CN104601079B - A kind of single-phase winding open circuit fault-tolerant control system of drive system of electric automobile and method - Google Patents

Abstract

The invention discloses a single-phase winding fault-tolerant control system and method for an electric vehicle drive system. The system includes a PWM generation module, an inverter, a three-phase permanent magnet hub motor, a switch module, a switching control module, a current sampling module and a rotary encoder. In normal operation, the three-phase windings of the motor adopt a star connection mode, and the three-phase currents on the inverter side are three-phase symmetrical currents. When an open-circuit fault of a single-phase winding is detected, the connection mode of the three-phase windings is changed to a delta connection through the switch module. The control method is changed by adjusting the reference value of the three-phase current on the inverter side, and the torque output value is the torque value during normal operation, so as to realize the fault-tolerant operation of the single-phase winding of the three-phase permanent magnet in-wheel motor. The fault-tolerant control system and method of the present invention do not require additional switching tubes and mid-point voltages, reducing equipment investment, and the three-phase currents on the inverter side after fault tolerance are still symmetrical sinusoidal currents, and the amplitude rises to 100% of the current during normal operation. times, the torque output is stable.

Description

A single-phase winding fault-tolerant control system and method for an electric vehicle drive system

technical field

The invention belongs to the technical field of electric vehicle control, and in particular relates to a single-phase winding fault-tolerant control system and method for a drive system of an electric vehicle.

Background technique

With the depletion of fossil fuels such as oil and the increasingly serious environmental pollution, research and development of energy-saving, environmentally friendly and safe vehicles to replace vehicles powered by internal combustion engines is the only way to achieve sustainable development. Among them, electric vehicles are highly praised for their significant advantages of high efficiency and low emissions, and their development has been accelerated. The motor drive system is one of the core technologies of electric vehicles, and the wheel hub drive is the main development direction of the drive mode of electric vehicles in the future. When a single-phase open circuit fault occurs in the motor winding of the drive system, the torque output will fluctuate greatly, resulting in unstable operation of the electric vehicle, which directly threatens personal safety.

Traditionally, some drive system single-phase winding fault-tolerant control methods mainly include:

1. Two-phase four-switch control strategy: The two-phase four-switch strategy is mainly to lead out the midpoint of the winding to the midpoint of the power supply after the single-phase winding is disconnected, forming a neutral line, providing a circuit for the zero-sequence current, and realizing fault-tolerant operation.

2. Two-phase three-arm control strategy: When a single-phase winding breaks, the midpoint of the winding is led to the spare bridge arm, and the fault-tolerant operation of the motor is driven through the three bridge arms.

3. Two-phase full-bridge control strategy: When a single-phase winding is disconnected, all switch tubes of the bridge arm of the faulty phase are turned on, and the normal phase realizes two-phase full-bridge control to realize fault-tolerant operation.

However, the above several traditional control methods affect the overall performance of the fault-tolerant control system due to their own topology and the three-phase current after fault-tolerant operation. For example, method 1 requires a midpoint of the power supply. After fault-tolerant control, due to the influence of zero-sequence current, the midpoint voltage will shift, which will affect the motor control and motor operation. In addition, both methods 1 and 2 require the winding to lead out the neutral line, so this The application of the two methods is limited; both method 2 and method 3 require a switching device, which increases the volume and cost of the system; the three methods also have a neutral line, and the neutral current and the residual phase current are not three-phase symmetrical sinusoidal Current, and the output current of the inverter after fault-tolerant operation varies with the phase of the disconnected winding.

Contents of the invention

The purpose of the present invention is to address the problems existing in the single-phase winding open-circuit fault-tolerant control system of the traditional electric vehicle drive system, and propose a new electric vehicle drive system single-phase winding open-circuit fault-tolerant control system and method, which reduces equipment investment and simplifies the fault-tolerant control algorithm.

For realizing above-mentioned purpose of the invention, the technical scheme that the present invention adopts is:

A single-phase winding open circuit fault-tolerant control system for an electric vehicle drive system, comprising: a PWM generation module, an inverter, a three-phase permanent magnet hub motor, a switch module, a switch control module, a current sampling module and a rotary encoder;

The rotary encoder is connected to the motor for measuring the actual speed of the motor and outputting a speed signal to the PWM generating module;

The current sampling module is connected to the motor, used to measure the three-phase current of the motor, and output current signals to the PWM generation module and switching control module;

The switch module is connected to the three-phase winding of the motor, and includes at least two sets of switches, the first set of switches makes the three-phase windings form a star connection, and the second set of switches makes the three-phase windings form a delta connection;

The PWM generation module includes:

A rotational speed PI regulator, used to obtain a reference current amplitude according to the difference between the reference rotational speed and the actual rotational speed;

The current calculation module is used to calculate the reference value of the inverter output three-phase current through the first current shape function corresponding to the star connection mode or the second current shape function corresponding to the delta connection mode according to the reference current amplitude;

And, the hysteresis comparator is used to combine the reference value and the actual value of the three-phase current to output a PWM sequence for controlling the switches of the inverter;

The switching control module is used to judge whether there is a single-phase winding open circuit according to the current signal output by the current sampling module, and output a switching signal to the switching module and the PWM generating module if there is an open circuit.

Further, during normal operation, the first group of switches is normally open, the second group of switches is normally closed, and the connection mode of the three-phase winding is a star connection. After the switch module receives the switching signal, the second The first group of switches is normally open, the first group of switches is normally closed, and the connection mode of the three-phase winding is delta connection.

further,

The first current shape function is:

Among them, i _mh is the reference current amplitude during normal operation, is the reference value of the three-phase current output by the inverter, _ωe is the electrical angular velocity, which is p times the actual speed _ω0 , and p is the number of pole pairs of the motor;

The second current shape function is:

Among them, i _mf is the reference current amplitude during fault-tolerant operation.

Further, the switching control module includes a first comparator, a second comparator, a third comparator, an OR gate, an integrator and a fourth comparator; the first comparator, the second comparator and the third comparator One input terminal respectively inputs a phase current value, the other terminal inputs a reference current 0 value, the output terminals are respectively connected to one input terminal of the OR gate, the output terminal of the OR gate is connected to the input terminal of the integrator, and the output terminal of the integrator is connected to the fourth comparator The input terminal of the device; when there is a current value of 0 in the three-phase current, the OR gate outputs a trigger signal to trigger the integrator to start working; when the output value of the integrator is greater than the set threshold value, the fourth comparator outputs a fault signal.

A single-phase winding open circuit fault-tolerant control method for an electric vehicle drive system, comprising the following steps:

(1) During normal operation, set the connection mode of the three-phase windings of the three-phase permanent magnet hub motor to star connection;

(2) Measure the actual speed and three-phase current of the motor, pass the actual speed and reference speed through the speed PI regulator to obtain the reference current amplitude during normal operation, and connect the reference current amplitude to the first current corresponding to the star connection mode The shape function is multiplied to obtain the reference value of the three-phase current output by the inverter, and the PWM sequence for controlling the switch of the inverter is output through the hysteresis comparator;

(3) Detect the three-phase current of motor, judge whether there is a single-phase winding open circuit, if open circuit then enters step (4), otherwise enters step (2);

(4) Switch the connection mode of the three-phase winding of the motor to a delta connection;

(5) Measure the actual speed and three-phase current of the motor, pass the actual speed and reference speed through the speed PI regulator to obtain the reference current amplitude during fault-tolerant operation, and compare the reference current amplitude to the second current shape corresponding to the delta connection mode The functions are multiplied to obtain the reference value of the three-phase current output by the inverter, and the hysteresis comparator outputs a PWM sequence to control the switch of the inverter.

Further, the specific method for judging whether there is a single-phase winding open circuit is as follows: when the value of any phase current in the three-phase current is 0 for more than 1/6 current cycle, it is judged that a single-phase winding open circuit fault occurs.

Beneficial effects: when the single-phase winding of the electric vehicle drive system is disconnected, according to the system or method proposed by the present invention, the drive system can output the same torque as that in normal operation, so that the electric vehicle can continue to run, improving the driving efficiency of the electric vehicle. The fault-tolerant operation ability of the system. Compared with the prior art, the present invention applies the delta/star start in the motor starting method to the single-phase winding open circuit fault-tolerant control system of the electric vehicle drive system. Switching the connection mode of the winding to a delta connection through the switch module has the advantage of not increasing the switch tube or the midpoint of the power supply, reducing equipment investment; when any phase winding is disconnected, the three-phase current output by the inverter is the amplitude The same three-phase symmetrical sinusoidal current with a phase difference of 120 degrees, the amplitude rises to that of the current during normal operation times, the torque output is stable; it only needs to detect the fault without judging the specific fault phase, which simplifies the fault detection procedure.

Description of drawings

Fig. 1 is a schematic diagram of the overall structure of the system of the present invention;

Fig. 2 is the PWM generation module structural representation of the present invention;

Fig. 3 is a motor single-phase open circuit fault detection model diagram of the present invention;

Fig. 4 is an equivalent circuit diagram of the drive system inverter and motor of the present invention.

detailed description

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

As shown in Figure 1, a single-phase winding open circuit fault-tolerant system of an electric vehicle drive system disclosed in an embodiment of the present invention includes a PWM generation module 1, an inverter (three-phase half-bridge voltage type) 2, and a three-phase permanent magnet hub motor 3. Switch module 4, switch control module 5 and rotary encoder 6. The PWM generation module 1 includes a rotational speed PI regulator, a current calculation module and a hysteresis comparator. The rotary encoder 6 is connected to the motor 3, collects the rotational speed ω ₀ of the motor rotor, and outputs the rotational speed signal to the PWM generation module 1; the current sampling module 6 is connected to the motor 3, samples the three-phase current of the motor, and outputs the current signal to the PWM generation module 1 for the hysteresis comparator and switching control module 5 . The switch module (which can be realized by solid-state relay or thyristor) 4 is connected to the three-phase winding of the motor 3. There are at least _two sets _of switches S1 and S2. When S1 is closed and S2 is open, the connection mode _of the _three -phase winding is star Type connection, when S ₁ is open and S ₂ is closed, the connection mode of the three-phase winding is a delta connection, as shown in Figure 4. The switching control module 5 is connected to the current calculation module of the current sampling module 6, the switching module 4 and the PWM generation module 1 respectively, and the switching control module 5 determines whether a fault occurs according to the three-phase current sampled by the current sampling module 6. As shown in Figure 3, switching control module 5 comprises three equivalent comparators (comparator 1,2,3), OR gate, integrator and the 4th comparator (comparator F); One input terminal respectively inputs a phase current value, the other terminal inputs a reference current 0 value, the output terminals are respectively connected to one input terminal of the OR gate, the output terminal of the OR gate is connected to the input terminal of the integrator, and the output terminal of the integrator is connected to the fourth comparator When the current value of the three-phase current is 0, the integrator is triggered to start working. When the three-phase current is not 0, the integrator is cleared; the threshold value of the fourth comparator is set to T/6 , T is the current cycle, taking into account the response time and judgment accuracy, when the output value of the integrator is greater than the threshold value, the fourth comparator outputs a fault signal. After the switching control module 5 judges that a single-phase winding open-circuit fault occurs, it sends a switching signal to the switching module 4 and the PWM generating module 1 .

The connection mode of the three-phase windings during normal operation can be set as a star connection. When a single-phase winding fault occurs, the switch module ₄ controls S1 to open and S2 to close, and the connection mode of the _three -phase windings is converted to a delta connection. At the same time, the current calculation module of the PWM generation module 1 switches the current shape function to change the calculation method of the reference value of the three-phase output current of the inverter to adapt to the new connection mode.

The current shape function during normal operation is:

The current shape function during fault-tolerant operation is:

Among them, i _mh and i _mf are the reference current amplitudes during normal and fault-tolerant operation respectively, is the reference value of the three-phase current output by the inverter, ω _e is the electrical angular velocity, which is p times the actual speed ω ₀ , and p is the number of pole pairs of the motor.

As shown in Figure 2, the actual speed ω ₀ (rad/s) of the motor rotor is collected based on the rotary encoder, the difference between the reference speed ω _r and the actual speed ω ₀ is compared, and the difference is input to the input terminal of the speed PI regulator , get the reference current amplitude i _mh (normal), i _mf (fault tolerance).

During normal operation, the switching control module does not output the switching signal. Through the switching module, the winding connection mode of the motor is a star connection (S ₁ is closed, S ₂ is open). According to the reference current amplitude i _mh obtained above and the current shape function (1) Multiply to get the reference value of the three-phase output current of the inverter, through the hysteresis comparator, output the switching signal of the inverter-PWM sequence, the drive system outputs a stable torque, and the electric vehicle runs stably.

When a single-phase winding fault occurs, the switching signal module outputs a switching signal. Through the switching module, the motor winding is connected in a delta connection (S ₁ is open and S ₂ is closed). According to the above obtained reference current amplitude i _mf and current shape Multiply the function (2) to obtain the reference value of the three-phase output current of the inverter. Through the hysteresis comparator, the switching signal of the inverter-PWM sequence is output, so that the drive system maintains the torque output and realizes fault tolerance under the fault state of the electric vehicle. run.

A single-phase winding fault-tolerant method for an electric vehicle drive system disclosed in an embodiment of the present invention includes the following steps:

(1) During normal operation, set the connection mode of the three-phase windings of the three-phase permanent magnet hub motor to star connection;

(2) Measure the actual speed and three-phase current of the motor, pass the actual speed and reference speed through the speed PI regulator to obtain the reference current amplitude during normal operation, and multiply the reference current amplitude with the current shape function (1), Get the reference value of the three-phase current output by the inverter, and output the PWM sequence to control the switch of the inverter through the hysteresis comparator;

(3) Detect the three-phase current of the motor to determine whether there is a single-phase winding open circuit, if there is an open circuit, then enter step (4), otherwise enter step (2); according to the model in Figure 3, the current after sampling is processed, when When the trigger signal is a rising edge, the integrator starts to work, and when the trigger signal falls, the integrator is cleared. When the output value of the integrator is greater than the threshold value, a fault signal is output, and it can be judged that there is a single-phase winding open circuit fault;

(4) Switch the connection mode of the three-phase winding of the motor to a delta connection;

(5) Measure the actual speed and three-phase current of the motor, pass the actual speed and reference speed through the speed PI regulator to obtain the reference current amplitude during fault-tolerant operation, and multiply the reference current amplitude with the current shape function (2), The reference value of the three-phase current output by the inverter is obtained, and the PWM sequence for controlling the switch of the inverter is output through the hysteresis comparator.

In the embodiment of the present invention, the delta/star starting method in the motor starting method is applied to the fault-tolerant control system. The connection mode of the winding is a star connection during normal operation, and the connection mode of the winding is converted into a delta connection through a switch module during fault-tolerant operation. It has the advantage of not increasing the switch tube or the midpoint of the power supply, and reduces equipment investment; when the fault-tolerant operation is performed, the three-phase current output by the inverter is a three-phase symmetrical sinusoidal current with the same amplitude and 120 degrees of phase difference. The current shape function (2) can be applied to the case of open circuit of any phase winding. Compared with the current shape function (1), the initial phase lags by 30°. When performing fault detection, it is only necessary to determine whether a single-phase winding open-circuit fault occurs without determining the location of the open-circuit fault.

It should be pointed out that those skilled in the art can make some improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention. All components that are not specified in this embodiment can be realized by existing technologies.

Claims (4)

1. A single-phase winding fault-tolerant control system for an electric vehicle drive system, characterized in that it comprises: a PWM generation module (1), an inverter (2), a three-phase permanent magnet hub motor (3), a switch module (4 ), switching control module (5), current sampling module (6) and rotary encoder (7); The rotary encoder (7) is connected to the motor (3) for measuring the actual speed of the motor (3), and outputs a speed signal to the PWM generating module (1); The current sampling module (6) is connected to the motor (3), used to measure the three-phase current of the motor (3), and output current signals to the PWM generation module (1) and switching control module (5); The switch module (4) is connected to the three-phase windings of the motor (3), and includes at least two sets of switches, the first set of switches makes the three-phase windings form a star connection, and the second set of switches makes the three-phase windings form Triangular connection; The PWM generating module (1) includes: A rotational speed PI regulator, used to obtain a reference current amplitude according to the difference between the reference rotational speed and the actual rotational speed; The current calculation module is used to calculate the reference of the three-phase current output by the inverter (2) through the first current shape function corresponding to the star connection mode or the second current shape function corresponding to the delta connection mode according to the reference current amplitude value; And, the hysteresis comparator is used to combine the reference value and the actual value of the three-phase current to output a PWM sequence for controlling the switches of the inverter (2); The switching control module (5) is used to judge whether there is a single-phase winding open circuit according to the current signal output by the current sampling module (6), and output a switching signal to the switching module (4) and the PWM generation module (1); During normal operation, the first group of switches is normally open, the second group of switches is normally closed, and the connection mode of the three-phase winding is a star connection. After the switch module (4) receives the switching signal, the second The first group of switches is normally open, the first group of switches is normally closed, and the three-phase windings are connected in a delta connection; The first current shape function is: Among them, i _mh is the reference current amplitude during normal operation, is the reference value of the three-phase current output by the inverter, _ωe is the electrical angular velocity, which is p times the actual speed _ω0 , and p is the number of pole pairs of the motor; The second current shape function is: Among them, i _mf is the reference current amplitude during fault-tolerant operation. 2. The electric vehicle drive system single-phase winding fault-tolerant control system according to claim 1, wherein the switching control module includes a first comparator, a second comparator, a third comparator, an OR gate, an integral One input terminal of the first comparator, the second comparator and the third comparator respectively input a phase current value, the other terminal inputs the reference current 0 value, and the output terminals are respectively connected to one input terminal of the OR gate , the output terminal of the OR gate is connected to the input terminal of the integrator, and the output terminal of the integrator is connected to the input terminal of the fourth comparator; when there is a current value of 0 in the three-phase current, the OR gate outputs a trigger signal to trigger the integrator to start working , when none of the three-phase currents has a 0 value, the integrator is cleared; when the output value of the integrator is greater than the set threshold, the fourth comparator outputs a fault signal. 3. A single-phase winding fault-tolerant control method for electric vehicle drive system, characterized in that, comprising the steps: (1) During normal operation, set the connection mode of the three-phase windings of the three-phase permanent magnet hub motor to star connection; (2) Measure the actual speed and three-phase current of the motor, pass the actual speed and reference speed through the speed PI regulator to obtain the reference current amplitude during normal operation, and connect the reference current amplitude to the first current corresponding to the star connection mode The shape function is multiplied to obtain the reference value of the three-phase current output by the inverter, and the PWM sequence for controlling the switch of the inverter is output through the hysteresis comparator; (3) Detect the three-phase current of motor, judge whether there is a single-phase winding open circuit, if open circuit then enters step (4), otherwise enters step (2); (4) Switch the connection mode of the three-phase winding of the motor to a delta connection; (5) Measure the actual speed and three-phase current of the motor, pass the actual speed and reference speed through the speed PI regulator to obtain the reference current amplitude during fault-tolerant operation, and compare the reference current amplitude to the second current shape corresponding to the delta connection mode The function is multiplied to obtain the reference value of the three-phase current output by the inverter, and the PWM sequence for controlling the switch of the inverter is output through the hysteresis comparator; The first current shape function is: Among them, i _mh is the reference current amplitude during normal operation, is the reference value of the three-phase current output by the inverter, _ωe is the electrical angular velocity, which is p times the actual speed _ω0 , and p is the number of pole pairs of the motor; The second current shape function is: Among them, i _mf is the reference current amplitude during fault-tolerant operation. 4. The single-phase winding open circuit fault-tolerant control method of the electric vehicle drive system according to claim 3, characterized in that, the specific method for judging whether there is a single-phase winding open circuit is: when there is any phase current in the three-phase current If the value is 0 for more than 1/6 current cycle, it is judged that there is a single-phase winding open circuit fault.