JPH01295631A - Controller for uninterruptible power source equipment - Google Patents

Abstract

PURPOSE:To minimize unbalance by detecting recharge current of a battery through each rectifier and providing a constant current control circuit for limiting the recharge current below a predetermined level then operating the constant current control circuit such that output currents from respective rectifiers in uninterruptible power source equipments connected in parallel are balanced. CONSTITUTION:DC current transformers 9S1, 9S2, S3 are arranged in a loop 13 for recharging a battery 3 in order to detect current flowing through a DC bus, and the output from a rectifier is controlled to 10% of the set value of battery recharge current. By such arrangement, load can be born by rectifiers S1, S2, S3 with unbalance of output current in the range of + or -10%. When the battery 3 is recharged, a 200% load is born by the rectifiers S1, S2, S3 such that the rectifier having highest output voltage bears 76.7% of output current, the rectifier having intermediate output voltage bears 66.7% of output current and the rectifier having lowest output voltage bears 56.7% of output current.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention comprises a plurality of uninterruptible power supplies in which the output of a rectifier is directly connected to a common storage battery, and each of the uninterruptible power supplies The present invention relates to a control device for an uninterruptible power supply that balances the output currents of each rectifier.

(Conventional technology) For stationary uninterruptible power supplies made of semiconductor rectifying elements, multiple uninterruptible power supplies are often installed to create parallel redundancy in order to improve reliability as a power source. .

FIG. 2 is a block diagram showing a conventional parallel system of a plurality of uninterruptible power supplies and its control device. In this Figure 2, three uninterruptible power supplies fVh, M2
and M3- have rectifiers St, S2 and S3 connected to the same commercial power supply 1, and inverters 1112 and I3 connected to each of the rectifiers, respectively, and each of the inverters 11. 12 and I3 are connected to the common load 2 via semiconductor switches 5t-L+5l-12 and SH3 as shown. In addition, each rectifier S1. S
A storage battery 3 is connected to the DC side of S2 and S3 for floating charging.

Each rectifier S1. S2B and S3 are controlled by rectifier control circuits 10S1.1032 and 1033, respectively, and since each control circuit 10S1.1032 and 103 have the same configuration, the rectifier control circuit 10S1 will be described as a representative.

That is, the control circuit 10S1 includes a constant voltage control circuit 5S1. A phase that determines the firing phase of the rectifier S1 according to the outputs of the constant current control circuit 6S1 and the constant voltage control circuit 5S1, which limit the output level of the constant voltage control circuit 5S1 in order to suppress the output current of the rectifier S1 to a predetermined limit current or less. It is equipped with a container 7S1. And this control circuit 10
The constant current control circuit 6S1 of S1 is a DC bus I! It is configured to operate by the output current of the rectifier S1 obtained by the current transformer 12S1 provided at the rectifier S1.

Each of the inverters h, I2, and I3 is controlled by a control circuit (not shown) so that the output voltage and phase of each inverter coincide with each other, and the balance of the output current is maintained. Further, each inverter h, 12 and I3 is connected to a semiconductor switch 5t-h, SH2 and SH3, respectively.
The connection to and disconnection from the AC output bus 8 is performed by the following steps.

On the other hand, each rectifier St directly connected to the storage battery 3 via the DC bus 4
, 32 and S3 are each of the rectifier control circuits 10S
Constant voltage control is performed by the operations of 1, 1032 and 10S3. However, for example, the constant voltage control circuit 5S1 of unit 1
Even if the voltage setting of the constant voltage control circuit 5S2.5S3 of the other model is a small difference, the feedback signal for constant voltage control is obtained from the DC bus 4 of each model, so the voltage setting of the constant voltage control circuit 5S2. The constant voltage control circuits 582 and 533 of the device control the rectifiers 10S2 and 1033 of other devices by the action of closed loop control.
may operate to throttle the output voltage.

If the constant voltage control circuit falls into such an operation, only the rectifier S1 will share the direct current supplied to the inverter h2, I2.13 and the storage battery 3.

This phenomenon of current sharing is caused by the constant current control circuit 6S1,
The problem can be solved to some extent by only the operations of 6S2 and 6S3. But in any case, the rectifier S1. The degree of sharing of the output current between S2 and S3 is poor, and this tendency becomes stronger as the load becomes lighter, and when the equipment is operated for a long period of time, it may cause an imbalance in each equipment in terms of reliability and life. I don't like it.

What is shown in FIG. 3 is an electric current deviation detection circuit 11S1 that detects the deviation of the output current of each rectifier S1, in order to eliminate the problems of the conventional control device shown in FIG.
According to the output of the constant voltage control circuit 5S1, the output level of the constant voltage control circuit 5S1 is limited in order to reduce the output current deviation.

(Problem to be Solved by the Invention) However, in the control device shown in FIG. 3, it is necessary to send and receive signals between the uninterruptible power supplies Mt, M2, and M3 connected in parallel. Adjusting the balance between devices is also not easy. In addition, the output current ll difference detection circuit 11
Since the loop including S1 forms a kind of closed loop, unless the closed loop of constant voltage control and the response are emphasized well, the operation tends to become unstable and the response adjustment is not easy.

Furthermore, another problem with the conventional control device shown in FIGS. 2 and 3 is the problem of limiting the charging current to the storage battery 2. For example, three uninterruptible power supplies S1. S2,
A parallel circuit of S3, and each device St, S2, S3
If the limiting current value of the constant current control circuit 6S1゜682.6S3 of 120% x 3 when charging when power is restored)
An overcharge current equivalent to -100%-260% flows, which has an adverse effect on the life of the storage battery 3 (usually, it is preferable that the charging current is 1/10 to 115 of the discharging current). This overcharge current becomes larger as the load becomes lighter.

An object of the present invention is to minimize the unbalance of the output current of each rectifier regardless of the size of the load in a plurality of uninterruptible power supplies in which the output of the rectifier is directly connected to a common storage battery, and to reduce the charging current of the storage battery. The object of the present invention is to provide a control device for an uninterruptible power supply with a simple configuration that can limit

[Structure of the Invention] (Means for Solving the Problems) A control device for an uninterruptible power supply according to the present invention includes a rectifier having a constant voltage control function and a constant current control function, and an inverter that converts the DC output of the rectifier into AC. In a plurality of uninterruptible power supply apparatuses, in which the DC output of the rectifier is directly connected to a common storage battery, a charging current for charging the storage battery of each rectifier is detected, and this charging current is adjusted to a predetermined level. This is characterized by the provision of a constant current control circuit that limits the following.

(Function) In the present invention, by controlling the constant current of each rectifier so that the current in the loop that charges the storage battery of each rectifier of a plurality of uninterruptible power supply devices is equal to or less than the rated charging current of the storage battery, no load can be applied. Also, the unbalanced portion of the output current of each rectifier is suppressed to below the rated charging current of the storage battery, and the charging current to the storage battery is also limited.

(Example) The present invention will be described below with reference to an example shown in FIG. In FIG. 1, the same reference numerals as those in FIGS. 2 and 3 indicate the same parts, so the explanation thereof will be omitted. That is, a plurality of uninterruptible power supplies M1. M2 and M3 are respectively rectifiers S1. S2.

S3 and inverter 11. I2.13, and semiconductor switches SH1 and SH1 are connected between the commercial power supply 1 and the load 2.
connected in parallel via SH2 and SH3, and storage battery 3
are connected to be floatingly charged, and each rectifier S
1,32.33 rectifier control circuit 10S11052,
1033 is the constant voltage control circuit 5S1, 5S2.533
, constant current control circuits 6S1, 6S26S3 and phase shifter 7
S1,732.

The configuration including 7S3 is the same as the conventional one shown in FIG.

Therefore, in the present invention, the rectifier control circuit 10S1
In the conventional constant current control circuit 6St, the rectifier S1
However, in the present invention, each rectifier S1. S2.

This circuit is characterized in that the current in the loop 13 that charges the storage battery 3 of S3 is detected by DC transformers 931, 932, and 933, and the circuit is configured so that a constant current control operation is performed based on the detection signal. This constant current control circuit 631,
The operation level of 632 and 633 is set by the reference charging current of the storage battery 3.

The constant current control circuit of each rectifier S1, 32 so as not to exceed this operating level.

The output of 83 will be controlled.

Next, the operation of the control device for the uninterruptible power supply of the present invention configured as described above will be explained. As shown in Figure 1, 3
uninterruptible power supply M1. M2.

M3 are connected in parallel, and the storage battery 3 is connected to the rectifier S1.
Commonly connected to S2 and S3. load 2 is 200
%, DC current transformer 9S1,932.

Constant current control circuits 6S1 and 6S2 set the value of 9S3.

It is assumed that the rated load of each rectifier of 6S3 is set to 10%.

When the storage battery 3 is in a fully charged state, each rectifier S1, 32
, S3's load sharing state is ideally divided into three equal parts of 66
87%, but each uninterruptible power supply f through storage battery 3
Since the DC buses 4 of Vh, M2, and M3 are commonly connected, the rectifier output of the signal device can share the load, or the rectifier load can be shared by the rectifier output of the signal device.

However, in the present invention, as shown in FIG. 1, the loop 13 for charging the storage battery 3 includes DC transformers 9S1, 9S2.
By installing 9S3 to detect the current flowing to the DC bus and controlling the rectifier output with the set value of the storage battery charging current,
The load sharing of each rectifier S1゜S2, S3 is at most +1
The unbalance of the output current can be suppressed to within 0%, and at least within -10%.

That is, rectifier S1. Among S2 and S3, the rectifier with the highest output voltage has an output current of 76.7%, the next highest rectifier has an output of 66.7%, and the rectifier with the lowest output has an output of 56.7%.
% of the output will be shared. In addition, in this state, the recharging current after discharging the storage battery 3 is controlled by the rectifier S1. S2.3
Charging current is supplied to the storage battery 3 from the rectifier with the highest output voltage among the rectifiers S1. S2
, the unbalanced state of the output current of S3 can be limited to the same as before charging the storage battery 3. That is, the charging current to the storage battery 3 is limited to the rated charging current under any load condition.

[Effects of the Invention] As described above, in the present invention, by providing a constant current control circuit that detects the current in the loop that charges the storage battery of each rectifier and limits this charging current to a predetermined level or less, the parallel It functions to balance the output currents of each rectifier of each connected uninterruptible power supply, thereby minimizing unbalance.

[Brief explanation of the drawing]

FIG. 1 is a block connection diagram showing one embodiment of a control device for an uninterruptible power supply according to the present invention, and FIGS. 2 and 3 are block connection diagrams showing different conventional uninterruptible power supply devices. Ml, M2, M3... Uninterruptible power supply S1, 32
, S3... Rectifier 11, I2, 13... Inverter SH1, SH2, 81-13... Semiconductor switch
-Commercial power supply 2...Load 3...Storage battery 4...DC bus 5S1.5S2.533...Constant voltage control circuit 681.
652.633... Constant current control circuit 7S1, 7S2.
7S3... Phase shifter 8... AC buses 1051, 1032, 1033... Rectifier control circuit 9S1, 952.9S3... DC transformer 11S1.
...Current deviation detection circuits 1231, 1232, 1233...Current transformer 13.
...Charge Loop (8733) Agent Patent Attorney Yoshiaki Inomata (Idiot)
1 person)

Claims (1)

[Claims] A plurality of uninterruptible power supplies that are composed of a rectifier having a constant voltage control function and a constant current control function and an inverter that converts the DC output of the rectifier into AC, and in which the DC output of the rectifier is directly connected to a common storage battery. A control device for an uninterruptible power supply, characterized in that a constant current control circuit is provided that detects a charging current for charging the storage battery of each of the rectifiers and limits this charging current to a predetermined level or less.