JPS5810949B2 - Parallel operation inverter power supply device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a parallel operation inverter power supply device that cuts off the load from one inverter when an abnormality occurs in one of the inverters during parallel operation of two inverters.

An inverter that uses a semiconductor switch such as a transistor or SIRISK as an inverter switch, converts direct current to alternating current by driving the switch in response to a drive signal from an inverter drive signal circuit, and then obtains a sine wave alternating current output using a sine filter. In order to operate multiple inverters in parallel, the frequency, phase, voltage value, etc. of the AC output voltage of the inverters must almost match.

The frequency and phase can be easily matched by using a common source oscillator for each inverter, and the voltage value can be matched by providing a voltage control system to each inverter.

As an inverter having a voltage control system, a bridge inverter shown in FIG. 1 is generally used.

Figure 1 shows transistors 81 to S4 as semiconductor switches.
This is an example using .

FIG. 2 explains the operation of this circuit, and shows the inverter drive signals X, X, Y.

During the period when Y exists, the corresponding transistors are in the on state, and the transistors whose signal is zero are in the off state.

The signals X and X or Y and Y never exist at the same time, and the lengths of the periods in which the signals exist are equal.

During the period when signals X and Y or X and Y exist simultaneously, the DC power supply voltage E is applied between the AC terminals zz' and z'.

is applied. Period during which signals X and Y exist and signals X and Y
During the period in which the voltage is present, the voltage polarity between the AC terminals z and z' is different, resulting in an AC voltage shown in FIG. 2V.

Here, the period during which signals X and Y or X and Y exist simultaneously is called voltage control angle θ, and a variable time circuit is provided between the X-X inverter drive signal circuit and the Y-Y inverter drive signal circuit to control the voltage. By changing the control angle θ, the pulse width of the AC voltage V changes, and the AC output voltage value after the sine filter can be adjusted.

In such an inverter power supply system that uses two inverters to operate in parallel, if the voltage control system of one inverter breaks down for some reason and the voltage control angle of that inverter becomes too large or too small, When the output voltage of the inverter increases or decreases, an output voltage difference occurs between the inverters, and this voltage difference generates a cross current between the inverters.This cross current may overheat the equipment inside each inverter or cause the inverter to This will cause the output voltage of the device to drop, or in the worst case, the inverter will fail in commutation and stop, which will have a negative impact on the load.
It is very important to quickly identify the inverter that has caused the above abnormality, disconnect it from the load, and continue supplying power to the load from another healthy inverter, a so-called selective shutdown.

One of the conventional selective shutoff methods is that if an abnormality occurs in any inverter that causes the voltage control angle to be too large or too small, a cross current will occur between the imparks and the output voltage of the power supply will increase, albeit slightly. By focusing on the directionality of the phase lead or lag of the cross current flowing through each inverter and the increment or decrement of the output voltage, and by combining these signals, it is possible to determine which inverter A method has been proposed in which it is determined whether the voltage control angle is too large or too small, and selectively shuts off an abnormal inverter.

However, such a selective shutoff method requires a current phase discrimination detection element such as a current phase detection element to detect the direction of the phase lead/lag of the cross current, and at the same time, the increment or decrement of the output voltage of the power supply is normal. Compared to the output voltage of the device, the fluctuation range of increments and decrements is extremely small (for example, within about 1%)
Therefore, extremely accurate voltage detection relays are required.

Therefore, there is a drawback that devices for making detection judgments, such as a current phase discrimination detector and a highly accurate voltage detector, are expensive.

Another general selective shutoff method is to detect the output reactive current of each inverter operated in parallel, compare the average value with the output reactive current value of each inverter, and then A method of selectively shutting off inverters has also been proposed.

However, with this selective shutoff method, the difference in output reactive current can be easily determined when three or more inverters are operated in parallel, but the difference in output reactive current can be easily determined when two inverters are operated in parallel. Since they may be the same depending on the load conditions of the power supply device, it is difficult to determine whether the voltage control angle of the inverter is too large or too small.

An object of the present invention is to provide a parallel-operating inverter that, when an abnormality occurs in one of the inverters during parallel operation of two inverters, can disconnect the abnormal inverter from the load without the above-mentioned drawbacks. There is a power supply to provide.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 3 shows an embodiment of the parallel operation inverter power supply device according to the present invention, where 1 is a DC power supply, 2 is the parallel operation inverter power supply device of this embodiment, and 3 is a load.

4 and 5 are equipped with a plurality of semiconductor switches as inverter switches, an inverter drive signal circuit that provides a drive signal to these switches, a cross-current compensation circuit, etc., and are equipped with two cross-current compensation circuits that operate in parallel to supply AC power to the load. Inverters 6 and 7 are each 4°5 inverter with a cross current compensation circuit.
A voltage control angle detector 8 detects the voltage phase angle by pulse width from each inverter drive signal circuit, and 8 is a voltage control angle detector 6.
, 1, the output signal θ1. This is a voltage control angle comparison circuit that receives θ2 and determines the magnitude of the voltage control angle of the inverters 4 and 5 with a cross current compensation circuit.

9 is a device output voltage detector that detects whether the output voltage of the power supply device 2 has increased or decreased from a specified value; 10 is an output signal a of the voltage control angle comparison circuit 8 and an output signal of the device output voltage detector 9; This is an abnormal inverter discriminating circuit that receives a signal, identifies an abnormal inverter, and outputs a selection cutoff signal c or d for disconnecting the abnormal inverter from the load 3.

Reference numerals 11 and 12 indicate cutoff circuits that cut off the abnormal inverter from the load using signals c and d from the abnormal inverter discrimination circuit 10.

These 6 to 12 components constitute the parallel operation inverter power supply device 2.

Next, a method for selectively shutting off an abnormal inverter in such a parallel operation inverter power supply device 2 will be described.

In this power supply device 2, the two inverters 4 and 5 that operate in parallel are equipped with a cross current compensation circuit, so if each inverter 4 and 5 are healthy, the voltage control angles are equal and each impark mutually The output voltage difference between the inverters 4 and 5 is also zero, and the inverters 4 and 5 are operated so as to reduce the cross current to zero, and the output currents of each inverter 4 and 5 are shared evenly to maintain the output voltage of the power supply 2 at the specified value. .

In this manner, when the output voltage of the power supply device 2 is at the specified value and the voltage control angles of the inverters 4 and 5 are the same, the abnormal inverter discrimination circuit 10 does not issue a selective cutoff signal.

Next, if the voltage control system of one inverter becomes abnormal for some reason and the voltage control angle of that inverter attempts to become too large or too small, the other healthy inverter will be connected to the cross current compensation circuit. The inverter's voltage control angle follows the direction in which it becomes approximately equal to the voltage control angle of the abnormal inverter, and performs a compensation operation so as not to increase the output voltage difference between the inverters, that is, not to increase the cross current. Therefore, the output voltage of the power supply device also increases or decreases significantly from the normal voltage value.

Furthermore, when the compensation limit is exceeded, a difference occurs in the voltage control angles of each inverter, and the degree of unbalance in the output current distribution also becomes excessive than the specified value.

When eC, the voltage control angle of the abnormal inverter on the side that is trying to increase the inverter output voltage is larger than that of other normal inverters, and the voltage control angle of the abnormal inverter on the side that is trying to decrease the inverter output voltage is larger than that of other normal inverters. is smaller than that of other normal inverters.

Since such an abnormal phenomenon occurs, the function of the present invention is to check the phenomenon in which the voltage control angle of one inverter becomes too large or too small due to some reason, and in this case, to check whether the output voltage of the power supply device is normal or not. It detects two phenomena: a large increase or decrease from the value voltage, and combines both signals to determine an abnormal inverter with an excessive or insufficient voltage control angle using the following matrix, and disconnects it from the load and disconnects it from the device. I try to keep the output healthy.

Here, what has been explained above will be explained in more detail.

Now, if an abnormality occurs in the direction in which the output voltage of the inverter 4 increases, the device output voltage increases, and this is detected by the device output voltage detector 9.

At this time, the voltage control angle of inverters 4 and 5 is
is larger than that of the inverter 5, and this is detected by the voltage control angle detectors 6 and 7, and the output signal θ1. The voltage control angle comparison circuit 8 makes a determination based on θ2, and the abnormal impark determination circuit 10 outputs a selective shutdown signal c to cause the shutdown circuit 11 to perform a shutdown operation.

Conversely, if a failure occurs in the direction in which the output voltage of the inverter 4 decreases, the device output voltage decreases, and this is detected by the device output voltage detector 9.

At this time, the voltage control angle of each impark is smaller for impark 4 than for inverter 5, and is detected by voltage control angle detectors 6 and 7 in the same manner as described above, and discriminated by voltage control angle comparison circuit 8. The abnormal inverter discrimination circuit 10 then disconnects the cutoff circuit 1.
A selective cut-off signal C is issued to make the cut-off operation of 1.

In this way, the inverter 4 that has become abnormal is selectively disconnected from the load 3.

If the inverter 5 has a similar failure, a similar operation will be performed and the inverter 5 will be selectively shut off, but a detailed explanation thereof will be omitted.

According to experiments, when the cross current flows in an amount exceeding 10% of the output current to be shared by each inverter, the device output voltage exceeds 5%, and the fluctuation width of the device output voltage is reduced compared to the conventional method. It has been found that the detection of fluctuations in the device output voltage is so greatly magnified that a commonly used common voltage sensing relay is sufficient.

As explained above, in the present invention, the device output voltage and the voltage control angle of each inverter are detected, and an abnormal inverter is determined based on the combination of their magnitudes, so it is possible to operate two inverters in parallel, which was previously difficult. Selective shutoff of inverters can be easily performed.

Furthermore, according to the present invention, the fluctuation range of the device output voltage is greatly expanded in response to an increase in cross current, so it is sufficient to detect fluctuations in the device output voltage using a commonly used general voltage detection relay, etc. can.

In particular, in the present invention, since a voltage control angle detector is used, the voltage control angle can be easily detected by the pulse width from the inverter drive signal circuit in the inverter with a cross current compensation circuit, and the voltage control angle comparison circuit is used. Since the magnitude of the pulse width can be easily compared digitally, these voltage control angle detectors and voltage control angle comparison circuits do not need to be small and highly accurate side tubes, regardless of power.

Therefore, according to the present invention, highly reliable selective shutoff can be performed without using a highly accurate detector.

Further, since the output voltage of the power supply device and the voltage control angle of each inverter change extremely quickly to follow the abnormality, according to the present invention, selective cutoff can be performed extremely quickly.
Therefore, there is an advantage that the load is not adversely affected.

[Brief explanation of drawings]

Figure 1 is a circuit diagram showing an example of a bridge inverter, Figure 2 is a circuit diagram showing an example of a bridge inverter.
The figure is a waveform diagram showing an example of a control method for a bridge inverter, and FIG. 3 is a block diagram showing an embodiment of a parallel operation inverter power supply device according to the present invention. 1...DC power supply, 2...Parallel operation inverter power supply device, 3...Load, 4, 5...
... Inverter with cross current compensation circuit, 6, 7 ... Voltage control angle detector, 8 ... Voltage control angle comparison circuit,
9... Device output voltage detector, 10...
Abnormal inverter discrimination circuit, 11゜12... Cutoff circuit.

Claims (1)

[Claims] In a parallel operation inverter power supply system that cuts off the inverter in which an abnormality has occurred from the load during parallel operation of 12 inverters, two inverters with cross-current compensation circuits are operated in parallel, and the voltage control angle of each of the inverters is and a device output voltage detector that detects whether the device output voltage of the power supply device has increased or decreased from a specified value, respectively, and a device output voltage detector that is respectively connected to and corresponds to the downstream stage of each of the inverters. A cutoff circuit that disconnects the inverter from the load, and a signal from each of the voltage control angle detectors and a signal from the device output voltage detector are input, and when the device output voltage increases beyond a specified value, the side with the larger voltage control angle Outputs a selective cutoff signal that disconnects the inverter from the load to the cutoff circuit connected to that inverter, and also outputs a selective cutoff signal that disconnects the inverter with the smaller voltage control angle from the load when the device output voltage decreases below the specified value. 1. A parallel operation inverter power supply device comprising: an abnormal inverter discrimination circuit that outputs a signal to a cutoff circuit connected to the inverter.