JPH07231580A - Synchronous control method for uninterruptible power supply - Google Patents

Abstract

PURPOSE:To follow up the frequency quickly by deciding the direction for controlling the frequency based on the direction at the time when the phase difference passes 180 deg., controlling the frequency uniformly only in that direction, deciding the direction where the phase difference passes 0 deg. when both frequencies are close each other, and resetting the control based on a normal phase difference signal. CONSTITUTION:The synchronous control method for an uninterruptible power supply comprises a function for detecting that the output from a phase difference detecting function section 220 has passed 180 deg. and 0 deg. along with the passing direction thereof, and a function generating a signal for increasing/decreasing the frequency of power supply. The method further comprises a function for selecting an output between the section 220 and a setting function section 250 depending on the output from a decision function section 230. When an output from the section 220 passes 180 deg., any one set output is selected depending on the passing direction of output and the output frequency of one power supply is controlled. Control of the section 220 is reset depending on the passing direction of output therefrom when the output passes 0 deg..

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an uninterruptible power supply device applied to a computer power supply or the like, and more particularly to a synchronous control method in a uninterruptible power supply device which is switched from a commercial power supply without interruption or in parallel. It is about.

[0002]

2. Description of the Related Art An uninterruptible power supply (hereinafter referred to as UPS) is used as a power source for equipment such as computers and instrumentation equipment that requires a stable and highly reliable power source. UP
In S, in order to further improve reliability, multiple UPS's are operated in parallel, or are always operated in synchronization with a commercial power source.
When a UPS fails, a commercial power source is promptly connected to the load device, and the UPS is disconnected.

FIG. 4 shows the structure of a power supply system for a commercial synchronous UPS, where 1 is a commercial power supply, 2 is a UPS, 3 is a load device, and 4 and 5 are switches. Here, in UPS2, 21 is a forward conversion unit composed of a rectifying circuit and a DC smoothing circuit, 22
Is an inverse conversion unit composed of an inverter circuit, an output transformer, and an AC filter circuit, and 20 is a control unit.

[0004] As a normal power transmission form of the power supply system,
There are a mode in which power is transmitted from the commercial power source 1 to the load device 3 via the switch 4, and a mode in which power is transmitted via the UPS 2 and the switch 5. In either case, when the commercial power supply 1 or the UPS 2 is abnormal, a measure is taken to instantaneously switch to the other one to eliminate a momentary interruption of the voltage transmitted to the load device 3.

For example, the commercial power source 1 is always supplied to the load device 3.
In a system in which electric power is supplied via the UPS 2 and the switch 5, the switch 4 is closed after the UPS 2 fails, and then the switch 5 is opened. The electric power is supplied via. In the system that operates in this way, the load device 3
In order to prevent a sudden change in the voltage waveform when switching the power supply path to the UPS, it is necessary that the output voltage of the UPS 2 is always synchronized with the commercial power source 1 and that the phase difference is zero.

The same applies to a system that constantly transmits power from a commercial power source to a load. The control unit 20 performs this function.
Here, the control unit 20 comprises a phase controller 200, an amplifier 201, a reference frequency setting device 202 and an adder 203. The phase controller 200 has a phase difference detecting function and receives the power supply voltage 101 of the commercial power supply 1 and the output voltage 102 of the UPS 2 as inputs and detects the phase difference between two voltage waveforms.

An example of the phase difference detection circuit having this phase difference detection function is as shown in FIG. In FIG. 5, 211, 2
Reference numeral 12 is a (3 phase / 2 phase) conversion circuit, and 213 is an arithmetic circuit. The conversion circuit 211 receives the power supply voltage 101 of the commercial power supply 1 as input, performs dq conversion, and outputs a d-axis component signal V1d and a q-axis component signal V1.
Output 1q. The conversion circuit 212 outputs the output voltage of UPS2 1
02 is input to perform dq conversion, and d-axis component signals V2d, q
The axis signal V2q is output. The arithmetic circuit 213 calculates the following equation and outputs the phase difference signal S0.

(V1d) * (V2q)-(V1q) * (V2d) (1)

The characteristic of the phase difference signal S0 is shown by the solid line in FIG. In FIG. 6, the horizontal axis shows the phase difference between the power supply voltage of the commercial power supply and the output voltage of the UPS. That is, the power supply voltage 1
When 01 leads the output voltage 102, it is positive, and when it is late, it is negative. In this way, the phase difference signal S0 is the same as the power source voltage 101 of the commercial power source 1 and the UPS.
When the phase difference between the output voltage 102 and the output voltage 102 is 0, it becomes zero. When the commercial power supply has a phase difference of 90 degrees ahead of UPS, it has a maximum positive value, and when it has a delay of 90 degrees, it has a maximum negative value. It becomes a value. Further, even if the phase difference is 180 degrees, the phase difference signal S0 becomes zero.

FIG. 4 using such a phase difference detection circuit
The operation of the device will be described below. Power supply voltage of commercial power supply 1
When 01 leads the output voltage 102 of UPS2, the phase controller 200 outputs a positive signal as shown in FIG. 6 and is provided to the adder 203 via the amplifier 201. Further, the adder 203 adds the signal output from the reference frequency setting unit 202, and gives a frequency command higher than the reference frequency to the inverse conversion unit 22, so that the output frequency of the inverse conversion unit 22 increases and the power supply voltage of the commercial power supply 1 increases. The phase difference with 101 is reduced.

On the contrary, when the output voltage 102 from the inverse conversion unit 22 is higher than the power supply voltage 101, the phase controller 200 outputs a negative signal, passes through the amplifier 201, and the result is the adder 203. The frequency conversion command lower than the reference frequency becomes
2, the output frequency of the inverse conversion unit 22 is lowered and the phase difference with the power source voltage 101 of the commercial power source 1 is reduced. In this way, by using the phase difference detection circuit of FIG. 5, the phase difference between the voltages of the commercial power supply and UPS can be made zero.

[0012]

However, such a conventional phase difference detection circuit has the following problems. That is, usually, the amplifier 201 of the control unit 20 is provided with a control delay and an integration element, so that the frequency of the inverse conversion unit 22 does not change suddenly. Therefore, UPS
2 Output voltage 102 frequency and commercial power supply 1 power supply voltage 101
If the output frequency of the inverse conversion unit 22 cannot quickly follow the frequency of the commercial power supply because there is a difference in the frequency of the Phase difference of 0 degree to 90 degree and 1
This change is repeated until the output frequency of the inverse conversion unit becomes very close to the commercial power supply frequency after changing to 80 degrees, a delay of 90 degrees, and 0 degrees.

In FIG. 6, the phase difference signal S0 output from the phase difference detecting circuit is from the point A0 to the points A1, A2, A3,
The change with A0 is periodically changed, or the change in the opposite direction is repeated. Therefore, the output of the phase controller 200 alternately repeats the positive output indicating the leading phase and the negative output indicating the lagging phase.
Furthermore, from the state where the commercial power supply frequency is higher than the inverse conversion unit output frequency, the inverse conversion unit output voltage follows the commercial power supply frequency,
FIG. 7 shows the state of each part until the phases match.

In FIG. 7, (a) shows the change in the phase difference between the power supply voltage 101 of the commercial power supply and the output voltage 102 of the UPS, and (b) shows the change of the frequency of the power supply voltage 101 and the output voltage 102. , (C) show changes in the phase difference signal S0. That is, FIG. 7 shows a state in which the frequency of the commercial power supply sharply rises from the state in which the output voltage of the commercial power supply and the output voltage of the UPS match in frequency and phase.

Now, at time T0, when the frequency of the power supply voltage 101 rapidly increases from F1 to F2, immediately after that, as shown in FIG.
As shown in (b), since the frequency of the output voltage 102 is lower than the frequency of the power supply voltage, the voltage phase of the output voltage 102 always shifts in the delay direction. However, as shown in FIG. 7A, if only the difference in relative phase between the two voltages is seen, the output voltage
102 phase is delayed with respect to power supply voltage 101,
The phase difference signal S0 shown in FIG.
Positive and negative are repeated as shown in (c). Therefore, the output frequency of the output voltage 102 changes while repeating rising and falling as shown in FIG. 7 (b).

Therefore, it takes time for output voltage 102 to follow the frequency of power supply voltage 101. Further, it is not preferable that the frequency of the output voltage 102 repeatedly rises and falls from the viewpoint of the responsibility of the UPS that supplies a stable voltage having a stable frequency to the load. Furthermore, UP
When several S are controlled in parallel, the output of the phase controller 200 may change unnecessarily, and the frequency of the inverse converter 22 may move unnecessarily. It becomes a disturbance and is not preferable.

[0017]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and an object of the present invention is when the frequency of the UPS output voltage and the frequency of the commercial power supply voltage are different from each other. The purpose of the present invention is to provide a method capable of promptly following the frequency of a commercial power source by eliminating an unnecessary change in the output of the phase control unit and changing the output frequency of the inverse conversion unit only in the necessary direction of rising or falling. . Specifically, it is determined that there is a difference in frequency between the commercial power supply and UPS when the phase difference passes 180 degrees, and the phase difference is 1
The direction in which the frequency should be controlled is determined by the direction when passing 80 degrees, and it is uniformly controlled only in that direction. The fact that the two frequencies approach each other is also determined by the direction in which the phase difference passes 0 degree. The control is returned to the normal control by the phase difference signal.

In order to achieve such an object, it has a phase difference detection function for detecting the phase difference between the output voltages of two power supplies or power supply devices and outputting it as a phase difference signal. The first function to detect the change in 180 degree advance and the phase difference between the two voltages from 180 degree advance 1
The second function to detect the change of 80 degrees delay and the third function to detect the change of the phase difference of two voltages from 0 degrees delay to 0 degrees advance, and the phase difference of the two voltages It has a discriminating function having four functions, which is a fourth function for detecting a change from 0 degree advance to 0 degree delay, and has a switching function that operates by the outputs of the first to fourth functional units. It has a setting function of increasing and decreasing the frequency.

Then, when the first function operates, thereafter, the signal of the frequency increase command by the setting function is used as the phase control signal for giving the inverse conversion section, and when the third function is operated, the phase difference detection signal is used. Similarly, when the second function operates, the phase control signal is used as a phase control signal that gives a signal of a frequency down command by the setting function to the inverse conversion unit, and the phase difference signal is used when the fourth function operates. It is configured to be a phase control signal.

[0020]

With this configuration, it is determined that there is a difference in frequency between the commercial power supply and the inverse converter when the phase difference passes 180 degrees, and the direction when the phase difference passes 180 degrees Determine the direction in which the frequency should be controlled by fixing the control in the corresponding direction, and determine that the two frequencies are close by the direction in which the phase difference passes 0 degrees.
By releasing the fixed control direction and returning to the control by the phase difference signal, the time required for frequency tracking and phase synchronization can be shortened.

More specifically, when the phase difference passes through the 180 ° state, the phase difference changes from the 180 ° delayed state to the 180 ° advanced state, that is, the output of the phase difference detection circuit is as shown in FIG.
When it passes point A2 in the direction of arrow A21, it is determined that the frequency of the output of the inverse conversion unit is low, and thereafter, the signal for increasing the frequency of the setting function is used as the phase control signal.

After that, when the phase difference passes through the state of 0 degree, the phase difference changes from the state of 0 degree delay to the state of 0 degree advance, that is, the phase difference detection circuit output changes the point A0 in FIG. When passing through the direction, it is determined that the frequency of the output of the inverse conversion unit has sufficiently approached the commercial power supply frequency, and the output of the phase difference detection circuit is used as a phase control signal to return to normal control. In this way, it is possible to detect the difference between the frequencies of the two voltages and the high and low of the frequencies at the same time, determine the direction to be controlled, and eliminate unnecessary control, thereby smoothing the frequency tracking. It is possible to quickly synchronize the. Next, the present invention will be described in more detail by way of examples with reference to the drawings.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a structural example of the main part of a phase control unit according to the present invention. 220 is a phase detection function unit, 230 is a discrimination function unit, 240 is a switching function unit, and 250 is a setting function unit. The phase difference detection function unit 220 outputs two phase difference signals S1 and S2 as a phase difference detection circuit. An example of this is shown in FIG. 2 similar to FIG.

That is, in FIG. 2, a (3 phase / 2 phase) conversion circuit 221 receives the input of the power supply voltage 101 of the commercial power source 1, and a (3 phase / 2 phase) conversion circuit 222 is the inverse conversion unit 22 of the UPS 2. The input of the output voltage 102 is obtained and the signals are output to the arithmetic circuits 223 and 224, respectively. Here, the arithmetic circuits 223 and 224 are obtained by attaching the arithmetic circuit 223 to the apparatus of FIG. 5, and the arithmetic circuit 224 corresponds to the arithmetic circuit 213. . The arithmetic circuit 223 inputs the d-axis component signals V1d and V2d and the q-axis component signals V1q and V2q,
The following equation is calculated and the phase difference signal S1 is output.

(V1d) * (V2d) + (V1q) * (V2q) ... (2)

The characteristic of the phase difference signal S1 is shown by the dotted line in FIG. In this way, the phase difference signal S1 has a positive maximum value when the phase difference between the power supply voltage 101 and the output voltage 102 matches, and becomes zero when the phase difference advances or is delayed by 90 degrees. When the phase difference is 180 degrees, it has the maximum negative value.

The discrimination function unit 230 is a zero level comparator 231, 2
32 and inverter 233, 234 and D flip-flop 235, 236
Consists of. The switching function unit 240 includes AND circuits 241, 242 and contacts 241A, 241B, 242A, which are opened and closed by the AND circuits 241, 242.
It consists of 242B. The setting function unit 250 includes a setter 251 and a positive / negative inverting amplifier 252.

Next, the operation of FIG. 1 will be described. In the discrimination function unit 230, the phase difference signal S output from the phase difference detection function unit 220
The positive and negative judgments of 1 and S0 are made by the zero level comparators 231 and 232. By the zero level comparator 231 and the inverter 233, a signal "0" when the phase difference signal S1 is positive and a signal "1" when the phase difference signal S1 is negative is given to the data inputs of the D flip-flops 235 and 236. The zero level comparator 232 is the phase difference signal S
When 0 is positive, it outputs "1", and when it is negative, it outputs "0" directly to the clock input of the D flip-flop 235, and the output of the zero level comparator 232 is inverted by the inverter 234. Applied to the clock input of D flip-flop 236.

That is, a trigger is given to the D flip-flop 235 when the phase difference signal S0 changes from negative to positive. When the phase difference signal S1 at that time is positive, it is "0", and when it is negative, While outputting "1" to the Q output terminal, this output is held. Similarly, D flip-flop
A trigger is given to the 236 when the phase difference signal S0 changes from positive to negative. When the phase difference signal S1 at that time is positive, "0" is output to the Q output terminal, and "1" is output to the Q output terminal. Holds this output as it is issued.

In the switching function unit 240, the logical product circuits 241, 2
42 outputs "1" when only one Q terminal of the two D flip-flops 235, 236 is set to "1", and closes the contact 241A or the contact 242A, and the contact 2
Open 41B or contact 242B. When the contact 242A is closed and the contact 242B is opened, the phase control signal SS is cut off from the phase difference signal S0 and becomes a constant positive signal by the setter 251, that is, a frequency increase command. This frequency increase command increases the output frequency of the inverse conversion unit 22.

Similarly, when the contact 241A is closed and the contact 241B is opened, the phase control signal SS is cut off from the phase difference signal S0 and a constant negative signal by the setter 251 and the positive / negative inverting amplifier 252, that is, It becomes a frequency down command. This frequency lowering command lowers the output frequency of the inverse conversion unit 22. When both Q terminals of the two D flip-flops 235 and 236 are "1" or "0", the outputs of the AND circuits 241 and 242 are "0", and the contact points 241A and 242A.
Is closed and the contacts 251B and 252B are closed, and the phase control signal SS becomes the phase difference signal S0, which is normal control.

Further, the operation will be described. Now, when there is a difference between the frequency of the power source voltage of the commercial power source and the frequency of the output voltage of the UPS inverse conversion unit, the phase difference changes periodically, and as shown in FIG. 6, the phase difference signal S0 shows the point A0 on the solid line.
From the points A1, A2, A3, A0 or in the opposite direction periodically, the phase difference signal S1 similarly moves on the dotted line.

When the frequency of the power supply voltage 101 is higher than the frequency of the output voltage 102, the phase difference signal S0 changes periodically from the point A0 to the points A1, A2, A3 and A0 in FIG.
The phase difference signal S1 is negative and the D flip-flop 235,
“1” is input to the data input of 236. The phase difference signal S0 changes from positive to negative when passing through the point A2. Therefore, it does not trigger the D flip-flop 235 and does not affect the D flip-flop 235.
Inverter 234 inverts 236 to become an up edge, and outputs a data input signal "1" to the Q terminal and holds it.

The Q terminal of the D flip-flop 236 is "1".
Then, the contact 242A is closed via the AND circuit 242,
The contact 242B is opened, and the phase control signal SS is set by the setter 251.
It becomes the frequency rise command by. Eventually, when the frequency of the inverse conversion unit 22 follows the frequency of the commercial power source and further rises, the phase difference signal S0 changes from the point A0 to A3, A2, A1, A0.

At this time, the output of the phase difference detection circuit is point A0.
The phase difference signal S1 is positive before and after passing through in the direction of arrow A02, and "0" is input to the data inputs of the D flip-flops 235 and 236. Phase difference signal S0 is at point A0
It changes from positive to negative when passing through. Therefore, D
Not a trigger for flip-flop 235,
With respect to the D flip-flop 236, the inverter 234 outputs the data input signal "0" to the Q terminal and holds it. When the Q terminal of the D flip-flop 236 becomes "0", the contact 242A is opened and the contact 242B is closed through the AND circuit 242, the phase control signal SS becomes the phase difference signal S1, and the normal phase control is restarted. It

A brief description of such an operation is as follows. The Q terminal of the D flip-flop 236 is set to "1" when the phase difference signal S0 passes through the point A2 in the direction of arrow A21 in FIG. 6 and is set to "0" when the phase difference signal S0 passes through the point A0 in the direction of arrow A01. Is reset to. The signal of the setting function unit and the phase difference signal are switched according to the signal of the Q terminal to become the phase control signal. Similarly, when the point A2 is passed in the direction of the arrow A22, the Q terminal of the D flip-flop 235 becomes "1", and the contact 241A is closed, so that the phase control signal SS is output by the setter 251 and the positive / negative inverting amplifier 252. It becomes a negative constant value, and the frequency of the inverse conversion unit is lowered. Further, when passing through the point A0 in the direction of the arrow A01, the Q terminal of the D flip-flop 235 becomes "0", the contact 241A is opened, and the contact 241B is closed,
The phase control signal SS becomes the phase difference signal S0, and the normal phase control is restarted.

Next, from the state where the frequency of the power source voltage 101 of the commercial power source 1 is higher than the frequency of the output voltage 102 of the inverse converter 22 of the UPS 2, the frequency of the output voltage 102 follows the frequency of the power source voltage 101, and the phases match. The state of each part up to the above will be described with reference to FIG. 4 similar to FIG. 7. That is, in FIG. 4, the frequency of the power supply voltage 101 changes from F1 to F2 at time T0.
When it rapidly rises to, the phase of the output voltage 102 gradually delays as shown in (a). In FIG. 3, it moves from the point A0 to the point A1 and further toward the point A2.

During this time, the phase difference signal S0 outputs a positive signal to increase the frequency of the output voltage 102 to try to recover the phase difference. However, due to the characteristic of the amplifier 201, the phase difference is delayed at time T1 due to the delay of the frequency tracking. It becomes 180 degrees, and the output of the inverse converter changes from 180 degrees behind to 180 degrees ahead of the commercial power supply. At this time, since the phase difference signal S1 is negative and the phase difference signal S0 changes from positive to negative in FIG.
The Q terminal of the flip-flop 236 becomes "1", and this output goes through the logical product circuit 242 to close the contact 242A and close the contact 242.
Open B. Therefore, a positive signal from the setter 251 appears in the phase control signal SS, and acts to monotonically increase the output frequency of the inverse converter 22 via the amplifier 201 and the adder 203. This state continues until the frequency of the inverse converter follows the frequency of the commercial power source. Meanwhile, in FIG. 6, points A0, A1,
It changes periodically in the directions of A2, A3 and A0.

When the frequency of the inverse converter and the commercial power supply becomes the same at time T2, the change in the phase difference between the inverse converter and the commercial power supply temporarily stops, but the frequency of the inverse converter continues to rise. , The phase difference changes in the opposite direction. In FIG. 6, the change is in the direction of points A0, A3, A2, A1 and A0. In FIG. 4, the frequency of the inverse converter coincides with the commercial power source at the point PA on the way from the point A0 to the point A1 in FIG.
It shows a case where the direction of the operating point is reversed and heads again to the point A0.

Further, at time T3, the operating point passes the point A0. At this time, the phase difference signal S1 is positive and the phase difference signal S0 changes from positive to negative.
The Q terminal of 236 changes from "1" to "0", and this signal opens the contact 242A through the AND circuit 242 and opens the contact 242B.
Make a circuit. Therefore, the phase difference signal S0 appears in the phase control signal SS, and the inverse converter 22 returns to the normal control by the phase difference signal via the amplifier 201 and the adder 203 to reduce the phase difference by the phase difference signal. Controlled.

Eventually, at time T4, the output voltage of the inverse converter coincides with the commercial power supply in both frequency and phase. In this way, as shown in FIG. 4, during the period from time T1 to time T2, the frequency of the inverse conversion unit is controlled in the direction of monotonically increasing without repeating rising and falling, thereby promptly. And without giving disturbance to the control for parallel,
It can be brought close to the frequency of commercial power.

[0042]

As described above, according to the present invention, U
When there is a difference between the frequency of the PS output voltage and the frequency of the commercial power supply voltage, the output frequency of the UPS inverse conversion unit can be changed only in the direction in which it needs to be increased or decreased, and the frequency of the commercial power supply can be quickly tracked. It is possible to provide a special method for realizing the device.

[Brief description of drawings]

FIG. 1 is a system diagram showing a configuration example of a main part of a phase control unit according to the present invention.

FIG. 2 is a block diagram showing an example of a phase difference detection circuit according to the present invention.

FIG. 3 is a diagram showing operation waveforms of respective parts in the embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration of a commercial synchronous UPS power supply system.

FIG. 5 is a block diagram showing a conventional example of a phase difference detection circuit.

FIG. 6 is a waveform diagram showing a phase difference between a commercial power supply voltage and a UPS output voltage.

FIG. 7 is a diagram showing operation waveforms of various parts in the conventional example.

[Explanation of symbols]

 1 Commercial power supply 2 Uninterruptible power supply (UPS) 20 Control unit 21 Forward conversion unit 22 Inverse conversion unit 200 Phase control unit 201 Amplifier 202 Reference frequency setting device 203 Adder 3 Load device 4 Switch 5 Switch 221 Conversion circuit 212 Conversion Circuit 213 Operation circuit S0 Phase difference signal S1 Phase difference signal SS Phase control signal 220 Phase detection function section 230 Discrimination function section 240 Switching function section 250 Setting function section 221 Conversion circuit 222 Conversion circuit 223 Operation circuit 224 Operation circuit

Claims (1)

[Claims] 1. An uninterruptible power supply device having a function of detecting a phase difference between output voltages of two power supplies, and operating so as to synchronize by controlling an output frequency of one of the two power supplies, The phase difference detection function section has a discrimination function of detecting that the output has passed 180 degrees and 0 degrees and the passing direction, and has a setting function of generating a signal for raising or lowering the frequency of one power supply output. It has a switching function for selecting between the output of the phase difference detection function unit and the output of the setting function unit according to the output of the discrimination function unit, and when the output of the phase difference detection function unit has passed 180 degrees, it depends on the passing direction of the output. Select one of the setting outputs to control the output frequency of one power supply,
A synchronous control method for an uninterruptible power supply, characterized in that when 0 degrees is passed, the phase difference detection function unit returns to control according to the passing direction.