Dynamic loss control method for annular bus of motor driver

Abstract

The invention discloses a dynamic loss control method for an annular bus of a motor driver, which belongs to the technical field of motor driver control and comprises the following steps: a pulse optimizer changes pulse modulation of multi-phase voltage to generate a modulation signal; solving to obtain real-time current distribution of the annular bus by the mathematical solving model; the loss calculation module calculates the real-time ohmic loss of the annular bus according to the current distribution and the distribution resistance of the annular bus, and feeds the real-time ohmic loss back to the pulse optimizer; the pulse optimizer continuously adjusts the modulation signal and compares the change of the ohmic loss until the ohmic loss reaches the minimum value, and the modulation signal at the moment serves as a final control command; and finally, the control command is sent to each driving bridge arm. According to the method, the loss of the motor driver bus is controlled to reach the minimum value, and the phenomena of voltage fluctuation, current imbalance and ring current on the annular bus can be effectively reduced, so that the ring current of the distributed driver bus can be effectively avoided, and the efficiency of the motor driver is improved.

Description

Technical Field

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

[0002] Motor drives are widely used, such as robot joints, electric vehicle power systems, servo systems, etc. As the demand for technical indicators such as improving efficiency and reducing volume becomes stronger, traditional centralized motor drives have evolved into distributed motor drives. In distributed motor drives, single-phase drive bridge arms and bus capacitors are distributed in different directions and connected in parallel through a ring bus. However, multiple drive bridge arms are prone to mutual interference on the ring bus, generating local circulation, causing local heating and other problems, which limits the output capacity of the motor drive. Summary of the invention

[0003] The technical solution of the present invention aims at the technical problem that the existing technical solutions are too single, and provides a solution that is significantly different from the existing technologies. It mainly provides a method for dynamic loss control of the ring bus of a motor driver, which is used to solve the technical problem proposed in the above background technology that multiple drive bridge arms are prone to interfere with each other on the ring bus, generate local circulating currents, and then cause local heating.

[0004] The technical solution adopted by the present invention to solve the above technical problems is: A method for controlling dynamic loss of a motor drive ring bus, comprising the following steps: S1, when the motor driver is running, a conventional control command of a multi-phase voltage is generated by a multi-phase motor control method, and the conventional control command is sent to a pulse optimizer; S2, a pulse optimizer changes the pulse modulation of the multi-phase voltage, generates a modulation signal, and sends the modulation signal to a mathematical solution model; S3, solving the mathematical solution model to obtain the real-time current distribution of the ring bus, and sending the current distribution to the loss calculation module; S4, the 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 the ohmic loss back to the pulse optimizer; S5, the pulse optimizer continuously adjusts the modulation signal and compares the change of ohmic loss until the ohmic loss reaches the minimum value. The modulation signal at this time is used as the final control command; S6. The final control command is sent to each drive bridge arm one by one to realize the output of the driver electric energy to the motor.

[0005] Specifically, in steps S2 and S5, changing the pulse modulation of the multi-phase voltage includes at least one of the mean value, phase, and frequency of the pulse modulation.

[0006] Specifically, in step S3, the mathematical solution model is established based on the physical distribution of the driving bridge arm on the ring bus; the mathematical solution model 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.

[0007] Specifically, in step S4, the distributed resistance of the annular busbar is calculated by a resistance formula, or by a resistance formula and taking skin effect into consideration.

[0008] Specifically, in step S4, the loss calculation module uses the current and resistance of each bus segment to obtain 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.

[0009] Specifically, step S5 includes: the pulse optimizer generates a modulation signal and reads the fed-back ohmic loss; then the read ohmic loss is compared with the last ohmic loss, and when the data increases, a reverse change is taken; when the data decreases, the same direction change is continued, and the size of the data difference is judged; until the ohmic loss is reduced and the change is small compared with the last time it was read, it means that the ohmic loss has reached the minimum value.

[0010] Compared with the prior art, the present invention has the following beneficial effects: The present invention calculates the current distribution of the ring bus (i.e., the current size 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 by combining the current distribution and distributed resistance of the ring bus through a loss calculation module; and continuously adjusts the modulation signal through a pulse optimizer, and compares the change in ohmic loss until the ohmic loss reaches a minimum value, and the modulation signal at this time is used as the final control command. Compared with the multi-phase control method of a conventional motor driver, the method described in 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 a 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.

[0011] The present invention minimizes the bus ohmic loss and effectively avoids the occurrence of circulating current by only optimizing the control method of the motor driver ring bus; at the same time, no additional sensors or hardware are required, and the cost is low.

[0012] The present invention will be explained in detail below with reference to the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1It is the hardware wiring, control module and control signal diagram of the present invention; Figure 2 This is an example of a control strategy for changing the pulse mean value of the pulse optimizer in the present invention; wherein, Figure (a) is the pulse signal before adjustment, and Figure (b) is the pulse signal after adjustment; Figure 3 This is an example of a control strategy for changing the pulse phase of the pulse optimizer in the present invention; wherein, Figure (a) is the pulse signal before adjustment, and Figure (b) is the pulse signal after adjustment; Figure 4 This is an example of a control strategy for the pulse optimizer in the present invention to change the pulse frequency to double the frequency; wherein, Figure (a) is the pulse signal before adjustment, and Figure (b) is the pulse signal after adjustment.

[0014] Figure numerals: 1. driving bridge arm; 2. ring bus; 3. motor; 4. mathematical solution model; 5. multi-phase 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 DESCRIPTION

[0015] To facilitate understanding of 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 content disclosed in the present invention more thorough and comprehensive.

[0016] like Figure 1 As 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 connected in parallel through a circular or other ring-shaped ring bus 2, and each drive bridge arm 1 is distributed at different positions of the ring bus 2.

[0017] Specifically, the driving bridge arm 1 includes five or more independent single-phase bridge arms (1.1, 1.2, ..., 1.N); the ring bus 2 includes two positive and negative ring conductors (2.1, 2.2), and is powered by the positive and negative electrodes of the external power supply 13 respectively, and a plurality of parallel bus capacitors 14 are distributed on the ring bus; the single-phase output ports of the driving bridge arm 1 are respectively connected to the plurality of phase line ports of the motor 3, and the number of the phase line ports of the motor 3 is the same as the number of the bridge arm 1; the multi-phase ports (3.1, 3.2, ..., 3.N) of the motor 3 are connected to the driving bridge arm 1 one by one.

[0018] The dynamic loss control method of the ring bus of the above motor driver is: When the motor driver is running, a conventional multi-phase motor control method 5 is used to generate a conventional control command 6 of the multi-phase voltage; and the conventional control command 6 is sent to a 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 a mathematical solution model 4 to solve and obtain a real-time current distribution 9 of the ring bus 2; According to the current distribution 9 and the distributed resistance of the ring bus 2 (calculated using the resistance formula), the loss calculation module 11 is sent 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 optimal value. At this time, the modulation signal 8 is sent to the drive bridge arm 1 as the final control command 10 to realize the output of the driver electric energy to the motor 3. The final control command 10 is a group of control signals (10.1, 10.2, ..., 10.N), which are sent to each drive bridge arm 1 one by one.

[0019] According to the physical distribution of the driving 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 ring bus resistance and capacitance, or a circuit network model including the ring bus resistance, capacitance and inductance, and is used to calculate the current distribution 9 at different positions of the ring bus 2 (the solution can be performed using a time domain discrete ODE model, or a Laplace domain model for circuit network solution).

[0020] The loss calculation module 11 calculates the ohmic loss 12 based on Ohm's current law, or based on Ohm's current law and high-frequency skin effect model. According to the current of each section of copper busbar and the resistance of this section of copper busbar, using Ohm's law I 2 R is used to calculate the power; the resistance R of each bus section is calculated using the resistance formula, and the AC resistance is calculated by considering the skin effect; the current I of each bus section can be obtained through the previous current distribution 9; the sum of the bus losses of all sections is the total ohmic loss 12.

[0021] The pulse optimizer 7 reads the conventional control command 6, and adjusts one or more of the parameters such as the mean, phase, frequency, etc. of the pulse modulation, thereby changing the instantaneous output value of the phase voltage at different times and the average value of the motor phase-to-ground voltage without changing the average value of the motor phase-to-phase voltage.

[0022] The pulse optimizer 7 generates a modulation signal 8 and reads the ohmic loss 12. If the loss 12 increases compared to the last reading, it means that the change direction of the modulation signal 8 is wrong and a reverse change should be taken; if the loss 12 decreases compared to the last reading, it means that the change direction of the modulation signal 8 is correct and a change in the same direction should be taken; if the ohmic loss 12 changes slightly compared to the last reading (determined by a preset threshold, for example, less than 1% of the total loss), it means that the optimal setting is achieved.

[0023] Embodiment 1: In this embodiment, the pulse optimizer 7 changes the control strategy of the pulse mean value as follows Figure 2 As shown, all become wider or narrower, but the amount of change of all signals remains consistent.

[0024] Embodiment 2: In this embodiment, the pulse optimizer 7 changes the control strategy of the pulse phase as follows Figure 3 As shown, any one or more phases can be independently and freely moved left or right while keeping the width unchanged.

[0025] Embodiment 3: In this embodiment, the pulse optimizer 7 changes the pulse frequency to a double frequency control strategy, and any one or more phases (such as Figure 4 The frequency can be changed by changing the last phase as shown in the figure. The frequency is not limited to 2 times, but can be 0.5 times, 3 times, or a non-integer or non-integer fraction of the frequency. The duty cycle after adjustment is the same as before adjustment.

[0026] Embodiment 4: The control strategies in embodiments 1 to 3 are used together.

[0027] In each embodiment, the motor 3 is a 6-phase motor, and the signal time increases gradually (in actual use, the signal time does not increase gradually, but is modulated in real time. The reason why it is drawn as gradually increasing here is that the SVPWM drawing method conventionally recognized in the industry is gradually increasing, which is easier to display).

[0028] The motor driver bus loss is controlled to the minimum state to solve the problem of "multiple drive bridge arms are prone to mutual interference on the ring bus, generating local circulation, causing local heating" and other problems. The working principle is: ① Reduce circulating current: Reducing bus losses helps reduce circulating current on the ring bus. Circulating current is caused by the bus voltage difference between bridge arms. When the bus loss is reduced through bus loss optimization, the voltage difference and circulating current phenomenon will be curbed, and the local heating problem caused by circulating current can be avoided.

[0029] ② Improve current distribution: In a multi-bridge drive system, the current distribution of each bridge arm should be aimed at reducing losses 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.

[0030] ③ Improve system stability: The reduction of bus loss helps to improve the voltage stability of the entire motor drive system. The improved system voltage stability can reduce the current fluctuation and torque fluctuation caused by voltage fluctuation. In addition, for other devices powered by the same DC power supply, the interference caused by voltage fluctuation is reduced.

[0031] ④ Reduce local heating: Due to the reduction of busbar loss, the heat generated by the current flowing through the busbar is reduced, thereby reducing the risk of local heating. Reducing local heating can improve the reliability and life of the system.

[0032] 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, thereby solving the mutual interference and local heating problems between multiple drive bridge arms and improving the performance and reliability of the system.

[0033] The above is an exemplary description of the present invention in combination with the accompanying drawings. It is obvious that the specific implementation of the present invention is not limited to the above-mentioned method. As long as such non-substantial improvements are 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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