KR102234711B1 - Control method to autonomously control voltage of distributed energy resources - Google Patents

Abstract

The present invention relates to a distributed resource management system capable of managing distributed resources distributed in a power grid and a control method thereof. According to the present invention, provided is a control method of a computing device for controlling the distributed resources supplying active power from a first point to a second point through a line. The control method can comprise the steps of: calculating a ratio of a resistance (R) to a reactance (X) of the line; and adjusting reactive power supplied or absorbed to the line based on the ratio.

Description

Control method to autonomously control the voltage of distributed resources{CONTROL METHOD TO AUTONOMOUSLY CONTROL VOLTAGE OF DISTRIBUTED ENERGY RESOURCES}

The present invention relates to a control method for autonomously controlling voltages of distributed resources distributed in a power grid, and more specifically, to a method for controlling distributed resources capable of managing distributed resources.

Distributed Energy Resource (DER) is actively being introduced into the power system in order to complement the power supply method centered on the central power supply generator. Distributed resources are sometimes referred to as'distributed energy resources' or'distributed power sources'.

Since distributed resources (DER) are installed in small and medium-sized near demand sites, they can be installed in a short period of time at the required scale in the required area. In addition, since the distributed resource (DER) directly supplies power near the demand site, it can significantly reduce the overall energy loss due to transmission loss, and this delays the investment required for power infrastructure reinforcement and expansion by mitigating the load on the transmission system. Or make it possible to avoid it. In general, distributed resources (DER) can contribute to short-term stabilization of the distribution network because generators can be started within a short period of time, and when power is insufficient, additional power generation can be used to flexibly and effectively respond to peak demand, thereby improving system reliability and power quality. It can also be used.

However, the cost of generating distributed resources (DER) is still high, and there are a number of technical challenges to be solved in terms of operation as well. For example, when the DER generation capacity of a specific region exceeds the demand of the region, it causes reverse currents in the power grid. Such reverse currents not only cause congestion in the distribution network, but also make it difficult to maintain an appropriate level of voltage, and in the event of an accident, there is a possibility that a situation that cannot be solved with the existing protection cooperation system may occur. Due to such technical problems, a simple fit & forget method is currently applied when linking distributed resources (DER). This is suitable for the passive distribution network operating environment in the past, but not only limits the efficient use of distributed resources (DER), but also leads to an increase in investment costs and insufficient investment incentives for the distribution infrastructure. To solve this problem, it is necessary to improve the current power and ICT infrastructure and establish effective linkage plans so that distributed resources (DER) can replace the role of the existing large-scale central power plant. You need to build a control strategy that you can support. This means a change from a central control concept for hundreds of units of central power supply generators to a new distributed control paradigm suitable for the operation of hundreds of thousands of generators and controllable loads.

Conventionally, voltage rise of distribution lines frequently occurs due to distributed resources, and many control methods have been proposed to control this. In Korea, the DER-AVM function has been developed and applied to stabilize the voltage raised by the distributed resources of the distribution system, and this DER-AVM function is currently being operated in about 100 places. In addition, it is a technology that needs to be installed in more than 50,000 groups in the future and operated to stabilize the voltage of the distribution system. Distributed resources linked to the extra-high voltage system control the voltage at the point of connection through the'Extra-high-pressure distributed resource relay device' and the FRTU, and the distributed resources connected to the low-voltage system use the'low-voltage distributed resource linkage device'. The linkage device is designed to stabilize the voltage of the low-voltage transformer by controlling up to three distributed resources.

In the case of the prior art, since it is very difficult to obtain an accurate Thevenin equivalent impedance of a point where distributed resources are linked, a question about the efficiency of voltage stabilization has been raised.

The background technology of the present invention is disclosed in'Intelligent Power Grid Operation System for Managing Distributed Energy Resources in a Power Grid' of Korean Patent Application Publication No. 10-2019-0073340 (2019.06.26).

An object of the present invention is to solve the above-described problem, and to provide a control method capable of managing a plurality of distributed resources by autonomously controlling voltages of distributed resources distributed in a power grid.

The present invention is derived from such a technical background, and in order to increase the overall system stabilization effect by receiving the optimal control command through interlocking with the upper system, the QV droop curve, the power factor control command, and the QP droop curve are autonomously applied in the inverter. Its purpose is to provide a method for controlling autonomous voltage of distributed resources that can be set.

The present invention relates to a distributed resource management system capable of managing distributed resources distributed in a power grid and a control method thereof. More specifically, the present invention provides a control method for autonomously controlling the voltage of distributed resources.

According to the present invention, there is provided a control method of a computing device for controlling distributed resources supplying active power from a first point to a second point through a line.

The control method includes calculating a ratio of resistance (R) and reactance (X) of the line; And adjusting the reactive power supplied or absorbed to the line based on the ratio.

According to an embodiment, the control method includes: calculating a power factor command for controlling the voltage fluctuation of the distributed resource to zero based on the ratio; And transmitting the power factor command to the distributed resource.

According to an embodiment, the calculating of the power factor command includes: setting an adjustment variable for the distributed resource; And calculating the power factor command based on the adjustment variable and the ratio.

According to an embodiment, the adjustment variable may vary according to the distributed resource.

According to an embodiment, the control method includes: defining an equation between the voltage of the distributed resource and the reactive power based on the ratio; Measuring the voltage of the distributed resource; And adjusting the reactive power so that the reactive power corresponds to the measured voltage in the equation.

According to an embodiment, the calculating of the ratio may include changing the active power while maintaining the reactive power within a certain range; Measuring a first change amount of a voltage corresponding to the change amount of the active power; calculating a resistance of the line based on the first change amount; Changing the reactive power while maintaining the active power within a certain range; Measuring a second variation in voltage corresponding to the variation in reactive power; Calculating reactance of the line based on the second change amount; And calculating the ratio by dividing the resistance by the reactance.

According to an embodiment, the calculating of the ratio may include: supplying the active power of a predetermined size to the line using the distributed resources; Measuring a first voltage immediately before supplying the active power of the predetermined size; Supplying the reactive power of the predetermined size to the line by using the distributed resources; Measuring a second voltage immediately before supplying the reactive power of the predetermined size; And calculating the ratio using the first voltage and the second voltage.

According to an embodiment, the calculating of the ratio may include: fixing an amount of effective power supplied by the distributed resource to the line; Adjusting the amount of reactive power supplied to the line by the distributed resource while the amount of active power is fixed, and searching for a target amount of reactive power whose voltage fluctuation becomes zero; And calculating the ratio by using the amount of active power and the amount of target reactive power.

The present invention for achieving the above object includes the following configurations.

The autonomous voltage control method of distributed resources performed in the distributed resource control system according to an embodiment of the present invention includes controlling the supply of at least one of active power and reactive power, measuring the voltage of the distributed resource linkage point, the The step of determining the resistance value (R) or the reactance value (X) using the voltage fluctuation value of the measured connection point, and the reactance and resistance ratio (X/ It characterized in that it comprises the step of estimating the R ratio).

Meanwhile, the autonomous voltage control method of distributed resources that generates a QV droop curve performed in a distributed resource control system is the step of determining the dead band of the QV droop curve, and the X/R ratio of the distribution system viewed from the distributed resource. Determining the scale factor (a) for the QV droop curve, determining the reference voltage value of the QV droop curve, determining the reactance and resistance ratio (X/R ratio) of the distribution system viewed from the distributed resource, and the determined reactance And calculating a characteristic value of the QV Droop curve using the and resistance ratio (X/R ratio).

In addition, the autonomous voltage control method of distributed resources that generates a QP droop curve performed in the distributed resource control system is the step of determining the dead band of the QP droop curve, and is based on the X/R ratio of the distribution system viewed from the distributed resource. Determining the scale factor (a) for the QP droop curve, determining the reference active power of the QP droop curve, determining the reactance and resistance ratio (X/R ratio) of the distribution system viewed from the distributed resource, and the determined reactance And calculating a characteristic value of the QP Droop curve using the resistance ratio (X/R ratio).

According to the present invention, it is possible to provide an autonomous voltage control method of distributed resources capable of autonomously setting a Q-V droop curve, a power factor control command, and a Q-P droop curve in an inverter in order to increase the overall system stabilization effect.

In addition, according to the present invention, when a small-capacity distributed resource autonomously creates and responds to a function for controlling distributed resources by itself, it will be possible to have a very effective distribution operation structure.

For example, in 2018, about 50,000 distributed resources are experiencing connection delays. In order to achieve the government's regeneration e 3020 implementation plan, the capacity of additional distributed resources to be connected to the distribution system is estimated to be about 27GW, which is about three times the capacity of 10GW connected to the current distribution system.

Currently, distributed resources are mostly connected to the distribution system, causing overvoltage in distribution lines by changing the direction of the electric current, and frequent output fluctuations of distributed resources affect the customer's electricity quality. Therefore, as the linkage capacity of distributed resources increases, the importance of voltage stabilization of distribution lines using distributed resource control will increase.

Here, it is necessary to examine whether it is possible to directly manage all distributed resources linked to the distribution system. Except for about 45,000 of the distributed resources linked to the distribution system, most are offset transactions distributed resources. In other words, it may mean that the number of distributed resources to be managed and monitored is currently about 45,000. If the 2030 Regeneratione Implementation Plan is achieved, the number of distributed resources to be managed could increase significantly, exceeding 100,000. Currently, the number of 100kW-class distributed resources accounts for about 40% of the 45,000 accumulated distributed resources. Here, we must consider whether we should directly control and monitor 100kW-class distributed resources using the distribution operation system. Of course, monitoring should be performed, but if it is controlled directly, the investment cost for the hardware platform performance of the distribution operating system will not be neglected. Therefore, if small-capacity distributed resources autonomously create and act on the control of distributed resources, a very effective distribution operation structure can be obtained.

Suppose that the number of distributed resources to be managed in 2030 is 100,000 units, and at this time, the number of distributed resources with a capacity of 100 kW or less is 70%. If the distribution operation system does not directly control the distributed resource by itself using the methods proposed in the present invention patent, and if the investment cost of the control facility invested in one distributed resource can be reduced by 1,000,000 won, about 70,000 units are distributed. The amount that can be saved from resources will be about 70 billion.

If distributed resources less than 100kW are not the target, but all distributed resources linked to the low-voltage system are controlled for autonomous operation, the economic effect will increase further.

In addition, when 70,000 distributed resources are used for autonomous operation control proposed in the present invention patent, it is possible to additionally contribute to system stabilization, thereby reducing the cost of equipment investment for compensating the electric quality of customers, and stabilization of the distribution system voltage. As it is possible to increase the capacity of the hosting capacity according to the following, it is possible to reduce the investment cost for new expansion of distribution facilities by linking distributed resources.

1 is a block diagram of a system for managing distributed energy resources of a power grid
Figure 2 is a diagram for explaining the cause of the electrical voltage drop and voltage rise
3 is a curve for QV Droop control
Figure 4a is a diagram showing the X/R Ratio for each location in the distribution system
4B is a diagram showing variations in short-circuit impedance for each location in a distribution system
5 is a diagram for explaining a method of creating a curve for QV Droop control
6 is a diagram for explaining a method of creating a curve for QP Droop control
FIG. 7 is a diagram for explaining an upper controller for power factor control and a control structure of distributed resources
8 is a diagram for explaining a control structure of an upper level controller and distributed resources for creating a QV droop curve
9 is a diagram for explaining voltage fluctuations by distance of a general distribution line in a line with only a load
10 is a diagram for explaining a control structure of an upper level controller and distributed resources for creating a QP droop curve
11 is a flowchart of a method for controlling autonomous voltage of distributed resources performed in a distributed resource control system according to an embodiment of the present invention;
12 is a flowchart of an autonomous voltage control method of distributed resources for generating a QV Droop curve performed in a distributed resource control system according to an aspect of the present invention;
13 is a flowchart of an autonomous voltage control method of distributed resources for generating a QP droop curve according to an embodiment of the present invention

Hereinafter, exemplary embodiments disclosed in the present specification will be described in detail with reference to the accompanying drawings, but the same reference numerals are assigned to the same or similar elements regardless of the reference numerals, and redundant descriptions thereof will be omitted. The suffixes "module" and "unit" for constituent elements used in the following description are given or used interchangeably in consideration of only the ease of writing the specification, and do not themselves have a distinct meaning or role from each other. In addition, in describing the embodiments disclosed in the present specification, when it is determined that a detailed description of related known technologies may obscure the subject matter of the embodiments disclosed in the present specification, the detailed description thereof will be omitted. In addition, the accompanying drawings are for easy understanding of the embodiments disclosed in the present specification, and the technical idea disclosed in the present specification is not limited by the accompanying drawings, and all changes included in the spirit and scope of the present invention It should be understood to include equivalents or substitutes.

Terms including ordinal numbers such as first and second may be used to describe various elements, but the elements are not defined by the terms. The above terms are used only for the purpose of distinguishing one component from another component.

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

Singular expressions include plural expressions unless the context clearly indicates otherwise.

In this application, terms such as "comprises" or "have" are intended to designate the presence of features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, but one or more other features. It is to be understood that the presence or addition of elements or numbers, steps, actions, components, parts, or combinations thereof does not preclude in advance.

The terminal described in the present invention may correspond to at least one of a mobile terminal and a fixed terminal. Mobile terminals include mobile phones, smart phones, laptop computers, digital broadcasting terminals, personal digital assistants (PDAs), portable multimedia players (PMPs), navigation, slate PCs, and tablet PCs. PC), ultrabook, etc. may be included. The fixed terminal may include a desktop computer, a server, and the like.

The distributed power grid system aggregates energy resources consisting of several distributed resources (DERs) and provides services to one or several energy markets with several DERs as a single market resource. DER can generate data representing real-time local demand and DER's local energy capacity. Based on DER information and real-time market information, the system can calculate how to provide one or several services to the grid based on the DER energy capacity aggregation.

Electric power is supplied by alternating current (AC) with sinusoidal current and voltage waveforms in the power grid system, and this alternating current can be thought of as alternating in and out of electricity. Since AC energy flows in the reverse direction by the transformer monitored by the operator and can be modulated up and down in real time, transmission through high voltage power lines is possible while minimizing power line losses due to heat. Since AC energy travels from transmission lines to substations and power lines and eventually to end users, continuous and well-balanced control between active and reactive power is required.

The power supplied by the power grid is generally composed of an active power component and a reactive power component.

The unit of measure for active power is watts (W), which refers to active energy that does electrical work. Active power is supplied when the voltage and current waveforms are perfectly aligned in phase. For efficient active power supply, the demand point for the active energy waveform must coincide with the supply point of the energy waveform from the power grid. If these timings do not coincide, power loss occurs during energy transfer.

The unit of measure for reactive power is volt-ampere reactive (VAR), which refers to energy that reduces power loss by matching two points of time. Reactive power can lead or delay compared to active power based on the phase difference between the current and voltage waveforms.

1 is a block diagram of a system for managing distributed energy resources of a power grid. The system 100 includes a power grid, and the power grid 120 includes a distribution management system (DMS) 122 for transmitting power along a transmission line. Distribution control 122 manages the downstream flow of power from one or several power plants 140 to several customers 124. Customer 124 represents one or several groups of consumers and is connected at several locations downstream of power plant 140.

In embodiments, at least some of the customers 124 may be referred to as “prosumers”, which are consumers that produce power locally. Traditional local power generation in distributed resources (DER) may include power generation using "generators", "spare generators", "renewable energy sources" or "field power systems". Distributed resource (DER) refers to a small-scale energy generating source installed near a home or business that consumes electricity. So-called "green power" technology, such as a solar or photovoltaic (PV) system (a PV cell plate installed on the roof converts sunlight into electricity) or a wind power system (a turbine connected to a fan blade installed at the top of the tower uses wind to generate electricity) This is the most common.

When the traditional DER is expanded in the customer 124, non-intelligent watt injection occurs into the power grid, which can put a burden on the power grid 120. Such wattage injection cannot be controlled in real time, such as AC energy flow. Utility companies tend to spread the cost of increased VAR requirements due to watt injection. In an embodiment, at least some of the customers 124 include distributed resources 130. Control center 110 manages nodes 132 to aggregate and provide combined functions as a single energy resource available in one or several energy markets.

Nodes 132 are understood to represent individual nodes of a distributed resource (DER) each having a local energy production resource. In an embodiment, the control center 110 includes a local power source 112 similar to a "traditional power plant" but with less output capacity. In an embodiment, the local power source 112 may provide a basic level of power that can be aggregated with the power supplied from the node 132 to trade in the energy market. Energy market transactions are a bid or offer for one or several types of energy services required by the grid, such as active power capacity, auxiliary services (e.g. voltage or reactive power support), demand/response services, other services, or specific combinations. Say that. In an embodiment, the control center 110 is connected to the power grid 120 through a common connection point (PCC) 126. The common connection point 126 may represent several different connection points, such as connection points for different distributed resource nodes 132. Overall, the control center 110 may provide an energy service to the power grid 120 through the distributed resource 130.

Each node 132 may perform real-time control. For example, it is possible to monitor, analyze, control, aggregate, and predict the wattage of a system, while controlling VAR emissions at the same time. Monitoring wattage and VAR enables optimal energy efficiency, maximizes cost savings for consumers, and stabilizes power grid 120 operation.

2 is a diagram for explaining a cause of an electric voltage drop and a voltage increase.

When analyzing the basic electrical phenomenon, a voltage drop occurs as much as the current flowing through the line and the impedance of the line according to the flow of the electric current. That is, the voltage at the place where electricity is generated is not supplied to the consumed place due to the voltage drop caused by the product of the impedance present in the line while the current flows from the place where electricity is generated to the place where it is consumed. The following figure shows the causes of electrical voltage drop and voltage rise.

If the voltage between Es and Er is ΔV as shown in FIG. 2, ΔV can be simply determined by [Equation 1].

At this time, R is the resistance of the line, X is the reactance of the line, P is the active power flowing through the line, and Q is the reactive power supplied/absorbed by the line. That is, when reactive power is supplied, the reactive power provides a cause of increasing the voltage, and when reactive power is absorbed, the reactive power can lower the voltage. If this phenomenon is projected into distributed resources and general distribution systems and analyzed, the supply of active power from distributed power sources causes the voltage to rise in the distribution system, and the voltage at the junction of distributed resources rises according to how the reactive power of distributed power sources is controlled. You can do it, and you can descend. At this time, the size of the line impedance (R, X) is very important. If distributed resources are connected to a complex distribution system, the size of R among the Tevennon equivalent impedance components of the distribution system viewed by the distributed resources is larger than the size of X. If it is relatively large, the degree of voltage stabilization due to reactive power control at the linkage point will be insignificant than the linkage point where the size of X is relatively larger than the size of R.

Conventionally, voltage rise of distribution lines frequently occurs due to distributed resources, and many control methods have been proposed to control this. In Korea, the DER-AVM function has been developed and applied to stabilize the voltage raised by the distributed resources of the distribution system, and this DER-AVM function is currently being operated in about 100 places. In addition, it is a technology that needs to be installed in more than 50,000 groups in the future and operated to stabilize the voltage of the distribution system. Distributed resources linked to the extra-high voltage system control the voltage at the point of connection through the'Extra-high-pressure distributed resource relay device' and the FRTU, and the distributed resources connected to the low-voltage system use the'low-voltage distributed resource linkage device'. The linkage device is designed to stabilize the voltage of the low-voltage transformer by controlling up to three distributed resources.

The method of stabilizing the voltage raised by the distributed resource due to its own active power output can be stabilized to a desired voltage by supplying/absorption control of reactive power in principle, but methodologically, it is possible in the following four ways.

First, a method of controlling the QV droop that controls the supply/absorption of reactive power according to the voltage fluctuations, second, a method of controlling the power factor to supply/absorb reactive power by controlling the power factor according to the fluctuations of the active power, and the third, effective. QP Droop control method that allows reactive power to be controlled according to power fluctuations, and fourth, reactive power is controlled according to voltage fluctuations, but a method of decreasing the active power by reducing the active power according to the lack of reactive power control is a method of reducing the voltage. have.

All three of the above four methods control reactive power in the end, but there is a difference between controlling reactive power directly or indirectly. Here, the Droop control refers to a control method in which a curve in the form of a linear function is determined, and a command value for output is determined according to the fluctuation of the input. The difference between droop control and power factor control is that in the case of droop control, the reactive power that must be supplied or absorbed must constantly change according to the fluctuations in the input voltage or active power, but in the case of power factor control, it is not the fluctuation of the input active power. Regardless of the power factor command is constant. Instead, since the power factor command is constant, the reactive power fluctuates to keep the power factor constant according to the fluctuations of the active power.

At this time, depending on what type of function the Droop curve of these control methods has, that is, the slope of the linear function, the amount of reactive power supply/absorption according to voltage fluctuations will be different, and consequently, the control effect will be very different. .

3 shows a curve for Q-V Droop control.

In general, the voltage is input to the controller in the form of a PU (per unit), and the amount of reactive power supplied and absorbed according to voltage fluctuations varies depending on whether the distributed resource takes a red curve or a blue curve. In addition, in the case of the above figure, it is a dead band section that does not supply or absorb reactive power when the voltage is in the range of 0.98 to 1.02PU, so that unnecessary or frequent reactive power control is not performed in the section where the voltage fluctuation is not large.

As for QP droop control, the compensation amount varies depending on how the droop curve is taken, so the slope of this curve is very important. Is different. If there is a large amount of compensation, it may be the cause of frequent voltage fluctuations, so it is very important to select such a slope degree or a control setting value.

Since the characteristics of these control curves or control set values are determined by Thevenin equivalent impedance viewed from the connection point of the distributed resource as shown in the equation below, the R and X values of Thevenin equivalent impedance through systematic analysis in the upper system. It has been mainly decided in the form of obtaining and setting the corresponding control command through communication, or by selecting an appropriate value through offline analysis and inputting it to the inverter of the distributed resource. However, this form is very inconvenient, and since it is very difficult to obtain an accurate Thevenin equivalent impedance at the point where distributed resources are linked, the effect cannot be considered very good. If the distributed resource can directly grasp the characteristics of the connection point and find the basic values that can set the droop curve or power factor control command, and if the optimal control command can be received through interlocking with the upper system, the overall system stabilization effect. Will also increase.

Therefore, the present invention report proposes a method for autonomously setting the Q-V droop curve, the power factor control command, and the Q-P droop curve in the inverter.

As described above, the voltage stabilization effect due to the reactive power control of the distributed resource is determined by R and X of the Tevennon equivalent impedance viewed from the connection point of the distributed resource. In general, in a distribution line having a radial structure, when distributed resources are connected near a substation and connected to an end of a distribution line, the voltage control effect according to the control of reactive power may be very different. (Generally, the ratio of R and X is called X/R Ratio, and it means the value of X divided by R.) The reason is that the X/R Ratio of the transmission line is very large, and the lower the X/R ratio of the distribution line goes toward the end. This is because more and more R Ratio characteristics are included. In addition, the degree of voltage fluctuation according to the fluctuations of the active and reactive power of the distributed resource is ultimately determined by the impedance (Z) in which R and X values are mixed, and the size of this Z is generally the short-circuit impedance of the distribution line. it means. If the short-circuit impedance of the distribution line is large, the voltage fluctuation caused by the fluctuations of the active and reactive power of the distributed resource will be large, and if the short-circuit impedance is small, the fluctuation of the voltage caused by the fluctuation of the active or reactive power. This will be small. Therefore, the magnitude of the short-circuit impedance is also expressed as the strength of the system. In other words, when the short-circuit impedance is small, the system is a system that is resistant to voltage fluctuations. However, there is a disadvantage in that the short-circuit current is large during short circuit.

In fact, since the short-circuit impedance of a distribution line is a numerical value that can represent the degree of voltage fluctuation according to fluctuations in active power and reactive power, it is not very closely related to the effect of controlling reactive power due to fluctuations in active power of distributed resources. Therefore, it is important to accurately know the X/R ratio for each location of distributed resource connection of the distribution line. If you know the correct X/R ratio (again), you can know the degree of voltage fluctuation according to the fluctuation of active power as shown in the following equation. It is also possible to know the amount of reactive power to be supplied or absorbed in order to become zero.

In the end, a method of estimating the X/R ratio is proposed in the present invention report, and the command for power factor control is calculated using the X/R ratio learned so that a Q-V Droop curve and a Q-P Droop curve are created.

The method of obtaining the X/R Ratio of the connection point of distributed resources can be surprisingly simple. (Again) The linkage point X/R Ratio of the distributed resource can be obtained through the formula below. The distributed resource arbitrarily controls the active and reactive power, and measures the voltage at the linkage point of the distributed resource according to the magnitude of the voltage fluctuation. This is how to find R and X.

First, there is a method of using the step variation of the output.

First of all, it is necessary to change the active power to obtain the X/R ratio of the linkage point. Assuming that there is no variation in reactive power, the voltage variation according to the variation in active power can be determined by the following equation.

That is, if the initial voltage when there is no change in the active power of the distributed resource linkage point is E0, and the voltage after the active power is output is E1, it becomes. That is, if the distributed resource can know the magnitude of the voltage fluctuation before and after the injection of the active power by the amount of the active power fluctuation, R can be calculated.

In the same way, X can also be obtained through the supply or absorption of reactive power using [Equation 3].

At this time, since the distribution system load fluctuates while the distributed resource fluctuates the active power and the reactive power, and the output fluctuations of the surrounding distributed resources also occur, the voltage fluctuations generated in this method are entirely caused by the output of the distributed resources. It is difficult to say that it will be. However, since the time constant for the output control of the distributed resource is due to a very short time in ms units, if the output of the distributed resource is changed to a step, the voltage fluctuation due to the step change can be prevented if the measured value of the short time can be caught. Can be seen, and the R and X values at that time can be calculated.

However, if R and X values are estimated through only one output fluctuation and calculation, it cannot be considered to represent the same R and X values in all output intervals (theoretically they should be the same). And X values can be finally determined in the following ways.

For example, the active power and reactive power may be changed in several steps to determine the average of the calculated R and X values. As another example, an intermediate value may be taken by listing several calculated R and X values in order of magnitude. As another example, it may be determined as an average of the remaining values excluding the calculated R values and 5 to 10% of the upper and lower values of the X values.

The final X/R ratio can be determined by performing X divided by R using the finally determined R and X values.

On the other hand, there is a method of sequentially injecting and calculating the same amount of active power and reactive power.

If the size of the active power and the reactive power supplied by the distributed resource are the same, that is, if the sizes of △P and △Q are the same, then the X/R ratio can be calculated by using the voltage fluctuation of Q and A by [Equation 4]. You can get it.

At this time, when supplying active power and reactive power at the same time, the voltage fluctuations due to and cannot be fully verified. Therefore, the same active power and reactive power must be sequentially generated, and the voltage fluctuations according to them must be calculated. Since the basic initial voltage may fluctuate over time, some errors may occur. However, even if the initial voltage fluctuation occurs, if the magnitude of the voltage fluctuation can be accurately measured, the R and X values will be the same.

On the other hand, there is a method of using a voltage restoration (return to the original voltage) examination.

One of the active power and reactive power output from the distributed resource is fixed (generally, the active power is not fixed or controlled) and the other is controlled to find the values where the voltage fluctuation becomes zero, and then the X/R ratio can be calculated. have. In other words, when the active power and the reactive power (absorbed) are not 0, and find a pair of active power and reactive power whose voltage change becomes 0, the X/R ratio can be calculated as shown in [Equation 5]. .

It can be calculated by calculating the X/R Ratio as the amount of change in active power and reactive power at the moment when the voltage change becomes zero.

It is also possible to calculate the X/R Ratio by mixing the various methods described above.

In fact, if you know exactly the X/R ratio through the above invention proposal, you can solve very one-dimensionally how to create the power factor control command for power factor control, how to create a QV droop control curve, and how to create a QP droop control curve. . Furthermore, it is possible to increase the flexibility of control by giving several modified points in the method of controlling distributed resources to which this patent is applied.

As an example, there is a method of making a command for power factor control. If the X/R ratio of the point to which the distributed resource is linked is known, the power factor command required for the distributed resource to control the voltage fluctuation to zero can be calculated based on [Equation 7] using the following equation.

As another example, there is a method of creating a curve for Q-V Droop control.

As shown in Fig. 5, the QV droop control of the distributed resource uses four points of V1, V2, V3, and V4 to create a QV droop curve by itself in the distributed resource, and the curve function is applied according to the fluctuation of the voltage of the distributed resource connection point. It can supply/absorb the right reactive power. In other words, when the upper control system transmits V1, V2, V3, V4 and DB (dead band, dead band) to the distributed resource, the distributed resource can be controlled by creating a curve suitable for the figure below.

If the distributed resource can make V1, V2, V3, V4 by itself, the distributed resource can make a Q-V droop curve by itself.

The start of making the four points of distributed resources V1, V2, V3, and V4 can be started with the four X/R ratio estimation methods proposed in the present invention. Through the above four methods, the equivalent impedance of R and X, which is effective for control viewed from the distributed resource linkage point, and the X/R ratio can be obtained. If you know the equivalent impedances R and X viewed from the connection point, you can obtain V4 using [Equation 7].

Where is the reactive power in Per unit, is the rated voltage in Volt, is the rated active power, is reactance in ohm, is the junction voltage (or V4 point voltage) in Per unit, and DB is dead in per unit. Large, lastly, refers to the slope adjustment variable. In general, it can be set to 1 unless there is a separate command from the upper system.

The method of obtaining V4 can be obtained by using the maximum reactive power that the distributed resource can generate as an input, or by using the maximum value of the allowable voltage range of the distribution system. However, due to the presence of a dead zone, compensation for reactive power according to fluctuations in active power may not be accurate. Therefore, it is possible to change the slope of the Q-V droop curve by adjusting, and it should be possible to determine whether to create a curve with the maximum reactive power magnitude or the maximum voltage allowable range.

There are three ways to get V3. One is to receive the DB determined by the upper level controller and substitute it in [Equation 7] to obtain Vm.pu whose Qpu becomes 0. The second is to find Vm.pu whose Qpu becomes 0 as an input if DB is set in the distributed resource itself. Finally, if you input the internal resistance R of the transformer for connection of distributed resources, it is set as much as the voltage increase in the rated output condition of the distributed resource. For example, in the formula below, if R is calculated as the transformer's internal resistance R, you can find at the rated output P condition, and converting this to per unit unit will give you. At this time, it is assumed that the reactive power is 0 in order to designate the DB only for the voltage fluctuation due to the active power.

6 is a diagram for explaining a method of creating a curve for Q-P Droop control.

Like the Q-V droop control, the voltage of the distributed resource connection point can be controlled through the Q-P control curve. The Q-P droop curve is a control method for stabilizing the voltage of the distributed resource connection point by supplying/absorbing reactive power (Q) according to the fluctuation of active power (P). QP droop control is to supply/absorb reactive power according to the change of active power of the distributed resource itself by setting P1, P2, P3, P4 as shown in the figure below and by creating a droop curve for the distributed resource itself, so select P1, P2, P3, P4. This is important.

The start of making the four points of distributed resources P1, P2, P3, and P4 can also be started with the four X/R ratio estimation methods proposed in the present invention report. Through the above four methods, the equivalent impedance of R and X, which is effective for control viewed from the distributed resource linkage point, and the X/R ratio can be obtained. If you know the equivalent impedances R and X viewed from the connection point, P4 can be obtained using [Equation 10] below.

Here, Q _pu is the reactive power in Per unit, X is the reactance in ohm, R is the resistance in ohm, P _m-pu is the active power of the connection point in Per unit (or P4 point active power), and DB is per The dead band in units, and finally, the slope adjustment variable. In general, it can be set to 1 unless there is a separate command from the upper system.

The method of obtaining P4 can be obtained by determining the compensation slope according to the X/R ratio at the point of connection of the distributed resource and using the size of the maximum reactive power that the distributed resource can generate as an input, or reaching the rated reactive power from the rated active power. You may be asked to do it. However, due to the presence of a dead zone, compensation for reactive power according to fluctuations in active power may not be accurate. Therefore, it is possible to change the slope of the Q-V droop curve by adjusting, and it should be possible to determine whether to make the curve with the maximum reactive power size or to reach the rated reactive power from the rated active power.

There are three ways to get P3. One is to receive the DB determined by the upper level controller and substitute it into the above equation to find _{P m-pu where Q pu} becomes 0. The second is to find _{P m-pu whose Q pu} becomes 0 as an input if DB is set in the distributed resource itself. Lastly, this is a method of setting the amount of active power loss caused by the transformer for linkage of distributed resources as DB (Dead Band). For example, in [Equation 11] below, if R is calculated as the internal resistance R of the transformer, the current I of the distributed resource can be obtained under the condition of the rated voltage V, and this can be obtained by converting it into units of per unit.

The deadband can be set to 0.

P1 can be obtained in the same way as P4 is obtained, and P2 can be obtained in the same way as P3. At this time, the following [Equation 12] is used to obtain P1 and P2.

FIG. 7 is a diagram for explaining an upper level controller for power factor control and a control structure of distributed resources.

Distributed resources or devices that function as a system assistant linked to distributed resources receive a value from the upper control system and calculate the power factor command through a formula that calculates the power factor command, and the power factor command is transmitted by receiving a set from the distributed resource itself. The power factor command is also calculated through a formula that calculates the command.

At this time, the range of a is 0.1-10, and the X/R ratio can be changed up to 0.1-10 times at the distributed resource linkage point. At this time, D(P) is -1 or 1, and it is determined whether the power factor of the distributed resource is to be advanced or ground according to the direction of the active power output of the distributed resource.

In one embodiment, the higher-level control system (distribution operation system, DMS) can obtain the Tevennon equivalent X/R ratio of the linkage point to which distributed resources are linked through failure analysis of the study mode at the level of distribution planning. Therefore, although the X/R ratio can be used by the distributed resource itself, it is also possible to generate a power factor control command using the X/R ratio transmitted from the upper control system and transmitted by the upper control system.

If the distributed resource can estimate the effective X/R ratio by itself, it can generate an accurate power factor command necessary to stabilize the voltage increased due to active power as shown in [Equation 13] below.

However, just because this power factor command makes the voltage rise to zero is not unconditionally good. For example, when the entire distributed resource needs to be cooperatively controlled by the upper level controller, or when the voltage-reactive power optimization (Volt-Var Optimization) of the distribution system is performed by the distribution operating system, the distributed resources are subject to the optimal power factor command. In addition, it needs to be controlled by receiving the command from the upper level controller. In addition, if the power factor command by the X/R ratio estimated by the distributed resource is not the optimal power factor command due to the estimation error, the power factor command must be adjustable, so the following [Equation 14] including the adjustment variable a is used. You can make a power factor command.

When the inverter of the distributed resource generates and controls the power factor command using [Equation 14], the control structure with the upper control system is shown in FIG. 7.

Distributed resources or devices that function as a system assistant linked to distributed resources receive a from the upper control system and calculate the power factor command through a formula that calculates the power factor command, and by receiving a set from the distributed resource itself, the power factor The power factor command is also calculated through a formula that calculates the command. At this time, the range of a is 0.1 to 10, and the X/R ratio can be changed up to 0.1 to 10 times at the distributed resource linkage point. At this time, D(P) is ?1 or 1, and it is determined whether the power factor of the distributed resource is to be advanced or ground according to the direction of the active power output of the distributed resource.

The higher-level control system (distribution operation system, DMS) can obtain the Tevennon equivalent X/R ratio of the connection point to which distributed resources are linked through failure analysis of study mode at the level of distribution planning. Therefore, the X/R ratio can be used by the distributed resource itself, but it must also be able to generate a power factor control command using the X/R ratio transmitted by the upper control system after receiving it from the upper control system.

FIG. 8 is a diagram for explaining a control structure of a high-level controller and distributed resources for creating a Q-V droop curve, and FIG. 9 is a diagram for explaining voltage fluctuations for each distance of a general distribution line in a line with only a load.

Four variables are needed to make the Q-V droop curve of distributed resources. That is, in order to make these variables, as shown in Fig. 11, ① the step of determining the dead band (floating band) of the Q-V droop curve, ② the scale factor (a) for the X/R ratio of the distribution system viewed from distributed resources. It includes the step of determining, ③ determining the reference voltage (generally rated 1pu) of the Q-V droop curve, and ④ determining the X/R ratio of the distribution system viewed from the distributed resource.

More specifically, if you look at the configuration ① that determines the dead band of the Q-V droop curve (floating band), setting the DB to create the Q-V droop curve of the distributed resource can be performed in the upper control system and the control structure of the distributed resource.

At this time, the DB may be determined by a method of setting the distributed resource using a human machine interface (HMI) by itself, a method of receiving and inputting a transmission from an upper level controller, and a method of automatically calculating the internal resistance R in consideration of the transformer.

In addition, the configuration ② that determines the scale factor (a) for the X/R ratio of the distribution system viewed from distributed resources can be performed in the upper control system and the control structure of the distributed resources.

The curve to determine the Q-V droop curve uses a method of finding a point mathematically based on when DB is 0. However, this method of calculating the slope cannot ideally compensate for the entire output area according to the X/R ratio estimated at the distributed resource linkage point due to the DB.

Therefore, it can be controlled by receiving commands from the host control system by using a scale factor of a, or by using the HMI (Human Machine Interface) itself from distributed resources.

And the configuration that determines the reference voltage (generally 1pu rating) of the QV droop curve ③ For analysis of study mode at the level of distribution planning or VVO (Volt-Var Optimization) control at the operation level by the upper control system (DMS, etc.) It can be mainly analyzed, but if the distributed resources act individually, the voltage immediately before the connection of the distributed resources (voltage when the effective output is 0kW) _{can be set as V ref} and control can also be performed.

In addition, the configuration ④ that determines the X/R ratio of the distribution system viewed from the distributed resource is the upper control system (distribution operation system, DMS) is a frame of the linkage point where the distributed resources are connected through failure analysis of the study mode at the level of distribution planning. You can find the Bnan equivalent X/R ratio. Therefore, it is possible to create a Q-V droop curve by using the X/R ratio transmitted from the upper control system and transmitted by the upper control system, or by estimating the X/R ratio by the distributed resource itself.

In the case where there is no distributed resource in the distribution line, a voltage fluctuation trend of a general distribution line in consideration of the voltage drop generated only by the load is as shown in the solid black line of FIG. 9.

In the voltage characteristics of such a distribution line, if the distribution source is assumed to be connected to the blue linkage point, unnecessary reactive power must be supplied steadily if the distributed residual source operates to maintain the voltage of 1PU at the linkage point with a relatively low voltage. In some cases, there may be situations in which the desired reactive power cannot be supplied due to insufficient capacity. Therefore, if you can _{(again) change V ref} as shown in the figure below, distributed resources will be able to respond appropriately based on _{the V ref.}

At this time, Vref can be analyzed mainly for study mode analysis at the level of distribution planning or VVO (Volt-Var Optimization) control at the operation level by higher level control systems (DMS, etc.), but distributed resources are individually In the case of responsiveness, the voltage immediately before the connection of the distributed resource (the voltage when the effective output is 0kW) is set as Vref and can be controlled.

The higher-level control system (distribution operation system, DMS) can obtain the Tevennon equivalent X/R ratio of the connection point to which distributed resources are linked through failure analysis of study mode at the level of distribution planning. Therefore, the X/R ratio can be used by the distributed resource itself, but the Q-V droop curve must be generated using the X/R ratio transmitted by the upper control system after receiving it from the upper control system.

10 is a diagram for explaining a control structure of an upper level controller and distributed resources for creating a Q-P droop curve.

Three variables are needed to create the Q-P droop curve of distributed resources. Specifically, the QP droop curve generation method of distributed resources is the step of determining the dead band (floating band) of the QP droop curve (⑤), and the scale factor (a) for the X/R ratio of the distribution system viewed from the distributed resource. It includes the step (⑥) and the step (⑦) of determining the X/R ratio of the distribution system viewed from the distributed resource.

Specifically, the step of determining the dead band (floating band) of the QP droop curve (⑤) can be performed in the upper control system and the control structure of the distributed resource to set the DB for creating the QP droop curve of the distributed resource. . At this time, the DB is a method of setting up using the Human Machine Interface (HMI) by itself from distributed resources, a method of receiving and inputting the transmission from a host controller, and a method of automatically calculating the voltage drop in the transformer according to the rated effective output Can be determined.

In addition, the step (⑥) of determining the scale factor (a) for the X/R ratio of the distribution system viewed from the distributed resource can be performed in the upper control system and the control structure of the distributed resource.

Actually, the curve for determining the Q-P droop curve uses a method of finding a point mathematically based on when the DB is 0. However, this method of calculating the slope cannot ideally compensate for the entire output area according to the X/R ratio estimated at the distributed resource linkage point due to the DB. Therefore, it must be able to control by using a scale factor of a to receive commands from the host control system or by using the HMI of distributed resources.

The step (⑦) of determining the X/R ratio of the distribution system viewed from the distributed resource may be performed by the upper control system or the distributed resource itself. The higher-level control system (distribution operation system, DMS) can obtain the Tevenan equivalent X/R ratio of the linkage point to which distributed resources are connected through failure analysis of study mode at the level of distribution planning. Therefore, the X/R ratio can be used by the distributed resource itself, but the Q-P droop curve must be generated using the X/R ratio transmitted by the upper control system after receiving it from the upper control system.

The higher-level control system (distribution operation system, DMS) can obtain the Tevennon equivalent X/R ratio of the connection point to which distributed resources are linked through failure analysis of study mode at the level of distribution planning. Therefore, the X/R ratio can be used by the distributed resource itself, but the Q-P droop curve must be generated using the X/R ratio transmitted by the upper control system after receiving it from the upper control system.

Currently, the number of distributed resources connected to the distribution system is about 420,000 as of 2018.

In 2018, about 50,000 distributed resources are experiencing connection delays.

In order to achieve the government's regeneration e 3020 implementation plan, the capacity of additional distributed resources to be connected to the distribution system is estimated to be about 27GW, which is about three times the capacity of 10GW connected to the current distribution system.

Currently, distributed resources are mostly connected to the distribution system, causing overvoltage in distribution lines by changing the direction of the electric current, and frequent output fluctuations of distributed resources affect the customer's electricity quality. Therefore, as the linkage capacity of distributed resources increases, the importance of voltage stabilization of distribution lines using distributed resource control will increase.

Here, it is necessary to examine whether it is possible to directly manage all distributed resources linked to the distribution system. Except for about 45,000 of the distributed resources linked to the distribution system, most are offset transactions distributed resources. In other words, it may mean that the number of distributed resources to be managed and monitored is currently about 45,000. If the 2030 Regeneratione Implementation Plan is achieved, the number of distributed resources to be managed could increase significantly, exceeding 100,000. Currently, the number of 100kW-class distributed resources accounts for about 40% of the 45,000 accumulated distributed resources. Here, we must consider whether we should directly control and monitor 100kW-class distributed resources using the distribution operation system. Of course, monitoring should be performed, but if it is controlled directly, the investment cost for the hardware platform performance of the distribution operating system will not be neglected. Therefore, if small-capacity distributed resources autonomously create and act on the control of distributed resources, a very effective distribution operation structure can be obtained.

Suppose that the number of distributed resources to be managed in 2030 is 100,000 units, and at this time, the number of distributed resources with a capacity of 100 kW or less is 70%. If the distribution operation system does not directly control the distributed resource by itself using the methods proposed in the present invention patent, and if the investment cost of the control facility invested in one distributed resource can be reduced by 1,000,000 won, about 70,000 units are distributed. The amount that can be saved from resources will be about 70 billion.

If distributed resources less than 100kW are not the target, but all distributed resources linked to the low-voltage system are controlled for autonomous operation, the economic effect will increase further.

In addition, when 70,000 distributed resources are used for autonomous operation control proposed in the present invention patent, it is possible to additionally contribute to system stabilization, thereby reducing the cost of equipment investment for compensating the electric quality of customers, and stabilization of the distribution system voltage. As it is possible to increase the capacity of the hosting capacity according to the following, it is possible to reduce the investment cost for new expansion of distribution facilities by linking distributed resources.

11 is a flowchart of a method for autonomous voltage control of distributed resources performed in a distributed resource control system according to an embodiment of the present invention.

In one embodiment, the voltage of the distributed resource linkage point is measured by controlling the supply of at least one of active power or reactive power (S400), and resistance value (R) or reactance is performed using the measured voltage fluctuation value of the linking point. Determine the value (X) (S410).

Then, the reactance and the resistance ratio (X/R ratio) are estimated according to the recognized resistance value R or the reactance value X (S420).

The voltage stabilization effect according to the reactive power control of the distributed resource is determined by the R and X values of Thevenin equivalent impedance viewed from the connection point of the distributed resource. The ratio of R and X is called X/R Ratio, and it means the value obtained by dividing X by R. In general, in a distribution line having a radial structure, the voltage control effect due to the control of reactive power is very different when distributed resources are connected near a substation and when connected to an end of a distribution line. The reason is that the X/R Ratio of the transmission line is very large, and the lower the X/R Ratio characteristic of the distribution line is more and more included as it goes toward the end.

In addition, the degree of voltage fluctuation according to the fluctuations of the active and reactive power of distributed resources is determined by the impedance (Z) in which R and X values are mixed, and the magnitude of the impedance (Z) is generally the short circuit impedance of the distribution line. Means.

If the short-circuit impedance value of the distribution line is large, voltage fluctuations caused by fluctuations in active and reactive power of distributed resources will be large. On the other hand, if the short-circuit impedance is small, the voltage fluctuation caused by the fluctuation of the active power or the reactive power will be small.

Therefore, in general, the magnitude of the short-circuit impedance is also expressed as the strength of the system. That is, when the short-circuit impedance is small, the system is a system that is resistant to voltage fluctuations. However, there is a disadvantage in that the short-circuit current is large during short circuit.

12 is a flowchart of a method for controlling an autonomous voltage of a distributed resource for generating a Q-V Droop curve performed in a distributed resource control system according to an aspect of the present invention.

The autonomous voltage control method of distributed resources for generating a QV droop curve performed in the distributed resource control system according to an embodiment is to determine the dead band (floating band) of the QV droop curve (S600), and distribution viewed from the distributed resource. The scale factor (a) for the system's X/R ratio is determined (S610). Then, after determining the reference voltage value of the Q-V droop curve (S620), the reactance and resistance ratio (X/R ratio) of the distribution system viewed from the distributed resource are determined (S630). The characteristic values V1, V2, V3, and V4 of the Q-V Droop curve are calculated using the determined reactance and resistance ratio (X/R ratio) (S640).

After the X/R ratio value is estimated, the method of making the command for power factor control is as follows.

When the X/R ratio of the point to which the distributed resource is linked is known, the power factor command required for the distributed resource to control the voltage fluctuation to zero can be calculated using [Equation 6].

13 is a flowchart of a method for controlling autonomous voltage of distributed resources for generating a Q-P droop curve according to an embodiment of the present invention.

In the autonomous voltage control method of distributed resources that generates a QP droop curve performed in the distributed resource control system according to an embodiment, the dead band of the QP droop curve is determined (S800), and the distribution system viewed from the distributed resource. The scale factor (a) for the X/R ratio of is determined (S810).

Then, after determining the reference active power of the Q-P droop curve (S820), the reactance and resistance ratio (X/R ratio) of the distribution system viewed from the distributed resource are determined (S830). After that, a characteristic value of the Q-P Droop curve is calculated using the determined reactance and resistance ratio (X/R ratio) (S840).

The present invention can be implemented as a computer-readable code on a medium on which a program is recorded. The computer-readable medium includes all types of recording devices that store data that can be read by a computer system. Examples of computer-readable media include hard disk drives (HDDs), solid state disks (SSDs), silicon disk drives (SDDs), ROMs, RAM, CD-ROMs, magnetic tapes, floppy disks, optical data storage devices, etc. There is also a carrier wave (for example, transmission over the Internet) also includes the implementation of the form. In addition, the computer may include a terminal.

Therefore, the detailed description above should not be construed as restrictive in all respects and should be considered as illustrative. The scope of the present invention should be determined by reasonable interpretation of the appended claims, and all changes within the equivalent scope of the present invention are included in the scope of the present invention.

100: distributed power grid system
110: control center
120: power grid
122: distribution control
124: customer
130: distributed resources

Claims (23)

A method for controlling a computing device for controlling distributed resources supplying active power from a first point to a second point through a line, comprising:
Calculating a ratio of resistance (R) and reactance (X) of the line; And
Adjusting reactive power supplied or absorbed to the line based on the ratio
Including,
The step of calculating the ratio,
Changing the active power while maintaining the reactive power within a certain range;
Measuring a first variation in voltage corresponding to the variation in active power;
Calculating resistance of the line based on the first change amount;
Changing the reactive power while maintaining the active power within a certain range;
Measuring a second variation in voltage corresponding to the variation in reactive power;
Calculating reactance of the line based on the second change amount; And
Calculating the ratio by dividing the resistance by the reactance
Control method comprising a. The method of claim 1,
Calculating a power factor command for controlling the voltage fluctuation of the distributed resource to zero based on the ratio; And
And transmitting the power factor command to the distributed resource. The method of claim 2,
The step of calculating the power factor command,
Setting an adjustment variable for the distributed resource; And
And calculating the power factor command based on the adjustment variable and the ratio. The method of claim 3,
The control method, characterized in that the adjustment variable varies according to the distributed resource. The method of claim 1,
Defining an equation between the voltage of the distributed resource and the reactive power based on the ratio;
Measuring the voltage of the distributed resource;
And adjusting the reactive power so that the reactive power corresponds to the measured voltage in the equation. delete The method of claim 1,
The step of calculating the ratio,
Supplying the active power of a predetermined size to the line by using the distributed resources;
Measuring a first voltage immediately before supplying the active power of the predetermined size;
Supplying the reactive power of the predetermined size to the line by using the distributed resources;
Measuring a second voltage immediately before supplying the reactive power of the predetermined size; And
And calculating the ratio using the first voltage and the second voltage. The method of claim 1,
The step of calculating the ratio,
Fixing an amount of effective power supplied to the line by the distributed resource;
Adjusting the amount of reactive power supplied to the line by the distributed resource while the amount of active power is fixed, and searching for a target amount of reactive power whose voltage fluctuation becomes zero; And
And calculating the ratio by using the amount of active power and the amount of target reactive power. In the autonomous voltage control method of distributed resources performed in a distributed resource control system,
Controlling supply of at least one of active power and reactive power;
Measuring the voltage of the distributed resource linkage point;
Determining a resistance value (R) or a reactance value (X) using the measured voltage fluctuation value of the connection point; And
Estimating reactance and resistance ratio (X/R ratio) according to the recognized resistance value (R) or reactance value (X)
Including,
Controlling the supply of at least one of the active power and the reactive power,
Changing the active power while maintaining the reactive power within a certain range; And
Changing the reactive power while maintaining the active power within a certain range
Including,
Measuring the voltage of the distributed resource connection point,
Measuring a first variation in voltage corresponding to the variation in active power; And
Measuring a second variation in voltage corresponding to the variation in reactive power
Including,
The reactance is calculated based on the second change amount. The method of claim 9,
In the controlling step, the reactive power is fixed and the supply value of the active power is changed,
The step of grasping,
Equation

Calculate the difference between the voltage (E _{1 ) after the active power is output by applying and the initial voltage (E 0} ) when there is no active power fluctuation, and substitute it for ΔV, and the amount of active power fluctuation before and after the injection of active power is calculated Substituting for ΔP to determine the resistance value (R). The method of claim 10,
The controlling step outputs a plurality of different active power values,
The determining step is to determine a plurality of resistance values R by applying voltage values measured after outputting the plurality of different active power values,
The step of estimating the reactance-resistance ratio (X/R ratio) comprises estimating a reactance-to-resistance ratio (X/R ratio) using an average value of at least some of the plurality of identified resistance values. A method of autonomous voltage control of resources. The method of claim 10,
The controlling step outputs a plurality of different active power values,
The determining step is to determine a plurality of resistance values R by applying voltage values measured after outputting the plurality of different active power values,
The step of estimating the reactance and resistance ratio (X/R ratio) is characterized by estimating the reactance-to-resistance ratio (X/R ratio) by listing the plurality of identified resistance values in order of magnitude and taking an intermediate value thereof. Autonomous voltage control method of distributed resources. The method of claim 9,
In the controlling step, the active power is fixed and the supply value of the reactive power is changed,
The step of grasping,
Equation

Calculate the difference between the voltage (E _{1 ) after the reactive power is output by applying and the initial voltage (E 0} ) when there is no change in reactive power, and substitute it for ΔV, and the amount of change in reactive power due to the supply or absorption of reactive power Substituting ΔQ to determine the reactance value (X). The method of claim 9,
In the controlling step, active power and reactive power of the same size are supplied,
The step of estimating the reactance and resistance ratio (X/R ratio),
Equation

Autonomous voltage control method of distributed resources, characterized in that estimating reactance and resistance ratio (X/R ratio) by applying. The method of claim 9,
The controlling step,
The active power is fixed and the supply value of the reactive power is changed, and the supply value of the reactive power at which the voltage fluctuation of the connection point becomes zero is found,
The step of estimating the reactance and resistance ratio (X/R ratio),
Equation

Autonomous voltage control method of distributed resources, characterized in that estimating reactance and resistance ratio (X/R ratio) by applying. In the autonomous voltage control method of distributed resources that generates a QV Droop curve performed in a distributed resource control system,
Determining a dead band (floating band) of the QV droop curve;
Determining a scale factor (a) for the X/R ratio of the distribution system viewed from distributed resources;
Determining a reference voltage value of the QV droop curve;
Determining the reactance and resistance ratio (X/R ratio) of the distribution system viewed from the distributed resource; And
Computing a characteristic value of a QV Droop curve using the determined reactance and resistance ratio (X/R ratio). The method of claim 16,
The step of calculating the feature value,
Equation

Autonomous voltage control method of distributed resources for generating a QV Droop curve, characterized in that calculating the connection point voltage (V4) by applying. The method of claim 16,
The step of calculating the feature value,
Equation

Autonomous voltage control method for distributed resources generating a QV Droop curve, characterized in that the determined Dead Band (floating band) value is substituted into and _{a V m·pu value (v3) at which Q pu} becomes 0 is calculated. The method of claim 16,
The step of calculating the feature value,
Equation

To calculate V1 by applying
Equation

Autonomous voltage control method of a distributed resource for generating a QV Droop curve, characterized in that the determined dead band (floating band) value is substituted to and _{a V m·pu value (V2) at which Q pu} becomes 0 is calculated. In the autonomous voltage control method of distributed resources that generates a QP droop curve performed in a distributed resource control system,
Determining a dead band (floating band) of the QP droop curve;
Determining a scale factor (a) for the X/R ratio of the distribution system viewed from distributed resources;
Determining a reference active power of the QP droop curve;
Determining the reactance and resistance ratio (X/R ratio) of the distribution system viewed from the distributed resource; And
Computing a characteristic value of a QP droop curve using the determined reactance and resistance ratio (X/R ratio). The method of claim 20,
The step of calculating the feature value,
Equation

Autonomous voltage control method of distributed resources for generating a QP droop curve, characterized in that calculating the linkage point active power (P4) by. The method of claim 20,
The step of calculating the feature value,
Equation

Autonomous voltage control method for distributed resources generating a QP droop curve, characterized in that the determined Dead Band (floating band) value is substituted and _{a P m·pu value (P3) at which Q pu} becomes 0 is calculated. The method of claim 20,
The step of calculating the feature value,
Equation

To calculate P1 by applying
Equation

Autonomous voltage control method of distributed resources for generating a QP droop curve, characterized in that the determined Dead Band (floating band) value is substituted into and _{a V m·pu value (P2) at which Q pu} becomes 0 is calculated.

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