CN103701395B - A kind of rotor initial position method of estimation based on positive and negative sequence harmonic injection - Google Patents

Abstract

The invention discloses a kind of rotor initial position method of estimation based on positive and negative sequence harmonic injection, the method improve the estimated angle error that traditional rotation high-frequency signal injection estimation d shaft position produces, comprise the nonlinear characteristic of stator resistance and Inverter Dead-time, equally also analyze wire time time delay, impact that filtering delay-time is estimated initial position of rotor, therefore can make the initial d shaft position estimation of rotor more accurately, fast and stable; The recycling estimation magnetic saturation effect obtained on d axle distinguishes the polarity of permanent magnet pole, finally obtains rotor initial angle accurately.The inventive method implements simply, and has very strong antijamming capability, can more accurately, the initial position recording rotor of fast and stable.

Description

A kind of rotor initial position method of estimation based on positive and negative sequence harmonic injection

Technical field

The invention belongs to technical field of motors, be specifically related to a kind of rotor initial position method of estimation based on positive and negative sequence harmonic injection.

Background technology

Accurately will control the motion state of permagnetic synchronous motor, need the rotor-position signal knowing that motor is real-time, therefore traditional magneto generally adopts additional position transducer, is used for detection rotor position.But adopt position transducer to not only increase the complexity of cost and electric machine structure, and in some high temperature, high pressure or severe corrosive environment, position transducer can reduce the reliability of system or transducer cannot normally work.Therefore, the position Sensorless Control realizing permanent magnet synchronous motor has become one of important directions of permanent magnet motor control technology development in recent years.At present, the position Sensorless Control of permanent magnet motor adopts back-EMF determination method, high frequency signal injection method or flux observer method etc. mostly.

Publication number is that a kind of method by detecting back-emf zero crossing that patent discloses of CN1286525 is used for determining rotor-position, and its antijamming capability is strong, and position probing is accurate, but several specific positions of back-emf zero crossing can only be detected.And for example publication number is the defining method that patent discloses a kind of rotor-position of CN101534088, it is by Harmonic injection component, rotor-position signal is drawn through complicated treatment circuit, but its antijamming capability is more weak, simultaneously because extracted high order harmonic component amount is less, higher to the requirement of signal processing circuit, and also there is larger error in result.

Utilize the method for flux observer principle detection rotor position signalling to obtain very large development in recent years, its main advantage is to obtain continuous print rotor-position signal, and for the advanced algorithm such as vector control, direct torque control, this is very important.Compared with Harmonic Injection Method, flux observer method does not need complicated modulate circuit just can obtain relatively accurate rotor position angle, and the antijamming capability of circuit is also improved.But existing magneto flux observer is mainly based on stator rest frame, as the method that publication number is disclosed in CN202059359U and CN102340278A, all be through computing permanent magnet flux linkage component in stator magnetic linkage is resolved out, thus continuous print rotor-position signal can be calculated.This method is comparatively extensive in the application of the Sensorless Control Technique field of motor, and technology is also comparatively ripe, but the intermediate quantity in computational process is of ac, to the computational speed of processor and required precision all higher, easily affect by intermediate link filter amplitude-frequency characteristic and phase-frequency characteristic.This algorithm is for non-salient pole permanent magnet motor, computational process is comparatively simple, and easily realize, intermediate computations link also can simplify, but for salient pole machine, need in computational process to estimate rotor-position roughly in advance, then estimated value is corrected, considerably increase amount of calculation thus, and increase the error of observed result, computational process required time increases simultaneously, makes the bad dynamic performance of control system.Flux observer in pilot process in order to eliminate the impact of noise that electromagnetic interference is introduced, general meeting suitably adds some filters, the rotor-position signal that these filters can obtain the observer observation station of this principle causes error in various degree, and along with the difference of load and rotating speed and the error produced in various degree.

Summary of the invention

For the above-mentioned technical problem existing for prior art, the invention provides a kind of rotor initial position method of estimation based on positive and negative sequence harmonic injection, can more accurately, the initial position recording rotor of fast and stable.

Based on a rotor initial position method of estimation for positive and negative sequence harmonic injection, comprise the steps:

(1) injecting amplitude to motor stator winding is V _cangular frequency is w _cforward harmonic voltage; Through static alpha-beta coordinate system transformation to synchronous rotary d-q coordinate system, obtain the voltage vector V of forward harmonic voltage under synchronous rotary d-q coordinate system _dq;

(2) according to voltage vector V _dq, calculate and try to achieve the current phasor I of motor stator electric current under synchronous rotary d-q coordinate system _dq;

(3) through synchronous rotary d-q coordinate system transformation extremely static alpha-beta coordinate system, the current phasor I of stator current under static alpha-beta coordinate system is obtained _{α β};

(4) from current phasor I _{α β}in extract electric current negative sequence component to electric current negative sequence component carry out low-pass filtering successively and rotate demodulation obtaining electric current negative sequence component

(5) according to electric current negative sequence component negative phase-sequence phase theta is obtained by following relational expression arctangent computation ₁;

$\begin{array}{cc}{I}_{\mathrm{\α}\mathrm{\β}2}^{-}=I_{cp}{e}^{{\mathrm{j\θ}}_1}& I_{cp}=\sqrt{{I_{R2}}^2+{I_{R1}}^2}\end{array}$

$\begin{array}{cc}{I}_{R1}=\frac{I_{r1}}{2}+\frac{I_{r3}}{2}& I_{R2}=\frac{I_{r2}}{2}+\frac{I_{r4}}{2}\end{array}$

$\begin{array}{cccc}{I}_{r1}=\frac{V_c\·r}{r^2+{L_d}^2{w_c}^2}& I_{r2}=\frac{V_c\·L_d\·w_c}{r^2+{L_d}^2{w_c}^2}& I_{r3}=\frac{V_c\·r}{r^2+{L_q}^2{w_c}^2}& I_{r4}=\frac{V_c\·L_q\·w_c}{r^2+{L_q}^2{w_c}^2}\end{array}$

Wherein: L _dand L _qbe respectively the d axle inductive component of motor stator inductance under synchronous rotary d-q coordinate system and q axle inductive component, r is stator resistance, and j is imaginary unit;

(6) inject the negative sense harmonic voltage of identical amplitude same angular frequency to motor stator winding, in like manner calculate the current phasor I of stator current under static alpha-beta coordinate system according to step (1) to (5) _{α β}and therefrom extract electric current positive sequence component and then to electric current positive sequence component carry out low-pass filtering and rotate demodulation obtaining electric current positive sequence component according to electric current positive sequence component pass through relational expression arctangent computation obtains positive sequence phase theta ₂;

(7) according to following relational expression, the angle theta of synchronous rotary d-q coordinate system d axle and static alpha-beta coordinate system α axle is determined:

If θ ₁>=θ ₂, then θ=0.5* [θ ₁-0.5* (θ ₁-θ ₂)];

If θ ₁< θ ₂, then θ=0.5* [θ ₁+ π-0.5* (θ ₁+ π-θ ₂)];

(8) according to angle theta, distinguished the polarity of permanent magnet pole by the magnetic saturation effect on d axle, and then determine the rotor initial angle of motor.

In described step (1), calculate the voltage vector V of forward harmonic voltage under synchronous rotary d-q coordinate system according to following formula _dq:

$\left\{\begin{array}{c}{V}_d=V_{c}cos(w_{c}t-\mathrm{\&theta;})\\ V_q=V_{c}sin(w_{c}t-\mathrm{\&theta;})\end{array}\right.$

Wherein: voltage vector V _dqcomprise d shaft voltage component V _dwith q shaft voltage component V _q, t is the time.

In described step (2), calculate the current phasor I of motor stator electric current under synchronous rotary d-q coordinate system according to following formula _dq:

$\left\{\begin{array}{c}{I}_d=\frac{V_c\&CenterDot;r}{r^2+{L_d}^2{w_c}^2}\cos (w_{c}t-\mathrm{\&theta;})+\frac{V_c\&CenterDot;L_d\&CenterDot;w_c}{r^2+{L_d}^2{w_c}^2}\sin (w_{c}t-\mathrm{\&theta;})\\ I_q=\frac{V_c\&CenterDot;r}{r^2+{L_q}^2{w_c}^2}\sin (w_{c}t-\mathrm{\&theta;})-\frac{V_c\&CenterDot;L_q\&CenterDot;w_c}{r^2+{L_q}^2{w_c}^2}\cos (w_{c}t-\mathrm{\&theta;})\end{array}\right.$

Wherein: current phasor I _dqcomprise d shaft current component I _dwith q shaft current component I _q, t is the time.

In described step (3), calculate the current phasor I of stator current under static alpha-beta coordinate system according to following formula _{α β}:

$I_{cn}=\sqrt{{I_{R3}}^2+{I_{R4}}^2}$

$\begin{array}{cc}{I}_{R3}=\frac{I_{r1}}{2}-\frac{I_{r3}}{2}& I_{R4}=\frac{I_{r2}}{2}-\frac{I_{r4}}{2}\end{array}$

Wherein: t is the time.

In described step (4) according to following formula from current phasor I _{α β}in extract electric current negative sequence component

$I_{\mathrm{\&alpha;}\mathrm{\&beta;}}^{-}=I_{\mathrm{\&alpha;}\mathrm{\&beta;}}\&CenterDot;e^{-w_{c}t}$

Wherein: t is the time.

In described step (4) according to following formula to electric current negative sequence component carry out low-pass filtering:

$I_{cn}=\sqrt{{I_{R3}}^2+{I_{R4}}^2}$

$\begin{array}{cc}{I}_{R3}=\frac{I_{r1}}{2}-\frac{I_{r3}}{2}& I_{R4}=\frac{I_{r2}}{2}-\frac{I_{r4}}{2}\end{array}$

Wherein: for the electric current negative sequence component after low-pass filtering, t is the time.

Carry out rotation demodulation according to following formula in described step (4) and obtain electric current negative sequence component

$I_{\mathrm{\&alpha;}\mathrm{\&beta;}2}^{-}=I_{\mathrm{\&alpha;}\mathrm{\&beta;}1}^{-}\&CenterDot;e^{2w_{c}t}$

Wherein: for the electric current negative sequence component after low-pass filtering, t is the time.

Rotor initial position method of estimation of the present invention improves the estimated angle error that traditional rotation high-frequency signal injection estimation d shaft position produces, comprise the nonlinear characteristic of stator resistance and Inverter Dead-time, equally also analyze wire time time delay, impact that filtering delay-time is estimated initial position of rotor, therefore can make the initial d shaft position estimation of rotor more accurately, fast and stable; The recycling estimation magnetic saturation effect obtained on d axle distinguishes the polarity of permanent magnet pole, finally obtains rotor initial angle accurately.The inventive method implements simply, and has very strong antijamming capability, can more accurately, the initial position recording rotor of fast and stable.

Accompanying drawing explanation

Fig. 1 is the steps flow chart schematic diagram of rotor initial position method of estimation of the present invention.

Embodiment

In order to more specifically describe the present invention, below in conjunction with the drawings and the specific embodiments, technical scheme of the present invention is described in detail.

For a three-phase permanent magnet synchronous motor, this parameter of electric machine is as shown in table 1:

Table 1

Rated power (W)	1500
		Rated speed (rpm)	1000
Nominal torque (N*m)	14.3
		Rated current (A)	3.8
Winding connection	Y type
		Phase resistance R s(Ω)	2.15
D-axis inductance L d(H)	0.0632
		Quadrature axis inductance L q(H)	0.0919
Permanent magnet equivalence magnetic linkage (Wb)	0.5

As shown in Figure 1, this rotor initial position method of estimation, comprises the steps:

(1) injecting amplitude to motor stator winding is V _cangular frequency is w _cforward harmonic voltage (namely applying the magnetic field be rotated counterclockwise to motor); Through static alpha-beta coordinate system transformation to synchronous rotary d-q coordinate system, obtain the voltage vector V of forward harmonic voltage under synchronous rotary d-q coordinate system _dq;

The voltage vector V of forward harmonic voltage under static alpha-beta coordinate system _{α β}as follows:

$\left\{\begin{array}{c}{V}_{\mathrm{\&alpha;}}=V_{c}cos\left(w_{c}t\right)\\ V_{\mathrm{\&beta;}}=V_{c}sin\left(w_{c}t\right)\end{array}\right.$

For voltage vector V _{α β}, make static alpha-beta coordinate system transformation to synchronous rotary d-q coordinate system according to following relational expression:

$\left\{\begin{array}{c}{V}_d=V_{\mathrm{\&alpha;}}cos\mathrm{\&theta;}+V_{\mathrm{\&beta;}}sin\mathrm{\&theta;}\\ V_q=V_{\mathrm{\&alpha;}}(-sin\mathrm{\&theta;})+V_{\mathrm{\&beta;}}cos\mathrm{\&theta;}\end{array}\right.$

Obtain the voltage vector V of forward harmonic voltage under synchronous rotary d-q coordinate system _dqas follows:

$\left\{\begin{array}{c}{V}_d=V_{c}cos(w_{c}t-\mathrm{\&theta;})\\ V_q=V_{c}sin(w_{c}t-\mathrm{\&theta;})\end{array}\right.$

Wherein: θ is the angle of synchronous rotary d-q coordinate system d axle and static alpha-beta coordinate system α axle.

(2) due to voltage vector V _dqfollowing relation is there is with motor stator electric current:

$\left\{\begin{array}{c}{V}_d=V_{c}cos(w_{c}t-\mathrm{\&theta;})=r\&CenterDot;I_d+L_d\frac{{\mathrm{dI}}_d}{dt}\\ V_q=V_{c}sin(w_{c}t-\mathrm{\&theta;})=r\&CenterDot;I_q+L_q\frac{{\mathrm{dI}}_q}{dt}\end{array}\right.$

Wherein: L _dand L _qbe respectively the d axle inductive component of motor stator inductance under synchronous rotary d-q coordinate system and q axle inductive component, r is stator resistance;

Consider when motor stable state, above formula is solved and obtains the current phasor I of motor stator electric current under synchronous rotary d-q coordinate system _dqas follows:

$\left\{\begin{array}{c}{I}_d=\frac{V_c\&CenterDot;r}{r^2+{L_d}^2{w_c}^2}\cos (w_{c}t-\mathrm{\&theta;})+\frac{V_c\&CenterDot;L_d\&CenterDot;w_c}{r^2+{L_d}^2{w_c}^2}\sin (w_{c}t-\mathrm{\&theta;})\\ I_q=\frac{V_c\&CenterDot;r}{r^2+{L_q}^2{w_c}^2}\sin (w_{c}t-\mathrm{\&theta;})-\frac{V_c\&CenterDot;L_q\&CenterDot;w_c}{r^2+{L_q}^2{w_c}^2}\cos (w_{c}t-\mathrm{\&theta;})\end{array}\right.$

(3) through synchronous rotary d-q coordinate system transformation extremely static alpha-beta coordinate system, the current phasor I of stator current under static alpha-beta coordinate system is obtained _{α β}:

$\begin{array}{c}{I}_{\mathrm{\&alpha;}\mathrm{\&beta;}}=I_{dq}\&CenterDot;e^{j\mathrm{\&theta;}}\\ =(\frac{I_{r1}}{2}+\frac{I_{r3}}{2})e^{{\mathrm{jw}}_{c}t}+(\frac{I_{r1}}{2}-\frac{I_{r3}}{2})e^{j(2\mathrm{\&theta;}-w_{c}t)}+(\frac{I_{r2}}{2}+\frac{I_{r4}}{2})e^{j(w_{c}t-\frac{\mathrm{\&pi;}}{2})}+(\frac{I_{r2}}{2}\\ -\frac{I_{r4}}{2})e^{j(2\mathrm{\&theta;}-w_{c}t+\frac{\mathrm{\&pi;}}{2})}\end{array}$

Wherein: $I_{r1}=\frac{V_c\&CenterDot;r}{r^2+{L_d}^2{w_c}^2},I_{r2}=\frac{V_c\&CenterDot;L_d\&CenterDot;w_c}{r^2+{L_d}^2{w_c}^2},I_{r3}=\frac{V_c\&CenterDot;r}{r^2+{L_q}^2{w_c}^2},I_{r4}=\frac{V_c\&CenterDot;L_q\&CenterDot;w_c}{r^2+{L_q}^2{w_c}^2};$

Order: $I_{R1}=\frac{I_{r1}}{2}+\frac{I_{r3}}{2},I_{R2}=\frac{I_{r2}}{2}+\frac{I_{r4}}{2},I_{R3}=\frac{I_{r1}}{2}-\frac{I_{r3}}{2},I_{R4}=\frac{I_{r2}}{2}-\frac{I_{r4}}{2};$

Then

Wherein: $I_{cp}=\sqrt{{I_{R2}}^2+{I_{R1}}^2},I_{cn}=\sqrt{{I_{R3}}^2+{I_{R4}}^2},$

Stator current vector can regard a positive sequence component be rotated counterclockwise and a negative sequence component turned clockwise as, and the positional information of rotor is all positioned on negative sequence component as can be seen here.

(4) according to following formula from current phasor I _{α β}in extract electric current negative sequence component

Then, according to following formula to electric current negative sequence component carry out low-pass filtering to obtain:

Finally, according to following formula to the electric current negative sequence component after low-pass filtering carry out rotation demodulation and obtain electric current negative sequence component

$I_{\mathrm{\&alpha;}\mathrm{\&beta;}2}^{-}=I_{\mathrm{\&alpha;}\mathrm{\&beta;}1}^{-}\&CenterDot;e^{2w_{c}t}$

(5) according to electric current negative sequence component negative phase-sequence phase theta is obtained by following relational expression arctangent computation ₁;

Wherein: can change along with parameter of electric machine change, and dead band is on its impact.

(6) injecting amplitude to motor stator winding is V _cangular frequency is w _cnegative sense harmonic voltage (namely applying the magnetic field turned clockwise to motor); The voltage vector V of negative sense harmonic voltage under static alpha-beta coordinate system _{α β}as follows:

$\left\{\begin{array}{c}{V}_{\mathrm{\&alpha;}}=V_{c}cos(-w_{c}t)\\ V_{\mathrm{\&beta;}}=V_{c}sin(-w_{c}t)\end{array}\right.$

Through static alpha-beta coordinate system transformation to synchronous rotary d-q coordinate system, obtain the voltage vector V of negative sense harmonic voltage under synchronous rotary d-q coordinate system _dqas follows:

$\left\{\begin{array}{c}{V}_d=V_{c}cos(-w_{c}t-\mathrm{\&theta;})\\ V_q=V_{c}sin(-w_{c}t-\mathrm{\&theta;})\end{array}\right.$

(7) due to voltage vector V _dqfollowing relation is there is with motor stator electric current:

$\left\{\begin{array}{c}{V}_d=V_{c}cos(-w_{c}t-\mathrm{\&theta;})=r\&CenterDot;I_d+L_d\frac{{\mathrm{dI}}_d}{dt}\\ V_q=V_{c}sin(-w_{c}t-\mathrm{\&theta;})=r\&CenterDot;I_q+L_q\frac{{\mathrm{dI}}_q}{dt}\end{array}\right.$

Consider when motor stable state, above formula is solved and obtains the current phasor I of motor stator electric current under synchronous rotary d-q coordinate system _dqas follows:

$\left\{\begin{array}{c}{I}_d=\frac{V_c\&CenterDot;r}{r^2+{L_d}^2{w_c}^2}\cos (-w_{c}t-\mathrm{\&theta;})+\frac{V_c\&CenterDot;L_d\&CenterDot;w_c}{r^2+{L_d}^2{w_c}^2}\sin (-w_{c}t-\mathrm{\&theta;})\\ I_q=\frac{V_c\&CenterDot;r}{r^2+{L_q}^2{w_c}^2}\sin (-w_{c}t-\mathrm{\&theta;})-\frac{V_c\&CenterDot;L_q\&CenterDot;w_c}{r^2+{L_q}^2{w_c}^2}\cos (-w_{c}t-\mathrm{\&theta;})\end{array}\right.$

(8) through synchronous rotary d-q coordinate system transformation extremely static alpha-beta coordinate system, the current phasor I of stator current under static alpha-beta coordinate system is obtained _{α β}:

The positional information of rotor is all positioned in positive sequence component as can be seen here.

(9) according to following formula from current phasor I _{α β}in extract electric current positive sequence component

Then, according to following formula to electric current positive sequence component carry out low-pass filtering to obtain:

Finally, according to following formula to the electric current positive sequence component after low-pass filtering carry out rotation demodulation and obtain electric current positive sequence component

$I_{\mathrm{\&alpha;}\mathrm{\&beta;}2}^{+}=I_{\mathrm{\&alpha;}\mathrm{\&beta;}1}^{+}\&CenterDot;e^{2w_{c}t}$

(10) according to electric current positive sequence component positive sequence phase theta is obtained by following relational expression arctangent computation ₂;

(11) known: at θ ₁, θ ₂in expression formula, expression formula be consistent, namely affect factor be consistent, after twice process above value be identical, and within 0 to 90 degree, so θ in theory ₁> θ ₂; Judge so permanent-magnetic synchronous motor rotor initial position can be normalized within the scope of 0 to 180 degree.

According to following relational expression, determine the angle theta of synchronous rotary d-q coordinate system d axle and static alpha-beta coordinate system α axle:

If θ ₁>=θ ₂, then θ=0.5* [θ ₁-0.5* (θ ₁-θ ₂)];

If θ ₁< θ ₂, then θ=0.5* [θ ₁+ π-0.5* (θ ₁+ π-θ ₂)];

(12) according to angle theta, distinguished the polarity of permanent magnet pole by the magnetic saturation effect on d axle, and then determine the rotor initial angle of motor.

Given positive and negative square-wave voltage on θ direction, detects the peak value of feedback current, if forward gives timing current peak than oppositely large to timing, then θ is the rotor initial angle of motor; If oppositely give timing current peak larger to timing than forward, then θ differs 180 ° with the rotor initial angle of motor.

We verify present embodiment by experiment, and its result is as shown in table 2, and the rotor initial angle of angle theta and motor exists above-mentioned relation really as can be seen from Table 2, and deviation is very little.

Table 2

The rotor initial angle of setting	Angle theta
		0	0
10	10.1125
		20	20.5500
30	31.2175
		40	41.5000
50	51.0875
		60	60.5325
70	70.0450
		80	80.0500
90	90.0000
		100	99.9500
110	109.9500
		120	119.4675
130	128.9125
		140	138.5000
150	148.7825
		160	159.4450
170	169.8875
		180	-0.0025
190	10.1125
		200	20.5500
210	31.2175
		220	41.5000
230	51.0875
		240	60.5325
250	70.0400
		260	80.0500
270	90.0000
		280	99.9500
290	109.9550
		300	119.4675
310	128.9155
		320	138.5000
330	148.7850
		340	159.4450
350	169.8875
		360	-0.0025

Claims (7)

1., based on a rotor initial position method of estimation for positive and negative sequence harmonic injection, comprise the steps:

(1) injecting amplitude to motor stator winding is V _cangular frequency is w _cforward harmonic voltage; Through static alpha-beta coordinate system transformation to synchronous rotary d-q coordinate system, obtain the voltage vector V of forward harmonic voltage under synchronous rotary d-q coordinate system _dq;

(2) according to voltage vector V _dq, calculate and try to achieve the current phasor I of motor stator electric current under synchronous rotary d-q coordinate system _dq;

(3) through synchronous rotary d-q coordinate system transformation extremely static alpha-beta coordinate system, the current phasor I of stator current under static alpha-beta coordinate system is obtained _{α β};

(4) from current phasor I _{α β}in extract electric current negative sequence component to electric current negative sequence component carry out low-pass filtering successively and rotate demodulation obtaining electric current negative sequence component

(5) according to electric current negative sequence component negative phase-sequence phase theta is obtained by following relational expression arctangent computation ₁;

$\begin{array}{cc}{I}_{\mathrm{\&alpha;\&beta;}2}^{-}=I_{\mathrm{cp}}{e}^{j{\mathrm{\&theta;}}_1}& I_{\mathrm{cp}}=\end{array}\sqrt{I_{}{{R2}_{}}^2+{I_{R1}}^2}$

$\begin{array}{cc}{I}_{R1}=\frac{I_{r1}}{2}+\frac{I_{r3}}{2}& I_{R2}=\frac{I_{r2}}{2}+\frac{I_{r2}}{2}+\frac{I_{r4}}{2}\end{array}$

$\begin{array}{cccc}{I}_{r1}=\frac{V_c\&CenterDot;r}{r^2+{L_d}^2{w_c}^2}& I_{r2}=\frac{V_c\&CenterDot;L_d\&CenterDot;w_c}{r^2+{L_d}^2{w_c}^2}& I_{r3}=\frac{V_c\&CenterDot;r}{r^2+{L_q}^2{w_c}^2}& I_{r4}=\frac{V_c\&CenterDot;L_q\&CenterDot;w_c}{r^2+{L_q}^2{w_c}^2}\end{array}$

Wherein: L _dand L _qbe respectively the d axle inductive component of motor stator inductance under synchronous rotary d-q coordinate system and q axle inductive component, r is stator resistance, and j is imaginary unit;

(6) inject the negative sense harmonic voltage of identical amplitude same angular frequency to motor stator winding, in like manner calculate the current phasor I of stator current under static alpha-beta coordinate system according to step (1) to (5) _{α β}and therefrom extract electric current positive sequence component and then to electric current positive sequence component carry out low-pass filtering and rotate demodulation obtaining electric current positive sequence component according to electric current positive sequence component pass through relational expression arctangent computation obtains positive sequence phase theta ₂;

(7) according to following relational expression, the angle theta of synchronous rotary d-q coordinate system d axle and static alpha-beta coordinate system α axle is determined:

If θ ₁>=θ ₂, then θ=0.5* [θ ₁-0.5* (θ ₁-θ ₂)];

If θ ₁≤ θ ₂, then θ=0.5* [θ ₁+ π-0.5* (θ ₁+ π-θ ₂)];

(8) according to angle theta, distinguished the polarity of permanent magnet pole by the magnetic saturation effect on d axle, and then determine the rotor initial angle of motor.

2. rotor initial position method of estimation according to claim 1, is characterized in that: in described step (1), calculates the voltage vector V of forward harmonic voltage under synchronous rotary d-q coordinate system according to following formula _dq:

$\left\{\begin{array}{c}{V}_d=V_c\cos (w_{c}t-\mathrm{\&theta;})\\ V_q=V_c\sin (w_{c}t-\mathrm{\&theta;})\end{array}\right.$

Wherein: voltage vector V _dqcomprise d shaft voltage component V _dwith q shaft voltage component V _q, t is the time.

3. rotor initial position method of estimation according to claim 1, is characterized in that: in described step (2), calculates the current phasor I of motor stator electric current under synchronous rotary d-q coordinate system according to following formula _dq:

$\left\{\begin{array}{c}{I}_d=\frac{V_c\&CenterDot;r}{r^2+{L_d}^2{w_c}^2}\cos (w_{c}t-\mathrm{\&theta;})+\frac{V_c\&CenterDot;L_d\&CenterDot;w_c}{r^2+{L_d}^2{w_c}^2}\sin (w_{c}t-\mathrm{\&theta;})\\ I_q=\frac{V_c\&CenterDot;r}{r^2+{L_q}^2{w_c}^2}\sin (w_{c}t-\mathrm{\&theta;})-\frac{V_c\&CenterDot;L_q\&CenterDot;w_c}{r^2+{L_q}^2{w_c}^2}\cos (w_{c}t-\mathrm{\&theta;})\end{array}\right.$

Wherein: current phasor I _dqcomprise d shaft current component I _dwith q shaft current component I _q, t is the time.

4. rotor initial position method of estimation according to claim 1, is characterized in that: in described step (3), calculates the current phasor I of stator current under static alpha-beta coordinate system according to following formula _{α β}:

Wherein: t is the time.

5. rotor initial position method of estimation according to claim 1, is characterized in that: in described step (4) according to following formula from current phasor I _{α β}in extract electric current negative sequence component

$I_{\mathrm{\&alpha;\&beta;}}^{-}=I_{\mathrm{\&alpha;\&beta;}}\&CenterDot;e^{-w_{c}t}$

Wherein: t is the time.

6. rotor initial position method of estimation according to claim 1, is characterized in that: in described step (4) according to following formula to electric current negative sequence component carry out low-pass filtering:

Wherein: for the electric current negative sequence component after low-pass filtering, t is the time.

7. rotor initial position method of estimation according to claim 1, is characterized in that: carry out rotation demodulation according to following formula in described step (4) and obtain electric current negative sequence component

$I_{\mathrm{\&alpha;\&beta;}2}^{-}=I_{\mathrm{\&alpha;\&beta;}1}^{-}\&CenterDot;e^{2w_{c}t}$

Wherein: for the electric current negative sequence component after low-pass filtering, t is the time.