KR19990039375A - Operation Control Method of Power Switching Machine and Its Circuit Structure - Google Patents

Abstract

The present invention relates to an operation control method capable of performing an optimal switching operation by preventing arcing during power switching in an AC power supply switching between A power supply and B power supply, and a circuit structure for performing the method.

The present invention provides a method for controlling an operation of a power changer for switching from one power source to another, the method comprising: detecting a time when a phase instantaneous value from one power source reaches a specific value; Detecting a time when a phase instantaneous value from another power supply reaches a specific value; And, comprising the step of determining the time interval in the two steps, by providing a control method of the operation of the power switch, characterized in that the power supply switching is performed so that the phase difference between the two power supplies within a predetermined range, The phase difference between the two power supplies can be detected by measuring the time interval between zero cross points (zero voltage points) of the two power supplies, which simplifies the circuit configuration of the phase difference detection unit, thereby reducing the cost of the product and operating reliability. To provide a technical effect to improve.

In addition, the power switching method according to the present invention can be applied to an uninterruptible switch between AC power supplies while providing a technical effect of preventing damage to the switch and damage to the associated circuit elements by arcing at the contact portion of the power switch. .

Description

Operation Control Method of Power Switching Machine and Its Circuit Structure

The present invention relates to a control method of a power switching operation capable of performing an optimal switching operation by preventing arcing during power switching in AC power switching of A power supply and B power supply, and a circuit structure for performing the method. will be.

Switching of power means changing the power source supplied to the electrical equipment. For example, when the main power is supplied while the main power is supplied, the power supply is switched to start the self-generating equipment and to receive power from the main power supply.

In this case, there may be a method of operating a separate power generation facility, or there may be a method of using other power source that is always waiting to configure a separate transmission line.

In such a power supply switching device, the reliability, speed and stability of its operation are required.

That is, the power switching device and its system should be able to supply the spare power quickly in case of emergency, and should reduce the surge voltage caused by the arc generation when switching the power as much as possible. Should be guaranteed.

On the other hand, the voltage of an AC power supply changes with time. In the case of an AC power supply having a frequency of 60 Hz, the change of the voltage value changes at a rate of 60 changes in one second period.

According to the characteristics of these AC power sources, when switching them from one AC power supply source to another, the phase change of both power sources and voltages other than the frequency should be considered.

However, the power supply switching device of the prior art merely detects the power failure of the main power supply and automatically performs an operation of switching to the standby power supply, and does not adopt a switching method in consideration of the phase change of both power supplies.

Therefore, when a conventional power supply switching device is used for power supply switching between AC power sources, there is a problem that arcing occurs at the switching contact of the power supply switching machine due to the phase superposition of both power sources.

By this arcing, an instantaneous voltage waveform of more than twice the normal power supply voltage can be applied to the circuit, resulting in the voltage being applied beyond the breakdown voltage of the circuit device, resulting in a breakdown of the power switch or deterioration of the related circuit device. It can also cause damage.

The present invention has been made to solve the above problems of the conventional power switching device, and an object of the present invention is to provide a method for controlling the operation of a power switch that can switch the power source by detecting the phase of both power sources and comparing them. do.

In addition, another object of the present invention is to provide a control circuit structure of a power switch which can perform power switching by applying the operation control method.

1 is a circuit diagram showing an example of a circuit configuration of a power supply switching control unit according to the present invention.

2 is a flowchart illustrating the operation of the power switching control unit according to the present invention.

* Explanation of symbols for main parts of the drawings

D1, D2: Rectifier diodes R1, R2, R3, R4: Voltage distribution resistors

ST1, ST2: Operational Amplifier

According to the present invention for achieving the above object, in the operation control of the power changer for switching from one power source to another power source, detecting the phase instantaneous value from one power source reaches a specific value; ; Detecting that a phase instantaneous value from another power supply reaches a specific value; And, comprising the step of determining the time interval of the instant of the detection of the two steps, to provide a control method for the operation of the power switch characterized in that the power supply switching is performed so that the phase difference between the two power supplies within a predetermined range. do.

In another aspect, the present invention, the first Schmitt trigger means for detecting a phase change of a power supply; Second Schmitt trigger means for detecting a phase change of another power supply; And microprocessor means for receiving the phase signals from the two Schmitt trigger means, and outputting a power switching control signal so that power is switched within a predetermined range between the two power supply sources. Provides a control circuit structure of a power switch.

Hereinafter, with reference to the accompanying drawings will be described the technical operation and effects according to the present invention.

First, an embodiment of a control circuit structure of a power switch according to the present invention will be described in detail with reference to FIG. 1.

The control circuit according to the invention senses the power phases from one power supply source (hereinafter referred to as the main power source) and the other power supply source (hereinafter referred to as the reserve power source), respectively.

The circuit divides the diode (D1) for rectifying the AC voltage input from the main power supply, the diode (D2) for rectifying the AC voltage input from the spare power supply, and divides the rectified DC voltage to the positive terminal (+) of the operational amplifier. Voltage divider resistors R1, R2, R3, R4 for input, voltage divider resistor R13 for inputting a reference voltage signal to the negative terminal (-) of the operational amplifier, and operational amplifier ST1 having a Schmitt trigger characteristic. , ST2).

The negative terminal (-) of the Schmitt trigger operational amplifiers ST1 and ST2 receives a reference voltage in common through the voltage distribution resistor R13. Therefore, under the common reference voltage, each of the operational amplifiers ST1 and ST2 operates in accordance with the voltage value of the main power supply or the voltage value of the spare power supply input through the positive terminal (+).

The pulsating voltage rectified from the main power supply is input to the positive terminal (+) of the operational amplifier ST1. The voltage waveform at this time is a half-wave rectified wave. The changing pulse current is input to the operational amplifier ST1 via the voltage distribution resistors R1 and R2. At this time, a constant reference value obtained by dividing the operating power source Vcc is input to the negative terminal (−) of the operational amplifier ST1. Therefore, as soon as the voltage value of the positive terminal rises above the voltage value of the negative terminal and exceeds the reference value, the operational amplifier ST1 is operated to input a HIGH output to the microprocessor (not shown). In addition, as soon as the voltage value of the positive terminal becomes smaller than the reference value, a low output is input to the microprocessor.

On the other hand, to the positive terminal (+) of the operational amplifier (ST2), the pulse current voltage rectified from the spare power supply is input. The rectified waveform at this time is a half-wave rectified wave. The DC voltage thus changed is input to the operational amplifier ST2 via the voltage distribution resistors R3 and R4. At this time, a constant reference value obtained by dividing the operating power is input to the negative terminal (-) of the operational amplifier ST2. Therefore, as soon as the voltage value of the positive terminal rises above the voltage value of the negative terminal and exceeds the reference value, the operational amplifier ST2 is operated to input a HIGH output to the microprocessor. In addition, as soon as the voltage value of the positive terminal becomes smaller than the reference value, a low output is input to the microprocessor.

Therefore, when the frequency of the input power is 60 Hz, the phase signal of the main power is input to the microprocessor at a frequency of 1/60 seconds or 16.67 ms, and when the frequency is 50 Hz, the frequency is 1/50 seconds or 20 ms. The phase signal of the main power supply is input. Similarly, at a frequency of 60 Hz, the phase signal of the backup power supply is input to the microprocessor as a high frequency at 1/60 seconds or 16.67 ms, and the phase signal of the backup power supply is input at a frequency of 1/50 seconds or 20 ms at a frequency of 50 Hz. do.

The microprocessor determines the synchronization of the two power sources by measuring the time difference between the two phase signal inputs. For example, if the phase signal is inputted from the preliminary power supply after 16.67 / 2ms, that is, 8.335ms after the phase signal from the main power supply, it can be determined that both power supplies have a phase difference of 180 degrees. Therefore, the microprocessor determines that both phases are closer as the phase signal distance from both power inputs approaches zero, and that the phases are opposite when the phase signal intervals from both power inputs approach 8.335 ms. It can be determined that the phase of.

On the other hand, the main power source is usually supplied by the Korea Electric Power side, the frequency is relatively stable, but when the reserve power is supplied from the self-generating facilities, the frequency fluctuates widely. Thus, for example, if the frequency of the main power supply is fixed at 60 Hz and the frequency of the spare power supply is 50 Hz, the synchronous and asynchronous phases are repeated at a period of 20 / 16.67 = 1.2 seconds. That is, the zero cross point (zero voltage point) coincides every 1.2 seconds. The period of the zero-cross is shorter as the frequency difference between both power supplies is shorter, and the longer as the frequency difference between both power sources is smaller.

Therefore, in performing the switching between the main power supply and the reserve power supply, if the power supply switching is performed at the same time when the phases of both power supplies are synchronized, the occurrence of arcing between both ends of the contact point of the switching device can be reduced.

2 is a flowchart illustrating the operation of the operation control method according to the present invention.

This flow chart is for the phase comparison control program subroutine in the microprocessor.

As described above, the microprocessor receives the phase signal of the A power source through the operational amplifier ST1 (step S102). After that, the input of the phase signal of the B power supply is awaited. For this purpose, if there is a phase signal input of the A power supply, the timing counting means (not shown) can be reset to continue counting until there is a phase signal input from the B power supply.

The phase signal is input from the B power supply via the operational amplifier ST2 (step S104). At this time, the counting of the counting means is stopped and the count value, i.e., the time difference between the two inputs can be calculated.

Thereafter, a phase difference comparison step S106 of comparing the time difference between both signals with a predetermined setting range X is performed. Herein, the setting range may be set by the user. For example, if the range of the phase difference is set to 10%, the comparison result is output as an example (Y) when both signals are input within a time interval of 1.67 ms (16.67 / 100 x 10).

On the other hand, if the comparison result in the comparison step (S106) is NO (N), the flow returns to the phase signal input step (S102) of the A power supply and circulates in this cycle.

If the comparison result in the comparison step S106 is YES, the transfer control signal is output (S108). Therefore, the power switching means may be operated to switch power between the A power source and the B power source.

As described above, the phase comparison method according to the present invention can detect the phase difference between the two power supplies by measuring the time interval between zero cross points (zero voltage points) of the two power supplies, thereby simplifying the circuit configuration of the phase difference detection unit. Therefore, the cost of the product can be reduced, and the technical effect of improving the operation reliability is achieved.

In addition, the power switching control circuit of the present invention detects the difference between the phases of the two power supply when switching the power supply, so that the switching operation can be performed at the optimal switching time, the switching of the switch by arcing at the contact portion of the power switch It prevents damage and damage to related circuit elements to achieve the technical effect of extending the life of the product and preventing failure.

In addition, the power switching method according to the present invention can be applied to an uninterruptible power switch between AC power.

While the invention has been shown and described with respect to particular preferred embodiments, it is possible to make various modifications and variations within the spirit or principles of the invention provided by the following claims, wherein the spirit or principles of the invention are power conversion It will be apparent to those skilled in the art that the system can be implemented in various forms.

Claims (2)

In controlling the operation of a power switch, which switches from one power supply source to another power supply source, Detecting that a phase instantaneous value from one power supply reaches a specific value; Detecting a shade when a phase instantaneous value from another power supply reaches a specific value; And, And determining the time interval between the sensing moments of both steps, A method of controlling an operation of a power switch, characterized in that the power supply is switched so that the phase difference between the two power supplies is within a predetermined range. First Schmitt trigger means for detecting a phase change of a power supply; Second Schmitt trigger means for detecting a phase change of another power supply; And, A microprocessor means for receiving a phase signal from the two Schmitt trigger means, A control circuit structure of a power changer, characterized by outputting a power transfer control signal so that power transfer is performed within a predetermined range between two power supply sources.