltage ea,eb,ecAnd current ia,ib,icThree-phase AC voltage ea,eb,ecIs input to a two-level voltage source inverter (20) to generate a three-phase AC voltage ea,eb,ecAnd current ia,ib,icThe two-level voltage source inverter (20) outputs a direct current bus voltage U which is commonly input into a dead-beat prediction direct power control system (50)dcInto a switched reluctance motor system (10), the outputs of the switched reluctance motor system (10) are a position angle θ, a velocity ω, and a phase current imThe output end of the switched reluctance motor system (10) is respectively connected with the input ends of the conduction pulse correction module (23), the drive control module (30) with overcurrent protection and the dead-beat prediction direct power control system (50), the speed omega is respectively input into the conduction pulse correction module (23) and the dead-beat prediction direct power control system (50), and the position angle theta and the phase current imThe current signals are jointly input into a drive control module (30) with overcurrent protection, the output end of a conduction pulse correction module (23) is sequentially connected with the drive control module (30) with overcurrent protection and a switched reluctance motor system (10), and the output of the conduction pulse correction module (23) is correctedOn pulse of'on，θ’offCorrected on pulse θ'on，θ’offThe input signal is input into a drive control module (30) with overcurrent protection, and the drive control module (30) with overcurrent protection outputs a switch drive signal SiInto a switched reluctance motor system (10); the reference speed omega output by the reference speed setting module (55) is input into the dead-beat prediction direct power control system (50), and the dead-beat prediction direct power control system (50) outputs a voltage vector uα,uβThe output end of the dead-beat prediction direct power control system (50) is sequentially connected with an asymmetric SVPWM module (60) and a two-level voltage source inverter (20), and the output end of the dead-beat prediction direct power control system (50) is a voltage vector uα,uβVoltage vector uα,uβThe input is an asymmetric SVPWM module (60), and the output of the asymmetric SVPWM module (60) is a switching signal SjThe switching signal SjThe voltage is input to a two-level voltage source inverter (20).
2. The system of claim 1, wherein the switched reluctance motor speed control system comprises: the switched reluctance motor system (10) is composed of a switched reluctance motor (11), a position detection module (12), a speed calculation module (13), a current detection module (14) and an asymmetric half-bridge converter (15), wherein the output end of the asymmetric half-bridge converter (15) is respectively connected with the input ends of the switched reluctance motor (11) and the current detection module (14), the output end of the switched reluctance motor (11) is connected with the speed calculation module (13) through the position detection module (12), and the direct-current bus voltage U isdcAnd a switch drive signal SiInput to an asymmetric half-bridge converter (15), a switching drive signal SiThe voltage is a square wave driving signal with 15V, and the position detection module (12) outputs a position angle theta. The speed calculation module (13) outputs speed omega, and the current detection module (14) outputs phase current im。
3. The system of claim 1, wherein the switched reluctance motor speed control system comprises: two-level voltage source inverter(2) By a filter resistor RgFilter inductor Lg6 IGBT switch tubes Sa1，Sa2，Sb1，Sb2，Sc1，Sc2And a filter capacitor CdcComposition, filter resistance RgAnd a filter inductance LgSeries, filter inductance LgThe emitter of the upper IGBT switch tube of the three phases a, b and C is connected with the collector of the lower IGBT switch tube, the collector of the upper IGBT switch tube of the three phases a, b and C is connected with the positive end of the power supply, the emitter of the lower IGBT switch tube is connected with the negative end of the power supply, and the filter capacitor CdcThe anode of the anode is connected with the positive end of the power supply, and the cathode of the anode is connected with the negative end of the power supply.
4. The system of claim 1, wherein the switched reluctance motor speed control system comprises: obtaining the corresponding conduction angle theta at the best running performance under different speeds omegaonGenerating a look-up table module according to the predefined conduction angle thetaonOff angle thetaoffAnd the speed omega is corrected to obtain an on pulse theta'on，θ’off。
5. The system of claim 1, wherein the switched reluctance motor speed control system comprises: the drive control module (30) with overcurrent protection is composed of a logic judgment module (31), an overcurrent protection module (32) and a logical AND module (33), wherein the input of the logic judgment module (31) is a corrected conduction pulse theta'on，θ’offAnd an open position angle theta, outputting a square wave signal S1The input of the overcurrent protection module (32) is the phase current imAnd a predefined maximum limit value i for the currentmaxOutputting a square wave signal S2The output ends of the logic judgment module (31) and the overcurrent protection module (32) are both connected with the input end of the logic AND module (33), and the logic AND module (33) is used for generating a square wave signal S1，S2Making logic and judgment, and outputting switch driving signal Si。
6. The strip power factor correction of claim 1The speed control system of the switched reluctance motor is characterized in that: the dead beat prediction direct power control system (50) consists of a Clarke change module (51), an instantaneous power calculation module (52), a dead beat prediction direct power control module (53) and a PI speed controller (54), wherein the output ends of the PI speed controller (54) and the Clarke change module (51) are respectively connected with the instantaneous power calculation module (52) and the dead beat prediction direct power control module (53), a difference value delta omega of the difference between a reference speed omega and a speed omega is input into the PI speed controller (54), the PI speed controller (54) outputs a reference active power P to the dead beat prediction direct power control module (53), and three-phase alternating current voltage e isa,eb,ecAnd current ia,ib,icThe voltage is input into a Clarke change module (51), and the Clarke change module (51) outputs the voltage e under a two-phase static alpha beta coordinate systemα,eβAnd current iα,iβVoltage eα,eβAnd current iα,iβInput into an instantaneous power calculation module (52) and the voltage eα,eβThe input is input into a dead-beat prediction direct power control module (53), an instantaneous power calculation module (52) outputs an instantaneous active power p and a reactive power q to the dead-beat prediction direct power control module (53), and the dead-beat prediction direct power control module (53) outputs a voltage vector uα,uβ。
7. The system of claim 1, wherein the switched reluctance motor speed control system comprises: the switching sequence of the asymmetric SVPWM module (60) begins with one zero voltage vector, ends with another zero voltage vector, and follows a period TsIn the sequence, the start vector and the last period TsThe vectors implemented at the end are identical.
8. The system of claim 6, wherein the switched reluctance motor speed control system comprises: the instantaneous active power
Reactive power
eα,eβThe components of the AC voltage in the alpha and beta axes, iα,iβThe components of the alternating current in the alpha and beta axes, respectively.
9. The system of claim 8, wherein the switched reluctance motor speed control system comprises: voltage vector
γ1＝P*eα+Q*eβ，γ2＝Q*eα-P*eβ，
TsFor a sampling period, RgIs a filter resistance, LgIs a filter inductance.
10. The system of claim 5, wherein the switched reluctance motor speed control system comprises: the square wave signal
The square wave signal
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