KR20220034560A - TCSC Impedance Determination Method and TCSC Control Apparatus using Online Grid Data - Google Patents

Abstract

According to the present invention, a thyristor controlled series capacitor (TCSC) impedance determination method using online grid data includes: acquiring grid operation data; determining an overload occurrence state of a line or a transformer by calculating a flow by using the grid operation data at a specific impedance value of a TCSC; calculating an overload index of an entire grid when an overload occurs; calculating a power transmission loss index of the entire grid when the overload does not occur; changing the specific impedance value; determining whether the changed impedance value is within a drivable region, and performing the calculation of the flow again by using the grid operation data at the changed impedance value when the changed impedance value is within the drivable region; and confirming an optimal impedance value by using the calculated overload index and the calculated power transmission loss index when the changed impedance value is out of the drivable region. Accordingly, an optimal operating point is selected even when a grid operation environment is changed rapidly.

Description

TCSC Impedance Determination Method and TCSC Control Apparatus using Online Grid Data

The present invention relates to a TCSC impedance determination method for determining an optimal TCSC impedance for an entire system using system data provided online, such as SCADA, and a TCSC control device for controlling TCSC with the determined TCSC impedance.

Recently, the introduction of FACTS (Flexible AC Transmission System) facilities is being promoted for the purpose of increasing the transmission capacity and improving the stability of the power system. FACTS facilities have fast dynamic characteristics unlike existing manual facilities, and through this, it can contribute to dynamic stability review.

FIG. 1A shows a circuit configuration of a general Thyristor Controlled Series Capacitor (TCSC), and FIG. 1B shows the line impedance control effect by the general TCSC.

A Thyristor Controlled Series Capacitor (TCSC) is a series FACTS (Flexible AC Transmission System) composed of a series capacitor and a thyristor controllable reactor as shown in FIG.

를 연속적으로 제어할 수 있다. 이는 TCSC가 선로에 설치될 때 선로의 임피던스를 제어 할 수 있음을 의미하므로, TCSC를 통하여 송전선로에 흐르는 전력량을 제어할 수 있다.As shown in FIG. 1B, the combined impedance with the series capacitor is adjusted by controlling the amount of current flowing through the reactor through the thyristor firing angle control of the TCSC.

can be continuously controlled. This means that when the TCSC is installed on the line, the impedance of the line can be controlled, so the amount of power flowing through the transmission line can be controlled through the TCSC.

Equation 1 below is the impedance X(α) of the TCSC expressed as a function of the thyristor firing angle α.

, α : 점호각, k=λ/ω, ω=2πf, f=60Hz,

이다.In the above formula,

, α: firing angle, k=λ/ω, ω=2πf, f=60Hz,

am.

2 is a graph showing the TCSC impedance characteristics according to the firing angle.

According to the magnitude of the firing angle, the impedance of the TCSC is derived as shown in Equation 1, which is schematically shown in FIG. 2 . In the graph shown, the X axis is the firing angle, the Y axis is the impedance, α ₀ is the resonance frequency, and α _M is the firing angle limit during capacitive operation. As shown, depending on the size of the firing angle, the TCSC impedance becomes inductive reactance or capacitive reactance. However, there is a resonance region (near α ₀ ) between them, and operation is impossible in this region. In order to compensate the impedance of the transmission line, the TCSC is mainly operated in the capacitive reactance region (X _C ).

3 is a functional block diagram for explaining a control algorithm for impedance control of the aforementioned general TCSC.

4 is a schematic diagram of an IEEE 32 busbar as a rather complicated system example.

As shown in FIG. 3 , when the driver inputs a desired impedance control value (X _ref ) to the controller, a thyristor firing angle (α _ref ) suitable for the impedance is calculated through a linearization process, and the phase of the line current (Phase ) and synchronization, a firing pulse for thyristor firing angle control is derived, and TCSC impedance control, that is, transmission line power current control is performed.

The TCSC impedance control method shown in FIG. 3 is possible for a simple system, but is difficult to apply to a complex system as shown in FIG. 4 . This is because it is difficult for the driver to intuitively know what kind of ripple effect the impedance control (power current control) of the TCSC line will have on other systems.

Due to the above circumstances, for general TCSC operation, it was almost the only response method to perform various systematic analysis in advance to derive operation values for various situations in advance, and then use a method in which the driver issues an input command based on this.

Although this method can be a TCSC operation plan that considers the entire system to some extent, it can be a problem if the current system situation is different from the previously reviewed system scenario. This is due to the need to derive a new operating point that can respond to the system operation environment (exceptional power generation, load loss, line truce) that is significantly different from the system review scenario. This is because, in this case, it is inevitable to select a driving point (impedance) according to the driver's intuition and experience.

Republic of Korea Registration No. 10-1378545

An object of the present invention is to provide a TCSC impedance determination method and a TCSC control device using online system data capable of controlling the impedance of a corresponding line and controlling a power current through it even in a complex system connection structure.

An object of the present invention is to provide a TCSC impedance determination method and a TCSC control device using online system data that can select an optimal operating point even when the system operating environment changes rapidly.

According to an aspect of the present invention, there is provided a method for determining TCSC impedance using online system data, the method comprising: acquiring system operation data; checking whether overload occurs in a line or a transformer by calculating a current using the system operation data at a specific impedance value of TCSC; Calculating an overload index for the entire system when an overload occurs; Calculating the power transmission loss index of the entire system when no overload occurs; changing the specific impedance value; checking whether the changed impedance value is an operable region, and if it is an operable region, performing tidal current calculation again using the system operation data in the changed impedance value; and when out of the operable area, determining an optimal impedance value (impedance value for performing operation) using the calculated overload indexes and power transmission loss indexes.

Here, the method may further include defining an operable impedance region for the TCSC.

Here, in the step of determining the optimal impedance value, pre-calculated overload indices and power transmission loss indices are applied to all operable TCSC impedance values. , the impedance value having the lowest power transmission loss index is determined as the optimum impedance value for the TCSC at the corresponding control time, and if the power transmission loss index does not exist in the calculated result, the impedance value with the lowest overload index, It can be determined as the optimal impedance value for the TCSC at the corresponding control time point.

Here, in the step of determining whether or not the overload occurs, it is possible to check whether or not the overload occurs by determining whether the amount of current flowing through the current calculation exceeds the capacity of each line and the transformer.

Here, in the step of calculating the overload index, the overload index may be calculated according to the following equation.

Here, in the calculating of the power transmission loss index, the power transmission loss index may be calculated according to the following equation.

According to another aspect of the present invention, there is provided an apparatus for controlling TCSC using online system data, comprising: an operation data acquisition unit configured to acquire system operation data; a tidal current calculation unit for calculating a system tidal current at each operating point impedance value of the TCSC using the system operation data and checking whether overload occurs; an overload index calculation unit for calculating an overload index of the system at each operating point impedance value of the TCSC; a trim index calculation unit for calculating a power transmission loss index of the system at each operating point impedance value of the TCSC; an impedance determining unit for determining an optimal impedance value using the overload indexes and power transmission loss indexes calculated for all impedance values belonging to the operable region of the TCSC; a firing angle calculation unit for calculating a thyristor firing angle with respect to the determined optimal impedance value; and a firing unit for controlling the operation of the TCSC with the firing angle.

Here, it may further include a storage unit for storing information on the operable area of the TCSC and the calculated overload indices and power loss indices.

Here, the impedance determining unit applies the overload indexes and power transmission loss indexes calculated for all TCSC impedance values of the operable region and stored in the storage unit, but when there is one or more power transmission loss indexes in the stored result , the impedance value with the lowest power transmission loss index is determined as the optimal impedance value for the TCSC at the time of the control, and if there is no power transmission loss index in the stored result, the impedance value with the lowest overload index is determined At this point, it can be determined as the optimal impedance value for the TCSC.

Here, the current calculation unit may check whether the overload occurs by determining whether the amount of electric power flowing in the system given by the current calculation exceeds the capacity of each line and each transformer belonging to the system.

Here, the overload index calculation unit may calculate the overload index according to the following equation.

Here, the loss index calculator may calculate the power transmission loss index according to the following equation.

If the TCSC impedance determination method and/or the TCSC control device using online system data according to the spirit of the present invention having the above configuration are implemented, the optimal impedance control of the corresponding line and the power current control through it can be performed online even in a complex system connection structure. There is an advantage.

The TCSC impedance determination method and/or TCSC control device using on-line system data of the present invention has the advantage of being able to select an optimal operating point not only in a steady state in a wide-area system but also in a case where the system operating environment changes rapidly.

The TCSC impedance determination method and/or TCSC control device using the online system data of the present invention is connected to EMS/SCADA online and calculates the optimal TCSC operating value based on the current operating system data, so that the efficient system operation is performed. There is an advantage.

Figure 1a is a circuit diagram showing the circuit configuration of a general TCSC (Thyristor Controlled Series Capacitor).
1B is a conceptual diagram illustrating the effect of controlling line impedance by a general TCSC.
2 is a graph showing the TCSC impedance characteristics according to the firing angle.
3 is a functional block diagram for explaining a control algorithm for controlling the impedance of the above-described general TCSC.
4 is a schematic diagram of an IEEE 32 busbar as a rather complicated system example.
5 is a flowchart illustrating a TCSC impedance determination method using online system data according to an embodiment of the present invention.
6 is a system application conceptual diagram illustrating the configuration of an online TCSC optimal impedance control system for performing the TCSC impedance determination method using the online system data shown in FIG. 5 by applying it to the complex system structure of FIG. 4 .
7 is a block diagram illustrating a TCSC control apparatus using online system data according to an embodiment of the present invention.

In describing the present invention, terms such as first, second, etc. may be used to describe various components, but the components may not be limited by the terms. The terms are only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, a first component may be referred to as a second component, and similarly, a second component may also be referred to as a first component.

When a component is referred to as being connected or connected to another component, it may be directly connected or connected to the other component, but it can be understood that other components may exist in between. .

The terminology used herein is used only to describe specific embodiments, and is not intended to limit the present invention. The singular expression may include the plural expression unless the context clearly dictates otherwise.

In this specification, the terms include or include are intended to designate that a feature, number, step, operation, component, part, or combination thereof described in the specification exists, and includes one or more other features or numbers, It may be understood that the existence or addition of steps, operations, components, parts, or combinations thereof is not precluded in advance.

In addition, shapes and sizes of elements in the drawings may be exaggerated for clearer description.

The main purpose of TCSC is to control the impedance of the installed line and control the power flow through it. However, TCSC impedance control affects not only the corresponding line but also the power current of the surrounding wide area system. It is difficult to know the influence of these surrounding systems until TCSC impedance control is performed. Therefore, in the past, the TCSC impedance control value was found in advance through various system analysis using the power system tidal current calculation program, and this was reflected in the TCSC operation by creating a scenario.

However, as described above, this method has a disadvantage in that it is difficult to reflect the optimal operating point in a large-scale real-time system environment. This is especially true in emergency situations, such as the loss of a nearby transmission line due to a system failure.

To solve this problem, it is proposed to derive the optimal TCSC operation value for power system operation by performing power system current calculation based on real-time online system data obtained from SCADA.

To this end, the objective function of the power system as a criterion for determining the optimal TCSC operation value is set, and the optimal TCSC operation value matching the objective function is derived through periodic and iterative current calculations. The objective function may be configured differently from the one exemplified below depending on the purpose of TCSC operation.

As the objective function described above, an overload index and a loss index may be applied.

The objective function is to eliminate overload when line overload occurs (mainly occurs in emergency conditions such as line dropout) and minimize line operation loss when overload does not occur (normal condition). If the current flowing in a specific line is larger than the capacity of the line, it becomes an overloaded line and the overload index increases significantly. When the number of such overload lines increases, the power overload index also increases. It is intended to balance the current of each transmission line in a wide area system without overloading it through impedance variable control of TCSC, and to reduce transmission loss of the entire system.

5 is a flowchart illustrating a TCSC impedance determination method using online system data according to an embodiment of the present invention.

The illustrated online TCSC impedance determination method can execute an algorithm for performing online TCSC optimal control in connection with EMS/SCADA in a steady state or emergency state (line dropout, load increase, etc.). The algorithm may perform stabilization control by feedback control of the TCSC in a transient state due to a system failure or the like.

The method for determining TCSC impedance using the illustrated online system data includes: acquiring system operation data (S120); Checking whether or not an overload of the line or transformer has occurred by calculating the current flow using the system operation data at a specific impedance value (ie, operating point) (S130) (S140); Calculating (and storing) the overload index for the entire system when an overload occurs (S162); Calculating (and storing) the power transmission loss index of the entire system when no overload occurs (S163); changing the specific impedance value (S164); Checking whether the changed impedance value is an operable region (S166), and if it is an operable region, performing tidal current calculation again using the system operation data in the changed impedance value; If it is out of the operable area, the method may include determining an optimal impedance value using the calculated overload indexes and power transmission loss indexes (S168).

Depending on the implementation, the operable impedance region may be defined as a fixed range value, or may be defined by performing the step (S150) of defining the operable impedance region for the corresponding TCSC in advance, and the operable impedance region defined for the corresponding TCSC may be performed. The impedance region may be stored in a predetermined storage unit.

In the tidal current calculation step (S130) first performed for a specific TCSC, the highest impedance value in the operable region may be set or the specific TCSC may be set as an impedance value in operation at the time.

As a result of repeating steps S130 to S166 for all operable TCSC impedance values for the TCSC, an overload index or power transmission loss index is calculated and obtained for each operable TCSC impedance value, and the predetermined may be stored in the storage of

In the step of determining the optimal impedance value (S168), pre-calculated overload indices and power transmission loss indices are applied to all operable TCSC impedance values, but at least one power transmission loss index exists in the calculated result. In this case, the impedance value with the lowest power transmission loss index is determined as the optimum impedance value (ie, operating point) for the TCSC at the corresponding control time, and if the power transmission loss index does not exist in the pre-calculated result, the overload index Determines the lowest impedance value as the optimal impedance value (ie, operating point) for the TCSC at the corresponding control time.

The present invention according to the illustrated flowchart calculates the optimal TCSC operating point for system operation based on the system operation data and uses the overload index and loss index, and uses this as an input to the TCSC controller to maximize the system operation effect. do.

FIG. 6 shows the relationship of the online TCSC optimal impedance control system 100 for performing the TCSC impedance determination method using the online system data shown in FIG. 5 by applying it to the complex system structure of FIG. 4 .

In the step (S120) of acquiring the system operation data, the institution (the power exchange) that operates the power system periodically acquires the state of the power system online through the EMS/SCADA 1000, and performs signal processing (status estimation, etc.) ) to derive the system operation data (PSS/E data) for the power system analysis program (PSS/E).

In the current calculation step (S130), the current calculation is performed with the system operation data derived from the EMS/SCADA (1000), and in the step (S140) of checking whether the overload occurs, the overload of the line or transformer through the current calculation Check for occurrence. In this case, whether overload occurs may be determined by whether the amount of current flowing through the current calculation exceeds the capacity of each line and the transformer.

If there is an overload point, an overload index for the entire system is calculated (S162). The calculated overload index may be later stored in a storage device for comparison with indices obtained at other operating points, and the overload index may be obtained according to Equation 2 below.

The line overload index according to the above equation is the sum of all the electric powers (P, Q) of each line obtained through the current calculation compared to the capacity (MVA) of each branch or transformer (TR).

After that, while changing (increasing or decreasing) the TCSC impedance X _C within the operable range (S164), repeating the calculation of the current flow (S167), when the line or transformer is overloaded, the TCSC impedance X _C with the lowest overload index is operated select by value. For this purpose, the TCSC impedance operation region may be input in advance. As shown in FIG. 2 , the TCSC has a resonance region that cannot be operated between the variable capacitive and inductive reactance. After each overload index calculation, it can be checked whether the overload index calculation for all operation areas is completed (S166).

If, as a result of the current calculation in the current calculation step (S130), there is no overload in the line or the transformer in the system, the power transmission loss index of the entire system at the corresponding impedance value is calculated (S163). This is to generate basis data for later selecting the TCSC impedance X _C with the least loss as the operating value in step S168. The power transmission loss index of the entire system at the corresponding impedance value can be obtained according to Equation 3 below.

Through the optimal value determination algorithm performed in the step (S168) of determining the optimal impedance value, if the overload index minimization TCSC impedance value and the TCSC impedance value with the greatest loss reduction effect are derived together, the overload index minimization TCSC impedance value is final It is selected as the TCSC operating value. This is because the system overload situation is judged as a more critical situation (emergency state). In practice, in this situation, the overload index is calculated for all impedance values, and the loss index is not calculated.

In a steady-state system without overload, the overload index or loss index is calculated for all impedance values, and the TCSC impedance with the greatest loss reduction effect is selected as the operating value.

Thereafter, the TCSC is controlled with the determined optimal TCSC impedance value (eg, firing angle control), which is similar to that described with respect to the prior art, and overlapping descriptions will be omitted.

7 is a block diagram illustrating a TCSC control apparatus using online system data according to an embodiment of the present invention.

The illustrated TCSC control device 100 includes an operation data acquisition unit 120 for acquiring system operation data from the EMS/SCADA 1000; a tidal current calculator 130 for calculating a system tidal current at each operating point impedance value of the TCSC 10 using the system operation data and checking whether overload occurs; an overload index calculation unit 160 for calculating an overload index of the system at each operating point impedance value of the TCSC 10; a trim index calculation unit 170 for calculating a power transmission loss index of the system at each operating point impedance value of the TCSC (10); an impedance determining unit 180 for determining an optimal impedance value using the overload indexes and power transmission loss indexes calculated for all impedance values belonging to the operable region of the TCSC (10); a firing angle calculation unit 190 for calculating a thyristor firing angle with respect to the determined optimal impedance value; and a firing unit 195 for controlling the operation of the TCSC 10 with the firing angle.

Although not shown, the TCSC control device 100 may further include a storage unit for storing information on the operable area of the TCSC 10 and the calculated overload indices and power loss indices.

The operation data acquisition unit 120, an institution (power exchange) operating the power system periodically acquires information on the state of the power system (ie, system operation data) online through the EMS/SCADA 1000 . For this purpose, it may be provided with a communication module for performing mutually prescribed wired/wireless communication with the institution and security modules for accessing the institution.

The current calculation unit 130 applies the system operation data received from the operation data acquisition unit 120 to a specific impedance value (ie, an operating point) for the TCSC, calculates the current flow, and as a result, the line Alternatively, it is possible to check whether the transformer is overloaded. Whether or not overload occurs can be determined by whether the amount of current flowing through the current calculation exceeds the capacity of each line and transformer.

The overload index calculation unit 160 may calculate an overload index for the system when controlling the TCSC with the specific impedance value. For example, the overload index may be calculated according to Equation 2 above.

The loss index calculation unit 170 may calculate a power transmission loss index for the system when controlling the TCSC with the specific impedance value. For example, the power transmission loss index may be calculated according to Equation 3 above.

The impedance determining unit 180 applies the overload indexes and power transmission loss indexes previously calculated for all operable TCSC impedance values and stored in the storage unit, but the power transmission loss index is one of the results stored in the storage unit. If there is an abnormality, the impedance value with the lowest power transmission loss index is determined as the optimum impedance value (ie, operating point) for the TCSC at the corresponding control time, and if there is no power transmission loss index in the stored result, overload The impedance value having the lowest index may be determined as the optimal impedance value (ie, the operating point) for the TCSC at the corresponding control time point.

The firing angle calculation unit 190 and the firing unit 195 are for controlling the TCSC by calculating the firing angle with the determined optimal TCSC impedance value, like the linearization block and firing pulse generator shown in FIG. 3 . , can be implemented according to the prior art, and in this case, the thyristor firing angle α can be calculated to satisfy Equation 1 above.

Those skilled in the art to which the present invention pertains should understand that the present invention may be embodied in other specific forms without changing the technical spirit or essential characteristics thereof, so the embodiments described above are illustrative in all respects and not restrictive. only do The scope of the present invention is indicated by the following claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts should be construed as being included in the scope of the present invention. .

10: TCSC 100: TCSC control device
120: operation data acquisition unit 130: tide calculation unit
160: overload index calculation unit 170: grooming index calculation unit
180: impedance determination unit 190: firing angle calculation unit
195: roll call
1000: EMS/SCADA

Claims (12)

acquiring system operation data;
checking whether overload occurs in a line or a transformer by tidal current calculation using the system operation data at a specific impedance value of TCSC;
Calculating an overload index for the entire system when an overload occurs;
Calculating the power transmission loss index of the entire system when no overload occurs;
changing the specific impedance value;
checking whether the changed impedance value is an operable region, and if it is an operable region, performing tidal current calculation again using the system operation data at the changed impedance value; and
When out of the operable area, determining an optimal impedance value using the calculated overload indices and power transmission loss indices
TCSC impedance determination method comprising a.
According to claim 1,
defining an operable impedance region for the TCSC;
TCSC impedance determination method further comprising a.
According to claim 1,
In the step of determining the optimal impedance value,
Pre-calculated overload indices and power transmission loss indices are applied to all operable TCSC impedance values, but if there is more than one power transmission loss index in the calculated result, the impedance value with the lowest power transmission loss index is selected; It is determined as the optimum impedance value for the TCSC at the control time point, and if the power transmission loss index does not exist in the pre-calculated result, the impedance value with the lowest overload index is set as the optimum impedance value for the TCSC at the control time point Determining TCSC Impedance Determination Method.
According to claim 1,
In the step of checking whether the overload occurs,
TCSC impedance determination method that checks whether overload occurs by judging whether the amount of current flowing through the current calculation exceeds the capacity of each line and transformer.
According to claim 1,
In the calculating of the overload index, the TCSC impedance determination method for calculating the overload index according to the following equation.

According to claim 1,
In the calculating of the power transmission loss index, the TCSC impedance determination method for calculating the power transmission loss index according to the following equation.

an operation data acquisition unit for acquiring system operation data;
a tidal current calculation unit for calculating a system tidal current at each operating point impedance value of the TCSC using the system operation data and checking whether overload occurs;
an overload index calculation unit for calculating an overload index of the system at each operating point impedance value of the TCSC;
a trim index calculation unit for calculating a power transmission loss index of the system at each operating point impedance value of the TCSC;
an impedance determination unit for determining an optimal impedance value using the overload indexes and power transmission loss indexes calculated for all impedance values belonging to the operable region of the TCSC;
a firing angle calculation unit for calculating a thyristor firing angle with respect to the determined optimal impedance value; and
A firing unit that controls the operation of the TCSC with the firing angle
TCSC control device comprising a.
8. The method of claim 7,
A storage unit for storing information on the operable area of the TCSC and the calculated overload indices and power loss indices
TCSC control device further comprising a.
9. The method of claim 8,
The impedance determining unit,
The overload indices and power transmission loss indices that are calculated for all TCSC impedance values of the operable region and stored in the storage unit are applied. The low impedance value is determined as the optimal impedance value for the TCSC at the control time point, and if there is no power transmission loss index in the stored result, the impedance value with the lowest overload index value is the optimal impedance value for the TCSC at the control time point. TCSC control device that determines the impedance value.
8. The method of claim 7,
The algae calculator,
A TCSC control device for checking whether or not the overload occurs by checking whether the amount of electric power flowing in the system given by the current calculation exceeds the capacity of each line and each transformer belonging to the system.
8. The method of claim 7,
The overload index calculation unit, TCSC control device for calculating the overload index according to the following equation.

8. The method of claim 7,
The loss index calculator, TCSC control device for calculating the power transmission loss index according to the following equation.

Images