Permanent magnet motor full-speed-domain position sensorless control method and system based on differentiating circuit

Abstract

The invention discloses a differential circuit-based permanent magnet motor full-speed-domain position-sensorless control method and system, and the method comprises the steps: setting a differential circuit, and enabling the differential circuit to be connected with a three-phase line of a permanent magnet motor through a current sensor; the method comprises the following steps: measuring three-phase current of a permanent magnet motor through a current sensor, inputting the three-phase current into a differentiating circuit, carrying out single sampling under the action of a zero voltage vector, and extracting a three-phase current differential value of the permanent magnet motor; and performing processing according to the three-phase current differential value of the permanent magnet motor under the action of the zero voltage vector, and inputting the three-phase current differential value into a normalized phase-locked loop to obtain position and rotating speed information of the permanent magnet motor. According to the method, parameter information such as inductance and resistance of the permanent magnet motor is not needed, accurate observation of the rotor position can be achieved only through single sampling in each switching period, and the method has good universality and robustness.

Description

Technical Field

[0001] The present invention relates to a position sensorless control technology for a permanent magnet synchronous motor, and in particular to a position sensorless control method and system for a permanent magnet motor in full speed range based on a differential circuit. Background Art

[0002] The field-oriented control of permanent magnet synchronous motors requires accurate rotor position information. The installation of mechanical position sensors will increase the system size and cost. Existing rotor position observation technologies usually design position observers based on motor models and rely on motor parameters such as inductance and resistance. When motor parameters change during operation, the position observation error will increase, thereby degrading the motor control performance.

[0003] In addition, the existing rotor position observation technology based on current differential obtains the current differential by multiple sampling and software calculation in a single switching cycle. It is easily interfered by sampling and calculation noise and can only be used in low-speed sections. It is not suitable for working conditions where the motor runs at high speed and the zero vector action time is short, which limits its practical application scope. Summary of the invention

[0004] The purpose of the present invention is to provide a full-speed range position sensorless control method and system for a permanent magnet motor based on a differential circuit, so as to solve the drawbacks of the prior art that the permanent magnet motor parameters such as inductance and resistance are dependent on the prior art, or that multiple sampling is required in a single switching cycle, making it difficult to apply in practice.

[0005] The technical solution to achieve the purpose of the present invention is:

[0006] A permanent magnet motor full-speed range position sensorless control method based on a differential circuit, comprising:

[0007] Step 1, build a three-phase differential circuit, the input ends of the three-phase differential circuit are respectively connected to the output ends of the current sensors of the three-phase current of the three-phase permanent magnet motor, and the output value of the three-phase differential circuit is obtained by single sampling under the action of the zero voltage vector, and the three-phase current differential value of the permanent magnet motor is obtained based on the output value of the three-phase differential circuit;

[0008] Step 2, performing coordinate transformation on the three-phase current differential value to obtain the current differential value of the permanent magnet motor in a stationary two-phase coordinate system;

[0009] Step 3, based on the current differential value of the permanent magnet motor in the stationary two-phase coordinate system, the rotor position and speed of the permanent magnet motor are obtained through a normalized phase-locked loop to achieve position sensorless control.

[0010] Furthermore, the output of the current sensor and the current value of the three-phase permanent magnet motor satisfy:

[0011] Usa =0.5V cc +k s i a , U sb =0.5V cc +k s i b , U sc =0.5V cc +k s i c

[0012] Among them, U sa , U sb , U sc is the output of the current sensor, i a 、i b 、i c is the current value of the three-phase a, b, c of the three-phase permanent magnet motor i a 、i b 、i c , V cc Supply voltage for current sensor, k s is the setting coefficient.

[0013] Furthermore, the three-phase differential circuit includes an operational amplifier, an input resistor R i , input capacitor C i and feedback resistor R f , input resistance R i One end is connected to the signal output end of the current sensor, and the output end is connected to the input capacitor C i One end is connected to the inverting input of the operational amplifier and the input capacitor C i The other end is connected, its in-phase input is grounded, and the output is connected through the feedback resistor R f Connected to the inverting input terminal, the output value of the output terminal satisfies:

[0014] U da =-R f C i *P sa , U db =-R f C i *P sb , U dc =-R f C i *P sc

[0015] Among them, U da , U db , U dc are the output values ​​of the three-phase differential circuit respectively, and p is the differential operator.

[0016] Furthermore, the three-phase current differential value is:

[0017] pi a =-U da / (k s R f C i ), pi b =-U db / (k s R f C i ), pi c =-U dc / (k s R f C i ).

[0018] Furthermore, the current differential value of the permanent magnet motor in the stationary two-phase coordinate system is:

[0019] pi α =2 / 3*pi a -1 / 3*pi b -1 / 3*pi c

[0020] pi β =1.732 / 3*pi b -1.732 / 3*pi c

[0021] Among them, pi α With pi β They respectively represent the α-axis current differential value and the β-axis current differential value of the permanent magnet motor in a stationary two-phase coordinate system.

[0022] Furthermore, the normalized phase-locked loop is a proportional-integral controller and an integral link connected in series, the output of the proportional-integral controller is the rotor speed, and the output of the integral link is the rotor position.

[0023] Furthermore, the input of the proportional-integral controller is:

[0024] ε=pi α *cosθ e2 +pi β *sinθ e2

[0025] =A*sinθ e1 *cosθ e2 -A*cosθ e1 *sinθ e2

[0026] =A*sin(θ e1 -θ e2 )

[0027] Among them, θ e1 is the actual rotor position of the permanent magnet motor at the last moment, θ e2 is the estimated rotor position of the permanent magnet motor at the previous moment, A is the amplitude of the current differential signal, and ε is the input of the proportional-integral controller.

[0028] Furthermore, the output of the proportional-integral controller is:

[0029]

[0030] Among them, ω e is the rotation speed, k p and k i are the proportional coefficient and the integral coefficient respectively, and s represents the complex variable in the Laplace domain.

[0031] A permanent magnet motor full-speed range position sensorless control system based on a differential circuit, comprising:

[0032] A current sensor is connected to the three-phase permanent magnet motor to measure the three-phase current of the three-phase permanent magnet motor;

[0033] A three-phase differential circuit is connected to the output end of the current sensor, and a single sampling is performed under the action of a zero voltage vector to obtain an output value of the three-phase differential circuit;

[0034] A three-phase current differential value solving unit is used to solve the three-phase current differential value of the permanent magnet motor based on the output value of the three-phase differential circuit;

[0035] A coordinate transformation unit performs coordinate transformation on the three-phase current differential value to obtain the current differential value of the permanent magnet motor in a stationary two-phase coordinate system;

[0036] The rotor position and speed obtaining unit obtains the rotor position and speed of the permanent magnet motor based on the current differential value of the permanent magnet motor in a stationary two-phase coordinate system through a normalized phase-locked loop to achieve position sensorless control.

[0037] Compared with the prior art, the above technical solution conceived by the present invention has the following beneficial effects:

[0038] (1) The present invention discloses a permanent magnet motor full-speed range position sensorless control technology based on a differential circuit, in which the current differential signal is obtained through a hardware differential circuit, and a single sampling at the center point under a zero voltage vector can obtain the current differential signal; compared with the existing method of continuous multiple sampling under a zero voltage vector and then calculating the current differential through software, the technology described in the present invention requires a short sampling window time, has no special requirements for the zero voltage vector action length, can be applied at different speeds of the permanent magnet motor, and avoids the problem that the software calculation differential is easily affected by noise, and the estimated position error is small.

[0039] (2) The present invention discloses a permanent magnet motor full-speed sensorless control technology based on differential circuit, wherein the sampling method is to perform a single sampling in each switching cycle, and the sampling time is the center point under the zero voltage vector; the existing permanent magnet motor parameter identification method based on switch state function, wherein the sampling method is to perform two samplings in each switching cycle, and the sampling time is respectively located in the effective voltage vector action interval and the zero voltage vector action interval; after the sampling is completed, the technology disclosed in the present invention uses only the three-phase current differential value for software calculation, without the need for motor inductance, flux linkage, resistance and other parameters, and can maintain good calculation stability even after the parameters change during the operation of the motor; the existing permanent magnet motor parameter identification method based on switch state function uses the a-phase current differential value, and subsequent calculation can only be carried out under the premise that the permanent magnet motor rotor position information is known. The present invention focuses on the permanent magnet motor sensorless control technology, discovers the rotor position information contained in the current differential signal under the action of the zero voltage vector, and realizes the rotor position observation that does not depend on specific motor parameters by the normalized phase-locked loop. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is the signal sampling and position estimation flow chart.

[0041] Figure 2 This is a schematic diagram of a differential circuit.

[0042] Figure 3 Schematic diagram of a normalized phase-locked loop.

[0043] Figure 4 The waveform diagram of the differential current signal of the α-axis and β-axis of the permanent magnet motor under zero vector and the observed rotor position waveform diagram.

[0044] Figure 5 This is the change diagram of the rotor position error under sudden changes in speed and load. DETAILED DESCRIPTION

[0045] The preferred embodiments of the present invention are described in detail below so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more definite definition of the protection scope of the present invention.

[0046] The present invention provides a full-speed range position sensorless control method for a permanent magnet motor based on a differential circuit. In each switching cycle of the magnetic field oriented control, only a single sampling is required at the center position of the zero vector, and the rotor position can be calculated in real time without the need for motor parameters. A switching state model is established for a surface-mounted permanent magnet synchronous motor powered by an inverter, and a three-phase current differential signal under the action of a zero voltage vector is obtained by sampling the differential circuit. After coordinate transformation, a sine and cosine signal containing rotor position information is obtained in a stationary two-phase coordinate system, and the rotor position signal is input into a normalized phase-locked loop.

[0047] like Figure 1 As shown, the embodiment of the method of the present invention and its implementation process are as follows:

[0048] A surface-mount permanent magnet synchronous motor powered by a voltage source inverter is simulated. The motor and inverter parameters are as follows:

[0049] Table 1 Permanent magnet synchronous motor and inverter parameters

[0050]

[0051] 1) A differential circuit is set up. After measuring the three-phase current of the permanent magnet motor through a current sensor, the current is input into the differential circuit. A single sampling is performed at the center position of the zero voltage vector to extract the three-phase current differential value of the permanent magnet motor under the action of the zero voltage vector.

[0052] The three-phase permanent magnet motor phase lines are respectively equipped with current sensors, and the output signals of the current sensors are used as the input of the differential circuit. The three-phase current differential values ​​of the permanent magnet motor are obtained after the output signals of the differential sampling circuit are processed. The output U of the current sensor is sa , U sb , U sc The three-phase current value i of motor a, b, c a ,i b ,i c Satisfies the following relationship

[0053] U sa =0.5V cc +k s i a

[0054] U sb =0.5V cc +k s i b

[0055] U sc =0.5V cc +k s i c

[0056] Among them, i a ,i b ,i c is the permanent magnet motor phase current, V cc Supply voltage for current sensor, k s is a fixed coefficient.

[0057] The differential circuit is as follows Figure 2 As shown, the operational amplifier and input resistor R i , input capacitance C i , feedback resistor R f The inverting input terminal of the operational amplifier is composed of a series input resistor R i With input capacitor C i Connected to the signal output terminal of the current sensor, the in-phase input terminal of the operational amplifier is grounded, and the output terminal of the operational amplifier is connected to the feedback resistor R f Connected to the inverting input terminal; the output signal of the differential circuit is the voltage at the output terminal of the operational amplifier.

[0058] After a single sampling at the center point of the zero voltage vector, the output values ​​of the three-phase differential circuit are

[0059] U da =-R f C i *P sa

[0060] U db =-R f C i *P sb

[0061] U dc =-R f C i *P sc

[0062] Among them, U da , U db , U dc are the output values ​​of the three-phase corresponding differential circuits, and p is the differential operator. f Represents the feedback resistance R in the differential circuit f The resistance value, C i Represents the input capacitance C in the differential circuit i Capacitance value.

[0063] Furthermore, the three-phase current differential value pi of the permanent magnet motor is a , pi b , pi c Calculated as

[0064] pi a =-Uda / (k s R f C i )

[0065] pi b =-U db / (k s R f C i )

[0066] pi c =-U dc / (k s R f C i )

[0067] 2) The three-phase current differential value of the permanent magnet motor under the action of the zero voltage vector is transformed into a coordinate to obtain the current differential value in a stationary two-phase coordinate system;

[0068] The three-phase current differential value pi in the stationary three-phase coordinate system obtained by sampling the permanent magnet motor under the action of zero voltage vector a , pi b , pi c , according to the following coordinate transformation formula, the stationary three-phase coordinate system is transformed into the stationary two-phase coordinate system:

[0069] pi α =2 / 3*pi a -1 / 3*pi b -1 / 3*pi c

[0070] pi β =1.732 / 3*pi b -1.732 / 3*pi c

[0071] Among them, i α with i β They represent the α-axis current value and β-axis current value of the permanent magnet motor in the stationary two-phase coordinate system, and pi α With pi β They represent the α-axis current differential value and the β-axis current differential value of the permanent magnet motor in the stationary two-phase coordinate system, and their waveforms are Figure 4 Given in.

[0072] 3) According to the current differential value of the permanent magnet motor in the stationary two-phase coordinate system, the normalized phase-locked loop is input to obtain the rotor position and speed information of the permanent magnet motor to realize position sensorless control.

[0073] like Figure 3 The permanent magnet motor rotor position information is obtained by the differential current values ​​pi of the α-axis and β-axis in the stationary two-phase coordinate system.α With pi β The input is a normalized phase-locked loop, and the normalized phase-locked loop can be equivalent to a proportional-integral controller connected in series with an integral link.

[0074] When the voltage drop on the motor phase resistance is ignored, the α-axis current differential value and the β-axis current differential value in the stationary two-phase coordinate system sampled under the zero voltage vector satisfy:

[0075] pi α =A*sinθ e1

[0076] pi β = -A*cosθ e1

[0077] A is the amplitude of the current differential signal.

[0078] The input of the proportional-integral controller satisfies the following formula:

[0079] ε=pi α *cosθ e2 +pi β *sinθ e2

[0080] =A*sinθ e1 *cosθ e2 -A*cosθ e1 *sinθ e2

[0081] =A*sin(θ e1 -θ e2 )

[0082] ≈A*(θ e1 -θ e2 )

[0083] Among them, θ e1 is the actual rotor position of the permanent magnet motor at the last moment, θ e2 is the estimated rotor position of the permanent magnet motor at the last moment, that is, the input of the proportional-integral controller is the error of the observed position. The output of the proportional-integral controller is the estimated speed ω e ,

[0084]

[0085] Among them, k p and k i are the proportional coefficient and integral coefficient of proportional-integral control respectively, and s represents the complex variable in the Laplace domain.

[0086] The estimated rotor position is further obtained through the integral link to achieve position sensorless control.

[0087] The comparison between the rotor position waveform obtained by the differential value of the α-axis current and the differential value of the β-axis current in the stationary two-phase coordinate system under the zero voltage vector and the true value is shown in Figure 4 Given in.

[0088] According to the above calculation process, the error between the observed rotor position value and the true value is Figure 5 As shown in the figure, this method has a fast convergence speed, accurate calculation results, and the calculated rotor position value is highly consistent with the true value, which has practical value for sensorless control of permanent magnet motors.

[0089] The present invention also provides a permanent magnet motor full-speed range position sensorless control system based on a differential circuit, comprising:

[0090] A current sensor is connected to the three-phase permanent magnet motor to measure the three-phase current of the three-phase permanent magnet motor;

[0091] A three-phase differential circuit is connected to the output end of the current sensor, and a single sampling is performed under the action of a zero voltage vector to obtain an output value of the three-phase differential circuit;

[0092] A three-phase current differential value solving unit is used to solve the three-phase current differential value of the permanent magnet motor based on the output value of the three-phase differential circuit;

[0093] A coordinate transformation unit performs coordinate transformation on the three-phase current differential value to obtain the current differential value of the permanent magnet motor in a stationary two-phase coordinate system;

[0094] The rotor position and speed obtaining unit obtains the rotor position and speed of the permanent magnet motor based on the current differential value of the permanent magnet motor in a stationary two-phase coordinate system through a normalized phase-locked loop to achieve position sensorless control.

[0095] The present invention can realize the observation of the rotor position and speed of the permanent magnet motor according to the three-phase current differential signal of the permanent magnet motor obtained by sampling. The present invention does not require parameter information such as the inductance and resistance of the permanent magnet motor, and only a single sampling is performed in each switching cycle to realize accurate observation of the rotor position, which has good universality and robustness.

[0096] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A permanent magnet motor full-speed range position sensorless control method based on differential circuit, characterized in that: include: Step 1, build a three-phase differential circuit, the input ends of the three-phase differential circuit are respectively connected to the output ends of the current sensors of the three-phase current of the three-phase permanent magnet motor, and the output value of the three-phase differential circuit is obtained by single sampling under the action of the zero voltage vector, and the three-phase current differential value of the permanent magnet motor is obtained based on the output value of the three-phase differential circuit; Step 2, performing coordinate transformation on the three-phase current differential value to obtain the current differential value of the permanent magnet motor in a stationary two-phase coordinate system; Step 3, based on the current differential value of the permanent magnet motor in the stationary two-phase coordinate system, the rotor position and speed of the permanent magnet motor are obtained through a normalized phase-locked loop to achieve position sensorless control.

2. According to claim 1, a permanent magnet motor full-speed range position sensorless control method based on differential circuit is characterized in that: The output of the current sensor and the current value of the three-phase permanent magnet motor satisfy: U sa =0.5V cc +k s i a ,U sb =0.5V cc +k s i b ,U sc =0.5V cc +k s i c Among them, U sa , U sb , U sc is the output of the current sensor, i a 、i b 、i c is the current value of the three-phase a, b, c of the three-phase permanent magnet motor i a 、i b 、i c , V cc Supply voltage for current sensor, k s is the setting coefficient.

3. The method for controlling a permanent magnet motor in full speed range without position sensor based on a differential circuit according to claim 2 is characterized in that: The three-phase differential circuit includes an operational amplifier, an input resistor R i , input capacitor C i and feedback resistor R f , input resistance R i One end is connected to the signal output end of the current sensor, and the output end is connected to the input capacitor C i One end is connected to the inverting input of the operational amplifier and the input capacitor C i The other end is connected, its in-phase input is grounded, and the output is connected through the feedback resistor R f Connected to the inverting input terminal, the output value of the output terminal satisfies: U da =-R f C i *pU sa ,U db =-R f C i *pU sb ,U dc =-R f C i *pU sc Among them, U da , U db , U dc are the output values ​​of the three-phase differential circuit respectively, and p is the differential operator.

4. The method for controlling a permanent magnet motor in full speed range without position sensor based on a differential circuit according to claim 3 is characterized in that: The three-phase current differential value is: pi a U da / (k s R f C i ),pi b U db / (k s R f C i ),pi c U dc / (k s R f C i ) 5. The method for controlling a permanent magnet motor in full speed range without position sensor based on a differential circuit according to claim 4 is characterized in that: The current differential value of the permanent magnet motor in the stationary two-phase coordinate system is: pi α =2 / 3*ft a 1 / 3*ft b 1 / 3*ft c pi β =1.732 / 3*pi b -1.732 / 3*pi c Among them, pi α With pi β They respectively represent the α-axis current differential value and the β-axis current differential value of the permanent magnet motor in a stationary two-phase coordinate system.

6. The method for controlling a permanent magnet motor in full speed range without position sensor based on a differential circuit according to claim 5, characterized in that: The normalized phase-locked loop is a proportional-integral controller connected in series with an integral link, the output of the proportional-integral controller is the rotor speed, and the output of the integral link is the rotor position.

7. The method for controlling a permanent magnet motor in full speed range without position sensor based on a differential circuit according to claim 6, characterized in that: The input of the proportional-integral controller is: e=pi α *cosθ e2 +pi β *sinth e2 =A*sinθ e1 *cosθ e2 -A*cosθ e1 *sinθ e2 =A*sin(θ e1 -θ e2 ) Among them, θ e1 is the actual rotor position of the permanent magnet motor at the last moment, θ e2 is the estimated rotor position of the permanent magnet motor at the previous moment, A is the amplitude of the current differential signal, and ε is the input of the proportional-integral controller.

8. The method for controlling a permanent magnet motor in full speed range without position sensor based on a differential circuit according to claim 7, characterized in that: The output of the proportional-integral controller is: Among them, ω e is the rotation speed, k p and k i are the proportional coefficient and the integral coefficient respectively, and s represents the complex variable in the Laplace domain.

9. A permanent magnet motor full speed range position sensorless control system implementing any of the methods described in claims 1-8, characterized in that: include: A current sensor is connected to the three-phase permanent magnet motor to measure the three-phase current of the three-phase permanent magnet motor; A three-phase differential circuit is connected to the output end of the current sensor, and a single sampling is performed under the action of a zero voltage vector to obtain an output value of the three-phase differential circuit; A three-phase current differential value solving unit is used to solve the three-phase current differential value of the permanent magnet motor based on the output value of the three-phase differential circuit; A coordinate transformation unit performs coordinate transformation on the three-phase current differential value to obtain the current differential value of the permanent magnet motor in a stationary two-phase coordinate system; The rotor position and speed obtaining unit obtains the rotor position and speed of the permanent magnet motor based on the current differential value of the permanent magnet motor in a stationary two-phase coordinate system through a normalized phase-locked loop to achieve position sensorless control.

Images