A sensorless minimum loss control method for built-in permanent magnet synchronous motor

Abstract

A sensorless minimum loss control method for a built-in permanent magnet synchronous motor belongs to the field of motor control technology, and includes the following steps: Step S01: constructing a d-q axis voltage expression, a torque equation, and an α-β axis flux equation for a built-in permanent magnet synchronous motor considering iron loss; Step S02: constructing a d-q axis equivalent current and building a mathematical model of total controllable electrical loss power; Step S03: constructing a virtual power current compensation controller; Step S04: designing an improved nonlinear observer. When the present invention uses a virtual signal injection method to search online for the optimal d-axis stator current, the search process does not need to derive the loss model, which optimizes the solution process and improves the convergence speed. The active flux estimator is designed by equivalent active flux and compensation function, which reduces the influence of the initial rotor flux and DC bias on the control system and realizes sensorless control.

Description

Technical Field

[0001] The present invention belongs to the technical field of motor control, and in particular relates to a sensorless minimum loss control method for a built-in permanent magnet synchronous motor. Background Art

[0002] Permanent magnet synchronous motor is a synchronous motor that uses permanent magnets to establish an excitation magnetic field. Its stator generates a rotating magnetic field, and the rotor is made of permanent magnet material. It can be divided into surface-mounted and built-in types according to the rotor structure. Because of its advantages of high power density, high efficiency and wide speed regulation range, it is widely used in industrial occasions such as new energy motors and heavy machinery. Among them, energy efficiency and power density, as important properties of motors, play a decisive role in the performance of permanent magnet synchronous motors. The minimum loss control system for built-in permanent magnet synchronous motors needs to be based on obtaining accurate rotor position, but considering the cost of the drive system, the stability of operation and the difficulty of maintaining physical sensors in harsh environments, the research on position sensorless technology is gradually becoming one of the research hotspots of motor control systems.

[0003] The core of the minimum loss control of permanent magnet synchronous motors is to build a loss model, conduct an online search for the electrical losses that appear in the motor control system, and then obtain the optimal regulation current. Traditional minimum energy consumption control generally uses the derivation method to obtain the minimum power loss operating point, but there are problems with traditional minimum loss control: the traditional minimum loss control structure of the built-in permanent magnet synchronous motor considering iron loss is complex, and the derivation method cannot be used to obtain the optimal regulation current. The nonlinear observer does not require speed information, thereby eliminating the complexity associated with speed estimation errors. At the same time, compared with the back electromotive force, the rotor flux does not disappear when stationary, but remains unchanged, but the following problems still exist: the traditional nonlinear observer is not easy to obtain the initial rotor flux, and there is a DC bias problem. Summary of the invention

[0004] In view of the above shortcomings and deficiencies of the prior art, the present invention provides a sensorless minimum loss control method for a built-in permanent magnet synchronous motor. When the virtual signal injection method is used to search online for the optimal d-axis stator current, the search process does not need to derive the loss model, which optimizes the solution process and improves the convergence speed. At the same time, by constructing an equivalent active flux and compensation function, the influence of the initial rotor flux and DC bias on the control system is weakened, and the accuracy of the rotor electrical angle estimation is improved.

[0005] In order to achieve the above object, the main technical solutions adopted by the present invention include:

[0006] A sensorless minimum loss control method for an internal permanent magnet synchronous motor comprises the following steps:

[0007] Step S01: Construct the dq axis voltage expression, torque equation and α-β axis flux equation of the interior permanent magnet synchronous motor considering iron loss:

[0008]

[0009] Where: i dt 、i qt are the d-axis weak magnetic current and the q-axis torque current respectively; u d 、u q and L d , L q are the stator voltage and inductance of the d-axis and q-axis respectively; ψ f is the permanent magnet flux; R s is the stator resistance; ω e represents the rotor electrical angular velocity; p is the differential operator; R total =(R s / R fe )+1; R fe is the iron loss resistance.

[0010]

[0011] Where: T e is the electromagnetic torque; n p is the pole pair number.

[0012]

[0013] Where: λ=[λ α ,λ β ] is the magnetic flux in the α-β axis; v αβ =[u α ,u β ] is the α-β axis voltage; i αβ =[i α ,i β ] is the α-β axis current; ΔL=L d -L q ; c(θ)=[cosθ,sinθ] T ; θ is the rotor electrical angle.

[0014] Step S02: Construct dq axis equivalent current:

[0015]

[0016] Where: i N is the equivalent current; Λ is the combined parameter; sgn(·) is the sign function.

[0017] Step S03: Combine the motor control system mathematical model obtained in step S01 with the power basic calculation equation P=i 2R, build a mathematical model of total controllable electrical loss power:

[0018]

[0019] Where: P E , P Cu and P Fe They are the total controllable loss power, controllable copper loss power and controllable iron loss power of the motor control system respectively;

[0020] Step S04: According to Kirchhoff's theorem and the dq axis voltage equation in step S01, the dq axis iron loss current equation is obtained as follows:

[0021]

[0022] Where: i df 、i qf are the d-axis and q-axis iron loss currents respectively;

[0023] Step S05: Substitute the dq-axis equivalent current of step S02 and the iron loss current equation of step S04 into the total controllable electrical loss power mathematical model in step S03 to construct a total controllable electrical loss power mathematical model with only a single variable when the motor is in stable operation, that is:

[0024]

[0025] Where: A = ω e / R Fe .

[0026] Step S06: using a virtual signal to search online for a minimum power loss operating point;

[0027] Step S07: inputting the d-axis weak magnetic current compensation amount at the minimum power loss working point obtained by searching into the actual control system to realize minimum loss control based on virtual power current compensation.

[0028] Step S08: constructing active magnetic flux, equivalent active magnetic flux and compensation function through the mathematical model of the built-in permanent magnet synchronous motor in step S01:

[0029]

[0030] in: Estimate the active flux for α-β;

[0031]

[0032] in: Estimate the active flux for α-β equivalent;

[0033]

[0034] Where: Γ is the gain coefficient; is the compensation function;

[0035] Step S09: Through step S08, an improved nonlinear observer can be obtained:

[0036]

[0037] Where: γ = 300.

[0038] Step S10: Obtain an estimated rotor electrical angle using the estimated active magnetic flux obtained in step S09:

[0039]

[0040] in: To estimate the rotor electrical angle.

[0041] 2. A sensorless minimum loss control method for a built-in permanent magnet synchronous motor according to claim 1, characterized in that: the specific method of using virtual signals to search online for the minimum loss power operating point in step S06 is as follows:

[0042] Step S601: superimpose a tiny virtual DC signal ε onto i N In, we get:

[0043]

[0044] in: is the virtual current after superimposing ε.

[0045] Step S602: Substitute P E (i N ) is obtained from The power generated is the virtual total controllable power loss

[0046] Step S603: The adjustment process of improving the virtual power current compensation control is as follows:

[0047] 1) When hour, renew Repeat step 1), otherwise jump to step 3);

[0048] 2) When hour, renew Repeat step 2), otherwise jump to step 3);

[0049] 3) Output optimal regulation current

[0050] The beneficial effects of the present invention are:

[0051] When the present invention uses the virtual signal injection method to search for the optimal d-axis stator current online, the search process does not need to derive the loss model, which optimizes the solution process, improves the convergence speed, and reduces the difficulty of control system design. At the same time, by constructing equivalent active magnetic flux and compensation function, the influence of initial rotor flux and DC bias on the control system is weakened, and the accuracy of rotor electrical angle estimation is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 This is the structural block diagram of the IPMSM sensorless minimum loss control system;

[0053] Figure 2 This is a power curve diagram of the improved virtual power current compensation control in Example 1;

[0054] Figure 3 It is a curve diagram of feedback current and regulation current of the improved virtual power current compensation control in Example 1;

[0055] Figure 4 is the estimated active magnetic flux curve diagram in Example 1;

[0056] Figure 5 is a graph of estimated rotor electrical angle in Example 1;

[0057] Figure 6 For comparison in the comparative example d =0 loss optimization performance diagram;

[0058] Figure 7 This is a performance diagram for loss optimization compared with the traditional virtual power current compensation control in the comparative example. DETAILED DESCRIPTION

[0059] In order to better explain the present invention and facilitate understanding, the present invention is described in detail below through specific implementation modes in conjunction with the accompanying drawings.

[0060] The present invention provides a sensorless minimum loss control method for a built-in permanent magnet synchronous motor, comprising the following steps:

[0061] Step S01: Construct the dq axis voltage expression, torque equation and α-β axis flux equation of the interior permanent magnet synchronous motor considering iron loss:

[0062]

[0063] Where: i dt 、i qtare the d-axis weak magnetic current and the q-axis torque current respectively; u d 、u q and L d , L q are the stator voltage and inductance of the d-axis and q-axis respectively; ψ f is the permanent magnet flux; R s is the stator resistance; ω e represents the rotor electrical angular velocity; p is the differential operator; R total =(R s / R fe )+1; R fe is the iron loss resistance.

[0064]

[0065] Where: T e is the electromagnetic torque; n p is the pole pair number.

[0066]

[0067] Where: λ=[λ α ,λ β ] is the magnetic flux in the α-β axis; v αβ =[u α ,u β ] is the α-β axis voltage; i αβ =[i α ,i β ] is the α-β axis current; ΔL=L d -L q ; c(θ)=[cosθ,sinθ] T ; θ is the rotor electrical angle.

[0068] Step S02: Construct dq axis equivalent current:

[0069]

[0070] Where: i N is the equivalent current; Λ is the combined parameter; sgn(·) is the sign function.

[0071] Step S03: Combine the motor control system mathematical model obtained in step S01 with the power basic calculation equation P=i 2 R, build a mathematical model of total controllable electrical loss power:

[0072]

[0073] Where: P E , P Cu and P FeThey are the total controllable loss power, controllable copper loss power and controllable iron loss power of the motor control system respectively; i df 、i qf are the d-axis and q-axis iron loss currents respectively;

[0074] Step S04: According to Kirchhoff's theorem and the dq axis voltage equation in step S01, the dq axis iron loss current equation is obtained as follows:

[0075]

[0076] Where: i df 、i qf are the d-axis and q-axis iron loss currents respectively;

[0077] Step S05: Substitute the dq-axis equivalent current of step S02 and the iron loss current equation of step S04 into the total controllable electrical loss power mathematical model in step S03 to construct a total controllable electrical loss power mathematical model with only a single variable when the motor is in stable operation, that is:

[0078]

[0079] Where: A = ω e / R Fe .

[0080] Step S06: using a virtual signal to search online for a minimum power loss operating point;

[0081] The specific steps of step S06 are as follows:

[0082] Step S601: superimpose a tiny virtual DC signal ε onto i N In, we get:

[0083]

[0084] in: is the virtual current after superimposing ε.

[0085] Step S602: Substitute P E (i N ) is obtained from The power generated is the virtual total controllable power loss

[0086] Step S603: The adjustment process of improving the virtual power current compensation control is as follows:

[0087] 1) When hour, renew Repeat step 1), otherwise jump to step 3);

[0088] 2) When hour, renew Repeat step 2), otherwise jump to step 3);

[0089] 2) Output optimal regulation current

[0090] Step S07: inputting the d-axis weak magnetic current compensation amount at the minimum power loss working point obtained by searching into the actual control system to realize minimum loss control based on virtual power current compensation.

[0091] Step S08: constructing active magnetic flux, equivalent active magnetic flux and compensation function through the mathematical model of the built-in permanent magnet synchronous motor in step S01:

[0092]

[0093] in: Estimate the active flux for α-β;

[0094]

[0095] in: Estimate the active flux for α-β equivalent;

[0096]

[0097] Where: Γ is the gain coefficient; is the compensation function.

[0098] Step S09: Through step S08, an improved nonlinear observer can be obtained:

[0099]

[0100] Where: γ = 300.

[0101] Step S10: Obtain an estimated rotor electrical angle using the estimated active magnetic flux obtained in step S09:

[0102]

[0103] in: To estimate the rotor electrical angle.

[0104] The structural block diagram of the IPMSM sensorless minimum loss control system is as follows Figure 1 shown.

[0105] Example 1

[0106] The motor runs at a given speed of 1200r / min and a torque of 3N﹒m. According to the above method and steps, the energy consumption optimization performance of the designed control strategy is as follows Figure 2 As shown, the d-axis feedback current and regulation current are as follows Figure 3 As shown, the improved nonlinear observer estimates the active flux as Figure 4 As shown, the estimated rotor electrical angle is Figure 5 shown.

[0107] observe Figure 2 , 3 It can be concluded that the control system has achieved convergence within 0.075s, and the system runs stably without any major oscillations. Figure 2 It can be obtained that when the motor runs stably, the total controllable power loss is stable at 201W (±0.5).

[0108] observe Figure 4 , 5 It can be concluded that the control system can effectively estimate the rotor electrical angle and reduce the impact of the initial rotor flux and DC bias on the control system.

[0109] Comparative Example

[0110] Under multiple working conditions, comparison d = 0 control, traditional virtual signal injection control and the designed minimum loss control strategy. The simulation results are as follows Figure 6 , 7 Observation Figure 6 , 7 , under multiple groups of the same working conditions, as the speed increases, the iron loss increases. Therefore, the improved virtual power current compensation control is better than i d = 0 control optimization efficiency increases accordingly, and in the set working conditions, the loss range is reduced by 4% to 24.21%. Compared with the traditional virtual power current compensation control, since the optimization deviation of the traditional virtual power current compensation control and the improved virtual power current compensation control for iron loss is smaller, the improved virtual power current compensation control has stronger energy consumption optimization performance at low speed than the traditional virtual power current compensation control. In the set working conditions, the loss range is reduced by 1.33% to 9.15%.

[0111] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. Alterations, modifications, substitutions and variations of the above embodiments by a person skilled in the art are all within the scope of the present invention.

Claims

1. A sensorless minimum loss control method for an internal permanent magnet synchronous motor, characterized in that: The steps include: Step S01: Construct the dq axis voltage expression, torque equation and α-β axis flux equation of the interior permanent magnet synchronous motor considering iron loss: Where: i dt 、i qt are the d-axis weak magnetic current and the q-axis torque current respectively; u d 、u q and L d , L q are the stator voltage and inductance of the d-axis and q-axis respectively; ψ f is the permanent magnet flux; R s is the stator resistance; ω e represents the rotor electrical angular velocity; p is the differential operator; R total =(R s / R fe )+1; R fe is the iron loss resistance; Where: T e is the electromagnetic torque; n p is the pole pair number; Where: λ=[λ α ,λ β ] is the magnetic flux in the α-β axis; v αβ =[u α ,u β ] is the α-β axis voltage; i αβ =[i α ,i β ] is the α-β axis current; ΔL=L d -L q ; c(θ)=[cosθ,sinθ] T ;θ is the rotor electrical angle; Step S02: Construct dq axis equivalent current: Where: i N is the equivalent current; Λ is the combination parameter; sgn(·) is the sign function; Step S03: Combine the motor control system mathematical model obtained in step S01 with the power basic calculation equation P=i 2 R, build a mathematical model of total controllable electrical loss power: Where: P E , P Cu and P Fe They are the total controllable loss power, controllable copper loss power and controllable iron loss power of the motor control system respectively; i df 、i qf are the d-axis and q-axis iron loss currents respectively; Step S04: According to Kirchhoff's theorem and the dq axis voltage equation in step S01, the dq axis iron loss current equation is obtained as follows: Where: i df 、i qf are the d-axis and q-axis iron loss currents respectively; Step S05: Substitute the dq-axis equivalent current of step S02 and the iron loss current equation of step S04 into the total controllable electrical loss power mathematical model in step S03 to construct a total controllable electrical loss power mathematical model with only a single variable when the motor is in stable operation, that is: Where: A=ω e / R Fe ; Step S06: using a virtual signal to search online for a minimum power loss operating point; Step S07: inputting the d-axis weak magnetic current compensation amount at the minimum power loss working point obtained by searching into the actual control system to realize minimum loss control based on virtual power current compensation; Step S08: constructing active magnetic flux, equivalent active magnetic flux and compensation function through the mathematical model of the built-in permanent magnet synchronous motor in step S01: in: Estimate the active flux for α-β; in: Estimate the active flux for α-β equivalent; Where: Γ is the gain coefficient; is the compensation function; Step S09: Through step S08, an improved nonlinear observer can be obtained: Where: γ = 300; Step S10: Obtain an estimated rotor electrical angle using the estimated active magnetic flux obtained in step S09: in: To estimate the rotor electrical angle.

2. A sensorless minimum loss control method for an interior permanent magnet synchronous motor according to claim 1, characterized in that: The specific method of using virtual signals to search online for the minimum power loss operating point in step S06 is as follows: Step S601: superimpose a tiny virtual DC signal ε onto i N In, we get: in: is the virtual current after superimposing ε; Step S602: Substitute P E (i N ) is obtained from The power generated is the virtual total controllable power loss Step S603: The adjustment process of improving the virtual power current compensation control is as follows: 1) When hour, renew Repeat step 1), otherwise jump to step 3); 2) When hour, renew Repeat step 2), otherwise jump to step 3); 3) Output optimal regulation current

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