Permanent magnet motor position-free control system direct current bias compensator and compensation method

Abstract

The invention provides a permanent magnet motor position-free control system DC bias compensator and a compensation method, and the compensator comprises an error calculation module which is used for comparing an original sampling current and an observation current of an alpha-beta coordinate system, and generating an error signal; the QPR regulator module is used for regulating the error signal through a quasi-proportional regulator QPR and outputting a direct-current bias observation value; the input compensation module is used for processing the direct-current bias observation value through the voltage and the counter electromotive force to obtain observation current, and the observation current is transmitted back to the error calculation module to form closed-loop negative feedback regulation; and the direct-current bias compensation quantity generation module is used for converting the direct-current bias observation value in closed-loop negative feedback regulation into the direct-current bias compensation quantity through a relation equation of a direct-current bias sampling value and a direct-current bias component and complex frequency variable conversion. And the direct current bias component in the original sampling current of the alpha-beta coordinate system is accurately compensated in a closed-loop negative feedback regulation mode.

Description

Technical Field

[0001] The present invention relates to the technical field of permanent magnet motor control, and in particular to a DC bias compensator and a compensation method for a permanent magnet motor position-free control system. Background Art

[0002] The rotary transformer used to collect the rotor position information of the permanent magnet synchronous motor is easily interfered by environmental factors such as electromagnetic radiation and temperature changes, which has a negative impact on the reliability of the permanent magnet motor transmission system. In addition, the rotary transformer requires an independent decoding circuit and software program, which increases the development cost and difficulty of the permanent magnet motor transmission system. On the contrary, the permanent magnet synchronous motor position sensorless control technology has the advantages of simplifying the physical structure of the drive system, improving the anti-interference ability of the drive system, and saving the cost of the drive system. Therefore, this technology has become one of the indispensable core technologies in the application of electric drive engineering.

[0003] The essence of permanent magnet synchronous motor position sensorless control technology is to collect the current signal at the motor port, and the voltage signal can be obtained by reconstruction, and then demodulated in combination with a specific algorithm to achieve real-time estimation of the motor rotor position. However, when the inverter used to drive the permanent magnet motor collects the current signal at the motor port, due to differences in sensor performance or temperature drift of conditioning circuit components, the collected current signal is very likely to introduce DC bias components.

[0004] When the three-phase AC current signal contains a DC bias component, on the one hand, it becomes an AC harmonic of one times the electrical fundamental frequency in the dq coordinate system after Park transformation. This AC harmonic component is used as the feedback current parameter of the dq coordinate system in the current inner loop closed-loop control, which introduces additional torque fluctuations into the drive system; on the other hand, the three-phase AC current signal needs to be transformed by Clark transformation into a current signal of the αβ two-phase coordinate system and used for rotor position estimation, but the DC component of the three-phase AC current signal will interfere with the rotor position estimation performance as a disturbance signal, causing the estimated speed to produce an oscillation of one times the electrical fundamental frequency.

[0005] Under the influence of DC bias components, the motor port voltage and current will produce obvious double fundamental frequency harmonic disturbances, and the estimated speed and dq axis feedback current will have obvious primary fundamental frequency harmonic disturbances, and the speed control performance and power quality of the drive system will be significantly reduced. The influence of DC bias components on the permanent magnet motor position-free control system will reduce the stability of the electric drive system, restricting the promotion and application of position sensor-free control technology in high-precision permanent magnet drive applications. Therefore, it is necessary to compensate for it in a targeted manner. Summary of the invention

[0006] The present invention proposes a DC bias compensator and a compensation method for a permanent magnet motor position-free control system, so as to solve the technical problem that the stability of the permanent magnet motor position-free control system is low due to the influence of the DC bias component.

[0007] In order to solve the above technical problems, the present invention provides a permanent magnet motor position-free control system DC offset compensator, including an error calculation module, a QPR regulator module, an input compensation module and a DC offset compensation amount generation module; The error calculation module is used to compare the original sampled current and the observed current in the αβ coordinate system to generate an error signal; The QPR regulator module is used to regulate the error signal through a quasi-proportional regulator QPR and output a DC bias observation value; The input compensation module is used to process the DC bias observation value through voltage and back electromotive force to obtain an observation current, and the observation current is transmitted back to the error calculation module to form a closed-loop negative feedback regulation; The DC bias compensation value generation module converts the DC bias observation value in the closed-loop negative feedback regulation into a DC bias compensation value through a relationship equation between a DC bias sampling value and a DC bias component and complex frequency variable transformation.

[0008] Preferably, the input compensation module processes the DC bias observation value through voltage and back electromotive force to obtain the expression of the observation current: ; In the formula, and denote the observed currents of the α and β axes respectively; s represents the complex frequency variable in the Laplace transform; and denote the observed voltages of the α and β axes, respectively; and denote the observed back EMF of α and β axes respectively; and Represent the DC bias observation values ​​of α and β axes respectively.

[0009] Preferably, the transfer function of the quasi-proportional regulator QPR in the QPR regulator module is: ; In the formula, , K r and Represent the proportional coefficient, integral coefficient and cut-off frequency respectively, represents the estimated electrical angular velocity of the permanent magnet motor.

[0010] Preferably, the relationship equation between the DC bias sampling value and the DC bias component in the DC bias compensation amount generating module is expressed as: ; In the formula, i α_dc and i β_dc Represent the DC bias components of α and β axes respectively; R s represents the stator resistance; L s represents the stator inductance; d / dt represents the differential operator; and Represent the DC bias values ​​of the α and β axes respectively.

[0011] The present invention also provides a method for compensating a DC offset of a permanent magnet motor position-free control system, which is implemented based on the above-mentioned DC offset compensator of the permanent magnet motor position-free control system and includes the following steps: Step S1: The original sampled current of the αβ coordinate system i α_m and i β_m The DC bias compensation amount obtained by the compensator is i α_dc_cmp and i β_dc_cmp Subtract and get the reconstructed current i α_r and i β_r ; Then, the DC bus voltage and modulation ratio are used to reconstruct the voltage signal in the αβ coordinate system u α_r and u β_r ; Step S2: Using the permanent magnet motor position-free control technology of the fundamental wave model, using u α_r , u β_r , i α_r and i β_r , get the estimated rotor position of the permanent magnet motor; Step S3: Use i α_r and i β_r Participate in Park transformation to obtain smooth dq axis scale feedback current i d and i q , to perform current closed-loop control without DC bias influence.

[0012] Preferably, in step S1, the DC bus voltage and the modulation ratio are used to reconstruct the αβ coordinate system voltage signal u α_r and u β_r The expression is: ; In the formula, U dc Indicates the DC bus voltage; d α and d β Represent the modulation ratios of the α and β axes respectively.

[0013] Preferably, step S2 comprises: Step S21: Pass u α_r , u β_r , i α_r and i β_r Obtain the scalar form of the stator flux vector; Step S22: obtaining the effective flux of the rotor, and performing equivalent estimation on the rotor position through the effective flux to obtain an estimated rotor position; Step S23: Based on the estimated rotor position, construct a position error signal through the concept of trigonometric function equivalent infinitesimal; Step S24: Use the phase-locked loop to adjust the position error signal to 0 to obtain the estimated angular velocity of the motor , the estimated angular velocity of the motor is integrated to obtain an error-free estimated rotor position.

[0014] Preferably, in step S22, the expression for obtaining the rotor effective flux is: ; ; In the formula, and Represent the α- and β-axis stator fluxes respectively; and Represents the α and β axis rotor flux respectively R s represents the stator resistance; L d and L q Respectively represent the d and q axis inductance; i d represents the d-axis current; represents the effective flux linkage vector; represents the rotor position angle; Represents the rotor permanent magnet flux vector.

[0015] Preferably, in step S23, the position error signal The expression is: ; In the formula, is the original position error, and the estimated rotor position .

[0016] Preferably, the expression of step S3 is: ; In the formula, Represents the estimated rotor position.

[0017] The beneficial effects of the present invention include at least: 1. The present invention constructs a DC bias compensator based on a quasi-proportional resonant regulator QPR, which accurately compensates the DC bias component in the original sampling current of the αβ coordinate system through closed-loop negative feedback regulation.

[0018] 2. The DC bias compensation method of the permanent magnet motor position-free control system of the present invention optimizes the speed estimation, which can significantly reduce the 1 times electrical fundamental frequency oscillation phenomenon in the estimated speed, and effectively eliminate the 2 times electrical fundamental frequency harmonics of the three-phase voltage and current at the motor port, thereby improving the system power quality.

[0019] 3. The DC offset compensation method for the permanent magnet motor position-free control system of the present invention has a simple structure. After applying the DC offset compensation technology, there is no obvious impact on the dynamic performance of the system, and the system stability is still guaranteed. It has little dependence on motor parameters and can be used in permanent magnet motor position-free control systems of different power levels. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the principle structure of a permanent magnet motor DC offset compensator according to an embodiment of the present invention; Figure 2 It is a schematic diagram of the principle structure of a DC bias compensation method for a permanent magnet motor position-free control system according to an embodiment of the present invention; Figure 3 A schematic diagram of the rotor position estimation principle structure considering DC offset compensation according to an embodiment of the present invention; Figure 4 It is a schematic diagram of the speed and position estimation waveforms before and after DC offset compensation at 800r / min of the present invention; Figure 5 It is a waveform diagram of the present invention under high dynamic acceleration and deceleration conditions after DC bias compensation is enabled. DETAILED DESCRIPTION

[0021] The following is a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the protection scope of the present invention.

[0022] To facilitate understanding of the embodiments of the present invention, several specific embodiments will be further explained below with reference to the accompanying drawings, and each embodiment does not constitute a limitation on the embodiments of the present invention.

[0023] Example 1 like Figure 1 As shown, an embodiment of the present invention provides a DC offset compensator for a permanent magnet motor position-free control system, including an error calculation module, a QPR regulator module, an input compensation module and a DC offset compensation amount generation module.

[0024] The error calculation module is used to calculate the original sampling current of the αβ coordinate system. i α_m , i β_m and observe the current , A comparison is performed to generate an error signal.

[0025] QPR regulator module, used to adjust the error signal and output the DC bias observation value .

[0026] Input compensation module, used to pass voltage and back EMF DC bias observation value Processing to obtain the observed current and , the observed current is transmitted back to the error calculation module to form a closed-loop negative feedback regulation.

[0027] The DC bias compensation generation module converts the DC bias observation value in the closed-loop negative feedback regulation into the DC bias compensation value through the relationship equation between the DC bias observation value and the DC bias component and the complex frequency variable transformation.

[0028] By using the DC offset compensator of the permanent magnet motor position-free control system of this embodiment, the DC offset component in the original sampled current of the αβ coordinate system can be accurately compensated by closed-loop negative feedback regulation.

[0029] Specifically, the observation current in the input compensation module and It is obtained through the following analysis. It includes the following steps: 1. Construct the original sampling current considering the αβ coordinate system i α_m and i β_m Contains DC bias components i α_dc and i β_dc The voltage equation at this time is shown in formula (1).

[0030] (1) In the formula, U α and U β Represent the α and β axis voltages respectively; R s represents the stator resistance; i α_m and i β_m Represent the original sampling current of α and β axis respectively; i α_dc and i β_dc Represent the DC bias components of α and β axes respectively; L s represents the stator inductance; and denote the α and β axis back EMF respectively, , , represents the electrical angular velocity, represents the rotor position angle, represents the permanent magnet flux vector; d / dt represents the differential operator.

[0031] 2. Transform equation (1) into the form of a state equation, as shown in equation (2).

[0032] (2) The last two terms in formula (2) are related to the DC bias. The differential term of the DC bias is zero, so the last two terms are used as the DC bias sampling values. D α and D β , as shown in formula (3).

[0033] (3) Combining the above formulas (1) to (3), we get the formula (4).

[0034] (4) Where S represents the complex frequency variable in Laplace transform.

[0035] Based on the above formula (4), the original sampling current is constructed and The observation model is shown in formula (5).

[0036] (5) In the formula, the signal with a superscript “~” represents the observed component.

[0037] Considering that the current in the αβ coordinate system is an AC component, a quasi-proportional regulator QPR regulator is used in this embodiment to achieve zero-static error tracking of the AC component. and Strictly track the original sampled current i α_m and i β_m , at this time the DC bias observation value and The DC bias sampling value will also be strictly tracked D α and D β , thus achieving accurate observation of DC bias.

[0038] Transfer function of quasi-proportional regulator QPR for: (6) In the formula, , K r , and Represent the proportional coefficient, integral coefficient, resonant frequency and cut-off frequency respectively. Configured as the electrical frequency of the current drive system. For position-free control systems, it needs to be configured as the estimated electrical angular velocity of the current permanent magnet motor. .

[0039] Afterwards, the DC bias compensation value generation module uses the DC bias observation value generated in the closed-loop negative feedback regulation and , through the relationship equation between the DC bias observation value and the DC bias component, that is, equation (3), and the complex frequency variable transformation, the DC bias compensation value is obtained i α_dc_cmp and i β_dc_cmp .

[0040] Example 2 This embodiment is a method for performing DC offset compensation on a permanent magnet motor position-free control system by using the DC offset compensator of the permanent magnet motor position-free control system in Embodiment 1, specifically as follows: Figure 2 This embodiment only describes the contents related to the present invention, and the prior art in the position-free control system of the permanent magnet motor is not described in detail here.

[0041] Specifically, the original sampled current of the αβ coordinate system is i α_m and i β_m Respectively i α_dc and i β_dc Subtract and eliminate the DC bias component to obtain the reconstructed current in the αβ coordinate system i α_r and i β_r , as shown in formula (7).

[0042] (7) Using DC bus voltage U dc Modulation ratio with αβ coordinate system d α and d β The voltage reconstruction of the αβ coordinate system is realized, as shown in formula (8).

[0043] (8) Then, the unbiased voltage and current signals are used to estimate the speed and position information. Specifically, Figure 3 shown.

[0044] The scalar form of the stator flux vector is obtained as shown in formula (9).

[0045] (9) Then, the effective rotor flux is calculated using formula (10).

[0046] (10) In the formula, and Represent the α- and β-axis stator fluxes respectively; and Represents the α and β axis rotor flux respectively R s represents the stator resistance; L d and L q Respectively represent the d and q axis inductance; id represents the d-axis current; represents the effective flux linkage vector; represents the rotor position angle; Represents the rotor permanent magnet flux vector.

[0047] The stator flux on the left side of the equation can be obtained by integrating the back EMF at the motor port, while the effective flux vector on the right side is , which is expressed as , where is the effective flux vector The modulus, as a scalar, reflects the effective magnetic flux size.

[0048] The effective flux vector is , although its amplitude is similar to the rotor permanent magnet flux vector The amplitudes are different, but their directions are consistent, so the effective flux can be used to make an equivalent estimate of the rotor position.

[0049] Constructing position error signal based on the concept of trigonometric function equivalent infinitesimal , and its mathematical principle is shown in formula (11).

[0050] (11) In the above formula, is the original position error, and the estimated rotor position .

[0051] The estimated angular velocity of the motor can be obtained by adjusting the position error signal to 0 using a phase-locked loop. , and integrating it can get the estimated rotor position information of the motor.

[0052] Finally, the unbiased current signal is used to participate in the current closed-loop control: the reconstructed current using the αβ coordinate system i αβ_r Participate in Park transformation to obtain smooth dq axis scale feedback current i d and i q , expressed as shown in formula (12).

[0053] (12) The method of this embodiment estimates the rotor position of the permanent magnet motor after reconstructing the current and voltage according to the DC bias compensation amount obtained by the DC bias compensator of the permanent magnet motor position-free control system, thereby obtaining a smooth rotor speed estimation effect, and using the reconstructed current of the αβ coordinate system to participate in the Park transformation to obtain a smooth dq axis scale system feedback current, so that the current closed-loop control can obtain an effect without the influence of DC bias. The DC bias and the second fundamental harmonic in the three-phase voltage and the three-phase current are significantly weakened, and the first fundamental harmonic oscillation in the estimated speed is effectively suppressed, thereby improving the stability of the permanent magnet motor position-free control system.

[0054] Example 3 This embodiment combines Figure 4 and Figure 5 The experimental waveforms illustrate the performance of the DC offset compensator of the permanent magnet motor position-free control system of Example 1 and the DC offset compensation method of the permanent magnet motor position-free control system of Example 2.

[0055] Figure 4 The figure is a schematic diagram of the speed and position estimation waveforms before and after DC offset compensation at 800 r / min in the present invention. Figure 4 (a) in the figure is, from top to bottom, the given value and estimated value of DC bias, the given value and estimated value of speed observation, speed error and position error. Figure 4 (b) and Figure 4 (c) in the figure shows the estimated speed error and spectrum analysis before and after DC offset compensation. In the figure, the DC offset compensation function is enabled 1.5s after the DC offset appears. It can be seen that before DC offset compensation, the estimated speed has obvious fluctuations, and the harmonic frequencies are 1 times the electrical fundamental frequency (200Hz) and 2 times the electrical fundamental frequency (400Hz). After DC offset compensation, the fluctuation of the estimated speed disappears significantly.

[0056] Figure 5 This is the waveform of the present invention under high dynamic acceleration and deceleration conditions after DC bias compensation is enabled. It can be seen that after enabling the DC bias compensation function, the system exhibits good DC bias suppression effect in different speed ranges, and the speed and current tracking effects are good, and the speed regulation function has no obvious negative impact.

[0057] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. Only the preferred embodiments of the present invention are expressed. The description is more specific and detailed, but it cannot be understood as limiting the scope of the present invention. As long as there is no contradiction in the combination of these technical features, they should be considered as within the scope of this specification.

[0058] It should be noted that, for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention, and these modifications and improvements all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the attached claims.

Claims

1. A DC offset compensator for a permanent magnet motor position-free control system, characterized in that: It includes an error calculation module, a QPR regulator module, an input compensation module and a DC offset compensation amount generation module; The error calculation module is used to compare the original sampled current and the observed current in the αβ coordinate system to generate an error signal; The QPR regulator module is used to regulate the error signal through a quasi-proportional regulator QPR and output a DC bias observation value; The input compensation module is used to process the DC bias observation value through voltage and back electromotive force to obtain an observation current, and the observation current is transmitted back to the error calculation module to form a closed-loop negative feedback regulation; The DC bias compensation generating module converts the DC bias observation value in the closed-loop negative feedback regulation into the DC bias compensation value through the relationship equation between the DC bias sampling value and the DC bias component and the complex frequency variable transformation.

2. The DC offset compensator of a permanent magnet motor position-free control system according to claim 1, characterized in that: The input compensation module processes the DC bias observation value through voltage and back electromotive force to obtain the expression of the observation current: ； In the formula, and denote the observed currents of α and β axes respectively; s represents the complex frequency variable in Laplace transform; and denote the observed voltages of the α and β axes, respectively; and denote the observed back EMF of α and β axes respectively; and Represent the DC bias observation values ​​of α and β axes respectively.

3. The DC offset compensator of a permanent magnet motor position-free control system according to claim 1, characterized in that: The transfer function of the quasi-proportional regulator QPR in the QPR regulator module is: ； In the formula, , K r and Represent the proportional coefficient, integral coefficient and cut-off frequency respectively, represents the estimated electrical angular velocity of the permanent magnet motor.

4. The DC offset compensator of a permanent magnet motor position-free control system according to claim 1, characterized in that: The relationship equation between the DC bias sampling value and the DC bias component in the DC bias compensation amount generation module is expressed as: ； In the formula, i α_dc and i β_dc Represent the DC bias components of α and β axes respectively; R s represents the stator resistance; L s represents the stator inductance; d / dt represents the differential operator; and Represent the DC bias values ​​of the α and β axes respectively.

5. A method for compensating a DC offset of a permanent magnet motor position-free control system, implemented based on a DC offset compensator of a permanent magnet motor position-free control system according to claim 1, characterized in that: The following steps are involved: Step S1: The original sampled current of the αβ coordinate system i α_m and i β_m The DC bias compensation amount obtained by the compensator is i α_dc_cmp and i β_dc_cmp Subtract and get the reconstructed current i α_r and i β_r ; Then, the DC bus voltage and modulation ratio are used to reconstruct the voltage signal in the αβ coordinate system u α_r and u β_r ; Step S2: Using the permanent magnet motor position-free control technology of the fundamental wave model, using u α_r , u β_r , i α_r and i β_r , get the estimated rotor position of the permanent magnet motor; Step S3: Use i α_r and i β_r Participate in Park transformation to obtain smooth dq axis scale feedback current i d and i q , to perform current closed-loop control without DC bias influence.

6. A method for compensating a DC bias of a permanent magnet motor position-free control system according to claim 5, characterized in that: In step S1, the DC bus voltage and modulation ratio are used to reconstruct the αβ coordinate system voltage signal u α_r and u β_r The expression is: ； In the formula, U dc Indicates the DC bus voltage; d α and d β Represent the modulation ratios of the α and β axes respectively.

7. The method for compensating a DC offset of a permanent magnet motor position-free control system according to claim 5, characterized in that: Step S2 include: Step S21: Pass u α_r , u β_r , i α_r and i β_r Obtain the scalar form of the stator flux vector; Step S22: obtaining the effective flux of the rotor, and performing equivalent estimation on the rotor position through the effective flux to obtain an estimated rotor position; Step S23: Based on the estimated rotor position, construct a position error signal through the concept of trigonometric function equivalent infinitesimal; Step S24: Use the phase-locked loop to adjust the position error signal to 0 to obtain the estimated angular velocity of the motor , the estimated angular velocity of the motor is integrated to obtain an error-free estimated rotor position.

8. A method for compensating a DC offset of a permanent magnet motor position-free control system according to claim 7, characterized in that: In step S22, the expression for obtaining the rotor effective flux is: ； ； In the formula, and Represent the α- and β-axis stator fluxes respectively; and Represents the α and β axis rotor flux respectively R s represents the stator resistance; L d and L q Respectively represent the d and q axis inductance; i d represents the d-axis current; represents the effective flux linkage vector; represents the rotor position angle; Represents the rotor permanent magnet flux vector.

9. A method for compensating a DC offset of a permanent magnet motor position-free control system according to claim 8, characterized in that: In step S23, the position error signal The expression is: ； In the formula, is the original position error, and the estimated rotor position .

10. The method for compensating a DC offset of a permanent magnet motor position-free control system according to claim 5, characterized in that: The expression of step S3 is: ； In the formula, Represents the estimated rotor position.

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