JP2002034259A - Inverter parallel operation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect the existence of a cross current, to control inverters so as to elevate their internal voltages and to suppress the undesirable cross current. SOLUTION: Detection of outputted (or inputted) active powers on respective inverter sides is utilized to calculate flowing-in electrical energies obtained by integrating flowing-in powers and, according to the calculation result, the internal voltages of the inverters are elevated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter parallel operation device which is controlled to eliminate undesired cross current between inverters operated in parallel.

[0002]

2. Description of the Related Art Inverter devices that are operated in parallel are known, and the active power is balanced between the inverters so as to eliminate unwanted cross-current power between the inverters that are operated in parallel. (Eg, Patent No. 267)
8991 and JP-A-2000-32764).

[0003]

In controlling to eliminate the above-mentioned cross current, it is necessary to appropriately grasp the generation of the cross current and to perform control to eliminate the cross current. The problem is how to grasp the generation of the cross current.

FIG. 3 shows a configuration in which two inverters are operated in parallel. In the figure, reference numeral 22 denotes an AC generator, 33 denotes a rectifier circuit, 34 denotes a smoothing capacitor, 35 and 36 denote output terminals, 37 denotes an inverter or an inverter circuit, 38 denotes a filter circuit, and F denotes a common load. I have.

FIG. 4 is an equivalent circuit diagram of the circuit configuration of FIG. 3 considering only the cross current.
When the effective power output from A) and P _A,

[0006]

(Equation 1)

[0007] Then, when the phase difference between the internal voltages is θ ₁ −θ ₂ = 0,

[0008]

(Equation 2)

[0009] become, when E _2> E _1, P _A takes a negative value, so that the cross flow power flows to the inverter 37A side.

The cross-current power flowing into the inverter is regenerated at the input side of the H-bridge constituting the inverter, and is charged in the smoothing capacitor 34A connected to the input side of the H-bridge, thereby increasing the terminal voltage of the smoothing capacitor 34A. Let it. Note that the cross-current power flowing in is not regenerated to the generator side. Therefore, the terminal voltage of the smoothing capacitor 34A keeps increasing, and this terminal voltage V becomes

[0011]

(Equation 3)

The voltage V is determined by

[0013] Incidentally, the terminal voltage V of the smoothing capacitor 34A is increased, the input voltage of the H-bridge inverter 37A is increased, the internal voltage E ₁ of the inverter 37A as described later, a sine wave in the PWM circuit which will be described later It is fixed at a value determined by the reference signal Vsin. In the present invention, the output voltage (internal voltage E
Raising (which may be considered as ₁ ) means performing control to increase the amplitude of the sine wave reference signal Vsin.

As described above, when the cross current exists, the terminal voltage of the smoothing capacitor 34 undesirably increases.
It is necessary to suppress this increase.

SUMMARY OF THE INVENTION It is an object of the present invention to detect the presence of a cross current and control the internal voltage (E ₁ ) of the inverter to increase so as to suppress the occurrence of an undesired cross current.

[0016]

In the present invention, attention is paid to the fact that the power output from each inverter (in some cases, flowing in) is detected corresponding to each inverter, and the power is detected. Is calculated (by integrating the negative power), and the internal voltage E in the inverter is calculated according to the calculated power (J). Let it rise. That is, generation of undesired cross current is suppressed.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the inverter device of the present invention is applied to a portable AC power supply device will be described below with reference to the drawings.

First, in FIG. 1, for example, 100 V
1 shows an electrical configuration of a portable AC power supply device 21 that generates a 50 Hz or 60 Hz AC power supply. The portable AC power supply 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 monitors the terminal voltage of the smoothing capacitor 34 based on the DC voltage detection signal.

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 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.

An 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.

The 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, the sine wave reference signal Vsin is used for adjusting the output voltage and output frequency output from the inverter circuit 37.

As shown in FIG. 2A, the PWM circuit 65 uses the sine wave reference signal Vsin and a carrier 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 removed by a filter circuit 38, for example, as shown in FIG.
An AC output voltage Voac of z or 60 Hz (that is, the internal voltage E) is formed.

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

The microcomputer 61 also functions as an effective voltage detecting means. As described with reference to FIGS. 3 and 4, when the undesired cross current flowing into the inverter circuit shown in FIG. 1 is generated, The incoming power is detected.
That is, the active power detection means (in the microcomputer 61) according to the present invention detects a negative voltage.

The microcomputer 61, (a -P _A with if negative value) the active power power detected by the detecting means by integrating,

[0034]

(Equation 4)

Has the function of calculating the electric power, and functions as the electric energy calculating means according to the present invention.

In the first embodiment of the present invention, control is performed as follows. That is, when the power amount calculating means calculates the power amount having a negative value, as described above, since the terminal voltage of the smoothing capacitor 34 continues to increase, the amplitude value of the sine wave reference signal Vsin is increased. , Through a PWM circuit,
Transistors 45 to 4 in inverter circuit 37
8 is controlled so that the internal voltage (E... May be conceptually regarded as voltage Voac) in the inverter circuit 37 is increased. That is, the internal voltage E is controlled in accordance with the magnitude of the inflowing electric energy J.

In the second embodiment of the present invention, control is performed as follows. That is, the internal voltage E is increased by a predetermined amount only when the value of the inflowing electric energy J has increased to a predetermined threshold value J _THO .

In the third embodiment of the present invention, control is performed as follows. That is, as shown in the first embodiment or the second embodiment, the amount of electric power flowing in is calculated, and the internal voltage E of the inverter circuit 37 is increased. However, since there is a possibility that an undesired error is mixed in the value of the inflowing electric energy J calculated by the microcomputer 61, the illustrated DC power supply detection circuit 62 which detects the terminal voltage of the smoothing capacitor 34 is used. Thus, the error is corrected. More specifically, it is determined that the voltage detected by the DC power supply detection circuit 62 has reached a threshold value V _THO prepared in advance as a value smaller than an undesirably increased value, and is calculated as the inflow power amount. Is reset to a desired value.

Assuming that the threshold value V _THO is set to a value equal to the above-mentioned V ₀ , the terminal voltage of the smoothing capacitor 34 becomes V ₀ , in other words, the inflowing electric energy J
Does not exist, and if the calculated inflowing electric energy J at that time has a "predetermined value", it can be regarded as an error. Therefore, the error is reset to zero.

In the fourth embodiment of the present invention, control is performed as follows. That is, the threshold value V _TH need not be limited to one, including the V _0, a large plurality of threshold V _THO than _{V 0, V TH1, V TH2} ... are prepared to, and each of A plurality of initial values for resetting the amount of inflow power in association with the threshold value are prepared. When the terminal voltage of the smoothing capacitor 34 reaches a certain threshold value V _TH1 , the calculated inflowing electric energy J is reset to an initial value J _TH1, and when the terminal voltage reaches a certain threshold value V _TH2 , the above calculation is performed. Resets the inflowing electric energy to the initial value J _TH2 ,
Make sure to reset like….

[0041]

As described above, according to the present invention, attention is paid to the fact that the power P output from each of the inverters is generally detected during the parallel operation of the inverters, and a means for integrating the power P is provided. To calculate the "inflow electric energy (inflow electric energy) J", and increase the internal voltage E of the inverter to suppress the generation of the cross current. It is possible to suppress the generation of cross-flow power only by using the amount of inflow power as a guide.

[Brief description of the drawings]

FIG. 1 shows a configuration of an embodiment of one inverter side in the present invention.

FIG. 2 shows a waveform in a PWM circuit.

FIG. 3 shows a configuration example of an inverter parallel operation device.

FIG. 4 shows an equivalent circuit in which occurrence of cross current is considered.

[Explanation of symbols]

21: Inverter (or inverter device or portable AC power supply device) 22: AC generator 23: Inverter unit 33: Rectifier circuit (or DC power supply circuit) 37: Inverter circuit 38: Filter circuit 59: Control circuit 61: Microcomputer (internal) And active power detection means and control means) 63: output voltage detection circuit (output voltage detection means) 64: output current detection circuit (output current detection means)

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Masao Iku 3 Hayakawa, Hayakawa, Nitta-cho, Nitta-gun, Gunma Prefecture Inside the Nitta Plant of Sawafuji Electric Co., Ltd. Address F-term in Toshiba Aichi Factory (reference) 5G066 HA08 HB03 5H007 AA05 AA17 CA01 CB04 CB05 CC05 CC12 DA06 DB02 DB12 DC02 DC03 DC05 EA02

Claims (4)

[Claims] 1. A first inverter is supplied with power from a DC circuit having a smoothing capacitor and controls one or both of an output voltage and an output phase by controlling a control element constituting the inverter. The second and subsequent inverters are supplied with power from a DC circuit having a smoothing capacitor, and control one or both of an output voltage and an output phase by controlling a control element constituting the inverter. A first filter circuit provided on the output side of the first inverter and a second filter circuit provided on the output side of the second and subsequent inverters are connected so as to be controllable; An inverter parallel operation device that supplies power to the load of the first inverter, wherein first active power detection means for detecting active power output by the first inverter; A second and subsequent active power detection means for detecting active power output from the second and subsequent inverters; and a first for calculating a power amount by integrating the power detected by the first active power detection means. And a second and subsequent power amount calculating means for calculating the power amount by integrating the power detected by the second and subsequent active power detecting means, and the first power An inverter having a power amount calculating unit, of the power calculating unit and the second or later power amount calculating unit, in which the output power amount has a negative value;
An inverter parallel operation device comprising: an output voltage increasing unit that increases the output voltage of the inverter in accordance with a negative amount of power calculated by the power amount calculating unit. 2. The method according to claim 1, wherein the output voltage increasing means is configured to output the output voltage of the inverter when the power value of the negative value calculated by the power amount calculating means becomes more negative than a predetermined threshold value. The inverter parallel operation device according to claim 1, wherein the device is configured to activate ascent. 3. A smoothing capacitor terminal voltage detecting means for detecting a terminal voltage of the smoothing capacitor on each of the inverters, and wherein the terminal voltage detected by the smoothing capacitor terminal voltage detecting means is higher than a predetermined threshold value. If the power amount calculated by the corresponding power amount calculation means indicates a negative value on the inverter side having a smaller value, the power amount of the calculated negative value is reset to an initial value including zero. The inverter parallel operation device according to claim 1 or 2, further comprising an electric energy reset unit. 4. A method according to claim 1, wherein a plurality of thresholds are determined for the terminal voltage detected by said smoothing capacitor terminal voltage detecting means, and said power amount resetting means sets said detected terminal voltage to each of the corresponding thresholds. 4. The inverter parallel operation device according to claim 3, wherein the power amount calculated by the power amount calculation means is reset to an initial value predetermined for each of the thresholds.