JPS62203567A - Control circuit for inverter apparatus - Google Patents

Abstract

PURPOSE:To stabilize the output voltage of an inverter apparatus by using a present DC bus voltage value when the variation amount of the DC bus voltage is small and a DC bus voltage mean value when the variation amount is large to correct a V command. CONSTITUTION:Differential circuit 10 compares present DC bus voltage value detected by a voltage detector 5 which a DC bus voltage mean value during a past predetermined period obtained by a voltage averaging circuit 11, and outputs a voltage abrupt change signal when the absolute value of the difference of both exceeds a predetermined value. The averaging circuit 11 inputs the DC bus voltage value at every predetermined time while a voltage abrupt change signal is not input, obtains a DC bus voltage value mean value of past predetermined time up to present time to output it to a V command correcting circuit 6, and the voltage abrupt change signal to a DC bus voltage mean value when the voltage abrupt change signal is input to output present DC bus voltage value to the correcting circuit 6. The correcting circuit 6 outputs a V command after correction to a PWM signal forming circuit 7.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a control circuit for an inverter device that corrects the output ground pressure of the inverter in response to fluctuations in the DC bus voltage of the inverter device.

[Conventional technology]

Conventionally, as a control circuit for this type of inverter device, there is a T circuit f) shown in FIG. In the figure, (1) is the forward conversion part of the inverter device that converts the three-phase AC voltage to the pulsating current voltage, and (2) is the converting section of the inverter device that converts the pulsating current [BE into the DC rIL king].
The smoothing capacitor (3) is an inverse converter that converts the above DC voltage into a variable voltage and variable frequency AC voltage, (4)
l; is an induction motor, (5) detects the DC bus voltage of the inverter device (7, IHj that outputs as a DC bus voltage value
pressure detection circuit, (6) corresponds to the above voltage value, ■command 1 and correction are added, and the corrected ■command and (7 output -j) ■command correction circuit, (7) is ■ A PWM signal generation circuit that generates a WM signal in the inverter device 2Bnl' using the command, (8) drives the switching element of the inverter device inverse conversion section (3) from the PWM signal (ζ). This is a drive circuit that

FIG. 4 shows another example of a control circuit for a conventional inverter device. In the figure,
(9) is a voltage averaging circuit that takes in the voltage value for a certain period of time, calculates the average value of the DC bus voltage for a certain period in the past up to the present time, and outputs the average value.

Next, the operation will be explained. In the circuit of FIG. 3, a voltage detection circuit (5) detects the DC bus voltage of the inverter device and outputs it as a DC bus voltage value. (2) The command correction circuit (6) uses the DC bus voltage value to correct the output voltage of the inverter to the (2) command according to the following formula, and outputs the corrected V command.

Vdc.

■Command after correction - ■Command × ・・・・・・(1) r: r
VdCQ: Reference value of DC bus voltage Vdc: DC bus voltage value The drive circuit (8) drives the switching elements of the inverse conversion section (3) of the inverter device using the PWM signal.

DC bus voltage 1: [The input voltage to the forward conversion unit (1) of the inverter device fluctuates by ζζ, and when the inverter device is performing regenerative operation 7P, Eζ increases. However, in such a case, ■If the command is not corrected for ζ, the output 11iIr pressure of the inverter will also fluctuate as the DC bus voltage fluctuates.3 The circuit shown in Figure 3 1 O. From the above equation (1) Eζ, add v command Eζ correction t and add 1 to J:J.
This is to maintain the output voltage.

That is, in Example 9, the DC bus voltage becomes lower than the base value at T.
In this case, by formula (1), the ■ command is set to the standard value (V7f
The V command obtained from pattern EC is shown in Figure 1ζ. [In other words, the output voltage pulse height decreases as the DC bus voltage decreases, the pulse width is increased (not compensated for by ζ), and the output ground pressure is kept constant (ζ).
It can be seen that in the fifth (ζ), the DC bus voltage L±(Jk upper and lower previous output line chamber EE waveform 03 and the output line voltage waveform 0 after the drop phantom fundamental wave voltage 09 match.

Next, in the fourth circuit (1, t3), the average value of the DC bus voltage of the ζ electric current is determined and outputted, and the Vd , c is the average value of this DC bus voltage.
This is Komenorano.

[Problem that the invention seeks to solve]

However, since the control circuit of the conventional inverter device is configured as described above, there are problems as described below. Perform V command correction processing using the pressure value data as is.
As shown in Fig. 6 αG, when the DC bus voltage slightly fluctuates in a relatively fast cycle, the output voltage of the inverter device changes as shown in Fig. 6 (To) due to a delay in the correction process, etc. Slight fluctuation causes anxiety 7F:, (!:), especially when the torque pulsation of the induction motor (4) becomes large during steady operation,
One problem is that vibration and noise increase.

In addition, in the circuit shown in FIG. 4, the above-mentioned unstable phenomenon of the output voltage can be avoided since the command correction process is performed using the average value during a certain period of the detected DC bus voltage value data. Figure 7 α9. As shown in @, when the DC bus voltage changes greatly and suddenly (for example, when the input voltage suddenly changes or when switching to regenerative operation), the delay in response due to averaging causes When f occurs, the inverter output voltage temporarily rises or falls, and when it rises, it becomes overexcited, causing a large current to flow in the main circuit of the inverter, and when it falls, it causes a lack of torque. .

This invention is an effort to solve the above-mentioned problems, and is useful if the output voltage of the inverter device is unstable even if the DC bus voltage slightly fluctuates in a relatively fast cycle. To obtain a control circuit for an inverter device that can always keep the output normal pressure of a six-inverter unit constant even when the bus voltage suddenly changes, and that does not cause overexcitation or insufficient torque of an induction motor.

[One-shot means for solving the problem] The control circuit of the inverter device according to the first invention compares the average value of the DC bus voltage for a certain period in the past up to the present time with the DC bus voltage value at the present time. , as long as the absolute value of the difference between the two does not exceed a certain specified value, the V command correction process is performed using the above-mentioned DC bus voltage average value, and when the absolute value of the difference between the two exceeds the specified value, the above-mentioned By performing command correction processing using the current DC bus voltage value,
Make sure to always keep the output voltage of the inverter constant (ζ and γ).

However, the control circuit for the inverter device according to the second invention compares the average value of the DC bus voltage with the current DC bus voltage value, whereas the invention of ff@1 above compares the average value of the DC bus voltage with the current DC bus voltage value. Then, the steady DC bus voltage value data, which is the DC bus voltage value, and the current DC bus voltage value are compared.

[Effect]

The difference circuit in this first invention - ζ is configured to calculate the current DC bus voltage value detected by the voltage averaging circuit and the average DC bus voltage value for a certain period of time in the past up to the present time, which is determined by the voltage averaging circuit. The values are compared, the absolute value of the difference between the two is obtained, and when the value exceeds the specified value, a sudden voltage change signal is output.

In addition, the voltage averaging circuit normally outputs the above-mentioned DC bus voltage average value, but when the above-mentioned sudden voltage change signal is input,
This outputs the current DC bus voltage value.

The output of this voltage averaging circuit is used to correct the command.

The difference circuit in this second invention compares the current DC bus voltage value detected by the voltage detection circuit 5ζ with the steady DC bus voltage value data stored in the voltage storage circuit, The absolute value of the difference between the two is determined, and when that value exceeds a specified value, a sudden voltage change signal is output. Hereinafter, the same operation as this first invention is performed.

[Embodiments of the invention]

An embodiment of the first invention will be described below with reference to the drawings. The same parts as in FIGS. 3 and 4 are indicated by the same reference numerals.

In Fig. 1, QG calculates the absolute value of the difference between the DC bus voltage average value from the voltage averaging circuit αυ described later and the current DC bus voltage value from the voltage detection circuit (5), and when the value exceeds the specified value αυ is a differential circuit that outputs a sudden voltage change signal at certain times, and normally takes in the DC bus voltage value at regular intervals, calculates the average value of the DC bus voltage values for a certain period of time up to the present time, and uses it as a V command correction circuit. (6), but when the sudden voltage change signal is input, the DC bus voltage average value is replaced with the current DC bus voltage value and is output to the V command correction circuit (6), and at the same time The average value calculation process is also performed by a voltage averaging circuit that uses this current DC bus voltage value as an initial value.

Next, the operation Gζ will be explained. As mentioned above, in the conventional inverter device control circuit shown in Part 3, when the DC bus voltage slightly fluctuates at a relatively fast cycle, the output voltage of the inverter will slightly fluctuate due to delays in correction processing, etc. There is one problem that makes it unstable. In addition, in order to solve this problem, the conventional control circuit shown in Figure 4 uses the average value of the DC bus voltage during a certain period to correct the command. Although the unstable phenomenon of the output voltage of the device can be avoided, the DC bus 1
! When the voltage changes greatly and suddenly, the output voltage of the inverter device temporarily increases or decreases due to the delay in the averaging response. The control circuit of the inverter device shown in Figure 1 is as follows:
A difference circuit αO is provided to calculate the difference between the current DC bus voltage value of the voltage detection circuit (5) and the average value of the DC bus voltage during a certain period in the past from the lightning pressure averaging circuit circle. When tty is smaller than this value (that is, when the DC bus normal pressure fluctuates slightly, use the voltage averaging circuit Ql) to correct the V command using the average DC bus voltage, and When the above-mentioned difference is larger than the predetermined value (i.e., when the DC bus voltage changes greatly and suddenly), the voltage detection circuit (5) detects it and uses the current DC bus normal pressure as it is. By correcting the command, the two problems mentioned above can be solved at the same time.

That is, in the circuit shown in Fig. 1, the difference n path OG is detected by the voltage detection circuit (5) l, T is determined by the current DC bus voltage value and the voltage average circuit a old ζ, and is calculated from the current DC bus voltage value during the past one period. and the average value of the DC bus voltage, and when the absolute value of the difference between the two exceeds a specified value, a sudden voltage change signal is output. While the sudden voltage change signal is not input to the voltage averaging circuit α1)+, the DC bus voltage value is taken in for a period of time;
The average value of the DC bus voltage values for a certain period in the past up to the present time is requested and outputted from the command correction circuit (6). It replaces the current DC bus voltage value + 1 and outputs it to the command correction circuit (6), and uses this current DC bus voltage value as the initial value for the subsequent average value calculation process. Next, the command correction circuit (6) 6) uses the DC bus voltage average value from the voltage averaging circuit αυ or the current DC bus voltage value to correct the ■ command that indicates the constant output voltage of the inverter device using the equation 1: (1) ζζ. In addition, after correction■
Takes commands and outputs them.

As described above, ■Correction of the command (in contrast, by using the current DC bus voltage value and the average DC bus voltage value depending on the amount of change 1ζ in the DC bus 1! pressure, the above-mentioned conventional impark J) Because it is possible to solve two problems in the control circuit of the device at the same time.

In addition, in the embodiment of the first invention, the differential circuit l1lI
q is the current DC bus 1 from the voltage detection circuit (5)! An embodiment of the second invention is shown in FIG. 1 and FIG. The steady DC bus room pressure value data stored in @ is used as a comparison target (t J<), and in this case as well, the same effect as in the first embodiment of the invention can be obtained.

That is, 1! of FIG. 2 according to this second invention! ! At 1, the voltage storage circuit @ receives the voltage sudden change signal from the differential circuit αO, and only at this time, the voltage detection circuit (5) at that time is input.
The DC bus voltage value from the DC bus 11EF of the differential circuit is stored and is output as value data while the sudden voltage change signal is not input. Differential circuit (IG is the steady DC bus voltage value data,
l! - Compare the current DC bus voltage value from the voltage detection circuit (5), find the absolute value of the difference between the two, and recommend that the value be the specified value. (6) and output to the voltage averaging circuit αη). The operation of the other circuits is the same as that of the first embodiment of the invention shown in FIG.

〔Effect of the invention〕

As described above, according to the first and second inventions,
■For command correction, when the amount of change 1 in DC bus voltage is small, the current DC bus voltage value is used, and when the amount of change is large, the average value of DC bus voltage is used. Even if the DC bus voltage slightly fluctuates at a relatively fast cycle, the output voltage of the impark device will be unstable. It is possible to keep the output 11'/pressure of the inverter constant at 1ζ even in the case of sudden changes in γ, and to obtain a WA control circuit for the inverter that does not cause overexcitation or insufficient torque of the induction motor. can.

[Brief explanation of drawings]

FIG. 1 is a circuit configuration diagram of a control circuit of an inverter device according to an embodiment of the first invention, and the second figure is a circuit configuration diagram of a control circuit of an inverter device according to an embodiment of the second invention. Figure 8 is a circuit configuration diagram of a control circuit of a conventional inverter device, Figure m4 is a circuit configuration diagram of a control circuit of a conventional inverter device, and Figure 5 is a circuit configuration diagram of a control circuit of a conventional inverter device. Output 'It 81: - foot) Koho -)
Figure 1 and Figure 6 show how, in the conventional circuit shown in Figure 3, the DC bus voltage fluctuates slightly in the relatively early 1M period, and when this happens, the output voltage of the inverter device becomes unstable. Figures 73 and 73 are diagrams showing how in the conventional circuit shown in Figure 4, the DC bus voltage changes greatly and suddenly, and the output voltage of the inverter device temporarily rises or falls at this time. In the figure, (3) is the inverse conversion section, (5) is the dragon pressure simulation circuit, (6) is the V command correction circuit, (7) is the PWM signal generation circuit, (9) is the voltage average circuit, and the symbol is the difference. The circuit, αυ, is a voltage average circuit, and the circuit is a voltage storage circuit. In addition, in the figures, the same reference numerals indicate the same parts.

Claims (2)

[Claims] (1) In the control circuit of an inverter device that converts AC or DC power into variable frequency, variable voltage AC power,
A voltage detection circuit detects the DC bus voltage, which is the input voltage to the inverse converter, and outputs it as a DC bus voltage value. Normally, the DC bus voltage value is taken in at regular intervals, and the data is calculated for a certain period in the past up to the present moment. A voltage averaging circuit that calculates and outputs the average value of the DC bus voltage, and when a sudden voltage change signal is input, replaces the above average voltage value with the current DC bus voltage value and outputs it, and a voltage averaging circuit that calculates and outputs the average value of the DC bus voltage. A differential circuit that calculates the absolute value of the difference with the bus voltage value and outputs the voltage sudden change signal when the difference exceeds a specified value, and a V command that is the inverter output voltage command according to the output of the voltage average circuit. A control circuit for an inverter device, comprising: a V command correction circuit that performs correction and output; and a PWM signal creation circuit that creates a PWM signal using the output from this circuit. (2) In the control circuit of an inverter device that converts alternating current or direct current power into variable frequency, variable voltage alternating current power,
A voltage detection circuit detects the DC bus voltage which is the input voltage to the inverse converter and outputs it as a DC bus voltage value, and only when a sudden voltage change signal is input, stores the DC bus voltage value at that time and outputs the sudden voltage change signal. A voltage storage circuit that outputs steady DC bus voltage value data while holding the DC bus voltage value when there is no input, and a voltage storage circuit that calculates the absolute value of the difference between the steady DC bus voltage value data and the DC bus voltage value, and that difference is specified. A differential circuit that outputs the sudden voltage change signal when the voltage exceeds the above value, and a differential circuit that normally captures the DC bus voltage value at fixed time intervals, calculates and outputs the average value of the DC bus voltage for a fixed period in the past up to the present time, and When the sudden voltage change signal is input, there is a voltage averaging circuit that replaces the average voltage value with the current DC bus voltage value and outputs it, and corrects it to the V command, which is the inverter output voltage command, according to the output from this circuit. 1. A control circuit for an inverter device, comprising: a V command correction circuit that adds and outputs a V command; and a PWM signal creation circuit that creates a PWM signal based on the output from this circuit.