CN106787997A - A kind of electric excitation biconvex electrode electric machine rotor exact position method of estimation - Google Patents

Abstract

The invention discloses a method for estimating the precise position of a rotor of an electrically excited double salient pole motor, which belongs to the technical field of motor control. In this method, three detection pulses A+C‑, B+A‑ and C+B‑ of the same width are sequentially injected into the armature winding through a three-phase full-bridge converter, and the detection response current i is respectively sampled at the end of the pulse _ac , i _ba and icb ; then calculate the two-phase series self-inductance values L _ac , L _{ba and} L _cb respectively according to the response current; then determine the sector where the rotor is located according to the relationship between the two-phase series self-inductance; finally, according to the obtained rotor The precise position of the rotor is estimated by the geometric similarity in the sector and the "inductance rectangle" formed by the self-inductance of two phases in series. In addition, the current rotational speed of the motor can be obtained according to the two adjacent rotor position estimations and the time interval between the two estimations. The method can realize accurate estimation of the rotor position in the starting process without adding additional hardware circuits, ensures the commutation accuracy, and improves the starting performance of the system without a position sensor.

Description

A Method for Precise Estimation of Rotor Position of Electrically Excited Doubly Salient Motor

technical field

The invention relates to a method for estimating the precise position of a rotor of an electrically excited double salient pole motor, belonging to the technical field of motor control.

Background technique

As a new type of special motor, electrically excited doubly salient motor has the advantages of simple and reliable structure, flexible control, and good fault tolerance performance. It has attracted extensive attention in the fields of aviation and new energy power generation. The installation of mechanical position sensors in traditional electrically excited double salient motor systems not only increases the volume cost of the system, but also reduces the reliability. Therefore, its position sensorless control strategy has important research value. The research on the position sensorless control strategy of pole motor is still in its infancy. The back EMF method is the most commonly used position sensorless control method at present, but it is difficult to accurately extract the back EMF amplitude in the low-speed starting stage, so this method is not applicable. In fact, the position sensorless control in the low-speed stage has always been a difficult point in the position sensorless control of various motors.

Zhao Yao et al. disclosed a patent of "a method for low-speed operation of electrically excited double salient pole motor without position based on series inductance slope threshold" (China, publication date: March 26, 2014, publication number: 103684137A). A position sensorless technology for low-speed operation of electrically excited double salient pole motors based on the threshold value of the slope of the series self-inductance. It calculates the slope value of the series self-inductance by detecting the slope value of the bus chopping current when the switching tube is turned on and off, and it is compared with the preset value. The threshold value is compared to determine whether the rotor has reached the commutation point. This method has high requirements on the current sampling time, and the commutation threshold needs to be selected according to the motor parameters, which increases the difficulty of actual implementation.

Zhou Xingwei et al. published a patent "a method for starting an electric excitation double salient pole motor without reverse rotation" (China, publication date: May 13, 2015, publication number: 104617832A) which discloses a The method of estimating the sector of the rotor based on the three-phase induced voltage, and accurately calculating the initial position of the rotor based on the geometric similarity relationship in the "inductance rectangle" of the doubly salient motor. This method can realize the rotor position estimation without injecting detection pulses into the armature winding, but the rotor position estimation method in the excitation voltage building process is only suitable for the initial position estimation when the motor is stationary, not for the starting process.

The "Starting method of doubly salient motor without position sensor control" (China, publication date, December 21, 2011, publication number: 102291070A) disclosed by Cheng Ming et al. discloses a doubly salient motor without position sensor control. The starting method, which applies a pulse voltage of the same time and equal amplitude to each stator winding combination through the inverter, and estimates the position of the rotor according to the current response. However, there is a big difference in the inductance characteristics between the permanent magnet doubly salient motor and the electrically excited doubly salient motor, and this method can only estimate the sector where the rotor is located, and cannot estimate the exact position.

At present, the rotor position estimation of many electrically excited double salient pole motors in the low-speed stage is mostly realized by injecting detection voltage pulses, but this method can only estimate the sector where the rotor is located, and cannot achieve accurate rotor position estimation, and this method has inevitable problems. The commutation delay will affect the starting performance of the motor.

Contents of the invention

In view of the above problems, the present invention proposes a method for estimating the precise position of the rotor of an electrically excited doubly salient pole motor.

The present invention adopts following technical scheme for solving its technical problem:

A method for estimating the precise position of a rotor of an electrically excited doubly salient motor comprises the following steps:

Step 1: Inject the detection pulses A+C-, B+A- and C+B- of the same duration into the armature winding sequentially through the three-phase full-bridge converter, and sample the detection response currents i _ac , i _ba and i _cb , where the detection pulse A+C- means that the upper tube of phase A and the lower tube of phase C are on, B+A- means that the upper tube of phase B and the lower tube of phase A are on, and C+B- means the upper tube of phase C , Phase B lower pipe is opened;

Step 2, calculate the two-phase series self-inductance values L _ac , L _ba and L _cb according to the response current;

Step 3, judge the sector where the rotor is located according to the relationship between the two-phase series self-inductance L _ac , L _ba and L _cb ;

Step 4, according to the geometric relationship of the two-phase series self-inductance L _ac , L _ba and L _cb of the electrically excited doubly salient pole motor and the sector where the rotor is located, the accurate rotor position estimation is performed;

Step 5, in the next pulse injection period, repeat the above steps 1-4 to estimate the precise rotor position; Step 6, estimate the current angular velocity of the motor according to the difference between the current two estimated precise rotor positions and the detection pulse injection interval;

In step 7, the real-time rotor position estimation is carried out through the latest accurate rotor estimated position and estimated angular velocity.

The expressions for calculating the self-inductance L _ac , L _ba and L _cb of the two-phase series series described in step 2 are respectively

and

Among them, R is the internal resistance of the single-phase winding of the electrically excited doubly salient motor, T is the detection pulse duration, and U _dc is the DC bus voltage.

As mentioned in step 3, judge the sector where the rotor is located according to the self-inductance relationship of the two-phase series series. If L _ac ≥ L _ba ≥ L _cb or L _ac ≥ L _cb ≥ L _ba , the rotor is located in sector 1; if L _ba ≥ L _ac ≥L _cb or L _ba ≥L _cb ≥L _ac , the rotor is located in sector 2; if L _cb ≥L _ba ≥L _ac or L _cb ≥L _ac ≥L _ba , the rotor is located in sector 3.

According to the geometric relationship of the self-inductance L _ac , L _ba and L _cb of the two-phase series series self-inductance of the electrically excited double salient pole motor and the sector where the rotor is located in step 4, the accurate rotor position estimation method is as follows. If the rotor is located in sector 1, then The expression of the rotor position angle is If the rotor is located in sector 2, the expression of the rotor position angle is If the rotor is located in sector 3, the expression of the rotor position angle is

The current angular velocity estimation expression of the estimated motor described in step 6 is k is an integer greater than or equal to 1, where θ(k) and θ(k-1) are the rotor position estimation angles of the k-th and k-1 injection detection pulses respectively, and θ(0) is defined as an accurate estimate of the initial rotor position As a result, Δt is the time interval between two adjacent detection pulse injections.

The real-time rotor estimated position expression of the motor described in step 7 is θ _e = θ (k) + ω _e (tk Δt), θ _e is the estimated angle of the precise rotor position; t is time, and θ (k) is The rotor position estimation angle of the kth injected detection pulse, where k is an integer greater than or equal to 1.

The beneficial effects of the present invention are as follows:

(1) Without adding additional hardware circuits, the precise position estimation of the electrically excited doubly salient pole motor rotor can be realized.

(2) The commutation accuracy in the low-speed starting stage is improved, and the sensorless starting performance of the electrically excited double salient pole motor is improved.

(3) The response current amplitude of the detection pulse is small, and the estimation of the rotor position is not affected by the saturation of the magnetic circuit.

Description of drawings

Fig. 1 is a doubly salient motor and its control topology structure diagram provided by the present invention.

Fig. 2 is a sectional view of a 12/8-pole electrically excited double salient pole motor.

Figure 3 is the three-phase self-inductance curve and power-on rule diagram of the electrically excited doubly salient motor.

Fig. 4 is an equivalent circuit diagram when a detection pulse A+C- is injected.

Fig. 5 is a self-inductance curve diagram of two-phase series connection of electrically excited doubly salient pole motor.

Fig. 6 is an "inductance rectangle" diagram formed by two-phase series self-inductance of an electrically excited double salient pole motor when the rotor is located in sector 1.

detailed description

The invention will be described in further detail below in conjunction with the accompanying drawings.

The system structure block diagram of the present invention is shown in Figure 1, mainly includes: electric excitation double salient pole motor, three-phase full-bridge converter, excitation control circuit etc., wherein the section of electric excitation double salient pole motor is as shown in Figure 2, three-phase The self-inductance curve is shown in Figure 3. The specific implementation steps are as follows:

1. Turn on the switching tubes Q ₁ and Q ₂ , Q ₃ and Q ₄ , Q ₅ and Q ₆ in Figure 1 for an equal period of time, and inject the same duration of detection on the armature winding through the three-phase full-bridge converter in sequence Pulse A+C-, B+A- and C+B-, wherein the detection pulse A+C- indicates that the upper tube of phase A and the lower tube of phase C are on, and B+A- indicates that the upper tube of phase B and the lower tube of phase A are on , C+B- means that the upper transistor of phase C and the lower transistor of phase B are turned on, and the detection response currents i _ac , i _ba and i _cb are respectively sampled at the end of the detection pulse.

2. Calculate the two-phase series self-inductance values L _ac , L _ba and L _cb according to the response current. The two-phase series self-inductance expressions are respectively and Among them, R is the internal resistance of the single-phase winding of the electrically excited doubly salient pole motor, T is the duration of the injection detection pulse, and U _dc is the DC bus voltage.

The calculation principle of the two-phase series self-inductance is as follows. Taking the detection pulse A+C- as an example to illustrate, the amplitude of the back EMF of the motor at the low speed stage is small and can be ignored. The equivalent circuit when the detection pulse A+C- is injected is shown in Figure 4 As shown, at this time, the response current can be expressed as

where τ is the time constant, the expression is

Therefore, according to the response at the end of the detection pulse, the self-inductance expression of A and C two-phase series series can be obtained

Other two-phase series self-inductance can be calculated by similar method.

3. Judging the sector where the rotor is located according to the relationship between the two-phase series self-inductance L _ac , L _ba and L _cb . According to the curve of the two-phase series self-inductance changing with the rotor position shown in Figure 5, it can be seen that the sector where the rotor is located can be judged according to the relationship between the two-phase series self-inductance L _ac , L _ba and L _cb , and the specific corresponding relationship is as follows shown in the table.

Table 1 Relationship between self-inductance of two-phase series series and rotor sector

4. Accurate rotor position estimation is carried out according to the geometric relationship of the two-phase series self-inductance L _ac , L _ba and L _cb of the electrically excited doubly salient pole motor and the sector where the rotor is located. If the rotor is located in sector 1, the expression of the rotor position angle is If the rotor is located in sector 2, the expression of the rotor position angle is If the rotor is located in sector 3, the expression of the rotor position angle is

The principle of accurate rotor position angle estimation is as follows. Take the rotor located in sector 1 as an example. At this time, the geometric relationship between the two-phase series self-inductance L _ac , L _ba and L _cb is shown in Figure 6. In the formed "inductance rectangle" ABCD , △AEH is geometrically similar to △ACD, so there is the following corresponding proportional relationship

Among them: AH, AD, EH, CD, EG and HF represent the lengths corresponding to two points in the "inductance rectangle" ABCD in Figure 6. In addition, as shown in the "inductance rectangle" in Figure 6, the rotor position θ and the two-phase series self-inductance satisfy formula (5) and formula (6) respectively.

According to formulas (4), (5) and (6), we can get

Therefore, the exact position expression when the rotor is in sector 1 is

There are completely similar calculation methods when the rotor is located in other sectors.

5. In the next pulse injection period, repeat the above steps 1-4 to estimate the precise position angle of the rotor.

6. Estimate the current angular velocity of the motor according to the difference between the two current estimated precise rotor positions and the detection pulse injection interval.

Note that the rotor initial position angle estimation result is θ(0), the kth (k is an integer greater than or equal to 1), and the k-1 rotor precise position estimation results are respectively θ(k), θ(k-1), adjacent The interval between two detection pulse injections is Δt, then the estimated angular velocity of the motor is

7. Real-time rotor position estimation is carried out through the latest accurate rotor estimated position and estimated angular velocity, the expression of which is

θ _e ＝θ(k)+ω _e ·(tk·Δt) (10)

Through the above steps, the position sensorless starting of the electrically excited double salient pole motor can be realized, and the precise position estimation of the rotor can be performed, the commutation error is reduced, and the position sensorless starting performance of the system is guaranteed.

The above embodiments are only to illustrate the technical ideas of the present invention, and can not limit the protection scope of the present invention with this. All technical ideas proposed in accordance with the present invention, any changes made on the basis of technical solutions, all fall within the protection scope of the present invention. Inside.

Claims (6)

1. a kind of electric excitation biconvex electrode electric machine rotor exact position method of estimation, it is characterised in that：Comprise the following steps：

Step 1, be implanted sequentially on armature winding by three-phase full bridge converters identical duration detection pulse A+C-, B+A- and C+B-, and the sample detecting response current i when end-of-pulsing is detected_ac、i_baAnd i_cb, wherein detection pulse A+C- is represented in A phases Pipe, C phase down tubes are open-minded, and B+A- represents that pipe, A phase down tubes are open-minded in B phases, and C+B- represents that pipe, B phase down tubes are open-minded in C phases；

Step 2, two-phase series self-inductances value L is calculated according to response current_ac、L_baAnd L_cb；

Step 3, according to two-phase series self-inductances L_ac、L_baWith L_cbMagnitude relationship judge sector where rotor；

Step 4, the two-phase series self-inductances L according to electric excitation biconvex electrode electric machine_ac、L_baWith L_cbGeometrical relationship and rotor where fan Area carries out accurate rotor position estimate；

Step 5, in next impulses injection cycle, repeats the above steps 1 --- and 4 carry out the estimation of rotor exact position；

Step 6, difference and detection impulses injection interval time according to the accurate rotor-position of estimation twice currently estimate that motor is worked as Preceding angular speed；

Step 7, real-time rotor position estimate is carried out by the last accurate rotor estimated location with estimated angular velocity.

2. a kind of electric excitation biconvex electrode electric machine rotor exact position method of estimation according to claim 1, it is special Levy and be：Two-phase series self-inductances L is calculated described in step 2_ac、L_baAnd L_cbExpression formula be respectivelyWherein R is electricity The single-phase winding internal resistance of excitation biconvex electrode electric machine, T is detection pulse duration, U_dcIt is DC bus-bar voltage.

3. a kind of electric excitation biconvex electrode electric machine rotor exact position method of estimation according to claim 1, it is characterised in that： Rotor place sector is judged described in step 3 according to two-phase series self-inductances magnitude relationship, if L_ac≥L_ba≥L_cbOr L_ac≥L_cb≥ L_ba, then rotor is positioned at sector 1；If L_ba≥L_ac≥L_cbOr L_ba≥L_cb≥L_ac, then rotor is positioned at sector 2；If L_cb≥L_ba≥L_acOr L_cb≥L_ac≥L_ba, then rotor is positioned at sector 3.

4. a kind of electric excitation biconvex electrode electric machine rotor exact position method of estimation according to claim 1, it is special Levy and be：Two-phase series self-inductances L described in step 4 according to electric excitation biconvex electrode electric machine_ac、L_baWith L_cbGeometry close It is as follows that sector where system and rotor carries out accurate rotor position estimate method, if rotor is positioned at sector 1, rotor position angle Expression formula isIf rotor is located at sector 2, rotor position angle expression formula isIf rotor is located at sector 3, rotor position angle expression formula is

5. a kind of electric excitation biconvex electrode electric machine rotor exact position method of estimation according to claim 1, it is characterised in that： Estimate that motor current angular velocity estimates that expression formula is described in step 6K is the integer more than or equal to 1, Wherein θ (k), θ (k-1) are respectively kth, the rotor position estimate angle of k-1 injection detection pulse, and it is initial turn to define θ (0) The sub- accurate estimated result in position, Δ t detects impulses injection interval time twice for adjacent.

6. a kind of electric excitation biconvex electrode electric machine rotor exact position method of estimation according to claim 1, it is characterised in that：Institute The real-time rotor estimated location expression formula of motor described in step 7 is stated for θ_e=θ (k)+ω_e(t-k Δs t), θ_eIt is the accurate position of rotor Put estimation angle；T is the time, and θ (k) is the rotor position estimate angle of kth time injection detection pulse, and k is the integer more than or equal to 1.