KR20200132032A - Apparatus for detecting nonlinear oscillation in power network and method thereof - Google Patents

Abstract

The present invention discloses a nonlinear vibration detection device in a power network and a method thereof. The nonlinear vibration detection device in a power network of the present invention comprises: a power measuring unit measuring a power value in a bus of the power network; a control unit receiving measurement information measured from the power measuring unit to calculate the rate of change for the measurement information, using the measurement information and the rate of change to form a coordinate plane, and then calculating a distance between a stationary state in the coordinate plane and a measurement point based on the slope on the coordinate plane to determine the risk of differential resonance based on the distance; and a display unit outputting the calculation result and the determination result of the control unit.

Description

Nonlinear vibration detection device in power grid and its method {APPARATUS FOR DETECTING NONLINEAR OSCILLATION IN POWER NETWORK AND METHOD THEREOF}

The present invention relates to an apparatus and method for detecting nonlinear vibrations in a power grid, and more particularly, to a maximum for a distance value on a two-dimensional coordinate plane based on time series information and rate of change of voltage and current of effective values acquired in the power grid. The present invention relates to an apparatus for detecting nonlinear vibrations in a power grid and a method for determining the risk of differential resonance by calculating a Lyapunov index.

In general, KEPCO receives extra-high voltage power from KEPCO and converts and uses it into high-voltage and low-voltage power required by customers as the demand for power increases due to the increase in power consumption caused by the increase in power consumption in industrial sites and the increase in information equipment used by customers. For this purpose, the installation of switchgear, which is a basic electrical facility, is increasing, and according to the size, purpose, and location of the voltage used, it is divided into a high-voltage switchboard, a low-voltage switchboard, an electric motor control panel, and a distribution panel.

However, in the past, it is a reality that various types of equipment accidents such as equipment burnout, short circuit, ground fault, etc. have occurred due to the increase in installation and capacity increase of power equipment regardless of the voltage level such as extra high voltage, high voltage, and low voltage. Inside the closed structure, overload, thermal deterioration due to temperature rise of power devices, electrical deterioration due to electric field concentration, mechanical deterioration due to mechanical stress, insulation defect due to passage of time or environmental deterioration depending on location, overload, vibration/ Equipment accidents occur due to shocks, etc., and spread to power outages and fire accidents.

Meanwhile, the existing power grid consists of generators, transmission lines, substations, distribution lines, and customers, and the recent Korean power grid uses eco-friendly energy such as solar or wind energy to prepare for energy depletion and environmental pollution. The introduction of facilities is planned.

Since such eco-friendly energy has high volatility and uncertainty, if various failures occur in the power grid, the physical quantity (value) measured in each substation or power plant of the power grid may appear in the form of including vibrations, which can be found throughout the power grid. It can have a serious impact.

The background technology of the present invention is disclosed in Korean Registered Patent Publication No. 1865086 (announced on May 31, 2018, a fault monitoring and diagnostic device built-in switchgear having an accident data analysis and an internal abnormal condition monitoring and diagnosis function).

As such, the nonlinear vibration phenomenon that may occur due to the occurrence of an event in the power grid is characterized by being continuously maintained or gradually increasing, and such a vibration phenomenon can be observed from a low frequency vibration of 0.1 Hz to 2.0 Hz to a differential vibration of 15 Hz to 50 Hz. I can.

Here, the vibration phenomenon is difficult to secure the required time for the operator of the power grid to check it and take appropriate measures because the propagation speed of the vibration phenomenon is very fast in the power grid.

In particular, the conventional differential resonance detection method uses a band-pass filter for the differential resonance frequency domain to be detected, but this method requires a large amount of data to be accumulated so that the filter can be operated. There is a problem in that it takes a lot of time to detect the vibration phenomenon caused by resonance.

The present invention was conceived to improve the above problems, and an object of the present invention according to one aspect is a distance value on a two-dimensional coordinate plane based on time series information and rate of change of the effective voltage and current obtained in the power grid. Nonlinear vibration in the power grid that determines the risk of differential resonance in real time by calculating the maximum Lyapunov index for and using this to detect in real time a nonlinear vibration phenomenon caused by interference between components in the power grid. It is to provide a detection device and a method thereof.

An apparatus for detecting nonlinear vibrations in a power grid according to an aspect of the present invention includes: a power measuring unit for measuring a power value in a bus of the power grid; After receiving the measured information measured from the power measuring unit, calculating the rate of change for the measured information, forming a coordinate plane using the measured information and the rate of change, and then forming a coordinate plane between the normal state in the coordinate plane and the measurement point A control unit that calculates a distance and determines a risk of differential resonance based on the distance; And a display unit that outputs the calculation result and the determination result of the control unit.

In the present invention, the power measurement unit includes: a voltage measurement unit that measures a voltage in a bus; A current measuring unit measuring a current in the bus; And a phase angle measurement unit that measures a phase angle in the bus.

In the present invention, the control unit includes: a rate of change calculator configured to calculate a rate of change in time series for measurement information input from the power measurement unit; A distance calculator configured to form a two-dimensional coordinate plane based on the measurement information and the rate of change calculated by the rate of change calculator, and then calculate the distance between the stationary state and the measurement point based on the slope on one side of the coordinate; And a risk determination unit for determining the risk of differential resonance by calculating a maximum Liafnov index based on the distance calculated by the distance calculation unit.

In the present invention, the rate of change calculation unit is characterized in that it calculates the rate of change of the measurement information in real time through a delay device.

In the present invention, the two-dimensional coordinate plane is characterized in that it is a Poincare plane.

In the present invention, the distance calculator calculates a distance between a normal state and a measurement point by selecting a value in which a slope on the coordinate plane is within a set range.

In the present invention, the risk determination unit is characterized in that when the maximum Liafnov index is positive, it determines the risk of differential resonance.

A method for detecting nonlinear vibration in a power grid according to an aspect of the present invention includes the steps of: receiving, by a control unit, measurement information measured at a bus of the power grid from a power measuring unit; Calculating, by the controller, a rate of change of the input measurement information; Forming a coordinate plane by using the measurement information and a rate of change, and calculating a distance between a steady state in the coordinate plane and a measurement point based on a slope on the coordinate plane; And determining, by the controller, the risk of differential resonance resonance based on the distance.

In the present invention, the step of receiving the measurement information is characterized in that the control unit receives the voltage, current and phase angle measured by the bus.

In the present invention, the step of calculating the rate of change is characterized in that the control unit calculates the rate of change of the measurement information in real time through a delay device.

In the present invention, the step of calculating the distance is characterized in that the control unit forms a two-dimensional coordinate plane based on the measurement information and the rate of change, and then calculates the distance between the stationary state and the measurement point based on the slope on one side of the coordinate.

In the present invention, the two-dimensional coordinate plane is characterized in that it is a Poincare plane.

In the present invention, the step of calculating the distance is characterized in that the control unit calculates the distance between the normal state and the measurement point by selecting a value in which the slope on the coordinate plane is within a set range.

In the present invention, the step of determining the risk of differential resonance is characterized in that the control unit calculates the maximum Liafnov index based on the distance, and then determines the risk of differential resonance when the maximum Liafnov index is positive.

The apparatus and method for detecting nonlinear vibration in a power grid according to an aspect of the present invention are based on time series information and rate of change of voltage and current of effective values acquired in the power grid, based on the maximum Liapunov for a distance value on a two-dimensional coordinate plane. By calculating the (Lyapunov) index and using it to detect nonlinear vibration phenomena caused by interference between components in the power grid in real time, it is possible to determine the danger of differential resonance in real time, thereby improving the stability and reliability of the power grid. have.

In addition, according to the present invention, it is possible to more quickly detect a vibration phenomenon caused by mutual interference between different inverter-based power facilities in a smart grid environment to check the risk.

1 is a block diagram showing a nonlinear vibration detection apparatus in a power grid according to an embodiment of the present invention.
2 is a diagram showing a plane of Poincaré used in a nonlinear vibration detection apparatus in a power grid according to an embodiment of the present invention.
3 is a view for explaining the calculation process of the plane distance in the nonlinear vibration detection apparatus in the power grid according to an embodiment of the present invention.
4 is a flowchart illustrating a method of detecting nonlinear vibration in a power grid according to an embodiment of the present invention.

Hereinafter, an apparatus and method for detecting nonlinear vibration in a power grid according to the present invention will be described with reference to the accompanying drawings. In this process, the thickness of the lines or the size of components shown in the drawings may be exaggerated for clarity and convenience of description. In addition, terms to be described later are terms defined in consideration of functions in the present invention and may vary according to the intention or custom of users or operators. Therefore, definitions of these terms should be made based on the contents throughout the present specification.

1 is a block diagram showing a non-linear vibration detection device in a power grid according to an embodiment of the present invention, Figure 2 is a Poincare plane used in the nonlinear vibration detection device in the power grid according to an embodiment of the present invention 3 is a view for explaining the calculation process of the plane distance in the nonlinear vibration detection apparatus in the power grid according to an embodiment of the present invention.

As shown in FIG. 1, a nonlinear vibration detection apparatus in a power grid according to an embodiment of the present invention may include a power measurement unit 10, a control unit 20, and a display unit 30.

The power measurement unit 10 may measure a power value at a bus of the power grid and provide measurement information to the control unit 20.

Here, the power measurement unit 10 includes a voltage measurement unit 12 for measuring a voltage at the bus, a current measurement unit 14 for measuring a current at the bus, and a phase angle measurement unit 16 for measuring a phase angle at the bus Including, it is possible to provide the control unit 20 with measurement information obtained by measuring the effective voltage, current, and phase angle in the bus bar of the power plant or substation.

The controller 20 receives measurement information measured from the power measurement unit 10, calculates a rate of change of the measurement information, forms a coordinate plane using the measurement information and the rate of change, and then forms a coordinate plane based on the slope on the coordinate plane. The distance between the stationary state and the measurement point at is calculated, and the risk of differential resonance can be determined based on the distance.

Here, the control unit 20 may include a rate of change calculation unit 22, a distance calculation unit 24, and a risk determination unit 26.

The rate of change calculator 22 may calculate the rate of change in time series with respect to the measurement information input from the power measurement unit 10.

Here, the rate of change calculation unit 22 may calculate a rate of change of the measurement information in real time through a delay device.

The distance calculation unit 24 may calculate a distance between the normal state and the measurement point based on the inclination on one side of the coordinates after forming a two-dimensional coordinate plane based on the measurement information and the rate of change calculated by the rate of change calculation unit 22.

Here, the two-dimensional coordinate plane is a Poincare plane, and the distance calculator 24 may calculate a distance between the normal state and the measurement point by selecting a value in which the slope on the coordinate plane is within a set range.

The power produced from the three-phase generator structure in the power grid is transferred to the three-phase transmission network, and the instantaneous value of each phase has a constant waveform with a fundamental frequency of 60 Hz.

Here, the entire electric/mechanically configured power grid can be represented as a nonlinear system as shown in Equation 1.

When the solution of Equation 1 vibrates at a certain period, the solution of Equation 1 is expressed in the form of a trajectory in FIG. 2 according to the order, and corresponds to the case where a plane that always intersects in the same direction perpendicular to the trajectory is considered. The plane is called the Poincare plane (Ω).

For example, when the order of the dynamic system is N-dimensional, the order of the determined Poincaré plane is N-1.

If the solution vibrates stably on the Poincaré plane, it appears over a constant vibration period in the vicinity of the fixed point q on the plane, and can be expressed as Equation 3. Also, the relationship between the first intersection point q and the next P(q) can be expressed as in Equation 4.

은 주기적인 해의 초기치의 변화에 대한 시스템 응답을 나타내는 수식으로써, 이 행렬의 고유치를 플로케 지수(Floquet Multiplier, μ)라고 하고 고유벡터는 q₁으로 표시할 수 있다. 임계 플로케 지수(μ₁)가 양의 값을 갖게 되면 주기적인 해는 불안정하게 된다. In Equation 4

Is a formula representing the system response to changes in the initial value of a periodic solution. The eigenvalue of this matrix is called Floquet Multiplier (μ), and the eigenvector can be expressed as q ₁ . When the critical Floquet index (μ ₁ ) becomes positive, the periodic solution becomes unstable.

In order to apply this to time series information to which the present invention is applied, it is expressed as Equation 5 through linearization, and Equation 6 to indicate the stability of the system in the vicinity of the critical Floquet index.

Here, since the critical Floquet index μ ₁ in the steady state has a value that approximates to 1.0, it can be expressed as Equation 7 by approximating Equation 6, and this can be expressed as Equations 8 to 11 to suit the characteristics of time series information. Can be indicated.

In order to construct the Poincare plane, if the derivative of the periodic solution is zero as in Equation 9, it can be expressed as Equation 10, and the solution of the Poincare plane at time τ seconds is according to the natural number n as in Equation 11 It becomes a constant form with no change. In general, different frequency modes may simultaneously participate in the fundamental frequency due to changes in operating conditions or configuration conditions of the power grid, but a mathematical expression for this phenomenon can be expressed as Equations 12 to 15.

The unintended vibration phenomenon in the power grid may be expressed in a form in which a solution vibrating at a periodic fundamental frequency in Equation 1 and a heterogeneous frequency such as Equation 12 are mixed.

에 따라 진동하는 변동분으로 분류될 수 있다. The maximum value of the point or instantaneous waveform on the simplified Poincaré plane can be expressed as Equation 15, and Equation 15 is a constant form (fixed component) of the left term on the right side and the frequency ratio of the right term

It can be classified as a vibrating fluctuation according to.

Therefore, the distance calculation unit 24 is based on the above nonlinear dynamics theory and signal analysis theory, based on the measurement information of voltage (V), current (I) and phase angle (δ), which are the effective values input from the power measurement unit 10. And the rate of change calculated by calculating the rate of change of the measured information are received from the rate of change calculation unit 22.

Here, since the state variables (voltage, etc.) of the power grid derived as the solution of nonlinear dynamics are expressed in the form of a trigonometric function as in Equation 2, the relationship between the rate of change and the two-dimensional plane may be shown in the form of an elliptical trajectory.

Accordingly, as shown in FIG. 3, the distance between the effective value of the steady state and the rate of change can be calculated. For example, when the slope is a positive (+) value less than a specific value (a) and the change in the effective value is negative (-), the distance is calculated from the steady state, and the calculated distance is every one cycle of the vibrating solution. It is updated.

The risk determination unit 26 may determine the risk of differential resonance by calculating a maximum Lyapunov index based on the distance x calculated by the distance calculation unit 24.

Here, the maximum Leapunov index (λ) is calculated as in Equation 16.

Here, Δt is the section length, k is the section, N is the size of the data, i is the measuring device, and x is the distance.

Based on the time series maximum Lyapunov index calculated as in Equation 16, the risk determination unit 26 has a risk of differential resonance due to system instability when the maximum Lyapunov index is positive within the size of N data You can judge what exists.

The display unit 30 may visualize and output the maximum Liafnov index calculated by the control unit 20, and output a determination result of determining the risk of differential resonance so that the operator can recognize the risk.

As described above, according to the nonlinear vibration detection apparatus in the power grid according to an embodiment of the present invention, based on the time series information and change rate of the voltage and current of the effective values obtained in the power grid, the distance value on the two-dimensional coordinate plane By calculating the maximum Lyapunov index and using it to detect nonlinear vibration phenomena caused by interference between components in the power grid in real time, the risk of differential resonance can be determined in real time, thereby stabilizing and reliable power grid. Can improve.

In addition, in a smart grid environment, it is possible to more quickly detect a vibration phenomenon caused by mutual interference between different inverter-based power facilities and to check the risk.

4 is a flowchart illustrating a method of detecting nonlinear vibration in a power grid according to an embodiment of the present invention.

In the nonlinear vibration detection method in the power grid according to an embodiment of the present invention as shown in FIG. 4, first, the control unit 20 determines the voltage, current, and RMS values measured at the bus line of the power grid from the power measurement unit 10. The phase angle measurement information is input (S10).

After receiving the effective value from the power grid in step S10, the control unit 20 calculates a real-time rate of change of the measured information in time series (S20).

Here, the control unit 20 may calculate a rate of change of the measurement information in real time through a delay device.

After calculating the rate of change of the measurement information in step S20, the controller 20 forms a coordinate plane using the measurement information and the rate of change, and calculates the distance between the normal state in the coordinate plane and the measurement point based on the inclination on the coordinate plane. (S30).

Here, as shown in FIG. 3, the control unit 20 forms the Poincare plane, which is a two-dimensional coordinate plane, based on the effective value of the measurement information and the rate of change thereof, and then calculates the distance between the normal state and the measurement point based on the slope on the coordinate plane. Can be calculated.

For example, when the slope is a positive (+) value less than a specific value (a) and the change in the effective value is negative (-), the distance is calculated from the steady state, and the calculated distance is every one cycle of the vibrating solution. It is updated.

After calculating the distance in step S30, the controller 20 calculates the maximum Lyapunov index as shown in Equation 16 based on the calculated distance (S40).

After calculating the maximum Liafnov index in step S40, the control unit 20 determines whether the maximum Liafnov index is a positive number as a set value (S50).

If the maximum Liafnov index is positive in step S50, the control unit 20 determines that there is a risk of differential resonance due to system instability, and outputs the differential resonance risk through the display unit 30 (S60).

If the maximum Liafnov index is negative in step S50, the control unit 20 determines that it is in a stable state and ends.

As described above, according to the nonlinear vibration detection method in the power grid according to the embodiment of the present invention, based on the time series information of the voltage and current of the effective values obtained in the power grid and the rate of change, the distance value on the two-dimensional coordinate plane By calculating the maximum Lyapunov index and using it to detect nonlinear vibration phenomena caused by interference between components in the power grid in real time, the risk of differential resonance can be determined in real time, thereby stabilizing and reliable power grid. Can improve.

In addition, in a smart grid environment, it is possible to more quickly detect a vibration phenomenon caused by mutual interference between different inverter-based power facilities and to check the risk.

The implementation described herein may be implemented in, for example, a method or process, an apparatus, a software program, a data stream or a signal. Although discussed only in the context of a single form of implementation (eg, only as a method), the implementation of the discussed features may also be implemented in other forms (eg, an apparatus or program). The device may be implemented with appropriate hardware, software and firmware. The method may be implemented in an apparatus such as a processor, which generally refers to a processing device including, for example, a computer, a microprocessor, an integrated circuit or a programmable logic device, or the like. Processors also include communication devices such as computers, cell phones, personal digital assistants ("PDAs") and other devices that facilitate communication of information between end-users.

Although the present invention has been described with reference to the embodiments shown in the drawings, this is only illustrative, and those of ordinary skill in the field to which the technology pertains, various modifications and other equivalent embodiments are possible. I will understand.

Therefore, the true technical protection scope of the present invention should be determined by the following claims.

10: power measurement unit 12: voltage measurement unit
14: current measurement unit 16: phase angle measurement unit
20: control unit 22: change rate calculation unit
24: distance calculation unit 26: risk determination unit
30: display

Claims (14)

A power measuring unit that measures a power value in the bus of the power grid;
After receiving the measurement information measured from the power measuring unit, calculating a rate of change of the measurement information, forming a coordinate plane using the measurement information and the rate of change, in the coordinate plane based on the slope on the coordinate plane A control unit that calculates a distance between a steady state and a measurement point, and determines a risk of differential resonance based on the distance; And
And a display unit that outputs the calculation result and the determination result of the control unit.
The method of claim 1, wherein the power measurement unit,
A voltage measuring unit measuring a voltage in the bus;
A current measuring unit that measures a current in the bus; And
And a phase angle measurement unit that measures a phase angle in the bus.
The method of claim 1, wherein the control unit,
A change rate calculator configured to calculate the rate of change in time series with respect to the measurement information input from the power measurement unit;
A distance calculator configured to form a two-dimensional coordinate plane based on the measurement information and the rate of change calculated by the rate of change calculator, and then calculate a distance between a steady state and a measurement point based on a slope on one side of the coordinate; And
And a risk determination unit that determines the risk of differential resonance by calculating a maximum Liafnov index based on the distance calculated by the distance calculation unit.
The apparatus of claim 3, wherein the rate of change calculator calculates the rate of change of the measurement information in real time through a delay.
4. The apparatus of claim 3, wherein the two-dimensional coordinate plane is a Poincare plane.
4. The apparatus of claim 3, wherein the distance calculation unit calculates a distance between a steady state and a measurement point by selecting a value in which the slope on the coordinate plane is within a set range.
[4] The apparatus of claim 3, wherein the risk determination unit determines the risk of resonance of the differential motor when the maximum Liafnov index is positive.
Receiving, by the control unit, measurement information measured at the bus of the power grid from the power measurement unit;
Calculating, by the control unit, a rate of change of the inputted measurement information;
Forming, by the control unit, a coordinate plane using the measurement information and the rate of change, and calculating a distance between a steady state in the coordinate plane and a measurement point based on a slope on the coordinate plane; And
And determining, by the control unit, a risk of differential resonance resonance based on the distance.
The method of claim 8, wherein the receiving of the measurement information comprises receiving, by the control unit, a voltage, current, and phase angle measured by the bus.
9. The method of claim 8, wherein the calculating of the rate of change comprises: the controller calculates the rate of change of the measurement information in real time through a delay device.
The method of claim 8, wherein the calculating of the distance comprises: after the control unit forms a two-dimensional coordinate plane based on the measurement information and the rate of change, the distance between the normal state and the measurement point is calculated based on a slope on one side of the coordinate. Nonlinear vibration detection method in a power grid, characterized in that to calculate.
The method of claim 11, wherein the two-dimensional coordinate plane is a Poincare plane.
The nonlinear power grid according to claim 11, wherein the calculating of the distance comprises calculating a distance between a steady state and a measurement point by selecting a value in which the slope on the coordinate plane is within a set range. Vibration detection method.
The method of claim 8, wherein the determining of the risk of resonance of the differential comprises: after the control unit calculates a maximum Lyafnov index based on the distance, if the maximum Lyafnov index is positive, the risk of differential resonance Nonlinear vibration detection method in the power grid, characterized in that determined by.

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