JPH02159937A - Uninterruptible ac power source equipment - Google Patents

Abstract

PURPOSE:To reduce the size of an uninterruptible power source equipment by rectifying power of a commercial power source equipment and charging a floating cell thereby making the DC/DC converter of the uninterruptible power source equipment for producing AC power of commercial frequency through an output insulating DC/DC converter bilateral. CONSTITUTION:Power of an AC power source 1 is rectified 2 and employed for charging of a floating cell 3 and a load 6 is driven with AC power having predetermined frequency produced from a PWM inverter 5 through a DC/DC converter 7. The DC/DC converter 7 comprises a regenerative diode 13 and a regenerative switch 14 connected, respectively, in parallel with a primary main switch 11 and a secondary main diode 12 through an insulating transformer 8 thus exhibiting bilateral performance. Reactive power produced at the load 6 side is regenerated through the diode 13 to the power source by closing a switch 14 and opening a switch 11 according to load conditions. By such arrangement, the PWM inverter 5 is driven optimally at all times and abnormal voltage rise is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) In recent years, with the rapid development of semiconductor devices, information processing equipment using microcomputers has come into wide use. These devices are vulnerable to power outage accidents, and valuable information may be lost due to a momentary power outage. Therefore, in order to protect valuable information from power outage accidents, an AC uninterruptible power supply device is required that supplies a constant amount of power to the load even when the commercial power source is out of power. Further, as information equipment bodies are becoming smaller and more sophisticated with advances in integration technology, power supplies are also required to be smaller and more sophisticated. The present invention makes it possible to downsize and improve the performance of such an AC uninterruptible power supply by using a DC-DC converter capable of bidirectionally transmitting and distributing power within the AC uninterruptible power supply. It can be widely used as an uninterruptible power supply for information equipment.

(Prior art) AC uninterruptible equipment requires an inverter to convert from DC to AC, a transformer to insulate the load and battery equipment, etc. Conventionally, these devices have simple structures. Many low-frequency inverters and low-frequency transformers were used. However, due to recent demands for miniaturization of 11i EPJs, PWM inverters operating at high frequencies and DC-DC converters for load isolation are now being used as inverters for converting direct current to alternating current. FIG. 1 shows an example block diagram of an AC uninterruptible power supply using a typical PWM inverter and DC-DC converter. In this diagram, 1 is a commercial AC power supply, 2 is a rectifier, 3 is a battery, and 4 is a DC-D
C converter, 5 represents a PWM inverter, and 5 represents a load.

FIG. 2 shows a specific example of the DC-DC converter 4 in FIG. 1. In FIG. 0, 11 represents a switch, 12 a diode, 8 a high frequency transformer, and 9 an output capacitor. In the circuit of FIG. 2, energy is stored in transformer 8 when switch 11 is on. When the switch 11 is turned off, the energy of the transformer 8 is transmitted to the load side through the diode 12. Here, the input voltage is Ei,
The output voltage is EO, and the time the switch 11 is on is T on
, the off time is Toff, and the turns ratio between the primary winding and the secondary winding of the transformer 8 is 1:n, then a voltage EO expressed by the following equation is obtained at the output.

Eo=n −Ei−Ton/Toff Here, if T on/T off is adjusted appropriately,
The desired voltage EO is obtained.

However, the above input-output voltage relationship holds true only when power is continuously transmitted from the input side to the output side. The flow of power is blocked by diode 12, resulting in an increase in the voltage across output capacitor 9. For example, when a load with a low power factor or an induction motor is connected as the load 5, power is applied from the load side to the output terminal due to reactive power or the generation effect of the induction motor, and P
A high voltage may be generated at the input terminal of the WM inverter 5. Although FIG. 2 shows an example of a pack-boost type which is commonly used as a DC-DC converter, similar problems occur with other types such as a push-pull type and a forward type. For this reason, in the conventional technology, the capacity of the output capacitor 9 of the DC-DC converter is increased, or the DC-DC
It was necessary to solve this problem by connecting a dummy resistor to the output terminal of the C converter.

(Problem to be solved by the invention) However, with these methods, not only do elements such as resistors and capacitors become large, which impedes miniaturization of the power supply, but also they cannot completely prevent voltage increases. There have been problems such as the voltage having an adverse effect on the PWM inverter and causing output waveform distortion. The present invention eliminates the adverse effects that occur inside the power supply due to the power returned from such a load, and eliminates the large DC
- The purpose is to miniaturize the capacitor 9 and the like for the DC converter 4 in order to miniaturize and improve the performance of the power supply.

(Means for Solving the Problems) The present invention provides, as means for solving the above-mentioned problems,
Instead of the conventional DC-DC converter 4 in which power is transmitted only in one direction from the battery 3 to the PWM inverter 5, a DC-DC converter that can transmit power in both directions is used to effectively transfer power from the load to the battery. 3, the voltage generated inside the device is suppressed, the output waveform is improved, and the large capacitors and the like conventionally used to suppress voltage increases can be downsized.

FIG. 3 shows an example of a block diagram of the AC uninterruptible power supply of the present invention. The difference between the power supply device of the present invention and the conventional device is that the power supply device has a high frequency transformer for output isolation.
- As a DC converter, in conventional devices, a DC-DC converter 4 in which power is transferred only in one direction from the battery 3 to the PWM inverter 5, as shown in FIG.
However, the device developed by Zero and Mei uses a DC-DC converter 7 that can transmit power bidirectionally, and effectively regenerates power from the load to the battery 3.

Figure 4 shows a DC-D device that can transmit power in both directions according to the present invention.
This circuit, which shows one specific example of the C converter 7, is, for example, "New DC-DC converter with energy storage reactor (NEW DC-DCC0NVERτER9W
ITHAN ENERGY 5TORAGE R
RACTEOR) J IEEEτransacti
on ON MAGNEHC3, Sep, 1977
Vol, MAG-13No, 5 pp, 1211~
It is the same as 1213 in circuit configuration and operating principle.

In the DC-DC converter 7 shown in FIG. 4, a regeneration diode 13 and a regeneration switch 14 are connected in parallel with the main switch 11 and main diode 12 of the DC-DC converter, respectively. The regeneration switch 14 is driven to be on when the switch 11 is off and off when the switch 11 is on.

(Function) Here, when power is applied from the output side, when the switch 14 is on, energy is multiplied in the transformer 8, and when the switch 14 is turned off, the energy of the transformer 8 is regenerated to the input side through the diode 13. be done. The relationship between the human power and the voltage at both output terminals is the same as the above equation. In addition, since the battery 3 is connected to the input side of the converter 7, the input voltage of the converter 7 is kept approximately constant;
If n/Toff is adjusted appropriately, the desired voltage E is always achieved.

is obtained. In Figure 4, power can be transmitted in both directions.C
- Although the pack-boost type, which is commonly used as a DC converter, is shown as an example, the same effect can be obtained by adding regeneration diodes, switches, etc. to push-pull type, forward type, etc. As an actual switch element, a semiconductor switch element such as a bipolar transistor, FET, GTO, or thyristor is used.

As described above, according to the present invention, the power returned from the load side is effectively regenerated to the battery side by the DC-〇〇 converter that can transmit power in both directions, so that the PWM by the power returned from the load side is effectively regenerated. The voltage increase at the input terminal of the inverter 5 is suppressed, and the input voltage of the PWM inverter 5 is always adjusted to an optimal state. Therefore, the PWM inverter 5 can always be operated under optimal conditions, and the output waveform can be improved. Furthermore, since there is no need for special elements such as large capacitors to suppress voltage rise, the power supply can be made smaller.

(Example) FIG. 5 shows an example of the present invention. In this figure, the part surrounded by dotted line 2 represents the rectifier. Commercial electricity f!
The AC voltage applied from J1 is transmitted to rectifying bridge 22 through noise filter 21, and the voltage rectified by 22 is smoothed by capacitor 23. The DC voltage obtained across the capacitor 23 is adjusted in voltage and current by the DC-DC converter 24 and is transmitted toward the battery and the load. DC-DC converter 24
The output is controlled to an optimum voltage and current state by a PWM control circuit 25 provided with voltage feedback al and current feedback b1. The voltage from the rectifier and battery is p w M jl with voltage feedback a2 and current feedback b2
The DC-DC converter 7 (the part surrounded by the dotted line 7) driven by the yj 91 circuit 75 is insulated from the load, and the voltage and current are adjusted to the optimal state, and the PWM inverter 5 (the part surrounded by the dotted line 5) ). D.C.
- The DC voltage from the DC converter is converted into a sinusoidally PWM-modulated voltage by the bridge inverter 51, and after removing high frequency components caused by switching by smoothing LC filters 52 and 53, it is passed through the noise filter 54 to the load 6. communicated. The bridge inverter 51 is synchronized with 1Eil and modulated into a sine wave.
! It is driven by a PWM control circuit 55 provided with voltage feedback a5 and current feedback b5 for generating W M 111.

FIG. 6 shows another embodiment of the DC-DC converter 7.

This circuit has a regeneration diode 13, a regeneration switch 14, and a switch 17 connected to a conventional converter circuit called a forward type. Switch 11 and switch 17 are driven at the same timing, and switch 14 is driven for a period opposite to the timing of switch 11, that is, when switch 11 is on, it is off, and when switch 11 is off, it is on. This converter is driven by a p W M ml m circuit 15 with voltage feedback a and current feedback. First, when power is transmitted from the primary to the secondary, that is, from the left side to the right side of the circuit, when the switch 11 is on, the voltage on the negative side is transmitted to the secondary side through the transformer 8, and the power is It is supplied to the load and L through the diode 16. When the switch 11 is turned off, the energy stored in L is supplied to the load through the diode 16. Conversely, when power is transferred from the secondary to the primary, i.e. from the right side to the left side of the circuit, when switch 14 is on, energy on the secondary side is stored in L, and when switch 14 is off, energy on the secondary side is stored in L. The energy stored in the secondary side and the power on the secondary side are transferred to the primary side through the switch 17 and the transformer 8. -The relationship between the voltage on the primary side and the voltage on the secondary side is
, is determined by the off-time ratio, and is adjusted to an appropriate value by the control circuit 15.

As shown in the embodiments shown in Figs. 7, 8, and 9, regeneration switches and diodes are also used in DC-DC converter circuits such as two-stone forward type, push-pull type, and half-bridge type. By adding , power can be transmitted in both directions and the C-DC converter circuit can be used.

(Effects of the Invention) According to the present invention, since the input voltage of the PWM inverter 5 is always adjusted to the optimum condition, the PWM inverter 5 can always be operated under the optimum condition, and the output waveform of the power supply device is improved. Leads to. Furthermore, since there is no need for special elements such as large capacitors to suppress voltage increases, the power supply can be made smaller and lower in price.

[Brief explanation of the drawing]

FIG. 1 is an example of a block diagram of a conventional AC uninterruptible power supply, FIG. 2 is a specific example of the DC-DC converter 4 shown in the first section, and FIG. 3 is an example of the AC uninterruptible power supply of the present invention. An example of a block diagram, ``Figure 4 is the DC-DC shown in Figure 3.
One specific example of the converter 7, FIG. 5 is an embodiment of the present invention,
6, 7, 8 and 9 respectively show embodiments of the DC-DC converter 7 shown in FIG. In the figure, 1 is a commercial AC power supply, 2 is a rectifier, 3 is a battery, 4 and 7 are DC-DC converters, 5 is a PWM inverter, 6 is a load, 8 is a high frequency transformer, 9 and 23 are capacitors, 11, 11 17, 18 and 18' are switches, 12, 13, 16 and 16' are diodes, 21 and 54 are noise filters, 22 are bridge diodes, 24 are DC-D'C converters, 51 are PWM inverters, 52 and 53 are LC filters, and 15, 25.55 and 75 are control circuits, respectively.

Claims (1)

[Claims] 1. A DC-D that includes a rectifier that rectifies commercial AC power and supplies DC voltage to the battery and load, a battery that supplies power during a commercial power outage, and a high-frequency transformer for output isolation.
In an AC uninterruptible power supply that is equipped with a C converter and a PWM inverter that generates AC at a commercial frequency from DC, and constantly supplies AC power at a constant commercial frequency to a load,
The above DC-DC converter with a high-frequency transformer for output isolation is capable of bidirectionally transmitting power.
By using a converter, reactive power generated on the load side due to load conditions is regenerated to the battery side, thereby making it possible to reduce the output capacitor capacity of the DC-DC converter and improve the PWM inverter output waveform. AC uninterruptible power supply.