JPS5825738Y2 - Uninterruptible power system - Google Patents

Description

[Detailed description of the invention] This invention proposes that an uninterruptible power supply system consisting of a rectifier that also serves as a charging device, a storage battery, and an inverter has an excessive AC input capacity, including when power is being supplied from the bypass power supply to the load. The aim is to prevent this from happening.

In this type of uninterruptible power supply, normally a rectifier converts alternating current power into direct current to charge a storage battery, and at the same time supplies direct current power to an inverter, which converts the direct current power into alternating current.

A switch is used to switch between the inverter output and the bypass power supply, and normally the inverter output power is supplied to the load.

Furthermore, in the event of an inverter failure or inverter inspection, the switching device is switched to the bypass side to directly supply commercial power to the load.

However, in conventional devices of this kind, even during bypass power supply, the rectifier always has the ability to supply the rated output power to the storage battery, so there is a possibility that the storage battery will be charged with the rectifier's rated output current.

Particularly when the storage battery voltage is low or when the rectifier is performing equal charging, the storage battery will be reliably charged at the rectifier's rated output current.

Therefore, during bypass power supply, the sum of the apparent power supplied to the load through the bypass circuit and the apparent power required to charge the storage battery is larger than during normal operation, and the limit value of allowable input apparent power may be exceeded or the input Overcurrent interruption of the circuit breaker sometimes occurred.

The present invention provides a new device that eliminates these drawbacks, and includes a rectifier that also serves as a charging device, a parallel circuit between a storage battery connected to the rectifier output and an inverter input, and an output circuit of the inverter or a rectifier input power source. In a device configured to supply power to a load from a bypass circuit that also serves as a bypass circuit, a current detection device is provided in a common circuit between a rectifier input and a bypass circuit input, and the output of the rectifier is controlled in response to the output of the current detection device. It is characterized by this.

The present invention will be explained below with reference to the block diagram shown in FIG.

In the figure, 1 is an input power supply terminal, 2 is a breaker for input wiring, 3 is a current detection device, 4 is a rectifier that also serves as a charger, and 5
6 is a storage battery, 6 is an inverter, 7 is a switch for switching between the inverter output and a commercial power supply bypass circuit, and 8 is a load.

Further, 9 is a bypass circuit for directly supplying commercial power to the load.

In this system, commercial power is normally received from an input power supply terminal 1 and connected to a rectifier 4 via a wiring breaker 2 and a current detection device 3, and the rectifier 4 charges a storage battery 5 and supplies power to the invercro.

The invercro converts the DC power supplied from the rectifier 4 into AC power, and supplies the output to the load 8 via the switch 7.

In this case, the output of the current detection device 3 provided in the common circuit of the rectifier 4 and the bypass circuit 9 is detected, and this is compared with a reference value to amplify the error and phase control the rectifier. The output current of the rectifier 4 is controlled to be below the maximum allowable current.

When the inverter 6 breaks down or is inspected, the switch 7 is switched to the bypass circuit 9 side and commercial power is directly supplied to the load 8.

In this case as well, the current detection device 3 detects (rectifier input current + bypass circuit current) and controls the output current of the rectifier 4 so that the total input current is equal to or less than a preset maximum allowable current.

If the output of the inverter 6 is now delayed by 50 KVA with a power factor of 80%, and the efficiency of the inverter at this time is 80%, the inverter input power will be 50 KW.

Further, if the output voltage of the rectifier 4 is 220V and the storage battery charging current is 50A, the total output power required for the rectifier is 50KW+220V×50A=61KW.

If the efficiency of the rectifier at this time is 85% and the power factor is 80%, then the apparent power input to the rectifier is as follows.

If the power supply at this time is a single-phase 200 mm, the input current required for the rectifier will be 450 A.

In this example, 450 A is the maximum input current, and power supply equipment with a capacity matching this is installed.

Furthermore, during bypass power supply, the total input apparent power of this equipment is 90KVA, so if 50KVA is supplied to the load, the rectifier input apparent power must be limited to 40KVA.

(Assume that the resultant power factor does not change.

) In this embodiment, the sum of the rectifier input current and the bypass circuit current is detected and given to the rectifier as a signal for current limiting, so the rectifier output current is automatically limited to the rectifier's manual power of 40 KVA or less. Ru.

In this case, the rectifier 4 only needs to charge the storage battery 5, and a maximum input current of 40 KVA is sufficient.

Further, in this case, it is also possible to change the settings of the current limiting device to make the current limiting value smaller than during normal operation.

Next, one embodiment of the rectifier 4 including the current detection device 3 is shown in FIG.

In this embodiment, 111 is a rectifier transformer, 112 is a rectifier circuit using a diode and a silice, and 113 is a rectifier transformer.
is a DC smoothing choke coil.

Further, 114 is a phase shift pulse generation circuit, 115 is an amplification circuit,
116 is a reference voltage diode, 117 is a diode for detecting a voltage proportional to the output voltage, 118 is a diode for detecting a voltage proportional to the sum of the rectifier input current and bypass circuit current, and 119 and 120 are outputs. This is an attenuator for voltage detection.

Further, 121 is a rectifier circuit for converting the output of the current transformer used as the current detection device 3 into direct current, and 122 is a resistor for obtaining a voltage proportional to the sum of the rectifier input current and bypass circuit current. .

In this embodiment, when the current of the current detection device 3 is within a predetermined setting value, the diode 117 is energized, and the amplifying circuit 115 and the phase shifter are connected so that the voltage of the resistor 119 and the voltage of the reference voltage diode 116 are equal The pulse generating circuit 114 performs normal automatic control to keep the output voltage constant.

When the output voltage of the current detection device 3 increases and attempts to exceed a predetermined maximum current value, the voltage of the resistor 122 increases, the diode 118 becomes energized, and the voltage tends to exceed the voltage of the reference voltage diode 116.

As a result, the phase-shifted pulse generation circuit 114 performs automatic control to delay the pulse generation phase and keep the voltage across the resistor 122 constant.

As a result, it has become possible to operate the system without the total input apparent power exceeding the maximum input apparent power during normal operation in any case.

By implementing the present invention, there will be no abnormal increase in input apparent power (in the above embodiment, if the system is like the conventional example, the total input apparent power during bypass power supply is 50KVA).
There is a possibility that +90KVA=140KVA.

) It is possible to prevent the system from going down due to this, and its practical effects are enormous.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a connection diagram showing an embodiment of the present invention. 3... Current detection device, 4... Rectifier,
5...Storage battery, 6...Inverter, 7
......Switcher, 8...Load, 9...
...Bypass circuit.

Claims (1)

[Scope of utility model registration request] In a device configured to supply power to a load from a rectifier that also serves as a charging device, a parallel circuit of a storage battery connected to the rectifier output and an inverter input, an output circuit of the inverter, or a bypass circuit that also serves as a rectifier input power source,
An uninterruptible power supply system characterized in that a current detection device is provided in a common circuit between a rectifier input and a bypass circuit, and the output of the rectifier is controlled in response to the output of the current detection device.