JPH0799885B2 - Variable speed controller for synchronous motor - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a variable speed control device for a synchronous motor, and more specifically,
For example, the present invention relates to a variable speed control device for a synchronous motor, which efficiently controls a variable speed of a permanent magnet type synchronous motor used for a vehicle.

[Technical Background of the Invention and Problems Thereof] For example, a permanent magnet synchronous motor used in a vehicle converts a DC voltage from a vehicle battery into an AC voltage by an inverter circuit and is driven by the AC voltage. Variable voltage variable frequency control is performed to variably control the frequency and voltage of the AC voltage supplied to the electric motor in order to perform variable speed control of the electric motor with good response characteristics and high efficiency. FIG. 7 is a block diagram of a conventional variable speed control device for a synchronous motor that employs such a control system.

In FIG. 7, the DC voltage of the vehicle-mounted battery 1 is converted into an AC voltage by the inverter 2, and the synchronous motor 3 is driven by the AC voltage. The synchronous motor 3 is used, for example, for a vehicle, and for example, a variable speed command signal A supplied from a variable speed command device 5 including an accelerator or the like.
In this case, the rotation speed signal ω from the rotation speed sensor 4 for detecting the rotation speed of the synchronous motor 3 is fed back, and the drive control is performed in consideration of this rotation speed signal ω. There is. That is, the variable speed command signal A from the variable speed command device 5 is supplied to the function generator 6 which outputs a coefficient A ′ proportional to the variable speed command signal A, and the rotation speed signal from the rotation speed sensor 4 is supplied. ω is the input voltage / which depends on this rotation speed signal ω
The rotation speed coefficient (hereinafter abbreviated as V / F), that is, the coefficient γ, is supplied to the V / F generator 7. And
The coefficient A ′ from the function generator 6 is multiplied by the coefficient γ from the V / F generator 7 by the multiplier 8 to calculate the applied command voltage ||, which is the three-phase sine wave generator. 9 is being supplied. The three-phase sine wave generator 9 is also supplied with the rotation speed signal ω from the rotation speed sensor 4, and the three-phase sine wave generator 9 receives the three-phase sine wave generator 9 according to the applied command voltage || and the rotation speed signal ω. Outputs a phase sine wave signal. This three-phase sine wave signal is supplied to one input of each of the comparators 11, 12 and 13 and is compared in amplitude with the triangular wave signal from the carrier triangular wave generator 10 supplied to the other input. As a result, the three-phase sine wave signals are pulse-width modulated and supplied to the inverter 2, whereby the DC voltage of the battery 1 is converted into a three-phase AC voltage, and the synchronous motor 3 is drive-controlled.

In such control, V / F is controlled to be constant so that the generated torque is constant, and the input voltage is varied in proportion to the rotation speed of the synchronous motor 3. Therefore, there is a problem that the synchronous motor does not always operate at the operating point where the efficiency of the synchronous motor is maximum with respect to each torque value at each rotational speed, and the overall efficiency deteriorates. Further, when operating with deteriorated efficiency, the input current becomes excessively large, and the heat generation thereof causes the dielectric breakdown of the winding of the electric motor, and the output decreases.

[Object of the Invention] The present invention has been made in view of the above, and an object of the present invention is to perform a variable speed control of a synchronous motor in which the synchronous motor is efficiently operated to improve reliability and efficiency. To provide a device.

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention generates an AC input signal to be supplied to a motor based on a command signal from a rotation speed command means and a rotation speed signal of a synchronous motor, and the AC input. In a variable speed control device for a synchronous motor that drives and controls a motor by a signal, an input current / input voltage detection means for detecting an input current and an input voltage supplied to the motor, and a detected input current and an input voltage, respectively. An increasing / decreasing tendency detecting means for detecting whether there is an increasing tendency or a decreasing tendency, and a correction command for decreasing the AC input signal when both the detected input current and input voltage have an increasing tendency or a decreasing tendency. , Increasing the AC input signal when one of the detected input current and input voltage is increasing and the other is decreasing And a correction unit that generates a correction command.

Embodiments of the Invention Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a variable speed controller for a synchronous motor according to an embodiment of the present invention. The variable speed control device for a synchronous motor shown in the figure is for controlling the drive of a synchronous motor used for a vehicle, for example, but the configuration of each element indicated by reference numeral 1-13 is the same as the configuration of FIG. , An input current detector 14 connected to the input side of the inverter 2 to newly detect the input current to the synchronous motor 3 in this configuration,
An input voltage detector 15 connected to the output of the inverter 2 to detect the input voltage to the synchronous motor 3, and an input current detector.
Differentiating circuits 16a and 16b respectively connected to 14 and the input voltage detector 15 and an input voltage correction coefficient generator 17 connected to the outputs of the differentiating circuits 16a and 16b are added.

Each of the differentiating circuits 16a and 16b is composed of a normal differentiating circuit including a capacitor C and a resistor R as shown in FIG. Differentiating circuits 16a and 16b are input current detectors 14
Also, the input current and the input voltage from the input voltage detector 15 are differentiated to detect whether the input current and the input voltage tend to increase or decrease. When the output voltage of each differentiating circuit is positive, the corresponding input signal tends to increase, while when it is negative, the corresponding input signal tends to decrease.

The input voltage correction coefficient generator 17 is composed of, for example, a ROM memory R
Using the OM package, describe the input voltage correction coefficient α in the table format with the input voltage and input current input through the differentiating circuits 16a and 16b as parameters, and read the input voltage correction coefficient α according to the input signal. However, the circuit configuration shown in FIG. 3 will be described as an example.

The input voltage correction coefficient generator 17 shown in FIG. 3 receives the input current 1 and the input voltage V from the input current detector 14 and the input voltage detector 15 at the comparators 18a and 18b through the differentiating circuits 16a and 16b, respectively. , Each of which is compared with a reference voltage of 0 volt. The outputs of the comparators 18a and 18b are supplied to the exclusive OR circuit 19, and the output of the exclusive OR circuit 19 is supplied to the voltage increase / decrease coefficient generator 20. Comparator 18
The a and 18b compare the differential output from the differentiating circuits 16a and 16b with a reference voltage of 0 volt, and convert them into normal positive and negative level logic signals. The exclusive OR circuit 19 takes the exclusive OR of both the input signals converted to the normal logical level, that is, the logical signal showing the increasing / decreasing tendency of the input current and the logical signal showing the increasing / decreasing tendency of the input voltage, and The output signal K is output as a positive / negative signal. The following table shows this relationship.

That is, the output signal K of the exclusive OR circuit 19 is negative when both inputs have the same sign, and positive when the inputs have different signs.
The voltage increase / decrease coefficient generator 20 adds 1 to this signal K (1+
K). Therefore, as shown in the table, the output (1 + K) of the voltage increase / decrease coefficient generator 20 is smaller than 1 (<1) when both differential signals are positive or negative, and is larger than 1 when one is positive and the other is negative. (1>).

The output of the voltage increase / decrease coefficient generator 20, that is, the output of the input voltage correction coefficient generator 17 is supplied to the multiplier 8 shown in FIG. 1, whereby the output coefficient A from the function generator 6 is multiplied in the multiplier 8. ′ And the output coefficient γ from the V / F generator 7, which is a product of the applied command voltage ||
The applied command voltage || is increased or decreased by multiplying the output of 20 (1 + K). As a result, as shown in the table, when both differential signals are positive or negative and are the same, that is, when both the input current and the input voltage tend to increase or decrease, the applied command voltage || is decreased, and one is positive and the other is In the negative case, that is, either the input current or the input voltage tends to increase,
If the other is decreasing, the applied command voltage || is increased.

By the way, when the rotation speed N ₀ of the synchronous motor 3 is constant, V /
In the conventional method of controlling F to be constant, the torque-DC input current characteristic becomes the characteristic of the curve as shown in FIG. In addition,
In this characteristic, the input voltage is V ₀ (v). Here, when varying the current input voltage range of V1 <V ₀ <V2,
Torque-input voltage characteristics are shown in Fig. 5 for each voltage V1, V
It changes as shown by curves a, b, and c for ₀ and V2, respectively. That is, it is understood that there is a point that the input voltage with respect to the torque T can be considerably reduced by changing the input voltage with respect to the torque T as V1, V ₀ , V _{2 at} the same rotation speed N ₀ . In other words, if the input voltage V ₀ is fixed and controlled so that V / F is constant as in the conventional case, the input current decreases when the torque T changes from 0 to tp as shown in FIG. When the torque T changes from tp to tm, the input current increases and the efficiency deteriorates. On the other hand, by changing the input voltage as shown in Fig. 5, the torque at this time-
By using the envelope curve ABCD of the input current minimum point of the input current characteristic, the armature current of the permanent magnet type synchronous motor 3 can be minimized, which can prevent heat generation and improve efficiency. is there.

Next, in the characteristic of the constant rotation speed N ₀ shown in FIG. 5, for example, when the torque tp is constant, the input current is plotted against the input voltage, as shown in FIG. As can be seen from FIG. 6, the torque is constant when the rotation speed N ₀ is constant.
When tp is constant, the input voltage that minimizes the input current is only one point, V ₀ . Therefore, the input current can be minimized by controlling the input voltage to this value.

Then, as described above, the increasing / decreasing trends of the input current and the input voltage obtained in the differentiating circuits 16a, 16b are made to correspond to the arrows 31, 33, 35, 37 shown along the curve of FIG. The input voltage correction coefficient generator 17 is operating to obtain the input voltage V ₀ that minimizes the input current.

Next, the operation will be described.

The applied command voltage || is output by multiplication in the multiplier 8 based on the coefficient A ′ for the variable speed command signal A from the variable speed command device 5 and the coefficient γ for the rotation speed signal ω from the rotation speed sensor 4, and this applied command voltage || The voltage || and the rotation speed signal ω are supplied to the three-phase sine wave generator 9.
The amplitude of the three-phase sine wave signal from the three-phase sine wave generator 9 is compared with that of the triangular wave signal from the triangular wave generator 10 in the comparators 11, 12 and 13, and the pulse width is modulated to be supplied to the inverter 2. Is converted into a three-phase AC signal to drive the synchronous motor 3.

In this case, the input current supplied to the synchronous motor 3 is detected by the input current detector 14, and the input voltage is detected by the input voltage detector 15. The detected input currents and voltages are differentiated by the differentiating circuits 16a and 16b, respectively, and their increasing / decreasing tendency is determined.

Now, assuming that both the input current and the input voltage are increasing, this is the case where the input voltage is increasing from V ₀ to V _{2 as} shown by the arrow 31 in FIG. As shown in the table, dt / dI = positive, dv / dt = positive, and K
= Since it is negative, 1 + K <1. Therefore, in this case, the negative input voltage correction coefficient α is equal to the applied command voltage |
The input voltage V, that is, the applied command voltage || is multiplied by |, and is controlled to become V ₀ . As a result, the input current is also controlled to be the minimum value.

Next, when the input current increases and the input voltage decreases, it is the case where the input voltage changes from V ₀ to V ₁ as shown by the arrow 33 in FIG. As shown in the above display, dt / dI = positive, dv / dt = negative, and K = positive, so 1 + K> 1. Therefore, in this case, the positive input voltage correction coefficient α is multiplied by the applied command voltage ||, and the input voltage V, that is, the applied command voltage || is increased and controlled to V _0. . As a result, the input current is controlled to have the minimum value.

Further, the case where the input current is decreasing and the input voltage is increasing is the case indicated by the arrow 35 in FIG. 6, and in this case, similarly, as can be seen from the above table, the input voltage should be V _0. Increased control, resulting in a minimum input current.

Similarly, the case where the input current is decreasing and the input voltage is decreasing is the case indicated by the arrow 37 shown in FIG. 6, and the input voltage is controlled to decrease to V ₀ as shown in the previous table. ,
The input current is controlled to be the minimum.

Although a direct current is used as the input current in the above embodiment, it can be similarly performed with an alternating current, and in this case, it is conceivable to detect an effective value, a peak value, or the like. The input voltage is not limited to direct current, and may be alternating current. Use input power instead of input current,
Of course, the input voltage may be controlled so that the power is minimized.

[Advantages of the Invention] As described above, according to the present invention, when the input current and the input voltage supplied to the electric motor are respectively detected and the input current and the input voltage are both increasing or decreasing, Since the AC input signal of the synchronous motor is decreased and one of the detected input current and the input voltage has an increasing tendency and the other has a decreasing tendency, the AC input signal is increased so that the correction is performed. The input current of the synchronous motor can be minimized not only during steady operation but also during acceleration / deceleration, and efficient operation can be achieved. Further, since the current can be suppressed to the minimum for the same output of the synchronous motor, the current is prevented from becoming excessive, the insulation breakdown of the winding of the synchronous motor is prevented, and the output reduction is also prevented. Moreover, the efficiency of the entire synchronous motor can be improved.

[Brief description of drawings]

1 is a block diagram of a variable speed control device for a synchronous motor according to an embodiment of the present invention, FIG. 2 is a circuit diagram of a differentiating circuit used in the device of FIG. 1, and FIG. 3 is a circuit diagram of FIG. 4 is a circuit diagram of an input voltage correction coefficient generator used in the apparatus, and FIGS. 4 to 6 are torque-input voltage characteristic diagrams and input voltage-input current characteristic diagrams for explaining the operation of the apparatus of FIG. 1, respectively. FIG. 7 is a block diagram of a conventional variable speed control device for a synchronous motor. 1 ... Battery, 2 ... Inverter 3 ... Synchronous motor, 4 ... Rotation speed sensor 5 ... Variable speed commander, 14 ... Input current detector 15 ... Input voltage detector 16a, 16b ... Differentiation circuit 17 …… Input voltage correction coefficient generator

Claims (1)

[Claims] 1. A synchronous motor capable of generating an AC input signal to be supplied to the electric motor based on a command signal from a rotational speed command means and a rotational speed signal of the synchronous motor, and driving and controlling the electric motor by the AC input signal. In the shift control device, input current / input voltage detection means for detecting the input current and input voltage supplied to the electric motor, and whether the detected input current and input voltage tend to increase or decrease, respectively. An increasing / decreasing trend detecting means for detecting the above, and a correction command for decreasing the AC input signal when the detected input current and input voltage are both increasing or decreasing, Correction means for generating a correction command for increasing the AC input signal when one is increasing and the other is decreasing. A variable speed control device for a synchronous motor characterized by being provided.