A stator resistance online identification method independent of rotor position information

Abstract

The application discloses a stator resistance online identification method independent of rotor position information, belongs to the technical field of stator resistance identification, and is applied to a stator resistance identification system, wherein the stator resistance identification system comprises a control system, an identification system and a permanent magnet synchronous motor, the permanent magnet synchronous motor is connected with the identification system, the permanent magnet synchronous motor is connected with the identification system through the control system, and the identification system comprises a structure module. The method comprises the following steps: obtaining a reference position angle of the permanent magnet synchronous motor, and establishing a reference rotating coordinate system in combination with a two-phase static coordinate system; initializing the identification system; obtaining an electric angle frequency, an output torque, a voltage instruction and a phase current of the permanent magnet synchronous motor in the reference rotating coordinate system, converting the phase current into a stator current in the reference rotating coordinate system, and inputting the stator current into the structure module of the identification system; calculating input and output of the identification system, constructing an identification iteration equation not containing rotor position information, repeatedly and iteratively identifying the stator resistance, and outputting a stator resistance identification result.

Description

Technical Field

[0001] This invention belongs to the field of stator resistance identification technology, specifically relating to an online stator resistance identification method that does not rely on rotor position information. Background Technology

[0002] In recent years, permanent magnet synchronous motors (PMSMs) have been widely used in transportation, industrial control, and other fields due to their simple structure and high efficiency. A PMSM comprises four basic electrical parameters: stator resistance, d-axis inductance, q-axis inductance, and permanent magnet flux linkage. These parameters are closely related to the control performance of the entire control system; therefore, identification of each electrical parameter is necessary in most applications. Among these four basic parameters, stator resistance, in addition to its application within the control system, directly reflects the temperature change of the motor windings, which is used for temperature detection and corresponding fault protection strategies. Therefore, stator resistance identification algorithms for PMSMs, especially online identification algorithms, are of great significance for the accurate and reliable control of PMSMs.

[0003] Most common online stator resistance identification algorithms for permanent magnet synchronous motors (PMSMs) are based on voltage equations derived in a two-phase rotating coordinate system. Accurate identification relies on the control system having accurate rotor position information. However, in many PMSM applications, limitations such as cost and installation space often necessitate sensorless control systems. In these cases, rotor position information is estimated using an observer. Even if this method maintains reliable control system operation, the estimated position often deviates from the actual position. Even in control systems with position sensors, rotor position information is affected by sampling and computation delays, causing deviations from the true position angle. Under these conditions, traditional online stator resistance identification algorithms are unusable. Some universities and companies have proposed solutions, mostly employing artificial intelligence algorithms or model reference adaptive observers for parameter identification without rotor position information. However, these solutions consume significant microcontroller resources and require complex parameter tuning, making large-scale application in different scenarios difficult.

[0004] In summary, accurate identification of the stator resistance of permanent magnet synchronous motors requires accurate acquisition of rotor position information. Existing technologies obtain rotor position information through conventional observers, which has certain errors. Furthermore, parameter identification under conditions without rotor position information using artificial intelligence algorithms or model reference adaptive observers will consume a large amount of microcontroller computing resources and require a relatively complex parameter debugging process. Summary of the Invention

[0005] The purpose of this invention is to provide an online stator resistance identification method that does not rely on rotor position information. This method can solve the technical problem that accurate identification of stator resistance in permanent magnet synchronous motors requires accurate acquisition of rotor position information, and that the rotor position information obtained through conventional observers has certain errors. In addition, this invention can also solve the technical problem that existing technologies use artificial intelligence algorithms or model reference adaptive observers for parameter identification under conditions without rotor position information, which consumes a lot of microcontroller computing resources and requires a relatively complex parameter debugging process.

[0006] To solve the above-mentioned technical problems, the present invention is implemented as follows:

[0007] This invention provides an online stator resistance identification method that does not rely on rotor position information, applied to a stator resistance identification system. The stator resistance identification system includes a control system, an identification system, and a permanent magnet synchronous motor (PMSM). The PMSM is directly connected to the identification system and also connected to the identification system through the control system. The identification system includes structural modules. The online identification method includes:

[0008] S101: Obtain the reference position angle of the permanent magnet synchronous motor, and establish a reference rotating coordinate system of the permanent magnet synchronous motor based on the reference position angle and the two-phase stationary coordinate system. The rotational angular velocity of the reference rotating coordinate system is the same as the rotational angular velocity of the actual rotating coordinate system of the permanent magnet synchronous motor.

[0009] S102: Initialize the identification system;

[0010] S103: Real-time acquisition of the electrical angular frequency, output torque, voltage command and phase current of the permanent magnet synchronous motor in the reference rotating coordinate system, and conversion of the phase current to the stator current in the reference rotating coordinate system;

[0011] S104: Input the electrical angular frequency, output torque, voltage command in the reference rotating coordinate system, and stator current in the reference rotating coordinate system to the construction module of the identification system;

[0012] S105: The construction module calculates the input and output of the identification system based on the recursive damped least squares method with forgetting factor;

[0013] S106: Construct an identification iterative equation that does not contain rotor position information based on the input and output of the identification system, and identify the stator resistance of the permanent magnet synchronous motor through the identification iterative equation.

[0014] S107: Identification result of the stator resistance of the output permanent magnet synchronous motor;

[0015] S108: Repeat S103-S107 to iteratively identify the stator resistance.

[0016] In this embodiment of the invention, without needing to obtain the rotor position information of the permanent magnet synchronous motor (PMSM), a reference position angle of the PMSM is obtained, and a reference rotating coordinate system of the PMSM is established. By obtaining the electrical angular frequency, output torque, voltage command, and phase current of the PMSM in the reference rotating coordinate system, the input and output of the identification system are calculated based on the recursive damped least squares method with a forgetting factor. Then, an identification iterative equation without rotor position information is constructed to identify the stator resistance. The parameter acquisition method used in the construction of the identification iterative equation is simple and the data is accurate. The rotor position information of the PMSM is not required in the entire construction process of the identification iterative equation, and the rotor position information is not required. This avoids the identification error of stator resistance caused by inaccurate rotor position information, and also avoids the problem of wasting a lot of computing resources and complex parameter debugging by artificial intelligence. This improves the accuracy of the stator resistance identification result, reduces the difficulty of stator resistance identification, and the stator resistance identification process is simple, fast, and highly stable. Attached Figure Description

[0017] Figure 1 This is a schematic flowchart of an online stator resistance identification method that does not rely on rotor position information, provided by an embodiment of the present invention.

[0018] Figure 2 This is a schematic diagram of the reference rotating coordinate system provided in an embodiment of the present invention.

[0019] Figure 3 This is a schematic diagram of the stator resistance identification system provided in an embodiment of the present invention.

[0020] The realization of the objective, functional characteristics and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0022] The following description, in conjunction with the accompanying drawings, details a method for online stator resistance identification that does not rely on rotor position information, through specific embodiments and application scenarios.

[0023] Reference Figure 1The diagram shows a schematic flowchart of an online stator resistance identification method that does not rely on rotor position information, provided by an embodiment of the present invention.

[0024] Reference Figure 2 The diagram shows a reference rotating coordinate system provided in an embodiment of the present invention.

[0025] Figure 2 In this invention, the dq-axis coordinate system represents the true rotating coordinate system, the γ-δ coordinate system represents the reference rotating coordinate system, and the α-β coordinate system represents the two-phase stationary coordinate system. The two-phase stationary coordinate system is fixed and known. The reference rotating coordinate system can be obtained by transforming the two-phase stationary coordinate system using a reference position angle. However, if the reference position angle has an error, the true coordinate system cannot be obtained. Therefore, the method for establishing the reference rotating coordinate system used in this invention is independent of the true rotating coordinate system. Figure 2 It's just describing the relationship between the two, w e and w ref Representing the rotational angular velocities of the real coordinate system and the reference coordinate system, respectively, in this invention, they are approximately equal, θ ref θ represents the reference position angle. e It represents the true position angle of the real rotating coordinate system.

[0026] Reference Figure 3 This diagram illustrates the structure of a stator resistance identification system provided in an embodiment of the present invention. The present invention provides an online stator resistance identification method independent of rotor position information, applied to a stator resistance identification system. The stator resistance identification system includes a control system, an identification system, and a permanent magnet synchronous motor. The permanent magnet synchronous motor is directly connected to the identification system and is also connected to the identification system through the control system. The identification system includes structural modules, and the online identification method includes:

[0027] S101: Obtain the reference position angle of the permanent magnet synchronous motor, and establish a reference rotating coordinate system of the permanent magnet synchronous motor based on the reference position angle and the two-phase stationary coordinate system. The rotational angular velocity of the reference rotating coordinate system is the same as the rotational angular velocity of the actual rotating coordinate system of the permanent magnet synchronous motor.

[0028] The reference rotating coordinate system is a two-phase rotating coordinate system. In this invention, to facilitate the distinction between it and the real rotating coordinate system, the two-phase rotating coordinate system is described as the reference rotating coordinate system.

[0029] It should be noted that the reference position angle is also called the rotor position angle. The reference rotating coordinate system established based on the reference position angle and the two-phase stationary coordinate system does not need to coincide with the actual rotating coordinate system of the permanent magnet synchronous motor. It is only necessary to ensure that the rotational angular velocity of the reference rotating coordinate system and the actual rotating coordinate system are the same. In other words, it is not necessary to obtain the angular position of the actual rotating coordinate system.

[0030] In practical applications, the true coordinate system cannot be obtained when the reference position angle has an error. Therefore, the method for establishing the reference rotating coordinate system used in this invention is independent of the true rotating coordinate system. The two rotating coordinate systems are fixed and known. The reference rotating coordinate system can be obtained by performing coordinate transformation on the two stationary coordinate systems using the reference position angle.

[0031] In one possible implementation, S101 specifically includes:

[0032] S1011: Obtain the reference position angle of the permanent magnet synchronous motor.

[0033] It should be noted that the reference position angle can be obtained using any method that satisfies the condition that the rotational angular velocity of the reference rotating coordinate system is the same as the rotational angular velocity of the actual rotating coordinate system of the permanent magnet synchronous motor. This includes, but is not limited to, obtaining the reference position angle using a rotor position estimation algorithm or a target speed integral method, such as the Vf control method or the If control method, which both belong to the target speed integral method.

[0034] S1012: Use the reference position angle to perform a Park transformation on the two stationary coordinate systems to obtain a reference rotating coordinate system.

[0035] Optionally, the rotational angular velocity of the reference rotating coordinate system and the rotational angular velocity of the actual rotating coordinate system of the permanent magnet synchronous motor can be made the same through a rotor position estimation algorithm.

[0036] It is understandable that a reference rotating coordinate system is established based on a two-phase stationary coordinate system and a reference position angle. The angular velocity of the reference rotating coordinate system is the same as that of the actual rotating coordinate system. Without obtaining the angular position of the actual rotating coordinate system, a reference rotating coordinate system is established using the obtained reference position angle and the two-phase stationary coordinate system of the permanent magnet synchronous motor. The angular velocity of the reference rotating coordinate system is the same as that of the actual rotating coordinate system of the permanent magnet synchronous motor. Calculations are performed based on the reference rotating coordinate system to identify the stator resistance, avoiding the errors caused by obtaining rotor position information through an observer in existing technologies.

[0037] S102: Initialize the identification system.

[0038] Understandably, the initialization of the identification system ensures that there is no extra data in each parameter value before it is used in the calculation, thus avoiding the introduction of irrelevant data during the calculation process, which could lead to an unacceptable final result.

[0039] In one possible implementation, S102 specifically includes:

[0040] S1021: Set the input H(0) and output Y(0) of the identification system to 0;

[0041] S1022: Set the initial values ​​to be identified for the permanent magnet synchronous motor. The offline measured value for a permanent magnet synchronous motor or the reference resistance value provided by the permanent magnet synchronous motor manufacturer.

[0042] S103: Real-time acquisition of the electrical angular frequency, output torque, voltage command and phase current of the permanent magnet synchronous motor in the reference rotating coordinate system, and conversion of the phase current to the stator current in the reference rotating coordinate system.

[0043] It should be noted that the parameters acquired in real time in this invention are all readily available. Currently, there are already accurate methods for measuring the electrical angular frequency, output torque, voltage command in the reference rotating coordinate system, and phase current of permanent magnet synchronous motors. Using voltage command values ​​avoids the need for excessive sensors, reduces costs, and ensures that the command value and the actual value are within the allowable error range.

[0044] In one possible implementation, S103 specifically includes:

[0045] S1031: Obtain the electrical angular frequency of the permanent magnet synchronous motor through a rotor position estimation algorithm;

[0046] S1032: Use the command values ​​of the control system as the output torque and voltage command in the reference coordinate system of the permanent magnet synchronous motor;

[0047] S1033: Use a current sensor to obtain the phase current of the permanent magnet synchronous motor.

[0048] It should be noted that, in the entire process of identifying stator resistance, in addition to not relying on the rotor position information of the motor, no other motor parameters such as flux linkage and inductance are used. The speed, torque, current and voltage information introduced are all state variables of the motor, which can be obtained by direct measurement or bench calibration. The acquisition method is simple and has higher robustness.

[0049] In one possible implementation, S103 further includes:

[0050] S1034: The Clark transformation is used to convert the phase current into the stator current in a two-phase stationary coordinate system;

[0051] S1035: Based on the reference position angle, the stator current in the two-phase stationary coordinate system is converted into the stator current in the reference rotating coordinate system using the Park transformation.

[0052]

[0053] Among them, iα i β i represents the stator current in a two-phase stationary coordinate system. γ i δ θ represents the stator current in the reference rotating coordinate system. ref Indicates the reference position angle.

[0054] It is understandable that the reference rotating coordinate system is established based on the two-phase stationary coordinate system and the reference position angle. The obtained phase current is converted into the first stator current and the second stator current in the two-phase stationary coordinate system. Then, by further converting the first stator current and the second stator current in the two-phase stationary coordinate system through the reference position angle, the third stator current and the fourth stator current in the reference rotating coordinate system can be obtained.

[0055] S104: Input the electrical angular frequency, output torque, voltage command in the reference rotating coordinate system, and stator current in the reference rotating coordinate system into the construction module of the identification system.

[0056] It should be noted that the stator current in the reference coordinate system includes the third stator current and the fourth stator current.

[0057] S105: The construction module calculates the input and output of the identification system based on the recursive damped least squares method with forgetting factor.

[0058] In one possible implementation, S105 specifically includes:

[0059] S1051: Based on the electrical angular frequency, output torque, voltage command in the reference rotating coordinate system, and third and fourth stator currents in the reference rotating coordinate system, calculate the input H(k) and output Y(k) of the identification system:

[0060]

[0061] H(k) = -[i γ (k) 2 +i δ (k) 2 ]

[0062] Where k represents the number of iterations, T ref The output torque, w ref Represents the electric angular frequency, u γ and u δ This indicates the voltage command in the reference selection coordinate system, n p This indicates the number of pole pairs in a permanent magnet synchronous motor.

[0063] S106: Construct an identification iterative equation that does not contain rotor position information based on the input and output of the identification system, and identify the stator resistance of the permanent magnet synchronous motor through the identification iterative equation.

[0064] In one possible implementation, S106 specifically includes:

[0065] S1061: Construct intermediate variable P(k) based on the input of the identification system:

[0066] P(k) = 1 ÷ [μ + λ] 2 H(k-1) 2 +H(k) 2 ]

[0067] Where P(k) represents the intermediate variable, λ represents the forgetting factor, which takes a value between 0 and 1, and μ represents the damping coefficient, which takes a small positive value.

[0068] It should be noted that in recursive least squares with a forgetting factor, the forgetting factor emphasizes the importance of the current data while reducing the importance of previous data; this effect is more pronounced the closer the forgetting factor is to 0. Considering that the stator resistance changes with temperature at a relatively slow rate, it is unnecessary to excessively increase the influence of the current data on the identification results. A forgetting factor close to 1 is beneficial for improving the stability of the estimation results; therefore, a value close to 1 is recommended here. The damping coefficient can be greater than 1, and is generally chosen as a small positive number.

[0069] Optionally, the forgetting factor can be close to 1.

[0070] It should be noted that those skilled in the art can choose the size of the forgetting factor according to the actual situation, and no limitation is made here.

[0071] S1062: Construct the identification iterative equation by combining the intermediate variable P(k), the input H(k) of the identification system, and the output Y(k) of the identification system:

[0072]

[0073] in, This indicates the identification value of the stator resistance.

[0074] S1063: Identify the stator resistance of a permanent magnet synchronous motor using an identification iterative equation.

[0075] S107: Identification result of the stator resistance of the output permanent magnet synchronous motor.

[0076] In one possible implementation, the process after S107 includes:

[0077] S107A: Send the identification results to the control system.

[0078] It should be noted that the stator resistance obtained from the identification will be applied in real time to systems such as permanent magnet synchronous motor position observation, vector control, temperature detection, and fault protection to improve the control performance of the control system. In addition to its application within the control system, the stator resistance can also directly reflect the temperature change of the motor windings and be used in motor temperature detection and corresponding fault protection strategies.

[0079] S108: Repeat S103-S107 to iteratively identify the stator resistance.

[0080] It is understandable that the stator resistance of the permanent magnet synchronous motor is repeatedly iterated and the identification results are continuously output so that the control system can evaluate the operating status of the permanent magnet synchronous motor in real time based on the identification results, prevent unexpected faults, and provide a reference for the operation faults of the permanent magnet synchronous motor.

[0081] In this embodiment of the invention, without needing to obtain the rotor position information of the permanent magnet synchronous motor (PMSM), a reference position angle of the PMSM is obtained, and a reference rotating coordinate system of the PMSM is established. By obtaining the electrical angular frequency, output torque, voltage command, and phase current of the PMSM in the reference rotating coordinate system, the input and output of the identification system are calculated based on the recursive damped least squares method with a forgetting factor. Then, an identification iterative equation without rotor position information is constructed to identify the stator resistance. The parameter acquisition method used in the construction of the identification iterative equation is simple and the data is accurate. The rotor position information of the PMSM is not required in the entire construction process of the identification iterative equation, and the rotor position information is not required. This avoids the identification error of stator resistance caused by inaccurate rotor position information, and also avoids the problem of wasting a lot of computing resources and complex parameter debugging by artificial intelligence. This improves the accuracy of the stator resistance identification result, reduces the difficulty of stator resistance identification, and the stator resistance identification process is simple, fast, and highly stable.

[0082] The above description is merely an embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of the present invention should be included within the scope of the claims of the present invention.

Claims

1. A method for online identification of stator resistance that does not rely on rotor position information, characterized in that, An online identification method is applied to a stator resistance identification system, which includes a control system, an identification system, and a permanent magnet synchronous motor. The permanent magnet synchronous motor is directly connected to the identification system and is also connected to the identification system through the control system. The identification system includes a construction module. S101: Obtain the reference position angle of the permanent magnet synchronous motor, and establish a reference rotating coordinate system of the permanent magnet synchronous motor based on the reference position angle and the two-phase stationary coordinate system, wherein the rotational angular velocity of the reference rotating coordinate system is the same as the rotational angular velocity of the actual rotating coordinate system of the permanent magnet synchronous motor. S102: Initialize the identification system; S103: Real-time acquisition of the electrical angular frequency, output torque, voltage command and phase current of the permanent magnet synchronous motor in the reference rotating coordinate system, and conversion of the phase current to the stator current in the reference rotating coordinate system; S104: Input the electrical angular frequency, the output torque, the voltage command in the reference rotating coordinate system, and the stator current in the reference rotating coordinate system to the construction module of the identification system; S105: The construction module calculates the input and output of the identification system based on the recursive damped least squares method with forgetting factor; S106: Construct an identification iterative equation without rotor position information based on the input and output of the identification system, and identify the stator resistance of the permanent magnet synchronous motor through the identification iterative equation; S107: Output the identification result of the stator resistance of the permanent magnet synchronous motor; S108: Repeat S103-S107 to repeatedly identify the stator resistor; Specifically, the rotational angular velocity of the reference rotating coordinate system is made the same as the rotational angular velocity of the actual rotating coordinate system of the permanent magnet synchronous motor through a rotor position estimation algorithm. Specifically, S103 includes: S1031: Obtain the electrical angular frequency of the permanent magnet synchronous motor through the rotor position estimation algorithm; S1032: Use the command values ​​of the control system as the output torque of the permanent magnet synchronous motor and the voltage command in the reference coordinate system; S1033: Obtain the phase current of the permanent magnet synchronous motor using a current sensor; S103 further includes: S1034: The phase current is converted into stator current in a two-phase stationary coordinate system using Clark transformation; S1035: Based on the reference position angle, the stator current in the two-phase stationary coordinate system is converted into the stator current in the reference rotating coordinate system using the Park transformation: Among them, i α i β i represents the stator current in the two-phase stationary coordinate system. γ i δ θ represents the stator current in the reference rotating coordinate system. ref Indicates the reference position angle; Specifically, S105 includes: S1051: Calculate the input H(k) and output Y(k) of the identification system based on the electrical angular frequency, the output torque, the voltage command in the reference rotating coordinate system, and the third and fourth stator currents in the reference rotating coordinate system. Where k represents the number of iterations, T ref The output torque, w ref Represents the electrical angular frequency, u γ and u δ This represents the voltage command in the reference rotating coordinate system, n p This indicates the number of pole pairs of the permanent magnet synchronous motor; Specifically, S106 includes: S1061: Construct intermediate variable P(k) based on the input of the identification system: P(k)=1÷[μ+λ 2 H(k-1) 2 +H(k) 2 ] Wherein, P(k) represents the intermediate variable, λ represents the forgetting factor, which takes a value between 0 and 1, and μ represents the damping coefficient, which takes a small positive value; S1062: Construct the identification iterative equation by combining the intermediate variable P(k), the input H(k) of the identification system, and the output Y(k) of the identification system: in, Indicates the identification value of the stator resistance; S1063: The stator resistance of the permanent magnet synchronous motor is identified using the identification iterative equation.

2. The online stator resistance identification method according to claim 1, characterized in that, S101 specifically includes: S1011: Obtain the reference position angle of the permanent magnet synchronous motor; S1012: Use the reference position angle to perform a Park transformation on the two-phase stationary coordinate system to obtain the reference rotating coordinate system.

3. The online stator resistance identification method according to claim 1, characterized in that, S102 specifically includes: S1021: Set the input H(0) and output Y(0) of the identification system to 0; S1022: Set the initial value to be identified for the permanent magnet synchronous motor. The measured value of the permanent magnet synchronous motor is either an offline value or a reference resistance value provided by the manufacturer of the permanent magnet synchronous motor.

4. The online stator resistance identification method according to claim 1, characterized in that, The forgetting factor takes a value close to 1.

5. The online stator resistance identification method according to claim 1, characterized in that, Following S107, the following is also included: S107A: Send the identification result to the control system.

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