Demodulation Method of Back EMF Envelope of Exciter in Excitation System

Abstract

In the back-EMF envelope demodulation method of the exciter of the excitation system of the present application, a non-singular fast terminal sliding mode observer is used to obtain the current back-EMF observation value of the exciter. The process is simple to implement and has a good estimation effect. In addition, the non-singular fast terminal sliding mode observer can effectively reduce jitter and reduce the distortion of the observation results. In the present application, the current back-EMF observation value is recorded in the back-EMF observation value sequence, and a target back-EMF observation value that meets the preset interval condition with the current back-EMF observation value is determined. If the absolute value of the difference between the current back-EMF and the target back-EMF observation value is greater than a preset threshold, the current back-EMF observation value is determined as the back-EMF peak value. This process performs envelope demodulation according to the characteristics of the back-EMF of the exciter itself, which is convenient for quickly extracting back-EMF information and providing back-EMF information for a high-performance position sensorless control algorithm based on the exciter.

Description

Technical Field

[0001] The present application relates to the technical field of AC motor transmission control, and in particular to a method for demodulating the back electromotive force envelope of an exciter in an excitation system. Background Art

[0002] The three-stage motor is composed of the main motor, exciter, and auxiliary exciter installed coaxially. The exciter rotor winding and the main motor excitation winding are connected through a rotating rectifier. The main motor rotor position is the key information for starting control. In traditional technology, mechanical position sensors are installed to achieve starting control, but the utilization rate is extremely low, and the volume and weight are increased, and the reliability is reduced.

[0003] The rotating rectifier of the three-stage motor generates a large amount of harmonics during the starting process, and the excitation signal is naturally injected into the exciter; at the same time, the exciter and the main motor are coaxially installed, indicating that the exciter has operating characteristics similar to those of a rotary transformer, and can naturally be used as a position sensor for the main motor. This idea does not require changing the original motor structure, so that the exciter can have both excitation function and position sensor function, achieving dual use of one machine. This idea does not require additional injection of high-frequency signals. At the same time, the exciter has low power and simple working conditions, so the signal-to-noise ratio is relatively high, and it has good potential in high-performance position estimation. The back EMF of the exciter is the carrier of the exciter rotor position information, and accurately and quickly obtaining the back EMF information of the exciter is the key to realizing this idea. In order to facilitate the acquisition of back EMF information, a back EMF envelope demodulation method is urgently needed. Summary of the invention

[0004] Based on this, it is necessary to provide a method for back-EMF envelope demodulation of an excitation machine in an excitation system to address the problem in the prior art that there is no method for envelope demodulation using the back-EMF characteristics of the excitation machine in the excitation system.

[0005] A method for demodulating back electromotive force envelope of an exciter in an excitation system, comprising:

[0006] Obtaining a current back electromotive force observation value of the exciter through a non-singular fast terminal sliding mode observer;

[0007] Recording the current back electromotive force observation value in a back electromotive force observation value sequence, and determining a target back electromotive force observation value that satisfies a preset interval condition with the current back electromotive force observation value;

[0008] If the absolute value of the difference between the current back electromotive force observation value and the target back electromotive force observation value is greater than a preset threshold, the current back electromotive force observation value is determined as the back electromotive force peak value;

[0009] Back electromotive force envelope demodulation is performed according to the back electromotive force peak value.

[0010] In one embodiment, obtaining the current back electromotive force observation value of the exciter through a non-singular fast terminal sliding mode observer includes:

[0011] Collecting the three-phase voltage of the exciter stator, and calculating the target voltage according to the three-phase voltage;

[0012] Collecting the three-phase current of the stator of the exciter, and calculating the target sub-current according to the three-phase current;

[0013] The current back electromotive force observation value of the exciter is calculated according to the target sub-voltage, the target sub-current and a preset sliding mode surface.

[0014] In one embodiment, the process of determining the preset sliding mode surface in the non-singular fast terminal sliding mode observer includes:

[0015] The preset sliding mode surface is determined according to the target sub-current and an estimated value of the target sub-current by the non-singular fast terminal sliding mode observer.

[0016] In one embodiment, the calculation formula of the current back electromotive force observation value is:

[0017]

[0018] Among them, ε>0, η>0, R es is the resistance value of the exciter stator, L es is the stator inductance of the exciter, sgn(s) is the sign function, and

[0019] In one embodiment, the current back-EMF observation values ​​in the back-EMF observation value sequence are arranged in an acquisition order;

[0020] The step of recording the current back electromotive force observation value in the back electromotive force observation value sequence and determining a target back electromotive force observation value that satisfies a preset interval condition with the current back electromotive force observation value comprises:

[0021] The back electromotive force observation values ​​having a preset number of back electromotive force observation values ​​separated from the current back electromotive force observation value are determined as the target back electromotive force observation value.

[0022] In one embodiment, performing back-EMF envelope demodulation according to the back-EMF peak value includes: recording the back-EMF peak value in a back-EMF peak value sequence, and grouping the back-EMF peak value sequence according to preset values;

[0023] Envelope demodulation is performed according to the grouped back electromotive force peaks.

[0024] An exciter back electromotive force envelope demodulation device of an excitation system, comprising:

[0025] An acquisition module, used for acquiring a current back electromotive force observation value of the exciter;

[0026] A determination module, configured to record the current back electromotive force observation value in a back electromotive force observation value sequence, and determine a target back electromotive force observation value that satisfies a preset interval condition with the current back electromotive force observation value;

[0027] A data processing module, used for calculating the difference between the current back electromotive force observation value and the target back electromotive force observation value, and if the absolute value of the difference is greater than a preset threshold, determining the current back electromotive force observation value as a back electromotive force peak;

[0028] The envelope demodulation module is used to perform back electromotive force envelope demodulation according to the back electromotive force peak value.

[0029] In one embodiment, the exciter back electromotive force envelope demodulation device of the excitation system further includes:

[0030] A voltage acquisition module, used for acquiring the three-phase voltage of the stator of the exciter;

[0031] A current acquisition module, used for acquiring the three-phase current of the stator of the exciter;

[0032] An observation module is used to calculate the current back electromotive force observation value of the exciter according to the target sub-voltage, the target sub-current and a preset sliding surface.

[0033] In one embodiment, the observation module is further used to determine the preset sliding mode surface according to the target sub-current and an estimated value of the target sub-current by the non-singular fast terminal sliding mode observer.

[0034] In one embodiment, the observation module is specifically used to calculate the current back electromotive force observation value according to a calculation formula of the current back electromotive force observation value.

[0035] In one embodiment, the current back electromotive force observation values ​​in the back electromotive force observation value sequence in the determination module are arranged in an acquisition order;

[0036] The determination module is specifically used to determine a preset number of back electromotive force observation values ​​whose number of back electromotive force observation values ​​is spaced from the current back electromotive force observation value as the target back electromotive force observation value.

[0037] In one embodiment, the envelope demodulation module is specifically used to:

[0038] Recording the back electromotive force peak value in a back electromotive force peak value sequence, and grouping the back electromotive force peak value sequence according to preset values;

[0039] Envelope demodulation is performed according to the grouped back electromotive force peaks.

[0040] A computer device comprises a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps of any one of the above methods when executing the computer program.

[0041] A computer-readable storage medium stores a computer program, which implements the steps of any of the above methods when executed by a processor.

[0042] A computer program product comprises a computer program, which implements the steps of any one of the methods described above when executed by a processor.

[0043] In the back-EMF envelope demodulation method of the exciter of the excitation system described in the present application, a non-singular fast terminal sliding mode observer is used to obtain the current back-EMF observation value of the exciter; the current back-EMF observation value is recorded in the back-EMF observation value sequence, and a target back-EMF observation value that satisfies a preset interval condition with the current back-EMF observation value is determined; if the absolute value of the difference between the current back-EMF and the target back-EMF observation value is greater than a preset threshold, the current back-EMF observation value is determined as the back-EMF peak value; and back-EMF envelope demodulation is performed according to the back-EMF peak value. In the embodiment of the present application, the back-EMF peak value is determined by comparing the difference between the current back-EMF and the target back-EMF observation value with the preset threshold value, and then envelope demodulation is achieved through the back-EMF peak value. This process performs envelope demodulation according to the characteristics of the exciter back-EMF itself, which facilitates the rapid extraction of back-EMF information and provides back-EMF information for the high-performance position sensorless control algorithm of the three-stage motor based on the exciter. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the conventional technology, the drawings required for use in the embodiments or the conventional technology descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0045] Figure 1 It is a flow chart of the back electromotive force envelope demodulation method of the exciter in the excitation system;

[0046] Figure 2 It is a schematic diagram of the structure of a three-stage electrically excited brushless synchronous motor;

[0047] Figure 3 It is the structural diagram of the excitation system;

[0048] Figure 4 Flow chart for obtaining the current back electromotive force observation value of the exciter;

[0049] Figure 5 It is a schematic diagram of a three-phase bridge rectifier circuit;

[0050] Figure 6 This is the exciter rotor current waveform when the rotating rectifier is in commutation mode I;

[0051] Figure 7 is the equivalent circuit diagram of diodes D1 and D3 during commutation;

[0052] Figure 8 This is the exciter rotor current waveform when the rotating rectifier is in commutation mode II;

[0053] Fig. 9 is the exciter back EMF in commutation mode I;

[0054] Fig.10 is the exciter back EMF in commutation mode II;

[0055] Fig.11 A schematic diagram of a method for determining a target back-EMF observation value;

[0056] Fig.12 This is the simulation result diagram of the back-EMF envelope demodulation method of the exciter in the excitation system. DETAILED DESCRIPTION

[0057] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below through embodiments and in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0058] The serial numbers assigned to the components herein, such as "first", "second", etc., are only used to distinguish the objects described and do not have any order or technical meaning. The "connection" and "coupling" mentioned in this application, unless otherwise specified, include direct and indirect connections (couplings). In the description of this application, it should be understood that the orientation or position relationship indicated by the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", etc. are based on the orientation or position relationship shown in the accompanying drawings, which is only for the convenience of describing this application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to this application.

[0059] In the present application, unless otherwise clearly specified and limited, a first feature being “above” or “below” a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being “above”, “above”, and “above” a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being “below”, “below”, and “below” a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0060] like Figure 1 As shown, an embodiment of the present application provides a method for back-EMF envelope demodulation of an exciter in an excitation system. This embodiment uses the method applied to an electronic device as an example, and the electronic device is used to perform back-EMF envelope demodulation of an exciter. The exciter can be a multi-stage electrically excited brushless synchronous motor based on an excitation system, and the exciter can be a three-stage structure or a two-stage structure. Figure 2 It is a structural diagram of a three-stage electrically excited brushless synchronous motor. The three-stage structure includes a coaxially mounted main motor, an exciter and an auxiliary exciter, wherein the exciter rotor winding and the main motor rotor winding are connected through a rotating rectifier, the main motor includes a stator winding and a rotor winding, and the power module provides power to the main motor. The secondary structure includes a coaxially mounted main motor and an exciter. The method described in this embodiment can also be used to perform back-electromotive force envelope demodulation of a two-stage or three-stage motor with an exciter winding of two phases, three phases, or more than three phases. It can be understood that the method can also be applied to a server, and can also be applied to a system including an electronic device and a server, and is implemented through the interaction between the electronic device and the server.

[0061] Since the observed back EMF of the exciter is a segmented high-frequency signal, it needs to be envelope demodulated to remove the high-frequency component before it can be further used to extract position information. Since the exciter rotor injection signal is generated by the nonlinear operation of the rotating rectifier, it is impossible to directly obtain the synchronous sampling signal for envelope demodulation. Therefore, the embodiment of the present application proposes a method for envelope demodulation through the characteristics of the back EMF of the exciter itself, and the method includes the following steps:

[0062] S100, obtaining a current back electromotive force observation value of the exciter through a non-singular fast terminal sliding mode observer.

[0063] Among them, the non-singular fast terminal sliding mode observer can be determined by the state equation of the exciter.

[0064] Due to the sawtooth waveform of the exciter back EMF, the traditional sliding mode observer has large jitter, which will cause serious waveform distortion. In the embodiment of the present application, an exciter back EMF observation method based on a non-singular fast terminal sliding mode observer (NFTSMO) is adopted to facilitate the accurate and rapid extraction of the exciter back EMF. In addition, the implementation method of observing the exciter back EMF value through a non-singular fast terminal sliding mode observer is simple, the system has good robustness, and reduces jitter and distortion.

[0065] Further, the current back-EMF observation value of the exciter may include a first current back-EMF observation value and a second current back-EMF observation value. The first current back-EMF observation value corresponds to the back-EMF observation value on the first coordinate axis of the exciter stator. The second current back-EMF observation value corresponds to the back-EMF observation value on the second coordinate axis of the exciter stator. The first coordinate axis of the exciter stator may be the d-axis, and the second coordinate axis may be the q-axis. The first coordinate axis of the exciter stator may also be the q-axis, in which case the corresponding second coordinate axis is the d-axis. In this embodiment, the first coordinate axis is the d-axis and the second coordinate axis is the q-axis for illustration.

[0066] Specifically, the electronic device calculates the first target sub-voltage, the second target sub-voltage, the first target sub-current and the second target sub-current according to the collected three-phase voltage and three-phase current of the exciter stator. The first current back electromotive force observation value of the exciter stator is obtained through the non-singular fast terminal sliding mode observer, the first target sub-voltage and the first target sub-current. The second current back electromotive force observation value of the exciter stator is obtained through the non-singular fast terminal sliding mode observer, the second target sub-voltage and the second target sub-current. The first target sub-voltage is the target sub-voltage on the first coordinate axis of the exciter stator. The first target sub-current is the target sub-current on the first coordinate axis of the exciter stator. The second target sub-voltage is the target sub-voltage on the second coordinate axis of the exciter stator. The second target sub-current is the target sub-current on the second coordinate axis of the exciter stator. The first coordinate axis of the exciter stator can be α s axis, the second coordinate axis can be β s Axis. The first coordinate axis of the exciter stator can also be β s Axis, the corresponding second coordinate axis is α s In this embodiment, the first coordinate axis is α s axis, the second coordinate axis is β s The axis is used as an example for explanation.

[0067] Optionally, Figure 3 The structure shown is a schematic diagram of the excitation system structure, dq coordinate system and α s β s The coordinate systems coincide.s β s The coordinate system is fixed on the stator of the exciter, α r β r The coordinate system is fixed on the rotor of the exciter. esA ,u esB ,u esC is the stator phase voltage of the exciter; i esA ,i esB ,i esC is the stator phase current of the exciter; i era ,i erb , i erc is the exciter rotor phase current; i f is the main motor excitation current; θ er is the exciter rotor position, θ er =θ er0 +w ert ,θ er0 is the initial position of the exciter, w er is the electrical angular velocity of the exciter.

[0068] The stator voltage equation of the exciter is:

[0069]

[0070] In the formula, is the exciter stator α s β s Shaft voltage; is the exciter stator α s β s Shaft current; R es is the stator resistance of the exciter; L es is the stator inductance of the exciter; M em It is the mutual inductance between the stator and rotor of the exciter.

[0071] is the back EMF of the exciter d-axis and q-axis.

[0072] S200, recording the current back electromotive force observation value in a back electromotive force observation value sequence, and determining a target back electromotive force observation value that satisfies a preset interval condition with the current back electromotive force observation value.

[0073] Specifically, the current back electromotive force observation values ​​are arranged in the order of acquisition to form a back electromotive force observation value sequence. The electronic device can determine the target back electromotive force observation value according to the preset interval condition. The back electromotive force observation value sequence may include a first back electromotive force observation value sequence and a second back electromotive force observation value sequence. The first back electromotive force observation value sequence is composed of the first current back electromotive force observation value, and the second back electromotive force observation value sequence is composed of the second current back electromotive force observation value. The preset interval condition may include a first preset interval condition and a second preset interval condition. The target back electromotive force observation value may include a first target back electromotive force observation value and a second target back electromotive force observation value. The electronic device may determine a first target back electromotive force observation value in the first back electromotive force observation value sequence that satisfies the first preset interval condition with the first current back electromotive force observation value. The electronic device may determine a second target back electromotive force observation value in the second back electromotive force observation value sequence that satisfies the second preset interval condition with the second current back electromotive force observation value.

[0074] S300: If the absolute value of the difference between the current back electromotive force observation value and the target back electromotive force observation value is greater than a preset threshold, the current back electromotive force observation value is determined as a back electromotive force peak value.

[0075] Specifically, the preset threshold may include a first preset threshold and a second preset threshold. The back electromotive force peak may include a first back electromotive force peak and a second back electromotive force peak.

[0076] If the absolute value of the difference between the first current back electromotive force observation value and the first target back electromotive force observation value is greater than the first preset threshold, the first current back electromotive force observation value is determined as the first back electromotive force peak value.

[0077] If the absolute value of the difference between the second current back electromotive force observation value and the second target back electromotive force observation value is greater than the second preset threshold, the second current back electromotive force observation value is determined as the second back electromotive force peak value.

[0078] S400, performing back electromotive force envelope demodulation according to the back electromotive force peak value.

[0079] Specifically, the back electromotive force envelope includes a first back electromotive force envelope and a second back electromotive force envelope. The electronic device can demodulate the first back electromotive force envelope according to the first back electromotive force peak value. The electronic device can also demodulate the second back electromotive force envelope according to the second back electromotive force peak value.

[0080] In the above-mentioned excitation system back-EMF envelope demodulation method, the implementation method of obtaining the current back-EMF observation value of the excitation machine through a non-singular fast terminal sliding mode observer is simple in steps and has a good estimation effect. In addition, the non-singular fast terminal sliding mode observer can effectively reduce jitter and reduce the distortion of the observation result. In addition, in the embodiment of the present application, the back-EMF peak value is determined by comparing the difference between the current back-EMF and the target back-EMF observation value with a preset threshold, and then envelope demodulation is achieved through the back-EMF peak value. This process performs envelope demodulation according to the characteristics of the excitation machine back-EMF itself, which is convenient for quickly extracting back-EMF information and providing back-EMF information for the high-performance position sensorless control algorithm of the three-stage motor based on the excitation machine.

[0081] See also Figure 4 In one embodiment, obtaining the current back electromotive force observation value of the exciter through a non-singular fast terminal sliding mode observer comprises:

[0082] S110, collecting the three-phase voltage of the exciter stator, and calculating the target sub-voltage according to the three-phase voltage;

[0083] S120, collecting the three-phase current of the stator of the exciter, and calculating the target sub-current according to the three-phase current;

[0084] Specifically, the first target sub-voltage and the second target sub-voltage are calculated based on the three-phase voltage pre-applied on the stator side of the exciter and the first preset coordinate system conversion formula. Similarly, the first target sub-current and the second target sub-current are calculated based on the three-phase current of the stator of the exciter and the second preset coordinate system conversion formula.

[0085] Furthermore, the three-phase voltage is pre-applied on the stator side of the exciter with an angular frequency of ω e1 The three-phase symmetrical voltage, including the A phase voltage u esA 、B phase voltage u esB And the C phase voltage u esC The first preset coordinate system conversion formula is to convert the three-phase voltage into the exciter's α s β s The coordinate system conversion calculation formula required for the voltage on the coordinate system. The three-phase current includes the A phase current i esA 、B phase current i esB And the C phase current i esC The second preset coordinate system conversion formula is to convert the three-phase current into the exciter's α s β s The coordinate system transformation calculation formula required for the electric current on the coordinate system.

[0086] Alternatively, the three-phase stator voltage of the exciter can be converted to α by the following formula s β sVoltage on the coordinate system:

[0087]

[0088] in, is the α of the exciter stator s Shaft voltage, is the β of the exciter stator s Shaft voltage, u esA , u esB 、u esC is the three-phase voltage collected on the stator side of the exciter, and the above constant matrix is ​​the conversion coefficient of the first preset coordinate system.

[0089] The three-phase stator current of the exciter can be converted to α by the following formula s β s Current in the coordinate system:

[0090]

[0091] in, is the α of the exciter stator s Shaft current, is the β of the exciter stator s Shaft current, i esA ,i esB ,i esC is the three-phase current collected on the stator side of the exciter, and the above constant matrix is ​​the conversion coefficient of the second preset coordinate system.

[0092] S130, calculating the current back electromotive force observation value of the exciter according to the target sub-voltage, the target sub-current and a preset sliding mode surface.

[0093] Specifically, the first current back electromotive force observation value of the exciter is calculated according to the first target sub-voltage, the first target sub-current and the first preset sliding mode surface, and the calculation steps of the second back electromotive force observation value are the same and will not be repeated.

[0094] Due to the sawtooth waveform of the exciter back EMF, the traditional sliding mode observer has large jitter, which will cause serious waveform distortion. In the embodiment of the present application, an exciter back EMF observation method based on a non-singular fast terminal sliding mode observer (NFTSMO) is adopted to facilitate the accurate and rapid extraction of the exciter back EMF. In addition, the implementation method of observing the exciter back EMF value through a non-singular fast terminal sliding mode observer is simple, the system has good robustness, and reduces jitter and distortion.

[0095] In one embodiment, the process of determining the preset sliding mode surface in the non-singular fast terminal sliding mode observer includes:

[0096] The preset sliding mode surface is determined according to the target sub-current and an estimated value of the target sub-current by the non-singular fast terminal sliding mode observer.

[0097] Specifically, the calculation formula of the preset sliding surface is:

[0098]

[0099] in, i es is the target sub-current, is the estimated value of the target sub-current of the non-singular fast terminal sliding mode observer, is the derivative of e, m>0, n>0, g, h, p, q are all odd numbers,

[0100] The preset sliding surface includes a first preset sliding surface and a second preset sliding surface. Taking the d-axis back electromotive force observation value as an example, the first preset sliding surface of the non-singular fast terminal sliding mode observer is

[0101]

[0102] Similarly, the second preset sliding film surface of the non-singular fast terminal sliding mode observer is

[0103]

[0104] Please also see Figure 5 ,pass Figure 5 The three-phase bridge rectifier circuit shown is used to analyze the excitation system. era , e erb , e erc is the equivalent induced potential of the exciter rotor; L γ The following assumptions are made for the three-phase bridge rectifier circuit: ① The on-resistance of the diode is zero and the reverse resistance is infinite; ② The inductance of the excitation winding of the main motor is very large, and the excitation current i f It is direct current and has no fluctuation component; ③ The equivalent commutation resistance is negligible.

[0105] For a rotating rectifier, common commutation modes include commutation mode I and commutation mode II, which are discussed below respectively.

[0106] When the rotating rectifier is in commutation mode I, the exciter rotor current waveform is as follows: Figure 6 As shown, γ is the commutation angle, 0<γ≤π / 3.

[0107] When D1 and D3 are in phase change (0-t1), the equivalent circuit of the three-phase bridge rectifier circuit can be expressed as Figure 7 , the corresponding circuit equation is

[0108]

[0109] Among them, e era , e erb , e erc for

[0110]

[0111] Where: E m is the equivalent induced potential amplitude of the exciter rotor; ω e1 is the angular frequency of the equivalent induced electromotive force of the exciter rotor.

[0112] From the above two formulas, we can get

[0113]

[0114] Considering the low motor speed, the di during the commutation period of D1 and D3 can be approximately calculated. erd / dt、di erq / dt is

[0115]

[0116] Therefore, e erd 、e erq for

[0117]

[0118] During the rest of the commutation period, e erd 、e erq The expression is shown in Table 1, and the calculation process will not be repeated here.

[0119] Table 1 Expression of exciter back EMF in commutation mode I

[0120]

[0121]

[0122] When the rotating rectifier is in commutation mode II, the exciter rotor current waveform is as follows: Figure 8 As shown, α is the commutation delay angle, 0<α≤π / 6.

[0123] When D1 and D3 are in phase change (0-t1), the equivalent circuit of the three-phase bridge rectifier circuit is as follows: Figure 7 As shown, the corresponding circuit equation is

[0124]

[0125] Among them, e era , e erb , eerc for

[0126]

[0127] Through a derivation process similar to that of commutation mode I, the expression of the back EMF during commutation mode II is obtained as shown in Table 2, and the calculation process is not repeated here.

[0128] Table 2 Expression of exciter back EMF in commutation mode II

[0129]

[0130]

[0131] Based on this, the back EMF characteristics of the exciter can be obtained. From Table 1, the back EMF waveform of the exciter in commutation mode I can be obtained, and the waveform is shown in Figure 9.

[0132] Similarly, the back EMF waveform of the exciter in commutation mode II can be obtained from Table 2. Fig.10 shown.

[0133] For commutation mode I, when t=t1, w e1 t1=γ. At this time, the back electromotive force of the exciter is

[0134]

[0135] Since 0<γ≤π / 3, e erq (t = t1) and e erq (t=t1) is the peak value during the commutation period of D1 and D3.

[0136] For commutation mode II, when t=t1,

[0137] At this time, the back EMF of the exciter is

[0138]

[0139] Since 0<α≤π / 6, e erq (t = t1) and e erq (t=t1) is the peak value during the commutation period of D1 and D3.

[0140] Similarly, for other commutation states under commutation modes I and II, the exciter back EMF also reaches its peak value at the end of commutation. After that, the absolute value of the exciter back EMF suddenly decreases and jumps, forming Fig. 9 and Fig.10 The sawtooth waveform shown.

[0141] Based on the sawtooth waveform of the exciter back EMF, the traditional sliding mode observer has large jitter, which will cause serious waveform distortion. In the embodiment of the present application, an exciter back EMF observation method based on a non-singular fast terminal sliding mode observer is adopted to achieve accurate and rapid extraction of the exciter back EMF, while reducing jitter and distortion.

[0142] Please also see Figure 3 , the state equation of the exciter can be expressed as

[0143]

[0144] Based on this, the design of the non-singular fast terminal sliding mode observer is as follows

[0145]

[0146] In the formula, yes The estimated value of Yes erd 、e erq The estimated value of .

[0147] Subtracting the above two equations, we can get

[0148]

[0149] With e erd As an example, the sliding surface of NFTSMO is selected as

[0150]

[0151] In the formula, m>0, n>0, g, h, p, q are odd numbers,

[0152] In the e erq During observation, the sliding surface design steps of NFTSMO are similar to those mentioned above, and the process will not be repeated here.

[0153] Since the load state of the exciter will affect the magnitude of the back EMF, and the stator current of the exciter will change greatly when the exciter is under high speed and heavy load. Therefore, it is more reasonable to determine a non-singular fast terminal sliding mode observer for estimating the back EMF based on the state equation of the exciter. Due to the sawtooth waveform of the back EMF of the exciter, the embodiment of the present application adopts a method for observing the back EMF of the exciter based on a non-singular fast terminal sliding mode observer, which facilitates the accurate and rapid extraction of the back EMF of the exciter, reduces jitter, and reduces distortion.

[0154] In one embodiment, the calculation formula of the current back electromotive force observation value is:

[0155]

[0156] Among them, ε>0, η>0, R es is the resistance value of the exciter stator, L es is the inductance of the exciter stator, sgn(s) is the sign function, and

[0157] Specifically, the first current back electromotive force observation value can be calculated based on the resistance value, inductance value, first target sub-voltage, and first target sub-current of the exciter stator, and the second current back electromotive force observation value calculation process is similar.

[0158] The calculation formula for the first current back EMF observation value is:

[0159]

[0160] Since the d and q axes are symmetrical, the ε, η, m, n, g, h, p, and q parameters of the d and q axes can be selected to be consistent, so the calculation formula for the second current back electromotive force observation value is:

[0161]

[0162] Furthermore, the non-singular fast terminal sliding mode observer in the embodiment of the present application needs to satisfy the Lyapunov stability theorem.

[0163] Select the Lyapunov function as but

[0164]

[0165] set up The upper limit of the absolute value is E, that is, Therefore, if it satisfies

[0166] So,

[0167]

[0168] It satisfies Lyapunov's stability theorem.

[0169] Similarly, we select the Lyapunov function as but

[0170]

[0171] set up The upper limit of the absolute value is E, that is, Therefore, if it satisfies

[0172] So,

[0173]

[0174] It satisfies Lyapunov's stability theorem.

[0175] The non-singular fast terminal sliding mode observer in the embodiment of the present application satisfies the Lyapunov stability theorem, can ensure that the observed back-electromotive force value is consistent with the actual back-electromotive force value, and the acquired waveform is not easily distorted and has good stability.

[0176] In one embodiment, the current back-EMF observation values ​​in the back-EMF observation value sequence are arranged in an acquisition order;

[0177] The step of recording the current back electromotive force observation value in the back electromotive force observation value sequence and determining a target back electromotive force observation value that satisfies a preset interval condition with the current back electromotive force observation value comprises:

[0178] The back electromotive force observation values ​​whose number of intervals from the current back electromotive force observation value is a preset number are determined as the target back electromotive force observation values.

[0179] Specifically, the preset number may be 3, that is, there are 3 back electromotive force observation values ​​between the current back electromotive force observation value and the target back electromotive force observation value. The preset number includes but is not limited to 3.

[0180] Furthermore, the target back EMF observation value includes a first target back EMF observation value and a second target back EMF observation value. In one embodiment, a first array is constructed to store the first current back EMF observation value. When the first current back EMF observation value is obtained, all first back EMF observation values ​​in the first array are shifted back by one position, and the first current back EMF observation value is placed at the first position of the first array. The first back EMF observation value at the last position of the first array is the first target back EMF observation value. The steps for determining the second target EMF observation value of the second current back EMF observation value are the same as above and will not be repeated.

[0181] For details, please refer to Fig.11 , the method for determining the target back EMF observation value includes: setting a first array containing n elements to save the first current back EMF observation value; the first array adopts a first-in-first-out update method, that is, each time a new first current back EMF observation value is obtained, all elements in the array are shifted back one position as a whole, and the last position is moved out of the array, and the new exciter back EMF observation value is saved in the array position "1". The first back EMF observation value at the array position "n" is the first target back EMF observation value. The steps for determining the second target back EMF observation value are the same as above and will not be repeated.

[0182] In one embodiment, performing back EMF envelope demodulation according to the back EMF peak value includes: recording the back EMF peak value in a back EMF peak value sequence, and grouping the back EMF peak value sequence according to preset values; and performing envelope demodulation according to the grouped back EMF peak value.

[0183] It can be seen from Table 1 and Table 2 that the exciter back electromotive force expression is repeated every 6 commutation states, so the preset value can be 6, and the detected peak values ​​are grouped with a period of 6. The peak points at the same position in each group are connected, so the first back electromotive force observation value and the second back electromotive force observation value can obtain 6 back electromotive force envelopes respectively.

[0184] In summary, the embodiment of the present application realizes envelope demodulation through the back EMF peak value. This process performs envelope demodulation according to the characteristics of the back EMF of the exciter itself, which facilitates the rapid extraction of back EMF information and provides back EMF information for the high-performance position sensorless control algorithm of the three-stage motor based on the exciter.

[0185] In one embodiment, MATLAB / Simulink is used to simulate and verify the method of the present application, and the simulated motor model mainly comes from the Simscape simulation library. A wound-rotor asynchronous motor model is used as an exciter, and an electrically excited synchronous motor model is used as a main motor. A rotating rectifier is built through a diode to connect the rotor winding of the exciter and the excitation winding of the main motor. Since the auxiliary exciter does not work in this method, it is not considered in the simulation model. The main motor is driven to rotate by vector control.

[0186] In the embodiment of the present application, the back electromotive force envelope demodulation method of the exciter in the excitation system includes:

[0187] (1) Estimate the back EMF of the exciter, including:

[0188] (a) Collect the exciter stator voltage and current:

[0189] (a.1) Apply a 50V / 200Hz three-phase symmetrical voltage u to the stator winding of the exciter through the three-phase power module provided by the simulation software. esA ,u esB ,u esC ;

[0190] (a.2) The exciter stator α is obtained by the first preset coordinate system conversion formula s β s Shaft voltage

[0191]

[0192] (a.3) Collect the three-phase stator current i of the exciteresA ,i esB ,i esC ;

[0193] (a.4) The exciter stator α is obtained by the second preset coordinate system conversion formula s β s Shaft current

[0194]

[0195] (b) Exciter back EMF observation, including:

[0196] (b.1) Input exciter parameters R es =0.25Ω, L es =0.0037H, set ε=80×10 4 , η=6×10 4 , m=0.1,n=0.1,g=29,h=27,p=57,q=55 parameters, obtain the observed value of the exciter d-axis back EMF

[0197]

[0198] (b.2) Input exciter parameters R es =0.25Ω, L es =0.0037H, set ε=80×10 4 , η=6×10 4 , m=0.1,n=0.1,g=29,h=27,p=57,q=55 parameter values, obtain the exciter q axis back EMF observation value

[0199]

[0200] (3) Observation value of exciter back electromotive force Perform envelope demodulation, including:

[0201] (a) Observation value of exciter back EMF Perform envelope demodulation, including:

[0202] (a.1) Set up an array containing 5 elements;

[0203] (a.2) Each time a new exciter d-axis back EMF observation value is obtained After that, all elements in the array are shifted back one position as a whole, the last bit is moved out of the array, and then the new exciter back EMF observation value is saved in the array position "1".

[0204] (a.3) The observed values ​​of the exciter d-axis back EMF stored in array position "1" and array position "n" If the absolute value of the difference is greater than the preset threshold value of 80, it is considered that the exciter back electromotive force has jumped, that is, a Peak

[0205] (a.4) Peak value with a period of 6 Group the data and connect the peak points at the same position in each group.

[0206] (b) Observation value of exciter back EMF Perform envelope demodulation, including:

[0207] (a.1) Set up an array containing 5 elements;

[0208] (a.2) Each time a new exciter q-axis back EMF observation value is obtained After that, all elements in the array are shifted back one position as a whole, the last bit is moved out of the array, and then the new exciter back EMF observation value is saved in the array position "1".

[0209] (a.3) The observed values ​​of the exciter q-axis back EMF stored in array position "1" and array position "n" If the absolute value of the difference is greater than the preset threshold value of 80, it is considered that the exciter back electromotive force has jumped, that is, a Peak

[0210] (a.4) Peak value with a period of 6 Group them and then connect them.

[0211] Please also see Fig.12 Through the above steps, the observation and envelope demodulation of the exciter back EMF can be realized. Fig.12 In the figure, the waveforms of the estimated values ​​of the back EMF of the d and q axes are sawtooth-shaped, which is consistent with the theoretical analysis. In addition, the estimated values ​​of the back EMF of the d and q axes each contain 6 envelopes.

[0212] The embodiment of the present application provides an exciter back electromotive force envelope demodulation device of an excitation system, comprising:

[0213] An acquisition module, used for acquiring a current back electromotive force observation value of the exciter;

[0214] A determination module, configured to record the current back electromotive force observation value in a back electromotive force observation value sequence, and determine a target back electromotive force observation value that satisfies a preset interval condition with the current back electromotive force observation value;

[0215] A data processing module, used for calculating the difference between the current back electromotive force observation value and the target back electromotive force observation value, and if the absolute value of the difference is greater than a preset threshold, determining the current back electromotive force observation value as a back electromotive force peak;

[0216] The envelope demodulation module is used to perform back electromotive force envelope demodulation according to the back electromotive force peak value.

[0217] In one embodiment, the exciter back electromotive force envelope demodulation device of the excitation system further includes:

[0218] A voltage acquisition module, used for acquiring the three-phase voltage of the stator of the exciter;

[0219] A current acquisition module, used for acquiring the three-phase current of the stator of the exciter;

[0220] An observation module is used to calculate the current back electromotive force observation value of the exciter according to the target sub-voltage, the target sub-current and a preset sliding surface.

[0221] In one embodiment, the observation module is further used to determine the preset sliding mode surface according to the target sub-current and an estimated value of the target sub-current by the non-singular fast terminal sliding mode observer.

[0222] In one embodiment, the observation module is specifically used to calculate the current back electromotive force observation value according to a calculation formula of the current back electromotive force observation value.

[0223] In one embodiment, the current back electromotive force observation values ​​in the back electromotive force observation value sequence in the determination module are arranged in an acquisition order;

[0224] The determination module is specifically used to determine a preset number of back electromotive force observation values ​​whose number of back electromotive force observation values ​​is spaced from the current back electromotive force observation value as the target back electromotive force observation value.

[0225] In one embodiment, the envelope demodulation module is specifically used to:

[0226] Recording the back electromotive force peak value in a back electromotive force peak value sequence, and grouping the back electromotive force peak value sequence according to preset values;

[0227] Envelope demodulation is performed according to the grouped back electromotive force peaks.

[0228] In one embodiment, a computer device is provided, comprising a memory and a processor. The memory stores a computer program. When the processor executes the computer program, the steps of the above method are implemented.

[0229] In one embodiment, a computer readable storage medium is provided, on which a computer program is stored. When the computer program is executed by a processor, the steps of the above method are implemented.

[0230] In one embodiment, a computer program product is provided, comprising a computer program. When the computer program is executed by a processor, the steps of the above method are implemented.

[0231] Those of ordinary skill in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it may include the processes of the embodiments of the above-mentioned methods. Among them, any reference to a memory, a database or other medium used in the embodiments provided in this application may include at least one of a non-volatile and volatile memory. The database involved in the embodiments provided in this application may include at least one of a relational database and a non-relational database. Non-relational databases may include distributed databases based on blockchains, etc., but are not limited thereto. The processors involved in the embodiments provided in this application may be general-purpose processors, central processing units, graphics processors, digital signal processors, programmable logic devices, data processing logic devices based on quantum computing, etc., but are not limited thereto.

[0232] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0233] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. A method for demodulating the back electromotive force envelope of an exciter in an excitation system, characterized in that: The method comprises: Obtaining a current back electromotive force observation value of the exciter through a non-singular fast terminal sliding mode observer; Recording the current back electromotive force observation value in a back electromotive force observation value sequence, and determining a target back electromotive force observation value that satisfies a preset interval condition with the current back electromotive force observation value; If the absolute value of the difference between the current back electromotive force observation value and the target back electromotive force observation value is greater than a preset threshold, the current back electromotive force observation value is determined as the back electromotive force peak value; Performing back electromotive force envelope demodulation according to the back electromotive force peak value; The method of obtaining the current back electromotive force observation value of the exciter by the non-singular fast terminal sliding mode observer includes: collecting the three-phase voltage of the stator of the exciter, and calculating the target sub-voltage according to the three-phase voltage; collecting the three-phase current of the stator of the exciter, and calculating the target sub-current according to the three-phase current; and calculating the current back electromotive force observation value of the exciter according to the target sub-voltage, the target sub-current and a preset sliding mode surface. The process of determining the preset sliding surface in the non-singular fast terminal sliding mode observer includes: determining the preset sliding surface according to the target sub-current and the estimated value of the target sub-current by the non-singular fast terminal sliding mode observer; the calculation formula of the current back electromotive force observation value is: in, , , is the resistance value of the exciter stator, is the stator inductance of the exciter, is a symbolic function, and , The back electromotive force envelope demodulation according to the back electromotive force peak value comprises: recording the back electromotive force peak value in a back electromotive force peak value sequence, and grouping the back electromotive force peak value sequence according to preset values; and performing envelope demodulation according to the grouped back electromotive force peak value.

2. The method for demodulating the back electromotive force envelope of an exciter in an excitation system according to claim 1, characterized in that: The current back electromotive force observation values ​​in the back electromotive force observation value sequence are arranged in an acquisition order; The step of recording the current back electromotive force observation value in the back electromotive force observation value sequence and determining a target back electromotive force observation value that satisfies a preset interval condition with the current back electromotive force observation value comprises: The back electromotive force observation values ​​having a preset number of back electromotive force observation values ​​separated from the current back electromotive force observation value are determined as the target back electromotive force observation value.

3. A back electromotive force envelope demodulation device for an excitation system, characterized in that: The device comprises: An acquisition module, used for acquiring a current back electromotive force observation value of the exciter through a non-singular fast terminal sliding mode observer; A determination module, configured to record the current back electromotive force observation value in a back electromotive force observation value sequence, and determine a target back electromotive force observation value that satisfies a preset interval condition with the current back electromotive force observation value; A data processing module, used for calculating the difference between the current back electromotive force observation value and the target back electromotive force observation value, and if the absolute value of the difference is greater than a preset threshold, determining the current back electromotive force observation value as the back electromotive force peak value; An envelope demodulation module, used for performing back electromotive force envelope demodulation according to the back electromotive force peak value; The acquisition module is specifically used to collect the three-phase voltage of the exciter stator and calculate the target sub-voltage according to the three-phase voltage; collect the three-phase current of the exciter stator and calculate the target sub-current according to the three-phase current; calculate the current back electromotive force observation value of the exciter according to the target sub-voltage, the target sub-current and a preset sliding surface; The process of determining the preset sliding surface in the non-singular fast terminal sliding mode observer includes: determining the preset sliding surface according to the target sub-current and the estimated value of the target sub-current by the non-singular fast terminal sliding mode observer; the calculation formula of the current back electromotive force observation value is: in, , , is the resistance value of the exciter stator, is the stator inductance of the exciter, is a symbolic function, and , The envelope demodulation module is specifically used to record the back electromotive force peak value in the back electromotive force peak value sequence, and group the back electromotive force peak value sequence according to preset values; and perform envelope demodulation according to the grouped back electromotive force peak value.

4. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 2 are implemented.

5. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 2 are implemented.

6. A computer program product comprising a computer program, characterized in that When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 2 are implemented.

Images