A Method for Controlling the Dynamic Loss of the Ring Busbar of a Motor Driver

Abstract

The present invention discloses a method for dynamically controlling the loss of a ring bus of a motor driver, belonging to the technical field of motor driver control, and comprising the following steps: a pulse optimizer changes the pulse modulation of a multi-phase voltage to generate a modulation signal; a mathematical solution model solves to obtain the current distribution of the ring bus in real time; a loss calculation module calculates the real-time ohmic loss of the ring bus according to the current distribution and the distributed resistance of the ring bus, and feeds it back to the pulse optimizer; the pulse optimizer continuously adjusts the modulation signal and compares the change in the ohmic loss until the ohmic loss reaches the minimum value, and at this time, the modulation signal is used as the final control command; the final control command is sent to each drive bridge arm. The present invention controls the bus loss of the motor driver to reach the minimum value, which can effectively reduce the voltage fluctuation, current imbalance and circulating current phenomenon on the ring bus, thereby effectively avoiding the occurrence of bus circulating current in the distributed driver and improving the efficiency of the motor driver.

Description

Technical Field

[0001] The present invention mainly relates to the technical field of motor drive control, and specifically provides a method for controlling the dynamic loss of a ring bus in a motor drive. Background Art

[0002] Motor drives are widely used, such as in robot joints, electric vehicle power systems, servo systems, etc. With the increasing demand for technical indicators such as improving efficiency and reducing volume, traditional centralized motor drives have evolved into distributed motor drives. In a distributed motor drive, single-phase drive arms and bus capacitors are distributed in different positions and are connected in parallel through a ring bus. However, multiple drive arms are prone to interfering with each other on the ring bus and generating local circulating currents, which can cause problems such as local heating, limiting the output capacity of the motor drive. Summary of the Invention

[0003] The technical solution of the present invention addresses the technical problem of the overly single solution of the prior art and provides a solution significantly different from the prior art. It mainly provides a method for controlling the dynamic loss of a ring bus in a motor drive to solve the technical problem that multiple drive arms are prone to interfering with each other on the ring bus and generating local circulating currents, which in turn causes local heating as described in the above background art.

[0004] The technical solution adopted by the present invention to solve the above technical problems is as follows:

[0005] A method for controlling the dynamic loss of a ring bus in a motor drive, comprising the following steps:

[0006] S1. When the motor drive is running, generate a conventional control command for a multi-phase voltage through a multi-phase motor control method and send the conventional control command to a pulse optimizer;

[0007] S2. The pulse optimizer changes the pulse modulation of the multi-phase voltage to generate a modulation signal and sends the modulation signal to a mathematical solution model;

[0008] S3. The mathematical solution model solves to obtain the real-time current distribution of the ring bus and sends the current distribution to a loss calculation module;

[0009] S4. The loss calculation module calculates the real-time ohmic loss of the ring bus based on the current distribution and the distributed resistance of the ring bus and feeds the ohmic loss back to the pulse optimizer;

[0010] S5. The pulse optimizer continuously adjusts the modulation signal and compares the change in the ohmic loss until the ohmic loss reaches the minimum value. At this time, the modulation signal is used as the final control command;

[0011] S6. The final control commands are sent to each drive bridge arm one by one to realize the output of the electrical energy of the driver to the motor.

[0012] Specifically, in steps S2 and S5, changing the pulse modulation of the polyphase voltage includes at least one of the mean value, phase, and frequency of the pulse modulation.

[0013] Specifically, in step S3, the mathematical solution model is established according to the physical distribution of the drive bridge arm on the ring bus; the mathematical solution model is a circuit network model including the resistance and capacitance of the ring bus, or a circuit network model including the resistance, capacitance, and inductance of the ring bus.

[0014] Specifically, in step S4, the distributed resistance of the ring bus is calculated by the resistance formula, or calculated by the resistance formula and considering the skin effect.

[0015] Specifically, in step S4, the loss calculation module obtains the power of each section of the bus by using the current and resistance of each section of the bus as the loss of each section of the bus, and the sum of the losses of all sections of the bus is the total ohmic loss.

[0016] Specifically, in step S5, it specifically includes: the pulse optimizer generates a modulation signal and reads the feedback ohmic loss; then compares the read ohmic loss with the previous ohmic loss. When the data increases, take the reverse change; when the data decreases, continue to take the same direction change and judge the size of the data difference; until the ohmic loss is smaller than the previous reading and the change is small, indicating that the ohmic loss reaches the minimum value.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] The present invention calculates the current distribution of the ring bus (i.e., the current magnitude of each section of the bus) in real time through a mathematical solution model, and then calculates the real-time ohmic loss of the ring bus through the loss calculation module in combination with the current distribution and distributed resistance of the ring bus; and continuously adjusts the modulation signal through the pulse optimizer and compares the change of the ohmic loss until the ohmic loss reaches the minimum value. At this time, the modulation signal is used as the final control command. Compared with the polyphase control method of a conventional motor driver, the method of the present invention calculates and optimizes the loss of the ring bus in real time and outputs the optimized final control command to guide the motor driver to control the motor. By controlling the bus loss of the motor driver to reach the minimum value, the voltage fluctuation, current imbalance, and circulating current phenomenon on the ring bus can be effectively reduced, thereby effectively avoiding the occurrence of distributed driver bus circulating current and improving the efficiency of the motor driver.

[0019] The present invention only optimizes the control method of the annular busbar of the motor driver, so that the ohmic loss of the busbar reaches the lowest, effectively avoiding the occurrence of circulating current; at the same time, there is no need to add additional sensors or hardware, and the cost is relatively low.

[0020] The present invention will be explained in detail below in conjunction with the drawings and specific embodiments. Description of the Drawings

[0021] Figure 1 It is the hardware wiring, control module and control signal diagram in the present invention;

[0022] Figure 2 It is an example of a control strategy for the pulse optimizer in the present invention to change the pulse mean value; among them, Figure (a) is the pulse signal before adjustment, and Figure (b) is the pulse signal after adjustment;

[0023] Figure 3 It is an example of a control strategy for the pulse optimizer in the present invention to change the pulse phase; among them, Figure (a) is the pulse signal before adjustment, and Figure (b) is the pulse signal after adjustment;

[0024] Figure 4 It is an example of a control strategy for the pulse optimizer in the present invention to change the pulse frequency to double frequency; among them, Figure (a) is the pulse signal before adjustment, and Figure (b) is the pulse signal after adjustment.

[0025] Reference numerals: 1, drive bridge arm; 2, annular busbar; 3, motor; 4, mathematical solution model; 5, multiphase motor control method; 6, conventional control command; 7, pulse optimizer; 8, modulation signal; 9, current distribution; 10, final control command; 11, loss calculation module; 12, ohmic loss; 13, external power supply; 14, bus capacitor. Detailed Embodiments

[0026] For the convenience of understanding the present invention, the present invention will be described more comprehensively below with reference to the relevant drawings. Several embodiments of the present invention are given in the drawings, but the present invention can be implemented in different forms and is not limited to the embodiments described in the text. On the contrary, these embodiments are provided to make the disclosure of the present invention more thorough and comprehensive.

[0027] As Figure 1 shown, the motor driver in this embodiment is a distributed motor driver, which contains five or more distributed single-phase inverter drive bridge arms 1. The DC ports of the drive bridge arms 1 are electrically paralleled through a circular or other loop-shaped annular busbar 2, and each drive bridge arm 1 is distributed in different orientations on the annular busbar 2.

[0028] Specifically, the drive bridge arm 1 includes five or more independent single-phase bridge arms (1.1, 1.2, …, 1.N); the ring bus 2 includes two ring conductors, a positive one and a negative one (2.1, 2.2), which are respectively powered by the positive and negative electrodes of the external power supply 13, and a plurality of parallel bus capacitors 14 are distributed on the ring bus; the single-phase output ports of the drive bridge arm 1 are respectively connected to a plurality of phase wire ports of the motor 3, and the number of phase wire ports of the motor 3 is the same as the number of bridge arms 1; the multi-phase ports (3.1, 3.2, …, 3.N) of the motor 3 are connected to the drive bridge arm 1 in one-to-one correspondence.

[0029] The method for controlling the dynamic loss of the ring bus of the above motor driver is as follows:

[0030] When the motor driver is running, through the conventional multi-phase motor control method 5, a conventional control command 6 for generating multi-phase voltage is generated; and the conventional control command 6 is sent to the pulse optimizer 7 to change the pulse modulation of the multi-phase voltage, including but not limited to the mean value, phase, frequency, etc. of the pulse modulation, to generate a modulation signal 8, which is sent to the mathematical solution model 4 to solve and obtain the current distribution 9 of the real-time ring bus 2;

[0031] According to the current distribution 9 and the distributed resistance of the ring bus 2 (calculated using the resistance formula), it is sent to the loss calculation module 11 to calculate the real-time ohmic loss 12 of the ring bus 2, and the ohmic loss 12 is fed back to the pulse optimizer 7; the pulse optimizer 7 continuously adjusts the modulation signal 8 and compares the change of the ohmic loss 12 until the ohmic loss 12 reaches the minimum value. At this time, the pulse optimizer 7 reaches the optimum, and the modulation signal 8 at this time is used as the final control command 10 and sent to the drive bridge arm 1 to realize the output of the electrical energy of the driver to the motor 3. The final control command 10 is a set of control signals (10.1, 10.2, …, 10.N), which are sent to each drive bridge arm 1 in one-to-one correspondence.

[0032] Based on the physical distribution of the drive bridge arm 1 on the ring bus 2, a mathematical solution model 4 of the circuit is established to solve the current distribution on the ring bus 2; the mathematical solution model 4 is a circuit network model including the resistance and capacitance of the ring bus, or a circuit network model including the resistance, capacitance, and inductance of the ring bus, and is used to calculate the current distribution 9 at different positions of the ring bus 2 (which can be solved using the time-domain discrete ODE model or the Laplace-domain model for circuit network solution).

[0033] The loss calculation module 11 calculates the ohmic loss 12 based on Ohm's current law, or based on Ohm's current law and the high-frequency skin effect model. According to the current of each section of the copper bus and the resistance of this section of the copper bus, using Ohm's law I 2R obtains the power; the resistance R of each section of the busbar is calculated by the resistance formula and the AC resistance calculated considering the skin effect; the current I of each section of the busbar can be obtained from the previous current distribution 9; the sum of the busbar losses of all sections is the total ohmic loss 12.

[0034] The pulse optimizer 7 reads the conventional control command 6 and changes one or more of the parameters such as the mean value, phase, and frequency of the pulse modulation, so as to change the instantaneous output value of the phase voltage at different times and the average value of the voltage from the motor phase to the ground without changing the average value of the voltage from the motor phase to phase.

[0035] The pulse optimizer 7 generates the modulation signal 8 and reads the ohmic loss 12. If the loss 12 increases compared with the previous reading, it means that the change direction of the modulation signal 8 is wrong and the reverse change should be taken; if the loss 12 decreases compared with the previous reading, it means that the change direction of the modulation signal 8 is correct and the same-direction change should be taken; if the change of the ohmic loss 12 is small compared with the previous reading (judged by a preset threshold, for example, less than 1% of the total loss), it means that the optimization is achieved.

[0036] Example 1: In this example, the control strategy of the pulse optimizer 7 to change the pulse mean value is as Figure 2 shown, all become wider or all become narrower, but the change amount of all signals remains the same.

[0037] Example 2: In this example, the control strategy of the pulse optimizer 7 to change the pulse phase is as Figure 3 shown, any one or more phases can be independently shifted left or right freely, but the width remains unchanged.

[0038] Example 3: In this example, the control strategy of the pulse optimizer 7 to change the pulse frequency to double frequency, any one or more phases (such as Figure 4 shown to change the last phase), can change the frequency, not limited to 2 times frequency, it can be 0.5 times frequency, 3 times frequency, or non-integer, non-integer fraction multiple frequency. The duty cycle after adjustment is the same as that before adjustment.

[0039] Example 4: The control strategies in Examples 1 to 3 are used together.

[0040] In each example, the motor 3 is a 6-phase motor and the signal time increases gradually (in actual use, the signal time is not gradually increasing but is a real-time variable modulation. Here, it is drawn as gradually increasing because the conventional SVPWM drawing method recognized in the industry is gradually increasing, which is more convenient for display).

[0041] Control the bus loss of the motor driver to the lowest level to solve the problems such as "multiple drive bridge arms are prone to interfere with each other on the ring bus, generating local circulating current, which will cause local heating". The working principle is as follows:

[0042] ①Reduce circulating current: The reduction of bus loss helps to reduce the circulating current on the ring bus. The circulating current is caused by the bus voltage difference between the bridge arms. When the loss is optimized by reducing the bus loss, the voltage difference and the phenomenon of circulating current will be curbed, and at the same time, the problem of local heating caused by the circulating current can be avoided.

[0043] ②Improve current distribution: In a multi-bridge arm drive system, the current distribution of each bridge arm should aim to reduce the loss as much as possible. If the bus loss is low, it means that the current flows more efficiently on the bus and the energy distribution is more reasonable.

[0044] ③Improve system stability: The reduction of bus loss helps to improve the voltage stability of the entire motor drive system. When the system voltage stability is improved, the current fluctuation and torque fluctuation caused by voltage fluctuation can be reduced. In addition, for other devices powered by the same DC power supply, the interference caused by voltage fluctuation is reduced.

[0045] ④Reduce local heating: Due to the reduction of bus loss, the heat generated by the current flowing through the bus is reduced, thus reducing the risk of local heating. The reduction of local heating can improve the reliability and lifespan of the system.

[0046] In summary, by controlling the bus loss of the motor driver, the voltage fluctuation, current imbalance and circulating current phenomenon on the ring bus can be effectively reduced, thus solving the mutual interference and local heating problems between multiple drive bridge arms, and improving the performance and reliability of the system.

[0047] The above has given an exemplary description of the present invention in conjunction with the drawings. Obviously, the specific implementation of the present invention is not limited by the above methods. As long as this non-substantial improvement is made by adopting the method concept and technical solution of the present invention, or the concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A method for controlling dynamic loss of a motor drive ring bus, characterized in that: The steps include: S1, when the motor driver is running, a conventional control command (6) of a multi-phase voltage is generated by a multi-phase motor control method (5), and the conventional control command (6) is sent to a pulse optimizer (7); S2, a pulse optimizer (7) changes the pulse modulation of the multi-phase voltage to generate a modulation signal (8), and sends the modulation signal (8) to the mathematical solution model (4); S3, solving the mathematical solution model (4) to obtain the real-time current distribution (9) of the ring bus (2), and sending the current distribution (9) to the loss calculation module (11); S4, the loss calculation module (11) calculates the real-time ohmic loss (12) of the ring bus (2) according to the current distribution (9) and the distributed resistance of the ring bus (2), and feeds back the ohmic loss (12) to the pulse optimizer (7); S5, the pulse optimizer (7) continuously adjusts the modulation signal (8) and compares the change of the ohmic loss (12) until the ohmic loss (12) reaches a minimum value, and the modulation signal (8) at this time is used as the final control command (10); S6. The final control command (10) is sent to each drive bridge arm (1) one by one, so as to realize the output of the drive electric energy to the motor (3).

2. A method for controlling dynamic loss of a motor drive ring bus according to claim 1, characterized in that: In steps S2 and S5, changing the pulse modulation of the multi-phase voltage includes changing at least one of the mean value, phase, and frequency of the pulse modulation.

3. A method for controlling dynamic loss of a motor drive ring bus according to claim 1, characterized in that: In step S3, the mathematical solution model (4) is established based on the physical distribution of the driving bridge arm (1) on the ring bus (2); the mathematical solution model (4) is a circuit network model including the ring bus resistance and capacitance, or a circuit network model including the ring bus resistance, capacitance and inductance.

4. A method for controlling dynamic loss of a motor drive ring bus according to claim 1, characterized in that: In step S4, the distributed resistance of the annular busbar (2) is calculated using a resistance formula, or is calculated using a resistance formula and taking skin effect into consideration.

5. A method for controlling dynamic loss of a motor drive ring bus according to claim 4, characterized in that: In step S4, the loss calculation module (11) uses the current and resistance of each bus segment to calculate the power of each bus segment as the loss of each bus segment, and the sum of the losses of all bus segments is the total ohmic loss (12).

6. A method for controlling dynamic loss of a motor drive ring bus according to claim 1, characterized in that: Step S5 specifically includes: the pulse optimizer (7) generates a modulation signal (8) and reads the fed-back ohmic loss (12); then the read ohmic loss (12) is compared with the last ohmic loss (12), and when the data increases, the reverse change is adopted; when the data decreases, the same direction change is continued, and the size of the data difference is determined; until the ohmic loss (12) is reduced and the change is small compared with the last reading, indicating that the ohmic loss (12) has reached the minimum value.

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