KR20200003631A - Protection device and method for distributed energy resources in electric distribution system - Google Patents

Abstract

According to an embodiment of the present invention, provided is a protection device for connection with distributed power generators, comprising: a measurement unit configured to collect information on a voltage, a current, a frequency, a phase, and active power of a low or high voltage side connected with a distributed generator (DG); a calculation unit configured to calculate a change in the frequency, a change in the voltage, a change in the phase, and total harmonic distortion (THD); and a determination unit configured to determine that the DG is in an islanding condition if at least one of the changes in the frequency, voltage, phase, and/or the THD exceeds a maximum set value, and determine that the DG is in an islanding-suspected condition if at least one of the changes in the frequency, voltage, phase, and/or the THD is less than or equal to the maximum set value for each and exceeds a minimum set value.

Description

Protection device and method for distributed energy resources in electric distribution system}

One embodiment of the present invention relates to a distributed power supply protection device and method, and more specifically, for a distributed power supply connection that can be installed in the connection point to which the distribution system and the distributed power supply connected to the distribution system are connected. A protective device and method are provided.

Recently, due to the fossil energy depletion and environmental pollution, much attention has been focused on power generation using alternative energy. Power generation through alternative energy is called distributed power because it has smaller capacity and distributed around the demand area. Initially, distributed power supplies were operated in a state in which they were separated from the existing power system due to their small capacity. In recent years, the distributed power supplies have been operated in connection with the power system as their capacity increases.

Distributed power supply is generally connected to the power system through a grid-connected device having a structure of a circuit breaker and is always connected together, and has a structure that is separated from the power system when a problem occurs in the power system.

If an accident such as ground fault or short circuit occurs on the side where commercial AC power is supplied during operation in connection, the grid connection device is opened to separate the commercial power system and the distributed power system, and the overcurrent generated in the power system does not flow to the load. This protects the load and grid-connected distributed power system.

At this time, when the power system is separated, only the distributed power supply is connected to the load to supply power. This state is called an islanding state. In other words, islanding in grid-connected systems means that when a commercial system is interrupted from a power distribution system due to a power outage, a distributed power source, such as a photovoltaic power generation system, forms a single independent power distribution system to continue generating power to the load. Refers to the phenomenon being supplied.

However, in such a stand-alone operation, it may be difficult to supply stable power due to frequency and voltage fluctuations depending on the size of the active power produced by the distributed power supply and the size of the load. If this is recovered, an accident may occur in which a short circuit or a step out occurs due to the phase difference between both voltages. Therefore, it is necessary to quickly detect such a single operation state when linking distributed power systems.

These standalone detectors can be largely classified into passive and active techniques. The passive technique is basically a method of stopping the inverter by determining that it is a standalone operation when the detected parameter is out of the normal range by using system parameters necessary for controlling the inverter such as voltage and frequency. However, when the output power of the inverter and the power consumption of the load coincide, the voltage and frequency change is very small when the single operation occurs, so the single operation detection is likely to fail.

An active technique that compensates for these drawbacks is a technique that induces a change in voltage or frequency when an independent operation occurs by applying arbitrary disturbance to the output current of the inverter. In particular, the Active Frequency Drift Method (AFD) is widely known and used.

The AFD technique detects single operation by changing the frequency of the changed voltage to a specific value by increasing the frequency of the current and causing the frequency of the voltage to change rapidly in response to a rapid frequency change when the single operation occurs.

For example, the nominal frequency of KEPCO is 60Hz. When a system power failure occurs, the solar inverter uses the AFD method to change the frequency, which is a trip setting value of the over frequency relay (OFR). It exceeds 60.5Hz (Korean standard) to detect single operation. Alternatively, the nominal frequency 60Hz is exceeded the trip setting value of the Under Frequency Relay (UDR) 59.3Hz (Korean standard) to detect single operation.

The AFD technique has a problem in that power quality is deteriorated because the harmonic content of the current is increased due to the variation of the frequency of the current in a state connected to the system.

In particular, in order to detect single operation using the OFR or the UFR by using the conventional AFD technique, the frequency variation is increased to about 5%, which is a value of THD (Total Harmonic Distortion) component which is a current harmonic measurement. The power quality is lowered by increasing to about 5%, thereby shortening the lifespan of the power equipment.

Therefore, in the single operation detection method by the frequency fluctuation technique, the single operation detection method which prevents a fall of power quality and improves single operation detection performance is calculated | required.

The technical problem to be achieved by the present invention is to first determine the suspicion of sole operation of the distributed power supply, and then to apply the active detection method secondarily to isolate the non-detection area, which is a problem of the first passive detection method. Disclosed are a distributed power supply protection device and method capable of performing accurate detection of operation.

According to an embodiment of the present invention, a measurement unit for collecting voltage, current, frequency, phase and active power information associated with the distributed power supply; An operation unit which calculates a frequency variation, a voltage magnitude variation, a phase variation, and a harmonic distortion factor using the collected information; When at least one of the frequency change amount, the voltage magnitude change amount, the phase change amount, and the harmonic distortion ratio exceeds a maximum set value for each, it is determined as a distributed power supply alone situation, and the frequency change amount, the voltage magnitude change amount, and the Provides a distributed power supply protection device including a determination unit for determining whether the distributed power supply alone operation is suspicious when at least one of the phase change amount and the harmonic distortion is less than or equal to the maximum set value for each, and exceeds the minimum set value. .

The controller may further include a controller configured to output a corresponding distributed power system disconnection command when the distributed power supply alone is operated.

The control unit may further include a control unit configured to transmit an active power output command value to reduce the output of the inverter active power to the inverter when the distributed power supply suspicion of driving alone occurs.

The determination unit may determine that the distributed power supply alone is operated when the frequency collected through the measurement unit after the transmission of the active power output command value is less than a frequency set value.

The determination unit may determine the normal driving situation when the frequency collected through the measurement unit after the transmission of the active power output command value is greater than or equal to a frequency set value.

The controller may transmit an active power output command value a predetermined number of times to the inverter in order to sequentially decrease the output of the inverter active power when the distributed power supply alone suspicion of operation occurs.

The determination unit may determine the normal driving situation when the frequency collected through the measurement unit after the preset number of times of the active power output command value is greater than the frequency set value.

The controller may receive an output command value from an upper system or control the active / reactive power output of the distributed power supply by the self-determination when the active / reactive power output limitation of the distributed power supply is required.

The controller may block the distributed power system fault current when a failure occurs in the distributed power supply.

The controller may separate the system-side linkage in case of violation of the power quality regulation of the distributed power supply.

According to an embodiment of the present invention, the method includes: collecting voltage, current, frequency, phase, and active power information on a low voltage or high voltage side associated with a distributed power supply; Calculating frequency variation, voltage magnitude variation, phase variation, and harmonic distortion (THD) using the collected information; Determining at least one of a distributed power supply operation situation when at least one of the frequency change amount, the voltage magnitude change amount, the phase change amount, and the harmonic distortion rate exceeds a maximum setting value for each of the frequency change amounts; And determining whether the distributed power supply alone is suspected when at least one of the frequency change amount, the voltage magnitude change amount, the phase change amount, and the harmonic distortion is less than or equal to the maximum set value for each of the frequency change values and exceeds the minimum set value. It provides a distributed power supply protection method.

The method may further include outputting a corresponding distributed power system disconnection command in the distributed power supply alone operation situation.

The method may further include transmitting an active power output command value to reduce the output of the inverter active power to the inverter when the distributed power source alone operation suspect situation occurs.

Collecting a frequency after transmitting the active power output command value; And when the collected frequency is less than the frequency set value, determining that the distributed power supply alone is in operation.

Collecting a frequency after transmitting the active power output command value; And when the collected frequency is greater than or equal to a frequency set value, determining the normal driving situation.

The inventors of the present invention provide a protection apparatus and method for linking distributed power supplies, after first determining a suspicious operation state of a distributed power supply, and then applying an active detection method secondarily to detect a non-detection area that is a problem of the first passive detection method. Accurate detection of single operation.

In addition, since the active control algorithm can be applied sequentially, there is an advantage that it is not necessary to set the frequency change amount sensitively in order to minimize the undetected area.

In addition, since a plurality of connected inverters are controlled at the same time and under the same conditions, detection reliability can be improved.

In addition, by applying the DSOGI-PLL frequency measurement method (sample unit frequency change measurement), it is possible to improve the frequency measurement accuracy.

In addition, it is possible to minimize the adverse effect of the quality of the system compared to the standalone operation detection algorithm through the always active control.

1 to 4 is a conceptual diagram of a distributed power supply connection protection device according to the embodiment.
5 is a block diagram illustrating a configuration of a distributed power supply linkage protection device according to an embodiment.
6 is a flowchart illustrating a method for protecting distributed power supply according to an embodiment.

As the present invention allows for various changes and numerous embodiments, particular embodiments will be illustrated and described in the drawings. However, this is not intended to limit the present invention to specific embodiments, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

Terms including ordinal numbers, such as second and first, may be used to describe various components, but the components are not limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the second component may be referred to as the first component, and similarly, the first component may also be referred to as the second component. The term and / or includes a combination of a plurality of related items or any item of a plurality of related items.

When a component is referred to as being "connected" or "connected" to another component, it may be directly connected to or connected to that other component, but it may be understood that other components may be present in between. Should be. On the other hand, when a component is said to be "directly connected" or "directly connected" to another component, it should be understood that there is no other component in between.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprise" or "have" are intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, components, or a combination thereof.

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. Terms such as those defined in the commonly used dictionaries should be construed as having meanings consistent with the meanings in the context of the related art and shall not be construed in ideal or excessively formal meanings unless expressly defined in this application. Do not.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments will be described in detail with reference to the accompanying drawings, and the same or corresponding components will be given the same reference numerals regardless of the reference numerals, and redundant description thereof will be omitted.

1 to 4 is a conceptual diagram of a distributed power supply connection protection device according to the embodiment.

1 to 4, the distributed power supply protection device 10 according to the embodiment is a device applied to the distributed power supply 20 linked to the distribution system side, the distribution system and distributed power supply 20 ) Can be installed at the connection point to which it is connected.

1 is a conceptual diagram of a distributed power supply linkage protection device (slave installation type) associated with the low-pressure side, Figure 2 is a conceptual diagram of a distributed power linkage protection device (for installation of the generator premises) associated with the low-pressure side, Figure 3 is a conceptual diagram of a distributed power supply linkage protection device (for offset trade) associated with the low voltage side, and FIG. 4 is a conceptual diagram of a distributed power supply linkage protection device connected to the high voltage side.

Referring to FIG. 1, a distributed power supply protection device 10 is installed at a connection point stool, and blocks a plurality of distributed power generation companies 1, 2, 3,. Three phase).

Referring to FIG. 2, the distributed power supply connection protection device 10 may be installed in a power generation company premises to separate and block an individual power generation company (three phases).

Referring to FIG. 3, the distributed power supply linkage protection device 10 may be installed in the offset trading power generation company premises to separate and block (single phase) individual power generation companies.

However, if it is difficult to install in the premises of the generator, it can be installed in the neighboring inlet and stool.

The distributed power supply protection device 10 according to the embodiment may include a terminal unit 1, an open / close block 2, and a communication unit 3.

The distributed power supply protection device 10 according to the embodiment may monitor and cut off the independent operation of the distributed power supply 20, monitor the power quality, and perform voltage control on the voltage variation of the connection point. The distributed power supply protection device 10 may transmit the data acquired through the communication unit 3 to the higher system 30, and the distribution system and the distributed power supply through the supervision and control with the higher system 30. 20) Stable distribution line operation and power quality maintenance are possible.

In addition, the distributed power supply protection device 10 according to the embodiment monitors the electrical quality (PQM) of the distributed power supply 20 in real time to control the protection device by controlling the opening and closing block 2 when the deviation from the specified range By shutting off or stopping the operation of the inverter 21, the system can be stably operated.

In addition, the distributed power supply protection device 10 according to the embodiment can solve the voltage problem of the power distribution system by performing the tap adjustment of the OLTC power distribution transformer when the distribution voltage range is out of the specified voltage range.

In addition, the distributed power supply linkage protection device 10 according to the embodiment may perform the power factor control when the distributed voltage range is out of the specified voltage range.

In addition, the open / close block 2 of the distributed power supply connection protection device 10 according to the embodiment blocks the switch through the communication unit 3 and stops the inverter 21 when detecting the distributed power supply connection point fault current. The fault can be blocked.

5 is a block diagram illustrating a configuration of a distributed power supply linkage protection device according to an embodiment.

Referring to FIG. 5, the terminal unit 1 of the distributed power supply connection protection device 10 according to the embodiment includes a measurement unit 11, a calculation unit 12, a determination unit 13, and a control unit 14. Can be configured.

The measurement unit 11 may collect voltage, current, frequency, phase, and active power information on the low voltage or high voltage side associated with the distributed power supply 20. The measurement unit 11 may collect voltage, current, frequency, phase, and active power information on the low voltage or high voltage side from the terminal device 1 installed in the distribution line.

Three-phase current information can be measured from the CT sensor built in the switchgear 2, three-phase voltage information can be measured from the built-in PT sensor built in the switchgear (2). In addition, the DISOGI-PLL method may be applied to the frequency and phase information. The DISOGI-PLL method is a control method for synchronizing changing frequencies. It refers to a frequency measuring method using two SOGI filters integrating a voltage signal in order to prevent disturbance such as noise in a system.

The calculation unit 12 may calculate the frequency change amount, the voltage magnitude change amount, the phase change amount, and the harmonic distortion factor THD using the collected information.

For example, the calculator 12 may calculate the frequency change amount according to Equation 1 below.

[Equation 1]

는 전압 또는 전류의 주파수 변화량이고, t는 시간을 의미한다.In Equation 1

Is the frequency change of voltage or current, and t is time.

For example, the calculator 12 may calculate a voltage magnitude change amount according to Equation 2 below.

[Equation 2]

는 전압 크기 변화량이고, t는 시간을 의미한다.In equation (2)

Is the amount of change in voltage magnitude, and t is time.

For example, the calculator 12 may calculate a phase change amount according to Equation 3 below.

[Equation 3]

는 전압 또는 전류의 위상 변화량이고, t는 시간을 의미한다.In equation (3)

Is the amount of phase change in voltage or current, and t is time.

For example, the calculator 12 may calculate a harmonic distortion rate of voltage or current according to Equation 4 below.

[Equation 4]

은 기본파의 진폭이고,

는 고주파의 진폭을 의미한다.In equation (4)

Is the amplitude of the fundamental wave,

Is the amplitude of high frequency.

The determination unit 13 may determine that the distributed power supply alone operates when at least one of the frequency change amount, the voltage magnitude change amount, the phase change amount, and the harmonic distortion rate exceeds the maximum set value for each.

Alternatively, the determination unit 13 may determine that the distributed power supply alone is suspected when at least one of the frequency change amount, the voltage magnitude change amount, the phase change amount, and the harmonic distortion is less than or equal to the maximum setting value for each of the plurality, and exceeds the minimum setting value. Can be.

The determination unit 13 may determine that the distributed power supply alone operates when the frequency variation exceeds the maximum frequency variation set value. Alternatively, the determination unit 13 may determine that the distributed power supply alone operates when the voltage change amount exceeds the maximum voltage change amount setting value. Alternatively, the determination unit 13 may determine that the distributed power supply alone operates when the voltage and current phase change amount exceeds the maximum voltage and current phase change amount set value. Alternatively, the determination unit 13 may determine that the distributed power supply alone is operated when the harmonic distortion rate exceeds the maximum harmonic distortion rate setting value. That is, the determination unit 13 may determine that the distributed power supply alone operation occurs when at least one of the frequency change amount, the voltage magnitude change amount, the phase change amount, and the harmonic distortion rate exceeds the maximum set value for each.

The judging unit 13 secondly measures the frequency change amount, the voltage change amount, the phase change amount, and the harmonic distortion rate when at least one of the frequency change amount, the voltage magnitude change amount, the phase change amount, and the harmonic distortion rate does not exceed the maximum set value for each. The suspicious situation of distributed power supply alone can be detected by comparing with the minimum set value of.

The determination unit 13 may determine that the distributed power supply alone is suspected when the frequency change amount exceeds the minimum frequency change amount setting value. Alternatively, the determination unit 13 may determine that the distributed power supply alone operation is suspected when the amount of change in voltage exceeds the minimum voltage change amount. Alternatively, the determination unit 13 may determine that the distributed power supply alone operation is suspected when the voltage and current phase change amount exceeds the minimum voltage and current phase change amount setting value. Alternatively, the determination unit 13 may determine that the distributed power supply alone operation is suspected when the harmonic distortion rate exceeds a minimum total harmonic distortion rate setting value. That is, when the at least one of the frequency change amount, the voltage magnitude change amount, the phase change amount, and the harmonic distortion is less than or equal to the maximum setting value for each, the determination unit 13 operates the distributed power source alone when the respective minimum setting values are exceeded. It can be determined that a suspicious situation has occurred. Although it is not certain that a distributed power supply suspicion is a sole operation, it is highly likely that such a control algorithm is applied.

The determination unit 13 may determine that the driving condition is normal when the frequency change amount, the voltage magnitude change amount, the phase change amount, and the harmonic distortion are less than or equal to the minimum set value for each.

In an embodiment, each of the maximum setting values may have a value larger than the corresponding minimum setting value. If the minimum set value for determining the suspected distributed power supply alone operation is set too small, the probability of determining the distributed power supply alone operation suspect is high even though it is a normal operation situation. Therefore, in the embodiment, this problem can be solved by setting the minimum set value to a predetermined value or more and determining the suspicious situation of the distributed power supply alone.

In the embodiment, the maximum set value and the minimum set value are the result of simulating the normal operation situation and the single operation condition. Power system reliability and electrical quality maintenance criteria according to Article 2 ".

In addition, the determination unit 13 may transmit the effective power output command value of the control unit 14, and may determine that the distributed power supply alone is operated when the frequency collected through the measurement unit 11 is less than the frequency set value.

In addition, the determination unit 13 may transmit the effective power output command value from the control unit 14, and may determine the normal driving situation when the frequency collected through the measurement unit 11 is equal to or greater than the frequency setting value.

In addition, the determination unit 13 may transmit the effective power output command value for a predetermined number of times by the control unit 14, and may determine the normal operation situation when the frequency collected through the measurement unit 11 is greater than or equal to the frequency set value. .

The controller 14 may output the distributed power system disconnection command when the distributed power supply alone operates.

In addition, the controller 14 may transmit an active power output command value for reducing the output of the inverter active power to the inverter when a distributed power supply alone operation suspect situation occurs.

In addition, the controller 14 may transmit an active power output command value a predetermined number of times to the inverter in order to sequentially reduce the output of the inverter active power when a distributed power supply alone operation suspect situation occurs.

), 부하(

)에 따른 주파수(

)의 상관관계는 수학식 5와 같이 정의될 수 있다. 수학식 5에서 주파수 설정값은 60Hz이다.Distributed power output when distributed power supply alone

), Load(

) According to

) Can be defined as in Equation 5. In Equation 5, the frequency setting is 60 Hz.

[Equation 5]

)을 점진적으로 감소시키면, 수학식 5와 같이 주파수(

)도 점진적으로 감소하게 된다.That is, the output of the distributed power supply (

) Gradually decreasing the frequency, as shown in Equation 5

) Will also decrease gradually.

The controller 14 transmits an inverter active power output command value to the inverter in order to gradually reduce the output of the distributed power supply when a situation where the distributed power supply alone operation is suspected occurs. The inverter reduces the active power output of the distributed power supply according to the active power output command value and correspondingly reduces the frequency.

For example, if the distributed power source is 100kW and the load is 100kW when the distributed power source alone is suspected, the control unit 14 may set the effective power output command to reduce the effective power output of the distributed power source to 95%. Transfer it to the inverter. The inverter accordingly reduces the output of the distributed power supply to 95 kW and the frequency value correspondingly. Next, the control unit 14 sequentially transmits the active power output command value to reduce the effective power output of the distributed power supply to 90%, 85% to the inverter. The inverter sequentially reduces the output of the distributed power supply to 90 kW and 85 kW, and the frequency value correspondingly decreases. The control unit transmits the effective power output command value to the inverter a predetermined number of times to reduce the output and frequency of the distributed power supply.

The determination unit 13 may transmit the active power output command value a predetermined number of times by the control unit 14, and then determine that the driving state is normal when the frequency collected through the measurement unit 11 is equal to or greater than the frequency setting value. That is, when the reduced frequency value maintains the frequency setting value or more in response to the decrease in output of the distributed power supply, the determination unit 13 may cancel the suspected distributed power supply alone operation and determine that it is a normal operation situation. .

However, after the determination unit 13 transmits the effective power output command value of the control unit, if the frequency collected through the measurement unit 11 is less than the frequency set value, it may determine that the distributed power supply alone operation. That is, the determination unit 13 may determine that the distributed power source alone operation situation occurs when the reduced frequency value corresponding to the output reduction of the distributed power source is less than the frequency set value.

The controller 14 receives the output command value from the host system or controls the active / reactive power output of the distributed power supply by the self-determination when the restricted or reactive power output limitation of the distributed power supply is required to ensure the safety of system operation. can do. The controller 14 may control the effective power by controlling the power generation amount of the current distributed power supply to be gradually lowered when the current frequency is greater than the prescribed frequency (upper limit). For example, the controller 14 may control the active power through an active power output command value that is proportional to the difference between the current generation amount, the current system frequency, and the prescribed frequency. In Equation 6, P * is the active power output command value, P is the current active power, f is the current frequency, fmin-set is the specified frequency, K is the proportional coefficient. The active power output command value may be calculated by self determination and transmitted to the inverter, or may be received from the host system and transferred to the inverter.

[Equation 6]

Alternatively, the controller 14 may receive the reactive power output command value of the distributed power supply from a higher level system or calculate it by the self-determination when the distributed power supply connection point voltage is greater than the specified voltage. For example, the controller 14 may control the reactive power through a reactive power output command value that is proportional to the difference between the current link point voltage and the specified voltage and the current generation amount according to Equation 7 below. In Equation 7, Q * is the reactive power output command value, Q is the current reactive power, P is the current active power, V is the connection point voltage, Vmax-set is the specified voltage, K is the proportional coefficient. The active power output command value may be calculated by self determination and transmitted to the inverter, or may be received from the host system and transferred to the inverter.

[Equation 7]

The controller 14 may block the distributed power system fault current to protect the system when a distributed power supply side fault occurs. The control unit 14 may perform distributed power system separation through an open / close blocker when a failure is determined based on a protection relay element OCR, OCGR, OVR, UVR, OFR, or UFR. The fault current cutoff control command may be calculated by self determination and may be transmitted to the open / close block or may be received from a higher level system and transmitted to the open / close block.

The controller 14 may separate the grid-side linkage when the distributed power-side power quality regulation value is violated. The controller 14 may separate the distributed power supply system when the PQM setting value is exceeded through constant output monitoring of power quality PQM (Sag, Swell, Interruption, Harmonics (3th, THD), etc.) Calculated by and delivered to the opening and closing block or may be received from the host system and delivered to the opening and closing block.

Figure 6 is a flow chart of a distributed power supply protection method according to an embodiment of the present invention.

Referring to FIG. 6, first, the measurement unit collects voltage, current, frequency, phase, and active power information on the low voltage or high voltage side associated with a distributed power supply. The measurement unit collects voltage, current, frequency, phase, and active power information on the low voltage or high voltage side from the terminal device installed in the distribution line (S601).

The calculating unit calculates the frequency change amount, the voltage magnitude change amount, the phase change amount, and the harmonic distortion factor THD using the collected information (S602).

If the at least one of the frequency change amount, the voltage magnitude change amount, the phase change amount, and the harmonic distortion rate exceeds the maximum set value for each, the determination unit determines that the distributed power supply alone is operated (S603).

The control unit outputs a corresponding distributed power system disconnection command when the distributed power source is operated alone (S604).

The determination unit determines that at least one of the frequency change amount, the voltage magnitude change amount, the phase change amount, and the harmonic distortion is less than or equal to the maximum setting value and exceeds the minimum setting value (S605).

The controller transmits an active power output command value for reducing the output of the inverter active power to the inverter for a preset number n when the distributed power supply solenoid driving situation occurs (S606).

The measurement unit collects the frequency after transmitting the active power output command value, and if the collected frequency is less than the frequency set value, the measurement unit determines that the distributed power supply alone is in operation (S607).

If the frequency collected for a predetermined number of times or more than the frequency set value, the determination unit releases the suspected distributed power supply alone operation state and determines the normal operation state (S608).

The term '~ part' used in the present embodiment refers to software or a hardware component such as a field-programmable gate array (FPGA) or an ASIC, and '~ part' performs certain roles. However, '~' is not meant to be limited to software or hardware. '~ Portion' may be configured to be in an addressable storage medium or may be configured to play one or more processors. Thus, as an example, '~' means components such as software components, object-oriented software components, class components, and task components, and processes, functions, properties, procedures, and the like. Subroutines, segments of program code, drivers, firmware, microcode, circuits, data, databases, data structures, tables, arrays, and variables. The functionality provided within the components and the 'parts' may be combined into a smaller number of components and the 'parts' or further separated into additional components and the 'parts'. In addition, the components and '~' may be implemented to play one or more CPUs in the device or secure multimedia card.

Although described above with reference to a preferred embodiment of the present invention, those skilled in the art will be variously modified and changed within the scope of the invention without departing from the spirit and scope of the invention described in the claims below I can understand that you can.

10: Protective device for distributed power supply
11: measuring part
12: calculation unit
13: judgment
14: control unit

Claims (15)

A measurement unit collecting voltage and current information on the low voltage or high voltage side associated with the distributed power supply;
An operation unit which calculates a frequency variation, a voltage magnitude variation, a phase variation, and a harmonic distortion factor using the collected information; And
When at least one of the frequency change amount, the voltage magnitude change amount, the phase change amount, and the harmonic distortion ratio exceeds a maximum setting value for each, it is determined as a distributed power supply alone situation, and the frequency change amount, the voltage magnitude change amount, and the And at least one of a phase change amount and the harmonic distortion factor is less than or equal to the maximum setting value for each of the harmonic distortion rates, and exceeds the minimum setting value.
The method of claim 1,
And a control unit for outputting a distributed power system disconnection command when the distributed power supply alone operation situation.
The method of claim 1,
And a control unit for transmitting an active power output command value for reducing the output of the inverter active power to the inverter when the distributed power source alone operation suspect situation occurs.
The method of claim 3,
The determining unit determines the distributed power supply alone when the frequency collected by the measuring unit after the transmission of the active power output command value is less than the frequency set value, the distributed power supply protection device.
The method of claim 3,
The determining unit is a distributed power supply protection device for determining that the normal operating situation when the frequency collected through the measuring unit after the transmission of the active power output command value is greater than the frequency set value.
The method of claim 3,
The control unit is a distributed power supply connection protection device for transmitting a predetermined number of active power output command value to the inverter in order to sequentially reduce the output of the inverter active power when the situation of the distributed power supply alone operation suspicion occurs.
The method of claim 6,
The determining unit determines that the normal operating situation when the frequency collected through the measuring unit after the transmission of the active power output command value a predetermined number of times or more than the frequency setting value determines the normal operating situation.
The method of claim 2,
The controller may be configured to receive an output command value from an upper system or to control the active / reactive power output of the distributed power source by the self-determination when the active / reactive power output limitation of the distributed power source is required. Device
The method of claim 2,
The control unit is a distributed power supply protection device for blocking the distributed current system failure current when the failure of the distributed power supply
The method of claim 2,
The control unit is a distributed power supply linkage protection device for disconnecting the grid-side linkage in case of violation of the power quality regulation value of the distributed power supply
Collecting voltage, current, frequency, phase, and active power information on the low voltage or high voltage side associated with the distributed power supply;
Calculating frequency variation, voltage magnitude variation, phase variation, and harmonic distortion (THD) using the collected information;
Determining at least one of a distributed power supply operation situation when at least one of the frequency change amount, the voltage magnitude change amount, the phase change amount, and the harmonic distortion rate exceeds a maximum setting value for each of the frequency change amounts; And
Determining whether the distributed power supply alone is suspected when at least one of the frequency change amount, the voltage magnitude change amount, the phase change amount, and the harmonic distortion is less than or equal to the maximum set value for each of the frequency change values and exceeds the minimum set value. Protection method for distributed power linkage.
The method of claim 11,
The distributed power supply protection method further comprising the step of outputting the distributed power system disconnection command when the distributed power supply alone operation situation.
The method of claim 11,
And transmitting an active power output command value to reduce the output of the inverter active power to the inverter when the distributed power source alone operation suspect situation occurs.
The method of claim 13,
Collecting a frequency after transmitting the active power output command value; And
If the collected frequency is less than the frequency set value, the distributed power supply protection method further comprising the step of determining the distributed power supply alone operation.
The method of claim 13,
Collecting a frequency after transmitting the active power output command value; And
When the collected frequency is greater than the frequency set value, the distributed power supply protection method further comprising the step of determining a normal operating situation.

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