KR20230016736A - Open phase fault protection device and method in grid-connected transformer for ess - Google Patents

Abstract

Disclosed are an open-phase fault detection-protection device of a transformer for an energy storage system (ESS), which detects an open-phase fault by comparing currents and phases on each of primary and secondary sides of the transformer for the ESS using the concept of current comparison, and allows for quick disconnection of the ESS from the grid based on the detection; and a method thereof. The open-phase fault detection-protection device of a transformer for an ESS comprises: a first receiving unit which receives a first current sensed by a first current transformer installed on a primary side of the transformer for the ESS; a second receiving unit which receives a second current sensed by a second current transformer installed on a secondary side of the transformer for the ESS; and a detection current unit which calculates an operational slope and a current imbalance rate based on the magnitudes and phases of the first current and the second current, and determines an open-phase fault if both the operational slope and the current imbalance rate exceed predetermined setting values to operate a breaker.

Description

Phase failure detection of ESS-connected transformer - protection device and its method {OPEN PHASE FAULT PROTECTION DEVICE AND METHOD IN GRID-CONNECTED TRANSFORMER FOR ESS}

The present invention relates to a phase failure detection-protection device and method for an ESS-linked transformer, and more particularly, to an ESS-linked transformer that can quickly separate an energy storage system (ESS) from a system. It relates to an accident detection-protection device and its method.

In general, the structure of a transformer is largely composed of a winding wire and an iron core, and electrical characteristics are different depending on the wiring method of the winding and the structure of the iron core.

As for the wiring method of the transformer winding, the Y-Δ wiring method is mainly used, and in some cases, the Y-Y wiring method is used. The iron core structure of the transformer is largely divided into inner iron type and outer iron type, and inner iron type transformer is divided into triangular iron core and pentagonal iron core type.

Transformers for energy storage system (hereinafter referred to as ESS) use a triangular iron core shape, which is advantageous in terms of economic feasibility and occupied area, and the pentagonal core type is mainly used for extra-high voltage systems of 154kV or higher. On the other hand, there is a method of combining three single-phase transformers into one bank and using them as three-phase, and the electrical characteristics (voltage induction, power flow, etc.) are the same as those of the pentagonal iron core.

1 is a configuration for explaining a reverse power flow phenomenon of a general system ESS-linked transformer.

Referring to FIG. 1 , when a phase failure such as disconnection of one phase of a distribution line occurs in a distribution system to which an ESS is linked, the ESS must be separated from the system. However, due to the phenomenon of continuous power generation without detecting the phase loss accident (single operation) and the reverse flow phenomenon of the ESS-linked transformer, power may be supplied to the phase of the distribution line with phase loss and adversely affect the system.

In order to solve this problem, it is necessary to quickly separate the ESS from the system by detecting the phase loss when a phase loss occurs. However, conventionally used phase loss protection methods adopt a method of operating when the measured voltage is below the set value.

Therefore, since the phase loss protection relay of the above method can maintain the voltage of the phase loss according to the wiring method and the shape of the iron core of the ESS-linked transformer, it is difficult to detect the phase loss accident, and a new phase loss detection algorithm is required.

Republic of Korea Patent Registration No. 10-2080809 (2020. 02. 18.) (phase loss detection device and IoT-based phase loss accident remote alarm system) Republic of Korea Patent Registration No. 10-1884388 (2018. 07. 26.) (3-phase motor control panel voltage unbalance monitoring system)

Therefore, the technical problem of the present invention is focused on this point, and the purpose of the present invention is to detect phase loss based on the current size and phase of the primary and secondary sides of the ESS-linked transformer using the concept of the current comparison method Based on this, it is to provide a phase failure detection and protection device for an ESS-linked transformer that can quickly separate the ESS from the system.

Another object of the present invention is to use the concept of a current comparison method to detect a phase failure based on the current size and phase of the primary and secondary sides of the ESS-linked transformer, and to quickly separate the ESS from the system based on this It is to provide a phase failure detection and protection method for an ESS-linked transformer.

In order to realize the object of the present invention described above, the phase failure detection and protection device of the ESS-linked transformer according to an embodiment is configured to receive a first current sensed by a first current transformer installed on the primary side of the ESS-linked transformer. a first receiver; a second receiving unit receiving a second current sensed by a second current transformer installed on a secondary side of the ESS-linked transformer; And calculating an operation slope and a current unbalance rate based on the magnitude and phase of each of the first current and the second current, and when both the operation slope and the current unbalance rate are equal to or greater than a set value, it is determined that a phase failure occurs and the circuit breaker is operated. It includes a detection control unit that

In one embodiment, the detection control unit may include: an upper unit for assuming a transformer ratio, a transformer ratio, and each displacement and capacity of the ESS-linked transformer; Operation area determination unit for determining the operating area on the operating curve of the phase loss detection-protection device of the ESS linkage transformer by calculating the minimum operating current, knee point, operating slope, and current unbalance rate, which are the correct values of the phase loss detection-protection device ; a calculation unit that calculates an operating current and a limiting current of each phase based on the magnitude and phase of each of the first current and the second current; an operating range determination unit for determining whether the operating current and limit current of each phase are included in the operating range; a current imbalance rate judging unit calculating a current imbalance rate when it is checked that the operating current and the limit current are included in the operating range, and determining whether the current imbalance rate is greater than or equal to a set value; And when it is checked that the current imbalance rate is greater than or equal to a set value, it may include an operation control unit that determines a phase loss accident and operates a protection device.

및

(여기서,

: 동작전류,

: 제한전류,

: 변압기 1차측의 전류,

: 변압기 2차측의 전류)에 대입하여 각 상의 동작전류(

)와 제한전류(

)를 계산하고, 상기 전류 불평형률 판단부는,

(여기서,

: 변압기 1차측 전류 불평형률,

: 변압기 1차측의 a상 전류,

: 변압기 1차측의 b상 전류,

: 변압기 1차측의 c상 전류)에 따라 전류 불평형률을 계산할 수 있다. In one embodiment, the calculation unit, the measured current magnitude and phase

and

(here,

: operating current,

: limiting current,

: Current of the primary side of the transformer,

: operating current of each phase by substituting the current of the secondary side of the transformer) (

) and limiting current (

), and the current unbalance rate determining unit,

(here,

: Transformer primary side current unbalance factor,

: Phase a current of the primary side of the transformer,

: Phase b current of the primary side of the transformer,

: The current unbalance factor can be calculated according to the c-phase current of the primary side of the transformer).

In order to realize the other object of the present invention described above, a phase failure detection-protection method of an ESS-linked transformer according to an embodiment is, (a) a first sensed by a first current transformer installed on the primary side of an ESS-linked transformer receiving current; (b) receiving a second current sensed by a second current transformer installed on a secondary side of the ESS-linked transformer; And (c) calculating an operating slope and a current unbalance rate based on the first current and the second current, and determining that a phase failure occurs when both the operating slope and the current unbalance rate are equal to or greater than a set value, and operating a circuit breaker. includes

및

(여기서,

: 동작전류,

: 제한전류,

: 변압기 1차측의 전류,

: 변압기 2차측의 전류)에 대입하여 각 상의 동작전류(

)와 제한전류(

)를 계산하는 단계; (c-4) 상기 각 상의 동작전류(

)와 제한전류(

)에 대하여 상기 동작범위에 포함되는가를 판단하는 단계; (c-5) 상기 단계(c-4)에서 상기 동작전류 및 상기 제한전류가 상기 동작범위에 포함되지 않는 것으로 체크되면, 상기 단계(c-3)로 피드백하는 단계; (c-6) 상기 단계(c-4)에서 상기 동작전류 및 상기 제한전류가 상기 동작범위에 포함되는 것으로 체크되면,

(여기서,

: 변압기 1차측 전류 불평형률,

: 변압기 1차측의 a상 전류,

: 변압기 1차측의 b상 전류,

: 변압기 1차측의 c상 전류)에 따라 전류 불평형률을 계산하고, 상기 전류 불평형률이 정정치 이상인지를 판단하는 단계; 및 (c-7) 상기 단계(c-6)에서 상기 전류 불평형률이 정정치 이상인 것으로 체크되면, 결상사고로 판단하여 차단기를 동작시키는 단계를 포함할 수 있다. In one embodiment, the step (c) may include (c-1) assuming a transformer ratio, a transformer ratio, each displacement and capacity of the ESS-linked transformer; (c-2) Calculate the minimum operating current, knee point, operating slope, and current unbalance rate, which are the fixed values of the phase loss detection-protection device, to determine the operating area on the operating curve of the phase loss detection-protection device of the ESS-linked transformer doing; (c-3) the current magnitude and phase of each of the first current and the second current

and

(here,

: operating current,

: limiting current,

: Current of the primary side of the transformer,

: operating current of each phase by substituting the current of the secondary side of the transformer) (

) and limiting current (

); (c-4) The operating current of each phase (

) and limiting current (

) determining whether it is included in the operating range; (c-5) feeding back to step (c-3) if it is checked in step (c-4) that the operating current and the limit current are not included in the operating range; (c-6) If it is checked in step (c-4) that the operating current and the limiting current are included in the operating range,

(here,

: Transformer primary side current unbalance factor,

: Phase a current of the primary side of the transformer,

: Phase b current of the primary side of the transformer,

: Calculating a current unbalance rate according to the c-phase current of the primary side of the transformer), and determining whether the current unbalance rate is equal to or greater than a set value; and (c-7) if it is checked that the current unbalance ratio is greater than or equal to a set value in the step (c-6), determining a phase loss accident and operating a circuit breaker.

According to the phase failure detection-protection device and method of the ESS-linked transformer, the operating slope and current unbalance are based on the current size and phase of the primary and secondary sides of the ESS-linked transformer using the concept of a current comparison method. The ESS can be quickly separated from the system by calculating the operating slope and operating the circuit breaker by calculating the operating slope and determining that it is a phase failure when both the current unbalance rate is equal to or greater than the set value.

1 is a configuration for explaining a reverse power flow phenomenon of a general system ESS-linked transformer.
2 is a conceptual diagram for explaining primary-side current and secondary-side current of an ESS-linked transformer.
Figure 3 is a conceptual diagram for explaining the installation of the image failure detection-protection device according to the present invention.
Figure 4 is a graph for explaining the operation curve of the image failure detection-protection device.
5 is a flow chart for explaining a method of operating a phase failure detection-protection device.
6 is a wiring diagram for explaining modeling of a current controller for an ESS.
7A and 7B are connection diagrams for explaining modeling of a current controller for an ESS.
8 is a wiring diagram for explaining PWM controller modeling for ESS.
9 is a wiring diagram for explaining PCS modeling for ESS.
10 is a wiring diagram for explaining the modeling of the image failure detection-protection device.
11 is a wiring diagram for explaining modeling of the entire system.
12a is a connection diagram for explaining a phase loss detection and protection device for a YY connection transformer, and FIG. 12b is a connection diagram for explaining a phase loss detection and protection device for a Y-Δ connection transformer.
13a is a waveform diagram for explaining voltage characteristics of a YY-connected ESS-connected transformer, and FIG. 13b is a waveform diagram for explaining current characteristics of a YY-connected ESS-connected transformer.

Hereinafter, with reference to the accompanying drawings, the present invention will be described in more detail. Since the present invention may have various changes and various forms, specific embodiments are illustrated in the drawings and described in detail in the text. However, it should be understood that this is not intended to limit the present invention to the specific disclosed form, and includes all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

Like reference numerals have been used for like elements throughout the description of each figure. In the accompanying drawings, the dimensions of the structures are shown enlarged than actual for clarity of the present invention.

Terms such as first and second may be used to describe various components, but the components should not be limited by the terms. These terms are only used for the purpose of distinguishing one component from another. For example, a first element may be termed a second element, and similarly, a second element may be termed a first element, without departing from the scope of the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise.

In this application, terms such as "comprise" or "have" are intended to designate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, but one or more other features It should be understood that it does not preclude the possibility of the presence or addition of numbers, steps, operations, components, parts, or combinations thereof.

In addition, unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related art, and unless explicitly defined in the present application, they should not be interpreted in an ideal or excessively formal meaning. don't

2 is a conceptual diagram for explaining primary-side current and secondary-side current of an ESS-linked transformer.

)와 2차측 전류(

)는 항상 동일한 값을 가진다. Referring to FIG. 2, in the normal state, the primary side current of the ESS-linked transformer (TR)

) and the secondary current (

) always has the same value.

), 2차측 전류(

)는 그 값이 서로 달라지게 된다. 따라서, ESS 연계용변압기(TR)의 1차측 전류(

)와 2차측 전류(

)를 비교하는 전류비교방식을 이용하면 기존방식에서 검출하기 어려운 결상사고를 판단할 수 있다. However, due to the single operation of the PCS for ESS and the reverse current of the transformer (TR) for ESS connection in the event of a phase failure, the primary side current (

), the secondary current (

) will have different values. Therefore, the primary side current of the ESS-linked transformer (TR)

) and the secondary current (

), it is possible to determine phase loss accidents that are difficult to detect in the existing method.

Figure 3 is a conceptual diagram for explaining the installation of the image failure detection-protection device according to the present invention.

Referring to FIG. 3, the settlement accident detection-protection device 100 according to the present invention uses the concept of a current comparison method, and the first current transformer CT1 (CT1) disposed on the primary side of the ESS-linked transformer (TR) 10) and the second current transformer (CT2) 20 disposed on the secondary side of the ESS-linked transformer (TR), respectively, to detect phase loss by comparing current and phase.

Specifically, the settlement accident detection-protection device 100 includes a first receiving unit 110, a second receiving unit 120 and a detection control unit 130.

)를 수신하여 검출 제어부(130)에 제공한다. The first receiver 110 receives the primary side current (or first current) sensed by the first current transformer 10 installed on the primary side of the ESS-linked transformer (TR) (

) is received and provided to the detection control unit 130.

)를 수신하여 검출 제어부(130)에 제공한다. The second receiver 120 receives the secondary current (or second current) sensed by the second current transformer 20 installed on the secondary side of the ESS-linked transformer (TR) (

) is received and provided to the detection control unit 130.

)와 제2 전류(

) 각각의 크기 및 위상에 기초하여 동작 기울기와 전류 불평형률을 계산하고, 상기 동작 기울기 및 상기 전류 불평형률 모두가 정정치 이상인 경우 결상사고로 판단하여 차단기를 동작시킨다. 예를 들어, 검출 제어부(130)는 상정부(도면부호 미부여), 동작 영역 결정부(도면부호 미부여), 계산부(도면부호 미부여), 동작범위 판단부(도면부호 미부여), 전류 불평형률 판단부(도면부호 미부여) 및 동작 제어부(도면부호 미부여)를 포함할 수 있다. 여기서, 검출 제어부(130)는 상정부, 동작 영역 결정부, 계산부, 동작범위 판단부, 전류 불평형률 판단부 및 동작 제어부로 구성된 것으로 설명하였으나 이는 논리적으로 구분하였을 뿐 하드웨어적으로 구분한 것은 아니다. The detection control unit 130 is a first current (

) and the second current (

) Calculate an operating slope and a current unbalance rate based on each magnitude and phase, and when both the operating slope and the current unbalance rate are equal to or greater than a set value, it is determined as a phase failure and the circuit breaker is operated. For example, the detection control unit 130 may include an upper unit (reference numerals not assigned), an operating area determination unit (reference numerals not assigned), a calculation unit (reference numerals not assigned), an operating range determination unit (reference numerals not assigned), It may include a current unbalance rate determining unit (reference numerals not assigned) and an operation control unit (reference numerals not assigned). Here, the detection control unit 130 has been described as being composed of an upper unit, an operating range determining unit, a calculating unit, an operating range determining unit, a current unbalance rate determining unit, and an operation controlling unit, but these are logically classified and not hardware-based. .

) 및 상기 제2 전류(

) 각각의 전류 크기 및 위상에 기초하여 각 상의 동작전류와 제한전류를 계산한다. 상기 동작범위 판단부는 상기 각 상의 동작전류와 제한전류에 대하여 상기 동작범위에 포함되는가를 판단한다. 상기 전류 불평형률 판단부는 상기 동작전류 및 상기 제한전류가 상기 동작범위에 포함되는 것으로 체크되면 전류 불평형률을 계산하고, 상기 전류 불평형률이 정정치 이상인지를 판단한다. 상기 동작 제어부는 상기 전류 불평형률이 정정치 이상인 것으로 체크되면, 결상사고로 판단하여 보호장치를 동작시킨다. The assumption unit assumes a transformer ratio, transformer ratio, angular displacement, and capacity of the ESS-linked transformer. The operating area determination unit calculates the minimum operating current, knee point, operating slope, and current unbalance rate, which are the correct values of the phase loss detection and protection device, and determines the operation area on the operation curve of the phase failure detection and protection device of the ESS-linked transformer do. The calculation unit includes the first current (

) And the second current (

) Calculate the operating current and limiting current of each phase based on the size and phase of each current. The operating range determination unit determines whether the operating current and limit current of each phase are included in the operating range. The current imbalance rate determining unit calculates a current imbalance rate when it is checked that the operating current and the limit current are included in the operating range, and determines whether the current unbalance rate is greater than or equal to a set value. When the operation control unit checks that the current unbalance rate is greater than or equal to a set value, it determines that a phase loss accident occurs and operates a protection device.

The settlement accident detection-protection device 100 shows the image loss accident detection algorithm in detail as follows.

) 및 2차측 전류(

)를 측정하고, 수식 (1)과 수식 (2)를 이용하여 동작전류(

)와 제한전류(

)를 계산한 후, 수식 (3)을 이용하여 동작 기울기(Operating Slope)(

)를 구한다.First, the primary side current of the ESS-linked transformer (TR)

) and the secondary current (

), and using Equation (1) and Equation (2), the operating current (

) and limiting current (

) After calculating the operating slope (Operating Slope) using Equation (3)

) is obtained.

(1)

(One)

(2)

(2)

(3)

(3)

: 동작전류,

: 제한전류,

: 변압기 1차측의 전류,

: 변압기 2차측의 전류,

: 동작 기울기)(here,

: operating current,

: limiting current,

: Current of the primary side of the transformer,

: current on the secondary side of the transformer,

: motion tilt)

), 제한전류(

) 및 동작 기울기(

)를 바탕으로 결상사고 검출-보호장치(100)의 동작범위를 나타내면 도 4와 같다. The operating current calculated through Equations (1) to Equations (3) (

), limiting current (

) and motion gradient (

Based on ), the operating range of the phase failure detection-protection device 100 is shown in FIG. 4.

Figure 4 is a graph for explaining the operation curve of the image failure detection-protection device.

)를 설정하는 영역을 나타내고, ② 구간은 결상사고 시, 역조류 현상으로 인해 발생하는 ESS 연계용변압기의 1차 및 2차측 전류의 차를 고려하여 결상을 검출하기 위한 기울기(

) 설정 영역을 나타낸다. 또한, ③ 구간은 계기용 변류기 포화특성을 고려하여 무릎점(knee point,

)을 상정하여 포화 시 발생하는 변류기 측정 오차를 고려하여 보호장치가 오동작하지 않도록 기울기(

)를 보정하는 영역을 나타낸다. In FIG. 4, section ① is the minimum operating current (to prevent malfunction due to measurement error in a steady state)

), and ② section is a slope for detecting phase loss in consideration of the difference between the primary and secondary currents of the ESS-linked transformer that occurs due to the reverse current phenomenon in the event of a phase loss accident (

) indicates the setting area. In addition, section ③ is the knee point (knee point,

) is assumed, and the slope (

) represents the area to be corrected.

미만에서 계산되고, ② 구간은 아래의 수식 (5)와 같이 제한전류가

이상이고, 동시에 무릎점(

) 미만에서 계산되며, ③ 구간은 아래의 수식 (6)과 같이 제한전류가 무릎점(

) 이상에서 결정된다. Therefore, in section ①, the limit current is 0 or more as shown in Equation (4) below, and at the same time

It is calculated from less than, and the limit current is calculated in ② section as shown in Equation (5) below.

above, and at the same time the knee point (

), and in section ③, the limit current is the knee point (as shown in Equation (6) below)

) is determined from above.

(

) (4)

(

) (4)

(

) (5)

(

) (5)

(

) (6)

(

) (6)

: 동작전류,

: 제한전류,

: 최소 동작전류의 설정값,

: 기울기 설정값,

: 무릎점)(here,

: operating current,

: limiting current,

: set value of minimum operating current,

: slope setting value,

: knee point)

,

)를 바탕으로 결상사고 검출 알고리즘에 의하여 도 4에 도시된 동작 곡선에서 어느 한 좌표가 결정되고, 상기 결정된 좌표가 결상사고 검출-보호장치에서 정정한 동작영역에 위치하면, 결상사고로 판단하게 된다. That is, the transformer primary and secondary current (

,

) Based on the phase loss detection algorithm, a coordinate is determined in the operation curve shown in FIG. 4, and if the determined coordinate is located in the operation area corrected by the phase loss detection-protection device, it is determined as a phase loss accident. .

)의 불평형률을 아래의 수식 (7)과 같이 계산하고, 상기 계산된 변압기 1차측 전류(

)의 불평형률이 정정치 이상일 경우에만 결상사고로 판단하여, 결상사고 검출-보호장치를 동작시킨다. On the other hand, in order to prevent malfunction due to an external ground fault, the primary side current of the transformer (

) is calculated as in Equation (7) below, and the calculated primary side current of the transformer (

) is judged to be a phase loss accident only when the unbalance rate of the phase is greater than the set value, and the phase loss detection and protection device is operated.

(7)

(7)

: 변압기 1차측 전류 불평형률,

: 변압기 1차측의 a상 전류,

: 변압기 1차측의 b상 전류,

: 변압기 1차측의 c상 전류)(here,

: Transformer primary side current unbalance factor,

: Phase a current of the primary side of the transformer,

: Phase b current of the primary side of the transformer,

: Phase c current of the primary side of the transformer)

배를 곱하여 계산해야 한다.On the other hand, the ESS-linked transformer has a 30° phase difference between the primary side and the secondary side depending on the wiring method (e.g., Y-Δ, △-Y), so the phase angle must be corrected. The size of the differential current must also be considered. That is, if the angular displacement of the ESS-linked transformer is YNd1 and the transformation ratio is 380/220 [V], the phase angle is different from the primary by 30° on the secondary side, so +30° is corrected on the secondary side to In the same way, since the secondary current is √3 times greater than the primary current, the magnitude of the current is equal to the secondary current

It must be multiplied by a factor of two.

According to the above phase loss detection algorithm, the operation method of the phase loss detection-protection device can be expressed as follows.

5 is a flow chart for explaining a method of operating a phase failure detection-protection device.

Referring to FIG. 5, an input value is set to the phase loss detection and protection device (step S102). The input value may include a transformer ratio, transformer ratio, angular displacement, and capacity of the ESS-linked transformer.

Subsequently, an operation area of the image loss detection and protection device is determined (step S104).

Subsequently, a pick-up value (or correction value) of the current unbalance ratio is set (step S106).

Subsequently, initialization is performed by setting time t to zero (step S108).

Next, the primary side and secondary side currents of the transformer are measured (step S110).

)와 제한전류(

)를 계산한다(단계 S112). 예를 들어, 측정된 1차측 전류 및 2차측 전류를 수식 (1) 내지 수식 (2)에 대입하여, 각 상의 동작전류(

)와 제한전류(

)를 계산한다.Then, based on the measured primary current and secondary current, the operating current (

) and limiting current (

) is calculated (step S112). For example, by substituting the measured primary current and secondary current into Equations (1) to Equations (2), the operating current of each phase (

) and limiting current (

) is calculated.

)와 제한전류(

)가 픽업값보다 큰지의 여부를 체크한다(단계 S114). Then, the operating current calculated in step S112 (

) and limiting current (

) is greater than the pickup value (step S114).

)와 제한전류(

)가 픽업값보다 크지 않은 것으로 체크되면 시간을 설정된 크기(Δ)만큼 증가시킨 후(단계 S116), 단계 S108로 피드백한다. In step S114, the operating current (

) and limiting current (

) is not larger than the pick-up value, the time is increased by the set size (Δ) (step S116), and then fed back to step S108.

)와 제한전류(

)가 픽업값보다 큰 것으로 체크되면 전류 불평형률이 픽업값보다 큰지의 여부를 체크한다(단계 S118). In step S114, the operating current (

) and limiting current (

) is greater than the pickup value, it is checked whether the current unbalance rate is greater than the pickup value (step S118).

If it is checked in step S118 that the current unbalance rate is not greater than the pick-up value, it is checked whether the current time is the set maximum time (step S120).

In step S120, if it is checked that the current time is the set maximum time, the process ends, and if it is checked that the current time is not the set maximum time, the process is fed back to step S116.

On the other hand, if it is checked that the current unbalance rate is greater than the pick-up value, the protection device is operated (step S122).

Hereinafter, modeling of the phase failure detection-protection device by the power system analysis software (PSCAD/EMTDC) will be described.

<Detection of phase loss accident of ESS-linked transformer - Modeling of protection device>

In order to analyze the operation characteristics of the protection device for each iron core structure and wiring method of the ESS-linked transformer in the distribution system linked to the ESS, modeling using power system analysis software (PSCAD/EMTDC), a distribution system commercial analysis program, is shown in FIG. 6 and same.

6 is a wiring diagram for explaining modeling of a current controller for an ESS.

Referring to FIG. 6, a phase loss state in which phase A of the distribution line is disconnected is simulated by a circuit breaker (CB, circuit breaker), and it is shown that three-phase loads are connected to the primary distribution line of the ESS-linked transformer. In addition, the ESS-linked transformer uses the UMEC (unified magnetic equivalent circuit) model provided by the library of power system analysis software (PSCAD/EMTDC). In the above model, it can be analyzed by changing the wiring method to Y-Y type or Y-Δ type with a three-phase two-winding transformer, and the iron core structure can be analyzed by changing the shape of a triangular core, a pentagonal core, and a single-phase transformer.

<ESS modeling>

In order to control the active power and reactive power targeted for the PCS for ESS, the detailed current control algorithm using the PI controller is as shown in Equations (8) and Equation (9) below, and modeling the PI controller is shown in FIG. 7a and as shown in FIG. 7B. Here, since the current controller of the PCS is a decoupling circuit and active power, it can control reactive power independently of each other.

(8)

(8)

(9)

(9)

,

: PCS의 출력을 위한 d-q축 전압,

: PCS 출력의 기준전류,

,

: d-q동기좌표계에 의한 계통 전류(직류),

: 계통의 순시전압)(here,

,

: dq axis voltage for output of PCS,

: Reference current of PCS output,

,

: System current (direct current) by dq synchronous coordinate system,

: instantaneous voltage of grid)

7A and 7B are connection diagrams for explaining modeling of a current controller for an ESS.

와

는 d-q 좌표변환을 통해 3상의 전압으로 변환되며, IGBT를 구동시키기 위한 6개의 신호로 사용되는 PWM을 모델링하면, 도 8과 같이 나타낼 수 있다. obtained from the above formulas (8) and (9)

and

is converted into a three-phase voltage through dq coordinate conversion, and can be represented as shown in FIG. 8 when modeling PWM used as six signals for driving an IGBT.

8 is a wiring diagram for explaining PWM controller modeling for ESS.

Meanwhile, modeling of the PCS for ESS that performs the above control is as shown in FIG. 9 .

9 is a wiring diagram for explaining PCS modeling for ESS.

Referring to FIG. 9 , the DC output generated by the ESS is converted into a three-phase AC output having a phase difference of 120° by means of six switching signals from the PWM.

<Separation Accident Detection-Protection Device Modeling>

When a phase loss accident occurs, modeling a phase loss detection-protection device capable of detecting it can be represented as shown in FIG. 10 .

10 is a wiring diagram for explaining the modeling of the image failure detection-protection device.

Referring to FIG. 10, part A represents the phase failure detection operation curve calculated by Equations (1) to Equation (6), and it is determined whether it corresponds to the operation region by calculating the operating current and the limiting current. In addition, part B calculates the unbalance ratio of the current in the primary side of the transformer according to Equation (7) to prevent malfunction of the protection device due to external ground faults, and determines whether it exceeds the set value. On the other hand, when part C satisfies both conditions of A and B, it transfers an operation signal to the phase loss detection and protection device.

<Full system modeling>

Modeling the entire system based on the above information is shown in FIG. 11 .

11 is a wiring diagram for explaining modeling of the entire system.

In FIG. 11, part A represents a switchgear, part B represents a low voltage distribution line and load, part C represents a transformer for linking an ESS, and part D represents an ESS and a phase loss detection-protection device.

Hereinafter, in the case of a phase loss accident in which one phase is disconnected in the distribution system connected to the ESS, in order to confirm that the phase loss detection algorithm proposed in the present invention is useful for phase loss protection for each wiring method and iron core structure of the ESS-linked transformer, As shown in Fig. 12, an abbreviated distribution system composed of a battery, a PCS, a transformer connected to an ESS, and a customer load and a phase failure detection and protection device connected to the distribution system are implemented.

12A is a connection diagram for explaining a phase loss detection and protection device for a Y-Y connection transformer, and FIG. 12B is a connection diagram for explaining a phase loss detection and protection device for a Y-Δ connection transformer.

Referring to FIGS. 12A and 12B, the abbreviated distribution system uses a 3-phase 4-wire 380/220V power source, and is composed of a transformer for ESS connection, a CB for phase failure test, and a resistive load.

The turns ratio of the ESS-linked transformer is 1:1, and the transformer iron core is composed of a pentagonal iron core transformer consisting of three three-phase triangular iron cores of 3 [kVA] and three single-phase transformers of 1 [kVA].

In addition, in order to check the operating characteristics of the phase failure detection-protection device due to power flow during phase loss, a resistive load of 2,400W (800W × 3) is connected to the primary side of the transformer.

In addition, the phase loss detection-protection device is connected between measurement points 1 and 2 at both ends of the transformer to measure the magnitude and phase of voltage and current, and after generating a phase loss accident in the phase loss test CB, the phase loss detection-protection device Check the operating characteristics.

In order to evaluate the phase failure detection algorithm of the ESS-linked transformer proposed in the present invention, the test parameters and conditions of the ESS-linked transformer and each component are assumed as shown in Tables 1 and 2.

Table 1 shows the load capacities and transformer parameters.

[Table 1]

Table 1 shows the ESS-linked transformer and load capacity parameters. Three-phase 3kVA transformers with triangular core and five-triangle core structure are used, and single-phase transformers are composed of three 1kVA three-phase connections.

Table 2 shows the setting conditions of the phase failure detection-protection device.

[Table 2]

Table 2 shows the setting conditions of the phase failure detection-protection device, and the transformer ratio is 380/380[V] in the case of Y-Y connection and 380/220[V] in case of Y-Δ connection, and the operation slope and primary current unbalance The rate is set at 30[%]. In addition, the phase loss accident is assumed to be a case where phase A is disconnected, and a resistance load of 2,400W (800W × 3) is connected to each phase on the primary side of the ESS-linked transformer.

Hereinafter, phase failure detection-protection device characteristics analysis by power system analysis software (PSCAD/EMTDC) will be described.

<Analysis of protection device characteristics of Y-Y connection transformer>

When the ESS-linked transformer is Y-Y-connected according to the modeling of the power system analysis software (PSCAD/EMTDC), the characteristics of the phase failure detection-protection device in a state in which the primary A-phase of the ESS-linked transformer is disconnected are shown in FIG. 13a and FIG. 13b, Table 3 and Table 4.

Figure 13a is a waveform diagram for explaining the voltage characteristics of the Y-Y connection ESS connection transformer, Figure 13b is a waveform diagram for explaining the current characteristics of the Y-Y connection ESS connection transformer.

Table 3 shows the voltage characteristics of the phase failure detection-protection device of the Y-Y connection ESS-linked transformer.

[Table 3]

Here, FIG. 13a and Table 3 analyze the voltage characteristics in the event of a phase loss accident. When the transformer is a triangular iron core, the primary and secondary voltages of the phase A phase are 219 [V] and 220 [V], respectively. In the case of a pentagonal iron core and a single-phase transformer, it can be seen that both the primary and secondary voltages are not induced. Therefore, in the case of disconnection in the pentagonal core and single-phase transformer of the Y-Y connection, the voltage of the phase loss is measured as 0 [V], so it can be detected by the existing phase loss protection method. It can be seen that detection is impossible.

Table 4 shows the operating characteristics of the phase failure detection-protection device of the Y-Y connection ESS-linked transformer.

[Table 4]

On the other hand, Figure 13b and Table 4 are the analysis of the operating characteristics of the phase loss detection-protection device, in the case of a triangular iron core transformer, a current of 3.6∠-3 ° [A] is supplied to the phase A phase loss, but 5 It can be seen that no current is supplied to each iron core and single-phase transformer.

That is, it can be seen that the phase loss phase is supplied by adding the current supplied by the PCS for ESS and the current in the form of reverse current supplied from B and C phases in the normal state to A phase.

In addition, in the case of triangular iron core, the operation slope is 33.6 [%] of A phase, 50 [%] of B phase, and 51 [%] of C phase, and the primary current unbalance rate is 87 [%], so both conditions are protective devices. Exceeding the correction value (30 [%]) of , it can be seen that according to the proposed phase loss accident detection algorithm, the protection device operates by determining a phase loss accident.

Therefore, it can be seen that the Y-Y connection pentagonal core and single-phase transformer type adopts the existing phase loss accident protection method, and the triangular iron core transformer must detect the phase loss accident according to the proposed phase loss detection algorithm.

In addition, if an appropriate phase loss detection and protection device is not installed according to the wiring method and iron core structure of the ESS-linked transformer, if a disconnection accident occurs, the phase loss cannot be detected and the PCS operates alone, which may adversely affect the system. can know

<Analysis of protection device characteristics of Y-Δ connection transformer>

When the ESS-linked transformer is Y-Δ connection, Tables 5 and 6 show the characteristics of the phase failure detection-protection device in a state where the primary side A phase of the ESS-linked transformer is disconnected.

Table 5 shows the voltage characteristics of the phase failure detection-protection device of the Y-Δ connection ESS-linked transformer.

[Table 5]

Referring to Table 5, the voltage characteristics in the event of a phase loss accident are analyzed. Regardless of the iron core structure of the ESS-linked transformer, the primary and secondary voltages of phase A in all transformers are 216 [V] to 219 [V] It can be seen that is organic.

Therefore, in the case of disconnection in the ESS-linked transformer of Y-Δ connection, it can be seen that it is impossible to detect with the existing phase loss accident protection method because the voltage is induced in the phase loss regardless of the iron core structure.

Table 6 shows the operating characteristics of the phase failure detection-protection device of the Y-Δ connection ESS-linked transformer.

[Table 6]

Referring to Table 6, the operation characteristics of the phase loss detection-protection device are analyzed. In the case of a triangular iron core transformer, a current of 3.63∠-3°[A] is supplied to the phase A phase with phase loss, and a pentagonal iron core And in the single-phase transformer, it can be seen that a current of 3.61 ∠ -3 ° [A] is supplied to the phase A phase. In addition, in all iron core structures, the operating slope and primary current unbalance rate exceed the correction value (30 [%]) of the protection device, so it can be seen that the protection device operates by judging it as a phase loss accident according to the proposed phase loss detection algorithm. there is.

Therefore, it can be seen that the Y-Δ connection should detect the image loss accident according to the proposed image loss detection algorithm regardless of the iron core structure. In addition, if an appropriate phase loss detection and protection device is not installed according to the wiring method and iron core structure of the ESS-linked transformer, if a disconnection accident occurs, the phase loss cannot be detected and the PCS operates alone, which may adversely affect the system. can know

<Analysis of protection device characteristics of Y-Y connection transformer>

Tables 7 and 8 show the operating characteristics of the phase loss detection and protection device when the primary side A phase of the ESS linkage transformer is disconnected by the above-described phase loss detection and protection device.

Table 7 shows the voltage characteristics of the phase failure detection-protection device of the Y-Y connection ESS-linked transformer.

[Table 7]

Referring to Table 7, the voltage characteristics in the event of a phase loss accident are analyzed. In the case of a pentagonal iron core and a single-phase transformer, both the primary and secondary side voltages are not induced, so it can be seen that the results are almost similar to the simulation results described later.

Table 8 shows the operating characteristics of the phase failure detection-protection device of the Y-Y connection ESS-linked transformer.

[Table 8]

Referring to Table 8, the operation characteristics of the phase loss detection-protection device are analyzed. In the case of a triangular iron core, a current of 3.17∠-2°[A] is supplied to the phase A phase, but a pentagonal core and a single phase It can be seen that no current is supplied from the transformer. Here, in the case of triangular iron core, the operation slope is 37.1 [%] of A phase, 54.5 [%] of B phase, and 41.9 [%] of C phase, and the primary current unbalance rate is 92 [%], so both conditions are of protection device According to the phase loss detection algorithm proposed by exceeding the correction value (30 [%]), it can be seen that the protection device operates by determining a phase loss accident.

Therefore, when the ESS-linked transformer is Y-Y connected, characteristics similar to the simulation results were confirmed, and the effectiveness of the phase failure detection and protection device proposed in the present invention was confirmed.

<Analysis of protection device characteristics of Y-Δ connection transformer>

Tables 9 and 10 show the operating characteristics of the phase loss detection and protection device when the primary side A phase of the ESS-linked transformer is disconnected.

Table 9 shows the voltage characteristics of the phase failure detection-protection device of the Y-Δ connection ESS-linked transformer.

[Table 9]

Referring to Table 9, the voltage characteristics in the event of a phase loss accident are analyzed. Regardless of the iron core structure of the ESS-linked transformer, the primary and secondary voltages of phase A in all transformers are 206 [V] to 216 [V] It can be seen that is induced and is almost similar to the simulation result described later.

Table 10 shows the operating characteristics of the phase failure detection-protection device of the Y-Δ connection ESS-linked transformer.

[Table 10]

Referring to Table 10, the operation characteristics of the phase failure detection-protection device are analyzed. In the case of a triangular iron core, a current of 3.17∠1°[A] is supplied to the phase A of phase loss, and a pentagonal iron core and a single-phase transformer , it can be seen that a current of 3.21∠1°[A] is supplied to the A phase that is phase disconnected. In addition, in all iron core structures, the operating slope and primary current unbalance rate exceed the correction value (30 [%]) of the protection device, so it can be seen that the protection device operates by judging it as a phase loss accident according to the proposed phase loss detection algorithm. there is. Therefore, when the ESS-linked transformer is Y-Δ connection, similar characteristics to the simulation results were confirmed, and the effectiveness of the phase failure detection and protection device proposed in the present invention was confirmed.

<Analysis of protection device characteristics of Y-Y connection transformer>

Comparing the simulation value of the power system analysis software (PSCAD/EMTDC) with the results of the phase loss detection-protection device, As shown in Tables 11 and 12, it can be seen that they are almost similar.

Table 11 shows the voltage characteristics of the phase failure detection-protection device of the Y-Y connection ESS-linked transformer.

[Table 11]

As shown in Table 11, in the case of a pentagonal core and single-phase transformer, it is possible to detect it with the existing phase loss accident protection method because the voltage is not induced in the phase loss phase. It can be seen that it is difficult to detect phase loss with the accident protection method, so it is necessary to detect phase loss accidents according to the proposed phase loss detection algorithm.

Table 12 shows the operating characteristics of the phase failure detection-protection device of the Y-Y connection ESS-linked transformer.

[Table 12]

As shown in Table 12, when the transformer is a triangular iron core, the operation slope and primary current unbalance rate exceed the correction value (30 [%]) of the protection device, so the protection device is judged as a phase loss accident according to the proposed phase loss detection algorithm. You can see that it works. Therefore, it can be seen that the Y-Y connection pentagonal core and single-phase transformer type adopts the existing phase loss accident protection method, and the triangular iron core transformer must detect the phase loss accident according to the proposed phase loss detection algorithm. In addition, if an appropriate phase loss detection and protection device is not installed according to the wiring method and iron core structure of the ESS-linked transformer, if a disconnection accident occurs, the phase loss cannot be detected and the PCS for ESS may be operated alone, which may adversely affect the system. know that it can.

<Analysis of protection device characteristics of Y-Δ connection transformer>

Table 13 and Table 14 compare the simulation values of PSCAD/EMTDC and the results of the phase loss detection and protection device for the operating characteristics of the phase loss detection-protection device in the state where the primary A phase of the ESS-linked transformer is disconnected. It can be seen that it is almost similar to

Table 13 shows the voltage characteristics of the phase failure detection-protection device of the Y-Δ connection ESS-linked transformer.

[Table 13]

As shown in Table 13, the Y-Δ connection of the ESS-linked transformer induces voltage in all phases of the transformer regardless of the iron core structure, so it is difficult to detect phase loss with the existing phase loss protection method. It can be seen that it is necessary to detect .

Table 14 shows the operating characteristics of the phase failure detection-protection device of the Y-Δ connection ESS-linked transformer.

[Table 14]

As shown in Table 14, the operating slope and primary current unbalance rate in all iron core structures exceed the correction value (30 [%]) of the protection device, indicating that the protection device operates by judging it as a phase loss accident according to the proposed phase loss accident detection algorithm. Able to know.

Therefore, it can be seen that the Y-Δ connection should detect the image loss accident according to the proposed image loss detection algorithm regardless of the iron core structure. In addition, if an appropriate phase loss detection and protection device is not installed according to the wiring method and iron core structure of the ESS-linked transformer, if a disconnection accident occurs, the phase loss cannot be detected and the independent operation of the PCS for ESS and the reverse of the transformer for ESS-linked ESS It can be seen that the algae phenomenon can adversely affect the system.

), 무릎점(

), 동작 기울기(

), 전류 불평형률(

)을 계산한다. 상기한 정정치에 의한 보호장치의 동작 곡선은 도 4에 의하여 결정된다. As described above, in the present invention, when a phase loss occurs due to a disconnection of a distribution line connected to an ESS, a new type of phase loss detection algorithm using the concept of a current comparison method is proposed. That is, after assuming the transformer ratio, transformer ratio, angular displacement, and capacity of the ESS-linked transformer, the minimum operating current (the setting value of the phase failure detection-protection device)

), knee point (

), motion slope (

), current unbalance rate (

) is calculated. The operating curve of the protection device according to the above-mentioned correction value is determined by FIG. 4 .

)와 제한전류(

)를 계산한다. Subsequently, by measuring the magnitude and phase of the primary and secondary side currents of the ESS-linked transformer and substituting them into Equations (1) to Equations (2), the operating current of each phase (

) and limiting current (

) is calculated.

)와 제한전류(

)를 계산하는 단계로 이동한다. Subsequently, it is determined whether the operating current and limit current of each phase are included in the operating range. If not included, the operating current of each phase (

) and limiting current (

) to the step of calculating

Subsequently, the current unbalance rate is calculated according to Equation (7), and it is determined whether this value is greater than or equal to a set value. If it is more than the fixed value, it is judged as a phase loss accident and the protection device is operated.

Summarizing the main results of the new type image loss detection algorithm according to the present invention are as follows.

When the ESS-linked transformer has a Y-Y connection, it was found that the phase loss accident can be detected according to the phase loss detection algorithm proposed in the present invention because the phase loss voltage is induced in the triangular iron core structure, which is widely used in the field. .

In addition, when the ESS-linked transformer is Y-Δ connection, it induces voltage in the phase of phase loss regardless of the structure of the iron core, so it is difficult to detect phase loss with the existing phase loss accident protection method. I knew I had to detect it.

In addition, in order to prevent problems that adversely affect the system due to disconnection accidents, it was found that an appropriate phase loss detection and protection device should be employed according to the wiring method and iron core structure of the ESS-linked transformer, and the phase loss presented in the present invention It was confirmed that the detection algorithm of the accident detection-protection device is useful.

Although the above has been described with reference to examples, those skilled in the art can variously modify and change the present invention without departing from the spirit and scope of the present invention described in the claims below. You will understand.

TR: Transformer for ESS connection 10: 1st current generator (CT1)
20: second current generator (CT2) 110: first receiver
120: second receiving unit 130: detection control unit

Claims (5)

a first receiver configured to receive a first current sensed by a first current transformer installed on a primary side of an ESS-linked transformer;
a second receiving unit receiving a second current sensed by a second current transformer installed on a secondary side of the ESS-linked transformer; and
Calculate an operating slope and a current unbalance rate based on the magnitude and phase of each of the first current and the second current, and when both the operating slope and the current unbalance rate are equal to or greater than a set value, it is determined as a phase failure and the circuit breaker operates A phase failure detection-protection device for an ESS linkage transformer, characterized in that it comprises a detection control unit. The method of claim 1, wherein the detection control unit,
an upper unit for assuming a transformer ratio, a transformer ratio, and each displacement and capacity of the ESS-linked transformer;
Operation area determination unit for determining the operating area on the operating curve of the phase loss detection-protection device of the ESS linkage transformer by calculating the minimum operating current, knee point, operating slope, and current unbalance rate, which are the correct values of the phase loss detection-protection device ;
a calculation unit that calculates an operating current and a limiting current of each phase based on the magnitude and phase of each of the first current and the second current;
an operating range determination unit for determining whether the operating current and limit current of each phase are included in the operating range;
a current imbalance rate judging unit calculating a current imbalance rate when it is checked that the operating current and the limit current are included in the operating range, and determining whether the current imbalance rate is greater than or equal to a set value; and
When it is checked that the current unbalance rate is equal to or greater than the set value, the phase loss detection-protection device of the ESS-linked transformer, characterized in that it comprises an operation control unit for operating a protection device by determining that it is a phase loss accident. The method of claim 2, wherein the calculator calculates the measured current magnitude and phase.

and

(here,

: operating current,

: limiting current,

: Current of the primary side of the transformer,

: operating current of each phase by substituting the current of the secondary side of the transformer) (

) and limiting current (

) is calculated,
The current unbalance rate determining unit,

(here,

: Transformer primary side current unbalance factor,

: Phase a current of the primary side of the transformer,

: Phase b current of the primary side of the transformer,

: A phase failure detection-protection device for an ESS-linked transformer, characterized in that the current unbalance rate is calculated according to the c-phase current of the primary side of the transformer). (a) receiving a first current sensed by a first current transformer installed on a primary side of an ESS-linked transformer;
(b) receiving a second current sensed by a second current transformer installed on a secondary side of the ESS-linked transformer; and
(c) calculating an operating slope and a current unbalance rate based on the first current and the second current, and operating a circuit breaker by determining a phase failure when both the operating slope and the current unbalance rate are equal to or greater than a set value; Phase failure detection-protection method of an ESS-linked transformer, characterized in that it comprises. The method of claim 4, wherein the step (c),
(c-1) assuming a transformer ratio, transformer ratio, angular displacement and capacity of the ESS-linked transformer;
(c-2) Calculate the minimum operating current, knee point, operating slope, and current unbalance rate, which are the fixed values of the phase loss detection-protection device, to determine the operating area on the operating curve of the phase loss detection-protection device of the ESS-linked transformer doing;
(c-3) the current magnitude and phase of each of the first current and the second current

and

(here,

: operating current,

: limiting current,

: Current of the primary side of the transformer,

: operating current of each phase by substituting the current of the secondary side of the transformer) (

) and limiting current (

);
(c-4) The operating current of each phase (

) and limiting current (

) determining whether it is included in the operating range;
(c-5) feeding back to step (c-3) if it is checked in step (c-4) that the operating current and the limit current are not included in the operating range;
(c-6) If it is checked in step (c-4) that the operating current and the limiting current are included in the operating range,

(here,

: Transformer primary side current unbalance factor,

: Phase a current of the primary side of the transformer,

: Phase b current of the primary side of the transformer,

: Calculating a current unbalance rate according to the c-phase current of the primary side of the transformer), and determining whether the current unbalance rate is equal to or greater than a set value; and
(c-7) If it is checked that the current imbalance rate is equal to or greater than the set value in the step (c-6), phase failure detection of the ESS-connected transformer comprising the step of determining a phase failure and operating a circuit breaker. - How to protect.

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