JPH04285497A - Constant ratio controller for output frequency between a plurality of inverters - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention provides a method for adjusting the output frequency between a plurality of inverters by keeping the output frequency ratio constant between a plurality of PAM type inverters, or by keeping the rotation speed ratio among synchronous motors of which each inverter is a load constant. This invention relates to a constant ratio control device.

0002

2. Description of the Related Art Conventionally, constant control of the output frequency ratio between a plurality of inverters or constant control of the rotation speed ratio between synchronous motors driven by each inverter has been performed by controlling each inverter or a combination of each inverter and the motor. On the other hand, each independently configures a closed-loop negative feedback control system that controls the frequency deviation between the target frequency and the output frequency or the deviation between the target rotational speed and the actual rotational speed to zero over an appropriate time period. In addition, a predetermined ratio is given between each of the target values to perform the required constant ratio control.

0003

However, in the conventional constant ratio control as described above, a forward-facing element such as a regulator and a feedback element such as a frequency or rotation speed detector are attached to each of a plurality of inverters. It is necessary to configure a negative feedback control system for the rotation speed, which leads to a complicated circuit configuration for the required functions and an increase in price. Furthermore, it is usually extremely difficult to keep the required ratio constant at all times due to differences in control responsiveness between the respective control systems. In view of the above, the present invention is directed to a PAM type inverter or a combination of the inverter and a synchronous motor, and relates to constant ratio control as described above, and provides a constant output frequency ratio between a plurality of inverters, which makes it possible to simplify and reduce the cost of the required circuit configuration. The purpose is to provide a control device.

0004

Means for Solving the Problems In order to achieve the above object, the present invention provides a constant output frequency ratio control device between a plurality of inverters, which includes a frequency setter that outputs a reference frequency as a voltage signal, and a frequency setter that outputs a reference frequency as a voltage signal. a voltage/frequency converter that receives a voltage output and outputs a pulse signal of the reference frequency; and a plurality of frequency dividers that receive the output of the converter and output pulse signals of frequencies divided at predetermined frequency division ratios. , a plurality of frequency division setters for specifying a predetermined frequency division ratio for each of the frequency dividers, and switching at a predetermined frequency and a predetermined phase difference for the main circuit switching element of the corresponding inverter receiving the output of each of the frequency dividers. A plurality of phase conversion counters that output command signals are provided, and the load of each of the plurality of PAM type inverters controlled by the control device is a synchronous motor, and the required rotation speed of each motor is set to a synchronous motor. A frequency corresponding to the rotation speed is set by a frequency divider setter in the control device, and each electric motor is controlled to have its own open-loop rotation speed, while at the same time constant control of the rotation speed ratio between the motors is performed. Assumed to be performed.

[0005]

[Operation] The present invention targets a plurality of PAM type inverters, and divides a single reference frequency pulse by a plurality of frequency dividers having a ratio between frequency division ratios that is the same as the output frequency ratio between the respective inverters. The frequency of each pulse signal obtained in this manner is used as the specified output frequency value for each inverter, and each pulse signal has a predetermined phase difference (for example, 120 during 3 phase
A phase conversion counter is used to organize the pulse signals into multiple sets of pulse signals with a frequency of All pulse calculations are performed in an open loop based on a certain single frequency pulse signal. Therefore, even if some variation occurs in the reference frequency pulse, the output frequency ratio itself between the inverters cannot vary and is always maintained at the originally planned ratio.

Therefore, when each inverter is loaded with a synchronous motor having a rotation speed synchronized with the driving power supply frequency, the rotation speed ratio between the respective motors is always the same as the output frequency ratio between the respective inverters. It will be preserved.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below with reference to the circuit diagram shown in FIG. In FIG. 1, 1 is a reference frequency setter that outputs a specified value f1 of the reference frequency as a voltage signal; 2
is a voltage/frequency converter V/f which receives the voltage output of the setting device and outputs a pulse train of the reference frequency f1; 3 and 4 are frequency dividers, and the voltage/frequency converter V/f receives the voltage output from the setting device and outputs the pulse train of the reference frequency f1; Frequencies f1 /α and f1 /β according to period ratios α and β
It outputs a pulse train. Also, 9 and 10 are P
AM type inverter, each with 3 phase AC input 3φ
a converter section 9a that converts and outputs AC to variable DC voltage;
10a, smoothing capacitors C1 and C2, and inverter sections 9b and 10b that form a three-phase bridge configuration with switching elements in each arm and output three-phase alternating current, respectively. Drive. Next, 5 and 6 are three-phase conversion counters, and the frequencies f1/α and f output from the frequency dividers 3 and 4, respectively.
1/β pulse signal, the frequencies of both signals are reduced again by the frequency division ratio K, and three sets of pulse signals having a mutual phase difference of 120 degrees are formed and output for each of the two frequency reduced signals. Both sets of signals are ON/OFF signals for the switching elements of each phase arm of the three-phase bridge structure in the inverter sections 9b and 10b, respectively.
This becomes an OFF switching command signal. Therefore, the output frequency of the inverter 9 is f1/(αK), that of the inverter 10 is f1/(βK), and the ratio of the two output frequencies is β/α. Further, the rotation speed of a synchronous motor is proportional to its AC power frequency, and if the synchronous motors SM11 and SM12 have the same number of poles, the rotation speed ratio of the two machines will be the same as the frequency ratio β/α. Become. That is, the output frequency ratio and rotation speed ratio depend only on the division ratio setting values α and β by the frequency division setters 7 and 8, and are unrelated to the reference frequency f1 and the division ratio K. becomes.

[0008]

According to the present invention, an output frequency control device for a plurality of PAM type inverters whose loads are the motors of the same machine includes a frequency setter that outputs a reference frequency as a voltage signal;
a voltage/frequency converter that receives the voltage output of the setting device and outputs a pulse signal of the reference frequency; and a plurality of voltage/frequency converters that receive the output of the converter and output pulse signals of frequencies divided at predetermined frequency division ratios. a frequency divider, a plurality of frequency division setters for specifying a predetermined frequency division ratio for each of the frequency dividers, and a predetermined frequency setting for the main circuit switching element of the corresponding inverter receiving the output of each frequency divider. By comprising a plurality of phase conversion counters that output switching command signals with a constant phase difference, the output frequency ratio between the plurality of inverters, and therefore the rotation speed ratio between the electric motors, can be changed to the output frequency or the rotation speed. It is possible to easily and reliably maintain a constant value at a required value without constructing a closed-loop negative feedback control system regarding the number, simplifying and reducing the cost of the circuit configuration of the required equipment, and further improving the required ratio constant control. Control performance can be improved.

[Brief explanation of the drawing]

[Fig. 1] Circuit diagram showing an embodiment of the present invention

[Explanation of symbols]

1 Setting device 2
V/f (voltage/frequency converter) 3, 4
Frequency divider 5, 6 3-phase conversion counter 7, 8
Frequency divider setter 9, 10
PAM method inverter 9a, 10a converter section 9b, 10b inverter section

Claims (2)

[Claims] 1. A frequency setter that outputs a reference frequency as a voltage signal, a voltage/frequency converter that receives the voltage output of the setter and outputs a pulse signal of the reference frequency, and a voltage/frequency converter that receives the output of the converter. a plurality of frequency dividers each outputting a pulse signal having a frequency divided by a predetermined frequency division ratio; a plurality of frequency division setting devices each specifying a predetermined frequency division ratio for each of the frequency dividers; and a plurality of phase conversion counters that receive the output of the frequency divider and output switching command signals of a predetermined frequency and a predetermined phase difference to the main circuit switching elements of the corresponding inverters. Constant output frequency ratio control device. 2. A constant output frequency ratio control device between a plurality of inverters according to claim 1, wherein the load of each of the plurality of PAM type inverters controlled by the control device is a synchronous motor, and the required rotation of each of the motors is The number of rotations is set as a frequency corresponding to the rotation speed by the frequency divider setter in the control device, and while controlling the rotation speed of each motor in its own open loop, at the same time the rotation speed ratio between the motors is controlled. A PAM method constant output frequency ratio control device between a plurality of inverters, characterized in that constant control is performed.