JPH0559671B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a parallel operation device for inverters used in uninterruptible power supplies and the like.

[Conventional technology]

Generally, uninterruptible power supplies are configured to use an inverter to convert storage battery voltage to AC voltage and output it, but if the load capacity is large, such uninterruptible power supplies may be operated in parallel. .

When operating uninterruptible power supplies with such inverters in parallel, each device does not send or receive control signals, and operates by controlling its own output power within the range of output power assigned to each device. There is a parallel operation method called the individual control method.

Specifically, in this individual control method, a control device is provided for each uninterruptible power supply, and this control device detects active power and reactive power, and controls the output frequency based on the detected value of active power. In addition, by controlling the output voltage value based on the detected value of reactive power, the power to the load is shared.

[Problem that the invention seeks to solve]

However, in this individual control method, if there is an error in the active power settings between each device, the amount of active power supplied to a specific device will increase, and the active power will be reversed to other devices. This phenomenon caused the DC input voltage of the inverter to rise, making normal parallel operation impossible. Such problems occur not only when uninterruptible power supplies are operated in parallel, but also when inverters are operated in parallel.

[Means and actions for solving problems]

The present invention has been made to solve the above-mentioned problems, and includes a detection means for detecting that the input voltage of the inverter has risen above a predetermined value, and the output frequency is determined by the detection output of this detection means. An object of the present invention is to provide an inverter parallel operation device that can maintain normal parallel operation by maintaining the share of active power in a balanced manner by controlling the inverters to the rising side.

〔Example〕

Hereinafter, the present invention will be explained in detail based on Examples.

FIG. 1 is a block diagram showing an embodiment of an uninterruptible power supply to which the present invention is applied. Here, two uninterruptible power supplies 1 and 2 are operated in parallel to supply power to a load 3. An example is shown. In FIG. 1, uninterruptible power supplies 1 and 2 convert AC input voltage E into rectifier circuit 1, as shown in FIG.
1, the rectified DC voltage is smoothed by a capacitor 12, and the smoothed DC voltage is further converted into an AC voltage of a predetermined voltage and frequency by an inverter 13 and output. ing. The output voltage from each device 1, 2 is supplied to a load 3 via switches 4, 5.

On the other hand, control devices 6 and 7, which control the output active power P and output reactive power Q of each device 1 and 2 according to their respective assigned amounts, have an effective-invalid state, as shown in the control device 6 as a representative. Power detection unit 60 (hereinafter referred to as
It is composed of a frequency control section 61, a voltage control section 62, and a gate _logic section 63. The active power P and reactive power Q of each power supply device 1, 2 are detected by the PQ detection unit 60 based on the detected load current I _O , and the gate logic unit 63 detects the active power P based on the detected value of the active power P.
The frequency control unit 61 controls the frequency of the gate signal given to the inverter 13 from
The voltage control unit 62 controls the gate signal of the inverter 13 based on the detected value and the set value E _S of the output voltage, and each power supply device 1, 2 controls the active power P and the reactive power Q.
It is configured such that it can be distributed to the load 3 on a one-to-one basis.

In this case, at the start of parallel operation, one power supply device 1 starts operating first, and the switch 4 is closed when the output voltage phase of this device 1 is synchronized with the output voltage phase of the subsequent device 2. Control for this phase synchronization is performed by a phase synchronization circuit (not shown).

By the way, in this configuration, when the share of the active power P of the power supply device 2 becomes larger than the share of the active power P of the power supply device 1, the active power corresponding to the difference is transferred to the diode connected in antiparallel to the transistor TR of the inverter 13. It flows into the DC side via D and the DC voltage increases.

Accordingly, in the present invention, as shown in detail in FIG. The configuration is such that the effective power P is controlled to the rising side.

That is, the DC output voltage of the inverter 13 is stepped down to a predetermined voltage by the DC/DC converter 640, and the output voltage of this converter 640 V _D
A comparator 642 compares the set voltage _VS set by the setting device 641, and if V _D > _VS , the comparator 642 outputs the voltage to the operational amplifier 6 of the frequency control section 61.
A predetermined voltage Pα is added to the input of 10. A voltage P _O representing a detected value of active power P is inputted to this operational amplifier 610 from an active power calculation section 611.
Its output is fed to a voltage controlled oscillator 612 which controls the output frequency.

Therefore, when V _D > V _S , the operational amplifier 6
The output voltage Pα of the comparator 642 is added to the input of the voltage control type oscillator 612, and the output signal frequency of the voltage controlled oscillator 612 increases by an amount corresponding to the voltage Pα. The output signal of this voltage controlled oscillator 612 is supplied to a gate logic section 63. As a result, the output frequency of the inverter 13 increases by an amount corresponding to the voltage Pα, and the effective power P also increases.

Note that under the condition of V _D ≦ V _S , the output signal frequency of the voltage controlled oscillator 612 increases or decreases in inverse proportion to the detected value of the active power P, so that a predetermined share of the active power P is sent out. controlled by.

On the other hand, the voltage control unit 62 uses the detection value of the reactive power Q detected by the reactive power calculation unit 613 of the frequency control unit 61, the output voltage E _O detected by the transformer 8, and the set value E _S of the output voltage for voltage control. The amplifier 620 performs addition and subtraction, and the result is input to a comparator 621 and compared with a triangular wave generated from a triangular wave generator 622 in synchronization with the output signal frequency of the voltage controlled oscillator 612. By applying a logic "1" signal to the gate logic unit 62 during a range smaller than the voltage value of
Configured to control E _O.

Therefore, according to this embodiment, even if an unbalance occurs in the shared amount of the active power P, this unbalance is corrected by the detection output of the detection circuit 64, so that the two uninterruptible power supplies 1, Normal parallel operation of the two can be continued.

In addition, although the number of uninterruptible power supplies operated in parallel in the embodiment is two, it is possible to control the number of uninterruptible power supplies in the same manner with more than two. Furthermore, it goes without saying that the present invention can be applied not only to uninterruptible power supplies but also to parallel operation of inverters.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, when operating inverters or uninterruptible power supplies in parallel, even if the shared amount of active power becomes unbalanced, it can be immediately controlled to a balanced relationship, so that normal parallel operation can be achieved. This has the excellent effect of allowing continuous operation and improving reliability and stability.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention;
FIG. 2 is a block diagram showing the detailed configuration of the control device in FIG. 1. 1, 2... Uninterruptible power supply, 3... Load, 6,
7...Control device, 60...PQ detection section, 61...
Frequency control section, 62... Voltage control section, 63... Gate logic section, 64... Detection circuit.

Claims (1)

[Claims] 1 It is installed corresponding to each of multiple inverters operated in parallel, detects the active power and reactive power output from the corresponding inverter, controls the output frequency based on the detected value of active power, and controls the reactive power. In an inverter parallel operation device that is equipped with a control device that controls the output voltage value based on the detected power value, and that operates in parallel by sharing the active power and reactive power that each inverter should supply to the load, the inverter's DC Each control device is provided with a detection means for detecting that the voltage has risen above a predetermined value, and the output frequency is controlled to the rising side based on the detection output of this detection means, and the sharing of active power is maintained in balance for parallel operation. An inverter parallel operation device featuring: