WO2024162549A1

WO2024162549A1 - Ess charging/discharging control system and charging/discharging control method using same

Info

Publication number: WO2024162549A1
Application number: PCT/KR2023/012851
Authority: WO
Inventors: 이동영; 박상현
Original assignee: 스탠다드에너지(주)
Priority date: 2023-01-31
Filing date: 2023-08-30
Publication date: 2024-08-08
Also published as: WO2024162548A1; KR20240120623A; KR20240120622A

Abstract

The present document relates to an energy storage system (ESS) charging/discharging control system and an ESS charging/discharging control method using same. To this end, the charging/discharging control system comprises: an ESS having a battery; a power conversion system (PCS) connected to a power grid and the ESS to convert the power form between the power grid and the ESS; and a controller configured to control charging/discharging of the battery to be performed with power in a first power section if the first power section based on the power conversion efficiency of the power conversion system is different from a second power section based on the charging/discharging efficiency of the battery.

Description

ESS charge/discharge control system and charge/discharge control method using the same

The following description relates to a charge/discharge control system for an ESS (Energy Storage System) and an ESS charge/discharge control method using the same. Specifically, it relates to a method and system for efficiently controlling ESS charge/discharge by giving priority to a power section based on the power conversion efficiency of a power conversion device (PCS).

Recently, as the use of electric vehicles (EVs) has expanded, EV chargers are being installed in various spaces. However, the use of EV chargers increases the electricity usage of the grid and can affect other electricity usage within the space. In particular, when electricity usage surges, there is a problem that the use of EV chargers is restricted.

In addition, various electric-powered mobility devices are being proposed, such as current electric vehicles, uncrewed aerial vehicles (UAVs), and personal mobility devices that require battery charging.

Accordingly, a power system including an ESS is proposed to stably charge the various electric-powered mobile devices described above in a space where a charger is installed, 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 above-described problem, one aspect of the present invention proposes a method for efficiently controlling ESS charging and discharging by giving priority to a power section based on the power conversion efficiency of a power conversion device (PCS), and a system therefor.

In addition, in a preferred embodiment of the present invention, in order to perform charging and discharging by giving priority to the power section of a power conversion device, the requirements of a suitable battery are examined, and a charging and discharging control system using the same 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 can be clearly understood by a person having ordinary skill in the technical field to which the present invention belongs from the description below.

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

In addition, in another aspect of the present invention, a method for controlling battery charging and discharging of an ESS is proposed, including comparing a first power section based on a power conversion efficiency of a power conversion device (PCS) that converts a power form between a power grid and the ESS and a second power section based on a charge and discharge efficiency of the battery; and 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 a power conversion device 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, by performing charging and discharging by giving priority to the power section of the power conversion device, a battery that does not pose a safety problem can be used, thereby simultaneously pursuing the safety and power efficiency of the ESS.

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

Figures 1 and 2 are drawings for explaining the power conversion efficiency of a power conversion device.

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

FIG. 4 is a drawing for explaining the concept of an ESS charge/discharge control system according to one embodiment of the present invention.

FIG. 5 is a drawing for explaining a battery type applied to ESS according to one embodiment of the present invention.

FIG. 6 is a drawing for explaining the structure of a VIB ESS according to one embodiment of the present invention.

FIG. 7 is a drawing for explaining a charging/discharging control method using a VIB ESS according to a preferred embodiment of the present invention.

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.

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

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

FIG. 11 is a drawing for explaining a mechanism by which discharging of an ESS is performed according to one 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 practice the present invention. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein. In addition, in order to clearly describe the present invention in the drawings, parts that are not related to the description are omitted, and similar parts are assigned similar drawing reference numerals throughout the specification.

Throughout the specification, whenever a part is said to "include" a component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise stated.

In general, ESS refers to a device that can store energy in various energy storage means and then supply the stored power back to the grid when needed. Among these ESS, ESS that uses batteries as energy storage means is specifically referred to as BESS (Battery Energy Storage System), but in the following description, unless otherwise specified, ESS is assumed to be BESS.

In general, 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, and multiple cells can form a module, and multiple modules can form a rack. An ESS configured in this way can be connected to a power grid, an electric grid, a power grid, etc., to receive power.

In the description below, the state of the battery can be expressed representatively 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).

First, the charge rate of the battery and/or the discharge rate of the battery can be controlled by the charge/discharge rate (C-Rate). The charge/discharge rate (C-Rate) refers to the measurement of the current used to charge and/or discharge the battery. For example, if a particular battery discharges at 1C-Rate or 1C, it means that a battery with a capacity of 10Ah (i.e., the amount of electricity when 10A (ampere) current flows for 1 hour) can discharge 10A (ampere) for 1 hour from a fully charged state.

By measuring the battery being charged at a specific C-Rate, the corresponding state of charge (SoC) can be checked. When charging an electric vehicle using ESS, the SoC of the battery inside the ESS and the SoC of the battery inside the electric vehicle can be checked to perform various controls on charging.

Based on this description, the following describes specific examples with reference to the drawings.

The power conversion device may include a converter that converts alternating current (AC) power into direct current (DC) power (hereinafter, 'AC/DC converter') and an inverter that converts direct current (DC) power into alternating current (AC) power (hereinafter, 'DC/AC inverter').

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

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

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

Specifically, drawing symbol 210 represents noise occurring at turn-off, and drawing symbol 220 conceptually represents switching loss at turn-off.

In particular, in the drawing symbol 220, the case where the switching speed is high (Case 1) and the case where the switching speed is low (Case 2) are distinguished according to the switching speed, and it can be confirmed that in the case where the switching speed is high (Case 1), the power loss is small due to the small resistance value, whereas in the case where the switching speed is low (Case 2), the power loss is large due to the large resistance value.

In summary, we can see that the higher the output power of an AC/DC converter, 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).

That is, 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.

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.

From the above review, it can be seen that for DC/AC inverters, the higher the battery voltage, the lower the current input to the power conversion device, which increases the efficiency. This shows that a certain level of battery voltage is required to control the efficiency of the power conversion device.

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

Meanwhile, the LIB, which is currently the most popular, has a problem in that it is difficult to charge and discharge within the first power section range 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 illustrated in FIG. 3, the power conversion device (320) can receive AC power from the power grid (310), convert it into DC power, and provide it to the LIB ESS (330-1), and conversely, convert the DC power of the LIB ESS (330-1) into AC power and provide it to the power grid (310).

In the example of Fig. 3, it is assumed that the first power range, which is an optimal power range 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 are limited to a charging rate of 0.2 C to 0.5 C due to the risk of battery fire, etc., and 1 C corresponds to 100 A. When the voltage of the current ESS is 700 V, the above charging rate limitation limits the charging and discharging speed to 14 kW to 35 kW, and FIG. 3 illustrates that the power exchange between the power grid (310) and the power conversion device (320) is limited to 14 kW to 35 KW due to the constraints of the LIB, and the charging and discharging between the power conversion device (320) and the LIB ESS (330-1) is limited to 20 to 50 A.

As described above, if the charging/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), the power loss by the power conversion device (320) increases, which may result in power waste in the entire system.

The ESS charge/discharge control system according to the present embodiment may include: an ESS (330) having a battery; a power grid (310) and a power conversion device (320) connected to the ESS (330) to convert a power form between the power grid (310) and the ESS (330); and a controller (not shown) that controls charging/discharging of the battery of the ESS (330) with power within the first power section when a first power section based on power conversion efficiency of the power conversion device (320) and a second power section based on charge/discharge efficiency of the battery are different.

That is, when charging and discharging the battery of the ESS (330), it is proposed to control the 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 that the battery applied to the ESS (330) is a battery that does not have safety issues when charging and discharging with a current corresponding to the first power section as shown in FIG. 3.

In addition, a battery according to a preferred embodiment of the present invention is preferably a battery in which power loss is minimized below a predetermined standard even when charging and discharging is performed outside a range outside a second power section that takes into account the charging and discharging efficiency of the battery, which will be described in detail later.

ESS의 배터리 타입ESS battery types

In the description of the embodiments described above, the battery used in the ESS need not be interpreted as being limited to a specific type. However, as described above, it is desirable that the battery applied to the ESS (330) has no safety issues when charging and discharging with a current corresponding to the first power section as shown in FIG. 3, and further, that the battery be a battery in which power loss is minimized below a predetermined standard even when charging and discharging is performed outside a range that preferably takes into account the charging and discharging efficiency of the battery, and for this purpose, an ESS based on a vanadium ion battery (VIB) proposed by the applicant of the present invention is described.

As described above, there are various types of batteries applicable to ESS, and for example, lead-acid batteries, lead carbon batteries, NAS (Sodium Sulfur) batteries, lithium-ion batteries (LIBs), flow batteries, etc. can be utilized. Fig. 5 (A) illustrates an example of a system in which a LIB ESS (210) is applied, in which LIBs, which are currently receiving the most attention among these various ESS batteries, are applied.

LIBs are attracting attention because they have high energy density and power density, are about three times lighter than conventional lead-acid batteries, and can reduce space consumption by 50-80% due to their high power density. In addition, they can discharge 1-2% of the charge per month and maintain a long service life, and can be used for about 10 years and have 5,000 battery cycles depending on conditions.

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

Additionally, for alkaline and lead batteries, it is common to operate at 0.05C (= 20 hours of discharge) to avoid battery capacity reduction (performance reduction) due to heat generation.

In contrast, the VIB developed by the present applicant refers to a secondary battery that electrochemically stores/releases energy using vanadium ions as an active material. While existing vanadium-based batteries store/release electrical energy by forcibly circulating/transporting/storing active materials (e.g., vanadium ions, H+ cations, water, sulfuric acid, etc.) participating in an electrochemical reaction by an externally powered pump, the VIB uses the internal electric field, osmotic pressure, concentration difference, etc. of the active materials to change and move ions, and the active materials store/release energy through an electrochemical reaction within the cell and/or module.

In particular, for VIB, charging and discharging at 0.5 to 5C (MAX 10C) is possible. In addition, since it is driven using a water-soluble electrolyte, it is free from fire risk and has the advantage of being able to utilize a wide SoC.

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

For example, in the case of LIB, high output may cause heat generation and affect battery life, but in the case of VIB, stable high output is possible. In addition, in the case of LIB, there are limitations such as 1C charging and 1C discharging, but in the case of VIB, input/output flow control is possible with high output, and for example, when a power outage occurs in the grid (110), the VIB ESS (140) can assist both the grid (110) and the charger with high output, so the utilization of the VIB ESS (140) has the advantage of being able to perform very efficient ESS charge/discharge management.

In particular, since there is no risk of fire due to overload in the case of VIB, when such VIB is applied to the ESS of this embodiment, the system of the present invention can be preferably applied to various auxiliary facilities while ensuring safety, so it can be said to be a very effective power supply system. In addition, since the utilization of VIB ESS (140) enables safe and efficient energy supply, it can be utilized as a very effective, safe, and environmentally friendly energy supply means for energy conservation, energy environment, and realization of carbon neutrality.

Additionally, when utilizing the VIB ESS (140) as illustrated in (B) of FIG. 5, the high-speed charge/discharge performance of the VIB as described above can be utilized to more efficiently utilize the amount of power measured by multiple power meters (211, 212, 220). For example, when the measured value of the power meter (212) measuring the amount of power flowing into the charger decreases rapidly, this can be supported by high-speed discharge, and when the measured value of the power meter (220) measuring at the load end other than the ESS is below a predetermined standard, the VIB ESS (140) can be charged at high speed.

Meanwhile, in the case of LIB, there are upper and lower voltage limits, so a relatively narrow voltage range (window) is used. Specifically, when LIB is at 0 V or under severe discharge condition (lower than the lower voltage limit), dendrite material is generated, which causes a short circuit due to damage to the separator, which can cause thermal runaway.

In contrast, VIB has an upper voltage limit but no lower voltage limit, so it has the advantage of being able to use a relatively wide voltage range (window). That is, no special problem occurs even when it becomes 0 V or a fully discharged state, so it can operate more flexibly depending on the measurement situations of multiple power meters.

In addition, in the case of LIB, there is a problem that capacity difference occurs during a certain cycle of operation due to the existence of irreversible reactions (surface precipitation phenomenon, solid electrolyte interphase phenomenon, cracking phenomenon) caused by phase change when repeating charge and discharge cycles, but in the case of VIB, there is an advantage of no difference between the initial capacity and the capacity after a certain cycle of operation by utilizing a reversible reaction.

Meanwhile, in connection with the upper/lower limit voltage as described above, in the case of LIB, it is impossible to use it below 20% of SoC in reality (theoretical), but in the case of VIB, since there is no lower limit voltage, it can be used below 20% of SoC in reality (theoretical).

Here, the term actual (theoretical) SoC is a concept to distinguish it from the SoC provided by the manufacturer, and manufacturers generally provide the safety-free range of the actual SoC range as 0% - 100% for safety reasons. In contrast, actual (theoretical) SoC refers to the SoC that calculates 100% for a full charge of the battery and 0% for a full discharge.

The main features of these LIBs and VIBs can be summarized as shown in Table 1 below.

	LIBLIB	VIBVIB
화재 위험성Fire hazard	높음height	없음doesn't exist
충방전율Charge/discharge rate	0.2-0.5 C0.2-0.5 C	0.5 - 5 C(Max 10 C)0.5 - 5 C (Max 10 C)
전압범위Voltage range	상한전압, 하한전압 존재There are upper and lower voltage limits	상한전압 존재, 하한전압은 XUpper voltage limit exists, lower voltage limit is X
실제 SoC 20% 미만 동작Actual SoC operation less than 20%	불가Impossible	가능possible
사이클 반복 시 특징Features when repeating cycles	상 변화로 비가역 반응Irreversible reaction with phase change	가역적 반응reversible reaction

FIG. 6 is a drawing for explaining the structure of a VIB ESS according to one embodiment of the present invention. As shown in FIG. 6, the VIB ESS also includes components such as a battery, BMS, PCS, and EMS.

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

Here, each level means an operation level that includes other control configurations than the above-described BMS. For example, level 2 may specify control with the level 1 control stage of the above-described pack BMS (32) and control operations for the switch gear (34), and level 3 may specify control operations between the above-described system BMS (33) and PMS (35). In addition, the final level 4 may specify control operations between multiple PMSs (35) and EMSs (36).

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

In the embodiments described in FIGS. 5 and 6, the type of battery applied to the ESS is exemplarily described as VIB (FIG. 5(B) and FIG. 6) in contrast to LIB (FIG. 5(A)), but the type of battery applied to the ESS need not be limited to VIB. For example, the ESS in this specification may utilize a VRB (Vanadium Redox Battery), a PSB (polysulfide bromide battery), a ZBB (zinc-bromine battery), etc.

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

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

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

Fig. 7 illustrates that the VIB ESS (330-2) is charged and discharged at 72 to 100 A in response to the conversion power range (50 to 70 kW) of the power conversion device (320) determined as above.

Meanwhile, in the example of Fig. 7, when there is a power section where the first power section (50 kW - 100 kW) and the second power section (14 kW - 70 kW) overlap, an example is shown where the ESS (330-2) is charged and discharged with power corresponding to the overlapping power section (50 kW - 70 kW).

In contrast, if the first power section is larger than the second power section, the charge/discharge power is preferably determined as the minimum power within the first power section, and conversely, if the first power section is smaller than the second power section, it is preferably determined as the maximum power within the first power section, which will be described later with reference to FIG. 9.

In the embodiment illustrated in Fig. 8, unlike Fig. 7, it is assumed that the specifications of the power conversion device (320) are increased, and the first power section is 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 to 200 kW by giving priority to the first power section, even though the second power section is still 14 kW to 70 kW, and accordingly, an example is shown in which the VIB ESS (330-2) is charged and discharged with a current in the section of 143 to 285 A.

In this embodiment, the second power section is set in consideration of the charge/discharge efficiency section of 0.2 C - 1 C of the VIB, but a section above and/or below 0.2 C - 1 C in the charge/discharge of the VIB can also be used without any safety issues. Therefore, that is, when the power section considering the safety of the battery in this embodiment is referred to as the third power section, it is preferable that the third power section includes the first power section, and it is advantageous that it includes at least a section overlapping with the second power section.

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 to 200 kW. However, as described above, if the first power section is a section larger than the second power section, it is preferable that the charging and discharging of the VIB ESS (330-2) is performed with the minimum power (100 kW) of the first power section, and this will be described in detail with reference to FIG. 9.

As illustrated in FIG. 9, the battery charge/discharge control method of the ESS according to the present embodiment can 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 (2 ^nd PR) are different, the battery is charged/discharged using the power within the first power section (1 ^st PR).

Specifically, in FIG. 9, if 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, if the first power section is smaller than the second power section, charging and discharging of the battery can be performed with 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 charge/discharge power can be set as the power within the overlapping section as in the example of Fig. 7 (S740).

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

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

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

Based on the optimal charging power amount calculated in this way, it is possible to compare and check whether there is spare power in the grid (S4060). If there is no spare power in the grid, the process can return to the step of checking the battery voltage again, and conversely, if there is spare power in the grid, subsequent procedures can be performed to charge the battery.

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

If the efficiency range of the power conversion device is smaller than the battery power, the controller according to the present embodiment can set the charging power based on the maximum value of the efficiency range of the power conversion device (S4074). Conversely, if the efficiency range of the power conversion device is larger than the battery power, the controller can set the charging power based on the minimum value of the efficiency range of the power conversion device (S4072).

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

When the charging power is set in this way, charging of the battery in the ESS can be performed based on this (S4090).

In the above-described embodiment, if the ESS battery is VIB, the efficiency of the input-to-output of VIB is the best between 0.2 C and 1 C, and the second power section can be set based on this. However, the above-described meaning does not mean that VIB has poor efficiency below 0.2 C or above 1 C, and VIB has the characteristic of being able to operate stably regardless of the output of the power conversion device.

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

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

In this embodiment, if it is determined (S5040) that there is a surplus in grid power based on such information verification, it is proposed to charge the battery so that the voltage corresponding to the power within the first power section described above is maintained. Specifically, if it is determined (S5040) that there is a surplus in grid power, the battery voltage is additionally verified (S5042), and if the verified voltage is lower than the efficient discharge voltage corresponding to the power within the first power section described above with respect to FIG. 4, the charging logic can be controlled (S5044) to perform battery charging.

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

The detailed description of the preferred embodiments of the present invention disclosed above has been provided to enable those skilled in the art to implement and practice the present invention. Although the above has been described with reference to preferred embodiments of the present invention, 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, those skilled in the art can utilize each configuration described in the above-described embodiments in a manner of combining them with each other.

Accordingly, 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 charge/discharge control system and the ESS charge/discharge control method using the same according to the embodiments of the present invention as described above can be utilized in various ways at charging stations for electric-powered mobile devices and at sites where power supply/demand imbalance occurs.

Claims

ESS (Energy Storage System) equipped with batteries;

A power conversion device (PCS) connected to a power grid and the ESS, converting the form of power between the power grid and the ESS; and

An ESS charge/discharge control system characterized in that it includes a controller that controls charging/discharging of the battery with power within the first power section when the first power section based on the power conversion efficiency of the power conversion device and the second power section based on the charge/discharge efficiency of the battery are different.
In paragraph 1,

The above power conversion device includes a converter that converts AC power into DC power and an inverter that converts DC power into AC power.

An ESS charge/discharge control system, wherein the first power section is determined based on at least one of a power amount based on the efficiency of the converter and a voltage level based on the efficiency of the inverter.
In paragraph 1,

The above controller,

If the first power section is greater than the second power section, charging and discharging of the battery is performed with the minimum power within the first power section.

An ESS charge/discharge control system that performs charging/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.
In paragraph 1,

The above controller,

An ESS charge/discharge control system that performs charging/discharging of the battery with power within the overlapping section when the first power section and the second power section include an overlapping section.
In paragraph 1,

The above controller,

When there is a surplus of power in the above power grid, the battery is charged so that the voltage corresponding to the power within the first power section is maintained,

An ESS charge/discharge control system that controls the battery to discharge to a voltage corresponding to power within the first power section when there is a power shortage in the above power grid.
In paragraph 1,

The above battery,

An ESS charge/discharge control system, wherein the battery satisfies a condition in which a third power section considering the safety of the battery includes a section overlapping with the first power section.
In paragraph 6,

The above second power section is a power section in which charging and discharging are performed with a current corresponding to a range of 0.2 C to 1 C.

An ESS charge/discharge control system, wherein the third power section includes a power section in which charging and discharging are performed with a current corresponding to at least one of a range of 0.2 C or less and a range of 1 C or more.
In paragraph 6,

The above battery is an ESS charge/discharge control system including a vanadium ion battery (VIB).
In paragraph 1,

An ESS charge/discharge control system, wherein the above controller is configured in combination with the above power conversion device.
In a method for controlling battery charging and discharging of an ESS (Energy Storage System),

A first power section based on the power conversion efficiency of a power conversion device (PCS) that converts the form of power between a power grid and the ESS and a second power section based on the charge/discharge efficiency of the battery are compared;

An ESS charge/discharge control method, comprising: performing charge/discharge of the battery with power within the first power section when the first power section and the second power section are different.
In Article 10,

Carrying out charging and discharging of the above battery is as follows:

When the first power section is greater than the second power section, charging and discharging of the battery is performed with the minimum power within the first power section;

An ESS charge/discharge control method, comprising: performing charge/discharge of the battery at maximum power within the first power section when the first power section is smaller than the second power section.
In Article 10,

Carrying out charging and discharging of the above battery is as follows:

An ESS charge/discharge control method, comprising: performing charge/discharge of the battery with power within the overlapping section when the first power section and the second power section include an overlapping section.
In Article 10,

When there is surplus power in the above power grid, the battery is charged so that the voltage corresponding to the power within the first power section is maintained;

An ESS charging/discharging control method, further comprising discharging the battery to a voltage corresponding to power within the first power section when power of the power grid is insufficient.
In Article 10,

The above battery,

An ESS charge/discharge control method, wherein the battery satisfies a condition in which a third power section considering the safety of the battery includes the first power section.
In Article 10,

The above second power section is a power section in which charging and discharging are performed with a current corresponding to a range of 0.2 C to 1 C.

A method for controlling charging and discharging of an ESS, wherein the third power section includes a power section in which charging and discharging is performed with a current corresponding to at least one of a range of 0.2 C or less and a range of 1 C or more.
In Article 10,

A method for controlling charge and discharge of an ESS, wherein the battery comprises a vanadium ion battery (VIB).