A method for optimizing low-speed performance of speed sensorless asynchronous motor control

Abstract

The present invention discloses a method for optimizing the low-speed performance of speed sensorless asynchronous motor control, comprising: constructing a full-order observer model composed of observation quantities; obtaining the unstable critical frequency of the full-order observer model, and obtaining a constraint that satisfies the observed speed stability by shrinking the critical frequency to zero; establishing a critical frequency expression under stator resistance mismatch conditions to obtain a first feedback gain constraint that can weaken the critical frequency offset phenomenon caused by stator resistance changes; establishing a ratio function of observed flux to true flux under stator resistance mismatch conditions to obtain a second feedback gain constraint that minimizes the flux observation error; and determining the feedback gain coefficient in the full-order observer model based on the feedback gain constraint to obtain a final full-order observer, which is then used for motor control. The method disclosed in the present invention solves the system stability problem under low-speed power generation conditions, improves the parameter robustness of the observer, and reduces the flux observation error.

Description

Technical Field

[0001] The invention relates to a method for optimizing low-speed performance of speed sensorless asynchronous motor control, belonging to the technical field of motor control. Background Art

[0002] While many theoretical solutions exist for addressing the low-speed power generation instability problem in sensorless asynchronous drive systems, relatively little research has been conducted under conditions of motor parameter mismatch. The ability to address low-speed power generation instability is inherently linked to motor parameter mismatch. Designing a global stability observer inevitably requires the use of boundary conditions, such as the Routh criterion or Lyapunov stability theory, to determine the necessary and sufficient conditions for observing speed stability. The subsequent selection of feedback gains also involves a large number of motor parameters. Therefore, changes in motor parameters can violate these boundary constraints, rendering the observer unstable again.

[0003] Furthermore, the observer model constructed based on the motor model inevitably exhibits deviations when motor parameters do not match, which in turn affects the accuracy of flux observation. Flux observation errors are particularly pronounced at low motor speeds, further deteriorating the system's performance under extremely low speed conditions. While efforts have been made to improve the robustness of the observer, these efforts have not yet fully addressed the system's instability issues under low-speed power generation conditions.

[0004] Therefore, how to solve the problem of unstable operation of the speed sensorless asynchronous drive system under low-speed power generation conditions and establish an observer with strong robustness to the motor parameters is a problem that needs further research. Summary of the Invention

[0005] In order to overcome the above problems, the inventors have conducted in-depth research and proposed a method for optimizing the low-speed performance of a speed sensorless asynchronous motor control, comprising the following steps:

[0006] S1. Establish a motor model through the stator voltage, current and rotor flux of the asynchronous motor, and construct a full-order observer model composed of observation quantities based on the motor model;

[0007] S2. Obtain the unstable critical frequency of the full-order observer model based on the motor parameters, and obtain the constraint that satisfies the observed speed stability by shrinking the critical frequency to zero;

[0008] S3. Establishing a critical frequency expression under stator resistance mismatch conditions to obtain a second feedback gain constraint that can weaken the critical frequency shift phenomenon caused by stator resistance variation;

[0009] S4. Establish a function of the ratio of the observed flux to the actual flux under the condition of stator resistance mismatch, and obtain the feedback gain constraint that minimizes the flux observation error;

[0010] S5. Determine the feedback gain coefficient in the full-order observer model by combining the first feedback gain constraint and the second feedback gain constraint to obtain a final full-order observer, and use the full-order observer to control the motor.

[0011] In a preferred embodiment, in S1, the motor model is expressed as:

[0012]

[0013] Among them, i s represents the stator current, ψ r represents the rotor flux, u s represents the stator voltage; p is the derivative symbol, a 11 、a 12 、a 21 、a 22 , b are coefficient parameters;

[0014] The stator current, rotor flux, and stator voltage are expressed as:

[0015] i s =i sd +ji sq

[0016] ψ r =ψ rd +jψ rq

[0017] u s =u sd +ju sq

[0018] Among them, i sd is the d-axis component of the stator current, i sq is the q-axis component of the stator current; ψ rd The d-axis component of the rotor flux, ψ rq is the q-axis component of the rotor flux; u sd is the d-axis component of the stator voltage, u sq is the q-axis component of the stator voltage, and j is the imaginary unit.

[0019] In a preferred embodiment, the coefficient parameters are set to:

[0020] a 11 =a1-jω e , a 12 =a2(1 / T r -jω r ),

[0021] a 21 =Lm / T r , a 22 =-1 / T r -j(ω e -ω r ),

[0022] a1=-(R s / (σL s )+a2L m / T r ), a2=L m / (σL s L r ), b=1 / (σL s ),

[0023] T r =L r / R r

[0024] Among them, a1 and a2 are intermediate quantities, σ is the magnetic leakage coefficient, T r is the rotor time constant; ω e is the synchronous angular velocity, ω r is the rotor electrical angular velocity; R s is the stator resistance, R r is the rotor resistance; L s is the stator inductance, L r is the rotor inductance, L m It is mutual induction.

[0025] In a preferred embodiment, the full-order observer model is expressed as:

[0026]

[0027] K1=g1+jg2,K2=g3+jg4

[0028] in, represents the observed quantity of stator current, represents the observed quantity of the rotor flux, Represents the coefficient parameter a 12 The observed quantity, Represents the coefficient parameter a 22 , K1 and K2 are intermediate variables, and g1, g2, g3, and g4 are feedback gain coefficients.

[0029] In a preferred embodiment, in S2, the unstable critical frequency is expressed as:

[0030] ω c =-(yω r +z / T r) / x

[0031] x=-a1+g1+1 / T r , y=a1-g1-a2g3+a2L m / T r , z=g2+a2g4

[0032] Among them, ω c is the unstable critical frequency, and x, y, and z are all intermediate variables.

[0033] In a preferred embodiment, in S3, the critical frequency expression under the stator resistance mismatch condition is:

[0034] ω c =ΔR s / (σL s ) / xω r

[0035] in, is the stator resistance error, Represents the stator resistance parameter used in the observer.

[0036] In a preferred embodiment, the first feedback gain constraint that can weaken the critical frequency shift phenomenon caused by the stator resistance change is expressed as:

[0037] g1>>R s / (σL s ).

[0038] In a preferred embodiment, the second feedback gain constraint that minimizes the flux linkage observation error is expressed as:

[0039] g1>>R s / (σL s )

[0040] g3=g4=0.

[0041] In a preferred embodiment, in S5, by combining the first feedback gain constraint and the second feedback gain constraint, and the unstable critical frequency obtained in S2, g2=T r (R s / (σL s )+g1)ω r , thus the feedback gain coefficient in the full-order observer model is obtained, which is expressed as:

[0042]

[0043] Among them, k is a configurable parameter.

[0044] In a preferred embodiment, the parameter k can be set to

[0045] Among them, k1 is a configurable constant.

[0046] The beneficial effects of the present invention include:

[0047] (1) It not only solves the system stability problem under low-speed power generation conditions, but also effectively improves the parameter robustness of the observer and reduces the flux observation error;

[0048] (2) The critical frequency offset problem caused by parameter mismatch is improved, especially it has strong resistance to changes in stator resistance, and can still shrink the unstable operation range to zero under the condition of stator resistance mismatch. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 A schematic flow chart of a method for optimizing low-speed performance of a speed sensorless asynchronous motor control according to a preferred embodiment of the present invention is shown;

[0050] Figure 2 A schematic diagram showing the change in critical frequency when the stator resistance changes by 50% using the traditional method is shown;

[0051] Figure 3 A schematic diagram showing the change in critical frequency when the rotor resistance changes by 50% using the traditional method is shown;

[0052] Figure 4 A schematic diagram showing the change in critical frequency when the mutual inductance changes by 50% using the traditional method is shown;

[0053] Figure 5 A schematic diagram showing a critical frequency change when the stator resistance changes by 50% when g1=500 is set in a method for optimizing low-speed performance of a speed sensorless asynchronous motor control according to a preferred embodiment of the present invention is shown;

[0054] Figure 6 The figure shows the amplitude and angle errors of the feedback gain and the zero feedback gain in the low-speed performance optimization method for controlling a speed sensorless asynchronous motor under no-load and full-load conditions when the stator resistance mismatch is +50%.

[0055] Figure 7 The figure shows the amplitude and angle errors of the feedback gain and the zero feedback gain in the low-speed performance optimization method of the speed sensorless asynchronous motor control under no-load and full-load conditions when the stator resistance mismatch is -50%.

[0056] Figure 8FIG. 1 shows an observer pole diagram drawn when k=500 in a method for optimizing low-speed performance of a speed sensorless asynchronous motor control according to a preferred embodiment of the present invention;

[0057] Figure 9 1. The diagram shows the observer pole diagram when k1=500 in the method for optimizing low-speed performance of speed sensorless asynchronous motor control according to a preferred embodiment of the present invention;

[0058] Figure 10 The results of low-speed power generation operation with a stator resistance mismatch of 0% in Example 1 are shown;

[0059] Figure 11 The results of low-speed power generation operation with a stator resistance mismatch of -30% in Example 1 are shown;

[0060] Figure 12 The results of low-speed power generation operation with a stator resistance mismatch of +30% in Example 1 are shown;

[0061] Figure 13 The results of the extremely low-speed operation response after the stator resistance step change of +30% in Example 2 are shown;

[0062] Figure 14 The following figure shows the extremely low speed operation response results after the stator resistance step change of -30% in Example 2;

[0063] Figure 15 The results of low-speed power generation operation with a stator resistance mismatch of 0% in Comparative Example 1 are shown;

[0064] Figure 16 The results of low-speed power generation operation with a stator resistance mismatch of -30% in Comparative Example 1 are shown;

[0065] Figure 17 The results of low-speed power generation operation in Comparative Example 1 with a stator resistance mismatch of +30% are shown. DETAILED DESCRIPTION

[0066] The present invention will be described in further detail below with reference to the accompanying drawings and examples, through which the features and advantages of the present invention will become more clearly understood.

[0067] The word "exemplary" is used exclusively herein to mean "serving as an example, example, or illustration." Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. Although various aspects of the embodiments are shown in the drawings, the drawings are not necessarily drawn to scale unless otherwise indicated.

[0068] According to the present invention, a method for optimizing low-speed performance of a speed sensorless asynchronous motor control is provided. Figure 1 As shown, the following steps are included:

[0069] S1. Establish a motor model through the stator voltage, current and rotor flux of the asynchronous motor, and construct a full-order observer model composed of observation quantities based on the motor model;

[0070] S2. Obtain the unstable critical frequency of the full-order observer model based on the motor parameters, and obtain the constraint that satisfies the observed speed stability by shrinking the critical frequency to zero;

[0071] S3. Establishing a critical frequency expression under stator resistance mismatch conditions to obtain a first feedback gain constraint that can weaken the critical frequency shift phenomenon caused by stator resistance variation;

[0072] S4. Establishing a ratio function of the observed flux to the actual flux under the condition of stator resistance mismatch, and obtaining a second feedback gain constraint that minimizes the flux observation error;

[0073] S5. Determine the feedback gain coefficient in the full-order observer model by combining the first feedback gain constraint and the second feedback gain constraint to obtain a final full-order observer, and use the full-order observer to control the motor.

[0074] In S1, the motor model is expressed as:

[0075]

[0076] Among them, i s represents the stator current, ψ r represents the rotor flux, u s represents the stator voltage; p is the derivative symbol, a 11 、a 12 、a 21 、a 22 , b are coefficient parameters.

[0077] The stator current, rotor flux, and stator voltage are expressed as:

[0078] i s =i sd +ji sq

[0079] ψ r =ψ rd +jψ rq

[0080] u s =u sd +ju sq

[0081] Among them, i sd is the d-axis component of the stator current, i sq is the q-axis component of the stator current; ψ rdThe d-axis component of the rotor flux, ψ rq is the q-axis component of the rotor flux; u sd is the d-axis component of the stator voltage, u sq is the q-axis component of the stator voltage, and j is the imaginary unit.

[0082] Preferably, the coefficient parameters are set as:

[0083] a 11 =a1-jω e , a 12 =a2(1 / T r -jω r ),

[0084] a 21 =L m / T r , a 22 =-1 / T r -j(ω e -ω r ),

[0085] a1=-(R s / (σL s )+a2L m / T r ), a2=L m / (σL s L r ), b=1 / (σL s ),

[0086] T r =L r / R r

[0087] Among them, a1 and a2 are intermediate quantities, σ is the magnetic leakage coefficient, T r is the rotor time constant; ω e is the synchronous angular velocity, ω r is the rotor electrical angular velocity; R s is the stator resistance, R r is the rotor resistance; L s is the stator inductance, L r is the rotor inductance, L m It is mutual induction.

[0088] The full-order observer model is expressed as:

[0089]

[0090] K1=g1+jg2,K2=g3+jg4

[0091] in, represents the observed quantity of stator current, represents the observed quantity of the rotor flux, Represents the coefficient parameter a 12 The observed quantity, Represents the coefficient parameter a 22 K1 and K2 are intermediate variables, representing feedback gain, and g1, g2, g3, and g4 are feedback gain coefficients.

[0092] In S2, the unstable critical frequency is expressed as:

[0093] ω c =-(yω r +z / T r ) / x

[0094] x=-a1+g1+1 / T r , y=a1-g1-a2g3+a2L m / T r , z=g2+a2g4

[0095] Among them, ω c is the unstable critical frequency, and x, y, and z are all intermediate variables.

[0096] According to the present invention, the feedback gain is set by shrinking the critical frequency to zero, so that the unstable interval of the rotational speed observation is eliminated, thereby solving the problem of unstable low-speed power generation.

[0097] According to the present invention, the constraint of satisfying the stability of the observed speed is expressed as:

[0098]

[0099] The feedback gain is designed to make the above equation true to satisfy the stability of the observed speed. The first term in the above equation is easy to satisfy, so the key to eliminating the unstable area of ​​low-speed power generation lies in whether the second term in the above equation can be satisfied, that is, the critical frequency ω of the speed observation instability c Reduced to zero. Let ω c Zero gives:

[0100] (R s / (σL s )+g1+a2g3)ω r -(g2+a2g4) / T r =0

[0101] Theoretically, the critical frequency ω can be adjusted by designing the feedback gain. cHowever, this approach inevitably depends on the actual motor parameters, causing the observer to be sensitive to a certain motor parameter. This problem is widely present in the feedback gain design method based on the speed observation stability principle. When the parameters change, the unstable boundary must be offset. At this time, ω c It cannot shrink to zero as under ideal conditions.

[0102] In S3, the critical frequency expression under the stator resistance mismatch condition is:

[0103] ω c =ΔR s / (σL s ) / xω r

[0104] in, is the stator resistance error, Represents the stator resistance parameter used in the observer.

[0105] There is an inherent motor stator resistance parameter in the feedback gain constraint. In order to make the equation valid, the stator resistance parameter is inevitably used in the feedback gain to cancel out its inherent parameter, which causes the critical frequency offset problem caused by stator resistance mismatch, and because of ΔR s The reason why the unstable boundary deviates far from the zero plane is that it accounts for a relatively significant proportion in the formula. Figure 2-4 The critical frequency ω is shown when the motor parameters vary within 0.5 pu to 1.5 pu using the traditional method. c The offset result is Figure 2 The diagram shows the critical frequency change after the stator resistance changes by 50%. Figure 3 The diagram shows the critical frequency change after the rotor resistance changes by 50%. Figure 4 The diagram shows the critical frequency change after the mutual inductance changes by 50%. It can be seen that ω c It is not sensitive to the changes of rotor resistance and mutual inductance, and its value remains in the zero plane without obvious deviation, but under the condition of stator resistance mismatch, the critical frequency ω c The value of obviously deviates from the zero plane, resulting in the existence of unstable areas.

[0106] In the present invention, the robustness of the observer to the stator resistance is improved by solving the offset problem of the critical frequency, thus preventing the system from falling into an unstable operating state. Furthermore, based on the critical frequency expression, by increasing the intermediate variable x, ΔR is weakened to a certain extent. s The impact caused.

[0107] The first feedback gain constraint that can weaken the critical frequency shift phenomenon caused by stator resistance variation is expressed as:

[0108] g1>>R s / (σL s )

[0109] In the present invention, by setting the feedback gain constraint g1>>R s / (σL s ) can increase the intermediate variable x, thereby solving the problem of critical frequency offset. For example, set g1 = 500 and bring it into ω c , and assume that the other parameters are accurate. Now draw a diagram of the critical frequency change when the stator resistance changes by 50%. Figure 5 As shown, Figure 2 By comparison, it can be clearly seen that the critical frequency shift phenomenon caused by stator resistance mismatch has been effectively improved.

[0110] In S4, the ratio function of the observed flux and the actual flux of the motor when the stator resistance is mismatched is:

[0111]

[0112]

[0113] Among them, h1 and h2 are intermediate variables.

[0114] This ratio function is not only related to the motor parameters, but also to the feedback gain. When different feedback gains are used, the observer's sensitivity to the motor parameters is also different.

[0115] The second feedback gain constraint that minimizes the flux linkage observation error is expressed as:

[0116] g1>>R s / (σL s )

[0117] g3=g4=0

[0118] According to the value function expression, h1 and h2 are coefficient items containing the stator resistance term. By setting the feedback gain g3=g4=0, K2 can be set to zero, and then h1 is set to zero, thus eliminating the stator resistance error term. s / (σL s ) can make the real part of K1 much larger than a 11 The real part of h2 makes the result approximately equal to 1, so as to avoid the error of the observed flux amplitude and phase caused by the stator resistance mismatch.

[0119] In S5, by combining the first feedback gain constraint and the second feedback gain constraint, as well as the unstable critical frequency obtained in S2, g2 = T r (R s / (σL s)+g1)ω r , thus the feedback gain coefficient in the full-order observer model is obtained, which is expressed as:

[0120]

[0121] Among them, k is a configurable parameter.

[0122] Substituting the feedback gain coefficient into the full-order observer model, the final full-order observer can be obtained.

[0123] The full-order observer in the present invention can effectively reduce the flux observation error. Figure 6-Figure 7 The figure shows the amplitude and angle errors of flux linkage observed when the stator resistance changes by 50% under no-load and full-load conditions using zero feedback gain and the feedback gain of the present invention respectively. Figure 6 When the stator resistance mismatch is +50%, it can be seen from the figure that the feedback gain of the present invention reduces the angular error of flux observation from 20° to 1.8° under no-load conditions and from 6° to 1.6° under full-load conditions relative to zero feedback gain.

[0124] Figure 7 When the stator resistance mismatch is -50%, it can be seen from the figure that the feedback gain of the present invention is reduced from 11° to 1.9° under no-load conditions and from 3.5° to 1.4° under full-load conditions relative to zero feedback gain.

[0125] The inventors found that if g1 is simply selected as a constant, for example, k = 500, the observer pole diagram is drawn as follows: Figure 8 As shown in Figure 8, the speed is set to 0 to 5 Hz. As shown in Figure 8, the observer pole has extremely large real and imaginary parts, which is not conducive to the stability of the observer after digital processing. Therefore, it is only suitable for low-speed conditions.

[0126] Considering that the power generation instability problem and the sensitivity to stator resistance change are both manifested in the extremely low speed condition, and the excessive gain coefficients g1 and g2 after the speed increases lead to extremely large real and imaginary parts of the observer pole, in a preferred embodiment, the parameter k can be set to Right now

[0127] Among them, k1 is a configurable constant.

[0128] According to the preferred embodiment of the present invention, the values ​​of the gain coefficients g1 and g2 are appropriately reduced after the speed increases to expand the system operating range, thereby taking into account both low-speed and high-speed operating conditions and achieving automatic and smooth switching of the feedback gain as the speed increases.

[0129] Let k1 = 500, and the observer extreme diagram is drawn in this preferred embodiment as follows: Figure 9 As shown in the figure, it can be seen that both the real and imaginary parts of the observer pole are effectively suppressed.

[0130] It should be understood that the various forms of the processes shown above can be used to reorder, add, or delete steps. For example, the steps described in the present disclosure can be performed in parallel, sequentially, or in a different order, as long as the desired results of the technical solutions disclosed in the present disclosure can be achieved. This is not limited herein.

[0131] Example

[0132] Example 1

[0133] A low-speed performance optimization simulation of a speed sensorless asynchronous motor was conducted. The motor parameters used were: rated power 11 kW, rated voltage 380 V, rated current 23.6 A, rated frequency 50 Hz, rated speed 1460 r / min, and rated torque 70 N·m.

[0134] The experiment includes the following steps:

[0135] S1. Establish a motor model through the stator voltage, current and rotor flux of the asynchronous motor, and construct a full-order observer model composed of observation quantities based on the motor model;

[0136] S2. Obtain the unstable critical frequency of the full-order observer model based on the motor parameters, and obtain the constraint that satisfies the observed speed stability by shrinking the critical frequency to zero;

[0137] S3. Establishing a critical frequency expression under stator resistance mismatch conditions to obtain a first feedback gain constraint that can weaken the critical frequency shift phenomenon caused by stator resistance variation;

[0138] S4. Establishing a ratio function of the observed flux to the actual flux under the condition of stator resistance mismatch, and obtaining a second feedback gain constraint that minimizes the flux observation error;

[0139] S5. Determine the feedback gain coefficient in the full-order observer model by combining the first feedback gain constraint and the second feedback gain constraint to obtain a final full-order observer, and use the full-order observer to control the motor.

[0140] In S1, the motor model is expressed as:

[0141]

[0142] i s =i sd +ji sq

[0143] ψ r =ψ rd +jψrq

[0144] u s =u sd +ju sq

[0145] The coefficient parameters are set as:

[0146] a 11 =a1-jω e , a 12 =a2(1 / T r -jω r ),

[0147] a 21 =L m / T r , a 22 =-1 / T r -j(ω e -ω r ),

[0148] a1=-(R s / (σL s )+a2L m / T r ), a2=L m / (σL s L r ), b=1 / (σL s ),

[0149] T r =L r / R r .

[0150] The full-order observer model is expressed as:

[0151]

[0152] K1=g1+jg2,K2=g3+jg4。

[0153] In S2, the unstable critical frequency is expressed as:

[0154] ω c =-(yω r +z / T r ) / x

[0155] x=-a1+g1+1 / T r , y=a1-g1-a2g3+a2L m / T r , z=g2+a2g4.

[0156] The constraint satisfying the stability of the observed speed is expressed as:

[0157]

[0158] In S3, the critical frequency expression under the stator resistance mismatch condition is:

[0159] ω c =ΔR s / (σL s ) / xω r

[0160] The first feedback gain constraint that can weaken the critical frequency shift phenomenon caused by stator resistance variation is expressed as:

[0161] g1>>R s / (σL s )

[0162] In S4, the ratio function of the observed flux and the actual flux of the motor when the stator resistance is mismatched is:

[0163]

[0164]

[0165] The second feedback gain constraint that minimizes the flux linkage observation error is expressed as:

[0166] g1>>R s / (σL s )

[0167] g3=g4=0

[0168] In S5, the feedback gain coefficient in the full-order observer model is expressed as:

[0169]

[0170] The motor is tested for forward and reverse rotation at an initial speed of 150 r / min under 50% rated load conditions. A reverse command is given in the 5th second. The results are as follows: Figure 10-12 As shown, Figure 10 The results of low-speed power generation operation with a stator resistance mismatch of 0% are shown. The maximum absolute error between the observed speed and the actual speed is 9 r / min. Figure 11 The results of low-speed power generation operation with a stator resistance mismatch of -30% are shown. The maximum absolute error between the observed speed and the actual speed is 11r / min. Figure 12 The results of low-speed power generation operation with a stator resistance mismatch of +30% are shown. The maximum absolute error between the observed speed and the actual speed is 12r / min. Figure 10-12It can be seen from the figure that this method can achieve stable power generation operation under the condition of stator resistance mismatch.

[0171] Example 2

[0172] The same experiment as in Example 1 was conducted, except that the initial speed was set to 45 r / min and the stator resistance was changed in a stepwise manner while the motor was running steadily. Figure 13-14 As shown. Figure 13 The following figure shows the extremely low speed operation response after a stator resistance step change of +30%. Figure 14 The figure shows the extremely low speed operation response results after a stator resistance step change of -30%.

[0173] from Figure 13-14 It can be seen from the figure that the observed speed quickly follows the command value under the action of the speed loop PI regulator and can still operate stably under extremely low speed stator resistance mismatch conditions.

[0174] Comparative Example 1

[0175] The same experiment as in Example 1 was carried out, except that the full-order observer adopted zero feedback gain. The simulation results are shown in Figure 15-17 shown.

[0176] in, Figure 15 The results of low-speed power generation operation with a stator resistance mismatch of 0% are shown. There is still an unstable area during braking, and the maximum absolute error between the observed speed and the actual speed is 32r / min. Figure 16 The results of low-speed power generation operation with a stator resistance mismatch of -30% are shown. The unstable area expands and shows an unstable trend throughout the braking process. When the speed approaches zero, it is completely out of control. Figure 17 The results of low-speed power generation operation with a stator resistance mismatch of +30% are shown. Although the observed speed has not completely lost control, there is still a large unstable area. The maximum absolute error between the observed speed and the actual speed is 151r / min.

[0177] Comparing the results of Example 1 with those of Comparative Example 1, Figure 10 and Figure 15 , Figure 11 and Figure 16 , Figure 12 and Figure 17 As can be seen from the figure, the method in Example 1 effectively improves the system stability when facing the stator resistance mismatch problem under extremely low speed conditions.

[0178] The present invention has been described above with reference to preferred embodiments, but these embodiments are merely exemplary and serve only as illustrations. On this basis, various replacements and improvements can be made to the present invention, all of which fall within the scope of protection of the present invention.

Claims

1. A method for optimizing low-speed performance of speed sensorless asynchronous motor control, characterized in that: The following steps are involved: S1. Establish a motor model through the stator voltage, current and rotor flux of the asynchronous motor, and construct a full-order observer model composed of observation quantities based on the motor model; S2. Obtain the unstable critical frequency of the full-order observer model based on the motor parameters, and obtain the constraint that satisfies the observed speed stability by shrinking the critical frequency to zero; S3. Establishing a critical frequency expression under stator resistance mismatch conditions to obtain a first feedback gain constraint that can weaken the critical frequency shift phenomenon caused by stator resistance variation; S4. Establishing a ratio function of the observed flux to the actual flux under the condition of stator resistance mismatch, and obtaining a second feedback gain constraint that minimizes the flux observation error; S5. Determine the feedback gain coefficient in the full-order observer model by combining the first feedback gain constraint and the second feedback gain constraint to obtain a final full-order observer, and use the full-order observer to control the motor; In S1, the full-order observer model is expressed as: K1=g1+jg2,K2=g3+jg4 Among them, i s represents the stator current, ψ r represents the rotor flux, u s represents the stator voltage, p is the derivative symbol, a 11 、a 12 、a 21 、a 22 , b are coefficient parameters, represents the observed quantity of the stator current, represents the observed quantity of the rotor flux, Represents the coefficient parameter a 12 The observed quantity, Represents the coefficient parameter a 22 The observed quantity, K1 and K2 are intermediate variables, g1, g2, g3, g4 are feedback gain coefficients, to 11 =a1-jω e ,to 12 =a2(1 / T r -jω r ), a 21 =L m / T r ,a 22 =-1 / T r -j(ω e -ω r ), a1=-(R s / (σL s )+a2L m / T r ),a2,L m x / (σL s L r ),b=1 / (σL s ), Among them, a1 and a2 are intermediate quantities, σ is the magnetic leakage coefficient, T r is the rotor time constant; ω e is the synchronous angular velocity, ω r is the rotor electrical angular velocity; R s is the stator resistance, R r is the rotor resistance; L s is the stator inductance, L r is the rotor inductance, L m It is mutual induction; In S2, the unstable critical frequency is expressed as: ω c =-(yω r +z / T r ) / x x=-a1+g1+1 / T r ,y=a1-g1-a2g3+a2L m / T r ,z=g2+a2g4 Among them, ω c is the unstable critical frequency, x, y, and z are all intermediate variables; The constraint of satisfying the stability of the observed speed is expressed as: In S3, the first feedback gain constraint that can weaken the critical frequency shift phenomenon caused by the stator resistance change is expressed as: g1>>R s / (σL s ) In S4, the second feedback gain constraint that minimizes the flux linkage observation error is expressed as: g1>>R s / (σL s ) g3=g4=0 In S5, by combining the first feedback gain constraint and the second feedback gain constraint, as well as the unstable critical frequency obtained in S2, g2 = T r (R s / (σL s )+g1)ω r , thus the feedback gain coefficient in the full-order observer model is obtained, which is expressed as: Among them, k is a configurable parameter.

2. The method for optimizing low-speed performance of a speed sensorless asynchronous motor control according to claim 1, characterized in that: In S1, the motor model is expressed as: The stator current, rotor flux, and stator voltage are expressed as: i s =to sd +ji sq ψ r =ψ rd +jψ rq you s =u sd +you sq Among them, i sd is the d-axis component of the stator current, i sq is the q-axis component of the stator current; ψ rd The d-axis component of the rotor flux, ψ rq is the q-axis component of the rotor flux; u sd is the d-axis component of the stator voltage, u sq is the q-axis component of the stator voltage, and j is the imaginary unit.

3. The method for optimizing low-speed performance of a speed sensorless asynchronous motor control according to claim 1, characterized in that: In S3, the critical frequency expression under the stator resistance mismatch condition is: oh c =ΔR s / (σL s ) / xω r in, is the stator resistance error, Represents the stator resistance parameter used in the observer.

4. The method for optimizing low-speed performance of a speed sensorless asynchronous motor control according to claim 1, characterized in that: The parameter k can be set to Among them, k1 is a configurable constant.

Images