JPS6130967A - Parallel operation device of inverter - Google Patents

Abstract

PURPOSE:To improve the reliability and the safety by providing input voltage detecting means of an inverter, and controlling the output frequency at the rise side by the rise of the voltage, thereby continuing normal parallel operation. CONSTITUTION:Two no-break power sources 1, 2 are operated in parallel to supply power through a switch to a load. The power sources 1, 2 convert DC voltage rectified from AC input voltage E by a rectifier 11 and smoothed by a capacitor 12 by an inverter 13 to the AC voltage of the prescribed voltage and frequency to output it. Controllers 6, 7 for controlling the output effective and reactive powers of the power sources 1, 2 in response to the sharing amounts have effective-reactive power detector 60, frequency control unit 61, and a detector 64 for detecting the fact that the input voltage of the inverter 13 rises from the prescribed value, and control the effective power by the output of the detector 64 to rise side.

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 convert storage battery voltage into AC voltage using an inverter and output it, but when 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, this control device detects active power and reactive power, and controls the output frequency based on the detected value of active power. By controlling the output voltage value based on the detected value of reactive power, it is configured to share the power to the load.

[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 occurs, causing 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 for Solving the Problems 2] The present invention has been made to solve the above problems, and includes a detection means for detecting that the input voltage of the inverter has risen above a predetermined value. By controlling the output frequency to the rising side based on the detection output of the detection means, there is provided an inverter parallel operation device that can maintain a balanced share of active power and continue normal parallel operation.

〔Example〕 Hereinafter, the present invention will be described 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 Figure 1, uninterruptible power supplies 1 and 2
1 AC input voltage E as shown representatively for device 1
is rectified by a rectifier circuit 11, the rectified DC voltage is smoothed by a capacitor 12, and the smoothed DC voltage is further converted into AC power of a predetermined voltage and one frequency by an inverter 13 and output. There is.

The output power from each device 1, 2 is supplied to a load 3 via a switch 4.5.

On the other hand, a control device 6 that controls the output active power P and the output reactive power Q of each device 1 and 2 according to their respective share;
7 represents the control device 6, as shown in FIG.
2. Reactive power detection section 60 (hereinafter abbreviated as PQ detection section) 2. Frequency control section 61. Voltage control section 62. Gate logic section 6
3, the supply voltage EO to the load 3 detected via the transformer 8 and the current transformer 9. The active power P and reactive power Q of each power supply device 1, 2 are detected by the PQ detection unit ω based on the load current factor 0 detected by the IOK, and based on the detected value of the active power P, the gate logic unit 63 detects the inverter 1.
The frequency control unit 61 controls the frequency of the gate signal given to
The voltage control unit 62 controls the gate signal width of the inverter 13 based on S, so that each power supply device 1゜2 can share the active power P and the reactive power Q on a one-to-one basis and supply it to the load 3. It is configured.

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, the effective power P of the power supply device 2
When the amount shared by one of the power supply devices 1 increases, the active power corresponding to the difference flows into the DC side through the diode D connected anti-parallel to the transistor TRK of the inverter 13, and the DC voltage increases. It will rise.

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

That is, the DC input voltage of the inverter 13 is stepped down to a predetermined voltage by the DC ν DC converter 640, and the output voltage VD of this converter 640 and the set voltage v8 set by the setting device 641 are compared by the comparator 642, and VD> V
When it becomes ll+, the frequency control section 6 is output from the comparator 642.
A predetermined voltage Pα is added to the input of the operational amplifier 610 of No. 1. A voltage PO representing a detected value of active power P is inputted to this operational amplifier 610 from an active power calculation unit 611, and its output is output from a voltage controlled oscillator 61 that controls the output frequency.
2 is supplied.

Therefore, when VD>V8, the output voltage Pα of the comparator 642 is added to the input of the operational amplifier 610, and the output signal frequency of the voltage controlled oscillator 612 is increased by an amount corresponding to the voltage Pα. Become.

The output signal of this voltage controlled oscillator 612 is supplied to the 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 VD≦ys, the voltage controlled oscillator 61
The output signal frequency of No. 2 increases or decreases in inverse proportion to the detected value of active power P, and is controlled so that a predetermined amount of active power P is sent out.

On the other hand, the voltage control unit 62 is the detected value of the reactive power Q detected by the reactive power calculation unit 613 of the frequency control unit 61.

The output voltage EO detected by the transformer 8 and the set value E8 of the output voltage are added and subtracted by the voltage control amplifier 620, and the result is input to the comparator 621, which generates a triangular wave in synchronization with the output signal frequency of the voltage control oscillator 612. By comparing the output voltage of the voltage amplifier 620 with the triangular wave generated from the generator 622 and applying a logic "1" signal to the gate logic unit 62 while the output voltage of the voltage amplifier 620 is smaller than the voltage value of the triangular wave, the output voltage EO
is configured to control.

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 and uninterruptible power supplies in parallel, even if the amount of active power shared becomes unbalanced, it can be immediately controlled to a balanced relationship, so that normal parallel operation can be achieved. This has excellent effects in that it allows continuous operation and improves reliability and stability.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention, and 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, ω...PQ detection section, 61...Frequency control section, 62...Voltage control section, 63...Gate logic section, 64...Detection circuit.

Claims (1)

[Claims] 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 value of Each control device is provided with a detection means for detecting that the value has increased from a predetermined value, and the detection output of this detection means is used to control the output frequency to the increasing side, thereby maintaining a balanced share of active power and performing parallel operation. Features: Inverter parallel operation device.