JPH0528957Y2 - - Google Patents

Description

[Detailed description of the invention] [Purpose of the invention] (Technical field of the invention) The present invention relates to the control of a power supply device that drives a synchronous motor, and in particular, a power supply device for driving a synchronous motor for stably driving a synchronous motor. Regarding the improvement of

(Prior Art) Inverters and cycloconverters using semiconductor elements have been frequently used in recent years as power sources for driving synchronous motors. Synchronous motors are prone to power disturbances due to their characteristics during steady operation. A hysteresis motor, which is a type of synchronous motor, uses a magnetic material for its rotor, and can generate torque and operate regardless of whether it is synchronous or asynchronous. During synchronous operation, power disturbances occur as with general synchronous motors. As a method for suppressing this disturbance, there is a method of controlling the voltage or frequency supplied to the hysteresis motor by detecting changes in the input power of the hysteresis motor or the direct current or input current of the inverter.

FIG. 3 is a block diagram showing a conventional method for suppressing power disturbance in a hysteresis motor. FIG. 3 shows a hysteresis motor 1, a rectifier 2 that converts AC input power into DC, and a DC filter circuit 3 consisting of a DC reactor and a capacitor.
The main circuit is composed of an inverse converter 4 that converts direct current to an arbitrary frequency. The control circuit includes a reference generation circuit 10 that generates a reference signal A for the voltage and frequency of the power supply, and a reference frequency B that determines the output frequency of the inverter 4 based on the reference signal A.
an F converter 11, a ring counter 12 that distributes a firing signal of the reference frequency B to the switching elements of the inverter 4 in a predetermined order;
A pulse amplification circuit 13 amplifies the output of the rectifier 2 and applies an ignition signal C to the switching element, and a current transformer 14 detects and rectifies the input current of the rectifier 2 and converts it into a DC signal D. , a differentiating circuit 15 that differentiates the amount of change, and an error amplifying circuit 16 that amplifies the error signal between the output signal E of the differentiating circuit 15, the reference signal A, and the signal F that is fed back by detecting the terminal voltage of the motor 1. and a phase shifter 17. FIG. 4 is a time chart showing the state of suppression of power disturbance, and shows the input power PM to the motor 1, the signal D detecting the input current of the power supply device, and the output signal E of the differentiating circuit 15. FIG. 4 shows that when signal E is applied to the motor 1 in a state where power disturbance is occurring, the power increases, the input current of the power supply increases, and the control signal E acts in the direction of lowering the DC voltage. Conversely, when the power decreases and the input current of the power supply device decreases, the control signal E operates in the direction of increasing the DC voltage to control the input power to the motor 1 and suppress disturbance. .

(Problems to be Solved by the Invention) This control method is very effective when accelerating the electric motor or operating at low speed, but when decelerating the electric motor 1 or operating at low speed, large power disturbances occur. When regenerated to the power source side, the current of the input power source is clipped to zero, so there is no effect of suppressing power disturbance at all, and power disturbance in the regenerative state is promoted in the control direction. That is, hysteresis motor 1
When the regenerated power returns, the DC voltage shown in FIG. 3 increases, so the rectifier 2 is controlled to lower the DC voltage, and as a result, the input current of the rectifier 2 decreases. When this input current decreases, the control signal E operates in the direction of increasing the DC voltage as described above. Electric motor 1 decelerating like this
The power disturbance becomes increasingly large, which may cause problems in the operation of the electric motor 1.

This invention was made in view of the above points,
The present invention provides a power supply device for driving a synchronous motor, which performs control to suppress power disturbance even during power regeneration of the synchronous motor, and is capable of stable operation.

[Structure of the invention] (Means and effects for solving the problem) In order to achieve this objective, the present invention installs a detector at a position where the polarity of the disturbance suppression signal is reversed during operation in a power regeneration state. By providing this, power disturbances are suppressed.

(Example) An embodiment of the present invention will be described below.

1 is a control block diagram showing an embodiment of the present invention. The same reference numerals as those in FIG. 3 denote the same elements.

The difference from FIG. 3 is that a current transformer 14 is provided after the DC filter circuit 3 as a power disturbance detection circuit.

When power disturbance occurs, the polarity of the average value of the DC current flowing to the current transformer 14 is reversed from (+) to (-) when it enters a regenerative state. The amount of change E in this signal is input to a power disturbance control circuit, for example, a point G of a voltage control circuit or a point H of a frequency control circuit. With the increase in the amount of change, the voltage control method controls the DC voltage in the direction of lowering, and the frequency control method controls the frequency in the direction of lowering.

FIG. 2 is a time chart showing the control signals when the power is out of order and the regeneration state is entered. The input power PM to the motor 1, the signal D detecting the DC current of the power supply device, and the output of the differentiating circuit 15 are shown in FIG. This is signal E.
A state in which the input power PM is on the (-) side indicates a state in which power is returned from the electric motor to the power supply device in the regeneration mode.

[Effects of the invention] As explained above, according to the invention, when power disturbance occurs in a synchronous motor, the polarity of the signal for suppressing power disturbance is made bipolar, so disturbances during power regeneration can also be suppressed, and furthermore, power disturbance can be suppressed. Since the current flow device 14 also serves as a DC short circuit detection circuit, it is possible to provide a power supply device for driving a synchronous motor that can realize economical and stable control.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an embodiment of the power supply device for driving a synchronous motor of the present invention, Fig. 2 is a time chart for explaining the operation of Fig. 1, and Fig. 3 is a conventional synchronous motor drive power supply device. FIG. 4 is a block diagram showing the power supply device for use in the present invention, and is a time chart for explaining the operation of FIG. 3. DESCRIPTION OF SYMBOLS 1... Synchronous motor, 2... Rectifier, 3... DC filter circuit, 4... Inverse converter, 10... Reference signal generator, 11... V-F converter, 12... Ring counter, 13... ...Pulse amplification circuit, 14...
Current transformer, 15... Differential circuit, 16... Error amplifier circuit, 17... Phase shifter.

Claims (1)

[Scope of utility model registration request] Consisting of a rectifier that converts alternating current to direct current, a direct current filter circuit equipped with a direct current capacitor provided in the direct current output circuit of the rectifier, and an inverse converter that converts the direct current supplied via the direct current filter circuit to alternating current. In a power supply device for driving a synchronous motor, which includes a variable voltage variable frequency power supply device and a synchronous motor driven by the power supply device, a signal having a polarity corresponding to a current direction provided at a downstream stage of the DC filter circuit is output. It comprises a current detector and a differentiation circuit that differentiates the output of the current detector, and applies the output of the differentiation circuit as a disturbance suppression signal to a voltage control system or a frequency control system that controls the variable voltage variable frequency power supply device. A power supply device for driving a synchronous motor, characterized in that the current detector also serves as a DC short circuit detector.