JP2002034262A - Inverter device - Google Patents

Abstract

An object of the present invention is to reduce the influence of noise as much as possible when taking in the output voltage of an inverter circuit. SOLUTION: In relation to two choke coils provided in a direction from two alternating voltage output terminals of an inverter circuit to an output side, one choke coil side is connected to an alternating voltage output terminal side and the other choke coil is connected to the other choke coil side. In the side, the potential is taken in from the side of the load side terminal, and is led to the differential amplifier.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter device for detecting an output voltage of an inverter device in a form in which the influence of a distortion factor and noise is suppressed.

[0002]

2. Description of the Related Art The present invention is not limited to this, but inverters have been conventionally operated in parallel.

FIG. 8 shows a configuration example of an inverter parallel operation device. In the figure, reference numeral 22 denotes an AC generator, 33 denotes a rectifier circuit (or a DC power supply circuit), 34 denotes a smoothing capacitor,
Denotes an inverter circuit, 38 denotes a filter circuit, 35 and 36 denote load terminals, 53 and 54 denote alternating voltage output terminals, and F denotes a load.

In the configuration shown in FIG. 8, switching control of the inverter circuits 37 on each side is performed by an on / off signal from a PWM circuit (not shown).
It outputs a high-frequency alternating voltage in the form of a rectangular wave. And
The filter circuit 38 includes two choke coils inserted between the terminal 53 and the terminal 35 and between the terminal 54 and the terminal 36.
And a capacitor inserted between them. Needless to say, the filter circuit 38 functions to filter the rectangular high-frequency alternating voltage output from the inverter circuit 37 and to introduce a desired sinusoidal voltage of, for example, 50 Hz to the load.

[0005] Each inverter device as shown in FIG. 8 extracts its own output voltage (internal voltage) and output current because it is necessary to detect the power output by itself.

In this case, in particular, in extracting the output voltage, there are various influences due to the influence of the high frequency alternating voltage having a rectangular waveform generated by the inverter device and the influence of the noise voltage introduced from the load side. You need to elaborate.

FIG. 9 shows an example of an electric potential extraction generally used conventionally, and FIG. 10 shows an example of an electric potential extraction disclosed in Japanese Patent No. 2688660. In each figure, the reference numerals in the figure correspond to those in FIG.

In FIG. 9 and FIG. 10, two choke coils are provided, respectively, because high frequency and noise (hereinafter, collectively referred to as noise) passing through the filter circuit are shown in FIG.
As shown in FIG. 1, there are a noise a and a noise b flowing back through the filter circuit 38 in the opposite phase and a noise c and a noise d flowing through the filter circuit 38 in the same phase.
One choke coil is intended to suppress any of these types of noise.

[0009] In the configuration of FIG.
5 and the potential on the terminal 36 side of the choke coil inserted between the terminal 54 and the terminal 36, and the potential on the terminal 36 side of the choke coil inserted between the terminal 54 and the terminal 36 is led to the differential amplifier A. The output voltage of the inverter circuit is extracted as the potential difference.

In the configuration of FIG. 10, the terminal 53 of the choke coil inserted between the terminal 53 and the terminal 35 is used.
The potential on the terminal side and the potential on the terminal 54 side of the choke coil inserted between the terminal 54 and the terminal 36 are led to the differential amplifier A, and the output voltage of the inverter circuit is extracted as the difference between the two potentials. are doing.

[0011]

The configurations shown in FIGS. 9 and 10 each have advantages and disadvantages. That is, in the case of the configuration of FIG. 9, noise based on high-frequency components from the inverter circuit side is easily suppressed, but noise from the load side is guided to the input side of the differential amplifier. Therefore, in some cases, it may be necessary to add another filter circuit to the load side of the terminals 35 and 36 in FIG. 9 and the input terminal of the differential amplifier.

In the case of the configuration shown in FIG. 10, noise from the load side is easily suppressed, but noise from the inverter circuit side is likely to remain and the presence of the choke coil causes the original output voltage (in the inverter circuit). The original sinusoidal voltage) may have a phase shift.

An object of the present invention is to reduce the influence of noise as much as possible when taking in the output voltage of an inverter circuit.

[0014]

According to the present invention, one of two choke coils provided in series between two alternating voltage output terminals of an inverter circuit and two load terminals is connected to one of the two choke coils. On the choke coil side, the first potential is taken from the alternating voltage output terminal, and on the other choke coil side, the second potential is taken from the load side terminal.

That is, noise from the inverter side is suppressed by one choke coil, and noise from the load side is suppressed by the other choke coil.

[0016]

FIG. 1 is a block diagram showing an embodiment of the present invention. Reference numerals 35 and 36 in the figure are load-side terminals, respectively.
37 is an inverter circuit, 38 is a filter circuit, 53 and 5
4 denotes an alternating voltage output terminal, and A denotes a differential amplifier.

In the case of the configuration shown in FIG.
1 is suppressed by the choke coil between the terminal 53 and the terminal 35, and the noise a and the noise c shown in FIG. 11 are suppressed by the choke coil between the terminal 54 and the terminal 36. You will be suppressed.

Hereinafter, a configuration in which the inverter device of the present invention is applied to a portable AC generator will be described.

First, in FIG. 2, for example, 100 V
2 shows an electrical configuration of a portable AC generator 21 that generates a 50 Hz or 60 Hz AC power supply. The portable AC generator 21 includes a three-phase AC generator 22 driven by an engine (not shown), and a single-phase inverter unit 23 connected to a subsequent stage.

The alternator 22 includes fuel (gasoline) for the engine in addition to the rotor and the armature (both not shown).
A stepping motor 24 is provided for controlling the rotation speed of the engine by controlling the supply amount. Armature has Y
Connected main windings 25u, 25v, 25w and auxiliary winding 2
6 are wound, and the main winding terminals 27u, 27v, 2
7w and the auxiliary winding terminals 28a, 28b are connected to input terminals 29u, 29v, 29w and input terminals 30a, 30b of the inverter unit 23, respectively.

On the other hand, the inverter unit 23 is configured as follows. That is, the input terminals 29u,
A rectifier circuit 33 is connected between 9v, 29w and the DC power supply lines 31, 32. A smoothing capacitor 34 is connected between the DC power lines 31 and 32,
An inverter circuit 37 and a filter circuit 38 are cascaded between the output terminals 1 and 32 and the output terminals 35 and 36. Note that the rectifier circuit 33 corresponds to a DC power supply circuit in the present invention.

The rectifier circuit 33 has a configuration in which thyristors 39 to 41 and diodes 42 to 44 are connected in the form of a so-called three-phase mixed bridge.
7 has a configuration in which transistors 45 to 48 (corresponding to switching elements) and free-wheel diodes 49 to 52 are connected in a so-called full bridge form.

The filter circuit 38 includes an inverter circuit 37
Output terminal 53 and output terminal 3 of inverter unit 23
5 and a capacitor 56 connected between the output terminals 35 and 36 of the inverter unit 23. Inverter circuit 37
Is directly connected to the output terminal 36 of the inverter unit 23, and a current transformer 57 for detecting an output current is provided in a current path from the output terminal 54 to the filter circuit 38. .

Further, the inverter unit 23 includes a control power supply circuit 58, a control circuit 59, and a drive circuit 60. The control power supply circuit 58 includes the input terminal 30
a, an AC voltage induced in the auxiliary winding 26 is input through the terminals 30 and 30b, the DC voltage is rectified and smoothed, and a control DC voltage (for example, 5 V, ± 15 V) for operating the control circuit 59 is generated. Has become. The AC voltage induced in the auxiliary winding 26 is also input to the control circuit 59 to detect the engine speed.

The control circuit 59 includes the microcomputer 6
1 (hereinafter referred to as microcomputer 61), DC power supply detection circuit 6
2. It comprises an output voltage detection circuit 63, an output current detection circuit 64, and a PWM circuit 65. Microcomputer 61
Although not specifically shown, CPU, RAM, ROM,
The input / output port, the A / D converter, the timer circuit, the oscillation circuit, and the D / A converter are configured as one-chip ICs.

The DC power supply detection circuit 62 is connected to the DC power supply line 31.
And a DC voltage Vdc between the DC voltage V.sub.32 and the detected DC voltage V.sub.dc, and outputs the detected DC voltage to the microcomputer 61 as a DC voltage detection signal. In this case, the microcomputer 61 controls the thyristors 39 to 41 based on the DC voltage detection signal so that the DC voltage Vdc becomes a predetermined voltage, for example, 180V.

The output voltage detecting circuit 63 includes a voltage dividing circuit for dividing the voltage between the output terminals 53 and 54 of the inverter circuit 37, and a filter for removing a carrier wave component from the divided rectangular wave voltage. , And outputs the detected output voltage Vs to the microcomputer 61 and the PWM circuit 65 as an output voltage detection signal.

The output current detection circuit 64 (corresponding to output current detection means) converts the output current detected by the current transformer 57 to a predetermined voltage level, and outputs the detected output current Is.
Is output to the microcomputer 61 and the PWM circuit 65 as an output current detection signal.

The PWM circuit 65 executes PWM control to generate drive signals G1 to G4 for the transistors 45 to 48. The drive signals G1 to G4 are applied to the bases of the transistors 45 to 48 via the drive circuit 60, respectively.

An output frequency of the microcomputer 61 is set to 50 Hz by a switch input from a switch input unit (not shown).
It can be set to any of 60 Hz. For example, when an AC power supply of 50 Hz and 100 V is to be generated, a sine wave reference signal Vsin having the same frequency as the set output frequency is supplied to the PWM circuit 65. I have.
However, the sine wave reference signal Vsin is adjusted so that the detection output voltage Vs of the output voltage detection circuit 63 becomes equivalent to 100 V output, that is, output voltage feedback control is performed. . Further, as will be described later, the sine wave reference signal Vsin is also for adjusting the output frequency based on the output active power.

As shown in FIG. 3 (a), the PWM circuit 65 uses the sine wave reference signal Vsin and a carrier wave Sc composed of, for example, a triangular wave of 16 kHz (in the drawing, the frequency is extremely reduced for convenience). The high-frequency voltage Vo having a rectangular wave shape shown in FIG.
Hz or 60 Hz).
4 is generated. The high frequency voltage V thus generated
The high frequency component o is, for example, 100 V · 50 H, as shown in FIG.
An AC output Voac of z or 60 Hz is formed.

The microcomputer 61 functions as active power detection means and control means. These functions will be described below together with their functions.

When the microcomputer 61 starts operation, the microcomputer 61
The output frequency is controlled according to the control flow chart shown in FIG. That is, in step Q1, the first zero cross of one cycle of the output voltage Vo (see FIG. 5,
Timing t0) is detected. In this case, the microcomputer 61
Since the effective zero crossing between the sine wave reference signal Vsin and the output voltage Vo ideally coincides with each other, the zero crossing timing t0 at the beginning of one cycle of the sine wave reference signal Vsin (timing that changes to the positive side) is set. Determine.
Thereafter, the instantaneous value Is is calculated from the detected output current Is at the timing of 64 times (equally spaced in time) for 1/2 cycle.
(N) (where n is 1 to 64) are detected and sequentially summed (step Q2, step Q3, step Q4). Then, when the total of 64 times ends (“YE” in step Q4).
S "), and proceeds to step Q5 to calculate (detect) the active power. In this case, the output voltage is uniquely 100 V
And the product of the above total value and the output voltage 100V is obtained. At this time, when the load W (see FIG. 6) is a low resistance load, the voltage / current phase does not change. When the load W is a coil load and a capacitor load, the voltage / current phase changes. ,
A minus component also appears in the instantaneous value Is (n) of the output current, and reactive power is generated. Note that the total value of step Q5 must be taken into account (6
It can be considered as an average current (without dividing the sum by 4).

In the next step Q6, a frequency difference for frequency correction is set. In this case, the frequency difference is obtained by an equation obtained by multiplying the active power by a constant (0.2 Hz / 2.8 kW). Then, in step Q7, a sine wave reference frequency Vsin to be changed is obtained. In this case, the frequency fluctuation range is 50.10 Hz at the upper limit and 49.90 Hz at the lower limit, and the upper limit frequency is 50.10 Hz as the reference frequency. The sine wave reference frequency Vsin to be changed is obtained by subtracting the frequency difference from the reference frequency. The relationship between the active power and the sine wave reference frequency Vsin to be changed is as shown in FIG.

Although not shown in the flowchart, the microcomputer 61 supplies the sine wave reference frequency Vsin to the PWM circuit 65 in the next half cycle so that the output frequency becomes the sine wave reference frequency Vsin. In this way, the output frequency is adjusted according to the active power.

The case where the portable AC power generator 21 is connected in parallel to supply power to the load F will be described. In FIG. 6A, for example, one of the two portable AC generators is a portable AC generator 21A, and the other is a portable AC generator 21B. Now, when the load F is AC 10
It is assumed that 35 A is consumed at 0 V. And each device 21
Assuming that A and 21B are operating in a well-balanced manner, for example, both output 50 Hz, 100 V, and 17.5 A of power. In this case, no cross current occurs between the devices 21A and 21B.

Here, as shown in FIG. 6 (b), one of the AC generators 21A
, Instantaneously becomes, for example, 49.96 Hz, a cross current flows from the other AC generator 21B to one AC generator 21A. Then, the active power of the AC generator 21B on the side where the cross current flows out increases, and the active power of the AC generator 21A on the side where the cross current flows enters decreases.

Then, in one AC generator 21A, the active power in step Q5 of the flowchart of FIG. 4 is reduced, so that the frequency difference in step Q6 is reduced. Thereby, the sine wave reference frequency Vsi of step Q7
n increases. That is, the output frequency is increased (FIG. 7
(B)).

In the other AC power generator 21B, the active power in step Q5 in the flowchart of FIG. 4 increases, so that the frequency difference in step Q6 increases. Thereby, the sine wave reference frequency Vsin of step Q7 decreases. That is, the output frequency is reduced.

The above-described control is performed separately in each of the devices 21A and 21B. On the one hand, the output frequency is controlled in the increasing direction, and on the other hand, the output frequency is controlled in the decreasing direction. The output frequencies of 21A and 21B match (see FIG. 7C), and the cross current is suppressed.

As described above, according to the present embodiment, the frequency is controlled to decrease as the active power increases.
Conversely, since the frequency is controlled to increase as the active power decreases, the two AC power generators 21A and 21B
Are operated in parallel, even if the output frequencies do not match, the output frequencies of the two AC power generators 21A and 21B immediately match, so that the cross current can be reliably suppressed.

In the configuration shown in FIG. 2, the differential amplifier A described with reference to FIG. 1 corresponds to the output voltage detection circuit 63 shown in FIG.

[0043]

As described above, according to the present invention, in taking in the output voltage of the inverter circuit, it is possible to appropriately suppress the noise from the inverter side and the noise from the load side.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 shows a configuration in which the inverter device of the present invention is applied to a portable AC generator.

FIG. 3 is a waveform diagram related to a PWM circuit.

FIG. 4 is a waveform diagram showing a sine wave reference signal and a detection output current.

FIG. 5 is a flowchart for explaining control contents.

FIG. 6 is an explanatory diagram at the time of inverter parallel operation.

FIG. 7 is a diagram illustrating a relationship between active power and frequency for explaining frequency control.

FIG. 8 shows a configuration example of an inverter parallel operation device.

FIG. 9 shows an example of potential extraction that has been generally used in the past.

FIG. 10 shows an example of potential extraction disclosed in Japanese Patent No. 2688660.

FIG. 11 is a diagram illustrating the distribution status of noise.

[Explanation of symbols]

 21: Portable AC generator (inverter device) 22: AC generator 23: Inverter unit 33: Rectifier circuit (DC power circuit) 35, 36: Load terminal 37: Inverter circuit 38: Filter circuit 53, 54: Alternating voltage Output terminal 59: control circuit 63: output voltage detection circuit (differential amplifier A)

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masao Ikui 3 Hayakawa, Hayakawa, Nitta-cho, Nitta-gun, Gunma Prefecture Inside the Nitta Plant of Sawafuji Electric Co., Ltd. (72) Inventor, etc. 991 Anadacho, Seto-shi, Aichi F-term in Toshiba Aichi factory (reference) 5H007 AA01 CA01 CB02 CB05 CC03 CC05 CC12 DA03 DA06 DB02 DB07 DC02 DC05 EA02

Claims (1)

[Claims] An inverter circuit having a DC power supply circuit and a switching element, for switching an output of the DC power supply circuit based on a PWM circuit to output a high-frequency voltage; and converting the high-frequency voltage into a sinusoidal AC voltage An inverter device comprising: a filter circuit that outputs two choke coils provided in series between two alternating voltage output terminals and two load-side terminals of the inverter circuit, respectively. At least a first potential taken from the alternating voltage output terminal on one side of the two choke coils, and a first potential taken from the load side terminal on the other side of the two choke coils. 2 is input, and a differential amplifier is provided, wherein the differential amplifier is configured to control the first potential and the second potential. And calculating the difference, the inverter apparatus characterized by comprising configured to output as an output voltage of the inverter circuit.