Composite control system and control method of ship electric propulsion system PMSM

Abstract

The invention relates to the technical field of ship power propulsion control, in particular to a composite control system and method for a ship electric propulsion system PMSM. The system comprises an outer rotating speed closed-loop control unit, an inner current closed-loop control unit, a coordinate conversion unit, a sliding mode estimation unit and a PWM modulation unit, and the sliding mode estimation unit calculates corresponding rotor position and rotor speed estimation values according to operation data of an output measurement module of a PMSM. And the estimated value is applied to the outer rotating speed closed-loop control unit and the inner current closed-loop control unit, so that double-closed-loop compound control is realized, and the dynamic performance and robustness of PMSM control are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ship power propulsion control, and particularly relates to a compound control system and a control method of a PMSM of a ship electric propulsion system. BACKGROUND

[0002] Ship power propulsion represents the development direction of future ship power technology, because ship power propulsion has the advantages of strong energy saving and emission reduction, high operation performance, etc., and the most core component of the power propulsion system is a permanent magnet synchronous motor (PMSM), because it has many advantages such as low loss, high power factor, high starting torque and strong overload capacity. Generally, a sensor motor, a direct-current excitation permanent magnet synchronous motor and an alternating-current synchronous motor are selected, these technologies are relatively mature, and in recent years, a superconducting motor has been developed, which will be applied in the field of ship transportation in the near future. The permanent magnet synchronous motor has a smaller volume capacity under the same power, so compared with an alternating-current asynchronous motor and an electric excitation alternating-current synchronous motor, it has greater advantages.

[0003] However, the control performance of the permanent magnet synchronous propulsion motor has more stringent standards for ships, and is continuously improved with the wide application of the permanent magnet synchronous propulsion motor in the ship propulsion system. The control technology of the permanent magnet synchronous propulsion motor includes vector control, direct torque control, constant voltage frequency ratio control, PID control and sliding mode control, and the core reason why the sliding mode control is widely concerned is its unique advantages. The sliding mode control method has good applicability to the system, and has a lower requirement for the accuracy of the mathematical model. At the same time, when the system enters the sliding mode, the sliding mode control is not sensitive to parameter changes, and has strong anti-interference ability in the operation process of the ship permanent magnet synchronous propulsion motor. In addition, the sliding mode control algorithm has a simple structure and low engineering implementation difficulty. Although the sliding mode control has obvious advantages, it still has some defects in practical application. Affected by its own structural characteristics, the sliding mode control is easy to cause system chattering. The chattering generation mechanism is complex and involves many factors, and it is difficult to completely eliminate. SUMMARY

[0004] The purpose of the present application is to provide a compound control system and a control method of a PMSM of a ship electric propulsion system, which solves the above technical problems.

[0005] In order to achieve the above object, the application provides a compound control system of a ship electric propulsion system PMSM, which comprises an outer rotating speed closed loop control unit, an inner current closed loop control unit, a coordinate conversion unit, a sliding mode estimation unit and a PWM modulation unit, the PWM modulation unit is connected with the PMSM, the output measurement module of the PMSM is connected with the sliding mode estimation unit through the coordinate conversion unit, the outer rotating speed closed loop control unit and the inner current closed loop control unit are connected with the output end of the sliding mode estimation unit, and the inner current closed loop control unit is connected with the PWM modulation unit through the coordinate conversion unit.

[0006] Preferably, the coordinate conversion unit comprises a Clark conversion module, a Park conversion module and an inverse Park conversion module, the Clark conversion module is connected with the PMSM, converts the three-phase current of the PMSM into actual current in a two-phase static coordinate system, the output end of the Clark conversion module is connected with the Park conversion module, and the Park conversion module is used for converting the actual current in the two-phase static coordinate system into q-axis current and d-axis current in a synchronous rotating coordinate system.

[0007] The inverse Park conversion module is arranged between the inner current closed loop control unit and the PWM modulation unit, and is used for converting the q-axis voltage and the d-axis voltage in the synchronous rotating coordinate system output by the inner current closed loop control unit into α-axis voltage and β-axis voltage in the two-phase static coordinate system.

[0008] Preferably, the sliding mode estimation unit is used for estimation of rotating position and rotating speed, the input end of the sliding mode estimation unit is connected with the output end of the Clark conversion module, and is used for obtaining the actual current in the two-phase static coordinate system, the output end of the sliding mode estimation unit comprises a rotating position angle output end and a rotating speed output end, the rotating speed output end is connected with the outer rotating speed closed loop control unit, and the rotating position angle output end is connected with the Park conversion module.

[0009] Preferably, the outer rotating speed closed loop control unit comprises a speed acquisition module and a rotating speed PI controller, the speed acquisition module is connected with the rotating speed output end, the speed acquisition module is used for obtaining a set reference rotating speed and an actual rotating speed calculated by the sliding mode estimation unit, and inputs the actual rotating speed and the set reference rotating speed into the rotating speed PI controller, and the rotating speed PI controller outputs a q-axis current reference value according to the speed difference between the actual rotating speed and the set reference rotating speed.

[0010] Preferably, the inner current closed loop control unit comprises a q-axis current controller and a d-axis current controller.

[0011] The q-axis current controller is connected with a q-axis current acquisition module, the q-axis current acquisition module is connected with a q-axis current output end of the Park conversion module, the q-axis current acquisition module is used for acquiring a q-axis current reference value and an actual q-axis current calculated by the sliding mode estimation unit, and the q-axis current acquisition module is connected with an output end of the speed PI controller; the q-axis current controller outputs a q voltage reference value according to a q-axis current difference between the actual q-axis current and the q-axis current reference value.

[0012] The d-axis current controller is connected with a d-axis current acquisition module, the d-axis current acquisition module is connected with a d-axis current output end of the Park conversion module, the d-axis current acquisition module is used for acquiring a d-axis current reference value and an actual d-axis current calculated by the sliding mode estimation unit, and the d-axis current controller outputs a d voltage reference value according to a d-axis current difference between the actual d-axis current and the d-axis current reference value.

[0013] Preferably, the output end of the q-axis current controller, the output end of the d-axis current controller and the rotation position angle output end of the Park conversion module are all connected with the inverse Park conversion module.

[0014] The control method of the composite control system of the ship electric propulsion system PMSM is as follows:

[0015] Step S1: constructing a PMSM mathematical module for outputting PMSM operation data, setting a set reference speed and a d-axis current reference value;

[0016] Step S2: collecting three-phase current values in the output PMSM operation data in real time, and outputting actual speed, actual q-axis current, actual d-axis current and rotation position angle under the feedback of the actual state of the PMSM through a coordinate conversion unit and a sliding mode estimation unit;

[0017] Step S3: outputting a double closed-loop control instruction signal through the data fed back by step S2 through an outer speed closed-loop control unit and an inner current closed-loop control unit;

[0018] Step S4: controlling the PMSM operation state according to the double closed-loop control instruction signal by a PWM modulation unit.

[0019] Preferably, in step S2, the PMSM current equation in the two-phase static coordinate system is as follows:

[0020]

[0021] Wherein, i α and i β are the α-axis and β-axis PMSM stator current values, u α and u β are the α-axis and β-axis stator voltages in the two-phase static coordinate system, e αand e β Back EMF of α-axis and β-axis, R s Stator resistance, L s Stator inductance

[0022] The back EMF equation is as follows:

[0023]

[0024] Where ω e is the electrical angular velocity of the rotor, ψ f is the permanent magnet flux linkage, θ e is the rotor rotation position angle

[0025] The difference between the observed value and the actual value of the stator current of the α-axis and β-axis is taken, and the difference of the current is taken as the sliding mode surface, and the sliding mode surface formula is as follows:

[0026]

[0027] Where s(x) is the sliding mode surface, and are the deviation values of the stator currents of the α-axis and β-axis PMSM respectively, and are the observed values of the stator currents of the α-axis and β-axis PMSM respectively

[0028] The sign function is introduced, and the sliding mode control law is as follows:

[0029]

[0030] Where sgn(x) is the sign function, v α and v β are the sliding mode observation functions, k a is the sliding mode gain coefficient

[0031] The data model of the sliding mode observer of the sliding mode estimation unit is as follows:

[0032]

[0033] The current error model is obtained as follows:

[0034]

[0035] When the sliding mode surface reaches the steady state, the error of the current is 0, and the back EMF is obtained as follows:

[0036]

[0037] The low-pass filter of the ω c cut-off frequency is added to the back EMF, and the speed estimation value is obtained by the arctangent method and rotor position estimate as follows:

[0038]

[0039] The above formula converts the actual current in the two-phase stationary coordinate system of the PMSM into rotor position and speed, which is used for dual-loop closed-loop control of speed and current.

[0040] Therefore, the present invention adopts the above-mentioned composite control system and control method of a marine electric propulsion system PMSM, which has the following beneficial effects: the sliding mode estimation unit calculates the corresponding rotor position and rotor speed estimates based on the operating data of the output measurement module of the PMSM, and applies the estimates to the external speed closed-loop control unit and the internal current closed-loop control unit to realize dual closed-loop composite control, thereby improving the dynamic performance and robustness of PMSM control.

[0041] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0042] Figure 1 This is a block diagram of a composite control system for a marine electric propulsion system (PMSM) according to the present invention.

[0043] Figure 2 This is a flowchart of the control method of the present invention.

[0044] Figure 3 This is a graph showing the rotational speed curve of the PMSM in the simulation experiment;

[0045] Figure 4 The diagram shows the three-phase current curves of the PMSM in the simulation experiment.

[0046] Figure 5 This is a graph showing the torque angle tracking curve of the PMSM in the simulation experiment. Detailed Implementation

[0047] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product is in use. They are used only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," and "connect" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0048] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0049] like Figure 1 As shown, a composite control system for a marine electric propulsion system (PMSM) includes an external speed closed-loop control unit, an internal current closed-loop control unit, a coordinate transformation unit, a sliding mode estimation unit, and a PWM modulation unit. The PWM modulation unit is connected to the PMSM for direct control of the PMSM. The output measurement module of the PMSM is connected to the sliding mode estimation unit through the coordinate transformation unit. Both the external speed closed-loop control unit and the internal current closed-loop control unit are connected to the output of the sliding mode estimation unit. The internal current closed-loop control unit is connected to the PWM modulation unit through the coordinate transformation unit.

[0050] The coordinate transformation unit includes a Clark transformation module, a Park transformation module, and an inverse Park transformation module. The Clark transformation module is connected to the PMSM and converts the three-phase current of the PMSM into the actual current in the two-phase stationary coordinate system. The output of the Clark transformation module is connected to the Park transformation module and is used to convert the actual current in the two-phase stationary coordinate system into the q-axis current and d-axis current in the synchronous rotating coordinate system.

[0051] The inverse Park transformation module is located between the inner current closed-loop control unit and the PWM modulation unit. It is used to convert the q-axis voltage and d-axis voltage output by the inner current closed-loop control unit in the synchronous rotating coordinate system into the α-axis voltage and β-axis voltage in the two-phase stationary coordinate system.

[0052] The sliding mode estimation unit is used to estimate the rotational position and speed. The input of the sliding mode estimation unit is connected to the output of the Clark transformation module to obtain the actual current in the two-phase stationary coordinate system. The output of the sliding mode estimation unit includes a positioning angle output terminal and a speed output terminal. The speed output terminal is connected to the external speed closed-loop control unit, and the rotational position angle output terminal is connected to the Park transformation module.

[0053] The external speed closed-loop control unit includes a speed acquisition module and a speed PI controller. The speed acquisition module is connected to the speed output terminal. The speed acquisition module is used to acquire the set reference speed and the actual speed calculated by the sliding mode estimation unit, and inputs the actual speed and the set reference speed into the speed PI controller. The speed PI controller outputs the q-axis current reference value according to the speed difference between the actual speed and the set reference speed.

[0054] The internal current closed-loop control unit includes a q-axis current controller and a d-axis current controller. The q-axis current controller is connected to a q-axis current acquisition module, which is connected to the q-axis current output of the Park transformation module. The q-axis current acquisition module acquires the q-axis current reference value and the actual q-axis current calculated by the sliding mode estimation unit. The q-axis current acquisition module is also connected to the output of the speed PI controller. The q-axis current controller outputs a q-voltage reference value based on the difference between the actual q-axis current and the q-axis current reference value. Similarly, the d-axis current controller is connected to a d-axis current acquisition module, which is connected to the d-axis current output of the Park transformation module. The d-axis current acquisition module acquires the d-axis current reference value and the actual d-axis current calculated by the sliding mode estimation unit. The d-axis current controller outputs a d-voltage reference value based on the difference between the actual d-axis current and the d-axis current reference value.

[0055] The output terminals of the q-axis current controller, the d-axis current controller, and the rotational position angle output terminal of the Park transformation module are all connected to the inverse Park transformation module.

[0056] Based on the above-mentioned control method for a composite control system of a ship electric propulsion system (PMSM), such as Figure 2 As shown, the specific steps are as follows:

[0057] Step S1: Construct a PMSM math module to output PMSM operating data, and set the reference speed and d-axis current reference value.

[0058] Step S2: Real-time acquisition of the three-phase current values ​​in the output PMSM operation data, and output of the actual rotation speed, actual q-axis current, actual d-axis current and rotation position angle of the PMSM under real state through coordinate transformation unit and sliding mode estimation unit.

[0059] In step S2, the PMSM current equations in the two-phase stationary coordinate system are as follows:

[0060]

[0061] Among them, i α and i β These are the PMSM stator current values ​​along the α and β axes, respectively. α and u β Let e ​​be the stator voltage along the α-axis and β-axis in a two-phase stationary coordinate system. α and e β The back electromotive force, R, is divided into α-axis and β-axis. s L is the stator resistance. s For stator inductance;

[0062] The back electromotive force equation is as follows:

[0063]

[0064] Where, ω e Let ψ be the electric angular velocity of the rotor. f For permanent magnet flux linkage, θ e This refers to the rotor's rotational position angle;

[0065] The observed and actual values ​​of the stator currents along the α and β axes are subtracted, and this difference is used as the sliding surface. The formula for the sliding surface is as follows:

[0066]

[0067] Where s(x) is the sliding surface, and These are the deviation values ​​of the PMSM stator current along the α-axis and β-axis, respectively. and These are the observed values ​​of the PMSM stator current along the α-axis and β-axis, respectively;

[0068] Introducing the sign function, the sliding mode control law is as follows:

[0069]

[0070] Where sgn(x) is the sign function, v α and v β These are the sliding mode observation functions, k a This is the sliding mode gain coefficient;

[0071] The data model for the sliding mode observer of the sliding mode estimation unit is as follows:

[0072]

[0073] The current error model obtained from the above is as follows:

[0074]

[0075] When the sliding surface reaches a steady state, the current error is 0, and the back electromotive force is obtained as follows:

[0076]

[0077] Then add ω to the back electromotive force c Low-pass filtering at the cutoff frequency, followed by arctangent method to obtain the speed estimate. and rotor position estimate as follows:

[0078]

[0079] The above formula converts the actual current in the two-phase stationary coordinate system of the PMSM into rotor position and speed, which is used for dual-loop closed-loop control of speed and current.

[0080] Step S3: The data fed back from step S2 is used to output dual closed-loop control command signals through the external speed closed-loop control unit and the internal current closed-loop control unit.

[0081] Step S4: The PWM modulation unit controls the operating status of the PMSM according to the dual closed-loop control command signal.

[0082] To verify the superiority of this embodiment, a simulation experiment was conducted. The preset motor speed was 1000 r / min, and the motor parameters were as follows:

[0083]

[0084] After the three-phase stator current of the motor is acquired by the sensor, it first undergoes a Clark transform. This transform converts the current signal in the three-phase stationary coordinate system to the two-phase stationary α-β coordinate system, obtaining the corresponding current components. After the Clark transform, a Park transform is further performed on the current signal, changing the α-β coordinate system to the dq coordinate system, thereby obtaining the corresponding rotating coordinate system current components. The coordinate transformation process for the voltage signal is the same as that for the current, also requiring sequential Clark and Park transforms to complete the signal conversion.

[0085] The actual current value in the dq coordinate system is compared with the preset value, controlled by the q-axis current controller and the d-axis current controller, and finally these two virtual values ​​(U) are... α and U β Through vector conversion, the values ​​are converted into actual control values ​​(Ua / Ub / Uc) to control the motor, thereby realizing the dual closed-loop control of the permanent magnet synchronous motor.

[0086] Observe the motor's speed, torque angle, and current using an oscilloscope. For example... Figure 3 , Figure 4 as well as Figure 5 As shown, during the process of the motor speed increasing from 0 r / min to the set value of 1000 r / min, although there is a certain degree of speed overshoot in the initial stage of startup, the designed control strategy exhibits excellent dynamic response performance. Thanks to the rapid adjustment capability of this strategy, the motor quickly converges to the target speed of 1000 r / min and maintains a stable operating state, with no significant fluctuations in the speed curve. Furthermore, the three-phase current of the motor also has a fast dynamic response speed, stabilizing within a very short time. Figure 5 In the diagram, the blue line represents the predicted torque angle, and the brown line represents the actual torque angle. The simulation results show that the predicted torque angle and the actual torque angle are basically the same.

[0087] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A composite control system for a marine electric propulsion system (PMSM), characterized in that: It includes an external speed closed-loop control unit, an internal current closed-loop control unit, a coordinate transformation unit, a sliding mode estimation unit, and a PWM modulation unit. The PWM modulation unit is connected to the PMSM. The output measurement module of the PMSM is connected to the sliding mode estimation unit through the coordinate transformation unit. Both the external speed closed-loop control unit and the internal current closed-loop control unit are connected to the output terminal of the sliding mode estimation unit. The internal current closed-loop control unit is connected to the PWM modulation unit through the coordinate transformation unit.

2. The composite control system for a marine electric propulsion system (PMSM) according to claim 1, characterized in that: The coordinate transformation unit includes a Clark transformation module, a Park transformation module, and an inverse Park transformation module. The Clark transformation module is connected to the PMSM and converts the three-phase current of the PMSM into the actual current in the two-phase stationary coordinate system. The output of the Clark transformation module is connected to the Park transformation module and is used to convert the actual current in the two-phase stationary coordinate system into the q-axis current and d-axis current in the synchronous rotating coordinate system. The inverse Park transformation module is located between the inner current closed-loop control unit and the PWM modulation unit. It is used to convert the q-axis voltage and d-axis voltage output by the inner current closed-loop control unit in the synchronous rotating coordinate system into the α-axis voltage and β-axis voltage in the two-phase stationary coordinate system.

3. The composite control system for a marine electric propulsion system (PMSM) according to claim 2, characterized in that: The sliding mode estimation unit is used to estimate the rotational position and speed. The input of the sliding mode estimation unit is connected to the output of the Clark transformation module to obtain the actual current in the two-phase stationary coordinate system. The output of the sliding mode estimation unit includes a positioning angle output terminal and a speed output terminal. The speed output terminal is connected to the external speed closed-loop control unit, and the rotational position angle output terminal is connected to the Park transformation module.

4. The composite control system for a marine electric propulsion system (PMSM) according to claim 3, characterized in that: The external speed closed-loop control unit includes a speed acquisition module and a speed PI controller. The speed acquisition module is connected to the speed output terminal. The speed acquisition module is used to acquire the set reference speed and the actual speed calculated by the sliding mode estimation unit, and inputs the actual speed and the set reference speed into the speed PI controller. The speed PI controller outputs the q-axis current reference value according to the speed difference between the actual speed and the set reference speed.

5. The composite control system for a marine electric propulsion system (PMSM) according to claim 4, characterized in that: The internal current closed-loop control unit includes a q-axis current controller and a d-axis current controller; The q-axis current controller is connected to a q-axis current acquisition module, which is connected to the q-axis current output of the Park transformation module. The q-axis current acquisition module is used to acquire the q-axis current reference value and the actual q-axis current calculated by the sliding mode estimation unit. The q-axis current acquisition module is also connected to the output of the speed PI controller. The q-axis current controller outputs a q-voltage reference value based on the q-axis current difference between the actual q-axis current and the q-axis current reference value. The d-axis current controller is connected to a d-axis current acquisition module, which is connected to the d-axis current output terminal of the Park transformation module. The d-axis current acquisition module is used to acquire the d-axis current reference value and the actual d-axis current calculated by the sliding mode estimation unit. The d-axis current controller outputs a d-voltage reference value based on the d-axis current difference between the actual d-axis current and the d-axis current reference value.

6. The composite control system for a marine electric propulsion system (PMSM) according to claim 5, characterized in that: The output terminals of the q-axis current controller, the d-axis current controller, and the rotational position angle output terminal of the Park transformation module are all connected to the inverse Park transformation module.

7. The control method for a composite control system of a marine electric propulsion system (PMSM) as described in claim 6, characterized in that, The specific steps are as follows: Step S1: Construct the PMSM mathematical module to output PMSM operating data, and set the reference speed and d-axis current reference value; Step S2: Real-time acquisition of three-phase current values ​​from the output PMSM operation data, and output of the actual rotation speed, actual q-axis current, actual d-axis current, and rotation position angle of the PMSM under real state through coordinate transformation unit and sliding mode estimation unit; Step S3: The data fed back from step S2 is used to output dual closed-loop control command signals through the external speed closed-loop control unit and the internal current closed-loop control unit; Step S4: The PWM modulation unit controls the operating status of the PMSM according to the dual closed-loop control command signal.

8. The control method according to claim 7, characterized in that: In step S2, the PMSM current equations in the two-phase stationary coordinate system are as follows: Among them, i α and i β These are the PMSM stator current values ​​along the α and β axes, respectively. α and u β Let e ​​be the stator voltage along the α-axis and β-axis in a two-phase stationary coordinate system. α and e β The back electromotive force, R, is divided into α-axis and β-axis. s L is the stator resistance. s For stator inductance; The back electromotive force equation is as follows: Where, ω e Let ψ be the electric angular velocity of the rotor. f For permanent magnet flux linkage, θ e This refers to the rotor's rotational position angle; The observed and actual values ​​of the stator currents along the α and β axes are subtracted, and this difference is used as the sliding surface. The formula for the sliding surface is as follows: Where s(x) is the sliding surface, and These are the deviation values ​​of the PMSM stator current along the α-axis and β-axis, respectively. and These are the observed values ​​of the PMSM stator current along the α-axis and β-axis, respectively; Introducing the sign function, the sliding mode control law is as follows: Where sgn(x) is the sign function, v α and v β These are the sliding mode observation functions, k a This is the sliding mode gain coefficient; The data model for the sliding mode observer of the sliding mode estimation unit is as follows: The current error model obtained from the above is as follows: When the sliding surface reaches a steady state, the current error is 0, and the back electromotive force is obtained as follows: Then add ω to the back electromotive force c Low-pass filtering at the cutoff frequency, followed by arctangent method to obtain the speed estimate. and rotor position estimate as follows: The above formula converts the actual current in the two-phase stationary coordinate system of the PMSM into rotor position and speed, which is used for dual closed-loop control of speed and current.

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