JPH04355697A - Motor drive controller for electric automobile - Google Patents

Abstract

PURPOSE:To realize low speed high torque operation without increasing the current capacity of a VVVF power converter and the size of motor and without requiring gear change mechanism. CONSTITUTION:The motor drive controller comprises means 14 for switching the primary winding of a motor 13 between star connection and delta connection and means 17 for controlling the connection switching means 14 to connect the primary winding of the motor 13 in star under low speed traveling whereas to delta connection under high speed traveling. Since the primary winding of the motor 13 is connected in star under low speed traveling, maximum torque current being fed from a power converter 12 becomes higher in the case of star connection than in the case of delta connection.

Description

[Detailed description of the invention]

[Object of the invention]

0002

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor drive control device for an electric vehicle equipped with a three-phase AC motor as a drive source.

0003

2. Description of the Related Art Conventionally, in this type of electric vehicle motor drive control device, as shown in FIG. This is converted into electric power, and is used to drive a three-phase AC motor, for example, a three-phase induction motor 3. The wheels are rotated by this induction motor 3. In this device, a torque command value T* is generated in response to the accelerator pedal depression operation of the automobile, and based on this torque command value T* and the rotational speed ωr of the motor 3, a frequency command generator 4, a voltage command generator 5 , an integrator 6, and a PWM voltage generator 7 to control the inverter main circuit 2, thereby changing the rotational speed of the motor 3. Note that the primary winding of the motor 3 has a delta connection.

0004

[Problems to be Solved by the Invention] However, in the conventional configuration described above, the primary winding of the motor 3 has a delta connection, so the starting current is originally large, and furthermore, in order to meet the high torque requirements at the time of starting and acceleration, In this case, it is necessary to increase the current capacity of the inverter main circuit 2 and also increase the size of the motor 3, and to suppress this, it is necessary to use a gear change mechanism, and in any case, the motor drive control device becomes larger. There were also problems that led to an increase in costs.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an electric vehicle that enables high torque operation at low speeds without increasing the current capacity of the power converter or the size of the motor, and without using a gear change mechanism. To provide motor drive control devices.

[Configuration of the invention]

[0007]

[Means for Solving the Problems] The electric vehicle motor drive control device of the present invention converts DC power from a battery power source into three-phase AC power using a variable voltage variable frequency power converter. A motor drive control device for an electric vehicle that drives a motor and causes wheels to be rotated by the motor, comprising a connection switching means for switching a primary winding of the motor between a star connection and a delta connection; The present invention is characterized in that it is provided with a switching control means for controlling the connection switching means so as to set the connection to a delta connection when traveling at high speed.

[0008]

[Operation] According to the above means, when the motor is running at low speed, by making the primary winding of the motor star-connected, the excitation current becomes 1/α (α is shown in equation 1) compared to the case of delta-connection. . As a result, the maximum torque current that can flow from the power converter becomes larger in the case of star connection. As a result, the high torque requirement during low speed driving can be fully satisfied. In this case, the current flowing through the primary winding is α times as large, so the motor generates a lot of heat, but since the starting acceleration time is short in the driving pattern of the car, this is not a big problem. Additionally, during normal high-speed driving, the delta connection is used, which can suppress heat generated by the motor.

[0009]

[Math 1]

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIGS. 1 to 6. In FIG. 1, a battery power source 11 is connected to an inverter main circuit 12, which is a variable voltage variable frequency power converter consisting of a three-phase inverter bridge. It is adapted to drive a motor 13. A wire connection switch 14 serving as wire connection switching means is connected between the inverter main circuit 12 and the motor 13.
The primary winding No. 3 can be switched between star connection and delta connection. This wiring switch 1
No. 4 has three relay switches controlled by external signals, and when the relay switch is turned on the upper side, it is a delta connection, and when the relay switch is turned on the lower side, it is a star connection.

The motor 13 is provided with a speed detector 15, which outputs a speed signal ωr. Furthermore, when an accelerator pedal (not shown) is depressed, a torque command value T* is generated by a torque command generator (also not shown) according to the amount of depression. This torque command value T* is given to a frequency command generator 16 and a connection selection signal generator 17 serving as a switching control means. As shown in FIG. 2, the frequency command generator 16 includes a slip frequency estimator 18, a frequency converter 19, and an adder 20, and calculates the slip frequency Fsf* according to the torque command value T* and the speed signal ωr. A frequency command value F* is generated by the sum with the proportional frequency conversion value Fr.

The connection selection signal generator 17 has the characteristics as shown in FIG. At speed, a delta connection selection signal Sd is generated, and the switch of the connection changeover 14 is controlled based on this signal. In addition,
As shown in FIG. 3, each of the selection signals Sy and Sd is provided with a hysteresis region H in order to reduce the number of times of switching.

The voltage command value generator 21 is configured to generate a voltage command V* according to the frequency command value F*, and in this case, the delta connection selection signal Sd is selected from among the selection signals Sy and Sd. , α when the delta connection selection signal Sd is given (the value of α is shown in Equation 2)
It is configured to have a double V/F ratio.

[0014]

[Math 2]

The frequency command value F* generated by the frequency command generator 16 is also given to an integrator 22, and the integrator 22 integrates the frequency command value F* to obtain a phase angle command value θ. * is generated. PWM voltage generator 2
3, a PWM voltage is generated based on this phase angle command value θ* and the voltage command value V*, and the inverter main circuit 1
Drive control of the second power transistor.

FIG. 4 shows the relationship between voltage and frequency in V/F control. In the figure, Vmax is the maximum voltage value that can be output from the inverter main circuit 12, and in delta connection, constant magnetic flux control is applied. The maximum possible frequency is indicated by FΔ, and the maximum frequency at which the magnetic flux can be controlled to be constant during star connection is indicated by Fy. This maximum frequency Fy is FΔ/α since the V/F ratio is multiplied by α.

FIG. 5 shows the current vector, im
Δ is the excitation current in delta connection, itΔ is the torque current in delta connection, imax is the maximum current value that the inverter main circuit 12 can output, imy is the excitation current in star connection, i
ty is the torque current in star connection, iΔ is the inverter output current in delta connection, and iy is the inverter output current in star connection.

Now, when the automobile is started or at low speed, the connection selection signal generator 17 outputs the star connection selection signal Sy, which turns the relay switch of the connection changer 14 to the lower side, and the motor 13 is switched on. The primary winding is star connected.

Therefore, in star connection, the motor impedance is three times that of delta connection, and the current ratio is 1:3.
Also, when looking at the phase current, in star connection, the output current from the inverter main circuit 12 flows directly to each phase winding of the motor 13, but in delta connection, the output current from the inverter main circuit 12 flows 1/α times. current flows. Therefore, in star connection, the excitation current flowing from the inverter main circuit 12 is 1/α of that in delta connection, so as shown in FIG. 5, the excitation current imy in star connection is equal to the excitation current in delta connection. 1/ of imΔ
becomes α. As a result, the maximum torque current it y that can flow from the inverter main circuit 12 during star connection becomes larger than the maximum torque current it Δ that can flow from the inverter main circuit 12 during delta connection.

For example, considering the case where itΔ=imΔ, ity and itΔ have the relationship shown in equation 3.

[0021]

[Math 3]

Therefore, the torque T generated during delta connection
Δ is β times (
The value of β is shown in equation 4).

[0023]

[Math 4]

However, if motor loss etc. are taken into consideration, the amount will be slightly less than this. Furthermore, the current flowing through the winding at this time is α times as large as that in the case of delta connection, so the motor generates a large amount of heat, and the current can only flow for a short time compared to the case of delta connection. However, when driving a car, the starting acceleration time is short and there is no problem in practice. Here, in order to avoid saturation of the magnetic circuit inside the motor, it is sufficient to make the excitation current flowing through each phase winding of the motor equal between both connections. It should be α times the time. In this embodiment, the voltage command generator 21 sets the V/F ratio to α times that of delta connection during star connection, so saturation of the magnetic circuit can be prevented.

On the other hand, when driving at high speed, the connection selection signal generator 17 outputs the star connection selection signal Sd, which turns the relay switch of the connection changer 14 upward, and the primary winding of the motor 13 is connected to the delta connection. It is said that If the star connection is maintained even when driving at high speeds, as mentioned above, the current flowing through the motor windings will be α times that of the delta connection, so the motor will generate more heat, but when driving at high speeds, Since delta connection is used, this problem does not occur.

Although the above embodiment has been described using a voltage control type inverter, a current control type inverter may also be used as in the second embodiment shown in FIG. In this case, the current controller 24 performs vector control in which torque current and excitation current are controlled, and when a star connection selection signal Sy is given, the excitation current command value is changed to a delta connection selection signal Sd. It is controlled to be 1/α of the case. As a result, saturation of the motor magnetic circuit can be eliminated.

[0027]

Effects of the Invention As is clear from the above description, the present invention has the primary winding of the motor star-connected when running at low speeds and delta-connected when running at high speeds. This has the excellent effect of enabling high torque operation at low speeds without increasing the current capacity of the power converter or the size of the motor, and without using a gear change mechanism.

[Brief explanation of drawings]

FIG. 1 is an electric circuit diagram showing a first embodiment of the present invention.

[Figure 2
]Block diagram of frequency command generator

[Figure 3] Diagram showing the relationship between speed signals, torque command values, and connection switching states

[Figure 4] Diagram showing the relationship between the V/F ratio and the connection switching state

[Figure 5] Current vector diagram

FIG. 6 is a diagram corresponding to FIG. 1 showing a second embodiment of the present invention.

[Figure 7
】Equivalent to Figure 1 showing a conventional example

[Explanation of symbols]

11 is a battery power supply, 12 is an inverter main circuit (power converter), 13 is a three-phase induction motor (three-phase AC motor),
Reference numeral 14 indicates a connection switch (connection switching means), and 17 indicates a connection selection signal generator (switching control means).

Claims (1)

[Claims] [Claim 1] A three-phase AC motor is driven by converting DC power from a battery power source into three-phase AC power using a variable voltage variable frequency power converter, and this motor rotates the wheels. In a motor drive control device for an electric vehicle, a connection switching means for switching a primary winding of the motor between a star connection and a delta connection;
1. A motor drive control device for an electric vehicle, comprising a switching control means for controlling the connection switching means so that the connection is set to star connection when running at low speed and to set to delta connection when running at high speed.