JP2001209445A - Inverter controller for system interconnection - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inverter controller for system interconnection, which can prevent its step-up voltage converter from making a noise and losing more power keeping constantly an operating frequency of the converter event though a direct current voltage of an input power supply varies. SOLUTION: The inverter controller 15 for system interconnection controls a direct current reactor current generated by a direct reactor 6 a system interconnection inverter that has a step-up voltage converter 3 that steps up an input voltage Vin of an input power 1. The inverter controller 15 has a command value adder 11 and a command value subtractor 12, which adds and subtracts the command value for a direct reactor current, which is generated by a value generator 9 for the direct reactor current, a hysteresis value generated by a hysteresis width generator 10, then, the controller generates an upper limit command value and a lower limit command value for the direct reactor current so that the hysteresis width is variable against the input voltage Vin. The controller also has a method to change continuously the hysteresis width with corrections obtained by multiplying the hysteresis value with the input voltage Vin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system interconnection inverter control device for converting DC power from a solar cell, a fuel cell, or the like to an AC system, converting the DC power into AC power, and supplying the AC power.

[0002]

2. Description of the Related Art A conventional system interconnection inverter control device will be described below with reference to the drawings. FIG. 3 is a block diagram showing a configuration of an example of a conventional grid-connected inverter. The system interconnection inverter supplies AC power to the system 2 at a commercial frequency of 50/60 Hz using a DC input power supply 1 as an input.

In FIG. 3, a system interconnection inverter includes a boost converter 3 for boosting an input voltage Vin from an input power supply 1 to a voltage higher than a system voltage VAC, and a voltage of about several hundred μF for removing a high-frequency component in the boosted voltage. It is composed of the following intermediate-stage capacitor 4 and a full-bridge inverter 5 for shaping the output current Io into a sine wave, and is connected to the system 2. The boost converter 3 is composed of an input capacitor of about several thousand μF for smoothing the input voltage Vin, a DC reactor 6 for storing energy, two switching elements QB and a switching element QF. An output reactor 7 and an output capacitor 8 are arranged to remove a high frequency component of the output current.

The operation of the above configuration will be described.
During the period when the input voltage Vin is smaller than the system voltage VAC,
Since the full-bridge inverter 5 switches the output boosted by the boost converter 3 at a low frequency, the current of the DC reactor 6, that is, the low-frequency component of the DC reactor current forms the output current Io. Here, since the system voltage VAC is a sine wave and the input voltage Vin is constant, if the average value of the DC reactor current is controlled to be a sine wave square, a sine wave can be obtained as the output current Io. Become.

Therefore, the command value adding means 11 and the command value subtracting means 11 combine the sine-wave squared DC reactor current command value generated by the DC reactor current command value generating means 9 and the hysteresis width generated by the hysteresis width generating means 10. 12
The upper and lower limit command values of the DC reactor current command value obtained by adding and subtracting with the above, and the upper and lower limit of the DC reactor current detected by the DC reactor current detection means 13,
The hysteresis comparator 14 performs successive comparisons, and based on the result, the pulse width of the two switching elements QB and QF constituting the boost converter 3 is determined. The DC reactor current command value generation means 9 to the DC reactor current detection means 13 constitute a system interconnection inverter control device 15.

[0006]

In such a conventional system interconnection inverter, when the hysteresis comparator 14 is used to control the boost converter 3, the operating frequency is the hysteresis width, the input voltage Vin, and the intermediate stage voltage VM.
And the inductance of the DC reactor 6. In the grid-connected inverter, since the input power source 1 is a solar cell or a fuel cell, the input voltage Vin fluctuates greatly, and when the operating frequency is lowered, noise due to operation in the audible range increases, and conversely, the operating frequency increases. The problem was that the loss would increase.

An object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to provide a grid-connected inverter control device capable of alleviating an increase in noise and loss with respect to a large change in input voltage of an input power supply.

[0008]

According to a first aspect of the present invention, there is provided a grid-connected inverter including a DC reactor and two switching elements, and a boost converter for boosting an input voltage from a DC input power supply. Wherein the grid-connected inverter control device for controlling the DC reactor current of the DC reactor generates an upper limit command value and a lower limit command value of the DC reactor current command value by adding and subtracting a hysteresis width to the DC reactor current command value. And a system interconnection inverter control device in which the hysteresis width is variable in accordance with the input voltage.

According to the present invention, the operating frequency can be maintained substantially constant even when the input voltage changes.

According to a second aspect of the present invention, an upper limit command value and a lower limit command value of a DC reactor current command value are generated as a correction hysteresis width using a value obtained by multiplying a fixed hysteresis width by an input voltage. 1 is a system interconnection inverter control device related to 1.

According to the present invention, the operating frequency can be maintained substantially constant even when the input voltage changes by changing the hysteresis width steplessly.

[0012]

1 is a block diagram showing a configuration of a step-up converter according to a first embodiment of the present invention; Hysteresis width generating means for generating a hysteresis width for alternately turning on or off two switching elements; and generating an upper limit command value of the DC reactor current command value by adding the hysteresis width to the DC reactor current command value. Command value adding means, a command value subtracting means for subtracting the hysteresis width from the DC reactor current command value to generate a lower limit command value of the DC reactor current command value, and a DC reactor current detection for detecting a current of the DC reactor Means, a hysteresis comparator, and an input voltage from an input power supply. An input voltage detection means detect, and varies the hysteresis width on the basis of the detected input voltage.

In the invention according to claim 2, the system interconnection inverter control device includes a correction hysteresis width generating means, wherein the correction hysteresis width generating means fixes the input voltage detected by the input voltage detecting means to a fixed hysteresis width. , A corrected hysteresis width is generated, and the corrected hysteresis width is added to or subtracted from the DC reactor current command value to set an upper limit command value and a lower limit command value. At this time, the correction hysteresis width is steplessly changed with respect to the input voltage.

Hereinafter, embodiments of the present invention will be described.

[0015]

(Embodiment 1) Hereinafter, Embodiment 1 of a system interconnection inverter control device of the present invention will be described with reference to the drawings. This embodiment relates to claim 1.

FIG. 1 is a block diagram showing the configuration of this embodiment. The same components as those in the conventional example are denoted by the same reference numerals. This embodiment is different from the conventional example in that the grid-connected inverter control device 15 includes an input voltage detecting means 16 for detecting an input voltage Vin from the input power supply 1.

The grid-connected inverter is similar to the conventional example,
50/60 Hz to system 2 with DC input power 1 as input
AC power is supplied at commercial frequencies. The grid-connected inverter roughly divides the input voltage Vin into the system voltage VAC.
A boost converter 3 for boosting to a higher voltage, an intermediate-stage capacitor 4 of several hundred μF or less for removing high-frequency components of the boosted voltage, and a full-bridge for controlling the voltage of the intermediate-stage capacitor 4 to generate an output current The step-up converter 3 comprises an input capacitor for smoothing the voltage of the input power supply 1, a DC reactor 6 for storing and releasing energy, and two switching elements QB and Q
Consists of F In addition, full bridge inverter 5
Has a four-element configuration and comprises an output reactor 7 for smoothing the output current Io and an output capacitor 8.

The system interconnection inverter control device 15 includes a DC reactor current command value generating means 9 as in the prior art.
Hysteresis width generating means 10 and command value adding means 11
, A command value subtracting unit 12, a DC reactor current detecting unit 13, and a hysteresis comparator 14, and an input voltage detecting unit 16 for detecting an input voltage Vin from the input power supply 1.

The operation of the above configuration will be described.
The voltage of the intermediate stage capacitor 4, that is, the intermediate stage voltage VM
Must be at least several tens of volts higher than the system voltage VAC to inject AC power into the system 2.
For example, when the input voltage Vin is DC 200V and the system voltage VAC is AC 200V, the peak of the system voltage VAC becomes 4
The input voltage Vin is boosted during a period of up to 5 ms, and is not boosted during a period in which the absolute value of the other system voltage VAC is sufficiently smaller than the input voltage Vin. Further, since the capacitance of the intermediate-stage capacitor 4 is small, it is not smoothed at a low frequency. Therefore, the ON time is modulated to maintain the difference from the system voltage VAC within about several tens of volts.

At this time, the system interconnection inverter control device 1
5 is a DC reactor current detecting means 13 for detecting a DC reactor current and an input voltage detecting means 16
, The input voltage Vin is reduced to, for example, about 100 V DC, the DC reactor current command value is not changed, and the hysteresis width generation means 1 is not changed.
By reducing the hysteresis width outputted from 0 to reduce the difference between the upper limit command value and the lower limit command value, the decrease in the operating frequency is minimized.

As described above, according to this embodiment, by changing the hysteresis width with respect to the change of the input voltage, the fluctuation of the operating frequency is suppressed, and the noise caused by the operation in the audible range due to the decrease of the input voltage. It is possible to provide a grid-connected inverter control device that can mitigate the phenomenon that the loss increases due to an increase in the operating frequency and conversely.

(Embodiment 2) Hereinafter, Embodiment 2 of a system interconnection inverter control device of the present invention will be described with reference to the drawings. This embodiment relates to claim 2.

FIG. 2 is a block diagram showing the configuration of this embodiment. The same components as those in the first embodiment are denoted by the same reference numerals, and a detailed description thereof will be omitted. This embodiment is different from the first embodiment in that the system interconnection inverter control device 15
The correction hysteresis width generating means 17 is provided, and the hysteresis width is multiplied by the input voltage Vin to generate a stepless variable correction hysteresis width.

The operation of the above configuration will be described.
The input voltage Vin detected by the input voltage detecting means 16
And the hysteresis width generated by the hysteresis width generating means 10 are multiplied by the corrected hysteresis width generating means 17 to generate a corrected hysteresis width, and the command value adding means 11 and the command value subtracting means 12 convert the DC reactor current command value into An upper limit command value and a lower limit command value are generated by adding and subtracting the correction hysteresis width, and the DC reactor current detected by the DC reactor current detection means 13 is compared with the upper limit command value and the lower limit command value by a hysteresis comparator 14, The two switching elements QB and QF of the boost converter 3 perform switching alternately. This correction hysteresis width is large when the input voltage Vin is large and small when the input voltage Vin is small.
The correction is performed so that the operating frequency is substantially constant with respect to the fluctuation of the input voltage Vin.

As described above, according to this embodiment, the change in the operating frequency of the boost converter can be constantly reduced by correcting the hysteresis width steplessly with respect to the change in the input voltage, so that noise and loss can be reduced. It is possible to provide a grid-connected inverter control device capable of minimizing the increase in the power supply.

[0026]

According to a first aspect of the present invention, there is provided a grid-connected inverter including a DC reactor and two switching elements, and a boost converter for boosting an input voltage from a DC input power supply. The system interconnection inverter control device for controlling the DC reactor current of the reactor adds or subtracts a hysteresis width to / from the DC reactor current command value to generate an upper limit command value and a lower limit command value of the DC reactor current command value. Is variable in accordance with the input voltage, by controlling the system interconnection inverter control device, it is possible to suppress fluctuations in the operating frequency and to maintain the operating frequency substantially constant, and to increase noise due to operation in the audible range due to the decrease in the input voltage. On the contrary, it is possible to alleviate the phenomenon that the operating frequency increases and the loss increases.

According to a second aspect of the present invention, an upper limit command value and a lower limit command value of a DC reactor current command value are generated as a correction hysteresis width using a value obtained by multiplying a fixed hysteresis width by an input voltage. The system interconnection inverter control device according to item 1 allows the hysteresis width to be steplessly changed and the operation frequency to be steplessly corrected in the direction in which the operating frequency is always constant, and a design that minimizes noise and loss increases. It becomes possible.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a system interconnection inverter control device according to a first embodiment of the present invention;

FIG. 2 is a block diagram illustrating a configuration of a system interconnection inverter control device according to a second embodiment of the present invention;

FIG. 3 is a block diagram showing a configuration of a conventional grid-connected inverter control device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Input power supply 2 system 3 Boost converter 4 Intermediate stage capacitor 5 Full bridge inverter 6 DC reactor 7 Output reactor 8 Output capacitor 9 DC reactor current command value generating means 10 Hysteresis width generating means 11 Command value adding means 12 Command value subtracting means 13 DC Reactor current detection means 14 Hysteresis comparator 15 Grid-connected inverter control device 16 Input voltage detection means 17 Correction hysteresis width generation means QB, QF Switching element Vin Input voltage VAC System voltage VM Intermediate stage voltage Io Output current

Continuing from the front page (72) Inventor Takaaki Okude 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. Reference) 5G066 HA30 HB05 5H007 AA01 AA08 AA17 BB07 CA01 CB04 CB05 CC03 CC12 DB01 DC02 DC05 5H420 BB13 CC03 DD03 EA11 EA45 EB01 EB16 EB39 FF03 FF04 FF22

Claims (2)

[Claims] 1. A system interconnection inverter having a boost converter that includes a DC reactor and two switching elements and boosts an input voltage from a DC input power supply.
The system interconnection inverter control device for controlling the DC reactor current of the DC reactor, when generating an upper limit command value and a lower limit command value of the DC reactor current command value by adding and subtracting a hysteresis width to the DC reactor current command value, A system interconnection inverter control device in which a hysteresis width is variable according to the input voltage. 2. The system interconnection inverter according to claim 1, wherein an upper limit command value and a lower limit command value of a DC reactor current command value are generated as a correction hysteresis width using a value obtained by multiplying a fixed hysteresis width by an input voltage. Control device.