阅读说明：本技术 一种永磁同步电机转子初始位置检测方法、装置及变频器 (Method and device for detecting initial position of rotor of permanent magnet synchronous motor and frequency converter ) 是由 李光明 徐政 王秀波 徐向宇 关彦彬 于 2019-11-15 设计创作，主要内容包括：本发明公开了一种永磁同步电机转子初始位置检测方法、装置、变频器及存储介质,涉及转子初始位置检测技术领域,该方法包括：分别封锁三相中任一相输出,由其余两相选择性地对三相绕组进行加压；在加压结束后,分别进行电流采样,得到第一采样电流、第二采样电流和第三采样电流；基于磁极轴向角度计算公式,根据所述第一采样电流、所述第二采样电流和所述第三采样电流确定转子磁极轴向位置。本发明提供的永磁同步电机转子初始位置检测方法、装置及变频器,无需进行多个电压矢量的调制,大大简化了检测过程,并彻底消除了控制误差的影响。(The invention discloses a method and a device for detecting the initial position of a permanent magnet synchronous motor rotor, a frequency converter and a storage medium, which relate to the technical field of the detection of the initial position of the rotor, and the method comprises the following steps: any phase output in the three phases is blocked respectively, and the other two phases selectively pressurize the three-phase winding; after pressurization is finished, current sampling is respectively carried out to obtain a first sampling current, a second sampling current and a third sampling current; and determining the axial position of the magnetic pole of the rotor according to the first sampling current, the second sampling current and the third sampling current based on a magnetic pole axial angle calculation formula. The method and the device for detecting the initial position of the permanent magnet synchronous motor rotor and the frequency converter do not need to modulate a plurality of voltage vectors, greatly simplify the detection process and thoroughly eliminate the influence of control errors.)

1. A method for detecting the initial position of a permanent magnet synchronous motor rotor is characterized by comprising the following steps:

any phase output in the three phases is blocked respectively, and the other two phases selectively pressurize the three-phase winding;

after pressurization is finished, current sampling is respectively carried out to obtain a first sampling current, a second sampling current and a third sampling current;

and determining the axial position of the magnetic pole of the rotor according to the first sampling current, the second sampling current and the third sampling current based on a magnetic pole axial angle calculation formula.

2. The method for detecting the initial position of the rotor of the permanent magnet synchronous motor according to claim 1, wherein the output of any one of the three phases is blocked, and the other two phases selectively pressurize the three-phase winding, specifically: if the three-phase winding adopts a Y-type wiring mode, the C phase is blocked, and only the A phase and the B phase output pulse width modulation direct current voltage U_abThe windings of the A phase and the B phase are reversely connected in series for electrifying, the A phase and the B phase are blocked in sequence by the same principle, and the corresponding voltage U is output_bcAnd U_ca(ii) a If the three-phase winding adopts a delta connection mode, the output U is_abThe series circuit corresponding to the B-phase winding and the C-phase winding is reversely connected in parallel with the A-phase winding, and the U is sequentially output in the same way_bcAnd U_ca。

3. The method for detecting the initial position of the rotor of the permanent magnet synchronous motor according to claim 2, wherein after the pressurization is finished, current sampling is respectively performed to obtain a first sampling current, a second sampling current and a third sampling current, and specifically: if the pressurizing time length T is reached, the pressurizing is finished, and the three-phase winding adopts a Y-shaped wiring mode, the first sampling current I_ab≈DU_dcT/[3L₀+3L₁cos2(θ′+30°)]Second sampling current I_bc≈DU_dcT/(3L₀-3L₁cos2 θ'), third sampled current I_ca≈DU_dcT/[3L₀+3L₁cos2(θ′-30°)](ii) a If the three-phase winding adopts a delta connection mode, the first sampling current I_ab≈DU_dcT/(L₀+L₁cos2 θ'), second sampled current I_bc≈DU_dcT/[L₀+L₁cos2(θ′+60°)]Third sampling current I_ca≈DU_dcT/[L₀+L₁cos2(θ′-60°)]Wherein L is₀Being a constant component of inductance, L₁The component of inductance change caused by the saliency, D is the on duty ratio, U_dcIs the DC bus voltage, L, of the frequency converter_abIs the corresponding equivalent inductance.

4. The method for detecting the initial position of the rotor of the permanent magnet synchronous motor according to claim 3, wherein the determining the axial position of the rotor magnetic pole according to the first sampling current, the second sampling current and the third sampling current based on the calculation formula of the axial angle of the magnetic pole specifically comprises: by the formula

5. The utility model provides a PMSM rotor initial position detection device which characterized in that includes:

the pressurizing module is used for respectively blocking the output of any one phase of the three phases and selectively pressurizing the three-phase winding by the other two phases;

the current sampling module is used for respectively sampling current after pressurization is finished to obtain a first sampling current, a second sampling current and a third sampling current;

and the position determining module is used for determining the axial position of the magnetic pole of the rotor according to the first sampling current, the second sampling current and the third sampling current based on a magnetic pole axial angle calculation formula.

6. The device for detecting the initial position of the rotor of the permanent magnet synchronous motor according to claim 5, wherein the pressurizing module is configured to block the output of any one of the three phases and selectively pressurize the three-phase winding by the remaining two phases, and specifically comprises: if the three-phase winding adopts a Y-type wiring mode, the C phase is blocked, and only the A phase and the B phase output pulse width modulation direct current voltage U_abThe windings of the A phase and the B phase are reversely connected in series for electrifying, the A phase and the B phase are blocked in sequence by the same principle, and the corresponding voltage U is output_bcAnd U_ca(ii) a If the three-phase winding adopts a delta connection mode, the output U is_abThe series circuit corresponding to the B-phase winding and the C-phase winding is reversely connected in parallel with the A-phase winding, and the U is sequentially output in the same way_bcAnd U_ca。

7. The PMSM rotor initial position detection device of claim 6, wherein in the current sampling module: after pressurization is finished, current sampling is respectively carried out to obtain a first sampling current, a second sampling current and a third sampling current, and the method specifically comprises the following steps: if the pressurizing time length T is reached, the pressurizing is finished, and the three-phase winding adopts a Y-shaped wiring mode, the first sampling current I_ab≈DU_dcT/[3L₀+3L₁cos2(θ′+30°)]Second sampling current I_bc≈DU_dcT/(3L₀-3L₁cos2 θ'), third sampled current I_ca≈DU_dcT/[3L₀+3L₁cos2(θ′-30°)](ii) a If the three-phase winding adopts a delta connection mode, the first sampling current I_ab≈DU_dcT/(L₀+L₁cos2 θ'), second sampled current I_bc≈DU_dcT/[L₀+L₁cos2(θ′+60°)]Third sampling current I_ca≈DU_dcT/[L₀+L₁cos2(θ′-60°)]Wherein L is₀Being a constant component of inductance, L₁The component of inductance change caused by the saliency, D is the on duty ratio, U_dcIs the DC bus voltage, L, of the frequency converter_abIs the corresponding equivalent inductance.

8. The device for detecting the initial position of the rotor of the permanent magnet synchronous motor according to claim 7, wherein the position determining module is configured to determine the axial position of the rotor magnetic pole according to the first sampling current, the second sampling current and the third sampling current based on a magnetic pole axial angle calculation formula, and specifically: by the formulaThe rotor pole axial position is determined.

9. A frequency converter, comprising: one or more processors, one or more memories; the one or more memories coupled to the one or more processors for storing computer program code comprising computer instructions which, when executed by the one or more processors, cause the frequency converter to perform the method of permanent magnet synchronous motor rotor initial position detection according to any of claims 1-4.

10. A computer storage medium having stored thereon computer instructions which, when run on a terminal, cause the terminal to perform the method of permanent magnet synchronous motor rotor initial position detection according to any of claims 1-4.

Technical Field

The invention relates to the technical field of rotor initial position detection, in particular to a method and a device for detecting an initial position of a permanent magnet synchronous motor rotor and a frequency converter.

Background

In order to ensure that a speed sensor-less control system of a Permanent Magnet Synchronous Motor (PMSM) has a high-torque and backlash-free starting characteristic, a variable frequency controller of the PMSM should have a function of detecting an initial position of a rotor.

The detection and estimation of the initial position of the rotor must ensure that the rotor position is not changed in the whole process, and simultaneously meet the requirements of precision and speed.

Disclosure of Invention

The invention provides a method and a device for detecting the initial position of a permanent magnet synchronous motor rotor and a frequency converter, which do not need to modulate a plurality of voltage vectors, greatly simplify the detection process and thoroughly eliminate the influence of control errors.

In a first aspect, an embodiment of the present invention provides a method for detecting an initial position of a rotor of a permanent magnet synchronous motor, including:

any phase output in the three phases is blocked respectively, and the other two phases selectively pressurize the three-phase winding;

after pressurization is finished, current sampling is respectively carried out to obtain a first sampling current, a second sampling current and a third sampling current;

and determining the axial position of the magnetic pole of the rotor according to the first sampling current, the second sampling current and the third sampling current based on a magnetic pole axial angle calculation formula.

Preferably, the blocking of the output of any one of the three phases is performed, and the remaining two phases selectively pressurize the three-phase winding, specifically: if the three-phase winding adopts a Y-type wiring mode, the C phase is blocked, and only the A phase and the B phase output pulse width modulation direct current voltage U_abThe windings of the A phase and the B phase are reversely connected in series for electrifying, the A phase and the B phase are blocked in sequence by the same principle, and the corresponding voltage U is output_bcAnd U_ca(ii) a If the three-phase winding adopts a delta connection mode, the output U is_abThe series circuit corresponding to the B-phase winding and the C-phase winding is reversely connected in parallel with the A-phase winding, and the U is sequentially output in the same way_bcAnd U_ca。

Preferably, after the pressurization is finished, current sampling is respectively performed to obtain a first sampling current, a second sampling current and a third sampling current, specifically: if the pressurizing time length T is reached, the pressurizing is finished, and the three-phase winding adopts a Y-shaped wiring mode, the first sampling current I_ab≈DU_dcT/[3L₀+3L₁cos 2(θ′+30°)]Second sampling current I_bc≈DU_dcT/(3L₀-3L₁cos2 θ'), third sampled current I_ca≈DU_dcT/[3L₀+3L₁cos 2(θ′-30°)](ii) a If the three-phase winding adopts a delta connection mode, the first sampling current I_ab≈DU_dcT/(L₀+L₁cos2 θ'), second sampled current I_bc≈DU_dcT/[L₀+L₁cos 2(θ′+60°)]Third sampling current I_ca≈DU_dcT/[L₀+L₁cos 2(θ′-60°)]Wherein L is₀Being a constant component of inductance, L₁The component of inductance change caused by the saliency, D is the on duty ratio, U_dcIs the DC bus voltage, L, of the frequency converter_abIs the corresponding equivalent inductance.

Preferably, the determining the axial position of the rotor magnetic pole according to the first sampling current, the second sampling current and the third sampling current based on the magnetic pole axial angle calculation formula specifically includes: by the formula

The rotor pole axial position is determined.

In a second aspect, an embodiment of the present invention provides a device for detecting an initial position of a rotor of a permanent magnet synchronous motor, including:

the pressurizing module is used for respectively blocking the output of any one phase of the three phases and selectively pressurizing the three-phase winding by the other two phases;

the current sampling module is used for respectively sampling current after pressurization is finished to obtain a first sampling current, a second sampling current and a third sampling current;

and the position determining module is used for determining the axial position of the magnetic pole of the rotor according to the first sampling current, the second sampling current and the third sampling current based on a magnetic pole axial angle calculation formula.

Preferably, the pressurizing module is configured to respectively block an output of any one of the three phases, and selectively pressurize the three-phase winding by the remaining two phases, specifically: if the three-phase winding adopts a Y-type wiring mode, the C phase is blocked, and only the A phase and the B phase output pulse width modulation direct current voltage U_abThe windings of the A phase and the B phase are reversely connected in series for electrifying, the A phase and the B phase are blocked in sequence by the same principle, and the corresponding voltage U is output_bcAnd U_ca(ii) a If the three-phase winding adopts a delta connection mode, the output U is_abThe series circuit corresponding to the B-phase winding and the C-phase winding is reversely connected in parallel with the A-phase winding, and the U is sequentially output in the same way_bcAnd U_ca。

Preferably, in the current sampling module: after pressurization is finished, current sampling is respectively carried out to obtain a first sampling current, a second sampling current and a third sampling current, and the method specifically comprises the following steps: if the pressurizing time length T is reached, the pressurizing is finished, and the three-phase winding adopts a Y-shaped wiring mode, the first sampling current I_ab≈DU_dcT/[3L₀+3L₁cos 2(θ′+30°)]Second sampling current I_bc≈DU_dcT/(3L₀-3L₁cos2 θ'), third sampled current I_ca≈DU_dcT/[3L₀+3L₁cos 2(θ′-30°)](ii) a If the three-phase winding adopts a delta connection mode, the first sampling current I_ab≈DU_dcT/(L₀+L₁cos2 θ'), second sampled current I_bc≈DU_dcT/[L₀+L₁cos 2(θ′+60°)]Third sampling current I_ca≈DU_dcT/[L₀+L₁cos 2(θ′-60°)]Wherein L is₀Being a constant component of inductance, L₁The component of inductance change caused by the saliency, D is the on duty ratio, U_dcIs the DC bus voltage, L, of the frequency converter_abIs the corresponding equivalent inductance.

Preferably, the position determining module is configured to determine an axial position of a magnetic pole of the rotor according to the first sampling current, the second sampling current, and the third sampling current based on a magnetic pole axial angle calculation formula, and specifically includes: by the formula

The rotor pole axial position is determined.

In a third aspect, an embodiment of the present invention provides a frequency converter, including: one or more processors, one or more memories; the one or more memories are coupled to the one or more processors and the one or more memories are configured to store computer program code comprising computer instructions that, when executed by the one or more processors, cause the frequency converter to perform the method for detecting an initial position of a rotor of a PMSM as described above.

In a fourth aspect, an embodiment of the present invention provides a computer storage medium, on which computer instructions are stored, and when the computer instructions are run on a terminal, the terminal is caused to execute the method for detecting the initial position of the rotor of the permanent magnet synchronous motor.

By adopting the technical scheme, the same voltage is applied to the stator windings of all phases in sequence, and the axial position of the magnetic pole of the rotor is judged according to the magnitude of the response current, so that the detection process is simplified, the error influence is eliminated, and the detection precision is improved.

Drawings

Fig. 1 is a flowchart of a method for detecting an initial position of a rotor of a permanent magnet synchronous motor according to an embodiment of the present invention;

fig. 2 is a schematic diagram of an inverter circuit according to an embodiment of the present invention;

FIG. 3 is a schematic diagram of reference voltage vectors for two wiring patterns provided by an embodiment of the present invention;

FIG. 4 illustrates a Y-type wiring current direction specification provided by an embodiment of the present invention;

FIG. 5 illustrates delta-type wiring current direction specification provided by an embodiment of the present invention;

FIG. 6 is a flow chart of software provided by an embodiment of the present invention;

fig. 7 is a block diagram of a device for detecting an initial position of a rotor of a permanent magnet synchronous motor according to an embodiment of the present invention.

Detailed Description

The following further describes embodiments of the present invention with reference to the drawings. It should be noted that the description of the embodiments is provided to help understanding of the present invention, but the present invention is not limited thereto. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

In the description of the embodiments herein, "/" means "or" unless otherwise specified, for example, a/B may mean a or B; "and/or" herein is merely an association describing an associated object, and means that there may be three relationships, e.g., a and/or B, which may mean: a exists alone, A and B exist simultaneously, and B exists alone. In addition, in the description of the embodiments of the present application, "a plurality" means two or more than two.

In the following, the terms "first", "second" are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the embodiments of the present application, "a plurality" means two or more unless otherwise specified.

In order to ensure that a permanent magnet synchronous motor speed sensorless control system can start with high torque and does not reverse, and provide rotor angle information for off-line identification of motor inductance parameters, a variable frequency controller of the permanent magnet synchronous motor speed sensorless control system has a function of detecting an initial position of a rotor. Therefore, the application provides a split-phase injection detection method, a frequency converter blocks one phase each time, the other two phases output voltage pulse vectors, voltages with the same magnitude are independently applied to stator windings of each phase of the PMSM in three times, and the axial angle of a magnetic pole can be accurately calculated by using current sampled synchronously at a single time. Because the modulation of a plurality of voltage vectors is not needed, the detection process is greatly simplified, and the influence of control errors is thoroughly eliminated.

In a first aspect, as shown in fig. 1, an embodiment of the present invention provides a method for detecting an initial position of a rotor of a permanent magnet synchronous motor, including:

step S101, respectively blocking the output of any phase of the three phases, and selectively pressurizing the three-phase winding by the other two phases;

step S102, after pressurization is finished, current sampling is respectively carried out to obtain a first sampling current, a second sampling current and a third sampling current;

and S103, determining the axial position of the magnetic pole of the rotor according to the first sampling current, the second sampling current and the third sampling current based on a magnetic pole axial angle calculation formula.

Preferably, in step S101: any phase output in the three phases is blocked respectively, and the other two phases selectively pressurize the three-phase winding, specifically: if the three-phase winding adopts a Y-type wiring mode, the C phase is blocked, and only the A phase and the B phase output pulse width modulation direct current voltage U_abThe windings of the A phase and the B phase are reversely connected in series for electrifying, the A phase and the B phase are blocked in sequence by the same principle, and the corresponding voltage U is output_bcAnd U_ca(ii) a If the three-phase winding adopts a delta connection mode, the output U is_abThe series circuit corresponding to the B-phase winding and the C-phase winding is reversely connected in parallel with the A-phase winding, and the U is sequentially output in the same way_bcAnd U_ca。

Preferably, in step S102: after pressurization is finished, current sampling is respectively carried out to obtain a first sampling current, a second sampling current and a third sampling current, and the method specifically comprises the following steps: if the pressurizing time length T is reached, the pressurizing is finished, and the three-phase winding adopts a Y-shaped wiring mode, the first sampling current I_ab≈DU_dcT/[3L₀+3L₁cos 2(θ′+30°)]Second sampling current I_bc≈DU_dcT/(3L₀-3L₁cos2 θ'), third sampled current I_ca≈DU_dcT/[3L₀+3L₁cos 2(θ′-30°)](ii) a If the three-phase winding adopts a delta connection mode, the first sampling current I_ab≈DU_dcT/(L₀+L₁cos2 θ'), second sampled current I_bc≈DU_dcT/[L₀+L₁cos 2(θ′+60°)]Third sampling current I_ca≈DU_dcT/[L₀+L₁cos 2(θ′-60°)]Wherein L is₀Being a constant component of inductance, L₁The component of inductance change caused by the saliency, D is the on duty ratio, U_dcIs the DC bus voltage, L, of the frequency converter_abIs the corresponding equivalent inductance.

Preferably, in step S103: based on a magnetic pole axial angle calculation formula, determining the axial position of the magnetic pole of the rotor according to the first sampling current, the second sampling current and the third sampling current, specifically: by the formulaThe rotor pole axial position is determined.

The following will be specifically explained:

winding wiring form and rotor position definition

The PMSM's three-phase stator winding mode of connection has two kinds, generally adopts Y type wiring, has also adopted delta type wiring in order to satisfy special needs. The frequency converter is controlled by SVPWM and outputs proper voltage according to the position of the magnetic pole of the rotorVector, forming the required stator magnetic field. The three-phase inverter circuit allows 8 different switching states, when combined with the windings of the Y-connection, to form 6 non-zero voltage vectors and 2 zero voltage vectors, which are defined conventionally, and to synthesize other required voltage vectors from these basic voltage vectors, and to convert S into S₁/S₄/S₆Conduction, S₂/S₃/S₅The output at turn-off is taken as the reference voltage vector.

Fig. 2 is a schematic diagram of an inverter circuit.

The rotor position is defined by two methods, one method is an electrical included angle theta between the rotor position and a reference voltage vector, and the method is based on the output control of a frequency converter; the other type is an electrical included angle theta' with the axial direction of the A-phase winding, which is based on the structure of the motor. The relationship between the reference voltage vector and the a-phase axis in the Y-connection and the Δ -connection is shown in fig. 3. When Y-type wiring is performed, a stator magnetic field formed by a reference voltage vector is consistent with the axial direction of the A-phase winding, so that theta is equal to theta'; in the case of the delta connection, the stator magnetic field formed by the reference voltage vector lags behind the a-phase winding by 30 °, so θ becomes θ' -30 °.

Self-inductance and mutual-inductance of stator winding

The split-phase injection method is provided based on a relational formula between stator interphase inductance and a rotor position angle theta of the permanent magnet synchronous motor. The basic principle is as follows: and blocking one phase output of the frequency converter in sequence, applying chopped pulse voltage vectors with a certain duty ratio to the other two opposite three-phase windings, applying three voltage vectors in total, measuring three inter-phase currents, and obtaining the difference of inter-phase inductances according to the difference of inter-phase current responses so as to reversely deduce a rotor position angle theta. Therefore, a relational expression between the interphase inductance and the rotor position angle θ is first derived.

The higher harmonic exists in the permanent magnet synchronous air gap magnetic field, but in the actual motor design and application, the action of higher harmonic magnetomotive force and magnetic density is greatly weakened by adopting the measures of short-distance winding distribution, salient pole shape design and the like, so that the higher harmonic is ignored, only the air gap fundamental wave magnetic field is considered, and the engineering precision requirement can be met.

First consider the self-inductance of the stator three-phase winding. Considering radicals onlyWhen the d-axis of the rotor coincides with the axis of the a-phase, that is, θ 'is 0 ° or θ' is 180 °, the self-inductance of the a-phase reaches a maximum value, and the maximum value is L_aad(ii) a When the d axis of the rotor is perpendicular to the axis of the phase a, that is, θ 'is 90 ° or θ' is 270 °, the self-inductance of the phase a reaches a minimum value, and the minimum value is set as L_aaq. In other positions, the self-inductance of the A phase changes sinusoidally with the magnetic permeability.

The formula of the change of the self-inductance of the phase A along with the position angle theta of the rotor is as follows:

L_aa＝L₀+L₁cos 2θ′ (1)

wherein, L₀And L₁The values of (A) are respectively:

similarly, the formula of the variation of the self-inductance of the B phase and the C phase along with the rotor position angle theta is as follows:

the mutual inductance of the stator windings is then taken into account. The mutual inductance formula between the A phase winding and the B phase winding is as follows:

similarly, the mutual inductance formulas of the BC and CA windings are respectively as follows:

from the self-inductance and mutual inductance of the stator windings, it can be seen that the inductance at different positions of the stator is related to the rotor position angle θ'. The following is a derivation of the split-phase injection method for Y-type and delta-type connections, respectively.

Rotor magnetic pole position identification under Y-shaped connection

The positive direction for the Y-wire current is specified as shown in fig. 4.

When S is₄Conduction, S₂/S₃/S₅/S₆Off, S₁In order to block the C phase, only the A and B phases output the pulse width modulated DC voltage U_ab. At this time, phase A and phase B are oppositely electrified in series, phase C is disconnected, and voltage vector U is obtained_abBetween the A-phase and B-phase windings. The relationship between the phases of the currents is:

i_ab＝i_a＝-i_b,i_c＝0 (8)

voltage vector U_abThe relationship to current and inductance is:

therefore, the interphase inductance L of the A phase and the B phase under the Y-shaped wiring_abAnd a resistor R_abRespectively as follows:

L_ab＝L_aa+L_bb-2M_ab(10)

R_ab＝2R (11)

voltage vector U_abCorresponding to the added resistance R_abAnd an inductance L_abCurrent response i across the series first order circuit_abThe expression of (a) is:

when t is very small, according to the equivalent infinitesimal formula, there are

Thus, i_abIs approximately as

It can be seen that when t is small, i_abAnd phase-to-phase inductance L_abRelated to interphase resistance R_abIs irrelevant.

Derivation of L_abIs described in (1). Substituting the self inductance and mutual inductance formula of the stator winding into L_abExpression of, having

It can be seen that the interphase inductance L_abIn relation to the rotor position angle theta and the period of variation of the phase-to-phase inductance is pi, i.e. the angle theta' changes by 180 DEG every time_abVarying by one cycle.

Similarly, when a voltage vector U is applied_bcBlocking phase A, and applying voltage vector U_caWhen B phase is blocked, respectively deducing L_bcAnd L_caCan obtain the product

L_bc＝L_bb+L_cc-2M_bc＝3L₀-3L₁cos 2θ' (16)

Setting DC bus voltage as U_dc，U_ab、U_bc、U_caThe duty cycles of (a) and (b) are all D, and the current rise times are all t. According to the relation between the interphase current and the interphase inductance of the formula (14), the magnitude of the interphase current at the time t is obtained

According to i_ab、i_bcAnd i_caThe expression (2) shows that the three groups of inter-phase currents all contain the information of the rotor position angle theta'. By equation (19), θ' can be solved:

the value range of the 2 theta 'angle calculated by the formula is 0-180 degrees, namely the value range of the theta' angle is 0-90 degrees, the actual value of the rotor position angle theta 'is 0-180 degrees, therefore, the quadrant where the 2 theta' is located needs to be judged according to the positive and negative values of sin2 theta 'and cos2 theta', the value range of the 2 theta 'is expanded to 360 degrees, namely the value range of the theta' is expanded to 180 degrees.

The specific method is shown in Table 1.

Notation and evaluation of Table 1 θ

For the sign determination of sin2 θ 'and cos2 θ', note that L₁The symbol of (2). Rewriting L₁The definition formula of (1) is as follows:

as previously described, for a salient pole permanent magnet synchronous machine, there are permanent magnets in the d-axis direction. The magnetic conductivity of the permanent magnet is close to air, so that the equivalent air gap length in the d-axis direction is increased, the magnetic conductivity is small, and the inductance is small; the q-axis direction is not provided with a permanent magnet but is made of ferromagnetic materials, so that the equivalent air gap length is small, the magnetic conductivity is large, and the inductance is large. Thus in the above formula, L_aadAnd L_aaqThe size relationship of (A) is as follows:

L_aad＜L_aaq(21)

therefore L₁< 0, i.e. L₁The sign of (a) is negative. In formula (19), sin2 θ' and (1/i)_ab-1/i_ca) The same sign, cos2 θ' and (2/i)_bc-1/i_ab-1/i_ca) The symbols are the same. In addition, since the stator magnetic field formed by the reference voltage vector is aligned with the axial direction of the a-phase winding, that is, θ ' is equal to θ ', the direction of the rotor d-axis with respect to the reference voltage vector needs to be known in the vector control of the permanent magnet synchronous motor, and the value of θ ' calculated by equation (19) is the value of the rotor position angle θ in the SVPWM control.

Rotor magnetic pole position identification under delta connection

The positive direction of current flow for a delta connection is specified as shown in fig. 5.

When S is₄Conduction, S₂/S₃/S₅/S₆Off, S₁In order to block the C phase, only the A and B phases output the pulse width modulated DC voltage U_ab. At this time, phase B is connected in series with phase C and then in parallel with phase A in the opposite direction. The relationship between the phases of the currents is:

i_ab＝i_a-i_b，i_b＝i_c(22)

from the A-phase branch, the voltage vector U_abThe relationship to current and inductance is:

from the B, C phase series branch, the voltage vector U_abThe relationship to current and inductance is:

by formulae (23) and (24) to remove i_aAnd simplifying to obtain U_abAnd i_abHas the relation of

Therefore, under the delta connection, U is applied_abInductance L between two ends of time voltage_abAnd a resistor R_abRespectively as follows:

voltage vector U same as Y-connection_abCorresponding to the added resistance R_abAnd an inductance L_abCurrent response i across the series first order circuit_abThe expression of (a) is:

substituting the self inductance and mutual inductance formula of the stator winding into L_abExpression of, having

Similarly, when a voltage vector U is applied_bcBlocking phase A, and applying voltage vector U_caWhen B phase is blocked, respectively deducing L_bcAnd L_caCan obtain the product

Setting DC bus voltage as U_dc，U_ab、U_bc、U_caThe duty cycles of (a) and (b) are all D, and the current rise times are all t, which is sufficiently small. The magnitude of the inter-phase current at time t is

According to i_ab、i_bcAnd i_caThe expression (c) can solve for the rotor position angle θ:

in the vector control of the PMSM, it is necessary to grasp the rotor position θ with respect to the reference voltage vector, and when Δ -type connection is performed, the stator magnetic field formed by the reference voltage vector lags the a-phase winding by 30 °, that is, θ -30 °. Therefore, formula (33) is substituted with θ' -30 °, and a calculation formula of the rotor position θ that we need can be obtained. Comparing equation (18) and equation (32), it can be seen that θ can still be directly determined by equation (19), that is, equation (19) applies to both Y-type and Δ -type wirings.

Therefore, the calculation formula of the split-phase injection method is the formula (19) under the Y-type connection or the delta-type connection, and the pressurizing, measuring and calculating processes are as follows:

(1)S₁chopping control with duty ratio D, S₄Conduction, S₂/S₃/S₅/S₆Is turned off to output a pulse width modulated direct voltage U_abAnd blocking phase C. After the time t, measuring the current i of the A phase or the B phase_ab；

(2)S₃Chopping control with duty ratio D, S₆Conduction, S₁/S₂/S₄/S₅Is turned off to output a pulse width modulated direct voltage U_bcBlocking phase A. After the time t, measuring the current i of the B phase or the C phase_bc；

(3)S₅Chopping control with duty ratio D, S₂Conduction, S₁/S₃/S₄/S₆Is turned off to output a pulse width modulated direct voltage U_caAnd blocking phase B. After the time t, measuring the current i of the C phase or the A phase_ca；

(4) Will measure i_ab、i_bcAnd i_caThe rotor position angle θ is calculated by substituting equation (19) and table 1.

According to the function analysis of the controller, the rotor position detection needs to provide position angle information for the offline parameter identification, so that the rotor position detection is used as the offline identification function of the first operation after the system is started and initialized. According to the implementation process of the split-phase injection method, the initial position identification mainly comprises the following steps:

1) initializing parameters: u applied as required_ab、U_bc、U_caAnd the DC bus voltage U output by the rectifying circuit_dcThe voltage duty ratio D is set so that the switch count value in one PWM period is calculated as the switch count value of the applied chopper voltage. And calculating the number of cycles required to pass by the current AD sampling according to the required current rising time and the control cycle of the controller.

2) Voltage application and current sampling: first applying a voltage U_ab. The upper bridge arm of the phase A performs chopping output, and the lower bridge arm is blocked; the lower bridge arm of the phase B is conducted, and the upper bridge arm is blocked; and C-phase upper and lower bridge arms are blocked. After the time t is applied, the current i is sampled_abAnd the bridge arm on the phase A is blocked, so that the voltages of three ends of the motor ABC are all 0. After a period of time, the current between the AB phases is reduced to 0, the next voltage vector can be continuously applied and current sampling is carried out, and the like, until three times of current sampling are completed.

3) Calculating the axial position of the rotor: mentioned in this chapterA rotor magnetic pole position detection method using i_ab、i_bcAnd i_caThe angle theta of the rotor axial direction is calculated.

4) And (3) identifying the polarity of the rotor: respectively calculating and applying a resultant voltage vector U at the axial position theta identified in the previous step and the opposite direction theta + pi thereof_θAnd U_θ+πTo obtain a current vector I_θAnd I_θ+π. According to the magnetic saturation effect, when the d-axis current is positive, the magnetic poles of the rotor are in a magnetizing state, and the current rises quickly; when the d-axis current is negative, the magnetic poles of the rotor are in a demagnetized state, and the current rises slowly. Thus, I_θAnd I_θ+πThe angle corresponding to the one with the larger median is the angle of the rotor N pole.

The software flow chart is shown in fig. 6.

In a second aspect, as shown in fig. 7, an embodiment of the present invention provides a device for detecting an initial position of a rotor of a permanent magnet synchronous motor, including:

the pressurizing module 71 is used for respectively blocking the output of any one of the three phases and selectively pressurizing the three-phase winding by the other two phases;

the current sampling module 72 is configured to perform current sampling respectively after the pressurization is finished, so as to obtain a first sampling current, a second sampling current, and a third sampling current;

and the position determining module 73 is used for determining the axial position of the magnetic pole of the rotor according to the first sampling current, the second sampling current and the third sampling current based on a magnetic pole axial angle calculation formula.

Preferably, the pressurization module 71 is configured to respectively block an output of any one of the three phases, and selectively pressurize the three-phase winding by the remaining two phases, specifically: if the three-phase winding adopts a Y-type wiring mode, the C phase is blocked, and only the A phase and the B phase output pulse width modulation direct current voltage U_abThe windings of the A phase and the B phase are reversely connected in series for electrifying, the A phase and the B phase are blocked in sequence by the same principle, and the corresponding voltage U is output_bcAnd U_ca(ii) a If the three-phase winding adopts a delta connection mode, the output U is_abThe series circuit corresponding to the B-phase winding and the C-phase winding is reversely connected in parallel with the A-phase winding, and the U is sequentially output in the same way_bcAnd U_ca。

Preferably, in the current sampling module 72: after pressurization is finished, current sampling is respectively carried out to obtain a first sampling current, a second sampling current and a third sampling current, and the method specifically comprises the following steps: if the pressurizing time length T is reached, the pressurizing is finished, and the three-phase winding adopts a Y-shaped wiring mode, the first sampling current I_ab≈DU_dcT/[3L₀+3L₁cos 2(θ′+30°)]Second sampling current I_bc≈DU_dcT/(3L₀-3L₁cos2 θ'), third sampled current I_ca≈DU_dcT/[3L₀+3L₁cos 2(θ′-30°)](ii) a If the three-phase winding adopts a delta connection mode, the first sampling current I_ab≈DU_dcT/(L₀+L₁cos2 θ'), second sampled current I_bc≈DU_dcT/[L₀+L₁cos 2(θ′+60°)]Third sampling current I_ca≈DU_dcT/[L₀+L₁cos 2(θ′-60°)]Wherein L is₀Being a constant component of inductance, L₁The component of inductance change caused by the saliency, D is the on duty ratio, U_dcIs the DC bus voltage, L, of the frequency converter_abIs the corresponding equivalent inductance.

Preferably, the position determining module 73 is configured to determine the axial position of the rotor magnetic pole according to the first sampling current, the second sampling current, and the third sampling current based on a magnetic pole axial angle calculation formula, specifically: by the formula

The rotor pole axial position is determined.

In a third aspect, an embodiment of the present invention provides a frequency converter, including: one or more processors, one or more memories; the one or more memories are coupled to the one or more processors and the one or more memories are configured to store computer program code comprising computer instructions that, when executed by the one or more processors, cause the frequency converter to perform the method for detecting an initial position of a rotor of a PMSM as described above.

The memory may be, but is not limited to, a read-only memory (ROM) or other type of static storage device that may store static information and instructions, a Random Access Memory (RAM) or other type of dynamic storage device that may store information and instructions, an electrically erasable programmable read-only memory (EEPROM), a compact disc read-only memory (CD-ROM) or other optical disc storage, optical disc storage (including compact disc, laser disc, optical disc, digital versatile disc, blu-ray disc, etc.), magnetic disk storage media or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer. The memory may be self-contained and coupled to the processor via a bus. The memory may also be integral to the processor.

The memory is used for storing application program codes for executing the scheme of the application and is controlled by the processor to execute. The processor is configured to execute the application code stored in the memory to implement the functions of the method of the present patent.

In particular implementations, a processor may include one or more CPUs, as one embodiment.

In particular implementations, the terminal may include multiple processors, as one embodiment. Each of these processors may be a single-core (single-CPU) processor or a multi-core (multi-CPU) processor. A processor herein may refer to one or more devices, circuits, and/or processing cores for processing data (e.g., computer program instructions).

In a fourth aspect, an embodiment of the present invention provides a computer storage medium, on which computer instructions are stored, and when the computer instructions are run on a terminal, the terminal is caused to execute the method for detecting the initial position of the rotor of the permanent magnet synchronous motor.

The embodiments of the present invention have been described in detail with reference to the accompanying drawings, but the present invention is not limited to the described embodiments. It will be apparent to those skilled in the art that various changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, and the scope of protection is still within the scope of the invention.