CN114389486B - Commutation error compensation method for hybrid excitation doubly salient motor - Google Patents
Commutation error compensation method for hybrid excitation doubly salient motor Download PDFInfo
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- 238000004804 winding Methods 0.000 claims description 27
- 238000004364 calculation method Methods 0.000 claims description 2
- 230000010349 pulsation Effects 0.000 abstract description 4
- 230000010355 oscillation Effects 0.000 description 5
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Classifications
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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
- H02P6/00—Arrangements for controlling synchronous motors or other dynamo-electric motors using electronic commutation dependent on the rotor position; Electronic commutators therefor
- H02P6/14—Electronic commutators
- H02P6/15—Controlling commutation time
- H02P6/153—Controlling commutation time wherein the commutation is advanced from position signals phase in function of the speed
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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
- H02P25/086—Commutation
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- Control Of Electric Motors In General (AREA)
Abstract
The invention discloses a commutation error compensation method for a hybrid excitation doubly salient motor, and belongs to the technical field of variable reluctance motor drive control. The method for compensating the commutation error of the hybrid excitation doubly salient motor provided by the invention is realized according to the following principle: when the current commutation point arrives, the sampling point of the controller is coincident with the commutation point, and thus accurate commutation can be realized to eliminate the commutation error of the hybrid excitation doubly salient motor. According to the invention, the phase-change error of the hybrid excitation doubly salient motor can be effectively reduced by adjusting the switching frequency by a small amplitude, the accurate phase-change of the hybrid excitation doubly salient motor is realized, the current capacity of a switching tube can be effectively utilized, the torque pulsation is reduced, and the torque output capacity is improved.
Description
Technical Field
The invention belongs to the technical field of driving control of variable reluctance motors.
Background
The hybrid excitation double salient pole motor is used as a variable reluctance motor, a stator-rotor structure of double salient poles of the switched reluctance motor is reserved on the basis of the switched reluctance motor, and an additional excitation winding is introduced on a stator. Because the rotor is free of any winding and permanent magnet, the rotor has a simple and reliable structure and is naturally suitable for high-speed operation. However, at present, no mature high-speed control algorithm exists for the hybrid excitation doubly salient motor. In engineering practice, the advanced angle control or the three-phase nine-state control method is generally adopted to realize the high-speed operation of the hybrid excitation doubly salient motor. Both control methods need to perform three-phase current commutation, and whether accurate current commutation can be realized has great influence on the running performance of the motor.
Commutation errors are due to delays present in digital control systems. Errors are mainly divided into two categories: one is an error caused by PWM update delay, and the other is an error caused by angular position of discrete samples. The first type of error is inherent to PWM digital control systems, in which a digital processor counts the generated triangular wave as a carrier wave, which is interleaved with the modulated wave to generate a PWM drive signal. And when the digital processor enters an interrupt, the digital processor calculates the acquired signals. If updated immediately after the operation is completed, the PWM signal may be lost due to the excessive operation time. The update of the PWM signal will only take place when the processor enters the next interrupt, which causes a delay of one switching cycle. The second type of error is due to discrete sampling, ideally at infinite sampling frequency, and the signal collected is a continuous quantity. In practical cases, however, the sampling frequency of the controller is limited, and the acquired signals are discrete signals. The set commutation angle is a certain point, and due to the limitation of the sampling frequency, the system cannot accurately sample at the point, and the actual sampling point fluctuates around the set point. The sampling frequency is typically equal to the switching frequency, so a commutation error of 0-1 switching cycle occurs. The two errors are combined, and the total commutation error of the hybrid excitation doubly salient motor system is 1-2 switching cycles.
The switching frequency of the hybrid excitation doubly salient motor is far greater than the operating frequency of the motor under low-speed operation, so that the electric angle corresponding to one switching period is very small, and the phase-change error under the low-speed condition can be ignored. When the running speed of the motor is increased, the electric angle corresponding to one switching period cannot be ignored. If the carrier ratio is to be kept unchanged, a higher switching frequency is required, the device cost and the design difficulty are greatly increased, which is not practical. Commutation errors can only be eliminated by a method that does not increase the switching frequency.
Under high-speed operation, the three-phase current of the hybrid excitation doubly-salient motor has low-frequency oscillation due to the existence of phase-change errors, the width of a conduction interval of each period is different, and the amplitude of the current is also unequal. On the one hand, the low-frequency oscillation of the current amplitude can lead to corresponding pulsation of the motor torque; on the other hand, the oscillation of the current amplitude can lead to smaller current amplitude in certain periods and larger current amplitude in certain periods, and the current stress of the switching tube is selected according to the maximum current stress, so that the current capacity of the switching tube cannot be fully utilized. If the commutation error in the high-speed running state can be eliminated, the current amplitude oscillation can be eliminated, the capacity of the switching tube can be fully utilized, and the rotating speed can be further improved.
Disclosure of Invention
According to the hybrid excitation doubly salient phase-change error compensation method, the effect of eliminating the phase-change error is achieved by adjusting the switching frequency in a small amplitude under the condition that the circuit topology is not changed.
In order to achieve the above purpose, the method for compensating the commutation error of the hybrid excitation doubly salient motor comprises the following specific implementation steps:
step one: sampling a current rotor position angle theta through a rotary transformer coaxially installed with the motor, and judging whether the current rotor position angle theta is in a section in which a commutation angle is theta 1 The sampled position signal is theta and the switching frequency is f s Maximum switching frequency nf s The electrical frequency is f e One switching cycle corresponds to an electrical angle of theta d ＝f e *360/f s ：
(1)θ∈(θ 1 -θ d *2/n，θ 1 -θ d /n)
(2)θ∈(θ 1 -(1+1/n)*θ d ，θ 1 -θ d *2/n)
Step two: if none of the current rotor positions is in the above section, it is indicated that the current rotor position is far from the set commutation point, so that no operation is required at this time to maintain the original switching frequency f s The method is unchanged.
Step two: if the current rotor position is in the section described in (1), calculating the current position angle theta and the phase change angle theta 1 And the angle difference between the two is set to a proper switching frequency, so that the position of the next sampling coincides with the phase change angle, and the accurate acquisition of the phase change point is ensured. Therefore, the switching frequency is set to f e *360/(θ 1 -θ)。
Step three: if the current rotor position is in the interval described in (2), the switching frequency is set directly to the maximum switching frequency nf s After a switching period, the rotor position angle can be ensured to be positioned at the next sampling point(1) In the interval described in (2).
Step four: and accurately sampling the position of the commutation point, operating in a digital processor, updating PWM signals, and realizing the effect of eliminating current commutation errors.
The phase-change error compensation method for the hybrid excitation doubly salient motor provided by the invention has the advantage that the phase-change error is eliminated by adding a compensation algorithm in a control flow. The compensation algorithm does not need to change the structure of the original hybrid excitation doubly salient motor system, and has the advantage of easiness in implementation. The phase-change error compensation method for the hybrid excitation doubly salient motor can effectively compensate the phase-change error of the hybrid excitation doubly salient motor system, eliminate phase current oscillation and peak caused by the phase-change error, reduce the current stress of a switching tube in a driving circuit, and effectively utilize the current capacity of the switching tube. Furthermore, the phase-change error compensation method of the hybrid excitation doubly salient motor is beneficial to reducing motor torque pulsation, improving torque output capacity and having remarkable effect on improving the operation performance of the hybrid excitation doubly salient motor system.
Drawings
FIG. 1 is a cross-sectional view of a three-phase 12/8 pole hybrid excitation doubly salient motor;
FIG. 2 is a three-phase full-bridge power converter topology for a hybrid-excitation doubly salient motor;
FIG. 3 is a simplified inductance model and standard angle control conduction mode of a hybrid excitation doubly salient motor;
FIG. 4 is a schematic diagram of a first type of phase inversion error generation principle;
FIG. 5 is a schematic diagram of a second type of phase inversion error generation principle;
fig. 6 is a flowchart of the commutation error compensation algorithm.
Detailed Description
Specific embodiments of the present invention will be further described with reference to the accompanying drawings.
As shown in FIG. 1, the three-phase 12/8 hybrid excitation doubly salient motor is in a structural cross section, wherein an excitation winding, an armature winding and a permanent magnet are all positioned on a stator, and no winding or permanent magnet is arranged on a rotor. FIG. 2 shows a mixed excitationThe main power converter topology of the magnetic doubly salient motor is a three-phase full-bridge inverter. Wherein A-X, B-Y and C-Z are respectively A phase, B phase and C phase armature windings, and are connected in star shape. Current i a 、i b And i c The respective phase currents, the arrow directions of which are defined as positive directions. E (E) a 、E b And E is c The counter potential of the armature winding is respectively shown, and the "+" end is the end with high counter potential in the winding. It can be seen that at this point current flows into the armature winding from the positive end of the counter potential, i.e. the armature winding is absorbing electrical energy, and the motor is in an motoring mode of operation. V1-V6 are six switch tubes, wherein V1, V3 and V5 are upper tubes, and V4, V6 and V2 are lower tubes. In the figure, D1 to D6 are body diodes of switching transistors, and play a role in freewheeling in phase current chopping control. In addition, U in the figure dc Is the voltage of a direct current bus, i dc Is a direct current bus current, C f Is a filter capacitor on the bus.
When current is introduced into a phase winding of the hybrid excitation doubly salient motor, the generated torque is as follows:
wherein T is p Is the total torque output of a single phase, T pr Representing single-phase reluctance torque, T pe Represents single-phase excitation torque, L p Indicating phase winding self-inductance, i f Indicating exciting current, L pf Indicating that the excitation winding is mutually inductive with the phase winding and indicating the rotor position angle. The self inductance of the armature winding and the mutual inductance of the armature winding and the exciting winding are all related to the position angle of the motor rotor. The simplified inductance model and the standard angle control conduction mode of the hybrid excitation doubly salient motor are shown in fig. 3. Since the self inductance of the armature winding is typically an order of magnitude less than the mutual inductance of the armature winding and the field winding, only the mutual inductance of the armature winding and the field winding is represented in fig. 3. When the hybrid excitation doubly salient motor runs electrically, positive current is supplied to the corresponding winding in the rising area of the inductance, negative current is supplied to the corresponding winding in the falling area of the inductance, and continuous driving torque can be generated.
The mixed excitation doubly salient motor is driven by adopting a PWM modulation mode, and a driving signal is generated once in each switching period. A schematic diagram of a first type of commutation error is shown in fig. 4. The controller enters interruption at the moment k, samples a position signal through the rotary transformer, samples a three-phase current signal through the current Hall sensor, and calculates a corresponding PWM signal according to the position signal and the current signal. Ideally, the controller should output the calculated PWM signal immediately, acting between time k and k+1. In actual situations, as the controller needs a certain time for calculation, the calculated PWM signal cannot be output immediately, and the calculated PWM signal in the last interrupt is output until the next interrupt is entered, and the calculated PWM signal acts between the k+1 and the k+2 moments, so that the commutation error of one switching period is caused.
A schematic diagram of a second type of commutation error is shown in fig. 5. Ideally, the sampling frequency is infinite, the position signal sampled by the controller is a continuous signal, and the controller determines the position of phase change according to the continuous position signal and the set phase change angle parameter. At this time, the commutation position should be consistent with the set commutation angle regardless of the first type of commutation error. However, in practical situations, the sampling frequency of the controller is limited, and the position signal sampled by the controller is a discrete signal, which may be the case shown in fig. 5. The position signal sampled by the controller at time k+1 is just before the set commutation angle parameter, at which time the controller compares the sampled position signal with the set commutation angle parameter, thereby applying the PWM signal without commutation between time k+1 and time k+2 (without regard to the first type of commutation error). Until the time k+2, the controller acts the phase-converted PWM signal between the time k+2 and the time k+3 according to the sampled position signal and the set phase-converted angle parameter. This results in a commutation error of the angle alpha in the figure.
Fig. 6 is a flowchart of a commutation error compensation algorithm for a hybrid excitation doubly salient motor according to the present invention, according to which a specific embodiment is described in text as follows:
step one: sampling a current rotor position angle theta by a resolver coaxially installed with the motor, judging to beWhether or not in a section in which the phase change angle is θ 1 The sampled position signal is theta and the switching frequency is f s Maximum switching frequency nf s The electrical frequency is f e One switching cycle corresponds to an electrical angle of theta d ＝f e *360/f s ：
(1)θ∈(θ 1 -θ d *2/n，θ 1 -θ d /n)
(2)θ∈(θ 1 -(1+1/n)*θ d ，θ 1 -θ d *2/n)
Step two: if none of the current rotor positions is in the above section, it is indicated that the current rotor position is far from the set commutation point, so that no operation is required at this time to maintain the original switching frequency f s The method is unchanged.
Step two: if the current rotor position is in the section described in (1), calculating the current position angle theta and the phase change angle theta 1 And the angle difference between the two is set to a proper switching frequency, so that the position of the next sampling coincides with the phase change angle, and the accurate acquisition of the phase change point is ensured. Therefore, the switching frequency is set to f e *360/(θ 1 -θ)。
Step three: if the current rotor position is in the interval described in (2), the switching frequency is set directly to the maximum switching frequency nf s After one switching cycle, at the next sampling point, it is ensured that the rotor position angle is located in the interval described in (1).
Step four: and accurately sampling the position of the commutation point, operating in a digital processor, updating PWM signals, and realizing the effect of eliminating current commutation errors.
Finally, the compensation algorithm provided by the invention reduces the current fluctuation amplitude, and the phase current waveform does not generate unstable peak any more, so that the torque pulsation is greatly reduced, and the current capacity of the switching tube can be fully utilized.
The above embodiments are only for illustrating the technical idea of the present invention, and are not intended to limit the scope of the present invention, and any modification, equivalent replacement, improvement, etc. made on the basis of the technical scheme of the present invention according to the technical idea of the present invention should be included in the scope of the present invention.
Claims (1)
1. The phase-change error compensation method for the mixed excitation doubly salient motor is characterized in that the mixed excitation doubly salient motor is of a stator-rotor structure with double salient poles, a rotor is free of any winding and permanent magnets, an excitation winding, an armature winding and permanent magnets are arranged on the stator, the high-speed mixed excitation doubly salient motor adopts advance angle control or three-phase nine-state control, and the advance angle control and the three-phase nine-state control perform three-phase armature current phase-change control according to a rotor position angle;
the phase-change error compensation method comprises the following specific implementation steps:
(1) When theta is E (theta) 1 -θ d *2/n，θ 1 -θ d In the process of/n), the current rotor position angle theta and the commutation point theta are calculated 1 The distance between them is calculated according to the formula f e *360/(θ 1 θ), setting the time corresponding to the distance as the next switching period, thereby ensuring that the next switching period is accurately sampled to the commutation point;
(2) When theta is E (theta) 1 -(1+1/n)*θ d ，θ 1 -θ d * 2/n), the switching frequency is set to the maximum switching frequency nf s The method is applied to the next switching period, so that the sampling point of the next switching period is ensured to be positioned in the interval in the step (1);
(3) When θ is not within the above range, the switching frequency is kept at f s Unchanged;
the phase change angle is theta 1 The sampled position signal is theta and the switching frequency is f s Maximum switching frequency nf s The minimum switching frequency is (1/n) f s The electrical frequency is f e One switching cycle corresponds to an electrical angle of theta d ；
θ d The calculation formula of (2) is theta d ＝f e *360/f s Different switching frequencies f s And electric frequency f e The switching frequency is at the minimum frequency (1/n) f corresponding to different electrical angles s And a maximum frequency nf s According to the principle, when the rotor angle is close to the current commutation point, the switching frequency is changed, so that the commutation point is just positioned at the sampling point, accurate commutation is realized, and the commutation error caused by discrete sampling is eliminated.
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104393802A (en) * | 2014-11-07 | 2015-03-04 | 南京航空航天大学 | Line voltage detection-based doubly salient electro-magnetic motor position-less control method |
| CN105703687A (en) * | 2014-12-13 | 2016-06-22 | 包米勒公司 | Method for operating a converter and converter |
| CN106059409A (en) * | 2016-05-27 | 2016-10-26 | 北京航空航天大学 | Position sensor-free brushless direct-current motor rotor phase commutation error correction method and control system |
| CN107046388A (en) * | 2017-03-07 | 2017-08-15 | 湖南大学 | A kind of switched reluctance machines curren tracing control method, controller and governing system |
| CN109995304A (en) * | 2017-12-29 | 2019-07-09 | 东南大学 | A method of switched reluctance machines noise is reduced based on PWM carrier frequency is adjusted |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2800261B1 (en) * | 2013-04-29 | 2019-03-06 | Nxp B.V. | Mobile computing device comprising high voltage resonant DC-DC converter |
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Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104393802A (en) * | 2014-11-07 | 2015-03-04 | 南京航空航天大学 | Line voltage detection-based doubly salient electro-magnetic motor position-less control method |
| CN105703687A (en) * | 2014-12-13 | 2016-06-22 | 包米勒公司 | Method for operating a converter and converter |
| CN106059409A (en) * | 2016-05-27 | 2016-10-26 | 北京航空航天大学 | Position sensor-free brushless direct-current motor rotor phase commutation error correction method and control system |
| CN107046388A (en) * | 2017-03-07 | 2017-08-15 | 湖南大学 | A kind of switched reluctance machines curren tracing control method, controller and governing system |
| CN109995304A (en) * | 2017-12-29 | 2019-07-09 | 东南大学 | A method of switched reluctance machines noise is reduced based on PWM carrier frequency is adjusted |
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