WO2019235657A1 - Solar energy storage system divided into daytime and night mode, and its operation method and battery replacement method thereof - Google Patents

Solar energy storage system divided into daytime and night mode, and its operation method and battery replacement method thereof Download PDF

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Publication number
WO2019235657A1
WO2019235657A1 PCT/KR2018/006434 KR2018006434W WO2019235657A1 WO 2019235657 A1 WO2019235657 A1 WO 2019235657A1 KR 2018006434 W KR2018006434 W KR 2018006434W WO 2019235657 A1 WO2019235657 A1 WO 2019235657A1
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WIPO (PCT)
Prior art keywords
battery
step
unit
soc
value
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PCT/KR2018/006434
Other languages
French (fr)
Inventor
Seong Il Paeng
Man Hui Geum
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Dass Tech Co., Ltd.
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Application filed by Dass Tech Co., Ltd. filed Critical Dass Tech Co., Ltd.
Priority to PCT/KR2018/006434 priority Critical patent/WO2019235657A1/en
Publication of WO2019235657A1 publication Critical patent/WO2019235657A1/en

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    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00Secondary cells; Manufacture thereof
    • H01M10/42Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/46Accumulators structurally combined with charging apparatus
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02JCIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/34Parallel operation in networks using both storage and other dc sources, e.g. providing buffering
    • H02J7/35Parallel operation in networks using both storage and other dc sources, e.g. providing buffering with light sensitive cells
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02SGENERATION OF ELECTRIC POWER BY CONVERSION OF INFRA-RED RADIATION, VISIBLE LIGHT OR ULTRAVIOLET LIGHT, e.g. USING PHOTOVOLTAIC [PV] MODULES
    • H02S10/00PV power plants; Combinations of PV energy systems with other systems for the generation of electric power
    • H02S10/20Systems characterised by their energy storage means
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02SGENERATION OF ELECTRIC POWER BY CONVERSION OF INFRA-RED RADIATION, VISIBLE LIGHT OR ULTRAVIOLET LIGHT, e.g. USING PHOTOVOLTAIC [PV] MODULES
    • H02S50/00Monitoring or testing of PV systems, e.g. load balancing or fault identification

Abstract

Disclosed is a photovoltaic energy storage system, and methods of controlling the same. The photovoltaic energy storage system operates separately in a daytime operation mode and in a nighttime operation mode. According to the method of controlling the photovoltaic energy storage system, it is possible to provide a DC load with power without interruption of a DC power source and to replace the battery with a new battery based on the result of determining whether the battery is abnormal or not.

Description

SOLAR ENERGY STORAGE SYSTEM DIVIDED INTO DAYTIME AND NIGHT MODE, AND ITS OPERATION METHOD AND BATTERY REPLACEMENT METHOD THEREOF

The present invention relates to a photovoltaic energy storage system and a method of controlling the photovoltaic generation energy storage system. More particularly, the present invention relates to a photovoltaic energy storage system that operates separately in a daytime operation mode and a nighttime operation mode, and relates to a method of operating the photovoltaic energy storage system. And more particularly, the present invention relates to a method of controlling the photovoltaic energy storage system including the step of replacing a battery without interruption of a DC power source.

The photovoltaic power generation system refers to a power generation system that generates electrical energy by using one or more solar cells that employ semiconductor devices capable of converting solar energy into electrical energy. In such a photovoltaic power generation system, one or two or more solar cells are embodied as needed, and they are connected in series or in parallel. This general form of photovoltaic system is disclosed in the public as various forms.

A characteristic part of the above-described the photovoltaic power generation system as described above is as follows. Since the sunlight, which is the source of electric energy, is supplied only during the daytime, it is impossible to generate electrical energy at night. Also, the power output may fluctuate according to the weather conditions during the daytime. Thus, the typical photovoltaic power generation system organizes a separate energy storage system.

A part of the electric energy to be produced during sunny hours is separately allocated to the surplus electric power, and it is stored in the energy storage system. The energy storage system is operated together with the photovoltaic power generation system.

The energy storage system has a tendency to increase in the proportion of relative importance in the photovoltaic power generation system due to factors such as its capacity increase, drop in prices, and prolonged life span, etc. Since it also contributes to the stable power supply, its importance is continuously increasing.

Typical examples of the energy storage system include a battery for storing electrical energy, a thermal storage tank for storing thermal energy, and a hydrogen generator for storing chemical energy, etc. The energy storage system can be configured in various forms depending on the energy source needed by the customer.

For example, Korean Patent No. 10-1469904 discloses a power control board mode control system for solar installations with ESS. This registered patent discloses a series of techniques for minimizing electric power charges through the optimal control of grid-connected photovoltaic power generation facilities based on the power demand pattern of the building, the real-time monitoring data of the solar power generation according to the amount of sunshine, and the real-time grid power prices.

Korean Patent Laid-Open Publication No. 10-2016-0028884 discloses a management method of ESS and solar generator, and Korean Patent Laid-Open Publication No. 10-2017-0038640 discloses a power control system and a method for ESS apparatus.

Korean Patent No. 10-1651772 discloses a power controlling system using energy storage system capable of improving the efficiency of the system.

Korean Patent No. 10-1766433 discloses an energy storage system including power conversion apparatus for operating with grid-connected photovoltaic power and charging /discharging power of battery. According to this registered patent, the energy storage system is automatically switched to a buck mode or a boost mode with reference to an average of current values flowing to an operation area (CCM/DCM) and an inverter side.

It is to be understood that all of the above-described Korean patent laid-open publications and registered patents are entirely different from the present invention in terms of their constituent elements and control methods.

It is an object of the present invention to provide a photovoltaic generation energy storage system and a method of controlling the photovoltaic generation energy storage system with a different configuration from the prior arts as mentioned above.

According to one aspect of the present invention, the present invention provides a photovoltaic energy storage system using more than one battery, the photovoltaic energy storage system comprising:

a solar cell unit including at least one solar cell;

a solar battery unit for controlling a power produced by the solar cell unit and including a DC/DC converter;

a solar cell breaker being installed between the solar cell unit and a solar battery unit;

a DC link unit being installed between the solar battery unit and a power system;

a power conversion unit being installed between the DC link unit and the power system and including a DC/AC bidirectional power converter;

a battery unit including at least one battery and being capable of storing an electrical energy;

a battery part for controlling charging of the battery unit and being connected to the solar battery unit and the power conversion unit by using the DC link unit as a contact point, the battery part including a DC/DC converter;

a battery breaker and a battery switch being installed between the battery part and the battery unit;

a DC load unit being connected between the battery part and a DC load, the DC load unit including a DC/DC converter for supplying a DC power to the DC load; and

a control unit for controlling operations of the solar battery unit, the battery part, the DC link unit, the power conversion unit, and the DC load unit.

According to other aspect of the present invention, the present invention provides a method of controlling a solar photovoltaic energy storage system for supplying a power to a DC load and for charging a battery by using the photovoltaic energy storage system as described above, the method comprising the steps of:

(S1) checking the overall system status of the solar photovoltaic energy storage system;

(S2) confirming that the current time (t) belongs to the daytime if the control unit determines that the current time (t) exceeds the daytime boundary time (td) and falls within the range below the nighttime boundary time (tn), and confirming that the current time (t) belongs to the nighttime if the control unit determines that the current time (t) exceeds the daytime boundary time (td) and it is outside the range, when the overall system is normal in the step (S1);

(S31) operating the photovoltaic energy storage system as a daytime operation mode, if it is determined that the current time (t) belongs to the daytime in the step (S2);

(S32) checking the charged state of the battery unit after the step (S31);

(S33) performing a battery remaining amount scenario mode (S5) if the charged state of the battery in the battery unit is in the low voltage state or the overvoltage state in the step (S32), and determining the operation of the solar cell unit by measuring a voltage (PV) of electric energy produced by the solar cell unit if the charged state of the battery in the battery unit is the normal voltage in the step (S32);

performing the step (S1) if an initial operating voltage (PVr) is greater than 150V, which is the operation start voltage, or the current voltage (PV) is within the operating sustain voltage range of more than 100V to less than 500V in the step (S33), and performing an operation standby mode (S34) for stopping the power generation of the solar cell unit when the initial operating voltage (PVr) is equal to or lower than 150V or the current voltage (PV) is out of the operating sustain voltage range in the step (S33), and performing the step (S2) after the step (S34);

(S41) operating the photovoltaic energy storage system as a nighttime operation mode if the current time (t) belongs to the nighttime in the step (S2);

(S42) checking the charged state of the battery unit after the step (S41); and

performing the battery remaining amount scenario mode (S5) when the charged state of the battery in the battery unit is in the low voltage state or in the overvoltage state in the step (S42), and performing the step (S1) if the charged state of the battery in the battery unit is in the normal voltage state in the step (S42).

In the step (S31), the DC/DC converter in the solar battery unit operates in the maximum power point tracking mode, and the DC/AC power converter in the power conversion unit operates in the inverter mode.

In the step (S41), the DC/AC power converter in the power conversion unit operates in the converter mode, and the grid current reference value of the DC link unit becomes a negative (-) value.

In the steps (S31) and (S41), the battery unit supplies DC power to the DC load unit.

The method of controlling a solar photovoltaic energy storage system further comprises the steps of:

(S321) determining whether the charged state value (soc) of the battery is verifiable or not to confirm the charged state of the battery when the steps (S32, S42) are started;

(S322) comparing the charged state value (soc) with the minimum allowable sic value (soc_mi) and the maximum allowable sic value (soc_mx), which are inputted in advance, if the charged state value (soc) is confirmed in the step (S321);

(S324) confirming the charged state of the battery is normal if the charged state value (soc) is equal to or greater than the minimum allowable soc value (soc_mi) and is equal to or less than the maximum allowable soc value (soc_mx), and ending the steps (S32, S42) after the step (S324);

performing the step (S5) if the charged state value (soc) is less than the minimum allowable soc value (soc_mi) or is greater than the maximum allowable soc value (soc_mx) in the step (S322);

(S323) comparing the voltage value (BV) of the battery with the minimum permissible voltage value (BV_mi) and the maximum allowable voltage value (BV_mx), if it is impossible to confirm the charged state value (soc) in the step (S321);

(S324) confirming the charged state of the battery is in the normal state if the voltage value (BV) of the battery is greater than the minimum permissible voltage value (BV_mi) and is less than the maximum allowable voltage value (BV_mx), and then ending the steps (S32, S42) after the step (S324); and

performing the step (S5) if the voltage value (BV) of the battery is equal to or less than the minimum allowable soc value (soc_mi) and is equal to or greater than the maximum allowable soc value (soc_mx) in the step (S323).

The method of controlling a solar photovoltaic energy storage system further comprises the steps of:

(S51) determining whether the battery in the battery unit is in the low voltage state or in the overvoltage state when the battery remaining amount scenario mode (S5) is started;

(S52) warning the user about that the battery is in the low voltage state when the batteries in the battery unit are determined to be in the low voltage state in the step (S51);

(S53) checking the low voltage state of the battery after the step (S52);

(S55) reporting the fact that the battery is in the low voltage state, if the current battery voltage value (BV) is lower than the limit permissible voltage value (BV_lim) inputted in advance and the charge count (cn) is higher than the maximum charge count (cmx) inputted in advance in the step (S53), and then performing the step (S1) after the step (S55);

(S54) charging the battery if the current battery voltage value (BV) is equal to or higher than the limit permissible voltage value (BV_lim) or if the charge count (cn) is equal to or smaller than the maximum charge count (cmx) in the step (S53);

(S56) alerting the user about that the battery is in the overvoltage state if it is determined that the batteries in the battery unit are in the overvoltage state in the step (S51); and

(S7) stopping the charging of the battery unit (210) after the step (S56), and then performing the step (S51) after the step (S56).

In the step (S54), the charging of the battery unit is started, and the control unit judges whether the charging time exceeds 2 hours or not, and then the battery is charged until the charging time (ct) exceeds 2 hours.

The method of controlling a solar photovoltaic energy storage system further comprises the steps of:

performing the step (S1) if the battery charged state value (soc) exceeds a charge allowable soc value (soc_ps) inputted in advance or the battery voltage value (BV) is more than the rated voltage value (RV), after charging the battery unit in the step (S54); and

performing the step (S53) by adding one to the current charge count (cn) if the battery charged state value (soc) is less than the charge allowable soc value (soc_ps) and the battery voltage value (BV) is less than the rated voltage value (RV), after charging the battery unit in the step (S54).

The method for replacing a battery in the battery unit in the solar photovoltaic energy storage system comprises the steps of:

(S61) setting the control unit to a battery replacement mode;

(S62) changing the operation mode of the solar photovoltaic energy storage system from the daytime operation mode into the nighttime operation mode when the photovoltaic energy storage system is operated in the daytime operation mode;

(S63) replacing the battery with a new battery if the step (S62) is performed or if the nighttime operation mode is executed, by disconnecting the electromagnetic contactor in the battery part; and

releasing the battery replacement mode after ending the step (S63).

The operation mode of the DC/DC converter in the battery part is changed to the constant voltage charging mode and then it is maintained at a constant voltage before turning off the electromagnetic contactor in the battery unit in the step (S62).

The charged state value generation energy storage system and the method of controlling the same according to the present invention can charge the battery constantly and effectively regardless of daytime, nighttime and solar radiation dose, and it can provide a uniform DC voltage to the DC load. In addition, it is possible to quickly judge whether the battery is malfunctioning and to take measures safely.

FIGS. 1 to 3 show the structure of a photovoltaic energy storage system according to the present invention;

FIG. 4 is a flow chart for controlling a solar power generation storage system in a daytime operation or in a nighttime operation by using the photovoltaic energy storage system of the present invention;

FIG. 5 is a flowchart for showing the step of checking the charged state of the battery unit according to the present invention;

FIG. 6 is a flowchart for showing the step of performing a battery remaining amount scenario mode according to the present invention; and

FIG. 7 is a flowchart illustrating a procedure for replacing a battery in the battery unit in the solar energy storage system of the present invention.

Hereinafter, the present invention will be described in detail with reference to the drawings.

Although the present invention has been described and illustrated in detail, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the spirit and scope of the present invention being limited only by the terms of the appended claims.

FIGS. 1 to 3 show the structure of a photovoltaic energy storage system according to the present invention.

Hereinafter, constitutional elements and operation of the photovoltaic energy storage system according to the present invention will be described in detail with reference to FIGS. 1 to 3.

Prior to the description, the parts connected by the solid line in FIGS. 1 to 3 indicate the physical circuit connection relationship in which the electrical energy is transmitted and received. The parts connected by the dotted line in FIG. 1, indicate the connection relationship which is communicably connected so as to exchange signals or information between the constitutional elements. In FIG. 1, the solid line and the dotted line are independent of each other without any contact point. In Figs. 2 and 3, arrows indicated by the dotted line indicate the flow direction of electrical energy.

As shown in FIG. 1, the photovoltaic energy storage system of the present invention may be applied to a power generation system that generates electricity and electrical energy by using a solar cell (C). The solar cell (C) may be composed of one or more than two solar cells (C) connected in series and in parallel. In the present invention, one or more solar cells (C) that produce electrical energy are used as the solar cell unit (110) as described above.

In order to control the power generated by the solar cell unit (110), a solar battery unit (100) is connected to the solar cell unit (110). The solar battery unit (100) may include a series of sensors and arithmetic units for controlling the operation of the solar cell unit (110), a storage device, and one or more programs embedded in the storage device. Since the configuration of the unit (100) is general, a detailed description thereof will be omitted.

In particular, the solar battery unit (100) includes a DC/DC converter for converting the DC power voltage of the electrical energy produced by the solar cell unit (110). The DC/DC converter of the solar battery unit (100) is unidirectional and converts the DC power voltage of the electrical energy produced by the solar cell unit (110) only in the arrow direction shown above the solar battery unit (100) of FIG. 1.

A solar cell breaker (120) is installed between the solar battery unit (100) and the solar cell unit (110).

A DC link unit (300) and a power conversion unit (310) are provided between the power system G that is a power network in which other electrical energy can be introduced thereto in addition to the electric energy generated by the solar battery unit (100) and the solar cell unit (110).

The DC link unit (300) determines a reference value of an amount of electric current to be transmitted to the power system (G) with respect to electrical energy transmitted from the solar battery unit (100).

The power conversion unit (310) connected to the DC link unit (300) includes a DC/AC bidirectional power converter for converting the AC power input from the power system (G) into DC power or converting DC power transmitted from the DC link unit (300) to AC power. The power conversion unit operates as an inverter when converting DC power to AC power (inverse conversion) to transmit power to the power system G, and it operates as a converter when conversely converting AC power supplied from the power system G to DC power (net conversion).

The photovoltaic energy storage system of the present invention comprises a battery unit (210) including one or more batteries for storing a part of electrical energy produced by the solar cell unit (110). One or more batteries to be included as the constitutional element of the battery unit (210) may be any battery that can charge electrical energy.

In order to control charging of the battery unit (210), the battery part (200) is connected to the battery unit (210). The battery part (200) is connected to the solar battery unit (100) and the power conversion part (310) by using the DC link part (300) as a contact point.

In the daytime operation mode, the battery part (200) transmits electrical energy transmitted from the solar battery unit (100) to the battery unit (210) to charge the battery unit (210). Alternatively, the battery part (200) transmits electrical energy transmitted from the electric power system (G) to the battery unit (210) to charge the battery unit (210). Also, the battery part (210) may discharge electrical energy in the battery unit (210) and then can supply it other constitutional elements as needed.

For this purpose, the battery part (200) may include a series of sensors and arithmetic units for controlling the operation of the battery unit (210), a storage device, and one or more programs embedded in the storage device. Since the configuration of the battery part (200) is general, a detailed description thereof will be omitted.

In particular, the battery part (200) includes a DC/DC converter for converting the DC power voltage of the electrical energy. The DC/DC converter of the battery part (200) is unidirectional and converts the DC power voltage of the electrical energy only in the arrow direction shown above the battery part (200) of FIG. 1.

A battery breaker (220) and a battery switch (230) are installed between the battery part (200) and the battery unit (210).

A solar cell breaker (120) is installed between the solar battery unit (100) and the solar cell unit (110).

A DC link unit (300) and a power conversion unit (310) are provided between the power system G that is a power network in which other electrical energy can be introduced thereto in addition to the electric energy generated by the solar battery unit (100) and the solar cell unit (110).

The DC link unit (300) determines a reference value of an amount of electric current to be transmitted to the power system (G) with respect to electrical energy transmitted from the solar battery unit (100).

A DC load unit (400) is connected between the battery part (200) and the DC load unit so as to supply DC power to the DC load (D) without converting the DC power produced by the solar cell unit (110) into the AC power.

The DC load unit (400) includes a one-way DC/DC converter (not shown) for converting the DC power supply voltage to provide the DC load (D) with the DC power supplied from the battery unit (200) or the battery unit (210).

The photovoltaic energy storage system of the present invention includes a control unit (500) for controlling operations of the solar battery unit (100), the battery part (200), the DC link unit (300), the power conversion unit (310), and the DC load unit (400).

The control unit (500) may include at least one computing device and a storage device, and at least one program installed in the storage device, for controlling the constitutional elements.

The control unit (500) may directly control operations of the solar cell unit (110), the battery unit (210), the circuit breakers (120, 220), and the switch 230, in addition to the constitutional elements. Alternatively, the operations of the solar cell unit (110) and the solar cell breaker (120) may be controlled by the solar battery unit (100), and the operations of the battery unit (210), the battery breaker (220) and the battery switch (230) may be controlled by the battery part (200).

As described above, during the day when the solar cell unit (110) generates electric power, electrical energy flows as indicated by the dotted arrow in Fig. 2.

As shown in FIG. 2, the electrical energy produced by the solar cell unit (110) is converted into an AC power through the solar battery unit (100) and the power conversion unit (310), and then it may be transmitted to the power system (G). Alternatively, the electrical energy may be transmitted to the battery unit (210) via the battery part (200) so as to charge the battery in the battery unit (210). Alternatively, the electrical energy may be transmitted to the DC load (D) through the DC load part (400).

When the solar cell unit (110) does not supply electrical energy due to nighttime or weather conditions or other problems, the AC power supplied from the power system (G) is converted into the DC power and then it may be provided to the battery unit (210) or the DC load (D) as shown by the dotted arrow in Fig. 3.

The flow direction of the electrical energy shown in FIG. 2 and FIG. 3 corresponds to a general case, and in some cases, the battery in the battery unit (210) must be replaced or repaired in a state in which electrical energy cannot be supplied due to failure or breakage thereof. The operation procedure for this special situation will be described later.

FIG. 4 is a flow chart for controlling a solar power generation storage system in a daytime operation or in a nighttime operation by using the photovoltaic energy storage system of the present invention.

Hereinafter, the operation of the photovoltaic energy storage system of the present invention will be described with reference to FIGS. 1 and 4.

When the photovoltaic generation system including the photovoltaic energy storage system of the present invention starts to operate, the control unit (500) checks the overall system state of the photovoltaic energy storage system (= step (S1)).

In the step (S1), if the normal operation cannot be performed due to failure or damage of any one of the constitutional elements, or if there is a risk of a safety accident during operation, the control unit (500) immediately terminates the operation of all the systems by performing the emergency termination step (S11).

If it is determined that the entire system can be normally operated without failure in the step (S1), the control unit (500) determines whether the photovoltaic energy storage system is in a daytime operation mode or in a nighttime operation mode (=step (S2)).

In the step (S2), the control unit (500) judges the day or night based on the current time (t). If the current time (t) exceeds the daytime boundary time (td) and is less than the nighttime boundary time (tn), the control unit determines that it is daytime, and if the current time (t) is outside the above range, the control unit determines that it is nighttime.

For example, if the daytime boundary time (td) is 6 AM (td = 6) and the nighttime boundary time (tn) is set at 6 PM (tn = 18), the control unit determines that the current time (t) is a daytime when the current time (t) is in a range of more than 6 and less than 18. If it is out of the range, the control unit judges that it is nighttime.

If the current time (t) is determined to be the daytime in the step (S2), the solar cell unit (110) can generate electric power, so that the control unit (500) makes the solar energy storage system of the present invention operate in the daytime operation mode (=step (S31)).

In the step (S31), in order to comply with the amount of electrical energy generated by the solar cell unit (110), the DC/DC converter in the solar battery unit (100) operates in a maximum power point tracking (MPPT) mode.

Accordingly, the DC link unit (300) maintains a preset constant voltage, and when the voltage exceeds the predetermined voltage, the DC link unit (300) determines a reference value of the amount of electric current to be transmitted to the power system (G) by a magnitude corresponding thereto.

In order to transmit power to the power system (G), the DC/AC power converter in the power converter (310) operates in an inverter mode.

For example, the predetermined constant voltage may be set to 350 Vdc for a single-phase AC 220V and 620 Vdc for a three-phase AC 380V.

After the step (S31), the control unit (500) checks the charged state of the battery unit (210) through the battery part (200)(= S32).

In the step (S32), the next step is determined according to the charged state of the battery in the battery unit (210)(= S32). When the charged state of the battery is in the low voltage or the overvoltage state, the battery remaining amount scenario mode (S5) is performed. Alternatively, if the charged state of the battery is a normal voltage, the control unit determines the operation mode of the solar cell unit (110) (= step (S33)).

Detailed configuration and steps of the battery remaining amount scenario mode (S5) that can be performed after the step (S32) and the step (S32) will be described later with reference to separate drawings.

In the step (S32), if the charged state of the battery is a normal voltage, the control unit determines the operation mode of the solar cell unit (110) (=step (S33)). In the step (S33), the voltage PV of the electrical energy generated by the solar cell unit (110) is measured, and the control unit determines the next operation mode based on the measured voltage.

As the factor for determining whether to perform the next step in the step (S33), the initial operating voltage (PVr) at which the solar cell unit (110) starts to generate electricity or the current voltage (PV) of the electrical energy currently produced and generated is used.

In the step (S33), if the initial operating voltage (PVr) is greater than 150V, which is the operation start voltage, or the current voltage (PV) is within the operating sustain voltage range of more than 100V to less than 500V, the control unit confirms that the power generation of the solar cell unit (110) is normally performed. Therefore, unless the operation termination command is issued in the system of the present invention, the operation of the present invention is maintained by going back to the step (S1).

In the step (S33), if the initial operating voltage (PVr) is equal to or lower than 150V or the current voltage (PV) is out of the range and is measured to be 100 V or less or 500 V or more, the power generation of the solar cell unit (110) is stopped (=step (S34)).

When the step (S34) is performed, the power generation of the solar cell unit (110) is stopped. Nevertheless, since the DC load (D) must be continuously supplied with DC power, it is preferable to receive power from the power system (G) or the charged battery unit (210).

After performing the step (S34), the step (S2) is performed again.

The daytime operation may be performed by repeating the above steps.

If the current time (t) is determined to be at night in the step (S2), the control unit (500) operates the solar power generation energy storage system of the present invention in a night operation mode (= step (S41)).

If the DC link unit (300) maintains the predetermined voltage when the immediately preceding step operates in the daytime operation mode during the step (S41), the control unit switches the operation mode of the solar power generation energy storage system to the night operation mode through the step (S41) and the battery part (200) slowly increases the battery charge current value. The DC link unit (300) changes the grid current reference value to a negative value and the control unit controls the DC/AC power converter of the power converter unit (310) to operate in the converter mode so as to receive power from the power system (G).

In the daytime operation mode or the nighttime operation mode, the battery unit body (210) can stably supply power to the DC load unit (400) and the DC load (D).

In the step (S41), when the photovoltaic energy storage system operates its original operation mode as a night operation mode, the battery part (200) provides the DC link unit(300) with a constant voltage, for example, 350Vdc when the DC link unit(300) is single-phase 220Vac, and 620Vdc when it is three-phase 380V, through the battery unit (210) as a result of the battery discharge.

As described above, in the step (S41), while the operation mode of the photovoltaic energy storage system is switched into the night operation mode, the battery part (200) slowly increases the battery charge current value in order to receive power for charging the battery through the power system (G). The DC link unit (300) converts the grid current reference value to a negative value. The DC/AC power converter of the power conversion unit (310) operates in a converter mode.

The steps of providing stably supplying DC power of 48V to the DC load (D) through the DC load unit (400), providing electric power in the power system (G) by operating the DC/AC power converter of the power converter unit (310) in the converter mode, and maintaining the voltage of the power supplied to the DC load (D) may be further performed.

When electric power is supplied from the power system (G) as described above, the battery part (200) changes the current direction of its DC/DC converter to charge the battery of the battery unit (210) in a constant current mode or a constant voltage mode.

After the step (S41), the battery charged state of the battery unit (210) is checked (=step (S42)). In the step (S42), the battery remaining amount scenario mode (S5) is performed when the battery unit (210) is in a low voltage or an overvoltage state, as in the step (S32).

In the step (S42), the control unit confirms that the power generation of the battery unit (210) is maintained at a normal voltage. Therefore, unless the operation termination command is issued in the system of the present invention, the operation of the present invention is maintained by going back to the step (S1).

The nighttime operation may be performed by repeating the above steps.

FIG. 5 is a flowchart for showing the steps (S32, S42) of checking the charged state of the battery unit according to the present invention.

Hereinafter, a specific operation procedure of the steps (S32, S42) will be described with reference to FIG. 5.

As described above, the steps (S32, S42) are the step for determining whether to perform the battery remaining amount scenario mode (S5) by checking the charged state of the battery unit (210) and for determining whether to perform the next step in accordance with the daytime or nighttime operation. To this end, the steps (S32 and S42) first check the charged state of the battery unit (210) (= step (S321)).

The step (S321) includes the step of determining whether the charged state value (soc) of the battery is verifiable or not. The charged state value (soc) of the battery is a value indicating the degree of charging of the battery unit (210), and it may be expressed as a percentage. If the charged state value (soc) of the battery is 100%, it means that the battery unit (210) is completely charged, and if it is 0%, it means that the battery is not fully charged.

If a separate battery management system (BMS) is additionally installed in the battery unit (210) or the battery part (200) to easily check the charged state value (soc) of the battery, in the step (S321), the charged state value (soc) of the battery is checked to determine whether the battery unit (210) is in a low voltage, a normal voltage, or an overvoltage (= step (S322)).

In the step (S322), the control unit (500) or the battery part (200) may be provided with a minimum allowable soc value (soc_mi) and a maximum permissible allowable value (soc_mi) in order to determine whether the charged state value (soc) of the battery is in a normal voltage range or not.

Generally, the minimum allowable soc value (soc_mi) is inputted as 10%, and the maximum allowable soc value (soc_mx) is inputted as 90%. The minimum allowable soc value (soc_mi) and the maximum allowable soc value (soc_mx) are set in consideration of the lifetime of the batteries in the battery unit (210).

If the charged state value (soc) of the battery falls within the range of the minimum allowable soc value (soc_mi) to the maximum allowable soc value (soc_mx) in the step (S322), it belongs to the category of normal voltage. Then, after confirming that the battery in the battery unit (210) is operating at a normal voltage (= step (S324)), the control unit controls the operation of the solar power generation storage system as shown in FIG. 4.

In the step (S322), if the charged state value of battery (soc) is less than the minimum allowable soc value (soc_mi), it is determined to be in a low voltage state. If the charged state of battery (soc) is greater than the maximum allowable soc value (soc_mx), it is determined to be in an overvoltage state. Then, the battery remaining amount scenario mode (S5) is performed.

In the step (S321), if the charged state of battery (soc) cannot be confirmed because the battery management system is not installed separately in the battery unit (210) or the battery part (200), the voltage of the battery is checked on the basis of the battery voltage value BV in the battery unit (210) (= step (S323)). The battery voltage value (BV) is expressed as a percentage, and it is preferable that the battery voltage value (BV) is expressed as 100% at the rated voltage.

In the step (S323), the control unit (500) or the battery part (200) may be provided with a minimum allowable voltage value (BV_mi) and a maximum allowable voltage value (BV_mx), which are inputted in advance, in order to determine whether the battery voltage value (BV) is in the normal voltage range or not.

Generally, when the battery voltage value (BV) is taken as 100% based on the rated voltage 12V, the minimum allowable voltage value (BV_mi) may be inputted at 85% and the maximum allowable voltage value (BV_mx) may be inputted at 120%. The minimum allowable voltage value (BV_mi) and the maximum allowable voltage values (BV_mx) may be adjusted in consideration of the lifetime of the batteries in the battery unit (210) or the rated voltage value.

In the step (S323), if the battery voltage value (BV) falls within the range of more than the minimum allowable voltage value (BV_mi) to less than the maximum allowable voltage value (BV_mx), it belongs to the category of normal voltage. Then, after confirming that the battery in the battery unit (210) is operating at a normal voltage (= step (S324)), the control unit controls the operation of the solar power generation storage system as shown in FIG. 4.

In the step (S322), if the battery voltage value (BV) is equal to or is less than the minimum allowable voltage value (BV_mi), it is determined to be in a low voltage state. If the battery voltage value (BV) is equal to or is greater than the maximum allowable voltage value (BV_mx), it is determined to be in an overvoltage state. Then, the battery remaining amount scenario mode (S5) is performed.

The steps (S32, S42) are performed in the same order as described above.

FIG. 6 is a flowchart for showing the step of performing a battery remaining amount scenario mode (S5) according to the present invention.

Hereinafter, the concrete procedure of the battery remaining amount scenario mode (S5) will be described with reference to FIG. 6.

As described above, the battery remaining amount scenario mode (S5) is performed when the battery in the battery unit (210) is in a low voltage or an overvoltage state, as in the step (S32, S42).

When the battery remaining amount scenario mode (S5) is started, it is first determined whether the battery in the battery unit (210) is in a low voltage or an overvoltage. Therefore, the step of determining whether the battery in the battery unit is in a low voltage or an overvoltage is performed (=step (S51)).

The charged state value of battery (soc), and the minimum and maximum allowable soc values (soc_mi, soc_mx) related thereto, or the battery voltage value (BV) and the allowable battery voltage values (BV_mi, BV_mx) related to the battery voltage value (BV) may be used as an element for determining whether the battery in the battery unit (210) is in a low voltage or an overvoltage in the above step.

In the step (S51), if the charged state value of battery (soc) is less than the minimum allowable soc value (soc_mi) or the battery voltage (BV) is less than the minimum allowable battery voltage value (BV_mi), the batteries in the unit (210) are in a low-voltage state. Then, the control unit (500) warns the low-voltage state of the battery to the user through a display or the like (= step (S52)).

The execution of the step (S52) means that the charged amount of the battery is almost not remaining. Then, it is preferred that the control unit (500) draws power from the power system G and provides it to the DC load (400) at a stable constant voltage of DC48V.

The situation in which the battery is not properly charged in the battery unit (210) occurs when the solar cell unit (110) has a problem in producing electrical energy due to weather deterioration in the daytime. Under this situation, it is preferred that the control unit (500) forcibly draws power from the power system (G).

Therefore, it is preferable that the step (S52) includes a separate procedure for supplying power to the DC load unit (400) by receiving power from the power system (G).

Also, in the step (S52), the charge count (cn), which is a counter that rises one by one, is initialized to a default value (%d). The default value (%d) can be changed and set as needed by the administrator, but it is preferable to set the default value to 0 or 1 easily.

After performing the step (S52), the control unit (500) determines whether the battery is in a low voltage state or not (= step (S53)).

In the step (S53), the control unit (500) determines whether the batteries in the battery unit (210) go wrong or not by using the limit permissible voltage value (BV_lim) and the maximum charge count (cmx) inputted in advance in the control unit (500) or the battery part (200).

More specifically, the limit allowable voltage value (BV_lim) is set to determine whether the batteries are faulty or not, and it is set to a value lower than the minimum allowable voltage value (BV_mi). For example, if the minimum allowable voltage value (BV_mi) is set to 85%, the limit allowable voltage value (BV_lim) may be set to about 80%.

The maximum charge count (cmx) is a counter that rises one by one as the next step proceeds, and is set to be larger than the default value (%d) of the charge count (cn),

In the step (S53), if the currently measured battery voltage value (BV) is lower than the limit allowable voltage value (BV_lim) and the charge count (cn) which is raised at the time of charging the battery at the next step is less than the maximum charge count (cmx), the control unit (500) checks a functional problem such as failure, breakage, or shortened life of the battery occurs.

Then, after the step (S55) of reporting that the battery is in a low voltage error state, the operation of the present invention is maintained by going back to the operation state of the photovoltaic energy storage system as a daytime operation or a nighttime operation as shown in FIG. 4. Then, the control unit (500) immediately terminates the operation of all the systems by performing the emergency termination step (S11) based on the detected battery errors.

However, since the charge count (cn) does not exist or is set to zero(0) or 1, it is lower than the maximum charge count (cmx) when the system goes into the step (S53) for the first time. The step (S54) of charging the battery is performed first without going directly to the step (S55).

The batteries in the battery unit (210) can be charged by adding the used current of the DC load (D) to the reference charging current value so that they may be charged taking into consideration the power used by the DC load (D).

It is preferable to supply power to the batteries in the battery unit (210) through the power system (G).

This is because, as described in the step (S52), a state in which the battery is in a low voltage is a problem that the power generation of the solar cell unit (110) is not stably performed due to reasons such as weather.

In the step (S54), the control unit (500) performs charging of all of the batteries in the battery unit (210), and determines whether the battery is fully charged or not based on the charging time (ct), the rated voltage value (RV), and the charge allowable soc value (soc_ps).

The rated voltage value (RV) is a rated voltage value of the batteries in the battery unit (210) that is inputted to the control unit (500) or the battery part (200) in advance. For example, when the battery is constituted by one 12V battery, the rated voltage value (RV) will be 12V. When eight 12V batteries are connected in series, the rated voltage value RV will be 96V.

The charging allowable soc value (soc_ps) is also a value that is inputted to the control unit (500) or the battery part (200) in advance and it is generally larger than the minimum allowable soc value (soc_mi) and smaller than the maximum allowable soc value (soc_mx). For example, through repeated experiments, the inventors of the present invention have found that the charge allowable soc value (soc_ps) should be set to about 60%.

In the state set as described above, it is preferable that the charging of the battery in the step (S54) is performed for at least 2 hours. Accordingly, the control unit determines whether the charging time (ct), which is to be measured from the start of charging, is 2 hours or more. The charging of the batteries is repeated until the charging time (ct) exceeds 2 hours. If the charging time (ct) exceeds 2 hours, the control unit (500) measures the degree of charging to date based on the battery charged state value (soc) or the battery voltage value (BV).

After charging for at least 2 hours as described above, if the battery charged state value (soc) exceeds the charge allowable soc value (soc_ps) inputted in advance or the battery voltage value (BV) exceeds the rated voltage value (RV), it means that all the batteries in the battery unit (210) are sufficiently charged. Then, the operation of the present invention is maintained by going back to the operation state of the photovoltaic energy storage system as a daytime operation or a nighttime operation as described above.

Alternatively, after charging for at least 2 hours as described above, if the battery charged state value (soc) is equal to or is less than the charge allowable soc value (soc_ps) inputted in advance or the battery voltage value (BV) is equal to or is less than the rated voltage value (RV), it means that all the batteries in the battery unit (210) do not sufficiently charged. Then, one is added to the charge count (cn) and the step (S53) is performed again.

The charging of the battery in the battery unit (210) is repeatedly performed in the same manner as described above. However, as described above, if the battery is not sufficiently charged despite the repetition of the charging step (S54) for a predetermined number of times or more, as described above, this is a problem in the battery, so that in the step (S53), and can terminate the process. in the step (S53), the control unit senses this fact and reports the user of the error (= step (S55)), and terminates the charging of the battery.

The corresponding procedure when the battery is in the low voltage state may be performed in the above-described procedure.

In the step (S51), if the battery charged state value (soc) exceeds the maximum allowable soc value (soc_mx) or the battery voltage value (BV) is equal to or greater than the maximum allowable voltage value (BV_mx) in the step S51, the control unit (500) confirms the fact that the batteries in the unit (210) are overcharged.

The control unit (500) alerts the overvoltage state of the battery to the manager (= step (S56)), and causes the battery part (200) to block the charging of the batteries in the battery unit (210) (= Step (S57)).

If the step (S57) is performed, charging of the battery unit (210) is stopped. However, the batteries in the battery unit (210) must continuously supply a constant voltage to the DC load unit (400). As a result, the charged amount of the battery can be reduced naturally and continuously.

After the step (S57), the control unit (500) checks whether the battery voltage is in a normal state. If the battery voltage is determined to be a normal voltage, the operation of the present invention is maintained by going back to the operation state of the photovoltaic energy storage system as a daytime operation or a nighttime operation as described above.

FIG. 7 is a flowchart illustrating a procedure for replacing a battery in the battery unit (210) in the solar energy storage system of the present invention. Hereinafter, the battery replacement procedure will be described with reference to FIG. 7.

As described with reference to FIG. 6, the photovoltaic generation energy storage system of the present invention can detect a situation where the battery in the battery unit (210) does not operate normally due to the end of its life, failure, or breakage.

If such a problem as described above occurs, the manager must replace the battery in the battery unit (210). Even in the battery replacement situation, the manager must continuously supply a constant voltage to the DC load unit (400) in order not to interrupt the power supply to the DC load (D).

For this purpose, when the administrator selects the battery replacement mode through the control unit (500), the control unit (500) performs the step (S61) of setting the control unit to a battery replacement mode.

In the step (S61), the control unit (500) determines whether the photovoltaic energy storage system of the present invention is operated in a daytime operation mode or a nighttime operation mode. If the photovoltaic energy storage system according to the present invention is currently operated in the daytime operation mode in the step (S61), the control unit (500) changes the current operation of the photovoltaic energy storage system to the nighttime operation mode regardless of the time (= step (S62)).

The reason for doing the above is as follows. When the photovoltaic energy storage system according to the present invention operates in the daytime operation mode and receives the electrical energy produced by the solar cell unit (110), the electrical energy may vary depending on the irradiation dose. If there is a situation in which the DC load unit (400) is not sufficiently supplied with the constant voltage required by the DC load unit (400), a malfunction may occur in supplying electricity to the DC load under circumstances where the battery unit (210) cannot supply additional electricity.

Therefore, it is preferable that the operation mode of the photovoltaic energy storage system is changed to the night operation mode, and power is supplied from the system power source (G) to the DC load unit (400) in a stable manner.

If the step (S62) is performed or if the current night mode is being executed, a battery replacement step (S63) is performed.

In the step (S63), the DC/DC converter in the battery part (200) changes to the constant voltage charging mode and maintains the constant voltage when the constant current charging is proceeding. For example, after setting the voltage of the DC/DC converter to the voltage of the battery to be replaced, the electromagnetic contactor in the battery part (200) is disconnected to remove the battery and replace it with a new battery.

The reason for changing into the constant voltage charging mode as described above is to allow the DC/DC converter of the DC load unit (400) to continuously supply a constant voltage to the DC load using the voltage.

The reason for matching the voltage of the DC/DC converter to a constant voltage, in particular, the voltage of the battery to be replaced is that a large current may be generated between the battery unit (210) and the battery part (200) according to the voltage difference when the battery voltage is different from the predetermined voltage. This is because a large current may be generated between the converters.

When the battery replacement is completed through the step (S63), the manager inputs the completion of the battery replacement through the control unit (500). Then, the operation of the present invention is maintained by going back to the operation state of the photovoltaic energy storage system as a daytime operation or a nighttime operation as described above.

All patents and publications mentioned in this specification are indicative of the levels of those skilled in the art to which the invention pertains. All patents and publications are herein incorporated by reference to the same extent as if each individual publication was specifically and individually indicated to be incorporated by reference. It is to be understood that while a certain form of the invention is illustrated, it is not intended to be limited to the specific form or arrangement herein described and shown. It will be apparent to those skilled in the art that various changes may be made without departing from the scope of the invention and the invention is not to be considered limited to what is shown and described in the specification. One skilled in the art will readily appreciate that the present invention is well adapted to carry out the objectives and obtain the ends and advantages mentioned, as well as those inherent therein. The systems, methods, and devices described herein are presently representative of the preferred embodiments, are intended to be exemplary and are not intended as limitations on the scope. Changes therein and other uses will occur to those skilled in the art which are encompassed within the spirit of the invention. Although the invention has been described in connection with specific, preferred embodiments, it should be understood that the invention as ultimately claimed should not be unduly limited to such specific embodiments.

Claims (11)

  1. A photovoltaic energy storage system using more than one battery, the photovoltaic energy storage system comprising:
    a solar cell unit including at least one solar cell;
    a solar battery unit for controlling a power produced by the solar cell unit and including a DC/DC converter;
    a solar cell breaker being installed between the solar cell unit and a solar battery unit;
    a DC link unit being installed between the solar battery unit and a power system;
    a power conversion unit being installed between the DC link unit and the power system and including a DC/AC bidirectional power converter;
    a battery unit including at least one battery and being capable of storing an electrical energy;
    a battery part for controlling charging of the battery unit and being connected to the solar battery unit and the power conversion unit by using the DC link unit as a contact point, the battery part including a DC/DC converter;
    a battery breaker and a battery switch being installed between the battery part and the battery unit;
    a DC load unit being connected between the battery part and a DC load, the DC load unit including a DC/DC converter for supplying a DC power to the DC load; and
    a control unit for controlling operations of the solar battery unit, the battery part, the DC link unit, the power conversion unit, and the DC load unit.
  2. A method of controlling a solar photovoltaic energy storage system for supplying a power to a DC load and for charging a battery by using the photovoltaic energy storage system as claimed in claim 1, the method comprising the steps of:
    (S1) checking the overall system status of the solar photovoltaic energy storage system;
    (S2) confirming that the current time (t) belongs to the daytime if the control unit determines that the current time (t) exceeds the daytime boundary time (td) and falls within the range below the nighttime boundary time (tn), and confirming that the current time (t) belongs to the nighttime if the control unit determines that the current time (t) exceeds the daytime boundary time (td) and it is outside the range, when the overall system is normal in the step (S1);
    (S31) operating the photovoltaic energy storage system as a daytime operation mode, if it is determined that the current time (t) belongs to the daytime in the step (S2);
    (S32) checking the charged state of the battery unit after the step (S31);
    (S33) performing a battery remaining amount scenario mode (S5) if the charged state of the battery in the battery unit is in the low voltage state or the overvoltage state in the step (S32), and determining the operation of the solar cell unit by measuring a voltage (PV) of electric energy produced by the solar cell unit if the charged state of the battery in the battery unit is the normal voltage in the step (S32);
    performing the step (S1) if an initial operating voltage (PVr) is greater than 150V, which is the operation start voltage, or the current voltage (PV) is within the operating sustain voltage range of more than 100V to less than 500V in the step (S33), and performing an operation standby mode (S34) for stopping the power generation of the solar cell unit when the initial operating voltage (PVr) is equal to or lower than 150V or the current voltage (PV) is out of the operating sustain voltage range in the step (S33), and performing the step (S2) after the step (S34);
    (S41) operating the photovoltaic energy storage system as a nighttime operation mode if the current time (t) belongs to the nighttime in the step (S2);
    (S42) checking the charged state of the battery unit after the step (S41); and
    performing the battery remaining amount scenario mode (S5) when the charged state of the battery in the battery unit is in the low voltage state or in the overvoltage state in the step (S42), and performing the step (S1) if the charged state of the battery in the battery unit is in the normal voltage state in the step (S42).
  3. The method of controlling a solar photovoltaic energy storage system, as claimed in claim 2, wherein in the step (S31), the DC/DC converter in the solar battery unit operates in the maximum power point tracking mode, and the DC/AC power converter in the power conversion unit operates in the inverter mode.
  4. The method of controlling a solar photovoltaic energy storage system, as claimed in claim 2, wherein in the step (S41), the DC/AC power converter in the power conversion unit operates in the converter mode, and the grid current reference value of the DC link unit becomes a negative (-) value.
  5. The method of controlling a solar photovoltaic energy storage system, as claimed in claim 2, wherein in the steps (S31) and (S41), the battery unit supplies DC power to the DC load unit.
  6. The method of controlling a solar photovoltaic energy storage system, as claimed in claim 2, wherein the method further comprises the steps of:
    (S321) determining whether the charged state value (soc) of the battery is verifiable or not to confirm the charged state of the battery when the steps (S32, S42) are started;
    (S322) comparing the charged state value (soc) with the minimum allowable sic value (soc_mi) and the maximum allowable sic value (soc_mx), which are inputted in advance, if the charged state value (soc) is confirmed in the step (S321);
    (S324) confirming the charged state of the battery is normal if the charged state value (soc) is equal to or greater than the minimum allowable soc value (soc_mi) and is equal to or less than the maximum allowable soc value (soc_mx), and ending the steps (S32, S42) after the step (S324);
    performing the step (S5) if the charged state value (soc) is less than the minimum allowable soc value (soc_mi) or is greater than the maximum allowable soc value (soc_mx) in the step (S322);
    (S323) comparing the voltage value (BV) of the battery with the minimum permissible voltage value (BV_mi) and the maximum allowable voltage value (BV_mx), if it is impossible to confirm the charged state value (soc) in the step (S321);
    (S324) confirming the charged state of the battery is in the normal state if the voltage value (BV) of the battery is greater than the minimum permissible voltage value (BV_mi) and is less than the maximum allowable voltage value (BV_mx), and then ending the steps (S32, S42) after the step (S324); and
    performing the step (S5) if the voltage value (BV) of the battery is equal to or less than the minimum allowable soc value (soc_mi) and is equal to or greater than the maximum allowable soc value (soc_mx) in the step (S323).
  7. The method of controlling a solar photovoltaic energy storage system, as claimed in claim 2, wherein the method further comprises the steps of:
    (S51) determining whether the battery in the battery unit is in the low voltage state or in the overvoltage state when the battery remaining amount scenario mode (S5) is started;
    (S52) warning the user about that the battery is in the low voltage state when the batteries in the battery unit are determined to be in the low voltage state in the step (S51);
    (S53) checking the low voltage state of the battery after the step (S52);
    (S55) reporting the fact that the battery is in the low voltage state, if the current battery voltage value (BV) is lower than the limit permissible voltage value (BV_lim) inputted in advance and the charge count (cn) is higher than the maximum charge count (cmx) inputted in advance in the step (S53), and then performing the step (S1) after the step (S55);
    (S54) charging the battery if the current battery voltage value (BV) is equal to or higher than the limit permissible voltage value (BV_lim) or if the charge count (cn) is equal to or smaller than the maximum charge count (cmx) in the step (S53);
    (S56) alerting the user about that the battery is in the overvoltage state if it is determined that the batteries in the battery unit are in the overvoltage state in the step (S51); and
    (S7) stopping the charging of the battery unit (210) after the step (S56), and then performing the step (S51) after the step (S56).
  8. The method of controlling a solar photovoltaic energy storage system, as claimed in claim 7, wherein in the step (S54), the charging of the battery unit is started, and the control unit judges whether the charging time exceeds 2 hours or not, and then the battery is charged until the charging time (ct) exceeds 2 hours.
  9. The method of controlling a solar photovoltaic energy storage system, as claimed in claim 7, wherein the method further comprises the steps of:
    performing the step (S1) if the battery charged state value (soc) exceeds a charge allowable soc value (soc_ps) inputted in advance or the battery voltage value (BV) is more than the rated voltage value (RV), after charging the battery unit in the step (S54); and
    performing the step (S53) by adding one to the current charge count (cn) if the battery charged state value (soc) is less than the charge allowable soc value (soc_ps) and the battery voltage value (BV) is less than the rated voltage value (RV), after charging the battery unit in the step (S54).
  10. A method for replacing a battery in the battery unit in the solar photovoltaic energy storage system as claimed in claim 1, the method comprising the steps of:
    (S61) setting the control unit to a battery replacement mode;
    (S62) changing the operation mode of the solar photovoltaic energy storage system from the daytime operation mode into the nighttime operation mode when the photovoltaic energy storage system is operated in the daytime operation mode;
    (S63) replacing the battery with a new battery if the step (S62) is performed or if the nighttime operation mode is executed, by disconnecting the electromagnetic contactor in the battery part; and
    releasing the battery replacement mode after ending the step (S63).
  11. The method for replacing a battery in a battery unit in a solar photovoltaic energy storage system as claimed in claim 10, wherein the operation mode of the DC/DC converter in the battery part is changed to the constant voltage charging mode and then it is maintained at a constant voltage before turning off the electromagnetic contactor in the battery unit in the step (S62).
PCT/KR2018/006434 2018-06-07 2018-06-07 Solar energy storage system divided into daytime and night mode, and its operation method and battery replacement method thereof WO2019235657A1 (en)

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