KR102276723B1 - Droop control method and controller for bi-directional distributed generator - Google Patents

Abstract

Disclosed are a droop control method for a bidirectional distributed power supply and an apparatus therefor. A droop control method for a bidirectional distributed power supply includes: receiving input line resistance and structure, maximum load consumption power, and maximum generated power, respectively; and controlling the droop so that the output power of the bidirectional distributed generator is within a predetermined voltage regulation range using the line resistance and structure, maximum load consumption power and maximum generated power.

Description

Droop control method and apparatus for bi-directional distributed power supply

The present invention relates to a droop control method and controller for a bidirectional distributed power supply.

As the power generation capacity of distributed generators (DG) increases worldwide, research on microgrids (hereinafter referred to as MG) to effectively use the generated power is being actively conducted. MG is a power system in which the load and DG are interconnected, and it is a small power grid with self-reliance that operates in the form of grid connection or independent operation depending on the situation. In particular, dc MG has good power quality, high power conversion efficiency and convenience of control because there is no reactive power and harmonic components compared to ac. Various control strategies have been proposed for the stable and efficient operation of dc MG. Existing control strategies can be classified into centralized control, distributed control using communication, and decentralized control.

The non-centralized control has the advantage of not requiring a communication system because it performs control only with local information, and generally uses droop control. The droop control enables autonomous power sharing by controlling the output voltage according to the increase or decrease of the output current of the DG. In droop control, the droop gain is an important parameter that affects control performance and stability, and the droop gain must be properly designed in order to properly distribute power between DGs. When configuring the dc MG line, the line resistance affects the droop gain value, so it is necessary to design the droop gain considering this.

In the case of the existing variable resistance droop control device and method, there is a problem that it cannot be applied to the microgrid that is connected to the grid because it targets the independent microgrid that controls the DC microgrid only with the energy storage device.

In addition, when distributed control is performed through bidirectional distributed power in the DC microgrid, the droop gain is affected by the line resistance, resulting in a problem that the control is not performed as originally designed.

An object of the present invention is to provide a droop control method and controller for a bidirectional distributed power supply.

Another object of the present invention is to provide a droop control method and controller for a bidirectional distributed power supply in a DC microgrid, in which the bidirectional distributed power supply can smoothly control the power current flow and maintain bus voltage regulation performance.

In addition, the present invention improves the power sharing accuracy of the distributed power supply through a droop control method and controller for a bidirectional distributed power supply considering line resistance, and at the same time, the voltage in the maximum load power consumption situation and the maximum power generation situation that can occur in the DC microgrid An object of the present invention is to provide a droop control method and controller for a bidirectional distributed power supply capable of maintaining regulating performance.

According to one aspect of the present invention, a system and apparatus for droop control for a bidirectional distributed power supply are provided.

According to an embodiment of the present invention, a first bi-directional distributed generator (BDG) and a second bi-directional distributed generator constituting the microgrid; and a droop control device for droop control so that the output powers of the first bidirectional distributed generator and the second bidirectional distributed generator are within a predetermined voltage regulation range in consideration of the line resistance of the first bidirectional distributed generator and the second bidirectional distributed generator A power control system comprising a may be provided.

The microgrid may be direct current.

The droop control device derives the power sharing ratio improvement coefficient value of the second bidirectional distributed generator based on the voltage sensitivity matrix derived using the power equation obtained by linearizing the Jacobian matrix, and the derived power sharing ratio improvement coefficient value It is possible to change the droop gain of the first or second bidirectional distributed generator.

The power sharing ratio improvement coefficient value derivation may be based on the voltage sensitivity matrix to derive the power sharing ratio improvement coefficient value in the maximum load power consumption state and the maximum power generation situation of the first or second bidirectional distributed generator, respectively.

The droop control device recalculates the voltage sensitivity matrix by reflecting the value of the power sharing factor improvement coefficient, and uses the recalculated voltage sensitivity matrix to determine the voltage fluctuation value in each bus under the maximum load and maximum power generation conditions However, the droop gain may be adjusted so that the maximum voltage fluctuation value among the voltage fluctuation values in each bus is equal to or less than the set voltage fluctuation width.

According to another embodiment of the present invention, there is provided an apparatus for controlling a droop of a bidirectional distributed generator constituting a microgrid, comprising: an input unit for receiving line resistance and structure, maximum load consumption power and maximum generated power, respectively; and a droop controller for droop control so that the output power of the bidirectional distributed generator exists within a predetermined voltage regulation range using the line resistance and structure, maximum load consumption power, and maximum generated power.

The droop controller derives a power sharing factor improvement coefficient value of the bidirectional distributed generator based on a voltage sensitivity matrix derived using a power equation obtained by linearizing a Jacobian matrix, and using the derived power sharing ratio improvement coefficient value The droop gain of the bidirectional distributed generator can be changed.

The droop controller may derive a value of a power sharing factor improvement coefficient in a maximum load power consumption state and a maximum power generation state of the bidirectional distributed generator, respectively, based on the voltage sensitivity matrix.

The droop controller recalculates the voltage sensitivity matrix by reflecting the value of the power sharing factor improvement coefficient, and uses the recalculated voltage sensitivity matrix to calculate the voltage fluctuation values in each bus under the maximum load and maximum power generation, respectively. However, the droop gain may be adjusted so that the maximum voltage fluctuation value among the voltage fluctuation values in each bus is less than or equal to the set voltage fluctuation width.

The microgrid may be direct current.

According to another aspect of the present invention, a method capable of controlling the droop of a bidirectional distributed generator in consideration of the line resistance of the microgrid is provided.

According to an embodiment of the present invention, there is provided a droop control method of a bidirectional distributed generator constituting a DC microgrid, the method comprising: receiving input line resistance and structure, maximum load consumption power, and maximum generated power, respectively; and controlling the droop so that the output power of the bidirectional distributed generator is within a predetermined voltage regulation range using the line resistance and structure, maximum load consumption power, and maximum generated power.

The step of controlling the droop includes the power sharing ratio of the bidirectional distributed generator based on a voltage sensitivity matrix derived using a power equation obtained by linearizing a Jacobian matrix based on the line resistance and structure, maximum load consumption power and maximum generated power. deriving an improvement coefficient value; and changing the droop gain of the bidirectional distributed generator using the derived power sharing factor improvement coefficient value.

The step of deriving the power sharing rate improvement coefficient value may include deriving the power sharing ratio improvement coefficient value in the maximum load power consumption state and the maximum power generation situation of the bidirectional distributed generator based on the voltage sensitivity matrix, respectively.

In the controlling of the droop, the voltage sensitivity matrix is recalculated by reflecting the power sharing factor improvement coefficient value, and the voltage change value in each bus under the maximum load and maximum power generation conditions using the recalculated voltage sensitivity matrix deriving each of the and adjusting the droop gain so that the maximum voltage fluctuation value among the voltage fluctuation values in each bus is equal to or less than a set voltage fluctuation width.

The microgrid may be direct current.

By providing a droop control method and a controller for a bidirectional distributed power supply according to an embodiment of the present invention, the bidirectional distributed power supply in the DC microgrid can smoothly control the power current flow and maintain bus voltage regulation performance.

In addition, the present invention improves the power sharing accuracy of the distributed power supply through a droop control method and controller for a bidirectional distributed power supply considering line resistance, and at the same time, the voltage in the maximum load power consumption situation and the maximum power generation situation that can occur in the DC microgrid control performance can be maintained.

)과 출력 전류(

)의 관계를 나타낸 도면.
도 4은 본 발명의 일 실시예에 따른 선로 저항을 고려한 드룹 제어 방법을 나타낸 순서도.
도 5는 본 발명의 일 실시예에 따른 드룹 제어 장치의 내부 구성을 설명하기 위해 도시한 도면.
도 6은 본 발명의 일 실시예에 따른 5-버스 그물망 선로를 구성한 실험 환경을 예시한 도면.
도 7은 도 6의 블록도.
도 8은 본 발명의 일 실시예에 따른 최대 부하 상황에 대한 실험 결과를 도시한 도면.
도 9은 본 발명의 일 실시예에 따른 최대 발전 상황에 대한 실험 결과를 도시한 도면.1 is a view showing a power control system according to an embodiment of the present invention.
FIG. 2 is a view showing a bird analysis diagram reflecting a droop bus for droop control in consideration of line resistance according to an embodiment of the present invention; FIG.
3 is an output voltage command for two BDGs with different rated capacities (

) and the output current (

) showing the relationship.
4 is a flowchart illustrating a droop control method in consideration of line resistance according to an embodiment of the present invention.
5 is a view for explaining the internal configuration of a droop control device according to an embodiment of the present invention.
6 is a diagram illustrating an experimental environment configured with a 5-bus mesh line according to an embodiment of the present invention.
Fig. 7 is a block diagram of Fig. 6;
8 is a view showing experimental results for a maximum load situation according to an embodiment of the present invention.
9 is a view showing experimental results for the maximum power generation situation according to an embodiment of the present invention.

As used herein, the singular expression includes the plural expression unless the context clearly dictates otherwise. In this specification, terms such as “consisting of” or “comprising” should not be construed as necessarily including all of the various components or various steps described in the specification, some of which components or some steps are It should be construed that it may not include, or may further include additional components or steps. In addition, terms such as "...unit" and "module" described in the specification mean a unit that processes at least one function or operation, which may be implemented as hardware or software, or a combination of hardware and software. .

In order to analyze the structural characteristics of a DC microgrid in which multiple lines and multiple distributed power sources are connected, the present invention can perform a current analysis-based voltage sensitivity analysis in which the distributed control characteristics are reflected. The present invention relates to a droop control capable of improving power sharing performance while satisfying a voltage control range under maximum load and power generation conditions based on voltage sensitivity analysis in consideration of line resistance.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a diagram illustrating a power control system according to an embodiment of the present invention.

Referring to FIG. 1 , the power control system 100 according to an embodiment of the present invention includes a first bidirectional distributed generator 110 , a second bidirectional distributed generator 120 , an nth bidirectional distributed generator 121 , and a load ( 130) and a droop control device 140 is configured.

It is assumed that the first bidirectional distributed generator 110 , the second bidirectional distributed generator 120 , and the nth bidirectional distributed generator 121 are connected through respective buses.

It should be understood that the first bidirectional distributed generator 110 and the second bidirectional distributed generator 120 according to an embodiment of the present invention constitute a DC microgrid.

In one embodiment of the present invention, the first bidirectional distributed generator 110, the second bidirectional distributed generator 120 and the DC microgrid is shown as being configured by the load, but the second bidirectional distributed generator 120 is a plurality of can

That is, the bidirectional distributed generator having the largest rated capacity among the plurality of bidirectional distributed generators constituting the DC microgrid is collectively referred to as the first bidirectional distributed generator or the main bidirectional distributed generator. The remaining bidirectional distributed generators will be collectively referred to as a second bidirectional distributed generator or a sub bidirectional distributed generator.

That is, in the following description, the second quantity "??* distributed generator should be interpreted as an n-th quantity"??* distributed generator.

The droop control device 140 is a device for controlling the droop so that the output power of the first and second bidirectional distributed generators is within a predetermined voltage regulation range in consideration of the line resistance of the DC microgrid.

)과 출력 전류(

)의 관계를 나타낸 도면이다. 이해와 설명의 편의를 도모하기 위해 도 2를 참조하여 조류 해석 모델에 대해 간략하게 설명하기로 한다. 2 is a view showing a tidal current analysis diagram reflecting a droop bus for droop control considering line resistance according to an embodiment of the present invention, and FIG. 3 is an output voltage command for two BDGs having different rated capacities (

) and the output current (

) is a diagram showing the relationship between For the convenience of understanding and explanation, the current analysis model will be briefly described with reference to FIG. 2 .

As shown in FIG. 2 , a bi-directional distributed generator (BDG: Bi-directional DG, hereinafter referred to as BDG, hereinafter referred to as BDG) may be connected to an nth (n is a natural number) bus. Although one BDG is illustrated in FIG. 2 , the BDG constituting the DC microgrid may be plural as described in FIG. 1 .

The BDG 210 may be connected in a line structure connected by two adjacent buses. In this case, droop control may be used for power burden between BDGs.

)은 수학식 1에서 보여지는 바와 같이, 출력 전류(

)가 증가함에 따라 선형적으로 감소된다. Output voltage reference by droop control technique (

) is the output current (

) decreases linearly with increasing.

은 공칭전압(Nominal voltage)를 나타내고,

는 가상 저항(virtual resistance), 즉 드룹 게인을 나타낸다. here,

represents the nominal voltage,

represents the virtual resistance, that is, the droop gain.

를 결정할 수 있다. In general, when considering the power burden according to the rated capacity of the BDG, as in Equation 2,

can be decided

는 허용 전압 변동 폭을 나타내고,

는 최소 허용 전압을 나타내며,

는 BDG의 정격용량을 나타낸다. here,

represents the allowable voltage fluctuation range,

represents the minimum allowable voltage,

indicates the rated capacity of BDG.

)과 출력 전류(

)의 관계를 나타낸다. 도 2에서

는 제1 BDG의 드룹 게인을 나타내고,

는 제2 BDG의 드룹 게인을 나타낸다. 또한,

는 제1 BDG의 정격 용량을 나타내고,

는 제2 BDG의 정격 용량을 나타낸다.

이

보다 큰 경우 수학식 2에 의해

이

보다 작으며, 제1 BDG는 더 많은 전력을 흡수 및 공급할 수 있다.3 is an output voltage command for two BDGs with different rated capacities (

) and the output current (

) represents the relationship of in Figure 2

represents the droop gain of the first BDG,

denotes the droop gain of the second BDG. Also,

represents the rated capacity of the first BDG,

denotes the rated capacity of the second BDG.

this

If greater than Equation 2

this

smaller, and the first BDG can absorb and supply more power.

In the case of an ideal DC microgrid without line resistance, accurate power distribution may be possible depending on the designed droop gain value. However, in the case of a general DC microgrid, there is a line resistance, and thus there is a problem in that power sharing and voltage regulation performance are deteriorated.

)을 나타낸 것이다. 여기서,

는 선로 저항의 등가 값을 나타낸다. Equation 3 is the rms value of the droop gain changed by the line resistance (

) is shown. here,

represents the equivalent value of the line resistance.

는 회로 해석을 통해 유도될 수 있으나, 여러 대가 환형(Ring)이나 그물망(mesh) 형태의 복잡한 선로 구성에 연계되는 경우 이를 유도하기 어려운 문제점이 있다. 이를 위해, 본 발명의 일 실시예에서는 선로 구성과 부하 및 신재생원의 연계 위치를 고려하여 허용 전압 범위를 유지함과 동시에 BDG간의 전력 분담이 이루어질 수 있도록 선로 저항을 고려한 드룹 제어 방법에 대해 도 3을 참조하여 설명하기로 한다. If it is a DC microgrid with a simple structure in which only two BDGs are connected,

can be derived through circuit analysis, but there is a problem in that it is difficult to induce this when several units are connected to a complex line configuration in the form of a ring or mesh. To this end, in one embodiment of the present invention, the droop control method considering the line resistance so that the power distribution between BDGs can be achieved while maintaining the allowable voltage range in consideration of the line configuration, the load and the linkage position of the new and renewable sources, FIG. 3 will be described with reference to .

4 is a flowchart illustrating a droop control method in consideration of line resistance according to an embodiment of the present invention.

In step 410, the droop control device 140 calculates a voltage sensitivity matrix. Voltage sensitivity analysis is a method to understand the characteristics of the entire network considering the line configuration, the droop gain of the bidirectional distributed power supply, and the maximum capacity of the load and non-dispatchable distributed generator (NDG). is an analysis method.

The voltage sensitivity matrix is calculated through the Jacobian matrix derived from the power equation of the bus in the DC microgrid.

는 수학식 2의 드룹 게인의 역수를 나타낸다. 이를 수학식으로 다시 정리하면 수학식 4와 같다.

denotes the reciprocal of the droop gain of Equation (2). If this is rearranged into Equation, Equation 4 is obtained.

이라 칭하면, 이는 수학식 5와 같이 나타낼 수 있다. The sum of the current flowing from the n-th bus to the adjacent bus and BDG

, this can be expressed as Equation (5).

Equation 5 can be generalized as Equation 6 and expressed.

)을 수학식 7과 같이 나타낼 수 있다. Here, h denotes the bus connected to the nth bus, and N denotes the total number of buses in the dc microgrid. Using Equation 6, the power equation of the nth bus (

) can be expressed as in Equation 7.

As already described above, the voltage sensitivity matrix can be derived by taking the Jacobian matrix inverse. The power equation linearized using the Jacobian matrix can be expressed as Equation (8).

는 전력 변동(에 대한 N대 1(N-by-1) 행렬을 나타내고,

는 버스전압 변동에 대한 N대 1행렬을 나타낸다. 자코비안 행렬 성분은 전력 방정식을 버스 전압에 대한 편미분으로써 얻을 수 있으며, 이에 대한 (n,m)번째 성분을 나타내면 수학식 9와 같이 나타낼 수 있다. here,

represents the N to 1 (N-by-1) matrix for the power variation

is an N-to-1 matrix for bus voltage fluctuations. The Jacobian matrix component can be obtained as a partial derivative of the power equation with respect to the bus voltage, and the (n,m)-th component can be expressed as in Equation 9.

)으로부터 제m 버스의 전압(V_m)을 편미분함으로써 획득될 수 있다. 이를 수학식 7에 적용하면 수학식 10과 같이 정리될 수 있다. That is, the (n,m)th Jacobian matrix component is the power equation (

) can be obtained by partial differentiation of the voltage (V _{m ) of the mth bus.} Applying this to Equation 7, it can be arranged as Equation 10.

은 수학식 11과 같이 간소하게 표현될 수 있다.

can be expressed simply as in Equation (11).

As shown in Equation 11, the Jacobian matrix (J matrix) can be expressed only by line resistance and droop gain. The voltage sensitivity matrix can be obtained by taking the J matrix as an inverse matrix as in Equation (12).

에 대한 선형화된

를 수학식 13과 같이 나타낼 수 있다.Using Equation 12, Equation 8 can be rearranged as Equation 13. That is, by Equation 12

linearized for

can be expressed as Equation 13.

In an embodiment of the present invention, for droop control considering line resistance, a Jacobian matrix (J) is derived through line resistance and an existing droop gain as shown in Equation 11, and the voltage sensitivity matrix (S) is calculated by taking the inverse matrix. can

In step 415 , the droop control apparatus 140 derives a value of the power burden improvement coefficient by using the voltage sensitivity matrix S.

In an embodiment of the present invention, a BDG having the largest capacity among BDGs is referred to as a main BDG, and other BDGs are referred to as sub-BDGs.

라 칭하기로 한다. 이때, 메인 BDG의 전력 변동분 대비 타겟 서브 BDG의 전력 변동분의 비율로 정의된다. 결과적으로, 서브 BDG의 드룹 게인은 메인 BDG의 드룹 게인에 기초하여 조정될 수 있다.In one embodiment of the present invention, the power burden rate improvement coefficient value of a specific BDG(x)

to be called In this case, it is defined as the ratio of the power variation of the target sub BDG to the power variation of the main BDG. As a result, the droop gain of the sub BDG can be adjusted based on the droop gain of the main BDG.

)과 최대 발전 상황(

) 두가지로 표현될 수 있다. In addition, the power burden factor improvement coefficient value is

) and the maximum development status (

) can be expressed in two ways.

If this is expressed as an equation, it is as in Equation 14.

는 최대 부하의 정격 소비 전력을 나타내고,

는 NDG의 정격 발전 전력을 나타낸다.

는 단계 310에서 계산된 S 행렬의 (n,h)성분을 나타낸다.

가 1보다 큰 경우, 이는 메인 BDG 대비 x번째 서브 BDG에 더 큰 전압 변동이 발생하는 것을 의미하며, 이는 x번째 서브 BDG가 상대적으로 큰 출력을 담당함을 의미한다. Here, the load bus indicates a bus connected to a load, and the NDG bus indicates a bus connected to the NDG. Also,

represents the rated power consumption of the maximum load,

represents the rated generated power of the NDG.

denotes the (n,h) component of the S matrix calculated in step 310 .

is greater than 1, this means that a larger voltage fluctuation occurs in the x-th sub BDG compared to the main BDG, which means that the x-th sub BDG is in charge of a relatively large output.

가 1보다 큰 경우, x번째 BDG의 드룹 게인에

를 곱하여 x번째 BDG의 드룹 게인을 증가시킨다. 이로 인해, x번째 BDG의 출력 전력이 상대적으로 감소됨으로써 전력 공유 성능이 향상될 수 있다. therefore,

is greater than 1, the droop gain of the xth BDG is

multiplies by to increase the droop gain of the x-th BDG. Due to this, the output power of the x-th BDG is relatively reduced, so that the power sharing performance may be improved.

)를 이용하여 드룹 게인을 다시 도출하고, 이를 반영하여 전압 민감도 행렬(S)를 다시 계산한다. In step 420 , the droop control device 140 sets the power burden rate improvement coefficient value (

) is used to derive the droop gain again, and the voltage sensitivity matrix (S) is calculated again by reflecting this.

)를 이용하여 다시 도출된 드룹 게인은 수학식 15와 같이 나타낼 수 있다. For example, the derived power burden improvement coefficient value (

), the droop gain derived again can be expressed as in Equation 15.

값이 결정된다. because of this

The value is determined.

The voltage sensitivity matrix S may be calculated as a maximum load and a maximum power generation situation by reflecting the newly derived droop gain.

The droop control device 140 may calculate the maximum power variation value for the maximum load and the maximum power generation situation, respectively, by using the recalculated voltage sensitivity matrix S for the maximum load and the maximum power generation situation. If this is expressed as an equation, it is expressed as Equation 16.

는 최대 부하 상황에서의 전압 민감도 행렬(S)을 나타내고,

는 최대 발전 상황에서의 전압 민감도 행렬(S)을 나타낸다. 또한,

와

는

와

을 성분으로 가지는 최대 전력 변동 행렬이고,

와

는 각각 최대 부하 및 최대 발전 상황에서의 전압 변동 행렬을 나타낸다. here,

denotes the voltage sensitivity matrix (S) under the full load situation,

denotes the voltage sensitivity matrix (S) in the maximum power generation situation. Also,

Wow

is

Wow

is the maximum power fluctuation matrix having as a component,

Wow

denotes the voltage fluctuation matrix under the maximum load and maximum power generation conditions, respectively.

는 행렬 성분 중 최대값을 찾는 함수이며, 이를 통해 변동이 가장 큰 버스의 전압값을 찾을 수 있다.

is a function to find the maximum value among the matrix components, and through this, the voltage value of the bus with the greatest fluctuation can be found.

In step 425, the droop control device 140 uses the re-calculated voltage sensitivity matrix in the maximum load and maximum power generation conditions to determine the voltage change value of the bus having the largest voltage change in the maximum load and maximum power generation conditions (hereinafter referred to as the maximum voltage change). value) is derived.

In step 430 , the droop control device 140 determines the droop gain so that the maximum voltage fluctuation value in the maximum load and maximum power generation conditions is included within the reference voltage fluctuation range.

가 기준 전압 변동 폭(

)보다 크면,

가

이내에 포함되도록

을 감소시킨 후 단계 320으로 진행한다. For example, the droop control device 140 may

A reference voltage fluctuation width (

) is greater than,

end

to be included within

After decreasing , proceed to step 320.

가

보다 작아지도록 조건을 변경하면서 드룹 게인 도출 및 전압 민감도 행렬을 도출하는 과정을 다시 반복 수행할 수 있다. 이는

에 대해서도 동일하게 적용된다. That is, the droop control device 140 is

end

The process of deriving the droop gain and deriving the voltage sensitivity matrix may be repeated again while changing the condition to be smaller. this is

The same applies to

와

를 이용하여 최종 드룹 게인을 결정한다. In step 435, the droop control device 140

Wow

to determine the final droop gain.

5 is a diagram illustrating an internal configuration of a droop control apparatus according to an embodiment of the present invention.

Referring to FIG. 5 , the droop control apparatus 140 according to an embodiment of the present invention includes an input unit 510 and a droop controller 515 .

The input unit 510 receives line resistance and structure, maximum load consumption power, and maximum generated power, respectively. That is, the input unit 510 may receive the structure and related information of the DC microgrid.

The droop controller 515 is a device for controlling droop so that the output power of the bidirectional distributed generator exists within a predetermined voltage regulation range using line resistance and structure, maximum load consumption power, and maximum generated power.

This droop controller 515 may be located in front of the internal controller of the bidirectional distributed generator, as shown in FIG. 6 . Through this, the droop controller 515 may droop control at least one of an output power and a bus voltage of the bidirectional distributed generator according to the droop gain.

Detailed functions and operations of the droop controller 515 are the same as those described with reference to FIGS. 1 to 4 , and thus a redundant description will be omitted.

6 is a diagram illustrating an experimental environment configured with a 5-bus mesh line according to an embodiment of the present invention, FIG. 7 is a block diagram of FIG. 6, and FIG. 8 is a maximum load situation according to an embodiment of the present invention. It is a diagram showing the experimental results for , and FIG. 9 is a diagram showing the experimental results for the maximum power generation situation according to an embodiment of the present invention.

Table 1 shows detailed integer values of distributed power, load, and line resistance. Table 2 shows a new droop gain derived in consideration of line resistance according to an embodiment of the present invention.

essence sign value nominal voltage Vnom 120 V bus voltage upper limit Vmax 126 V bus voltage lower limit Vmin 114 V BDG 1 rated power Prated,1 1500 W BDG 2 rated power Prated,2 750 W BDG 3 rated power Prated,3 750 W load 1 maximum power consumption load 1 1000 W load 2 resistance load 2 15 Ω load 3 resistance load 3 15 Ω NDG 1 Maximum power generation PNDG 1 1400 W NDG 2 maximum power generation PNDG 2 1000 W Line resistance between bus 1 and 2 R12 0.18 Ω Line resistance between bus 2 and 3 R23 0.22 Ω Line resistance between bus 2 and 5 R25 0.18 Ω Line resistance between bus 3 and 4 R34 0.18 Ω Line resistance between bus 4 and 5 R45 0.22 Ω Line resistance between bus 3 and 5 R35 0.3 Ω

# BDG Conventional droop gain load dominance development advantage Rd αload βload R'd αgen βgen R'd One 0.456 1.000 0.65 0.296 1.000 0.71 0.324 2 0.912 1.422 0.65 0.843 1.322 0.71 0.856 3 0.912 1.421 0.65 0.842 1.315 0.71 0.851

Referring to FIG. 8 , the left part of the waveform is the result of applying the conventional droop gain, and the right part is the result of applying the droop gain calculated through the proposed design method. It can be seen that the power sharing accuracy is improved by applying the designed droop gain. At full load, when applying the conventional droop gain, the voltages of buses 2, 3, 4, and 5 dropped below Vmin (114 V) to 113.3 V, 113.3 V, 113.1 V, and 113.7 V, respectively. When applying the droop gain derived according to an embodiment of , it can be confirmed that the voltages of all buses are equal to or greater than Vmin. 9 shows the experimental waveform for the maximum power generation situation, it can be confirmed that the power sharing accuracy is also improved. In the case of maximum power generation, when the existing droop gain is applied, the voltage of bus 4 exceeds Vmax (126V) by 126.1V, but when the designed droop gain is applied, it can be confirmed that the voltage of all buses is below Vmax. Through this, it can be confirmed that the voltage regulation ability is improved through the proposed method.

The apparatus and method according to an embodiment of the present invention may be implemented in the form of program instructions that can be executed through various computer means and recorded in a computer-readable medium. The computer-readable medium may include program instructions, data files, data structures, and the like, alone or in combination. The program instructions recorded on the computer readable medium may be specially designed and configured for the present invention, or may be known and available to those skilled in the computer software field. Examples of the computer-readable recording medium include magnetic media such as hard disks, floppy disks and magnetic tapes, optical media such as CD-ROMs and DVDs, and magnetic media such as floppy disks. - Includes magneto-optical media and hardware devices specially configured to store and execute program instructions, such as ROM, RAM, flash memory, and the like. Examples of program instructions include not only machine language codes such as those generated by a compiler, but also high-level language codes that can be executed by a computer using an interpreter or the like.

The hardware devices described above may be configured to operate as one or more software modules to perform the operations of the present invention, and vice versa.

So far, the present invention has been looked at focusing on the embodiments thereof. Those of ordinary skill in the art to which the present invention pertains will understand that the present invention can be implemented in a modified form without departing from the essential characteristics of the present invention. Therefore, the disclosed embodiments should be considered in an illustrative rather than a restrictive sense. The scope of the present invention is indicated in the claims rather than the foregoing description, and all differences within the scope equivalent thereto should be construed as being included in the present invention.

100: power control system
110: first bidirectional distributed generator
120: second bidirectional distributed generator
130: load
140: droop control device

Claims (16)

A first bi-directional distributed generator (BDG) and a plurality of second bi-directional distributed generators constituting the microgrid- The capacity of the first bi-directional distributed generator is greater than the capacity of each of the plurality of second bi-directional distributed generators or equal to; and
In consideration of the line resistance of each of the first bidirectional distributed generator and the plurality of second bidirectional distributed generators, the output power of each of the first bidirectional distributed generator and the plurality of second bidirectional distributed generators is drooped to exist within a predetermined voltage regulation range including a droop control device to control,
The droop control device,
Based on the voltage sensitivity matrix derived using the power equation obtained by linearizing the Jacobian matrix, the power sharing rate improvement coefficient value in the maximum load power consumption state and the maximum power generation situation of each of the plurality of second bidirectional distributed generators is derived, respectively, Changing the droop gain of each of the first or plurality of second bidirectional distributed generators by using the respectively derived power sharing ratio improvement coefficient value, and reflecting the power sharing ratio improvement coefficient value to recalculate the voltage sensitivity matrix, and Using the recalculated voltage sensitivity matrix, the voltage fluctuation values on each bus under the maximum load and maximum power generation are respectively derived.
The power sharing rate improvement coefficient value is the power variation value of each of the plurality of second bidirectional distributed generators compared to the power variation value of the first bidirectional distributed generator that has the largest rated capacity or is a reference among the bidirectional distributed generators constituting the microgrid be the ratio of
The droop gain of each of the plurality of second bidirectional distributed generators is multiplied by the power sharing rate improvement coefficient value for each bidirectional distributed generator to change the droop gain of each of the plurality of second bidirectional distributed generators in the plurality of second directions ?? Increases or decreases the output power of each distributed generator according to the power sharing rate improvement coefficient value for each bidirectional distributed generator,
The droop gain is adjusted so that the maximum voltage fluctuation value of each bus under the maximum load situation is less than the set voltage fluctuation range, and the maximum voltage fluctuation value among the voltage fluctuation values of each bus in the maximum power generation situation is the set voltage. Power control system, characterized in that the droop gain is adjusted to be less than the fluctuation range.
According to claim 1,
The microgrid is a power control system, characterized in that the direct current.
delete delete delete In the droop control device of a plurality of bidirectional distributed generators constituting a microgrid,
an input unit receiving line resistance and structure, maximum load consumption power, and maximum generated power, respectively; and
A droop controller for droop control so that the output power of the bidirectional distributed generator exists within a predetermined voltage regulation range using the line resistance and structure, maximum load consumption power and maximum generated power,
The droop controller is
Based on the voltage sensitivity matrix derived using the power equation obtained by linearizing the Jacobian matrix, the power sharing rate improvement coefficient value in the maximum load power consumption state and the maximum power generation situation of the bidirectional distributed generator is derived, respectively, and the derived power The droop gain of the bidirectional distributed generator is changed using the sharing ratio improvement coefficient value, the voltage sensitivity matrix is recalculated by reflecting the power sharing ratio improvement coefficient value, and the maximum load and maximum using the recalculated voltage sensitivity matrix Each bus derives the voltage fluctuation value in the power generation situation,
The plurality of bidirectional distributed generators include a first bidirectional distributed generator and a second bidirectional distributed generator, wherein the capacity of the first bidirectional distributed generator is greater than or equal to that of the second bidirectional distributed generator, wherein the second bidirectional distributed generator includes a plurality of is,
The power sharing factor improvement coefficient value is a ratio of the power variation value of the second bidirectional distributed generator to the power variation value of the first bidirectional distributed generator that has a large rated capacity or is a reference among the plurality of bidirectional distributed generators, the power sharing rate changing the droop gain by multiplying the droop gain of the second bidirectional distributed generator whose improvement coefficient value is equal to or greater than the reference value by the power sharing factor improvement coefficient value,
The droop gain is adjusted so that the maximum voltage fluctuation value of each bus under the maximum load situation is less than the set voltage fluctuation range, and the maximum voltage fluctuation value among the voltage fluctuation values of each bus in the maximum power generation situation is the set voltage. A droop control device, characterized in that the droop gain is adjusted to be less than the fluctuation range.
delete delete delete 7. The method of claim 6,
The microgrid is a droop control device, characterized in that the direct current.
In the droop control method of the bidirectional distributed generator constituting the microgrid,
receiving input of line resistance and structure, maximum load consumption power and maximum generated power, respectively; and
Controlling droop so that the output power of the bidirectional distributed generator exists within a predetermined voltage regulation range using the line resistance and structure, maximum load consumption power and maximum generated power,
The step of controlling the droop includes:
Based on the voltage sensitivity matrix derived using a power equation obtained by linearizing a Jacobian matrix based on the line resistance and structure, the maximum load consumption power and the maximum generated power, the maximum load power consumption state and the maximum generation situation of the bidirectional distributed generator deriving each of the power sharing rate improvement coefficient values in ;
changing the droop gain of the bidirectional distributed generator using the respective derived power sharing rate improvement coefficient values;
Recalculating the voltage sensitivity matrix by reflecting the respective derived power sharing factor improvement coefficient values, and using the recalculated voltage sensitivity matrix to derive voltage fluctuation values in each bus under maximum load and maximum power generation, respectively step; and
The droop gain is adjusted so that the maximum voltage fluctuation value of each bus under the maximum load situation is less than the set voltage fluctuation range, and the maximum voltage fluctuation value among the voltage fluctuation values of each bus in the maximum power generation situation is the set voltage. Including the step of adjusting the droop gain to be less than the fluctuation range,
The plurality of bidirectional distributed generators include a first bidirectional distributed generator and a second bidirectional distributed generator, wherein the capacity of the first bidirectional distributed generator is greater than that of the second bidirectional distributed generator, wherein the second bidirectional distributed generator is a plurality,
The power sharing rate improvement coefficient value is the ratio of the power variation value of the second bidirectional distributed generator to the power variation value of the first bidirectional distributed generator,
Changing the droop gain includes:
The droop control method, characterized in that the droop gain is changed by multiplying the droop gain of the second bidirectional distributed generator having the power sharing ratio improvement coefficient value equal to or greater than a reference value by the power sharing ratio improvement coefficient value.
delete delete delete 12. The method of claim 11,
The microgrid is a droop control method, characterized in that the direct current.
A computer-readable recording medium product on which a program code for performing the method according to claim 11 is recorded.

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