JP2000270558A - Dc-voltage setting device for inverter/converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device capable of satisfying voltage required by a load effectively by increasing a DC output voltage of a converter, when a polyphase AC output voltage of an inverter becomes high, in the device consisting of the converter which obtains DC from the polyphase AC and the inverter converting the DC into another polyphase AC. SOLUTION: This inverter/converter consisting of a three-phase voltage converter which converts a three-phase AC into a DC to output it to a DC capacitor, and a three-phase voltage inverter which converts the DC of the DC capacitor into an AC having arbitrary frequency and arbitrary voltage to supply it to a load is provided with a DC voltage setting device 10. A function generator 12 outputs the setting value of a lower limit setting device 14, when an input signal 100 from a speed setting device 1 is less than or equal to the lower limit, whereas the setting value of an upper limit setting device 13 as an output signal 100, when it is higher than or equal to the upper limit. When the value is between the lower and upper limit setting values, the function generator 12 outputs an output signal 101 with a value changing, based on the input signal 100.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in an output voltage utilization factor of an inverter / converter for converting a polyphase alternating current into another polyphase alternating current.

[0002]

2. Description of the Related Art FIG. 4 is a diagram showing a main circuit configuration of a generally used three-phase voltage type inverter / converter. FIG.
, 1 is a three-phase AC power supply, 2 is an AC reactor, 3
Is a three-phase voltage type converter bridge, 4 is a DC capacitor, 5 is a three-phase voltage type inverter bridge, and 6 is a load. 7, a converter control circuit; and 8, an inverter control circuit. In such a configuration, assuming that the DC voltage of the DC capacitor 4 is Ed and the effective value of the fundamental wave component of the output voltage of the three-phase voltage type inverter bridge 5 is Va, in a general sine wave modulation method, the obtained Va is The maximum value Vamax is about Vamax = √ (3/8) × Vd = 0.612 × Vd. It is known that no matter how much the modulation scheme is devised, it does not exceed Vamax = √6 / π × Vd = 0.780 × Vd.

[0003] In an inverter / converter device for driving a fluid device such as a fan / pump, it is not necessary to speed up the response of the output voltage. It was configured to obtain. In addition, transient response is required,
In vector control and the like, in order to shorten the operation time, the modulation method was simplified as much as possible and the rated voltage of the load motor was reduced.

[0004]

However, such a configuration has the following problems. When the rated voltage of the load motor is reduced, the rated current naturally increases accordingly. Since the unit size of the inverter is determined by the magnitude of the output current, it is necessary to use an inverter unit one rank higher, and the external dimensions, weight, and cost increase. Converter 3 shown in FIG. 4 can set its output voltage relatively freely. It can be solved by setting it to a higher value all the time.
In order to apply to a motor rated at 40 V, the DC voltage must be about 719 V or more, which leads to a decrease in overall efficiency and an increase in stress of each part due to the constant application of a high voltage. The present invention has been made in view of the above points, and an object of the present invention is to provide a DC voltage setting device for an inverter / converter that solves these problems.

[0005]

[Means for Solving the Problems] That is, means for achieving the object are as follows: The present invention relates to a converter for obtaining a direct current from a polyphase alternating current and an inverter for converting the direct current to another multiphase alternating current, wherein the multiphase alternating current output voltage of the inverter becomes higher than a predetermined value. A DC voltage setting device for an inverter / converter, comprising: means for increasing a DC output voltage of the converter when the DC / DC converter is turned on.

[0006] 2. In claim 2, as a means for increasing the DC output voltage of the converter, a DC voltage setting device for supplying as an output signal to a converter control circuit for controlling the converter is provided, the DC voltage setting device comprising a function generator and an upper limit value. A value set by the lower limiter if the input signal of the speed setter to the function generator is equal to or less than the value set by the lower limiter, and the upper limiter. If the value is equal to or greater than the value set in, set the value set by the upper limiter.If the value is equal to or greater than the value set in the lower limiter and equal to or less than the value set in the upper limiter, the value that changes according to the input signal of the speed setting device The DC voltage setting device for an inverter / converter according to claim 1, wherein the DC voltage setting device transmits the output signal of the DC voltage setting device to a converter control circuit.

[0007] 3. According to claim 3, a means for determining a setting of a DC output voltage of the converter according to a rotation speed command of the AC motor or an actual rotation speed is provided as a rotation speed sensor instead of the speed setting device of the AC motor. A DC voltage setting device for an inverter / converter according to claim 1 or 2. That is, in the present invention, the DC voltage can be set higher only when necessary. That is, when it is necessary to increase the output voltage of the inverter, the DC voltage may be increased accordingly.
Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing a main part of an embodiment according to claims 1 and 2 of the present invention, FIG. 2 is a characteristic diagram showing an embodiment of the input / output of FIG. 1, and FIG. FIG. 6 is a main part configuration diagram according to claim 3. Hereinafter, a DC voltage setting device for an inverter / converter according to the present invention will be described with reference to FIG.
First, the operation of this main circuit example will be briefly described with reference to FIG.
Converts the energy of the three-phase AC power supply 1 into the AC reactor 2
, And transfer it to the DC capacitor 4 to convert AC to DC. The three-phase voltage type inverter bridge 5 converts the DC of the DC capacitor 4 to an arbitrary frequency
The voltage is converted into alternating current and supplied to the load 6. In such a system, the load 6 is generally an AC motor. Converter control circuit 7 controls the DC voltage of DC capacitor 4 to a predetermined value. The inverter control circuit 8 controls the AC power supplied to the load 6, in the case of a general AC motor,
The rotation speed and the generated torque are controlled to desired values.

Next, in FIG. 1 of the present invention, reference numeral 10 denotes a DC voltage setting device for an inverter converter, and reference numeral 11 denotes a load 6 to be supplied to an inverter control circuit 8 shown in FIG. , 12 is a function generator,
13 is an upper limit value setting device, and 14 is a lower limit value setting device. The output signal 101 of the DC voltage setting device 10 of the inverter / converter is the three-phase voltage type converter bridge 3 shown in FIG.
, And becomes a DC voltage command value of the DC capacitor 4.

FIG. 2 is an input / output characteristic diagram of the function generator 12 according to the embodiment of the present invention shown in FIG. 1. The input signal 100 output from the speed setting value 11 is output from the lower limit value setting device 14 in FIG. If the value is equal to or smaller than the set value, the value set by the lower limit value setting unit 14 is output. Also, the input is the upper limit value setting unit 13 in FIG.
If the value is equal to or greater than the value set in step (1), the value set by the upper limit value setting unit 13 is output. Further, if the value is equal to or more than the value set by the lower limit value setting device 14 and equal to or less than the value set by the upper limit value setting device 13, the output signal 101 changes according to the input signal 100.

That is, if the load 6 shown in FIG. 4 is a general AC motor, if the rotation speed is lower than a predetermined value, the DC voltage of the DC capacitor 4 is set low. If it is higher than the value, the DC voltage of the DC capacitor 4 is set high. If it is intermediate between them, it changes according to the rotation speed.

In FIG. 3, an AC motor speed sensor 15 is used in place of the AC motor speed setting device 11 of the embodiment of the present invention shown in FIG. That is,
The actual speed is used in place of the speed set value of the AC motor, and both perform almost the same operation if the behavior in a very short time is ignored.

[0013]

As described above, according to the present invention, the following effects can be obtained. (1) Since the voltage required by the load can be applied, there is no need to lower the rated voltage of the AC motor or the like. (2) A general standard voltage can be applied to the rated voltage of the AC motor. (3) Since there is no need to lower the rated voltage of the AC motor,
There is no need to increase the frame number of the applicable inverter, and cost performance can be improved. And so on, the effect is enormous.

[Brief description of the drawings]

FIG. 1 is a main part configuration diagram showing an embodiment according to claim 1 or 2 of the present invention.

FIG. 2 is an input / output characteristic diagram of FIG.

FIG. 3 is a main part configuration diagram according to claim 3 of the present invention.

FIG. 4 is a configuration diagram showing one example of the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Three-phase AC power supply 2 AC reactor 3 Three-phase voltage type converter bridge 4 DC capacitor 5 Three-phase voltage type inverter bridge 6 Load 7 Converter control circuit 8 Inverter control circuit 10 DC voltage setting device 11 Speed setting device 12 Function generator 13 Upper limit Value setting device 14 Lower limit value setting device

Claims (3)

[Claims] 1. A converter for obtaining a direct current from a polyphase alternating current,
An inverter / converter device comprising an inverter for converting the direct current into another polyphase alternating current, comprising means for increasing the direct current output voltage of the converter when the multiphase alternating current output voltage of the inverter becomes higher than a predetermined value. A DC voltage setting device for inverters and converters. 2. As a means for increasing the DC output voltage of the converter, a DC voltage setting device for supplying an output signal to a converter control circuit for controlling the converter is provided, the DC voltage setting device comprising a function generator and an upper limit value. A value set by the lower limiter if the input signal of the speed setter to the function generator is equal to or less than the value set by the lower limiter, and the upper limiter. If the value is equal to or greater than the value set in, set the value set by the upper limiter.If the value is equal to or greater than the value set in the lower limiter and equal to or less than the value set in the upper limiter, the value that changes according to the input signal of the speed setting device The DC voltage setting device for an inverter / converter according to claim 1, wherein the DC voltage setting device transmits the output signal of the DC voltage setting device to a converter control circuit. 3. A method according to claim 1, wherein a speed sensor is used in place of the speed setting device of the AC motor, and a means for determining a setting of a DC output voltage of the converter according to a speed command of the AC motor or an actual speed. A DC voltage setting device for an inverter / converter according to claim 1.