JPH11178352A - Dc/ac power conversion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a device compactly and inexpensively with the no need for maintenance, without the use of an uninterruptible power supply device for a low-voltage DC control power supply of a conversion part for converting a high-voltage DC power supply of a solar cell power supply or the like into an AC power supply. SOLUTION: A first DC/DC converter 15 for stepping down a DC power supply at the DC input side of a conversion part 6 and for outputting a high-voltage, a primary stepdown power supply from the control power supply of the conversion part 6, and a second DC/DC converter 17 for forming a control power supply by stepping down the primary step-down power supply, are provided at a control power supply part 14. Then, the converter 15 is formed by a semiconductor switch element that is self-biased through the partial voltage of the DC power supply and interrupts the DC power supply, a rectification smoothing means for forming the primary step-down power supply by rectifying and smoothing the interrup output of the element, and a control means that is operated due to the supply of the output of the converter 17 and turns on/off the bias of the semiconductor switch element, so that the primary step-down power supply is a set voltage within the input voltage range of the converter 17.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a D-type inverter for an inverter for a distributed power supply connected to an electric power system.
The present invention relates to a C / AC power converter, and more particularly to the formation of a control power supply.

[0002]

2. Description of the Related Art Conventionally, a private power generation facility as a distributed power supply connected to a power system is generally formed as shown in FIG. 4, and DC power supplies such as a solar cell power supply 1 and a storage battery power supply 2 are used to prevent backflow. A so-called stationary converter 6 of a DC / AC power converter 5 as an inverse converter via diodes 3 and 4
Supplied to

At this time, the DC power source fluctuates depending on the state of solar radiation and the like, but has a high voltage of about 400 to 600 volts at the maximum.

The converter 6 comprises a bridge circuit (main circuit) for reverse conversion of the power semiconductor and an operation control circuit (drive circuit) for controlling the switching operation of this circuit. Operated by one or more low-voltage control power supplies of several volts or tens of volts,
The DC power supply is converted into an AC power supply having a system voltage of 100 to 200 volts synchronized with the system power supply 8, and the AC power supply is supplied to the load 10 via the interconnection switch 9.

By the way, in consideration of the fact that the voltage on the AC output side of the converter 6 is lower than that on the DC input side, conventionally, power is supplied to the control power supply 7 on the AC output side of the converter 6, for example, the interconnection switch 9. From the system side (load side).

At this time, a so-called uninterruptible power supply (UP) is used in order to prevent the power supply from being lost due to a system power failure.
S) 11 is used, and the power supply device 11 always supplies an AC power supply on the system side of the interconnection switch 9 to the control power supply unit 7, and performs an AC power supply based on a built-in battery energy or the like at the time of a system power failure or the like. The backup power is supplied to the control power supply unit 7.

The control power supply unit 7 is, for example, an AC / DC converter (inverter) 1 having a step-down function for each control power supply.
2, the converter 12 steps down the AC output of the uninterruptible power supply 11 and converts it to DC to form a control power supply for each voltage.

[0008]

In the case of the conventional apparatus shown in FIG. 4, a large, heavy, and expensive uninterruptible power supply 11 incorporating a storage battery and the like is required in order to form a control power supply for the converter 6. There is a point.

In addition, the uninterruptible power supply 11 has a short service life of about three years, requires frequent maintenance work such as so-called battery replacement, and has a problem that maintenance costs (running costs) are increased.

Since the DC power supplied to the converter 6 is not affected by an accidental power failure or the like of the system, the DC power is converted into a DC / DC signal, and the AC power supply 11 is omitted. It is conceivable to obtain a control power supply.

However, the DC power supplied to the converter 6 has a voltage of about 400 to 600 volts, and is capable of converting such a high voltage into a commercially available general power having an input voltage range of less than 400 volts. A single DC / DC converter (hereinafter referred to as a commercial converter) cannot reduce the voltage to a low voltage of several volts to several tens of volts, and the control power (operating power) of the commercial converter must be supplied from another DC power supply There is.

It is an object of the present invention to form a control power supply for a converter by using a commercially available converter and using a compact, inexpensive and easy-to-maintain configuration without using an uninterruptible power supply or the like. .

[0013]

In order to solve the above-mentioned problems, a DC / AC power converter of the present invention forms a DC control power supply having a lower voltage than a DC power supply such as a solar cell power supply or a storage battery power supply. A first DC / DC converter for stepping down the DC power supply and outputting a DC primary step-down power supply having a higher voltage than the control power supply to a control power supply unit that supplies power to the conversion unit; A second DC that forms the control power supply
A first DC / DC converter provided in an energizing path of the DC power supply, self-biased by a divided voltage of the DC power supply, and interrupting the DC power supply. Rectifying and smoothing means for rectifying and smoothing the intermittent output of the power supply to form a primary step-down power supply;
The output of the second DC / DC converter is supplied to operate, and the bias voltage of the semiconductor switch element is turned on and off so that the primary step-down power supply has a set voltage within the input voltage range of the second DC / DC converter. It is formed by controlling means.

Therefore, the high-voltage DC power supply on the DC input side of the converter is stepped down in two stages by the first and second DC / DC converters to form a DC control power supply for the converter.

In this case, the input of the second DC / DC converter is less than 400 V by the first DC / DC converter, so that the second DC / DC converter can be formed by an inexpensive commercial converter or the like.

In addition, the first DC / DC converter is supplied with the low-voltage output of the second DC / DC converter as a control power supply, and operates without supplying control power from another power supply device or the like.

Since the DC power supply on the DC input side of the conversion unit is used, the control power supply of the conversion unit is not lost even if an accidental power failure or the like of the system on the AC output side of the conversion unit occurs.
A large, expensive, and frequent maintenance work such as a backup power supply using a storage battery, such as a conventional uninterruptible power supply, is unnecessary. It is formed.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS. The DC / AC power conversion device 13 in FIG. 1 includes a control power supply unit 14 in a converter configuration instead of the control power supply unit 7 in a so-called inverter configuration of the conventional device 5 in FIG.

The control power supply unit 14 includes a solar cell power supply 1 and a storage battery power supply 2 on the DC input side of the conversion unit 6.
A DC power supply reaching about 0 volts is stepped down by a first DC / DC converter 15 as a so-called down converter, and the output (primary step-down power supply) of the converter 15 is passed through an OR gate diode 16 to one or a plurality of 2
, And further lowers the primary step-down power supply to form each low-voltage control power supply of several volts to several tens of volts. Supply.

The first DC / DC converter 15
Is composed of a main circuit section 18 and a control section 19 as control means shown in FIG. 2. The main circuit section 18 inserts the DC power supply of the voltage Vin ₁ supplied between the input terminals Ia and Ib into the current path. was interrupted by the switching of FET20 as a semiconductor switching element, the intermittent output diode 21, rectified by the rectifying and smoothing means of the reactor 22 and the smoothing capacitor 23 smoothes, voltage Vout ₁ is stepped down to the reference voltage Vref later 1 Output terminal O for next step-down power supply
a and Ob to the second DC / DC converter 17.

Further, since the control unit 19 to the voltage Vout ₁ below the reference voltage Vref by the feedback control, a predetermined reference voltage Vref of the voltage Vout ₁ and the reference power supply unit 24 is computed by a subtracter 25, the difference [Delta] V ( = V
The out ₁ -Vref) signal via a so-called PID processing circuit 26 is supplied to the pulse generation section 27, the creating unit 2
7, a pulse signal (PWM pulse signal) whose pulse width changes in proportion to the difference ΔV is formed, and the pulse signal turns on and off the bias intermittent switch 28 provided between the gate g and the drain d of the FET 20. Turn off.

By the way, an FET is connected between the input terminals Ia and Ib.
Voltage dividing resistors 29 and 30 forming a bias circuit of 20 are provided in series.
Forming a bias resistor of the drain d, FET 20 by the partial pressure of the voltage Vin ₁ is self-biased at a partial pressure of the DC power supply.

[0023] Then, the voltage Vin ₁ rises FET2
When the voltage between the gate g and the drain d becomes equal to or higher than a predetermined ON voltage, the FET 20 is turned ON by the self-bias.

When the FET 20 is turned on, the switch 28
Is turned on and off, the bias voltage of the FET 20 is interrupted, and the FET 20 switches according to the intermittent.

On the other hand, assuming that the input voltage range of the second DC / DC converter 17 is a voltage _VH to a voltage _VL ( _VH > _VL ) shown in FIG. The reference voltage Vref is set to an appropriate voltage therebetween.

At this time, the first DC / DC converter 1
To reduce the 5 buck burden, the reference voltage Vref is preferably set to minimize a voltage close to the voltage V _H.

[0027] Then, when the voltage Vin ₁ which varies in a range of for example 0 volts to 750 volts, as indicated by the solid line in FIG. 3 (a), between the Vin ₁ ≦ Vref switch 28
There was off, predetermined ON voltage during which the voltage Vin ₁ wherein, for example, equal to or higher than the voltage V _L, FE in FIG (b)
As shown in the operation state of T20, the self-bias causes the FET 20 to change from off to on.

When the FET 20 is turned on, the first DC
The / DC converter 15 changes from the “cut-off state” to the “through-pass state” as shown in the operation state of FIG. 3 (c), and is apparent from the change of the output voltage Vout ₁ indicated by the broken line in FIG. 3 (a). First DC / DC converter 15
Outputs the DC power without stepping down and outputs the second DC power.
/ DC converter 17.

Next, when Vin ₁ > Vref, the switch 28 is turned on and off in accordance with the difference ΔV.
The switching of the FET 20 to the switching operation of FIG.
The C / DC converter 15 is in the state of constant output step-down control shown by (c) in FIG.
The voltage is reduced to ef and supplied to the second DC / DC converter 17.

The reference voltage Vref is set to about 30
By setting the voltage to 0 volt, the high-voltage DC power supply of 400 volts or more on the DC input side of the conversion unit 6 is stepped down to a voltage within an input voltage range of less than 400 volts of a commercially available general DC / DC converter. To the second DC / DC converter 17.

Therefore, the second DC / DC converter 1
7 can each be formed by a commercial converter.

Then, the second DC / DC converter 17
Reduces the voltage of the primary step-down power supply of the voltage Vin ₂ (≒ Vout ₁ ≦ Vref) to several volts or several tens of volts, and a voltage Vo of, for example, 24 volts indicated by a one-dot broken line in FIG.
ut ₂ , and supplies the control power to the converter 6.

The DC output of the voltage Vout ₂ of the second DC / DC converter 17 is supplied to the control unit 19 of the first DC / DC converter 15 as a control power, and the control power supplies the first DC / DC converter. The operation of the DC converter 15 is controlled, and there is no need to separately prepare a control power supply for the first DC / DC converter 15.

The second DC / DC converter 17
Operate with a control power supply formed by stepping down a primary step-down power supply.

With the above configuration, the DC power supply on the DC input side of the conversion unit 6 is stepped down to form a control power supply required for the conversion unit 6. It does not disappear due to the use of a storage battery such as an uninterruptible power supply. A large, heavy and expensive backup power supply is unnecessary, and the device can be formed small, light, and inexpensively. Is also greatly reduced.

The symbol in FIG.
And (c) of FIG.
Indicates a through-pass state of the first DC / DC converter 15,
Indicates a shut-off state.

Next, in this embodiment, the first
In order to further improve the reliability and the like by preventing the control power supply from being lost even if a failure of the DC / DC converter 15 occurs, as shown in FIG. The DC / DC converter 3 converts the DC power into DC power to form a backup DC power supply. When the output of the first DC / DC converter 15 is lost, the AC / DC converter 3
The first DC power supply for backup is supplied to the second DC / DC converter 17 via the diode 32 for OR gate.

Since the AC / DC converter 31 does not perform a step-down operation, a commercially available AC / DC converter for electric power is used.
It can be formed at low cost.

The supply of the backup power causes the input voltage Vin of the second DC / DC converter 17 to change.
₂ is actually the voltage Vout _{1 of} FIG.
Even if it is lower than ref, it hardly decreases.

In the above embodiment, the semiconductor switch element is the FET 20, but the semiconductor switch element may be a power transistor or the like.

In the FET 20, the drain d and the source s are provided between the terminals Ib and Ob on the ground side in consideration of the dielectric strength and the like. However, the semiconductor switch element such as the FET 20 is provided between the terminals Ia and Oa on the hot side. A drain d and a source s may be provided.

Further, the first DC / DC converter 15
The configuration and the like of the main circuit section 18 and the control section 19 are not limited to those of the above-described embodiment.

The present invention can be applied to DC / AC power converters of various distributed power supplies connected to a power system.

[0044]

The present invention has the following effects. The high-voltage DC power supply on the DC input side of the conversion unit 6 is stepped down in two stages by the first and second DC / DC converters 15 and 17 provided in the control power supply unit 14, and the DC low voltage of the conversion unit 6 is reduced. Can be formed.

In this case, the second DC / DC converter 1
7 is an inexpensive DC /
It can be formed by a DC converter or the like.

Moreover, the first DC / DC converter 15
Is supplied with a low-voltage output of the second DC / DC converter 17 as a control power supply, and operates without supplying control power from another power supply device or the like.

Since the DC power supply on the DC input side of the conversion unit 6 is used, the control power supply of the conversion unit is not lost even if an accidental power failure of the system on the AC output side of the conversion unit occurs. A large-sized, expensive, backup power supply that requires frequent maintenance work, such as an uninterruptible power supply, is not required, and a DC control power supply for the converter is formed by a small, inexpensive, and easy-to-maintain configuration. can do.

[Brief description of the drawings]

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

FIG. 2 is a detailed connection diagram of a part of FIG. 1;

3A is an explanatory diagram of a voltage change in FIG. 1, FIG. 3B is a timing chart of the FET in FIG. 1, and FIG.
FIG. 4 is an explanatory diagram of a state change of the DC / DC converter of FIG.

FIG. 4 is a block connection diagram of a conventional example.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 solar cell power supply 2 storage battery power supply 6 conversion unit 8 system power supply 14 control power supply unit 15 first DC / DC converter 17 second DC / DC converter 19 control unit 20 FET 21 diode 22 reactor 23 smoothing capacitor

Claims (1)

[Claims] 1. A DC / AC power converter that is connected to a power system, converts a DC power supply such as a solar battery power supply or a storage battery power supply into an AC power supply by a static converter and feeds the power to a load. A first DC for forming a lower-voltage direct-current control power supply and supplying power to the conversion unit; a first DC for stepping down the DC power supply and outputting a DC primary step-down power supply having a higher voltage than the control power supply / DC converter, and a second DC / DC converter for stepping down the primary step-down power supply to form the control power supply, wherein the first DC / DC converter is provided in a current path of the DC power supply. A semiconductor switch element that is self-biased by the divided voltage of the DC power supply and interrupts the DC power supply, and rectifies and smoothes the interrupted output of the semiconductor switch element to form the primary step-down power supply. The semiconductor switch element is biased such that the output of the second DC / DC converter is supplied and operates, and the primary step-down power supply has a set voltage within an input voltage range of the second DC / DC converter. A DC / AC power converter formed by control means for turning on and off a voltage.