JP2646845B2 - Automatic synchronous feeding device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial applications]

The present invention relates to a circuit breaker interconnecting different power supply systems,
The present invention relates to an automatic synchronous closing device that closes a circuit breaker when the voltage phases of power supplies on both sides of the circuit breaker match. In the drawings, the same reference numerals indicate the same or corresponding parts.

[Prior art]

FIG. 3 shows a general system diagram in which the generator 1 and the electric power system 3 are interconnected through the circuit breaker 2. Here, reference numerals 4 and 5 denote transformers (PT) for detecting voltages on the generator 1 side and the electric power system 3 side, respectively, with the circuit breaker 2 interposed therebetween, and 6 denote detection voltages VG and VL of the transformers 4 and 5 respectively. Is input to perform automatic synchronization of the circuit breaker 2. Next, the operation principle of the automatic synchronization input device 6 will be described.
FIG. 4 shows an in-phase difference voltage waveform (beat voltage waveform) VGL between the transformer 4 and the transformer 5. That is, the secondary voltage VG of the transformer 4 is VG = E ₁ sinω ₁ t (1) The secondary voltage VL of the transformer 5 is VL = E ₂ sinω ₂ t (2) Therefore, if E ₁ = E ₂ = 1.0 (3), the beat voltage waveform VGL is Becomes In order to close the circuit breaker 2 at the point in FIG. 4, that is, at the point where the voltages VG and VL coincide with each other, the automatic synchronous closing device 6 is turned on at the time Δt seconds before the closing time of the circuit breaker 2 (that is, the time required for closing). It outputs a closing command. For this reason, conventionally, in order to calculate the phase coincidence point and the point before the closing time Δt seconds of the circuit breaker 2 based on the equation (4), a sum operation and a difference operation are performed by the secondary circuits of the auxiliary transformers 4 and 5, Furthermore, a rectifier circuit to remove the cos term, which is almost the rated frequency,
Many filter circuits and differentiating circuits for judgment were used.

[Problems to be solved by the invention]

In the conventional automatic synchronizing device, a large number of terminals are required for the secondary circuits of the auxiliary transformers 4 and 5 as described above, and it is necessary to compensate for the phase delay caused by an analog filter to remove the rated frequency component. was there. When a digital operation type automatic synchronization input device is used,
Use a high-speed calculator with a calculation cycle of several milliseconds, or
It was necessary to separately install a rectifier circuit, filter circuit, etc. to eliminate the s term. Therefore, the present invention limits the purpose of the auxiliary transformer to insulation and operation level matching, eliminates filters, differentiating circuits, and the like, improves the size and performance of the device, and has an operation cycle of about ten to several tens msec. It is an object of the present invention to provide an automatic synchronization input device that can perform calculations even with a digital calculator.

Means for Solving the Problems In order to solve the above-mentioned problems, an automatic synchronization input device according to claim 1) is configured such that “the two power supply systems (such as the generator 1 and the power system 3) are disconnected. When the voltage difference and the frequency difference between the two linked power supply systems (hereinafter referred to as both-side power supply) are equal to or less than a predetermined value and the voltage phases of the two-sided power supply coincide with each other, An automatic synchronous closing device (6, etc.) for outputting a closing command to close a circuit breaker, and calculates at least a sum of squares (EGL, etc.) of the in-phase difference voltage of each of the three-phase voltages of the power supplies on both sides. Thus, the sum frequency of the two power supplies / 2 (that is, (ω ₁ + ω ₂ ))
/ 2) component and the difference frequency / 2 (that is, (ω ₁ −ω ₂ ) / 2) component, only the component corresponding to the difference frequency / 2 in the common-mode difference voltage waveform of both power supplies And outputs a closing command for the circuit breaker based on this component. "In the automatic synchronous closing device according to claim 2), the automatic synchronous closing device according to claim 2).
The automatic phase dosing device, the "correction of the voltage difference between the square values between the two side power sum of squares as required of the in-phase difference voltage (i.e. ^{_{3 (E 1 -E 2) 2}} /2) is subjected to ].

[Operation]

As means for removing the cos term (approximately the rated frequency component) in the equation (4), the sum of squares of the in-phase difference voltage of each of the three-phase voltages of the power supplies on both sides of the circuit breaker is calculated. Now, each phase voltage of the secondary voltage VG of the transformer 4 is The secondary voltage VL of the transformer 5 And then, when calculating the square sum E _GL for each phase of the three-phase of the same phase difference voltage Becomes Here, since the voltage E ₁ and E ₂ can be detected in a known manner, it can be understood that only possible to calculate the sin term in easily (difference frequency / 2) component by calculating the E _GL. Second
The figure shows the waveform of the sin term obtained from equation (7) and the sin term of equation (4).

【Example】

FIG. 1 is a block circuit diagram showing a main part configuration as one embodiment of the present invention. In the figure, reference numeral 11 denotes a secondary-side three-phase voltage VGu, VGv,
VGw is input, and in this case, a voltage frequency detection circuit for detecting the voltage E _{1 of the} power source on the generator 1 side and the frequency ω ₁ , and 12 inputs the secondary three-phase voltages VLu, VLv, VLw of the transformer 5. In this case, it is a voltage frequency detection circuit for detecting the voltage E ₂ and the frequency ω ₂ of the power supply on the power system 3 side. In this case, the detection method of the power supply voltage E _L, for example in the case of an analog system, the transformer 4 secondary 3-phase voltage VGU, VGV,
A method of detecting a three-phase full-wave rectified voltage of VGw is used. In the case of a digital method, a method of calculating the average of the sum of squares of the three-phase voltages on the secondary side is used as shown below. The detected as in the case of the power supply voltage E ₁ also supply voltage E _2. Returning again to FIG. 1, 13 is a subtractor for calculating the difference (common-mode difference voltage) between the power supplies VGu and VLu, 14 is a subtractor for calculating (common-mode difference voltage) between the voltages VGv and VLv, and 15 is a voltage VGw and VLw. Subtracter for calculating the difference (in-phase difference voltage) from the sum, 16 is a multiplier for obtaining the square of the addition result of the adder 13, 17 is a multiplier for obtaining the square of the addition result of the adder 14, and 18 is the addition of the adder 15. A multiplier for calculating the square of the result, 19 is an adder for calculating the sum of outputs of the multipliers 16, 17, and 18,
Reference numeral 20 denotes a voltage correction calculator for correcting the addition results of the adder 19 to the detection voltages E ₁ and E ₂ of the voltage frequency detection circuits 11 and 12 to obtain Ex described later, and reference numeral 21 denotes a detection frequency of the voltage frequency detection circuits 11 and 12. ω ₁ , ω ₂ and circuit breaker closing time Δt are input and
Is a frequency-correction computing unit that calculates Ex and Ez, and is a closing permission determiner that inputs Ex and Ez and outputs a breaker closing command 22a. With such a configuration. Generator phase voltage VGu VGv VG
Using w and the bus voltage VLu VLv VLw of the power system 3 as input signals, subtracters 13, 14, and 15 calculate the common-mode difference voltages of the three phases U, V, and W, respectively. Then, the multipliers 16, 17, and 18 each perform a square operation of the difference voltage of each of the three phases, and the adder 19 calculates _EGL of the above equation (7). Voltage correction arithmetic unit 20 uses the voltages E ₁ and E ₂ detected in a known manner as described above by the voltage frequency detecting circuits 11 and 12 (7) of the first term on the right side 3 (E ₁ -E ₂ ) ^2/2 determined, right low frequency component value of the second term of subtracted from E _GL entering this value (7)
Ex (formula (8)) is calculated, and | E ₁ −E ₂ | is determined to be equal to or less than a predetermined value. The frequency correction calculator 21 calculates the low frequency component value at the time of t = −Δt from the frequencies ω ₁ and ω ₂ detected by the voltage frequency detection circuits 11 and 12 by a known method and the closing time Δt of the circuit breaker.
Ez (formula (9) below) is calculated, and | ω ₁ −ω ₂ | is determined to be equal to or less than a certain value. The closing permission determiner 22 issues a breaker closing command when | E ₁ −E ₂ | and | ω ₁ −ω ₂ | are both equal to or less than a predetermined value and the Ex value reaches Ex ≦ Ez in the low range. Is output.

【The invention's effect】

According to the present invention, for the circuit breaker 2 that interconnects two different power supply systems (such as the generator 1 and the power system 3), the two interconnected power supply systems (hereinafter referred to as both-side power supply) are provided.
An automatic synchronous closing device 6 that outputs a closing command to close the circuit breaker 2 when the voltage difference and the frequency difference are equal to or less than a predetermined value and the voltage phases of the power supplies on both sides match. Calculates the sum of squares EGL of the in-phase difference voltage of each phase of the three-phase voltage of the power supply, and further calculates the sum of squares EGL
By performing correction of the square value of the voltage difference between the two side power supply (i.e. ^{_{3 (E 1 -E 2) 2}} /2) if necessary, the sum of both side power supply frequency / 2 (i.e. (omega _{1 +} omega ₂ ) / 2) component and the difference frequency / 2 (that is, (ω ₁ −ω ₂ ) / 2) component multiplied by the difference frequency in the in-phase difference voltage waveform of both power supplies
Since only the component corresponding to / 2 is calculated and the closing command of the circuit breaker is output based on this component, a filter or the like for removing almost the rated frequency component of the beat voltage is not required, which is simple. The circuit can provide an automatic synchronization input device. In addition, by applying an analog input card with a simultaneous sample and hold function, the function can be satisfied with a digital arithmetic unit having an arithmetic cycle of about ten to several tens msec without installing an external filter or the like.

[Brief description of the drawings]

FIG. 1 is a block circuit diagram showing a main part configuration as one embodiment of the present invention, FIG. 2 is a comparison diagram of a low frequency component waveform of an in-phase difference voltage (beat voltage) and a detected waveform according to the present invention, The figure shows a configuration example of a power plant system including an automatic synchronization input device. FIG. 4 is a diagram showing the common-mode difference voltage (beat voltage) waveform on both sides of the circuit breaker. 1: Generator, 2: Circuit breaker, 3: Power system, 4,5: Transformer, 6: Automatic synchronization input device, 11, 12: Voltage frequency detection circuit, 13-15: Subtractor, 16-18: Multiplication , 19: adder, 20: voltage correction calculator, 21: frequency correction calculator, 22: closing permission determiner, 22a: closing command, Δt: breaker closing time.

Claims (2)

(57) [Claims] 1. A circuit breaker interconnecting two different power supply systems, wherein a voltage difference and a frequency difference between the two power supply systems (hereinafter referred to as both-side power supply) are not more than a predetermined value, and An automatic synchronous closing device that outputs a closing command to close the circuit breaker when the voltage phases of the power supplies on both sides match, wherein at least the sum of squares of the in-phase difference voltage of each of the three-phase voltages of the power supplies on both sides. By calculating only the component corresponding to the difference frequency / 2 of the in-phase difference voltage waveform of the both-side power supply expressed by multiplying the sum frequency / 2 component of the both-side power supply and the difference frequency / 2 component. An automatic synchronous closing device which calculates and outputs a closing command of the circuit breaker based on this component. 2. The automatic synchronizing device according to claim 1, wherein the sum of squares of the in-phase difference voltage is corrected, if necessary, by the square value of the voltage difference between the power supplies on both sides. Automatic synchronization input device.