JPH05176461A - Ac power supply - Google Patents

Abstract

PURPOSE:To provide an AC power supply comprising a first feeder for feeding power from an AC power supply through an AC switch to a load, and a second feeder for feeding power from the AC power supply through a rectifier, an inverter and an AC switch to the load, wherein respective feeders can be switched uninterruptibly in safety. CONSTITUTION:An output voltage of an inverter unit 6 is detected through an output voltage detector 11 and then rectified and averaged through an averaging circuit l3. The output from the averaging circuit 13 is then compared through a first comparator 14 with a voltage reference and upper and lower limits are set for thus compared output by means of a limit circuit 10. An output from the limit circuit 10 is fed through a first PI controller 15 to a multiplier 17 where it is multiplied by a unit amplitude sine wave. The output of the multiplier 17 is then compared through a second comparator 18 with the output of the output voltage detector 11 and thus compared output is fed through a second PI controller 19 to a PWM pulse generating circuit 20 thus obtaining a control signal for the inverter unit 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an AC power supply device, and more specifically, a first power supply path for supplying power to a load from a first AC power supply through an AC switch, and a second power supply path.
An AC power supply device having a rectifier device, an inverter device, and a second power supply path for supplying power to the load via the AC switch, and capable of switching to each other stably and without interruption Is.

[0002]

2. Description of the Related Art In recent years, loads requiring uninterruptible power supply, no interruption, and loads requiring high-accuracy input voltage characteristics have increased, and as an AC power supply device for supplying AC power to these loads, A first power supply path for supplying power from the first AC power supply via the AC switch; and a second power supply path for supplying power from the second AC power supply via the rectifying device, the inverter device and the AC switch. A storage battery is used between the rectifying device and the inverter device.

A conventional example of such an AC power supply device will be described with reference to FIG.

In FIG. 4, 1 is a first AC power supply, 2 is a second AC power supply, and a first power supply path for supplying power from the first AC power supply 1 to the load 4 via the AC switch 3. A second power supply path for supplying power from the second AC power supply 2 to the load 4 via the rectifying device 5, the inverter device 6, and the AC switch 3; and the rectifying device 5 and the inverter device 6
And a storage battery 7 between the storage device and the load so that the load can be supplied to the load without interruption by the AC switch 3, and the DC power from the storage battery 7 is supplied to the AC power by the inverter device 6 at the time of a power failure of each AC power supply. It is configured so as to be converted into the electric power to be supplied to the load.

A ripple is removed from the output of the rectifier 5 by the capacitor 8 to charge the storage battery 7, and the output of the inverter 6 is the reactor 9.
The AC filter 9 including the capacitor 1 and the capacitor 92 removes high-frequency components and supplies power to the load 4.

The AC switch 3 is the first AC power source 1
To the load 4 from the first mechanical contact 31, second
The second mechanical contact 32 for supplying power from the AC power source 2 to the load 4 and the semiconductor switch 33 in which the thyristor is connected in antiparallel.

In the inverter device 6, the output voltage V _INV is detected by the output voltage detector 11 and the diode 1
After being rectified by 2, the averaging circuit 13 converts the averaged DC voltage V _AVE . This DC voltage V _AVE is compared with the reference voltage V _REF by the first comparator 14, and the first PI controller 15 for stabilizing the control system.
_Is converted to an error voltage V _ERR via. This error voltage V
_ERR is a unit amplitude sine wave V synchronized with the first AC power supply 1 generated from the unit amplitude sine wave generator 16 by the multiplier 17.
_It is multiplied by _RS and converted into a reference sine wave V _SIN having average value information of the output voltage V _INV . This reference sine wave V
The second comparator 18 compares the _SIN with the output voltage V _INV, and the second PI controller 19 for stabilizing the control system.
It is input to the PWM pulse generation circuit 20 which obtains the control signal of the inverter device 6 via.

The PWM pulse generation circuit 20 operates so as to generate a PWM pulse that makes the deviation of the output voltage V _{INV from} the reference sine wave V _SIN zero, and the obtained pulse is amplified by the driver circuit 21. And is sent to the inverter device 6.

Next, the operation when switching from the first power feeding path to the second power feeding path will be described with reference to the timing chart of FIG.

In FIG. 5, (a) shows the first mechanical contact 3
1 is an operation diagram, (b) is an operation diagram of the semiconductor switch 33,
(C) is an operation diagram of the second mechanical contact 32. Before time t _0, only the first mechanical contact 31 is turned on and power is supplied to the load 4 from the first power supply path. Then, the semiconductor switch 33 is turned on at time t ₀ , and power is supplied to the load 4 from the first power supply path through both the first mechanical contact 31 and the semiconductor switch 33 until time t ₁ . The first mechanical contact 31 at time t ₁ is turned off, until the time t ₂ is powered from a first feed line through only the semiconductor switch 33 to the load 4. The second mechanical contact 32 is turned on at time t _2, the semiconductor switch 3 at time t ₃
Until the switch 3 is turned off, the load 4 is fed from the first and second power feeding paths.
Is powered. Then, when the semiconductor switch 33 is turned off at time t ₃ , power is supplied to the load 4 from the second power feeding path via only the second mechanical contact 32, and the non-instantaneous switching is performed as shown in FIG. 5D. .

[0011]

In the above-described conventional AC power supply device, the inverter device 6 is operated without load until time t _2, so that the reference sine wave V shown in FIG.
_{The SIN} is based on the average value information of the output voltage when there is no load, but when the second mechanical contact 32 is turned on at time t ₂ and the inverter device 6 supplies power to the load 4, It is based on the average value information of the output voltage corresponding to the output current value, and the output current from the first AC power supply 1 decreases as shown in FIGS. Output current starts to flow. At this time, when the output voltage of the inverter device 6 is higher than the output voltage of the first AC power source 1, a cross current flows from the inverter device 6 to the first AC power source 1 having a low internal impedance, and the output current of the inverter device 6 is increased. Is increased, the amplitude of the reference sine wave V _SIN is also increased as shown in FIG. 5 (g), and the output current of the inverter device 6 is further increased. Then, this increased amplitude continues even if the semiconductor switch 33 is turned off at time t ₃ and the power supply from the first AC power supply 1 is stopped.
There is a problem that the voltage applied to the load 4 becomes high.

[0012]

In order to solve the above-mentioned problems, the present invention provides a first power supply path for supplying power from a first AC power supply to a load via an AC switch, and a second AC power supply for a rectifying device. An inverter device and a second power supply path for supplying power to the load via the AC switch, wherein the power supply path can be switched without interruption by the AC switch. An output voltage detector for detecting the output voltage of the power feeding path of No. 2, and an averaging circuit for rectifying the output of this output voltage detector to average it.
A first comparator for comparing the output of the averaging circuit with a reference voltage, a limit circuit for setting an upper limit value and a lower limit value for the output of the first comparator, and an output of the limit circuit for PI A first PI controller for controlling and the first P controller
A multiplier that multiplies the output of the I controller by the unit amplitude sine wave from the unit amplitude sine wave generator, a second comparator that compares the output of this multiplier with the output of the output voltage detector, and a second comparator
And a PWM pulse generation circuit for obtaining a control signal for the inverter device from the output of the second PI controller.

[0013]

[Operation] Therefore, in the present invention, since the upper limit value and the lower limit value are set for the output of the first comparator by the limit circuit, even if the output current of the inverter device increases,
Since the reference sine wave based on the average value information of the output voltage corresponding to the output current value is not generated, the increase in the amplitude can be clamped, and it is applied to the load even after the power supply from the first AC power supply is stopped. Voltage does not increase.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram of an AC power supply device according to the present invention. Parts having the same functions as in FIG.

The feature of the present invention resides in the first feature of the apparatus of FIG.
The limit circuit 10 is inserted between the comparator 14 and the first PI controller 15.

The limit circuit 10 is, as shown in FIG.
The comparator 102 compares the output of the first comparator 14 with the output immediately before held by the holding circuit 101, inputs the output to the limit setter 103 to determine the upper limit value and the lower limit value, and then the adder. It is input to 104, added to the output just before being held, and input to the first PI controller 15.

In the AC power supply device of the present invention described above,
The operation when switching from the first power feeding path to the second power feeding path will be described with reference to the timing chart of FIG. Note that FIG.
The symbols (a) to (g) are common to the symbols (a) to (g) in FIG.

In FIG. 3, when the second mechanical contact 32 is turned on at time t ₂ and power is supplied from the inverter device 6 to the load 4, as shown in FIGS. 3 (e) and 3 (f), Output current from the AC power supply 1 of
The output current from starts to flow. At this time, when the output voltage of the inverter device 6 is higher than the output voltage of the first AC power source 1, a cross current flows from the inverter device 6 to the first AC power source 1 having a low internal impedance. Since the upper limit value and the lower limit value are set at the input of the first PI controller 15, the amplitude of the reference sine wave V _SIN is slightly increased as shown in FIG. It does not increase the current. Therefore,
Even if the semiconductor switch 33 is turned off at time t ₃ and the power supply from the first AC power supply 1 is stopped, the voltage applied to the load 4 does not increase.

Needless to say, the upper limit value and the lower limit value are set within a range that does not impair the transient fluctuation characteristics of the inverter device 6.

[0020]

As described above, the present invention provides
Mutual switching between the first power supply path and the second power supply path can be performed stably and without interruption, and the performance of the AC power supply device can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram of an AC power supply device of the present invention.

FIG. 2 is a block diagram of a limit circuit used in the device of the present invention.

FIG. 3 is a timing chart when switching the device of the present invention.

FIG. 4 is a block diagram of a conventional AC power supply device.

FIG. 5 is a timing chart when switching the conventional device.

[Explanation of symbols]

 1 1st AC power supply 2 2nd AC power supply 3 AC switch 4 Load 5 Rectifier 6 Inverter device 10 Limit circuit 11 Output voltage detector 12 Diode 13 Average value circuit 14 1st comparator 15 1st PI control 16 Unit amplitude sine wave generator 17 Multiplier 18 Second comparator 19 Second PI controller 20 PWM pulse generation circuit 21 Driver circuit

Claims (1)

[Claims] 1. A first power supply path for supplying power to a load from a first AC power supply via an AC switch, and a power supply to a load from a second AC power supply via a rectifying device, an inverter device, and the AC switch. In the AC power supply device, which has a second power supply line and which enables switching of each power supply line by the AC switch without interruption, an output voltage detector for detecting an output voltage of the second power supply line. And an averaging circuit that rectifies the output of the output voltage detector and averages it, and a first comparison circuit that compares the output of the averaging circuit with a reference voltage.
, A limit circuit for setting an upper limit value and a lower limit value for the output of the first comparator, a first PI controller for PI controlling the output of the limit circuit, and a first PI controller A multiplier that multiplies the output of the PI controller by the unit amplitude sine wave from the unit amplitude sine wave generator, a second comparator that compares the output of the multiplier with the output of the output voltage detector, and a second comparator AC power supply device comprising a second PI controller that performs PI control on the output of the comparator, and a PWM pulse generation circuit that obtains a control signal for the inverter device from the output of the second PI controller.