A current zero-gradient position correction method for a switched reluctance motor based on single-pulse injection

Abstract

The application relates to a single-pulse injection-based switch reluctance motor current zero-gradient position correction method and a working condition monitoring method using the same. During high-speed operation of the switch reluctance motor, the current zero-gradient position is detected by a current gradient method, a single-pulse signal is injected into an idle phase, the phase inductance value corresponding to the current rotor position is calculated according to the current change rate of the single-pulse current rising section and the single-pulse current falling section, the rotor angular position corresponding to the single-pulse injection moment is obtained by reverse inquiry, the actual current zero-gradient position is calculated, and online correction is completed. The online correction of the current zero-gradient position is realized, the estimation error problem caused by regarding the current zero-gradient position as a fixed position in the traditional current gradient method is overcome, the rotor position estimation precision, the universality and the engineering transplantability in the high-speed operation region are improved, and the system operation efficiency is improved.

Description

Technical Field

[0001] This invention belongs to the field of switched reluctance motor control, and relates to a method for zero-gradient position correction of switched reluctance motor current based on single-pulse injection, as well as a method for monitoring operating conditions using the zero-gradient position correction method. Background Technology

[0002] Switched reluctance motors (SRMs) possess advantages such as simple and robust structure, strong overload capacity, and wide operating range, making them promising candidates for applications in aerospace, electric vehicles, and home appliances. However, due to their doubly salient pole structure, the electromagnetic characteristics of SRMs are highly nonlinear. Traditional control schemes heavily rely on rotor position information, typically obtained through position sensors such as photoelectric encoders or rotary transformers. However, rotor position sensors not only increase system size and cost but also reduce system reliability. Therefore, sensorless control technology for SRMs has become a research hotspot in both academia and industry.

[0003] Sensorless control methods for switched reluctance motors are mainly divided into two categories: low-speed and high-speed. In the low-speed domain, a widely used method is to inject high-frequency pulses into the idle phase and estimate the rotor position by extracting information such as the pulse's peak current, current slope or current slope difference, inductance, and flux linkage. However, the high-frequency pulse injection method is limited by the frequency of the injected pulses and is difficult to extend to high-speed operating conditions. In the high-speed domain, the motor operates in a single-pulse excitation mode, and the current waveform is relatively simple. Existing high-speed sensorless control methods mainly include methods based on online flux linkage integration, observer-based methods, and feature position detection-based methods. Among these, the current gradient method, which estimates the rotor position by detecting the current zero-gradient position (CZGP), is one of the simplest and most effective methods for achieving high-speed sensorless control.

[0004] However, the traditional current gradient method has the following shortcomings: CZGP is affected by operating conditions (such as turn-on angle, speed, load torque, bus voltage, etc.), and deviations will occur under different operating conditions, leading to a decrease in rotor position estimation accuracy. In the prior art, although CZGP deviations can be compensated by pre-stored lookup tables (LUTs), this method requires a large amount of prediction or simulation work to build the lookup table, and it depends on motor parameters, resulting in poor versatility and portability. In addition, existing methods do not reveal the root cause of CZGP deviations, nor do they propose effective online correction schemes. Summary of the Invention

[0005] Technical problems to be solved To overcome the shortcomings of existing technologies, this invention proposes a method for zero-gradient current position correction of switched reluctance motors based on single-pulse injection. This method is a high-speed sensorless current gradient correction method for switched reluctance motors based on dynamic single-pulse injection and its operating condition monitoring method, thus solving the deficiencies of existing technologies.

[0006] Technical solution A method for zero-gradient position correction of a switched reluctance motor based on single-pulse injection, characterized by the following steps: Step 1: Establishing a non-saturated switching reluctance motor and inductance and rotor angle Location Correspondence Table L- And stored in the controller; Among them, the unsaturated inductor This indicates the inductance value of the phase winding when a small-amplitude detection pulse is injected and the phase current is small; the rotor angular position... Indicates the relationship with the unsaturated inductance The corresponding rotor position angle; Step 2: During the operation of the switched reluctance motor, detect the current waveform of each phase, detect the zero gradient position of the current using the current gradient method, and assign a timestamp t2 to the zero gradient position of the current. The zero gradient position of the current is defined as the position in the phase current waveform where the rate of change of the current is zero. Step 3: During the operation of the switched reluctance motor, inject a single pulse signal into the idle phase and give a timestamp t1 corresponding to the peak value of the single pulse current; The idle phase refers to the phase winding that is in the non-working range and is not connected to the excitation current; Step 4: Based on the rate of change of the current during the rising and falling phases of the single-pulse current, calculate the phase inductance value corresponding to the current rotor position using the current slope difference method. ; Step 5: Based on the actual calculated phase inductance value The relation table L- established in step 1 In the middle, the phase inductance value As a relation table L- The non-saturated inductance in the middle is compared with the phase inductance value. Corresponding rotor angle position ; Step 6: Based on the time interval between the peak current position of the single pulse at time t1 and the zero gradient current position at time t2... and current speed The angle difference between the single-pulse injection position and the current zero gradient position is obtained. Based on the angle difference The calculated position of the zero gradient of the current in the actual online correction is obtained. ;

[0007] in, This represents the actual time difference between the peak current time t1 and the current zero gradient position time t2 of a single pulse current; This represents the current mechanical angular velocity of the rotor. Indicates in The difference in mechanical angles traversed by the rotor during the time interval; This represents the actual rotor mechanical angle corresponding to the zero-gradient position of the current after single-pulse injection correction.

[0008] When establishing the correspondence table between the unsaturated inductance of the switched reluctance motor and the rotor angular position, a position sensor is connected to the motor shaft to make the rotor rotate at low speed. At the same time, high-frequency pulses are continuously injected into any phase winding of the motor until a complete mechanical cycle is covered. For each injected high-frequency pulse, the unsaturated inductance value is calculated using the current slope difference method, and it corresponds one-to-one with the rotor angular position measured by the sensor at this time to obtain the lookup table of the correspondence between the unsaturated inductance and the rotor angular position.

[0009] The high-frequency pulse is determined based on the low-speed rotation of the rotor during calibration, the required angular resolution of the lookup table, and the current sampling accuracy, ensuring a sufficient number of pulse sampling points within a complete mechanical cycle. Simultaneously, the frequency should also ensure that each pulse has a measurable current change during both the rising and falling phases, so that the inductance can be calculated using the current slope difference method.

[0010] The method for detecting zero current change rate using the current gradient method: Since the position where the current change rate is zero under high-speed operation is the current peak position; the position where the current change rate is zero is located directly by capturing the moment when the current peak value is located in each cycle.

[0011] The phase inductance value corresponding to the current rotor position is calculated using the current slope difference method. :

[0012] in: This is the DC bus voltage. The rate of change of current at the falling edge of the injected single pulse; The rate of change of current on the rising edge of the injected single pulse.

[0013] A method for monitoring operating conditions using the aforementioned single-pulse injection-based zero-gradient position correction method for switched reluctance motors, characterized in that: The expression for determining the status of the operating condition monitoring system is:

[0014]

[0015]

[0016] The operating condition monitoring process is as follows: in, This is a current status indicator. This is a speed status indicator. This is a system status flag; 1 indicates a static state, and 0 indicates a dynamic state. This is the peak current of the previous cycle. This is the peak current of the current cycle. The rotational speed of the previous cycle. The rotational speed for the current cycle. This refers to the permissible current limit. This refers to the permissible speed limit; Based on the changes in peak current and rotational speed detected in adjacent cycles, the corresponding current status flags are determined respectively. Speed ​​status flag The current operating status is determined based on the aforementioned status flags: 1) When the peak current change is less than or equal to the set threshold (current allowable limit) and the speed change is less than or equal to the set threshold (speed allowable limit), it is determined to be a non-changing state, i.e., the motor is in steady-state operation. Step 3 (single pulse injection) is stopped until step 6, and online correction of the current zero gradient position is stopped. ; 2) When the peak current change exceeds the set threshold (current tolerance limit) or the speed change exceeds the set threshold (speed tolerance limit), it is determined to be a changing state, i.e., the motor is in dynamic operating condition. The single-pulse injection in step 3 is executed until step 6, implementing online correction of the current zero gradient position. .

[0017] First, the motor is placed under multiple different "torque-speed" steady-state operating conditions, and current samples are continuously collected at multiple current zero gradient positions under each operating condition. Then, the maximum fluctuation extreme value of the current is extracted within the entire operating condition range, and a set safety margin is assigned based on the maximum natural fluctuation extreme value as the allowable limit value of current variation.

[0018] First, the motor is placed under multiple different "torque-speed" steady-state operating conditions, and speed samples are continuously collected at multiple current zero gradient positions under each operating condition. Then, the maximum fluctuation extreme value of the speed is extracted within the entire operating condition range, and a set safety margin is assigned based on the maximum natural fluctuation extreme value as the allowable limit value of speed variation.

[0019] An electronic device, characterized in that it includes a processor and a memory, the processor being configured to execute a computer program stored in the memory to implement the steps of the operating condition monitoring method described above.

[0020] A computer program product, characterized in that it includes computer-executable instructions, which, when executed, are used to implement the method of monitoring the operating conditions.

[0021] Beneficial effects This invention proposes a method for zero-gradient current position correction of a switched reluctance motor based on single-pulse injection. During high-speed operation of the switched reluctance motor, the current waveforms of each phase are detected, and the zero-gradient current position is detected using the current gradient method, recording the corresponding timestamps. A single-pulse signal is injected into an idle phase, and the corresponding time of the single pulse is recorded. Based on the rate of change of the current during the rising and falling segments of the single-pulse current, the phase inductance value corresponding to the current rotor position is calculated using the current slope difference method. The rotor angle position corresponding to the single-pulse injection time is obtained by reverse lookup using a non-saturated inductance lookup table. Based on the time interval between the single-pulse injection time and the zero-gradient current position time, and the current rotational speed, the actual zero-gradient current position is calculated, and online correction is completed.

[0022] The current gradient correction method for high-speed sensorless switched reluctance motors based on dynamic single-pulse injection of the present invention has the following advantages compared with the prior art: 1. This invention identifies unsaturated inductors online by injecting single pulses into the idle phase and combining them with the current slope difference method. It then uses a pre-established lookup table of unsaturated inductors and rotor position characteristics to look up the actual rotor position, thereby achieving online correction of the zero-gradient current position. This overcomes the estimation error caused by the traditional current gradient method treating the zero-gradient current position as a fixed position and improves the rotor position estimation accuracy in high-speed operating areas. 2. Compared with existing methods that rely on a large number of offline experiments or finite element simulations to establish multidimensional compensation lookup tables, this invention only needs to establish a set of unsaturated inductance-rotor position characteristic lookup tables to achieve online correction, which improves the versatility and engineering portability of the algorithm. 3. This invention introduces a working condition monitoring algorithm, which determines whether the system is in a steady-state or transient state by monitoring the changes in peak current and speed in real time. Single-pulse injection correction is only performed when the working condition changes, while pulse injection is stopped during steady-state operation, thereby reducing the number of switching device actions and additional losses, and improving system operating efficiency. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the zero current gradient position at high speed in this invention; Figure 2This is a schematic diagram of the full-cycle unsaturated inductor-rotor position characteristics measured offline by high-frequency pulse injection in this invention. Figure 3 This is a schematic diagram of the online position correction of zero current gradient based on single-pulse injection proposed in this invention; Figure 4 This is a schematic diagram illustrating the relationship between single-pulse injection and operating conditions in the dynamic single-pulse injection scheme proposed in this invention. Figure 5 This is a flowchart of the working condition monitoring algorithm proposed in this invention; Figure 6 This is an experimental waveform diagram of the present invention operating in steady state according to an embodiment; Figure 7 This is an experimental waveform diagram of the present invention operating under varying rotational speed conditions. Detailed Implementation

[0024] The present invention will now be further described in conjunction with the embodiments and accompanying drawings: This invention provides a high-speed sensorless current gradient correction method for switched reluctance motors based on dynamic single-pulse injection. To make the objectives, technical solutions, and advantages of this invention clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of the invention.

[0025] See the embodiments of the present invention. Figures 1 to 7 This embodiment provides a method for high-speed sensorless current gradient correction of switched reluctance motors based on dynamic single-pulse injection, including the following steps: S1. Establish a lookup table for the correspondence between the unsaturated inductance of the switched reluctance motor and the rotor angle position, and store it in the controller; S2. During the high-speed operation of the switched reluctance motor, detect the current waveform of each phase, detect the zero gradient position of the current by the current gradient method, and record the corresponding timestamp. S3. During the operation of the switched reluctance motor, inject a single pulse signal into the idle phase and record the time corresponding to the single pulse; S4. Based on the rate of change of the current during the rising and falling phases of the single pulse current, the phase inductance value corresponding to the current rotor position is calculated using the current slope difference method. S5. Based on the unsaturated inductance lookup table established in step S1, reverse the lookup to obtain the rotor angle position corresponding to the single pulse injection moment. S6. Calculate the actual current zero gradient position and complete online correction based on the time interval between the single pulse injection time and the current zero gradient position time and the current rotation speed.

[0026] The method for establishing the lookup table corresponding to the unsaturated inductance and the rotor angular position is as follows: A position sensor is connected to the motor shaft to make the rotor rotate at low speed. At the same time, high-frequency pulses are continuously injected into any phase winding of the motor until a complete mechanical cycle is covered. Because there are many high-frequency pulses in a mechanical cycle, the resulting inductance curve is very smooth. For each injected high-frequency pulse, the unsaturated inductance value is calculated using the current slope difference method, and then matched one-to-one with the rotor angle position measured by the sensor at that time, resulting in a lookup table of the correspondence between unsaturated inductance and rotor angle position. For example... Figure 2 As shown.

[0027] The obtained complete mechanical cycle unsaturated inductor characteristic curve is stored in the microprocessor in the form of a lookup table.

[0028] The principle of zero gradient position detection is as follows: Figure 3 As shown.

[0029] For each phase winding of the switched reluctance motor, Faraday's law is satisfied:

[0030]

[0031] in, Phase voltage, For phase current, For phase resistance, For phase inductance, For rotational speed, Rotor position; The first term on the right side of the equation is the voltage drop across the resistor, the second term is the back electromotive force of the transformer, and the third term is the moving back electromotive force, which is related to the slope of the inductance. Proportional. Before the stator and rotor begin to overlap, The phase voltage is approximately zero, the back electromotive force is negligible, and the phase voltage is mainly used for current excitation, resulting in a rapid increase in current. However, once the stator and rotor begin to overlap, the back electromotive force increases rapidly from zero, especially at high speeds due to the increased rotational speed. The large back electromotive force causes the back electromotive force to exceed the phase voltage, the transformer back electromotive force becomes negative, and the current begins to decrease after overlapping. Therefore, the current shows a waveform of first rising and then falling. There must be a position where the current gradient is zero, that is, the current zero gradient position.

[0032] The existence of CZGP at the stator-rotor overlap position is proven through analytical derivation. The derivation process is as follows: Let the overlapping position be , For the minute displacement of the rotor position, and Substitute each into the expression for Faraday's law; Since the displacement is extremely small, the inductance and phase current at the two locations can be considered the same, and the phase voltage remains constant. exist Since the first zero, we can obtain:

[0033] This formula shows that the current gradient before the overlapping position is always greater than the current gradient after the overlapping position. Therefore, the zero current gradient position appears at the stator-rotor overlapping position, which is also the peak current position.

[0034] Therefore, during high-speed operation, the moving back electromotive force increases rapidly with increasing speed. When the moving back electromotive force exceeds the phase voltage, the phase current changes from an upward state to a downward state. Thus, the phase current waveform must have a position where the rate of change of current is zero; this position is defined as the zero-gradient current position. The corresponding position can be obtained by calculating the rate of change of phase current in real time.

[0035] Specifically, the single-pulse injection process is as follows: Figure 4 As shown, during the normal output torque period of the currently conducting phase, a single-pulse signal with a small amplitude and short duration is injected into the idle phase. Since the injected current is much smaller than the excitation current, it will not have a significant impact on the motor's average torque and operating efficiency.

[0036] The unsaturated inductance value is calculated using the current slope difference method. For the rising and falling phases of the injected single pulse current, the voltage equations are as follows:

[0037]

[0038] in, and Let be the forward voltage drops of the power switch and the diode, respectively. Ignoring the effects of the voltage drops of the switch and the diode, subtracting the two equations yields the expression for calculating the phase inductance during the pulse:

[0039] The current slope during the rising phase and the current slope during the falling phase of a single pulse are detected separately, and then:

[0040] This current slope difference method is insensitive to resistance voltage drop and motion back EMF, and can accurately identify unsaturated inductors under high-speed operating conditions. This method effectively eliminates the influence of resistance voltage drop and motion back EMF on the inductance identification results, and is therefore suitable for high-speed operating conditions.

[0041] The rotor angle position corresponding to the single pulse injection position is looked up in a lookup table based on the calculated unsaturated inductance value. ; Secondly, combining the single-pulse injection timing With the current zero gradient position time The time interval between ,in, For single-pulse injection time, The position is the zero gradient position of the current.

[0042] The expression for the angle difference between the single-pulse injection position and the current zero gradient position is:

[0043] Where: current mechanical angular velocity ; Finally, the online correction formula for obtaining the actual value of the current zero gradient position is obtained, which is the actual current zero gradient position:

[0044] in, This is the corrected position of the zero gradient of the current. The rotor position corresponding to the single pulse injection position is obtained by reverse lookup of the unsaturated inductance-rotor position characteristic lookup table; This enables online correction of the current zero gradient position.

[0045] The system is determined to be in steady state or transient state based on the operating condition monitoring algorithm. When the system is in transient state, a single pulse is injected in each control cycle to correct the current zero gradient position. When the system enters steady state, the single pulse injection is stopped, and only the traditional current gradient method is used for rotor position estimation.

[0046] Specifically, the working condition monitoring algorithm process is as follows: Figure 5 As shown, the controller compares the peak current change and speed change between adjacent control cycles in real time. When both are less than a preset threshold, the system is determined to be in steady-state operation, and single-pulse injection is stopped; when either parameter exceeds the threshold, the system is determined to be in dynamic operation, and the single-pulse injection and online correction process is restarted.

[0047] The expression for determining the system state is:

[0048]

[0049]

[0050] The operating condition monitoring process is as follows: in, This is a current status indicator. This is a speed status indicator. This is a system status flag; 1 indicates a static state, and 0 indicates a dynamic state. This represents the peak current of the previous cycle. This is the peak current of the current cycle. The rotational speed of the previous cycle. The rotational speed for the current cycle. This refers to the permissible current limit. This refers to the permissible speed limit; Based on the changes in peak current and rotational speed detected in adjacent cycles, the corresponding current status flags are determined respectively. Speed ​​status flag The current operating status is determined based on the aforementioned status flags: 1) When the peak current change is less than or equal to the set threshold (current allowable limit) and the speed change is less than or equal to the set threshold (speed allowable limit), it is determined to be a non-changing state, i.e., the motor is in steady-state operation. Step 3 (single pulse injection) is stopped until step 6, and online correction of the current zero gradient position is stopped. ; 2) When the peak current change exceeds the set threshold (current tolerance limit) or the speed change exceeds the set threshold (speed tolerance limit), it is determined to be a changing state, i.e., the motor is in dynamic operating condition. The single-pulse injection in step 3 is executed until step 6, implementing online correction of the current zero gradient position. ; The determination of the permissible current variation limit is based on statistical data analysis. First, the motor is operated under multiple different torque-speed steady-state conditions, and current samples are continuously collected at multiple current zero-gradient locations under each condition. Next, the maximum current fluctuation extreme value across the entire operating range is extracted; for example, the maximum current fluctuation under high-speed steady-state conditions was found to reach 2.5A during testing. Finally, to allow for false judgments, a safety margin is assigned based on the maximum natural fluctuation extreme value, and the final calculated and set permissible current variation limit value is 3A.

[0051] The determination of the permissible speed variation limit is based on statistical data analysis. First, the motor is operated under multiple different torque-speed steady-state conditions, and speed samples are continuously collected at multiple current zero-gradient positions under each condition. Next, the maximum speed fluctuation extreme value across the entire operating range is extracted; for example, the maximum speed fluctuation under high-speed steady-state conditions was found to reach approximately 40 rpm during testing. Finally, to allow for false judgments, a set safety margin is applied based on the maximum natural fluctuation extreme value, ultimately calculating and setting the permissible speed variation limit to 50 rpm.

[0052] In actual working conditions, this situation occurs. 1. Differences in physical inertia ( , Current is an electrical quantity with an extremely fast response time; while rotational speed is a mechanical quantity, affected by the rotor's moment of inertia, and its response is relatively lagging. When the motor suddenly encounters a sudden change in load torque, the controller will instantly and drastically adjust the current, causing the peak current in adjacent cycles to change drastically, exceeding the limit (i.e., ...). However, in this extremely brief instant, the rotational speed may be maintained by inertia, and the change is very small, not exceeding the limit (i.e., ).

[0053] 2. Sampling jitter or local interference ( , In actual data acquisition, environmental interference may cause a brief fluctuation in the speed encoder or speed measurement algorithm during a certain cycle, exceeding the limit (i.e., ), while at this time the phase current remains stable (i.e. ).

[0054] If either the current or the rotational speed changes beyond the tolerance limit, the system should consider the operating condition to have changed (entering a transient state) and thus re-inject pulses to correct the CZGP using the method of this application.

[0055] The following is a prototype using a three-phase 12 / 8 structure switched reluctance motor, with a stator pole arc of 15°, a rotor pole arc of 17°, an overlap of 6.5°, a rated speed of 3000 rpm, and a rated load of 6 Nm.

[0056] First, an offline lookup table is established to map the relationship between unsaturated inductance and rotor angular position. For example... Figure 2 As shown, high-frequency pulses are continuously injected into one phase winding by manually rotating the rotor at extremely low speed until a complete mechanical cycle (45° mechanical angle) is covered. For each injected high-frequency pulse, the slope of its current rise segment is sampled. and the slope of the current drop segment The formula for the difference in current slope is used:

[0057] The corresponding unsaturated inductance value is calculated. Due to the high injection frequency, a large number of pulses are contained within one mechanical cycle, resulting in a very smooth inductance curve. The obtained unsaturated inductance characteristic curve for the complete mechanical cycle is stored in the microprocessor in the form of a lookup table for subsequent online calibration to look up the rotor position.

[0058] During high-speed operation of the switched reluctance motor, the motor operates in single-pulse excitation mode, and the current waveform is as follows: Figure 1 As shown. Since the current exhibits a characteristic of first rising and then falling at high speeds, the position where the current gradient is zero can be detected by the current gradient method, and the corresponding timestamp t2 can be recorded.

[0059] Secondly, to address the issue of deviations in the zero-gradient current position caused by operating conditions, a single pulse is injected into the idle phase for online correction. For example... Figure 3 As shown, a single pulse is injected into the idle phase, and the time corresponding to the peak current of the single pulse is recorded as t1. The unsaturated inductance value corresponding to the current rotor position is calculated according to the current slope difference formula.

[0060] Since the amplitude of the injected pulse current is much smaller than the peak excitation current (which is typically in the range of 30A to 80A at high speeds), magnetic saturation is negligible and will not introduce significant errors. Based on the offline-stored unsaturated inductor-rotor position characteristic lookup table from step S1, the rotor angular position corresponding to the moment of single-pulse injection is obtained by reverse lookup from the calculated inductance value. According to the formula Calculate the time interval between the single-pulse injection time t1 and the current zero gradient position time t2, and then combine it with the current rotational speed. According to the formula Calculate the angle difference, and finally use the formula. Online correction of the actual CZGP value was completed. Simulation results show that the negative torque generated by single-pulse injection is only -0.01 Nm, which is equivalent to 0.74‰ of the rated load torque of 13.5 Nm, and the negative impact on torque and efficiency is negligible.

[0061] Finally, to further reduce unnecessary pulse injections, this invention designs as follows: Figure 5 The operating condition monitoring algorithm shown implements dynamic single-pulse injection.

[0062] like Figure 4 As shown, under steady-state conditions, the control parameters and operating conditions of adjacent control cycles are basically the same, and the current zero gradient position remains almost unchanged. Therefore, single-pulse injection is stopped, and the rotor position is estimated using the traditional current gradient method only when the operating condition monitoring algorithm determines that the operating condition has changed and entered a transient state. Only when the operating condition monitoring algorithm determines that the operating condition has changed and entered a transient state is a single pulse re-injected for online correction.

[0063] Figure 6 The figure shows the experimental results of the proposed high-speed sensorless current gradient correction method for switched reluctance motors under steady-state conditions with a rated load of 6 Nm and a rated speed of 3000 rpm. As can be seen from the figure, after online correction of the zero-gradient current position, the current waveforms in each cycle are basically consistent, the zero-gradient current position remains almost unchanged, and there is no pulse injection in the current waveform. The maximum error in rotor position estimation is less than 0.5°, verifying the high accuracy of the proposed method under steady-state conditions.

[0064] Figure 7The figure shows the experimental results of the proposed high-speed sensorless current gradient correction method for switched reluctance motors under variable speed conditions. The motor was operating at a rated load of 6 Nm, with the speed command increasing from 2000 rpm to 3000 rpm in a step. Before the speed step, the system was in a steady state with no pulse injection. After the speed step, the zero-gradient current position changed with the peak current and speed. A single pulse was injected into the idle phase for online correction of the zero-gradient current position, and the maximum rotor position estimation error was 1.3°. When the speed stabilized, the system returned to a steady state, pulse injection stopped, and the maximum error recovered to approximately 0.5°. The experimental results show that the method of this invention can maintain good rotor position estimation accuracy under variable speed transient conditions.

[0065] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus.

[0066] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for zero-gradient position correction of a switched reluctance motor based on single-pulse injection, characterized in that... The steps are as follows: Step 1: Establishing a non-saturated switching reluctance motor and inductance and rotor angle Location Correspondence Table L- And stored in the controller; Among them, the unsaturated inductor This indicates the inductance value of the phase winding when a small-amplitude detection pulse is injected and the phase current is small; the rotor angular position... Indicates the relationship with the unsaturated inductance The corresponding rotor position angle; Step 2: During the operation of the switched reluctance motor, detect the current waveform of each phase, detect the zero gradient position of the current using the current gradient method, and assign a timestamp t2 to the zero gradient position of the current. The zero gradient position of the current is defined as the position in the phase current waveform where the rate of change of the current is zero. Step 3: During the operation of the switched reluctance motor, inject a single pulse signal into the idle phase and give it a timestamp t1 corresponding to the peak value of the single pulse current; The idle phase refers to the phase winding that is in the non-working range and is not connected to the excitation current; Step 4: Based on the rate of change of the current during the rising and falling phases of the single-pulse current, calculate the phase inductance value corresponding to the current rotor position using the current slope difference method. ; Step 5: Based on the actual calculated phase inductance value The relation table L- established in step 1 In the middle, the phase inductance value As a relation table L- The non-saturated inductance in the middle is compared with the phase inductance value. Corresponding rotor angle position ; Step 6: Based on the time interval between the peak current position of the single pulse at time t1 and the zero gradient current position at time t2... and current speed The angle difference between the single-pulse injection position and the current zero gradient position is obtained. Based on the angle difference The calculated position of the zero gradient of the actual online correction current is obtained. ; in, This represents the actual time difference between the peak current time t1 and the current zero gradient position time t2 of a single pulse current; This represents the current mechanical angular velocity of the rotor. Indicates in The difference in mechanical angles traversed by the rotor during the time interval; This represents the actual rotor mechanical angle corresponding to the zero-gradient position of the current after single-pulse injection correction.

2. The method for zero-gradient position correction of switched reluctance motor current based on single-pulse injection according to claim 1, characterized in that: When establishing the correspondence table between the unsaturated inductance of the switched reluctance motor and the rotor angular position, a position sensor is connected to the motor shaft to make the rotor rotate at low speed. At the same time, high-frequency pulses are continuously injected into any phase winding of the motor until a complete mechanical cycle is covered. For each injected high-frequency pulse, the unsaturated inductance value is calculated using the current slope difference method, and it corresponds one-to-one with the rotor angular position measured by the sensor at this time to obtain the lookup table of the correspondence between the unsaturated inductance and the rotor angular position.

3. The method for zero-gradient position correction of switched reluctance motor current based on single-pulse injection according to claim 2, characterized in that: The high-frequency pulse is determined based on the low-speed rotation of the rotor during calibration, the required angular resolution of the lookup table, and the current sampling accuracy, ensuring a sufficient number of pulse sampling points within a complete mechanical cycle. Simultaneously, the frequency should also ensure that each pulse has a measurable current change during both the rising and falling phases, so that the inductance can be calculated using the current slope difference method.

4. The method for zero-gradient position correction of switched reluctance motor current based on single-pulse injection according to claim 1, characterized in that: The method for detecting zero current change rate using the current gradient method: Since the position where the current change rate is zero under high-speed operation is the current peak position; the position where the current change rate is zero is located directly by capturing the moment when the current peak value is located in each cycle.

5. The method for zero-gradient position correction of switched reluctance motor current based on single-pulse injection according to claim 1, characterized in that: The phase inductance value corresponding to the current rotor position is calculated using the current slope difference method. : in: This is the DC bus voltage. The rate of change of current at the falling edge of the injected single pulse; The rate of change of current on the rising edge of the injected single pulse.

6. A method for monitoring operating conditions using the single-pulse injection-based zero-gradient position correction method for switched reluctance motors according to any one of claims 1 to 5, characterized in that: The expression for determining the status of the operating condition monitoring system is: The operating condition monitoring process is as follows: in, This is a current status indicator. This is a speed status indicator. This is a system status flag; 1 indicates a static state, and 0 indicates a dynamic state. This is the peak current of the previous cycle. This is the peak current of the current cycle. The rotational speed of the previous cycle. The rotational speed for the current cycle. This refers to the permissible current limit. This refers to the permissible speed limit; Based on the changes in peak current and rotational speed detected in adjacent cycles, the corresponding current status flags are determined respectively. Speed ​​status flag The current operating status is determined based on the aforementioned status flags: 1) When the peak current change is less than or equal to the set threshold (current allowable limit) and the speed change is less than or equal to the set threshold (speed allowable limit), it is determined to be a non-changing state, i.e., the motor is in steady-state operation. Step 3 (single pulse injection) is stopped until step 6, and online correction of the current zero gradient position is stopped. ; 2) When the peak current change exceeds the set threshold (current tolerance limit) or the speed change exceeds the set threshold (speed tolerance limit), it is determined to be a changing state, i.e., the motor is in dynamic operating condition. The single-pulse injection in step 3 is executed until step 6, implementing online correction of the current zero gradient position. .

7. The method for monitoring operating conditions according to claim 6, characterized in that: The determination of the allowable current limit is as follows: First, the motor is placed under multiple different "torque-speed" steady-state operating conditions, and current samples are continuously collected at multiple current zero gradient positions under each operating condition; then, the maximum fluctuation extreme value of the current in the entire operating condition range is extracted, and a set safety margin is given on the basis of the maximum natural fluctuation extreme value, which is the allowable current variation limit.

8. The method for monitoring operating conditions according to claim 5, characterized in that: The determination of the allowable speed limit is as follows: First, the motor is placed under multiple different "torque-speed" steady-state operating conditions, and speed samples are continuously collected at multiple current zero gradient positions under each operating condition; then, the maximum fluctuation extreme value of the speed is extracted within the entire operating condition range, and a set safety margin is given on the basis of the maximum natural fluctuation extreme value, which is the allowable speed change limit.

9. An electronic device, characterized in that, It includes a processor and a memory, the processor being configured to execute a computer program stored in the memory to implement the steps of the operating condition monitoring method as described in any one of claims 6 to 8.

10. A computer program product, characterized in that... It includes computer-executable instructions, which, when executed, are used to implement the working condition monitoring method of claims 6-8.

Images