JPS63117665A - Dc bus type ac variable speed apparatus - Google Patents

Abstract

PURPOSE:To stabilize a control operation of a DC bus type AC variable speed apparatus by measuring the amplitude of a starting current at the time of rising the apparatus and the rising time of a DC voltage to calculate the smoothing condenser value of a load, and regulating the gain of a voltage controller in response to the value. CONSTITUTION:A DC power is supplied through a DC power source 2 for obtaining a constant DC voltage from a 3.phase AC power source 1, a reactor 3, smoothing condensers 4-1-4-n to voltage type inverters 5-1-5-n, converted to an AC of variable voltage and variable frequency to drive induction motors IM. In this case, a comparator 11 for detecting the rise up to a rated DC voltage, a DC current detector 12, an integrator 13, a gain regulator 14 and a voltage controller 15 are provided, and the gain of the controller 15 is regulated to a gain reversely proportional to the output of the integrator. Thus, an optimum voltage control state is held irrespective of a load condition to be able to perform a stable control operation.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a DC bus type AC variable speed control system for variable speed control of a plurality of AC motors each connected to a common DC bus via an inverter device. It is related to the device.

[Conventional technology]

FIG. 3 is an electric circuit diagram showing an example of a conventional DC bus type AC variable speed device, as shown in, for example, "Inverter Application Manual" published by Denki Shoin, page 58 (published September 7, 1985). In the figure, 1 is a three-phase AC power supply, 2
is a DC power supply device for obtaining constant DC voltage, 3 is a glue handle for suppressing rush current, 4-1.4-2,...4-n
are smoothing capacitors, 5-1.5-2, . . . 5-n are voltage source inverter devices, and the voltage source inverter devices 5-1.5-2. . . , 5-n receives DC power from the common DC power supply 2 and supplies variable voltage, variable frequency AC power to the induction motors IM provided respectively. 6-1, 6-2,..., 6-n
are voltage source inverter devices 5-1, 5-2, . . .

5-n, a breaker for disconnecting the load side from the DC power supply device 2 when performing maintenance on the induction motor IM or the mechanical device rotation. 7 is a DC voltage detector, 8 is a DC voltage setter, and 9 is a voltage controller.The gain of this voltage controller 9 maintains the output voltage constant during normal operation, and also maintains the output voltage during transients such as load fluctuations. The gain is selected to be as high as possible so that there is little variation. 10 is a thyristor ignition device.

Next, the operation will be explained.

Normally, AC power from a three-phase AC power supply 1 is converted into DC power by a source device 2, and smoothing capacitors 4-1, 4-2.・・・
・, 4-n smooth this DC current, and then it is inversely converted into variable voltage, variable frequency AC power by voltage source inverter devices 5-1, 5-2, . . . , 5-n. Electric power is supplied to an individually provided induction motor IM to drive it. Therefore, the DC voltage detector 7 is connected to the DC power supply device 2.
The output voltage Vdc is detected, compared with the voltage command value Vs set by the DC voltage setter 8, and inputted to the voltage controller 9. This voltage controller 9 controls the thyristor ignition device 10 so that the DC voltage Vdc becomes equal to the voltage command value Vs.

[Problem that the invention seeks to solve]

Since the conventional DC bus type AC variable speed device is configured as described above, the voltage source inverter device 5-1
．． 5-2, ..., 5-n, for reasons such as maintenance of the induction motor IM-i or mechanical device rotation, some of the voltage type inverter devices 5-1, 5-2, ... 25-n, for example, breaker 6-1.6-2 of 1/2 of the total capacity.
, . . . , 6-n is opened, the load condition as seen from the converter side changes. In other words, since the capacitance of the smoothing capacitors 4-1, 4-2, .
What was set to the υ optimum response by the voltage controller 9 is
Transient vibration (hunting) will occur due to the gain being too high. For this reason, in conventional DC bus-type AC variable speed devices, the response performance must be adjusted to low response performance in advance without making optimal adjustments to minimize voltage fluctuations, or the breaker 6-1.6
-2, . . . , 6-n There was a problem in that gain adjustment had to be performed each time the disconnection was performed.

This invention was made to solve the above-mentioned problems, and it maintains the optimum voltage control state at all times regardless of the load side conditions, provides DC voltage with small voltage fluctuations, and provides stable control operation. The purpose of this invention is to obtain a DC bus-type AC variable speed device that makes possible the following.

[Failure to solve the problem]

The DC bus-type AC variable speed device according to the present invention includes a current detector that detects a starting current value and integrates the current value detected by the current detector by the rise time of the DC voltage when starting up the DC power supply. Gain of an integrator and a voltage controller that calculates the value of the smoothing capacitor of the load connected to the DC bus using the output of this integrator and outputs a control signal to the DC power supply unit according to the smoothing capacitor tray. It is designed to adjust.

[For production]

In the DC bus type AC variable speed device of this invention,
By measuring the magnitude of the starting current value and the rise time of the DC voltage when starting up the equipment, the value of the smoothing capacitor of the load connected to the DC bus is calculated from these measured values, and the value of the smoothing capacitor of the load connected to the DC bus is calculated. The gain is adjusted.

〔Example〕

An embodiment of the present invention will now be described with reference to the drawings. 1st
The figure is an electric circuit diagram showing a DC bus-type AC variable speed device as an embodiment of the present invention, and the same components in FIG. 1 as in FIG. . In the figure, 11 is a comparator device that detects a rise to the rated DC voltage Vdc, and 12 is a DC power supply device 2.
13 is an integrator, and this integrator 13 converts the output current value of the current detection device 12 into the time T from when the comparator device 11 is started until a stable DC voltage is obtained. It is used to integrate only . 14 is a gain adjuster, 15 is a voltage controller, and this voltage controller 15
The gain of the integrator 1 is determined by the gain adjuster 14.
The gain is adjusted to be inversely proportional to the output of 3.

Next, the operation will be explained with reference to FIG. When turning on the power, use the voltage source inverter device 5-1.5-2.
,..., 5-n are all stopped, so the DC current Idc is all smoothed capacitor as shown in Fig. 2(a)?
The charging current is 4-1.4-2, . . . , 4-n.

Therefore, if the charging current is approximately constant, Figure 2 (
As shown in b), the DC voltage Vdc increases at a substantially constant rate. Suppose 1 smoothing capacitor 4-1.4-2,...
If the capacitance of 4-n is small, the voltage rises quickly as shown by the broken line. The output of the comparator device 11 that detects the voltage increase until a stable DC voltage vdC is obtained is shown in FIG. 2(C). The time T until the voltage rises is approximately equal to the smoothing capacitor 4-
1.4-2. Since it is proportional to the capacitance of 4-n, smoothing capacitor 4-1.4-2, . . .
・.

It is possible to estimate the capacity of 4-n, but in order to obtain sufficient accuracy even if the charging current value fluctuates or has a tendency to hunt,
As shown in FIG. 2(d), if the value obtained by integrating the value of the DC current Idc by the integrator 13 for the time T is used, the smoothing capacitor 4-1 is completely smoothed.

4-2. ..., it is possible to obtain an output proportional to the capacitance of 4-n. If the output of the integrator 13 is input to the gain adjuster 14 to make the gain of the voltage controller 15 inversely proportional to the output of the integrator 13, the control gain for controlling the DC voltage Vdc will be equal to the smoothing capacitor +4. -1.4-2, □
Since it is constant regardless of the capacity iK of - and 4-n, the DC voltage Vdc can always be controlled in an optimal state.

In the above embodiment, an example was shown in which DC current was detected on the DC side, but detection on the AC power supply side may also be used. In addition, although the current detector 12 was explained as being added in the above embodiment, it is generally included in the control circuit for the purpose of protecting internal components from overcurrent in the DC power supply device 2, and the comparator device is also included in the control circuit. 11, the integrator 13, the gain adjuster 14, etc., can be implemented using a digital control system with almost no increase in equipment cost. Here, the DC power supply 2 includes an anti-parallel thyristor converter,
Voltage type inverter device 5-1. 5-2°...+5
Although an example in which a transistor is used as the conversion element has been described, the same effect as in the above embodiment can be obtained even if a GTO or other element is used as the conversion element.

〔Effect of the invention〕

As described above, according to the present invention, the output current value of the current detector is set to a predetermined value from the start of the comparator device so that the DC bus-type AC variable speed device is in an optimal control state regardless of the presence or absence of a load. It is equipped with a voltage controller that integrates the time it takes to obtain a stable DC voltage value and adjusts the gain according to the output, so it is a DC constant voltage power supply with little voltage fluctuation and no transient vibration. There is an effect that can be obtained.

[Brief explanation of the drawing]

Fig. 1 is an electric circuit diagram showing a DC bus type AC variable speed device according to one embodiment of the present invention, Fig. 2 is an explanatory diagram of the operation of the embodiment shown in Fig. 1, and Fig. 3 is a conventional DC bus type AC variable speed device. FIG. 2 is an electrical circuit diagram showing an AC variable speed device according to the present invention. In the figure, 2 is a DC power supply device, 5-1.5-2.5-
n is a voltage source inverter device, 9 is a voltage controller, 11 is a voltage rise time detection comparator, 12 is a current detector, 1
4 is a gain adjuster. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Scope of Claims] A plurality of voltage source inverter devices connected to a common DC bus bar and individually controlling AC motors at variable speeds, a DC power supply device supplying DC power to the DC bus bar, and a voltage of the DC bus bar. In a DC bus-type AC variable speed device comprising a voltage detector that detects information and a voltage controller that outputs a control signal to the DC power supply based on the output information from the voltage detector, the DC power supply A current detector detects the current value at the time of device startup, and an integrator integrates this current value by the time required for the voltage to rise between the DC bus and the gain of the voltage controller is adjusted by the integrated value of this integrator. An AC variable speed device using a DC bus system, characterized in that it is equipped with a gain adjuster to adjust the speed.