A double three-phase permanent magnet motor online branch cutting control method

Abstract

The application discloses an online branch cutting control method of a double three-phase permanent magnet motor, when a fault occurs in one branch, the voltage of the fault branch is reconstructed, the coupling disturbance generated by the fault branch is predicted based on a cross-coupling model between the branches, the disturbance voltage is compensated in time, the overcurrent generated by the disturbance in the normal branch is inhibited, and the online smooth cutting and exiting of the fault branch are realized. The application effectively solves the problem that the overcurrent of the normal branch is caused when the fault branch of the double branch permanent magnet motor is cut, and significantly improves the fault tolerance and maneuverability of the permanent magnet motor in the field of ship propulsion.

Description

Technical Field

[0001] This invention belongs to the field of permanent magnet motor control technology, specifically relating to a control method for online disconnection of faulty branches in a dual three-phase permanent magnet motor when a branch fault occurs. Background Technology

[0002] Dual three-phase permanent magnet motors are widely used in applications requiring extremely high continuous operation, such as ship propulsion, aerospace, and electric vehicles, due to their high power density, high reliability, and good fault tolerance. A dual three-phase permanent magnet motor typically consists of two independent three-phase branches (Branch 1 and Branch 2), each powered by an independent inverter. When a fault occurs in one branch (such as a short circuit or open circuit in the power transistor), to ensure continued system operation, the faulty branch needs to be disconnected promptly, and the remaining normal branches provide dated torque output.

[0003] However, during the process of disconnecting the faulty branch, due to the strong electromagnetic coupling (including mutual inductance coupling and back electromotive force coupling) between the faulty branch and the normal branch, the sudden disconnection of the faulty branch will induce a large voltage disturbance in the normal branch, which will then cause overcurrent in the normal branch. In severe cases, it will cause the normal branch protection to trip, paralyzing the entire system. In the existing technology, the drive signals of both branches are usually blocked simultaneously, and then the normal branch is restarted. However, this method will cause a power interruption, affecting the maneuverability of vehicles and ships.

[0004] Therefore, how to achieve online and smooth disconnection of faulty branches of dual three-phase permanent magnet motors, suppress overcurrent in normal branches, and improve the fault-tolerant operation capability of the system is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] The present invention aims to provide an online branch switching control method for a dual three-phase permanent magnet motor, in order to solve the problem of overcurrent in the normal branch when the faulty branch is switched out in the prior art, realize the shock-free online switching of the faulty branch, and improve the fault tolerance and maneuverability of the motor drive system.

[0006] The technical solution adopted by this invention to solve its technical problem is: an online branch switching control method for a dual three-phase permanent magnet motor, used in a permanent magnet propulsion motor with ABC phase windings in branch one and DEF phase windings in branch two, based on a control system composed of an inverter and a modulation and PWM generation module. The inverter consists of two sets of three-phase inverter H-bridges composed of switching transistors T1 to T12. The branch one winding is connected to the H-bridge composed of switching transistors T1 to T6, and the branch two winding is connected to the H-bridge composed of switching transistors T7 to T12. Both the branch one H-bridge and the branch two H-bridge are connected to the voltage through the modulation and PWM generation module. The system includes a reconstructing module and a disturbance prediction module. The disturbance prediction module comprises a transient disturbance module, a steady-state disturbance module, and a decaying pulse module. The voltage reconstructing module of one branch (normal branch) reconstructs the voltage of the other branch (faulty branch) under fault conditions based on the current, rotor position, and DC bus voltage of the faulty branch. The disturbance prediction module of the normal branch predicts the coupled disturbance of the next cycle based on the reconstructed voltage, the currents of both branches, the angular frequency, and the enable signal of the other branch (faulty branch). The predicted coupled disturbance is superimposed on the original voltage reference value of this branch. The steps are as follows:

[0007] Step 1, Fault Detection and Branch Enable Signal Generation: The fault is identified by detecting the short-circuit current of the lower arm of the H-bridge of the branch inverter, and the branch enable signal E2=0 is immediately generated, while the branch enable signal E1 remains at 1.

[0008] Step 2, Voltage Reconfiguration (taking Branch 1 controller as an example): The voltage reconfiguration module in Branch 1 obtains the three-phase current i of Branch 2 in real time. a2 i b2 i c2 Reconstruct the two-phase voltage of the branch according to the current polarity:

[0009] If i a2 ≥0, reconstruct u a2 =0; if i a2 <0, reconstruct u a2 =U dc ;

[0010] If i b2 ≥0, reconstruct u b2 =0; if i b2 <0, reconstruct u b2 =U dc ;

[0011] If i c2 ≥0, reconstruct u c2 =0; if i c2 <0, reconstruct u c2 =U dc ;

[0012] Then, the current rotor position angle θ is read, and the dq component of the reconfigured voltage is calculated according to the Clarke-Park transform formula: Calculate u d2_recon u q2_recon ;

[0013] Step 3, Disturbance Prediction: The disturbance prediction module in branch 1 receives the reconfigured voltage u from the faulty branch. d2_recon u q2_recon And the two currents i in the (faulty branch) branch. d2 i q2 Motor angular frequency ω, branch current i d1 i q1 The enable signal E2 for branch 2; the transient disturbance module calculates the transient disturbance value u based on the cross-coupled voltage equation of the motor in the dq coordinate system. d2_sr u q2_sr The steady-state disturbance module is based on the branch current i (in the normal branch). d1 i q1 Calculate the steady-state disturbance value u using angular frequency ω d2_wr u q2_wr The attenuation pulse module inverts and ramps the enable signal of the faulty branch, then multiplies the inverted signal with the ramped signal to obtain the attenuation pulse signal E. 2r ;

[0014] Step 4, Disturbance Compensation and Normal Branch Control: Predict the coupled disturbance voltage generated by the disconnection of the faulty branch in the next control cycle, and superimpose the predicted coupled disturbance voltage onto the original voltage reference value of this branch, thereby compensating for the disturbance in real time, suppressing the overcurrent of the normal branch, and realizing the smooth online disconnection of the faulty branch.

[0015] Furthermore, the voltage reconstruction module performs voltage reconstruction as follows: it detects the three-phase currents (ia, ib, ic) of the faulty branch. For each phase, when the phase current is greater than or equal to zero, the phase voltage is reconstructed to 0; when the phase current is less than zero, the phase voltage is reconstructed to the DC bus voltage Udc. That is: if the three-phase current ia of the faulty branch is greater than or equal to 0, then the phase voltage ua is reconstructed to 0; if ia is less than 0, then ua is reconstructed to Udc; if ib is greater than or equal to 0, then ub is reconstructed to 0; if ib is less than 0, then ub is reconstructed to Udc; if ic is greater than or equal to 0, then uc is reconstructed to 0; if ic is less than 0, then uc is reconstructed to Udc. Then, based on the reconstructed three-phase voltages ua, ub, uc and the current rotor position angle θ, according to the transformation rule of "from three-phase stationary coordinate system to two-phase rotating coordinate system (3s / 2r)," the d-axis component and q-axis component of the reconstructed voltage of the faulty branch in the dq rotating coordinate system are calculated (e.g., if branch two is the faulty branch, then u is obtained). d2_recon and u q2_recon ).

[0016] Furthermore, the transient disturbance module calculates the transient disturbance value using the following formula:

[0017] The specific coefficients are determined based on the motor parameters.

[0018] Furthermore, the steady-state disturbance module calculates the steady-state disturbance value using the following formula: In the formula, Md and Mq are the mutual inductances along the d and q axes, respectively.

[0019] Furthermore, the attenuation pulse module inverts E2 (initially 1, becomes 0 after a fault) to obtain ~E2, and simultaneously performs ramp processing on E2, setting the ramp time constant to 5 control cycles to obtain the ramp signal ramp(E2). ~E2 is then multiplied by ramp(E2) to obtain the attenuation pulse signal E. 2r Its waveform jumps from 0 to 1 at the falling edge of E2, and then descends to 0 by ramp.

[0020] Furthermore, in step 4, the original vector controller of branch 1 calculates the reference value u of the base voltage of this branch based on the speed command and current feedback. d1_ref0 u q1_ref0 Then, the total disturbance mentioned above is superimposed. , The modulation and PWM generation module uses the compensated voltage reference value for PWM modulation to drive the inverter in branch one, while the inverter in branch two is in a high-impedance state with pulse blocked (E2=0). Finally, the transient disturbance value is multiplied by the inverted enable signal of the fault branch (so that the transient disturbance is zero when the fault branch is enabled and immediately injected when the enable is deactivated), and the steady-state disturbance value is multiplied by the decayed pulse signal. The products of the two are then added together to obtain the total disturbance value that needs to be compensated to the voltage reference value of the normal branch. , .

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. This invention estimates the actual phase voltage of the faulty branch after the inverter is blocked in real time through a voltage reconstruction module, without the need for additional voltage sensors, and is low in cost and easy to implement in engineering.

[0023] 2. This invention introduces a branch-to-branch cross-coupling model, which divides the coupling disturbance caused by the removal of a faulty branch to a normal branch into transient disturbance and steady-state disturbance, and performs prediction and compensation for them respectively, which significantly improves the accuracy and response speed of disturbance suppression.

[0024] 3. This invention utilizes an attenuation pulse module to achieve smooth injection of steady-state disturbances, avoiding new current surges caused by sudden changes in compensation amount, ensuring stable current during fault branch disconnection, and achieving significant overcurrent suppression effect.

[0025] 4. The method of the present invention is applicable to occasions such as ship propulsion where continuous operation and rapid maneuverability are required, and improves the fault-tolerant operation capability of the dual three-phase permanent magnet motor drive system. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the topology of the dual three-phase permanent magnet motor of the present invention;

[0027] Figure 2 This is a general diagram of the online branch switching control method for dual three-phase permanent magnet motors of the present invention;

[0028] Figure 3 This is a schematic diagram of the voltage reconstruction module of the present invention (taking branch two as an example of a faulty branch).

[0029] Figure 4 This is a schematic diagram of the disturbance prediction module of the present invention (taking branch two as an example of a faulty branch).

[0030] Figure 5 This is a schematic diagram of the pulse attenuation module of the present invention (taking branch two as an example of a faulty branch). Detailed Implementation

[0031] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. The following embodiments are only used to explain the present invention and are not intended to limit the scope of protection of the present invention.

[0032] This embodiment uses a dual three-phase permanent magnet motor as an example. The motor parameters are: rated power 100kW, rated speed 600rpm, number of pole pairs 4, and DC bus voltage U. dc =540V, two three-phase branches are independently controlled, using a field-oriented control (FOC) strategy, with a control cycle of 100μs. See the topology diagram of the dual-branch permanent magnet motor system. Figure 1 .

[0033] The control system consists of an inverter and a modulation and PWM generation module. The inverter is composed of two sets of three-phase inverter H-bridges consisting of switching transistors T1 to T12. The first branch winding is connected to the H-bridge consisting of switching transistors T1 to T6, and the second branch winding is connected to the H-bridge consisting of switching transistors T7 to T12. Both the first and second branch H-bridges are connected to the modulation and PWM generation module. Each branch adds a voltage reconstruction module and a disturbance prediction module to the original vector control. The disturbance prediction module includes a transient disturbance module, a steady-state disturbance module, and a damped pulse module. The voltage reconstruction module of one branch (normal branch) reconstructs the voltage of the other branch (faulty branch) under fault conditions based on the current, rotor position, and DC bus voltage of the faulty branch. The disturbance prediction module of the normal branch predicts the coupling disturbance of the next cycle based on the reconstructed voltage, the current of the two branches, the angular frequency, and the enable signal of the other branch (faulty branch). The predicted coupling disturbance is superimposed on the original voltage reference value of this branch.

[0034] Suppose that at a certain moment, a power transistor short-circuit fault occurs in branch 2, and the system needs to disconnect branch 2 online, with only branch 1 continuing to operate.

[0035] The voltage reconstruction module performs voltage reconstruction as follows: if ia≥0, then reconstruct ua=0; if ia<0, then reconstruct ua=Udc; if ib≥0, then reconstruct ub=0; if ib<0, then reconstruct ub=Udc; if ic≥0, then reconstruct uc=0; if ic<0, then reconstruct uc=Udc.

[0036] Then, based on the reconstructed three-phase voltages ua, ub, and uc, and the current rotor position angle θ, the d-axis and q-axis components of the reconstructed voltage of the fault branch in the dq rotating coordinate system are calculated according to the transformation rule from the three-phase stationary coordinate system to the two-phase rotating coordinate system (3s / 2r). (If branch two is taken as the fault branch, then u is obtained.) d2_recon and u q2_recon ).

[0037] Reference Figure 2 As shown, the present invention provides an online branch switching control method for a dual three-phase permanent magnet motor, the steps of which are as follows.

[0038] Step 1: Fault detection and branch enable signal generation.

[0039] The fault is identified by detecting the short-circuit current of the lower arm of the H-bridge of the branch inverter by the fault detection circuit. The branch two enable signal E2=0 is immediately generated (low level indicates that the drive output is disabled), while the branch one enable signal E1 remains at 1.

[0040] The method of the present invention is started in the next control cycle after fault detection and confirmation.

[0041] Step 2, voltage reconstruction (taking branch controller 1 as an example).

[0042] The voltage reconstruction module in branch one acquires the three-phase current i of branch two in real time. a2 i b2 i c2 (Obtained through sampling by a current sensor), the two-phase voltage of the branch is reconstructed according to the current polarity: if i a2 ≥0, reconstruct u a2 =0; if i a2 <0, reconstruct u a2 =U dc =540V. Similarly, u is obtained. b2 u c2 .

[0043] Then, the current rotor position angle θ (measured by the rotary transformer) is read, and the dq component of the reconfigured voltage is calculated according to the Clarke-Park transform formula. Calculate u d2_recon u q2_recon See the voltage reconstruction diagram. Figure 3 .

[0044] The voltage reconstruction of branch two is similar and will not be elaborated here.

[0045] Step 3, disturbance prediction.

[0046] like Figure 4 As shown, the disturbance prediction module in the branch controller receives the reconfiguration voltage u of the faulty branch. d2_recon u q2_recon And the two currents i in the (faulty branch) branch. d2 i q2 (Also obtained through coordinate transformation), motor angular frequency ω, branch current i d1 i q1 And the enable signal E2 for branch 2.

[0047] The transient disturbance module calculates transient disturbances based on the cross-coupled voltage equations of the dual three-phase motor in the dq coordinate system. The specific coefficients are calibrated based on the motor parameters. This transient disturbance reflects the impulsive disturbance caused by sudden changes in current and voltage at the moment the faulty branch is disconnected.

[0048] In this embodiment, mutual inductance and leakage inductance values ​​are obtained through offline identification, and table lookup or real-time calculation is implemented through programming.

[0049] In this embodiment, mutual inductance and leakage inductance values ​​are obtained through offline identification, and table lookup or real-time calculation is implemented through programming.

[0050] The steady-state disturbance module is based on the branch current i of the (normal branch). d1i q1 The formula for motor parameter angular frequency ω Calculate the steady-state disturbance value u d2_wr u q2_wr Where Md and Mq are the mutual inductances along the d and q axes, respectively. This steady-state disturbance reflects the disturbance component that persists in the normal branch after the faulty branch is disconnected due to the mutual inductance coupling between branches.

[0051] The attenuation pulse module inverts and ramps the enable signal of the faulty branch (e.g., enable signal E2 for branch two), and multiplies the inverted and ramped results to obtain the attenuation pulse signal E. 2r The decaying pulse signal generates a gradually decaying pulse waveform at the falling edge of the fault branch enable signal, which is used to control the injection timing and decay rate of steady-state disturbances.

[0052] In this embodiment, the attenuation pulse module inverts E2 (initially 1, becomes 0 after a fault) to obtain ~E2, and simultaneously performs ramp processing on E2, with the ramp time constant set to 5 control cycles (500μs), resulting in the ramp signal ramp(E2). Multiplying ~E2 by ramp(E2) yields the attenuation pulse signal E. 2r Its waveform jumps from 0 to 1 at the falling edge of E2, and then descends to 0 by ramp.

[0053] The attenuation pulse module inverts E2 (initially 1, becomes 0 after a fault) to obtain ~E2, and simultaneously performs ramp processing on E2, with the ramp time constant set to 5 control cycles (500μs) to obtain the ramp signal ramp(E2). Multiplying ~E2 by ramp(E2) yields the attenuation pulse signal E. 2r Its waveform jumps from 0 to 1 at the falling edge of E2, and then descends to 0 by ramp.

[0054] Step 4, Disturbance Compensation and Normal Branch Control: Predict the coupled disturbance voltage generated by the disconnection of the faulty branch in the next control cycle; superimpose the predicted coupled disturbance voltage onto the original voltage reference value of this branch, thereby compensating for the disturbance in real time, suppressing the overcurrent of the normal branch, and realizing the smooth online disconnection of the faulty branch.

[0055] like Figure 4 As shown, the original vector controller in branch 1 calculates the reference value u of the base voltage of this branch based on the speed command and current feedback. d1_ref0 u q1_ref0 .

[0056] Then the above total disturbances are superimposed. , .

[0057] The compensated voltage reference value is used for PWM modulation to drive the inverter in branch one. Meanwhile, the inverter in branch two has its pulse blocked (E2=0) and is in a high-impedance state. See the disturbance compensation diagram below. Figure 2 .

[0058] Finally, the transient disturbance values ​​are multiplied by the inverted enable signal of the faulty branch (so that the transient disturbance is zero when the faulty branch is enabled, and the transient disturbance is immediately injected when the enable is deactivated), and the steady-state disturbance values ​​are multiplied by the decay pulse signal. The products of the two are then added together to obtain the final total disturbance that needs to be compensated to the reference voltage value of the normal branch. , See the diagram for disturbance prediction. Figure 4 A schematic diagram of the attenuation pulse signal generation is shown below. Figure 5 .

[0059] The above embodiment takes the faulty branch 2 and normal branch 1 as an example. In actual application, the same method can be used when any branch fails. Just set the enable signal of the corresponding branch to zero, and the voltage reconstruction module and disturbance prediction module in the controller of the other branch can perform calculations for the faulty branch.

[0060] Furthermore, the voltage reconstruction method is not limited to the simple polarity decision described above. Other reconstruction strategies may also be adopted according to the fault type (such as open circuit or short circuit), but all of them should fall within the protection scope of this invention.

[0061] The ramp function of the attenuation pulse module can be selected as linear ramp, exponential ramp, or custom curve to optimize compensation smoothness.

[0062] The above embodiments are merely illustrative of the principles and effects of the present invention, as well as some of the application examples. For those skilled in the art, various modifications and improvements can be made without departing from the inventive concept of the present invention, and these all fall within the protection scope of the present invention.

Claims

1. A method for online branch switching control of a dual three-phase permanent magnet motor, used in a permanent magnet propulsion motor having a branch winding one and a branch winding two, characterized in that: The control system is based on an inverter and a modulation and PWM generation module. The inverter consists of two H-bridges composed of switching transistors T1 to T12. The first branch winding is connected to the H-bridge composed of switching transistors T1 to T6, and the second branch winding is connected to the H-bridge composed of switching transistors T7 to T12. Both the first and second branch H-bridges are connected to a voltage reconstruction module and a disturbance prediction module via the modulation and PWM generation module. The disturbance prediction module includes a transient disturbance module, a steady-state disturbance module, and a damped pulse module. The voltage reconstruction module for the normal branch reconstructs the voltage of the faulty branch based on the current, rotor position, and DC bus voltage of the faulty branch. The disturbance prediction module for the normal branch predicts the coupling disturbance of the next cycle based on the reconstructed voltage, the currents of the two branches, the angular frequency, and the enable signal of the faulty branch, and superimposes it onto the original voltage reference value of this branch. The steps are as follows: Step 1: Identify the fault by detecting the short-circuit current of the lower arm of the H-bridge of the inverter in branch 2, and immediately generate the branch 2 enable signal E2=0, while the branch 1 enable signal E1 remains at 1. Step 2: The voltage reconstruction module in branch 1 acquires the three-phase current i of branch 2 in real time. a2 i b2 i c2 Reconstruct the two-phase voltage of the branch according to the current polarity: if i a2 ≥0, reconstruct u a2 =0; if i a2 <0, reconstruct u a2 =U dc ; if i b2 ≥0, reconstruct u b2 =0; if i b2 <0, reconstruct u b2 =U dc ; if i c2 ≥0, reconstruct u c2 =0; if i c2 <0, reconstruct u c2 =U dc Read the current rotor position angle θ, and calculate the dq component of the reconfigured voltage according to the Clarke-Park transform formula. ; Step 3: The disturbance prediction module in branch 1 receives the reconfiguration voltage u of the faulty branch. d2_recon u q2_recon and branch two current i d2 i q2 Motor angular frequency ω, branch current i d1 i q1 The enable signal E2 for branch 2; the transient disturbance module calculates the transient disturbance value u based on the cross-coupled voltage equation of the motor in the dq coordinate system. d2_sr u q2_sr The steady-state disturbance module is based on the branch current i. d1 i q1 Calculate the steady-state disturbance value u using angular frequency ω d2_wr u q2_wr The attenuation pulse module inverts and ramps the fault branch enable signal E2, and then multiplies the inverted and ramped results to obtain the attenuation pulse signal E. 2r ; Step 4: Predict the coupling disturbance voltage generated by the disconnection of the faulty branch in the next control cycle, and add it to the original voltage reference value of this branch to compensate for the disturbance in real time, suppress the overcurrent of the normal branch, and realize the smooth online disconnection of the faulty branch.

2. The online branch switching control method for a dual three-phase permanent magnet motor according to claim 1, characterized in that, The voltage reconstruction module performs voltage reconstruction as follows: if the fault branch current ia≥0, then the phase voltage ua=0 is reconstructed; if ia<0, then ua=Udc is reconstructed. If ib≥0, then reconstruct ub=0; if ib<0, then reconstruct ub=Udc. If ic≥0, then reconstruct uc=0; if ic<0, then reconstruct uc=Udc; based on the reconstructed three-phase voltages ua, ub, uc and the current rotor position angle θ, the d-axis and q-axis components of the reconstructed voltage of the fault branch in the dq rotating coordinate system are calculated.

3. The online branch switching control method for a dual three-phase permanent magnet motor according to claim 1 or 2, characterized in that, The transient disturbance module is described by the formula Calculate the transient disturbance value.

4. The online branch switching control method for a dual three-phase permanent magnet motor according to claim 3, characterized in that, The steady-state disturbance module is described by the formula Calculate the steady-state disturbance value, where Md and Mq are the mutual inductances along the d and q axes, respectively.

5. The online branch switching control method for a dual three-phase permanent magnet motor according to claim 4, characterized in that, The attenuation pulse module inverts E2 to obtain ~E2, and simultaneously performs ramp processing on E2, with the ramp time constant set to 5 control cycles, to obtain the ramp signal ramp(E2). Multiplying ~E2 by ramp(E2) yields the attenuation pulse signal E. 2r Then descend the slope to 0.

6. The online branch switching control method for a dual three-phase permanent magnet motor according to claim 5, characterized in that, In step 4, branch one calculates the reference value u of the base voltage of this branch based on the speed command and current feedback. d1_ref0 u q1_ref0 Then the total disturbance is superimposed. , The modulation and PWM generation module uses the compensated voltage reference value to perform PWM modulation, driving the inverter in branch one while the inverter in branch two is in a high-impedance state. The transient disturbance value is multiplied by the inverted enable signal of the fault branch, and the steady-state disturbance value is multiplied by the decaying pulse signal. The products are then added together to obtain the total disturbance value that needs to be compensated to the normal branch voltage reference value. , .

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