KR20240120623A - ESS Charging and Discharging Control System and Method using the Same - Google Patents

Abstract

This document is about the ESS (Energy Storage System) charge/discharge control system and the ESS charge/discharge control method using it.
To this end, the charge/discharge control system includes an ESS equipped with a battery; A power conversion device (PCS) connected to a power grid and the ESS to convert the form of power between the power grid and the ESS; And when the first power section based on the power conversion efficiency of the power conversion device and the second power section based on the charging and discharging efficiency of the battery are different, controlling to charge and discharge the battery with power within the first power section. It is characterized in that it includes a controller that.

Description

ESS charging and discharging control system and charging and discharging control method using the same {ESS Charging and Discharging Control System and Method using the Same}

The following description is about the charging and discharging control system of the ESS (Energy Storage System) and the ESS charging and discharging control method using the same. Specifically, the ESS charging is performed by first considering the power section based on the power conversion efficiency of the power conversion device (PCS). This relates to a method and system for efficiently controlling discharge.

Recently, as the use of electric vehicles (EVs) has expanded, electric vehicle chargers are being placed in various spaces. However, the use of electric vehicle chargers increases electricity usage on the grid and can affect other electricity usage in the space. In particular, when electricity usage increases rapidly, there is a problem that the use of electric vehicle chargers is limited.

In addition, various electric mobility devices such as UAV (Uncrewed Aerial Vehicle) and personal mobility are being proposed as mobility devices that require battery charging, in addition to current electric vehicles.

Accordingly, a power system including ESS has been proposed to stably charge the various electric mobile devices described above in a space where a charger is placed and to support this.

However, in the case of lithium ion batteries (LIBs), which are currently the most popular, a limited charging rate is applied considering battery safety when applied to ESS, which has the problem that it is impossible to derive the optimal charge/discharge efficiency for the power system including ESS.

In order to solve the problems described above, in one aspect of the present invention, a method and system for efficiently controlling ESS charging and discharging are proposed by prioritizing the power section based on the power conversion efficiency of the power conversion device (PCS). I want to do it.

In addition, in a preferred embodiment of the present invention, in order to perform charging and discharging by first considering the power section of the power conversion device, the requirements for a suitable battery are examined and a charging and discharging control system using these is proposed.

The problems to be solved by the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art from the description below. You will be able to.

In one aspect of the present invention for solving the problems described above, an ESS including a battery; A power conversion device (PCS) connected to a power grid and the ESS to convert the form of power between the power grid and the ESS; And when the first power section based on the power conversion efficiency of the power conversion device and the second power section based on the charging and discharging efficiency of the battery are different, controlling to charge and discharge the battery with power within the first power section. We propose an ESS charge/discharge control system characterized by including a controller.

In addition, in another aspect of the present invention, in a method of controlling battery charging and discharging of an ESS, a method based on the power conversion efficiency of a power conversion device (PCS) that converts the power form between a power grid and the ESS Compare the first power section with a second power section based on the charging and discharging efficiency of the battery; We propose an ESS charging and discharging control method, which includes performing charging and discharging of the battery with power within the first power section when the first power section and the second power section are different.

According to the embodiments of the present invention as described above, power loss in the power conversion device (PCS) can be minimized by preferentially considering a power section based on the power conversion efficiency of the power conversion device (PCS).

In addition, in a preferred embodiment of the present invention, the safety and power efficiency of the ESS can be pursued at the same time by using a battery that does not cause problems with the safety of the battery even when charging and discharging is performed by first considering the power section of the power conversion device.

The effects that can be obtained from the present invention are not limited to the effects mentioned above, and other effects not mentioned can be clearly understood by those skilled in the art from the description below. will be.

1 and 2 are diagrams for explaining the power conversion efficiency of the power conversion device.
Figure 3 is a diagram to explain power loss when LIB is applied to ESS.
Figure 4 is a diagram for explaining the concept of an ESS charging/discharging control system according to an embodiment of the present invention.
Figure 5 is a diagram for explaining the battery type applied to the ESS according to an embodiment of the present invention.
Figure 6 is a diagram for explaining the structure of VIB ESS according to an embodiment of the present invention.
Figure 7 is a diagram for explaining a charging and discharging control method using VIB ESS according to a preferred embodiment of the present invention.
Figure 8 is a diagram to explain the concept of a power section considering battery safety in charge/discharge control using VIB ESS according to another embodiment of the present invention.
FIG. 9 is a diagram illustrating a method of determining charge/discharge power according to the relationship between a first power section and a second power section according to an embodiment of the present invention.
Figure 10 is a diagram for explaining the mechanism by which ESS charging is performed according to an embodiment of the present invention.
Figure 11 is a diagram for explaining the mechanism by which ESS discharge is performed according to an embodiment of the present invention.

Hereinafter, with reference to the attached drawings, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the present invention. However, the present invention may be implemented in many different forms and is not limited to the embodiments described herein. In order to clearly explain the present invention in the drawings, parts unrelated to the description are omitted, and similar parts are given similar reference numerals throughout the specification.

Throughout the specification, when a part is said to “include” a certain element, this means that it may further include other elements rather than excluding other elements, unless specifically stated to the contrary.

Generally, ESS refers to a device that stores energy in various energy storage means and then supplies the stored power back to the grid when necessary. Among these ESSs, the ESS that uses batteries as a means of energy storage is specifically referred to as BESS (Battery Energy Storage System), but in the following description, unless otherwise specified, it is assumed that the ESS is a BESS.

Generally, ESS consists of a battery, a battery management system (BMS), a power conversion system (PCS), and an energy management system (EMS). A battery has one or more cells, a plurality of cells can form one module, and a plurality of modules can form a rack. The ESS configured in this way can be connected to the power grid, electric grid, etc. to receive power.

In the following description, the state of the battery can be representatively expressed based on the state-of-charge (SoC), and the charge/discharge speed of the battery can be explained based on the charge/discharge rate (C-Rate). You can.

First, the charging rate and/or the discharging rate of the battery can be controlled by the charging/discharging rate (C-Rate). Charge/discharge rate (C-Rate) refers to the measurement of current used to charge and/or discharge a battery. For example, discharging a specific battery at 1C-Rate or 1C means that a battery with a capacity of 10Ah (i.e., the amount of electricity when 10A (ampere) current flows for 1 hour) is fully charged and discharges at 10A for 1 hour. It means that (ampere) can be discharged.

By measuring a battery charged at a specific C-Rate, you can check its state of charge (SoC). When charging an electric vehicle using an ESS, various controls for charging can be performed by checking the SoC of the battery inside the ESS and the SoC of the battery inside the electric vehicle.

Based on this description, embodiments will be described in detail below with reference to the drawings.

1 and 2 are diagrams for explaining the power conversion efficiency of the power conversion device.

Power conversion devices include a converter that converts alternating current (AC) power into direct current (DC) power (hereinafter referred to as 'AC/DC converter') and an inverter that converts direct current (DC) power into alternating current (AC) power (hereinafter referred to as 'DC/AC'). Inverter') may be included.

Specifically, switching control is required to produce DC output by varying the AC voltage using an AC/DC converter, and Figure 1 is a diagram showing the PWM (Pulse Width Modulation) method in the AC/DC converter as voltage over time. . In FIG. 1, reference numeral 110 indicates a case of outputting low power, reference numeral 120 indicates a case of outputting medium power, and reference numeral 130 indicates a case of outputting high power.

As shown in Figure 1, it is possible to control the output power according to the switching speed, and it can be seen that the switching speed is low when outputting low power, and the switching speed is high when outputting high power.

Figure 2 is a diagram to explain the concept of resistance value according to switching speed and resulting power loss.

Specifically, reference numeral 210 represents noise generated during turn-off, and reference numeral 220 conceptualizes switching loss during turn-off.

In particular, reference numeral 220 indicates a case where the switching speed is high (Case 1) and a case where the switching speed is low (Case 2), depending on the switching speed. In the case where the switching speed is high (Case 1), the power is reduced due to a small resistance value. While the loss is small, when the switching speed is low (Case 2), it can be seen that the power loss is large due to the large resistance value.

In summary, in the case of AC/DC converters, the higher the output power, the better the efficiency.

Meanwhile, when changing DC voltage to AC voltage through a DC/AC inverter, the same switching is performed, but the grid voltage is fixed, so the output can be determined by the required power (W).

In other words, the higher the voltage, the lower the current, and the higher the voltage, the higher the efficiency.

For example, when using a DC/AC inverter with a conversion efficiency of 90%, the inverter output current (A) can be expressed as follows.

<Equation 1>

Inverter output current (A) = AC output (W)/AC voltage (V)

Inverter input current (A) = Inverter output current (A) * AC voltage (V) / (System voltage (V) * Conversion efficiency)

For example, if the battery is DC 12V and the load capacity is 220V 440W, it can be expressed as follows.

<Equation 2>

Through the above-mentioned review, it can be seen that in the case of DC/AC inverters, the higher the battery voltage, the lower the current input to the power conversion device, increasing the efficiency. This allows the battery voltage to exceed a certain level to control the efficiency of the power conversion device. You can see that this is required.

In the following description, the power section of the power conversion device determined based on one or more of the power amount based on the efficiency of the converter as described above and the voltage level based on the efficiency of the inverter as described above is referred to as the first power section. Do this.

Meanwhile, in the case of LIB, which is currently the most popular, there is a problem in that it is difficult to charge and discharge within the range of the first power section of the power conversion device described above.

Figure 3 is a drawing to explain power loss when LIB is applied to ESS.

In the example shown in FIG. 3, the power conversion device 320 can receive alternating current power from the power grid 310, convert it into direct current power, and provide it to the LIB ESS 330-1. Conversely, the LIB ESS 330-1 ) of direct current power may be converted to alternating current and provided to the power grid 310.

In the example of FIG. 3, it is assumed that the first power section, which is the optimal power section considering the efficiency of the power conversion device 320, is determined to be 50 kW to 100 kW.

However, in the case of LIB, charging and discharging is limited to a charging rate of 0.2 C - 0.5 C due to the risk of battery fire, where 1 C corresponds to 100 A. If the current voltage of the ESS is 700 V, the above charging rate limitation limits the charging and discharging rate to 14 kW - 35 kW, and Figure 3 shows the power grid 310 and the power conversion device 320 due to these LIB constraints. ) shows that power exchange between them is limited to 14 kW - 35 Kw, and charging and discharging between the power conversion device 320 and LIB ESS (330-1) is limited to 20 to 50 A.

As described above, when charging and discharging of the ESS is performed outside the first power range (50 kW - 100 kW) based on the power conversion efficiency of the power conversion device 320, power loss due to the power conversion device 320 increases. This may result in power wastage of the entire system.

Figure 4 is a diagram for explaining the concept of an ESS charging/discharging control system according to an embodiment of the present invention.

The ESS charge/discharge control system according to this embodiment includes an ESS (330) equipped with a battery; A power conversion device 320 connected to the power grid 310 and the ESS 330 and converting the form of power between the power grid 310 and the ESS 330; And when the first power section based on the power conversion efficiency of the power conversion device 320 and the second power section based on the charging and discharging efficiency of the battery are different, the battery of the ESS 330 is charged with the power within the first power section. It may include a controller (not shown) that controls discharge.

That is, when charging and discharging the battery of the ESS (330), it is proposed to control charging and discharging by giving priority to the power conversion efficiency of the power conversion device 320 over the charging and discharging efficiency of the battery. To this end, it is preferable to use the ESS (330) It is desirable that the battery applied is a battery that does not cause safety problems when charging and discharging with a current corresponding to the first power section, as shown in FIG. 3.

In addition, the battery according to a preferred embodiment of the present invention is preferably a battery whose power loss is minimized below a predetermined standard even when charging and discharging occurs outside the second power range considering the charging and discharging efficiency of the battery, This will be described in detail later.

ESS battery type

In the description of the above-described embodiments, there is no need to limit the interpretation of the battery used in the ESS to a specific type. However, as described above, there is no safety problem when the battery applied to the ESS (330) performs charging and discharging with a current corresponding to the first power section as shown in FIG. 3, and it is also desirable to consider the charging and discharging efficiency of the battery. It is desirable to have a battery whose power loss is minimized below a predetermined standard even when charging and discharging occurs outside the second power range. To this end, an ESS based on a vanadium ion battery (VIB) proposed by the present applicant will be described. .

Figure 5 is a diagram for explaining the battery type applied to the ESS according to an embodiment of the present invention.

As mentioned above, there are various types of batteries applicable to ESS, for example, lead-acid battery, lead carbon battery, NAS (Sodium Sulfur) battery, and lithium ion battery (LIB). ), flow batteries, etc. can be used. Figure 5 (A) exemplarily shows a system to which the LIB ESS (210), which is currently receiving the most popular attention among these various ESS batteries, is applied.

LIB has high energy density and power density, is about 3 times lighter than existing lead acid batteries, and is attracting attention because it can reduce space occupancy by 50-80% with high power density. In addition, it is possible to discharge 1-2% of the charge per month and maintain a long service life, and can be considered to have 5,000 battery cycles depending on the advantages and conditions of about 10 years of use.

However, in the case of LIB, when operating as an ESS, charging and discharging are performed under the basic condition of 0.2~0.5C, and when operating at a high C-rate, continuous operation is difficult due to heat generation, and it has the disadvantage of having a high risk of fire.

Additionally, in the case of alkaline and lead batteries, they are generally operated at 0.05C (= 20 hours of discharge) to avoid battery capacity degradation (performance reduction) due to heat generation.

On the other hand, VIB developed by the present applicant refers to a secondary battery that stores/releases energy electrochemically using vanadium ions as an active material. In existing vanadium-based batteries, active materials that participate in electrochemical reactions (e.g., vanadium ions, H+ cations, water, sulfuric acid, etc.) are forcibly circulated/transferred/stored by a pump operated by external power, thereby storing/storing electrical energy. On the other hand, in VIB, the active material within the cell and/or module changes and moves ions using internal electric fields, osmotic pressure, concentration difference, etc., and the active material releases energy through an electrochemical reaction within the cell and/or module. It performs a storage/release role.

In particular, in the case of VIB, charging and discharging is possible at 0.5 to 5C (MAX 10C). In addition, since it is driven using an aqueous electrolyte, it is free from fire risk and has the advantage of being able to utilize a wide range of SoCs.

Accordingly, Figure 5(B) shows a configuration in which the VIB ESS 140 using such a VIB is applied according to an embodiment of the present invention.

For example, in the case of LIB, heat generation and battery life are affected at high output, but in the case of VIB, stable high output is possible. In addition, LIB has limitations such as 1C charging and 1C discharging, but VIB is capable of controlling input and output flow with high output. For example, when a power outage occurs in the grid 110, the VIB ESS 140 controls both the grid 110 and the charger. Since assistance is possible with high output, the use of the VIB ESS (140) has the advantage of performing very efficient ESS charging and discharging management.

In particular, in the case of VIB, there is no risk of fire due to overload, so when this VIB is applied to the ESS of this embodiment, the system of the present invention is a very effective power supply system in that it can be preferably applied while ensuring safety in various auxiliary facilities. You can do it. In addition, since safe and efficient energy supply is possible through the use of VIB ESS (140), it can be used as a very effective, safe, and eco-friendly energy supply means for energy conservation, energy environment, and carbon neutrality.

Additionally, when using the VIB ESS (140) as shown in (B) of FIG. 5, the high-speed charging and discharging performance of the VIB is utilized as described above to measure the energy measured through a plurality of power meters (211, 212, and 220). Electric power can be used more efficiently. For example, when the measured value of the power meter 212, which measures the amount of power flowing into the charger, decreases rapidly, this can be supported by high-speed discharge, and the measured value of the power meter 220, which measures the amount of power flowing into the charger, decreases significantly. If it is below a predetermined standard, the VIB ESS (140) can be charged at high speed.

Meanwhile, in the case of LIB, there is an upper and lower limit voltage, so a relatively narrow voltage range (window) is used. Specifically, when LIB reaches 0 V or a severe discharge state (lower than the above lower limit voltage), dendrite material is generated, which may cause a short circuit due to damage to the separator, resulting in thermal runaway. there is.

On the other hand, in the case of VIB, there is an upper limit voltage but no lower limit voltage, so it has the advantage of being able to use a relatively wide voltage range (window). In other words, no special problems occur even if it is in a 0 V or full power state, and it can operate more flexibly depending on the measurement status of multiple watt-hour meters.

In addition, in the case of LIB, when charging and discharging cycles are repeated, there is an irreversible reaction (surface precipitation phenomenon, solid electrolyte interphase, cracking phenomenon) due to phase change, so there is a problem of capacity difference occurring during certain cycle operation, but VIB's In this case, it has the advantage of using a reversible reaction so that there is no difference between the initial capacity and the capacity after a certain cycle of operation.

Meanwhile, in the case of LIB, it is impossible to use it below 20% of the actual (theoretical) SoC by connecting it to the upper/lower limit voltage as described above, but in the case of VIB, there is no lower limit voltage, so the actual (theoretical) SoC is 20% or less. It can be used in

Here, the term actual (theoretical) SoC is a concept to distinguish it from the SoC provided by the manufacturer. For safety reasons, the manufacturer generally provides the range without safety problems as 0% - 100% of the actual SoC range. In contrast, the actual (theoretical) SoC refers to an SoC that calculates the battery's full charge as 100% and full discharge as 0%.

The main characteristics of these LIBs and VIBs can be summarized as in [Table 1] below.

LIB VIB Fire hazard height doesn't exist Charge/discharge rate 0.2-0.5C 0.5 - 5 C (Max 10 C) Voltage range Existence of upper and lower limit voltage There is an upper limit voltage, the lower limit voltage is Actual SoC operating below 20% Impossible possible Features when repeating cycle Irreversible reaction due to phase change reversible reaction

Figure 6 is a diagram for explaining the structure of VIB ESS according to an embodiment of the present invention.

As shown in Figure 6, VIB ESS also includes components such as battery, BMS, PCS, and EMS.

Specifically, the battery consists of a module in which 10-20 cells are grouped starting from the smallest cell unit, multiple modules constitute a pack, and multiple packs may constitute a system level, and in response to this structure, the BMS It may also have a hierarchical structure of cell BMS (not shown), module BMS (31; level 1), pack BMS (32; level 2), and system BMS (33; level 3).

Here, each level refers to an operation level that includes not only the above-described BMS but also other control configurations. For example, level 2 defines control with the level 1 control stage of the pack BMS 32 and control operations for the switch gear 34, and level 3 specifies the system BMS 33 and PMS 35 described above. ) can be defined. Additionally, the final level 4 may define control operations between a plurality of PMSs 35 and EMSs 36.

Here, the switch gear 34 can control the battery and power lines (contactor, precharge, fuse), and the linear IC 37 can turn on the switch 38 by receiving a command from the pack BMS 32. there is. At this time, turning on the switch = may mean performing balancing by resistance, and here the resistance may be a pattern resistor formed in a pattern of copper wires on the board.

In the embodiment described in FIGS. 5 and 6, the type of battery applied to the ESS is exemplarily described as VIB (FIGS. 5(B) and 6) in contrast to LIB (FIG. 5(A)). The type of battery applied to ESS does not need to be limited to VIB. For example, in this specification, the ESS may utilize a vanadium redox battery (VRB), polysulfide bromide battery (PSB), or zinc-bromine battery (ZBB).

Figure 7 is a diagram for explaining a charging and discharging control method using VIB ESS according to a preferred embodiment of the present invention.

In the embodiment shown in FIG. 7, the ESS charging/discharging control system includes a power conversion device 320 that converts the power form between the power grid 310 and the ESS 330-2 in the same manner as in FIGS. 3 and 4. , the first power section based on the power conversion efficiency of the power conversion device 320 was assumed to be 50 kW - 100 kW, similar to the example in FIG. 3.

However, in the example shown in FIG. 7, it is assumed that the ESS is a VIB ESS (330-2), and the VIB has a charge/discharge rate of 0.2 C - 1 C under the condition that 1C is 100 A, which corresponds to the most efficient charge/discharge section. , when the current voltage is 700 V, the second power section considering the charging and discharging efficiency of the battery is 14 kW to 70 kW.

In this way, when the first power section (50kW - 100 kW) and the second power section (14kW - 70 kW) are different, the battery of the VIB ESS (330-2) uses the power (50 - 70 kW) within the first power section. It is proposed to control to perform charging and discharging.

Figure 7 shows that the VIB ESS (330-2) is charged and discharged at 72 to 100 A corresponding to the conversion power section (50 - 70 kW) of the power conversion device 320 determined as above.

Meanwhile, in the example of FIG. 7, if there is a power section in which the first power section (50kW - 100 kW) and the second power section (14kW - 70 kW) overlap, the overlapping power section (50kW - 70 kW) An example in which the ESS (330-2) is charged and discharged with the corresponding power is shown.

On the other hand, if the first power section is larger than the second power section, the charging and discharging power is determined as the minimum power in the first power section, and conversely, if the first power section is smaller than the second power section, the first power It is desirable to determine the maximum power within the section, which will be described later with reference to FIG. 9.

FIG. 8 is a drawing for explaining the concept of a power section that takes battery safety into consideration in charge/discharge control using a VIB ESS according to another embodiment of the present invention.

In the embodiment shown in FIG. 8, unlike FIG. 7, it is assumed that the specifications of the power conversion device 320 have been increased, and the first power section has been increased to 100 kW - 200 kW.

In this situation, the power exchanged with the power conversion device 320 for charging and discharging is determined to be 100 - 200 kW, considering the first power section first, even though the second power section is still 14 kW - 70 kW, Accordingly, an example in which VIB ESS (330-2) is charged and discharged with a current in the range of 143 - 285 A is shown.

In this embodiment, the second power section is set in consideration of 0.2 C - 1C, which is the charging and discharging efficiency section of the VIB, but the section above and/or below the 0.2 C - 1C range in the charging and discharging of the VIB is also possible without safety problems. Available. Therefore, in this embodiment, when the power section considering the safety of the battery is referred to as the third power section, the third power section preferably includes the first power section and at least a section that overlaps with the second power section. It is advantageous to include

As described above in the embodiment of FIG. 8, in order to explain the concept of the third power section considering battery safety, the power section used for charging and discharging the VIB ESS (330-2) is indicated as 100 - 200 kW. As shown, when the first power section is a section larger than the second power section, it is preferable that charging and discharging of the VIB ESS (330-2) is performed with the minimum power (100 kW) of the first power section. This will be described in detail with reference to FIG. 9 .

FIG. 9 is a diagram illustrating a method of determining charge/discharge power according to the relationship between a first power section and a second power section according to an embodiment of the present invention.

As shown in FIG. 9, the battery charging and discharging control method of the ESS according to this embodiment may first perform a comparison between the first power section (1 ^st PR) and the second power section (2 ^nd PR) ( S710). If the first power section (1 ^st PR) and the second power section ( ^2nd PR) are different, charging and discharging of the battery is performed using the power within the first power section (1 ^st PR).

Specifically, in FIG. 9 , when the first power section is greater than the second power section, charging and discharging of the battery can be performed with the minimum power within the first power section (S730). Conversely, when the first power section is smaller than the second power section, charging and discharging of the battery can be performed at the maximum power within the first power section (S720).

Meanwhile, if there is an overlapping section between the first power section and the second power section, the battery charging and discharging power can be set to the power within the overlapping section as in the example of FIG. 7 (S740).

Charging and discharging of the ESS battery can be performed using a current corresponding to the battery charging and discharging power set in this way (S750).

Figure 10 is a diagram for explaining the mechanism by which ESS charging is performed according to an embodiment of the present invention.

First, in order to perform stable power storage/supply using ESS, the maximum available power amount of the grid can be obtained and stored (S4010). Additionally, the contracted amount of power can be obtained and stored as the power level provided from the grid (S4020). Considering the relationship between the amounts of power obtained in this way, the controller can check the amount of power available (the amount of power in use) (S4030).

Based on this, the voltage of the battery can be checked (S4040). The battery voltage confirmed in this way can be used to calculate the optimal charging power amount of the battery using the relationship between battery voltage * optimal charging current (S4050), which can correspond to the concept of the second power section described above.

Based on the optimal charging power amount calculated in this way, the surplus power of the grid can be compared and checked (S4060). If there is no spare power in the grid, you can return to the step of checking the battery voltage. Conversely, if there is spare power in the grid, you can perform subsequent procedures to charge the battery.

As a follow-up procedure for battery charging, in this embodiment, it can be determined whether the battery charging power amount matches the optimal efficiency section of the power conversion device (S4070). This may correspond to comparing the first power period and the second power period in the above-described embodiments.

If the efficiency section of the power conversion device is smaller than the battery power amount, the controller according to this embodiment can set the charging power based on the maximum value among the efficiency sections of the power conversion device (S4074). Conversely, when the efficiency range of the power conversion device is greater than the battery power amount, the controller may set the charging power based on the minimum value of the efficiency range of the power conversion device (S4072).

Alternatively, when the efficiency section of the power conversion device is the same as the battery power amount or has an overlapping section, the battery charging power can be set to the power calculated based on the overlapping section (S4080).

Once the charging power is set in this way, the battery within the ESS can be charged based on this (S4090).

In the above-described embodiment, when the battery of the ESS is a VIB, the efficiency of the output to input of the VIB is best between 0.2 C and 1 C, and the second power section can be set based on this. However, the above-mentioned meaning does not mean that the VIB has poor efficiency at temperatures below 0.2C and above 1C, and the VIB has the characteristic of being able to operate stably no matter what output the power conversion device produces.

In addition, since the VIB has a higher efficiency than the power loss of the power conversion device, this embodiment proposes to control the amount of charging power by giving priority to the power conversion efficiency of the power conversion device.

Figure 11 is a diagram for explaining the mechanism by which ESS discharge is performed according to an embodiment of the present invention.

In order to perform the discharge of the ESS, as shown in FIG. 11, the process of obtaining/storing the maximum amount of power available to the grid (S5010), obtaining/storing the contracted amount of power (S5020), and checking the amount of available power (S5030) It can be performed in the same way as the charging mechanism in FIG. 10.

In this embodiment, when it is determined that there is surplus grid power based on confirmation of such information (S5040), it is proposed to charge the battery to maintain the voltage corresponding to the power within the above-described first power section. Specifically, when it is determined that there is sufficient grid power (S5040), the battery voltage is additionally confirmed (S5042), and the confirmed voltage is discharged efficiently corresponding to the power in the first power section as described above with reference to FIG. 4. If the voltage is insufficient, battery charging can be performed by controlling the charging logic (S5044).

Through this charging, if it is determined that the power of the power grid is insufficient (S5040), the battery can be discharged to a voltage corresponding to the first power section (voltage corresponding to power within the maximum efficiency section of the power conversion device). It can be set (S5041), and battery discharge can be performed based on this (S5043).

A detailed description of preferred embodiments of the invention disclosed above is provided to enable any person skilled in the art to make or practice the invention. Although the present invention has been described above with reference to preferred embodiments, those skilled in the art will understand that various modifications and changes can be made to the present invention without departing from the scope of the present invention. For example, a person skilled in the art may use each configuration described in the above-described embodiments by combining them with each other.

Therefore, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

The ESS charging/discharging control system and the ESS charging/discharging control method according to the embodiments of the present invention as described above can be utilized in a variety of ways, such as at charging stations for electrically driven mobile devices and in sites where power supply and demand imbalance occurs.

Claims (16)

ESS (Energy Storage System) equipped with a battery;
A power conversion device (PCS) connected to a power grid and the ESS to convert the form of power between the power grid and the ESS; and
When the first power section based on the power conversion efficiency of the power conversion device and the second power section based on the charging and discharging efficiency of the battery are different, controlling to charge and discharge the battery with power within the first power section ESS charge/discharge control system comprising a controller. According to claim 1,
The power conversion device includes a converter that converts alternating current power into direct current power and an inverter that converts direct current power into alternating current power,
The first power section is determined based on one or more of a power amount based on the efficiency of the converter and a voltage level based on the efficiency of the inverter. According to claim 1,
The controller is,
When the first power section is greater than the second power section, charging and discharging the battery is performed at the minimum power within the first power section,
An ESS charge/discharge control system that performs charging and discharging of the battery at the maximum power within the first power section when the first power section is smaller than the second power section. According to claim 1,
The controller is,
When the first power section and the second power section include an overlapping section, the ESS charging and discharging control system performs charging and discharging of the battery with power within the overlapping section. According to claim 1,
The controller is,
If there is sufficient power in the power grid, the battery is charged to maintain a voltage corresponding to the power in the first power section,
An ESS charge/discharge control system that controls the battery to be discharged at a voltage corresponding to the power within the first power section when the power of the power grid is insufficient. According to claim 1,
The battery is,
An ESS charge/discharge control system, which is a battery that satisfies the condition that the third power section considering the safety of the battery includes a section overlapping with the first power section. According to claim 6,
The second power section is a power section that is charged and discharged with a current corresponding to the range of 0.2 C to 1 C,
The third power section includes a power section charged and discharged with a current corresponding to one or more of the range of 0.2 C or less and the range of 1 C or more. According to claim 6,
The battery is an ESS charge/discharge control system including a vanadium ion battery (VIB). According to claim 1,
The ESS charge/discharge control system wherein the controller is configured in combination with the power conversion device. In a method of controlling battery charging and discharging of an ESS (Energy Storage System),
Compare a first power section based on the power conversion efficiency of a power conversion device (PCS) that converts the power form between a power grid and the ESS with a second power section based on the charge and discharge efficiency of the battery;
When the first power section and the second power section are different, ESS charging and discharging control method comprising performing charging and discharging of the battery with power within the first power section. According to claim 10,
Performing charging and discharging of the battery includes:
When the first power section is greater than the second power section, charging and discharging the battery is performed at the minimum power within the first power section;
When the first power section is smaller than the second power section, ESS charging and discharging control method comprising performing charging and discharging of the battery at the maximum power within the first power section. According to claim 10,
Performing charging and discharging of the battery includes:
When the first power section and the second power section include an overlapping section, ESS charging and discharging control method comprising performing charging and discharging of the battery with power within the overlapping section. According to claim 10,
If the power of the power grid is sufficient, charge the battery to maintain a voltage corresponding to the power within the first power section;
When the power of the power grid is insufficient, the ESS charging and discharging control method additionally includes discharging the battery to a voltage corresponding to the power within the first power section. According to claim 10,
The battery is,
ESS charge/discharge control method, wherein the battery satisfies the condition that the third power section considering the safety of the battery includes the first power section. According to claim 10,
The second power section is a power section that is charged and discharged with a current corresponding to the range of 0.2 C to 1 C,
The third power section includes a power section charged and discharged with a current corresponding to one or more of the range of 0.2 C or less and the range of 1 C or more. According to claim 10,
The ESS charge/discharge control method wherein the battery includes a vanadium ion battery (VIB).

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