KR102174780B1 - Multi-Infeed HVDC System - Google Patents

Abstract

The present disclosure assumes a multi-infeed HVDC transmission system, which is composed of two or more HVDC transmission systems of different specifications, in consideration of the system characteristics as described above, and multi-infeed. The optimal operating capacity calculation method for the efficient operation of the HVDC transmission system is presented, and the optimal operating capacity calculation algorithm is presented through this, and the optimal operating capacity for each HVDC transmission system using the calculation algorithm for the load prediction value of the future Jeju system. It has an advantage that can be presented.
The multi-infeed HVDC system considering the system characteristics of the Jeju region according to an embodiment of the present disclosure is the MIESCR (Multi-infeed Interactive Effective Short Circuit Ratio), which is a reliability criterion for the power supply to the Jeju region and the stable operation constraint of the Jeju system and HVDC transmission system Each HVDC that composes a multi-infeed HVDC system based on the calculation step of calculating the stable operation limit capacity of the HVDC transmission system for each generator operation case in Jeju region based on the effective inertia constant of the system and the system. In order to calculate the optimal operating capacity for each system, the presentation step presents an algorithm for calculating the optimal operating capacity using a genetic algorithm, and the multi-infeed for the seasonal load prediction situation in Jeju using the algorithm of the presentation step. ) Characterized in that it comprises a calculation step of calculating the operating capacity of each HVDC transmission system that satisfies the stable operation constraint of the HVDC transmission system.

Description

Multi-Infeed HVDC System {Multi-Infeed HVDC System}

The content disclosed in this specification relates to a multi-unit HVDC system in consideration of the system characteristics, and in particular, the additional construction of the land-Jeju high-voltage direct current (HVDC) system and the future power system characteristics of the multi-unit ( Multi-Infeed) This is a multi-unit HVDC system that considers the characteristics of the Jeju area system that can present the optimal operating capacity of each HVDC transmission system through the setting of the optimal operating capacity calculation plan for each HVDC transmission system for establishing an efficient operation plan for the HVDC system. About.

Unless otherwise indicated herein, the content described in this section is not prior art to the claims of this application, and inclusion in this section is not admitted to be prior art.

Countries around the world are making continuous efforts to facilitate power supply through connection of power systems between countries or long-distance power transmission due to the increase in power demand, the opening of the power market, and the increase in demand for improvement in power supply reliability. .

These changes in the environment surrounding the power market are increasing the importance of maximizing the configuration and operation of the power system. Until now, power transmission has been performed using an alternating current (AC) method and an AC-DC converter that connects with the existing AC system. It can be divided into a direct current (DC) method that transmits power through mutual conversion of AC and DC.

Until now, most of the power transmission has been performed by the AC transmission method, but in recent years, due to the advantages of the DC transmission method and the development of large-capacity power electronic devices and related technologies, long distance, large-capacity power transmission and connection between power systems with different frequencies, etc. There is a trend of increasing the number of application cases around the world.

In Korea, the #1 HVDC transmission system was installed between the land (Haenam) and Jeju for the first time in 1998, and the #2 HVDC was added between Jindo and Seojeju in 2012 and is still in operation. The operation of the land-Jeju transmission system made it possible to operate in conjunction with the Jeju system, which was an independent system before that time, and the relatively large land system, thereby improving the reliability of power supply in the Jeju area.

In addition, it was possible to achieve economic effects by replacing the relatively expensive power generation power of the Jeju system with the power generation power of the land system. If the #3 HVDC transmission system is additionally constructed and operated as planned in the future, the effect obtained through the linked operation of the land system and the Jeju system is expected to increase further.

In this way, if the #2 HVDC transmission system is constructed and operated simultaneously with the #1 HVDC transmission system, the land system and the Jeju system are connected through the multi-infeed HVDC transmission system.

In this case, for the stable operation of the Jeju system and the HVDC transmission system, the need for a system review considering the characteristics of the multi-unit HVDC transmission system and establishment of an operation strategy for each HVDC system constituting the multi-unit HVDC transmission system based on the results will increase. will be.

If the 3HVDC transmission system is additionally constructed, the Jeju system will be operated in conjunction with the multi-tier HVDC transmission system considering both the land system and the reverse transmission, and this will increase the reliability of the power supply of the Jeju system as well as economic benefits compared to the present. do.

According to the plans so far, the basic specifications and system types of #3 HVDC transmission systems to be added in the future are expected to be different from the current HVDC transmission systems currently in operation. As a result, the operating conditions for each HVDC transmission system are also It is expected to change according to various conditions.

In addition, in terms of increasing the operating effect of the land-to-Jeju multi-unit HVDC transmission system, it will be more advantageous as the amount of transmission through the multi-unit HVDC transmission system increases, but considering the problems that may occur in the Jeju system, including accidents, transmission through the multi-unit HVDC transmission system is possible. There will be a transmission limit that can be achieved.

Therefore, it is necessary to calculate the optimal operating capacity of the HVDC transmission system under the transmission limit based on the interaction between each HVDC transmission system in the multi-phase HVDC transmission system and characteristics of the Jeju system.

1. Korean Patent Application Publication No. 10-2014-0134110 (November 21, 2014)

2. Korean Patent Application Publication No. 10-2013-0035054 (2013.04.08.)

In order to establish an efficient operation plan of the land-to-Jeju multi-unit HVDC system considering the additional construction of the land-Jeju HVDC system in the future and the characteristics of the power system in the future Jeju region, the optimal operating capacity calculation plan of each HVDC transmission system was set, and each HVDC transmission system was We intend to provide a multi-unit HVDC system in consideration of the system characteristics of the Jeju region that can present the optimum operating capacity.

The multi-unit HVDC system considering the system characteristics of the Jeju region according to the embodiment is effective with the MIESCR (Multi-infeed Interactive Effective Short Circuit Ratio), which is the reliability standard for power supply to the Jeju region, and the stable operation constraint of the Jeju system and HVDC transmission system. Optimal for each HVDC system constituting a multi-infeed HVDC system based on the calculation step of calculating the stable operation limit capacity of the HVDC transmission system for each generator operation case in Jeju region based on the inertial constant standard and the calculation value of the calculation step. Multi-infeed HVDC transmission for seasonal load prediction conditions in Jeju area using the algorithm of the presentation step and the presentation step that presents an algorithm for calculating the optimal driving capacity using a genetic algorithm for the calculation of the driving capacity. There is provided a multi-function HVDC system in consideration of system characteristics in Jeju, characterized in that it comprises a calculation step of calculating an operating capacity for each HVDC transmission system that satisfies the stable operation constraints of the system.

Multi-infeed HVDC system in consideration of the system characteristics of the Jeju region as described above is based on a multi-infeed HVDC transmission system composed of two or more HVDC transmission systems. The optimal operating capacity calculation method for the efficient operation of the transmission system is presented, and the optimal operating capacity calculation algorithm is presented through this, and the optimal operating capacity for each HVDC transmission system is calculated using the calculation algorithm for the load prediction value of the future Jeju system. It has an advantage that can be presented.

1 is a view showing an algorithm for calculating the optimal operating capacity of a multi-unit HVDC in a multi-unit HVDC system in consideration of system characteristics in Jeju according to an embodiment of the present disclosure.
2 is a view showing a load prediction data graph in Jeju.
3 is a view showing a case1 generator operation scenario MIESCR of a multi-unit HVDC system in consideration of system characteristics in Jeju according to an embodiment of the present disclosure.
4 is a view showing a system effective inertia constant, which is one of the constraints of stable operation of a multi-unit HVDC system in consideration of system characteristics in Jeju according to an embodiment of the present disclosure.
5 is a view for explaining operation of a summer load scenario of a multi-unit HVDC system in consideration of system characteristics in Jeju according to an embodiment of the present disclosure.
6 is a view for explaining the operation of an estimated load scenario of a multi-unit HVDC system in consideration of system characteristics in Jeju according to an embodiment of the present disclosure.
7 is a view for explaining the operation of a winter load scenario of a multi-unit HVDC system in consideration of system characteristics in Jeju according to an embodiment of the present disclosure.

Advantages and features of the present invention, and a method of achieving them will become apparent with reference to the embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in a variety of different forms, only the present embodiments are intended to complete the disclosure of the present invention, and the general knowledge in the technical field to which the present invention pertains. It is provided to completely inform the scope of the invention to those who have it, and the invention is only defined by the scope of the claims. The same reference numerals refer to the same elements throughout the specification.

In describing embodiments of the present invention, if it is determined that a detailed description of a known function or configuration may unnecessarily obscure the subject matter of the present invention, a detailed description thereof will be omitted. In addition, terms to be described later are terms defined in consideration of functions in an embodiment of the present invention, which may vary according to the intention or custom of users or operators. Therefore, the definition should be made based on the contents throughout this specification.

1 is a diagram showing an algorithm for calculating the optimal operating capacity of a multi-unit HVDC in a multi-unit HVDC system in consideration of system characteristics in Jeju according to an embodiment of the present disclosure, FIG. 2 is a view showing a load prediction data graph in Jeju, and FIG. 3 is a diagram of the present disclosure. A diagram showing a Case1 generator operation scenario MIESCR of a multi-unit HVDC system considering system characteristics in Jeju according to an embodiment, and FIG. 4 is one of the constraints of stable operation of a multi-unit HVDC system in consideration of system characteristics in Jeju according to an embodiment of the present disclosure. It is a diagram showing the system effective inertia constant.

The multi-unit HVDC system in consideration of the system characteristics of the Jeju region of the present disclosure is based on the reliability of power supply to the Jeju region, the MIESCR (Multi-infeed Interactive Effective Short Circuit Ratio) and system effective inertia, which are the constraints of stable operation of the Jeju system and HVDC transmission system An optimal operation for each HVDC system constituting a multi-infeed HVDC system based on the calculation step of calculating the stable operation limit capacity of the HVDC transmission system for each generator operation case in Jeju region based on the constant standard and the calculation value of the calculation step. Multi-infeed HVDC transmission system for the seasonal load prediction situation in Jeju area using the algorithm of the presenting step and the presentation step that presents an algorithm for calculating the optimal operating capacity using a genetic algorithm for capacity calculation. It includes a calculation step of calculating the operating capacity of each HVDC transmission system that satisfies the stable operation constraint of.

The calculation step for calculating the HVDC system stability operation index of the present disclosure will be described.

In the HVDC transmission system, the converter is a key part that performs mutual conversion of AC↔DC power and is composed of power electronic devices. HVDC systems can be classified into current type (LCC or CSC) HVDC and voltage type (VSC) HVDC according to the characteristics of power electronic devices constituting such a converter.

Here, current-type HVDC refers to a traditional HVDC transmission system, and is expressed as LCC-HVDC or CSC-HVDC, and since the current-type HVDC transmission system mainly uses a valve composed of a Thyristor element, the AC current by the current-type HVDC transmission system is Always out of phase than AC voltage. Due to these characteristics, when operating a current-type HVDC transmission system, reactive power is necessarily consumed. Therefore, for normal operation of a current-type HVDC system, reactive power equivalent to about 50% to 60% of the DC power transmission amount must be supplied from the system. The amount of reactive power supply increases as the amount of DC power transmission increases, and this may adversely affect the entire system including the AC system connected to the HVDC system. Therefore, compensation for reactive power required for operation of a current-type HVDC transmission system must be achieved using AC filters, parallel capacitors, synchronous control devices, and FACTS devices.

When the system is connected by the HVDC transmission system, the robustness of the rear AC system affects the operation of the HVDC transmission system. In particular, in the case of current type HVDC, the problem of commutation failure must always be considered, which is closely related to the robustness of the rear AC system. Since the robustness of the rear AC system is determined by the Thevenin equivalent impedance of the system, if the Thevenin equivalent impedance is large, it may cause a problem in system stability in the transient state. As such, the robustness of the AC system is expressed as SCR (Short Circuit Ratio), which is the ratio of the AC system fault capacity to the HVDC transmission and reception capacity. This parameter is expressed as the ratio of the fault capacity equation (1) and the HVDC operating capacity at the point where the converter is connected and is calculated as in equation (2). In terms of securing the stability of the entire system, the larger the two parameters of the AC system to which the HVDC transmission system is connected, the more advantageous, and if it is smaller than the standard value, additional system reinforcement is required for stable operation of the entire power system.

(1)

(One)

(2)

(2)

(3)

(3)

here,

: 컨버터 접속 모선 전압

: Converter connection bus voltage

: 컨버터 접속 모선 등가임피던스

: Equivalent impedance of the converter connection bus

: HVDC시스템 송수전전력 (DC Power)

: HVDC system transmission and reception power (DC Power)

: HVDC시스템이 연계되는 AC Bus에 접속된

: Connected to AC Bus to which HVDC system is connected

Capacities of capacitors, filters, etc.

라 하고 이것을 테브난 등가임피던스에 포함시켜 식 (3)과 같이 계산하며 그 값은 SCR 보다 감소하게 된다.In particular, ESCR (Effective Short Circuit Ratio) is a parameter to consider the effect of a capacitor or filter added to an HVDC AC system.

It is calculated as Equation (3) by including this in Thevenin equivalent impedance, and the value is reduced than SCR.

The ESCR of a multi-infeed HVDC system in which several HVDC transmission systems are connected to the same AC system and operated at the same time must consider the mutual effect of each HVDC system, and for this purpose, it responds to the ESCR of the single-infeed HVDC system. Calculate and apply MIESCR (Multi-infeed Effective Short Circuit Ratio).

는 다음과 같다.Meanwhile, the effective inertia constant in this disclosure

Is as follows.

Effective inertia constant refers to the ability to maintain the frequency of the power system by the rotational inertia of the AC system.According to IEEE Standard 1204-1997, the effective inertia constant must be 2.0 or more for stable operation of the HVDC transmission system. Demands. In general, situations that can cause a reduction in the frequency of the system may include the following cases.

＊ HVDC transmission system current failure (Commutation failure)

(Consider current failure between buses with MIIF of 0.6 or more)

＊ Accident at the transmission or reception of the HVDC transmission system

＊ HVDC transmission line accident

When the effective inertia constant (Hdc) is “2” or more, it is the most severe system accident. When the power is supplied to the system only with the HVDC system, and the system returns from the system accident 0.2 seconds after all of them are eliminated, the frequency fluctuation is within 5%. This is the number you want to keep. Equations (4) and (5) below show the relationship between the frequency change and the inertia constant.

(4)

(4)

or

(5)

(5)

here,

: 정격주파수

: Rated frequency

: 주파수 변화량

: Frequency change amount

: 발전기의 관성정수

: Generator's inertia constant

: 발전기 기계적 입력

: Generator mechanical input

: 발전기 전기적 출력

: Generator electrical output

라고 하며 일반적으로 HVDC 송전시스템 및 계통의 안정도를 고려하여 권장되는 유효관성정수의 값인 2.0은 다음의 식 (6)에 의하여 계산된다.In the above equation, the effective inertia constant (H) is expressed in terms of DC power.

In general, the recommended effective inertia constant of 2.0, considering the stability of the HVDC transmission system and system, is calculated by the following equation (6).

(6)

(6)

On the other hand, the multi-infeed HVDC transmission system stability operation index of the present disclosure is as follows.

As explained above, the need for securing the reliability of the power system and controlling the power flow is increasing more than ever with the spread of the power market opening. For this reason, there is a trend of increasing application cases for HVDC transmission systems worldwide. Due to the continuous increase of such HVDC transmission systems, more than two HVDC transmission systems in the same AC system are applied to the same area. In this way, there is a case in which the electrical distance between the points where the HVDC transmission system applied to the system is connected to or connected to the substation bus of the same AC system is close. Such two or more HVDC transmission systems are referred to as multi-unit HVDC transmission systems. For the normal operation of a multi-infeed HVDC transmission system, unlike the single-infeed HVDC system, not only the interaction with the rear AC system but also the interaction between each HVDC transmission system constituting the multi-infeed HVDC system It is also necessary to review the action. Due to this feature, in order to consider the influence between the rear AC system and each HVDC transmission system when reviewing the system for the multi-infeed HVDC transmission system, in addition to the existing parameters applied when reviewing the single-infeed HVDC system. Separate parameters need to be reviewed.

For this purpose, the MIIF (Multi-infeed Interaction Factor) of the present disclosure is a parameter for predicting the degree of interaction between two AC buses to which each HVDC transmission system constituting a multi-infeed HVDC transmission system is connected. . When two HVDC transmission systems are applied to the same AC system, MIIF from Converter 1 to Converter 2 is expressed as MIIF2,1 and calculated as Equation (7).

(7)

(7)

In other words, MIIF2,1 represents the ratio of the voltage drop of Converter 2 to the voltage drop of Converter 1, so if the value of MIIF is “1”, the two AC buses to which the converter is connected are the same bus, and if “0”, each converter It means that the two AC buses connected to are infinitely far apart. The MIIF parameter is used as a basic element to calculate ESCR in a multi-infeed HVDC transmission system.

For this purpose, the MIESCR (Multi-infeed Effective Short Circuit Ratio) of the present disclosure is a parameter indicating the robustness of the rear AC system in a multi-infeed HVDC system like the ESCR of a single-infeed HVDC system. . In general, if the MIESCR of the multi-infeed HVDC system is greater than 3, the HVDC transmission system is considered to be connected to the strong AC system, and if it is less than 2, the MIESCR is considered to be connected to the weak AC system. It is recommended to be 2.5. When one HVDC system is connected to Bus i of AC system, MIESCR of this HVDC system is called MIESCR_i and it is calculated as Equation (8).

(8)

(8)

here,

: HVDC가 접속된 Bus_i의 고장용량

: Fault capacity of Bus_i to which HVDC is connected

: Bus_i에 접속된 캐패시터, 필터의 용량

: Capacity of capacitor and filter connected to Bus_i

: Bus_i에 접속된 HVDC 송수전용량(DC power)

: HVDC transmission capacity connected to Bus_i (DC power)

: Bus_i이외 Bus에 접속된 HVDC의 송수전용량(DC Power)

: Transmission capacity of HVDC connected to bus other than Bus_i (DC Power)

: HVDC_i에서 HVDC_j로의 MIIF

: MIIF from HVDC_i to HVDC_j

A method of estimating a stable operating point of a multi-unit HVDC in a multi-unit HVDC system in consideration of the system characteristics of the Jeju region according to the above description will be described.

First, the existing single-infeed (hereinafter, referred to as'#1') HVDC system operation method, the proportion of the power supply by the #1 HVDC transmission system to the total power supply to the Jeju area is 2 ( Hereinafter, it is referred to as'#2') HVDC occupied about 30% on average before operation. In addition, the operating capacity of the #1 HVDC transmission system accounts for about 26% of the total power generation capacity in Jeju as of 2011, and the share of the #1 HVDC transmission system in the total power system in Jeju is not small. For this reason, if the #1 HVDC transmission system is stopped due to various factors during operation, it is highly likely to affect the stability of the entire Jeju system. Because of this, constraints are set on the amount of power supplied through the #1 HVDC transmission system among the total power supply to the Jeju system, and the system is operated.

These constraints limit the amount of power supplied through the #1 HVDC transmission system under normal conditions to the lesser of 50% of the total power demand in Jeju and 150[㎿]. If this constraint is expressed as an equation, it is as follows.

(9)

(9)

This is to minimize the effect on the Jeju system due to a failure of the #1 HVDC transmission system during operation, and the power supplied through the HVDC transmission system is adjusted even when the operation environment of the Jeju system such as synchronous controller operation restrictions is changed. Under normal conditions, the #1 HVDC system is operating in constant frequency mode.

Meanwhile, an algorithm for estimating an operating point of a multi-infeed HVDC system of a multi-infeed HVDC system in consideration of the system characteristics of the Jeju region of the present disclosure will be described.

The optimum operating capacity of each HVDC transmission system in the multi-infeed HVDC transmission system applied in the present disclosure was calculated using the algorithm of FIG. 1. This is to first classify the minimum generator constraint cases according to the load situation in the Jeju area, and examine whether the respective criteria for the stable operation constraint MIESCR and the effective inertia constant are satisfied for each case, and if both of these constraints are satisfied #1, #2 This is an algorithm that calculates the operating capacity of each HVDC transmission system.

The operating capacity of each HVDC transmission system in the multiple HVDC system used an optimization technique that minimizes the MIESCR difference of the receiving end (inverter side) bus for each HVDC transmission system. This is because the MIESCR value relative to the operating capacity of the HVDC transmission system has a non-linear functional relationship due to filter operation, etc., so the optimal operating capacity for each HVDC transmission system was calculated using a genetic algorithm, one of the optimization techniques.

Genetic Algorithm (GA) is a probabilistic optimal solution search method that mimics the evolutionary process of ecosystems made according to natural selection and genetic laws. In the process of ecosystem evolution, individuals who have adapted well to a given environment survive and leave offspring, and the offspring inherit excellent genes and adapt to the environment again, and on the contrary, individuals who cannot adapt to the environment are eliminated. As this process is repeated several times, only the most suitable individual survives the given environment. The genetic algorithm to which this concept is applied is a population consisting of a large number of individuals made through various combinations of solutions to be optimized, and a fitness function for evaluating the fitness for the purpose of optimization for each individual. Will be set. For each individual in the set population, each adaptability is evaluated through an adaptability function, and an individual inherited to the next generation is selected based on this. As the adaptability evaluation for the selected objects is repeatedly performed, the process of creating a new object with higher adaptability is repeated, and finally, the process of finding the object with the highest adaptability, that is, an optimal solution.

The set values and relational expressions of the genetic algorithm applied to the present disclosure are as follows, and an objective function for uniformly optimizing the MIESCR margin of the converter station connection bus was set.

A case study will be described in which a multi-unit HVDC system is applied in consideration of the system characteristics of the Jeju region of the present disclosure as described above.

First, the condition of the case study is that after the #2 HVDC transmission system is put in, the operation of the multi-infeed HVDC system is not a conventional fixed operation method because the land and Jeju systems are connected by a multi-infeed HVDC system. It is necessary to establish a new operation plan that considers the load situation in the Jeju area, supply reliability, and system stability. Therefore, in this disclosure, a study was conducted to calculate the optimal operation plan of the multi-infeed HVDC system between land and Jeju by reflecting the known specifications of the currently operating #1 and #2 HVDC transmission systems. In the case of the daily load prediction data, which is the subject of the case study, as shown in Fig. 1, the summer load data with the highest load, the estimated load data with the lowest load, and the winter load data with the lowest daily load level as shown in FIG. The daily load for the simulation was calculated using the following cases.

In addition, in order to secure the reliability of the power supply of the power system in Jeju, it is necessary to operate with a spare capacity so that there is no problem with the power system operation even in the event of an HVDC transmission system accident. For the calculation of the spare capacity at this time, the #1 HVDC bipolar stop, which is the largest generation power of the Jeju system, must be considered by applying the N-1 system reliability standard. Unlike the normal bipolar HVDC transmission system, the reason why the #1 HVDC transmission system treats the bipolar system stop as one N-1 accident case is because of the characteristics of the #1 HVDC system, two poles operate at the same time in case of a busbar accident on the DC line. Because it can be stopped. Therefore, when #1 HVDC and #2 HVDC systems are operated at the same time, the operating capacity of #1 HVDC is 300 [㎿] in preparation for bipolar failure of #1 HVDC system out of 700 [㎿], which is the total operable capacity of the HVDC transmission system. In case of operation considering the reserve capacity for accidents, the limit operation capacity of the two HVDC transmission systems is 400 [㎿].

In conclusion, the limit operating capacity of the entire HVDC transmission system according to the N-1 communication fastness standard is as follows, and this limit capacity is one constraint for calculating the proper operating capacity of the land-Jeju multi-infeed HVDC transmission system. do.

HVDC total capacity 700 ㎿

Free margin 300 ㎿

----------------------------

HVDC maximum operating capacity ≤ 400 ㎿

*) 400 ㎿: #1 HVDC + #2 HVDC

For stable operation of the HVDC system, it is necessary to secure the marginal capacity considering the N-1 reliability standard mentioned above, and also satisfy the standard values for the MIESCR and effective inertia constant described above. Therefore, the reference values of these two parameters become another constraint for the stable operation of the multi-infeed HVDC transmission system. In order to review whether the constraints for these two parameters are satisfied, it is necessary to know the short circuit capacity of the conversion station bus of each HVDC transmission system and the AC inertia value of the Jeju system for each generator operation scenario in the Jeju system.

Meanwhile, FIG. 5 is a view for explaining the operation of a summer load scenario of a multi-unit HVDC system in consideration of system characteristics in Jeju according to an embodiment of the present disclosure, and FIG. 6 is a multi-unit HVDC in consideration of system characteristics in Jeju according to an embodiment of the present disclosure. 7 is a diagram for explaining the operation of the estimated load scenario of the system, and FIG. 7 is a diagram for explaining the operation of a winter load scenario of a multi-unit HVDC system in consideration of system characteristics in Jeju according to an embodiment of the present disclosure.

Hereinafter, a case study result of a multi-unit HVDC system in consideration of the system characteristics of the Jeju region of the present disclosure as described above will be described.

First, in order to calculate the operating capacity of the HVDC transmission system for each section, the minimum generator limit for each generator operation scenario was reviewed with the capacity for securing the N-1 system reliability as the HVCD operating capacity limit. As a result, as shown in Table 1, Case 1 did not satisfy the MIESCR stability constraint.

In other words, in the case of the generator operation scenario of Case 1, the result was unstable for the 400 MW operating capacity of the HVDC transmission system considering the reliability of the N-1 system. Therefore, in Case 1's generator operation scenario, the maximum stable operation capacity of the HVDC transmission system was additionally reviewed. In this disclosure, it is assumed that the operating capacity of the HVDC transmission system is adjusted by 10 ㎿ in order to calculate the maximum operating capacity that satisfies the MIESCR constraint, and as a result of sequential simulations starting from 400 ㎿, stable results up to the operating capacity of the HVDC system of 370 ㎿ are obtained. I could get it. The results are shown in FIG. 3. In addition, for one of the constraints on stable operation of the HVDC transmission system, the system satisfies the stable operation criteria for all generator operation scenarios as shown in FIG. Based on this result, the results of simulating the optimum operating capacity of HVDC for the predicted values of daily load changes in summer, autumn, and winter were as shown in FIGS. 5, 6, and 7. As shown in Equation (10), the optimum operating point of HVDC was calculated using a dielectric algorithm to maximize the MIESCR margin of each converter station connection bus as shown in Equation (10) according to the flowchart of FIG.

In the case of the summer and winter load scenarios of Figs. 5 and 7, the HVDC operating capacity was hardly decreased due to the minimum generator constraint, but during the autumn load, the HVDC operating capacity decreased due to the minimum generator constraint, and the MIESCR value of each HVDC was maximized. Figure 6 shows the amount of driving.

Hereinafter, the conclusion of the multi-unit HVDC system in consideration of the system characteristics of the Jeju region of the present disclosure as described above will be described.

Currently, after the construction of the #2 HVDC transmission system between land and Jeju, the land and Jeju systems are operating in conjunction through two HVDC transmission systems. Therefore, in this disclosure, a multi-infeed HVDC transmission system composed of two or more different specifications HVDC transmission systems is assumed, and the optimum operating capacity is calculated for the efficient operation of the multi-infeed HVDC transmission system. The plan was reviewed and an algorithm for calculating the optimal operating capacity was suggested. In addition, the optimal operating capacity for each HVDC transmission system was presented using the calculation algorithm for the load prediction of the future Jeju system.

First, the limit capacity for stable operation of the HVDC transmission system for each generator operation case in Jeju was calculated based on the reliability standard of power supply to the Jeju region, MIESCR, which is the constraint of stable operation of the Jeju system and HVDC transmission system, and the system effective inertia constant standard. Based on this, an algorithm for calculating the optimal operating capacity for each HVDC system constituting the Multi-Infeed HVDC system was proposed using a genetic algorithm. For the load prediction situation, the operating capacity of each HVDC transmission system that satisfies the stable operation constraints of the multi-infeed HVDC transmission system was calculated.

Based on these results in the future, we plan to conduct an economic evaluation on the improvement of the stability of the Jeju system and changes in the operating capacity of the HVDC transmission system taking into account the starting and stopping characteristics of each generator in the Jeju area. You can review the optimal operation plan. Also, based on this, it can be used to review the operation plan of the land-Jeju Multi-Infeed HVDC transmission system and related systems.

Multi-infeed HVDC system in consideration of the system characteristics of the Jeju region as described above is based on a multi-infeed HVDC transmission system composed of two or more HVDC transmission systems. The optimal operating capacity calculation method for the efficient operation of the transmission system is presented, and the optimal operating capacity calculation algorithm is presented through this, and the optimal operating capacity for each HVDC transmission system is calculated using the calculation algorithm for the load prediction value of the future Jeju system. It has an advantage that can be presented.

The disclosed contents are only examples, and various changes can be made by those of ordinary skill in the art without departing from the gist of the claims claimed in the claims, so the scope of protection of the disclosed contents is It is not limited to the examples.

Claims (3)

Calculation step of calculating the stable operation limit capacity of the HVDC transmission system for each generator operation case based on the power supply reliability standard, MIESCR, which is a constraint on stable operation of the Jeju system and HVDC transmission system, and the system effective inertia constant standard;
A presentation step of presenting an algorithm for estimating an optimal operating capacity using a genetic algorithm in order to calculate an optimal operating capacity for each HVDC system constituting a multiple HVDC system based on the calculated value of the calculation step; And
And a calculation step of calculating an operating capacity for each HVDC transmission system that satisfies the stable operation constraint condition of the multi-unit HVDC transmission system with respect to the seasonal load prediction situation using the algorithm of the presentation step, and
Stable operation constraint MIESCR of the HVDC transmission system,
Fault capacity equation at the point where the converter is connected, and the equation of (1) below,

(One)
Equation (2) expressed as the ratio of HVDC operating capacity,

(2)
Thevenan equivalent impedance is included in the following equation (3)

(3)
here,
SCC: Fault capacity at the point where the converter is connected
SCR (Short Circuit Ratio): Ratio of AC system fault capacity to HVDC transmission capacity
ESCR (Effective Short Circuit Ratio): A parameter to consider the effect of a capacitor or filter added to the HVDC AC system.

: Converter connection bus voltage

: Equivalent impedance of the converter connection bus

: HVDC system transmission/reception power (DC Power)

: Capacity of capacitors, filters, etc. connected to the AC bus to which the HVDC system is connected
Multi-given HVDC system, characterized in that calculated as.
delete delete

Images