JP7100519B2 - Uninterruptible power system - Google Patents

Description

The present invention relates to a circuit method for making the current flowing through each uninterruptible power supply device the same when connecting a plurality of uninterruptible power supply devices in parallel in order to increase the rated current of the uninterruptible power supply device.

As a method of increasing the rated current of a conventional uninterruptible power supply (hereinafter referred to as "UPS"), there is a method of connecting a plurality of UPSs in parallel in addition to the method of connecting switching elements in parallel. Hereinafter, each of a plurality of UPSs connected in parallel to form one UPS will be referred to as a UPS module.
Among the methods for connecting a plurality of UPS modules in parallel, there are the following methods (1) and (2).

(1) No parallel control Select the on-resistance, on-voltage, and switching time of the switching element mounted on each UPS module, align the characteristics, and align the delay time of the on / off signal transmitted to the switching element. A method in which passive elements such as an AC filter reactor with the same characteristics are added to make the current flowing through each UPS the same.

(2) With parallel control A method of detecting the current of each UPS module and controlling and adjusting the on / off width of the switching element so that the current of each UPS module becomes the same.

Patent Document 1 is a prior art of the above-mentioned parallel connection method with parallel control. In Patent Document 1, when the variation of the output voltage of a plurality of inverters is suppressed by making the input voltages of the plurality of inverters uniform, in order to control the DC voltage supplied from the converter to the inverters for each UPS, In response to the problem that a voltage detector that detects DC voltage is required, which leads to an increase in the size of a non-disruptive power supply system, each UPS module supplies a converter, an inverter, a control circuit, and a DC voltage from the converter to the inverter. It has a configuration including one DC bus for the voltage detector and one voltage detector connected to the DC bus.

Japanese Unexamined Patent Publication No. 2018-7377

Patent Document 1 is a parallel connection method with parallel control, and it is not necessary to have a voltage detector in each UPS module. However, since the control circuit is provided in each UPS module, the circuit is complicated. It cannot be said that it is sufficient to solve the problems of large size and high cost, and the parallel connection method without parallel control is advantageous for these problems.

Therefore, when considering the parallel connection method without parallel control, as explained in (1) No parallel control described above, in order to make the current flowing through each UPS module the same, the characteristics of the switching element and the ON / ON / It is necessary to strictly match the characteristics of the off-signal and passive elements.

In recent years, the performance of switching elements has been improved to increase the speed and reduce the on-resistance. Regarding the on / off of switching elements, it is necessary to match the characteristics on the order of several tens of ns and adjust the wiring length of the circuit. It is necessary to make the circuit design strict or to allow a large value as the difference in the current flowing through each UPS module connected in parallel (hereinafter referred to as "cross current"), which leads to an increase in cost. ..

The present invention has been made in view of such a problem, and is to provide a UPS capable of reducing the cross flow flowing through each UPS module connected in parallel with a simple circuit configuration in a method of parallel connection method without parallel control. With the goal.

In view of the above background technology and problems, the present invention includes, for example, a forward converter that converts an AC voltage into a DC voltage, an inverse converter that converts the DC voltage into an AC voltage, and a storage battery. It is a non-disruptive power supply device in which a plurality of device modules are connected in parallel, and the non-disruptive power supply device module is configured to be connected in parallel via a resistor on the positive side, the negative side, or both of the DC voltage portion.

According to the present invention, it is possible to provide an uninterruptible power supply device capable of reducing the cross flow flowing through each UPS module connected in parallel with a simple circuit configuration.

It is a circuit block diagram of UPS in Example 1. FIG. It is an internal circuit block diagram of the forward converter and the reverse converter of FIG. It is a circuit block diagram of UPS in Example 2. FIG. It is a circuit block diagram of UPS in Example 3. FIG. It is an internal block diagram of the DC converter of FIG. It is a circuit block diagram of the UPS of the constant commercial power supply system in Example 4.

Hereinafter, examples of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit block diagram of UPS in this embodiment. In FIG. 1, in order to increase the rated current of the UPS 81, a plurality of UPS modules 71 to 73 are connected in parallel and controlled by a signal of the control device 6. The inside of each UPS module is composed of a forward converter 3, a reverse converter 4, and a storage battery 5. The forward converter 3 and the reverse converter 4 are connected in parallel by the AC terminal 17 and the DC terminal 18. When connecting the DC terminal 18 of each UPS module, a positive electrode side resistor 1 and a negative electrode side resistor 2 are added and connected to the DC bus line 7. The same signal is transmitted as the signal of the control device 6 sent to each UPS module, and there is no control for reducing the difference in the current flowing between each UPS.

FIG. 2 is an internal configuration diagram of the forward converter 3 and the reverse converter 4. As shown in FIG. 2, the forward converter 3 and the reverse converter 4 are generally composed of a switching element 11, a switching element drive circuit 13, an AC filter reactor 12, an AC filter capacitor 14, and a DC smoothing capacitor 15. It is a configuration of a three-phase three-wire power converter. By adjusting the on / off time of the switching element 11, the mutual conversion between the AC voltage / AC current and the DC voltage / DC current is performed.

Since the current flowing between the UPS modules is uncontrolled, the current flowing through each UPS is almost the same because the circuit configuration and the characteristics of the elements are the same. However, the current flowing through each UPS varies due to the on / off delay time of the switching element, the characteristics of the passive element, the difference in the wiring length of the circuit, etc., and it is necessary to allow a margin for the current value of the switching element. There is.

On the other hand, at the development stage, the circuit simulator is used to simulate the on / off delay time error of the switching element, the characteristic error of the passive element, and the impedance difference due to the wiring length of the circuit to maximize the current. It is possible to find the variation.

That is, in this simulation, it is confirmed that the current variation (cross current) is reduced by changing the resistance values of the positive side resistor 1 and the negative side resistor 2 when connecting the DC terminals of each UPS module. , The loss of the resistor will increase, and the cost will increase. Since there is a trade-off relationship between the variation in the current flowing through the switching element and the loss of the resistor, the optimum value of the resistance value is obtained by changing the resistance value. For example, in the case of UPS with a capacity of 100 KVA, the value of the resistor is about 20 mΩ.

In this way, the positive and negative sides of the DC voltage portion of the forward converter and reverse converter of each UPS module are connected in parallel via a resistor, and the resistance value is appropriately selected so that the cross current is the same condition. In the case of, it is possible to increase the allowable range of error between the characteristics of the switching element, the on / off signal, and the characteristics of the passive element when there is a resistor compared to when there is no resistor. It will be possible to simplify sorting and circuit design. The AC component of the current is limited by the impedance of the reactor, but the DC component of the current cannot be limited because the impedance of the reactor is low. Therefore, the cross flow can be suppressed by adding the resistor of this embodiment.

Further, since the loss of the resistor is about 1/1000 of the UPS capacity, it is possible to reduce the parts cost of the UPS, shorten the development period, and improve the robustness against the secular change of the parts characteristics.

If the resistance value is made extremely large or the DC terminal parts are not connected in parallel, the voltage of the DC terminal part of the forward converter 3 and the reverse converter 4 will be different, which will lead to the lateral flow of the current flowing through the AC terminal. .. On the contrary, when the resistance value is made extremely small or the DC terminal portion is connected by an electric wire or the like, a direct current cross current flows, and as a result, the alternating current also increases.

Further, in FIG. 1, the positive electrode side resistor 1 and the negative electrode side resistor 2 are clearly shown as resistors, but any component other than the resistor can be applied as long as it fulfills the function of the resistor. For example, it is possible to substitute a long and thin electric wire, a member having a long and thin printed circuit board pattern, a contact resistance of a small-capacity connector or a relay contact, and the like. For example, in the case of a long and thin electric wire, the electric wire having a cross section of 1 square mm is about 20 mΩ / m. This can be achieved by connecting instead of 2.

The resistor may be inserted on either the positive electrode side or the negative electrode side. Further, in FIG. 1, although it is composed of three UPS modules, this embodiment is effective if there are two or more UPS modules. Further, although the three-phase three-wire power converter is described in FIGS. 1 and 2, the same effect can be obtained with a single-phase power converter and a three-phase four-wire power converter.

As described above, according to the present embodiment, the DC voltage portions of the forward converter and the reverse converter are connected in parallel to the positive electrode side and the negative electrode side via a resistor, so that they flow to each UPS module connected in parallel. Since the cross current can be reduced and it can be realized with a simple circuit configuration, it is possible to provide a UPS capable of cost reduction.

In the first embodiment, the positive electrode side resistor 1 and the negative electrode side resistor 2 connected to the DC side are connected by the DC bus 7, but in this embodiment, a configuration in which the DC bus is not used will be described.

FIG. 3 is a circuit block diagram of UPS in this embodiment. In FIG. 3, the same functions as those in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted. As shown in FIG. 3, the plurality of UPS modules 71 to 73 are connected to each other by the positive electrode side resistor 1 on the positive electrode side and the negative electrode side by the negative electrode side resistor 2 without using a DC bus. This eliminates the need for a DC bus, and when three UPSs are connected in parallel, the number of resistors can be reduced from six to four.

In Examples 1 and 2, each UPS has a storage battery between the forward converter and the reverse converter, but in this embodiment, a configuration in which the storage battery is shared will be described.

FIG. 4 is a circuit block diagram of the UPS in this embodiment. In FIG. 4, the same functions as those in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted. As shown in FIG. 4, the UPS in this embodiment shares the storage battery 5 and adds a DC converter 8 to each UPS module. The DC converter 8 can supply the DC voltage of the storage battery 5 to the DC terminals 18 of the forward converter 3 and the reverse converter 4, and can supply the AC voltage to the load device 32 without power failure. Further, the DC converter 8 can also supply electric power for charging the storage battery 5 with the DC voltage of the DC terminal 18 of the forward converter 3 and the reverse converter 4.

FIG. 5 is an internal configuration diagram of the DC converter 8. As shown in FIG. 5, the DC converter 8 includes a switching element 11, a drive circuit 13 thereof, a DC filter reactor 16, and a DC smoothing capacitor 15. By adjusting the on / off time of the switching element 11, the direct current voltage and the direct current current are converted.

In this embodiment as well, since the cross current flows through the forward converter 3, the inverse converter 4, and the DC converter 8 between the UPSs as in the first and second embodiments, the positive electrode side resistor 1 and the negative electrode side resistor 2 are appropriate. By selecting to, the cross current can be reduced.

In this embodiment, since the DC voltage can be boosted by the DC converter 8, there is an advantage that the range in which the storage battery 5 can be selected is widened.

Although the first to third embodiments are the UPS of the constant inverter system, the UPS of the constant commercial power supply system will be described in this embodiment.

FIG. 6 is a circuit block diagram of a UPS of a constant commercial power supply system in this embodiment. In FIG. 6, the same functions as those in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted. As shown in FIG. 6, in the configuration of the continuous commercial power supply system UPS, the UPS module is only the inverse converter 4, and the electromagnetic switch 19 and the electromagnetic switch 20 are added.

In FIG. 6, normally, the electromagnetic switch 20 is closed and the electric power from the commercial power supply 31 is supplied to the load device 32, and the inverse converter 4 is in the standby state. When the commercial power supply 31 loses power, the electromagnetic switch 20 is opened, the electromagnetic switch 19 is closed, and power is supplied from the storage battery 5 to the load device 32 through the inverse converter 4. The electromagnetic switch 19 may be closed at all times.

When the commercial power supply 31 is normal, the cross flow is small, but when there is a power failure, the cross flow flows between the UPS modules as in Examples 1 to 3, so that the positive electrode side resistor 1 and the negative electrode side resistor 2 are effective for the cross flow. ..

In this embodiment, the electromagnetic switch 19 and 20 are momentarily interrupted, but the UPS module does not require the forward converter 3 and only the reverse converter 4, so that the circuit is simple and inexpensive. There are advantages.

The present invention is not limited to the above examples, and includes various modifications. For example, the above-described embodiment has been described in detail in order to explain the present invention in an easy-to-understand manner, and is not necessarily limited to the one including all the described configurations. Further, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. Further, it is possible to add / delete / replace a part of the configuration of each embodiment with another configuration.

1: Positive current side capacitor 2: Negative current side resistor 3: Forward converter 4: Reverse converter 5: Storage battery, 6: Control device, 7: DC bus, 8: DC converter, 11: Switching element , 12: AC filter reactor, 13: Switching element drive circuit, 14: AC filter capacitor, 15: DC smoothing capacitor, 16: DC filter reactor, 17: AC terminal, 18: DC terminal, 19, 20: Electromagnetic switch, 31: Commercial power supply, 32: Load device, 71, 72, 73: UPS module, 81: Non-disruptive power supply device (UPS)

Claims (4)

An uninterruptible power supply that connects a plurality of uninterruptible power supply modules having a forward converter that converts an AC voltage to a DC voltage, an inverse converter that converts the DC voltage into an AC voltage, and a storage battery in parallel.
An uninterruptible power supply device characterized in that the uninterruptible power supply module is configured to be connected in parallel on the positive electrode side, the negative electrode side, or both of the DC voltage portion via the contact resistance of a contact of a connector or a relay . An uninterruptible power supply that connects a plurality of uninterruptible power supply modules having a forward converter that converts an AC voltage to a DC voltage and an inverse converter that converts the DC voltage into an AC voltage in parallel.
The uninterruptible power supply module comprises a DC converter connected to the DC voltage portion.
It has a storage battery commonly connected to the DC converter of the plurality of uninterruptible power supply modules, and supplies the voltage of the storage battery to the DC voltage portion via the DC converter.
An uninterruptible power supply device characterized in that the uninterruptible power supply module is configured to be connected in parallel on the positive electrode side, the negative electrode side, or both of the DC voltage portion via the contact resistance of a contact of a connector or a relay . An uninterruptible power supply that connects a plurality of uninterruptible power supply modules having a storage battery and an inverse converter that converts the DC voltage of the storage battery into an AC voltage in parallel.
An uninterruptible power supply device characterized in that the uninterruptible power supply module is configured to be connected in parallel on the positive electrode side, the negative electrode side, or both of the DC voltage portion via the contact resistance of a contact of a connector or a relay . In the uninterruptible power supply according to claim 3,
One end of the first switch is connected to the output of the plurality of uninterruptible power supply modules connected in parallel.
The other end of the second switch connected to the commercial power supply is connected to the other end of the first switch.
The electric power from the commercial power source is supplied to the load device with the second switch closed, and the electric power from the storage battery opens the second switch and closes the first switch, and the inverse converter. A non-disruptive power supply characterized by being supplied to a load device via.

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