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Model prediction three-level direct torque control method based on state trajectory extrapolation

A technology of direct torque control and model prediction, applied in the direction of AC motor control, control system, estimation/correction of motor parameters, etc. problems, to achieve the effect of reducing switching frequency, improving energy utilization, and fast dynamic response capability

Active Publication Date: 2013-08-21
FLOWINN SHANGHAI IND
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  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The vector control scheme based on pulse width modulation has a significant lag in PWM response at low switching frequencies, which seriously damages the dynamic decoupling performance of the system, and even causes the system to fail to work normally.
Although the effective decoupling of the current at low switching frequency can be achieved by using the complex vector current regulator, there is a serious problem of current harmonic distortion as the switching frequency decreases
The direct torque control (DTC) scheme usually works at a high switching frequency, or the ideal control effect cannot be achieved at a low switching frequency
Traditional high-performance control schemes are difficult to meet the requirements of high-performance control at low switching frequencies of several hundred Hz in high-power applications. How to obtain small harmonic distortion at low switching frequencies and enable the system to have fast response capabilities is an important issue for AC A major problem in the high-performance control of high-power motor drives

Method used

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  • Model prediction three-level direct torque control method based on state trajectory extrapolation
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  • Model prediction three-level direct torque control method based on state trajectory extrapolation

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Embodiment 1

[0029] see figure 1 , the asynchronous motor model prediction three-level direct torque control method based on state trajectory extrapolation, using a model predictive controller to replace the hysteresis controller of the traditional direct torque control; the model predictive controller consists of an internal state prediction model and The value function rolling optimization consists of two modules. The flux linkage of the stator and rotor observed by the flux linkage observer, the rotational speed measured by the speed sensor and the switching vector output in the previous sampling period are used as the input of the internal state prediction model, and the state of the internal state prediction model The output, the given torque and the given stator flux obtained from the output of the speed regulator are used as the input of the value function rolling optimization module.

Embodiment 2

[0031] This embodiment is basically the same as Embodiment 1, and the special feature is: the model prediction controller uses the established internal state prediction model to determine the allowable switching vector according to the switching state of the inverter at the previous moment, and for the allowable switching vector through the internal The state prediction model extrapolates the output trajectory, determines a long prediction range, and then takes the average switching frequency of the inverter as the value function, and uses the limited time-domain rolling optimization strategy of model predictive control to solve the optimal switching vector in real time;

[0032] The allowable switch vector determines the allowable switch jump of the inverter according to the switch state of the last sampling period of the inverter, and the allowable switch jump is clearly defined as the continuity of the jump must be maintained, that is: , and there is at most one phase jump ...

Embodiment 3

[0043] The basic technical framework of this embodiment is: a model predictive controller is used to replace the traditional DTC hysteresis controller. The internal state prediction model is established by the NPC three-level inverter driving asynchronous motor mathematical model and the quadratic extrapolation method, and the allowable switching vector is determined according to the switching state of the inverter at the last sampling time. For the allowable switching vector, according to the internal state prediction The model extrapolates the output trajectory, thereby determining a long prediction horizon. Then take the average switching frequency of the inverter as the value function, use the finite time-domain rolling optimization strategy of model predictive control, and solve the optimal switching vector acting on the inverter in real time. The basic principle framework of its implementation is as follows: figure 1 shown.

[0044] Specific embodiments of the present ...

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Abstract

The invention provides a model prediction three-level direct torque control method based on state trajectory extrapolation. According to the method, a traditional hysteresis controller with direct torque control is replaced by a model prediction controller. The method includes the following steps: aiming at allowable switching vectors, determining a step-length prediction range for output trajectory extrapolation by using an internal state prediction model, and with average switching frequency of an inverter as a value function, solving an optimal switching vector in real time to act on the inverter directly according to limited time zone rolling optimization strategies of model prediction control. According to the model prediction three-level direct torque control method based on the state trajectory extrapolation, the switching frequency of an NPC three-level inverter can be reduced to about 300Hz, quick dynamic response capability and ideal current harmonic distortion characteristics can be obtained, and the method has broad application prospects in middle-high voltage and high power fields.

Description

technical field [0001] The invention belongs to the field of low switching frequency control of high-power AC motors, in particular to a model-predicted three-level direct torque control method based on state track extrapolation for low switching frequency control of asynchronous motors. Background technique [0002] Compared with the two-level inverter, the multi-level inverter has the advantages that the output voltage is closer to the sine wave, the withstand voltage level of the device can be reduced, and the harmonic content of the output voltage and current is small. The diode neutral point clamped (NPC) three-level inverter is the most widely used in practical applications due to its simple structure and no need for complex transformers. The withstand voltage of each power tube of the three-level inverter is limited to 1 / 2 of the DC bus voltage, which can nearly double the voltage capacity of the DC bus, and its output voltage is one step higher than the traditional t...

Claims

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Application Information

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IPC IPC(8): H02P23/14H02P27/06
Inventor 阮智勇朱洪志宋文祥
Owner FLOWINN SHANGHAI IND
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