JP3134301B2 - AC power supply - Google Patents

Description

The present invention relates to an AC power supply such as an uninterruptible power supply (hereinafter abbreviated as UPS) and a fuel cell power generation system.

[Conventional technology]

FIG. 12 shows a typical configuration of a conventional UPS. In the figure, a charger (3) converts electric power of a commercial power supply (5) into DC, and supplies DC power to a voltage source inverter (1) while charging a battery (2). The inverter (1) converts the DC power into an AC voltage with less low-order harmonics,
The power is converted into a sine wave AC power through a filter including the reactor Ls and the capacitor Cp, transformed into a voltage suitable for the load by the transformer T2, and supplied to the load (4). Usually, the load of the UPS such as a computer is insulated from the power supply side in order to prevent noise, and then, in many cases, a dedicated ground is taken. The transformer T2 needs not only the voltage adjustment but also the insulation function.

Although the transformer T1 on the voltage side is often omitted, the voltage on the DC side of the inverter is often determined from the economics of the inverter and the battery, so that the output DC voltage of the charger (3) is appropriate. In many cases, transformer T1 transforms the voltage and simultaneously insulates it. In this way, the conventional design improves
Since the S requires two transformers, its weight and size are large, making it difficult to reduce the size and weight of the UPS.

In order to solve this problem, a new scheme devised is a high-frequency intermediate link scheme shown in FIG. FIG. 13 is based on a block diagram of a conventional DC-AC power converter shown in IEEE PESC'88 Record, pp. 685-663, 1988,
This is a configuration of a UPS having the same functions as in FIG.
In the figure, an inverter (1) is a voltage-type inverter for generating a single-phase rectangular wave of f1 = 10 kHz, for example, and its output is provided to a cycloconverter (6) after being insulated by a transformer T2. The cycloconverter (6) converts the electric power of the frequency f1 into electric power of, for example, f3 = 60 Hz, converts the electric power into a sine wave through a filter including the reactor Ls and the capacitor Cp, and supplies the sine wave to the load. In this method, the transformer T2 can be designed at a frequency of 10 kHz, so that the size and weight of the transformer can be extremely reduced. However, the charger part requires a transformer T1 having a commercial power supply frequency f2 as in FIG.

A further developed system to improve this is shown in FIG. This focuses on the fact that the DC / AC converter in FIG. 13 can operate reversibly, and applies the same high-frequency intermediate link method to the charger. However, this method can reduce the size of the transformer, but requires two cycloconverters and two inverters between the commercial input and the output, which lowers the efficiency and increases the price of the converter. Therefore,
Although the method shown in Fig. 14 was possible in principle, it was of little practical value in terms of economy and efficiency.

Undeveloped to solve this shortcoming is Un
ited States Patent Patent Number 4719550 “UNINTER
RUPTIBLE POWER SUPPLY WITH ENERGY CONVERSION AND E
NHANCEMENT "This is a method of coupling input and output without using DC voltage as shown in Fig. 3. This method uses energy from commercial power supply, energy from battery, and energy from load all at the same frequency f1. The number of converters required is reduced by forming a star configuration so that power is exchanged at a frequency of f1 by the AC / AC converter (12). And supplies it to a high-frequency transformer (11). Between the high-frequency transformer (11) and the battery (2),
There is a second reversible converter (9), which converts the power of the battery (2) into DC / AC and supplies it to the high-frequency transformer (11). The AC / AC converter (15) is connected to the high-frequency transformer (1
The power of 1) is converted to power of frequency f3 and supplied to the load (4).

[Problems to be solved by the invention]

The conventional AC power supply is configured as described above,
This eliminates the input and output commercial frequency isolation transformers. However, in this configuration, the insulation function, which is the function of the commercial frequency isolation transformer, is sufficiently satisfied, but for the other function, the transformer function, the power converter is directly connected to the input / output power supply side. Therefore, the voltage cannot be changed without changing the design specifications of the power converter.

The present invention has been made to solve the above-described problems, and can easily cope with a change in the specification of input / output voltage, and can output various voltages and frequencies with one device, and can load various loads. At the same time.

[Means for solving the problem]

In the AC power supply according to the present invention, a large number of power converters are connected using a high-frequency insulating transformer, and the power converters are individually provided with current controllers so that the power converters can be connected in series or in parallel, and are connected in series or in parallel. It is a voltage controller of a power converter integrated into one.

[Action]

The AC power supply device according to the present invention is, for example, 100V, 200V,
A wide variety of electric power such as 50Hz, 60Hz, and 400Hz can be output from one device, and n can be output using the same n power converters.
This is an AC power supply that supplies twice the voltage and power.

(Example of the invention)

Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 to 5 show a first embodiment of the present invention, and FIG. 1 is a block diagram of the first embodiment. (2) battery, (16) capacitor, (17) inverter, (18) bus connected to the output of inverter (17), (19) AC filter,
(20) is a cycloconverter, (21) is a high-frequency isolation transformer, (22) is a bus connected to the output of the cycloconverter (20), and (23) is connected to the secondary winding of the high-frequency isolation transformer (21). The bus, (24) is a cycloconverter, (25) is an AC filter connected to the output side of the cycloconverter (24), (101) is a DC voltage controller that performs DC voltage control, and (102) is the input current of this device. Current control circuit to control, (103) output voltage control circuit, (1)
04) is a current control circuit for controlling the output current of this device.

FIG. 2 is a simplified diagram showing the internal configuration of the inverter (17), in which four switching elements (transistor, MOSFET,
IGBT, Bi-MOS, SIT, etc.), Q1-Q4 and four diodes D1
~ D4.

Fig. 3 shows an AC filter (19) and a cycloconverter (2
A simplified view showing the internal structure of 0), AC filter reactor L _F and the capacitor C _F, cycloconverter (20) is composed of four bidirectional switches S1 to S4.

Fig. 4 shows a DC voltage control circuit (10
It is a block diagram of 1). (105) is a DC voltage command generator, (106) is a DC voltage detector, (107) is a sine wave oscillator, (108) is a voltage controller, and (109) is a limiter.

FIG. 5 is a block diagram of a current control circuit (102) for controlling an input current according to the present invention. (110) is a current detector,
(111) is a current controller, and (112) is a switching signal generation circuit.

FIG. 6 is a block diagram of an output voltage control circuit (106) for controlling an output voltage according to the present invention. (113) is an output voltage command generator, (114) is an output voltage detector, (115) is an output voltage controller, and (116) is a limiter.

Next, the operation of the first embodiment shown in FIG. 1 will be described with reference to FIG. The inverter (17) in FIG. 1 has a configuration as shown in FIG. 2, but does not perform voltage control here, and its polarity is synchronized with a positive peak of a carrier signal having a frequency f1 as a reference of the device. The voltage of the battery (2) as shown in the middle part of FIG. 7 is obtained by using the switching signals Q1 and Q4 driven by the square wave switching signal having the changing duty ratio of 50% and the driving signals Q2 and Q3. The corresponding square wave is supplied to the bus (18). This inverter (17) fixes its frequency and establishes the voltage and frequency of the bus (18) as a reference for the entire system. In addition,
In FIG. 7, (Sc) is a carrier signal, and (I _I ) is a current command.

Next, an AC filter (19) and a cycloconverter (20)
Thus, the input voltage of the commercial frequency f2 is converted into the same frequency f1 as that of the inverter (17). Where this AC filter (19)
When the converter and the cycloconverter (20) are considered as one converter, if the two input terminals of these converters are connected in series between the output terminals of the AC power supply, the voltage applied to one converter becomes the AC power supply voltage. Half of Therefore, if n units are connected in series, the voltage applied to one converter becomes 1 / n, and this converter can be set with a low withstand voltage and can be transformed without an input transformer. In addition, the output side of this converter is isolated by an isolation transformer, and its voltage is controlled by an inverter (1
Since it is established in 7), individual converters can be controlled independently and converters can be easily unitized. Then, the operation of this cycloconverter (20) is described next with reference to FIGS.
This will be described with reference to FIGS. 5, 5 and 7.

The cyclo converter (20) has a configuration as shown in FIG. The switching elements S1 to S4 include a DC voltage control circuit (101) shown in FIG. 4 and a current control circuit (10
In 2), it is controlled to keep the DC voltage constant. First, the battery voltage Vd detected by the DC voltage detector (106) is subtracted from the DC voltage command V ^* d output from the DC voltage command generation circuit (105), and the voltage difference ΔV is output to the sine wave oscillator (107). I do. This sine wave oscillator is simply ΔVS
The signal INθ is oscillated. Here, if a PLL (Phase Locked Loop) circuit is incorporated in the sine wave oscillator (107) so that this phase is synchronized with the input voltage, the input power factor 1 can be controlled. Next, proportional or proportional-integral control is performed by the voltage controller (108) to generate an input current command I ^* i, which is input to the limiter (109). This limiter (109) is a DC voltage
This is to suppress output of an overcurrent command that exceeds the current capacity of the switching element when Vd greatly fluctuates. Next, in FIG. 5, first, the input current command I ^* i output from the DC voltage control circuit (101) is input,
The input current Ii detected by the current detector (110) is subtracted from the value, proportionally controlled by the current controller (111), and the result is again output as an input current command to the switching signal generation circuit (112), and the switching signal is output. Generation circuit (112)
Drives the four bidirectional switches of the cycloconverter (20). In response to this switching command, the switches S1 to S4 are repeatedly turned on and off as shown in FIG. 7. Here, the voltage output by the cycloconverter (20) shown at the bottom of FIG. 7 will be described by dividing it into periods t1 to t4. .

Period t1: S2, S4 ON, S1, S3 OFF, reactor Lf charging period Period t2: S1, S4 ON, S2, S3 OFF reactor Lf discharging period Period t3: S1, S3 ON, S2, S4 OFF Reactor Lf charging period Period t4: S2, S3 are ON, S1, S4 are OFF Reactor Lf discharging period As a result, zero voltage is output during the charging period of reactor Lf, and the voltage whose amplitude is clamped to DC voltage is output during the discharging period. Output.

Therefore, the energy exchange of this whole device is AC
When the reactor Lf of the filter (19) is in the charging period, energy is stored in the reactor Lf from the AC power supply, and energy is supplied to the load from the capacitor (16). During discharging, the energy of the reactor Lf is stored in the capacitor (1
6) or supplied to the load. Here the high-frequency transformer (2
The primary and secondary voltages in 1) are duty-free, regardless of the charging and discharging of reactor Lf, if the capacitor (16) is large enough.
A square wave with a constant amplitude at 50%.

Next, the power converter on the load side of this device will be described. The cycloconverter (24) receives the power of the voltage frequency f1 from the high-frequency insulating transformer via the bus (23),
Convert to commercial frequency. Next, power is supplied to the load after being filtered by the AC filter (25). Here, if the cycloconverter (24) and the AC filter (25) are considered as one converter like the input side, the input As with the side, if the output terminals of the two converters are connected in series to the load, the AC voltage output from one converter will be half.
Also, if n units are connected in series, the ratio becomes 1 / n, which is as advantageous as the converter on the input side.

Next, this cycloconverter (24) is shown in FIGS.
This will be described with reference to the drawings. The cycloconverter (24) and the AC filter (25) have a configuration in which the input side and the output side in FIG. 3 are turned upside down. The current control circuit (104) is exactly the same as the input-side current control circuit (102). The output voltage control circuit (103) is shown in FIG. In FIG. 6, first, an output voltage command V ^* _L is output from the output voltage command generation circuit (113). The output voltage detection circuit (114) detects the load voltage and, at the same time, divides the load voltage by the number of converters in series with the load and sets the result as the voltage detection value per unit. Next, the output of the output voltage detector (114) is subtracted from the output voltage command V ^* _L , and a proportional or proportional-integral control is performed by the voltage controller (115) to output an output current command.
6) Limit the overcurrent command. The output of the output control circuit (103) is input to the current control circuit (104),
Since the current control circuit (104) is the same as the input side, the description is omitted. By the above operation, the cycloconverter (24) performs switching with the switching pattern as shown in FIG. 8 with respect to the output voltage of the inverter (17) as shown in FIG. Here, the relationship between the input voltage of the cycloconverter (24) and the switching is as shown in the following table.

If pulse width control is performed using the relationship shown in the above table,
The output voltage of the cycloconverter (24) as shown in the figure is obtained. Furthermore, if the output of this cycloconverter (24) is filtered by an AC filter (25),
A sine wave with f3 is obtained.

Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 9 shows a configuration in which the input terminals of the converter on the input side are connected in parallel between the output terminals of the AC power supply, and the output terminals of the converter on the output side are connected in parallel. The components are exactly the same as those in FIGS. 1 to 6 showing the first embodiment. Next, the operation of the above-described second embodiment will be described. If two converters are connected in parallel to the AC power supply, the input current is shunted and the capacity of the converter is reduced by half. Here, two converters are connected to one current control circuit (10
When the control is performed in 2), the shunt current is unbalanced due to the variation in the characteristics of the switching signal generating circuits of the individual. Therefore, it is necessary that each of the converters has a current control circuit (102) and controls the current to balance the current. Further, when the DC voltage control circuit (101) is provided in each of the converters, the shunt is unbalanced due to the variation of the current command output from the DC voltage control circuit (101). Therefore, it is necessary to control the converters connected in parallel by one voltage control circuit (101) so that the current command is the same in any current control circuit (102). The same applies to the converter (24) on the load side.

As described above, if n converters each having a current control circuit are controlled by a command of one voltage control circuit, the current flowing in one converter becomes 1 / n when the n converters are connected in parallel. By adjusting the number of units connected in parallel, it is possible to easily cope with an increase or decrease in load.

Next, a third embodiment of the present invention will be described with reference to FIG. This circuit component is the same as that of the first embodiment shown in FIGS. 1 and 2, and its function is to connect the input terminal of the converter on the input side between the output terminals of the AC power supply in series or in parallel, respectively. The output terminals of the converter on the output side are connected in series or in parallel, respectively, so that the first embodiment and the second embodiment can be used together by switching a switch. In FIG. 10, (A) when both the input side Si and the output side So are turned off, (a) When two converters are in-phase controlled, the voltage and power twice as large as one converter are: It is obtained between input and output AC.

(B) When the two converters are controlled with a phase shift of 120 °, the voltage of one converter is set to the line voltage, and the three-phase power of the V connection having twice the power is used for input and output A, B, Obtained during C.

(B) When Si on the input side and So on the output side are both turned on and two converters are controlled in opposite phases, twice the power can be obtained at the same voltage as one converter.

As described above, three patterns can be output by switching between the switch and the control.

 Next, a fourth embodiment will be described with reference to FIG.

In FIG. 11, (27), (29), and (31) denote cycloconverters that perform pulse width modulation, and (28), (3)
(0) and (32) are AC filters, (117) and (118) are output voltage control circuits and current control circuits for controlling the voltage and current of the cycloconverter (27), respectively, and (119) and (120) are cyclotrons, respectively. Output voltage control circuit and current control circuit for controlling the voltage and current of the converter (29), (121) and (122)
Are an output voltage control circuit and a current control circuit for controlling the voltage and current of the cycloconverter (31), respectively.

Next, the operation will be described. For example, the AC power supply on the input side is a single-phase 200V, 60Hz. First, the cycloconverter (20) of the input converter converts the high frequency to f1 (f1 is considerably higher than the maximum frequency on the output side), and supplies the energy to the battery and the load. The voltage of the high-frequency transformer (26) is established by the inverter (17) as in the first embodiment, and the converter on the load side performs pulse width control in synchronization with this voltage. Here, for example, the cycloconverter (27) includes an output voltage control circuit (11
The value is output by the 100V, 60Hz voltage command created in 7). The cycloconverter (29) outputs the value according to a voltage command of 200V, 400Hz generated by the output voltage control circuit (119). In addition, cyclo converter (31)
If the AC filter (32) is composed of three phases, the voltage is output by a three-phase 200V, 60Hz voltage command generated by the output voltage control circuit (121).

〔The invention's effect〕

As described above, according to the present invention, a large number of power converters each having a current control circuit are connected by one high-frequency transformer, and can be connected and operated in series and parallel.
It can easily support various input / output specifications.
It is possible to configure a highly flexible and multifunctional power supply system, for example, such that power can be simultaneously supplied to a variety of loads on a stand.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention, FIG. 2 is a block diagram of a DC voltage control circuit for controlling a DC voltage in each embodiment of the present invention, and FIG. 3 is each embodiment of the present invention. FIG. 4 is a block diagram of an output voltage control circuit for controlling the DC voltage of each embodiment of the present invention, and FIG. 5 is a block diagram of an output voltage control circuit of each embodiment of the present invention. FIG. 6 is a block diagram of a current control circuit for controlling an input current, FIG. 6 is a block diagram of an output voltage control circuit for controlling an output voltage of each embodiment of the present invention, and FIG. 7 is an input of a first embodiment of the present invention. 8 is a switching timing diagram of the power converter on the output side, FIG. 8 is a switching timing diagram of the power converter on the output side according to the first embodiment of the present invention, and FIG. 9 is a block diagram showing a second embodiment of the present invention. FIG. 10 shows a third embodiment of the present invention. FIG. 11 is a block diagram showing a fourth embodiment of the present invention, FIG. 12 is a block diagram of a conventional power converter using a commercial frequency insulating transformer for input and output, and FIG. Fig. 12 is a block diagram of a conventional power converter in which the output-side insulating transformer is replaced with a high-frequency insulating transformer. Fig. 14 is a conventional power converter in which both the input and output insulating transformers in Fig. 12 are replaced by high-frequency insulating transformers. FIG. 15 is a block diagram of a conventional power converter in which input, output, and battery are insulated from each other by a single high-frequency insulating transformer. (1), (7), (9), (17) ... Inverter,
(2) ... battery, (3) ... rectifier, (4) ...
Load, (5) ... AC power supply, (6), (8), (12),
(15), (20), (24), (27), (29), (31) ...
Cycloconverter, (10), (13), (14), (1
8), (22), (23) ... bus, (11), (21), (2
6) High frequency insulation transformer, (16) Capacitor,
(19), (25), (28), (30), (32) ... AC filter. (101) DC voltage control circuit (102), (104), (1
18), (120), (122) ... current control circuit, (103),
(117), (119), (121) ... output voltage control circuit, (1
05) DC voltage command generation circuit, (106) DC voltage detector, (107) Sine wave oscillator, (108), (115)
... voltage controller, (109), (116) ... limiter, (110) ... current detector, (111) ... current controller, (112) ... switching signal generation circuit, (113)
... Output voltage command, (114) output voltage command. In the drawings, the same reference numerals indicate the same or corresponding parts.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H02M 5/00-5/48

Claims (4)

(57) [Claims] An AC power source having a second frequency is input and converted to a first frequency higher than the second frequency.
A plurality of converter groups, a second converter capable of converting reversible power into a first frequency with a DC power supply as an input, the first plurality of converter groups and a second converter And a third plurality of converter groups that are supplied with power from at least one of the first and second converters and convert the power into AC power of a third frequency. An input terminal of each converter constituting the first converter group is the AC power supply. And an output terminal of each of the converters constituting the third converter group is connected in series, between the output terminals of the AC power supply. 2. An AC power supply having an input of an AC power supply having a second frequency and converting the AC power to a first frequency higher than the second frequency.
A plurality of converter groups, a second converter capable of converting reversible power into a first frequency with a DC power supply as an input, the first plurality of converter groups and a second converter A plurality of converter groups that are supplied with power from at least one of them and convert into AC power of a third frequency, and currents that respectively control currents output from the converters that form the third converter group. A controller, and a voltage controller for commonly controlling a voltage output from each converter constituting the third converter group, wherein an input terminal of each converter constituting the first converter group is An AC power supply device connected in parallel between output terminals of an AC power supply, and having output terminals of the converters constituting the third converter group connected in parallel. 3. An AC power supply having a second frequency as an input and converting the AC power into a first frequency higher than the second frequency.
A plurality of converter groups, a second converter capable of converting reversible power into a first frequency with a DC power supply as an input, the first plurality of converter groups and a second converter And a third plurality of converter groups that are supplied with power from at least one of them and convert the AC power into a third frequency AC power, and an input terminal of each converter that forms the first converter group is an output terminal of the AC power supply. Means for changing the connection so that they are connected in series or in parallel between the terminals, and changing the connection so that the output terminals of the converters constituting the third converter group are connected in series or in parallel, respectively AC power supply comprising: 4. The AC power supply according to claim 3, wherein a polyphase AC is output from the third converter group by changing an output phase of the converters constituting the first and third converter groups. apparatus.