KR101639945B1 - Electricity providing system including battery energy storage system - Google Patents

Abstract

A battery power supply system is disclosed. The battery power supply system according to an embodiment of the present invention controls ON / OFF of input / output converted power, determines a switching loss caused by the power ON / OFF, blocks a battery rack constituting the battery And a battery energy storage system for charging / discharging electric power based on a result of the determination by the charge controller.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a power supply system including a battery power supply system,

The present invention provides an auxiliary service in a power system, and more particularly, to a method and system for minimizing heat loss that may occur due to the input / output of electrical energy.

A battery power supply system is a storage device that stores power generated at a power plant or generates irregularly generated renewable energy, and then transits when power is temporarily low.

Specifically, a battery power supply system is a system that stores electricity in an electric power system to supply energy when and where it is needed. In other words, it is a collection of systems that are integrated into one product, such as a conventional secondary battery.

The importance of battery power supply system is emerging as an indispensable device to store unstable power generation energy in wind power generation, which is a rapidly growing new renewable energy, and to supply it to the power system in a stable manner when necessary. If there is no battery power supply system, unstable power supply depending on wind or sunlight can cause serious problems such as sudden shutdown of power system. Therefore, storage is becoming a very important field in this environment, and it is being extended to home power storage systems.

These battery power supply systems are installed in power generation, transmission, distribution, and customer in the power system. They are used for frequency regulation, generator output stabilization by using renewable energy, peak shaving, load leveling ), And emergency power source.

Battery power supply systems are divided into physical energy storage and chemical energy storage depending on the storage method. Physical energy storage includes pumped storage, compressed air storage, and flywheel. Chemical storage includes lithium ion batteries, lead acid batteries, and Nas batteries.
Also, as a background of the invention, Patent Publication No. 10-2013-0062894 (2013.06.13.) Has been introduced.

A battery power supply system according to an embodiment of the present invention aims at minimizing switching loss due to input / output of electric energy by blocking a part of a plurality of batteries.

In particular, the present invention aims at minimizing the switching loss due to the input / output of electric energy by using the point where the voltage level changes according to the SOC (State of Charge) of the battery energy storage system.

The battery power supply system according to an embodiment of the present invention controls ON / OFF of input / output converted power, determines a switching loss according to the power ON / OFF, A control unit; And

And a battery energy storage system for charging / discharging electric power based on the determination result of the charge controller.

At this time, the charge control unit may calculate the switching loss and compare the calculated value with a preset value to determine the switching loss.

At this time, the charge control unit senses a temperature rise caused by the switching loss, and compares the sensed temperature with a preset value to determine the switching loss.

At this time, the charge controller can determine the number of battery racks to be shut off according to the determination result of the switching loss.

A method of controlling a battery power supply system according to an embodiment of the present invention includes: controlling on / off of a converted power input / output; determining a switching loss in accordance with the power on / off; And blocking some battery racks constituting the battery energy storage system.

The battery power supply system according to an embodiment of the present invention can block some of a plurality of batteries and minimize switching loss due to input / output of electric energy.

In particular, the switching loss due to the input / output of electric energy can be minimized by utilizing the point where the voltage level is changed according to the SOC (State of Charge) of the battery energy storage system.

1 is a block diagram showing an overall configuration of a battery power supply system.
2 is a block diagram of a power supply system in accordance with an embodiment of the present invention.
3 is a block diagram of a small capacity power supply system according to an embodiment of the present invention.
4 is a conceptual diagram illustrating a power market structure according to an embodiment of the present invention.
5 is a graph for explaining the switching loss.
6 is a flowchart illustrating an operation method of a battery power supply system according to an embodiment for solving the switching loss problem.

Hereinafter, embodiments related to the present invention will be described in detail with reference to the drawings. The suffix "module" and " part "for the components used in the following description are given or mixed in consideration of ease of specification, and do not have their own meaning or role.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention and the manner of achieving them will become apparent with reference to the embodiments described in detail below with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the invention to those skilled in the art. Is provided to fully convey the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout the specification.

In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear. The following terms are defined in consideration of the functions in the embodiments of the present invention, which may vary depending on the intention of the user, the intention or the custom of the operator. Therefore, the definition should be based on the contents throughout this specification.

Combinations of the steps of each block and flowchart in the accompanying drawings may be performed by computer program instructions. These computer program instructions may be embedded in a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus so that the instructions, which may be executed by a processor of a computer or other programmable data processing apparatus, Thereby creating means for performing the functions described in the step. These computer program instructions may also be stored in a computer usable or computer readable memory capable of directing a computer or other programmable data processing apparatus to implement the functionality in a particular manner so that the computer usable or computer readable memory It is also possible to produce manufacturing items that contain instruction means that perform the functions described in each block or flowchart illustration in each step of the drawings. Computer program instructions may also be stored on a computer or other programmable data processing equipment so that a series of operating steps may be performed on a computer or other programmable data processing equipment to create a computer- It is also possible for the instructions to perform the processing equipment to provide steps for executing the functions described in each block and flowchart of the drawings.

Also, each block or each step may represent a module, segment, or portion of code that includes one or more executable instructions for executing the specified logical function (s). It should also be noted that in some alternative embodiments, the functions mentioned in the blocks or steps may occur out of order. For example, two blocks or steps shown in succession may in fact be performed substantially concurrently, or the blocks or steps may sometimes be performed in reverse order according to the corresponding function.

1 is a block diagram showing an overall configuration of a battery power supply system. 1, the battery power supply system 1 may constitute one platform with the power plant 2, the factory 3, the home 4 and another power plant or consumer 5 .

According to one embodiment of the present invention, the energy produced in the power plant 2 may be stored in the battery power supply system 1. [ Further, the energy stored by the battery power supply system 1 may be transmitted again to the factory 3 or the home 4, and may be sold to other power plants or consumers.

Specifically, the electrical energy produced by the power plant 2 varies greatly depending on the environment and time. For example, in the case of photovoltaic power generation, production may vary depending on weather conditions or sunrise times. If the variation is large, it may be difficult to stably use the produced electric energy in the factory 3 or the home 4. Therefore, the electric energy produced by the power plant can be temporarily stored in the battery power supply system, and the stored electric energy can be reliably output to be used in the factory 3 or the home 4. It is also possible to sell the remaining used electric energy to another consumer (5). It is also possible to purchase electric energy from another power plant 5 when the electric energy stored in the battery power supply system 1 is consumed in the factory 3 or the home 4.

2 is a block diagram of a battery power supply system in accordance with an embodiment of the present invention.

The power supply system 100 according to an embodiment of the present invention includes a power generation apparatus 101, a DC / AC converter 103, an AC filter 105, an AC / AC converter 107, a system 109, A battery energy storage system 113, a system control unit 115, a load 117, and a DC / DC converter 121. [

The power generation apparatus 101 produces electrical energy. When the power generation apparatus is a solar power generation apparatus, the power generation apparatus 101 may be a solar cell array. A solar cell array is a combination of a plurality of solar cell modules. The solar cell module is a device for connecting a plurality of solar cells in series or in parallel to convert solar energy into electrical energy to generate a predetermined voltage and current. Thus, a solar cell array absorbs solar energy and converts it into electric energy. When the power generation system is a wind power generation system, the power generation apparatus 101 may be a fan that converts wind energy into electric energy. However, as described above, the power supply system 100 can supply power only through the battery energy storage system 113 without the power generation apparatus 101. [ In this case, the power supply system 100 may not include the power generation apparatus 101.

The DC / AC converter 103 converts the DC power to AC power. DC power supplied by the power generation apparatus 101 or the DC power discharged by the battery energy storage system 113 is supplied through the charge control unit 111 and is directly converted into AC power.

The AC filter 105 filters the noise of the power converted into AC power. In accordance with a specific embodiment, the AC filter 105 may be omitted.

The AC / AC converter 107 converts the magnitude of the voltage of the filtered AC power so that the AC power can be supplied to the system 109 or the load 117 to supply power to the system 109 or the independent load. According to a specific embodiment, the AC / AC converter 107 may be omitted.

The system 109 is a system in which many power plants, substations, transmission / distribution lines, and loads are integrated to generate and utilize electric power.

The battery energy storage system 113 receives electric energy from the power generation apparatus 101 and charges it and supplies electric power to the system 109 or the load 117 And discharges the charged electric energy according to the supply and demand situation. Specifically, when the system (109) or the load (117) is light, the battery energy storage system (113) receives and supplies the idle power from the power generation apparatus (101). When the system 109 or the load 117 is overloaded, the battery energy storage system 113 discharges the charged power to supply power to the system 109 or the load 117. The power supply / demand situation of the system 109 or the load 117 may have a large difference by time. Therefore, it is inefficient that the power supply system 100 uniformly supplies the power supplied by the power generation apparatus 101 without considering the power supply / demand situation of the system 109 or the load 117. Therefore, the power supply system 100 uses the battery energy storage system 113 to adjust the amount of power supply according to the power supply situation of the system 109 or the load 117. [ Whereby the power supply system 100 can efficiently supply power to the system 109 or the load 117. [

The DC / DC converter 121 converts the magnitude of the DC power supplied or supplied by the battery energy storage system 113. The DC / DC converter 121 may be omitted depending on the specific embodiment.

The system control unit 115 controls the operation of the DC / AC converter 103 and the AC / AC converter 107. The system control unit 115 may include a charge control unit 111 for controlling charging and discharging of the battery energy storage system 113. The charge control unit 111 controls charging and discharging of the battery energy storage system 113. When the system 109 or the load 117 is overloaded, the charge controller 111 receives power from the battery energy storage system 113 and transfers power to the system 109 or the load 117. When the system (109) or the load (117) is light, the charge control unit (111) receives power from an external power supply or power generation apparatus (101) and transfers it to the battery energy storage system (113).

3 is a block diagram of a small capacity power supply system according to an embodiment of the present invention.

The small capacity power supply system 200 according to an embodiment of the present invention includes a generator 101, a DC / AC converter 103, an AC filter 105, an AC / AC converter 107, a system 109, DC converter 119, a load 117, and a DC / DC converter 121. The control unit 111 includes a control unit 111, a battery energy storage system 113, a system control unit 115, a DC / DC converter 119,

2, but also includes a DC / DC converter 119. The DC / The DC / DC converter 119 converts the voltage of the DC power generated by the power generation device 101. In the small capacity power supply system 200, the voltage of the power produced by the power generation apparatus 101 is small. Therefore, step-up is necessary to input the power supplied by the power generation apparatus 101 to the DC / AC converter. The DC / DC converter 119 converts the voltage to the magnitude of the voltage that can be input to the DC / AC converter 103 by the voltage of the power produced by the power generator 101.

4 is a conceptual diagram illustrating a power market structure according to an embodiment of the present invention.

Referring to FIG. 4, the electric power market structure includes power generation subsidiaries, independent power generation companies, PPA providers, regional electricity providers, Korea Electric Power Corporation, Korea Electric Power Corporation, consumers, large-scale consumers and specific-area consumers. As mentioned above, there are 6 power generation subsidiaries separated from KEPCO and 288 independent power generation companies as of 2014.

Power generation subsidiaries, independent power generation subsidiaries, PPA operators, and zone electric companies can signify power generation companies, and each of them can bid for the available capacity based on the amount of power that can be generated from their own power generation equipment, Can be obtained.

Each of the power generation subsidiaries and independent power generation companies bids the amount of electricity that can be supplied by each generator owned by the generator to the KEPCO every day, and KEPCO is responsible for the operation of the electric power market.

KEPCO purchases electricity at a price determined in the electricity market and supplies the purchased electricity to consumers. Accordingly, KEPCO is responsible for transmission, distribution and sales.

The PPA operator may refer to a power purchase agreement (PPA) operator, and the PPA operator bids the electric power capacity in the aforementioned electric power market. In addition, the PPA operator shall settle the electricity trading price by applying the price based on the supply contract with KEPCO, not the amount determined in the electricity market. And the settlement rule can be included in the power market settlement rule information.

Zone operators are operators that produce electricity through a certain scale of power generation facilities and directly sell the electricity produced within the licensed zone. In addition, the district electric companies can directly purchase the scarce electricity from KEPCO or the electric power market, or sell surplus electric power to KEPCO or electric power market.

On the other hand, large-capacity customers with contracts of 30,000 kW or more can purchase the necessary electricity directly from the electric power market without going through the Korea Electric Power Corporation.

Charge / discharge of electric energy (electric power) through the battery energy storage system 113 in the electric power supply system 100 is continuously performed. Therefore, for charge / discharge of the battery energy storage system 113, the charge control unit 111 continuously converts the electric energy. For example, the magnitude of the voltage can be changed. At this time, the electric energy to be charged / discharged into the battery energy storage system 113 is a DC type, and unlike the AC type electric energy, the conversion is not simple.

DC-to-DC conversion is basically performed by dividing the current or voltage of the DC into a square wave pulse, and then making a square wave DC current or voltage through filtering to flatten it.

At this time, the current or voltage is split through the switching element. Specifically, the switching element can be quickly and cyclically turned on / off so that the electric energy applied to the filter can be performed in a manner that indicates a pulse shape.

The frequency at which the switching element is turned on / off is referred to as a switching frequency, and may be specifically an inverse number of the switching period. The higher the switching frequency, the cleaner the output voltage can be without ripple. As the switching frequency increases, the size of the inductor L or the capacitor C can be reduced.

On the other hand, there may be a loss due to overlapping of current and voltage in the switching transient period, for example, heat loss may occur. In this way, a loss including heat generated by switching can be referred to as a switching loss. Hereinafter, switching loss will be described in more detail with reference to FIG.

5 is a graph for explaining the switching loss.

In Fig. 5, "ON" refers to a state in which the resistance between both ends of the switch becomes small, so that no voltage drop occurs even when a current flows. Since the voltage is zero, the power across the switch is zero (power = current vs. voltage).

OFF means a state in which the resistance between both ends of the switch is sufficiently large so that no current can flow and only a voltage is applied. Since the current is zero, the power across the switch is zero.

As shown in Fig. 5, most of the semiconductor switches start to decrease after the current rises when the voltage is turned on, and then decrease when the voltage rises when the voltage rises.

Therefore, in an actual circuit other than the ideal circuit, a period where the product (power) of the current and the voltage is not 0 as shown in FIG. 5 may appear, and the corresponding period may be referred to as the transient time. And the heat that can occur in the transient time can be called the switching loss.

In DC-to-DC conversion, it is necessary to increase the switching frequency in order to clean the input / output power without pulsation. However, as the switching frequency increases, the transient section increases and the switching loss power increases.

As a result, as the switching frequency increases, the switching loss increases and the efficiency of the entire system decreases. In addition, the switching loss can be expressed as a product of voltage, current, and switching frequency.

6 is a flowchart illustrating an operation method of a battery power supply system according to an embodiment for solving the switching loss problem.

The charge controller 111 turns ON / OFF the current input / output to / from the battery (S101). Specifically, the charge controller 111 converts the DC power between charge / discharge of the battery. The DC power may include DC current and DC voltage. In this case, DC power input / output can be performed in the conversion process, and the charge controller 111 for controlling charge / discharge of each battery can control input / output of electric power. In another embodiment, the charge control section 111 can control the input / output of power to the battery energy storage system 113 based on the control of the system control section 115. [

In a specific embodiment, the switch included in the charge controller 111 can control the input / output of power. The switch may comprise a MOSFET (Metal Oxide Silicon Field Effect Transistor) or an IGBT (Insulated Gate Bipolar Mode Transistor).

The charge control unit 111 can calculate the switching loss while controlling the input / output of electric power through the switch. Specifically, the charge control unit 111 can know the voltage and current value of input / output electric power. In addition, since the main control unit for controlling the switching period is the charge control unit 111, the charge control unit 111 can know up to the switching frequency value.

Therefore, since the switching loss can be calculated as a product of the current, voltage, and switching frequency of the input / output power, the charge controller 111 can calculate the current switching loss.

The charge controller 111 determines whether the calculated value of the switching loss is equal to or greater than a predetermined level (S105). Specifically, the charge controller 111 determines whether the switching loss calculated in step S103 is an acceptable value in the entire battery power supply system 1. [ In this case, the predetermined level may be a predetermined value in the system design for efficient operation of the battery power supply system 1.

In another embodiment, the charge controller 111 may send the calculated switching loss value to the system controller 115. [ In this case, the system control unit 115 can determine whether the switching loss value is equal to or higher than a predetermined level.

At this time, if the charge control unit 111 (or the system control unit 115) determines that the calculated switching loss value is equal to or higher than a predetermined level, the charge control unit 111 cuts off power input / output of some batteries (S107) .

Specifically, in the conventional case, the voltage level changes according to the SOC level of the battery energy storage system 113, and thus, the value of the switching loss changes as the voltage level changes. Here, the SOC level may be the amount of power remaining in the battery energy storage system 113. In this case, each of the battery racks included in the battery energy storage system 113 can not be controlled. Therefore, a switching loss has to be generated manually in accordance with the charging / discharging of the battery energy storage system 113.

However, in an embodiment of the present invention, the plurality of battery racks included in the battery energy storage system 113 each include a switch, and the charge control unit 111 can control the switch. As a result, the charge control unit 111 can control the switches for the respective battery racks to shut off some battery racks. If the charge control unit 111 cuts off some battery racks, the SOC level of the entire battery energy storage system 113 is reduced, leading to a decrease in the voltage level. As a result, the switching loss proportional to the voltage level is also reduced.

If it is determined that the switching loss value calculated by the charge control unit 111 is equal to or less than a predetermined level, the charge control unit 111 continues to charge the battery power storage system 113 It controls input / output ON / OFF.

In yet another embodiment, the charge controller 111 may sense the heat generated by the switching losses between power conversions to determine whether to shut off some battery racks. More specifically, the charge control unit 111 may include a temperature sensor. When the sensed temperature is equal to or higher than a preset value, the charge control unit 111 may control the switching loss by shutting off some battery racks.

In yet another embodiment, the charge controller 111 may determine the number of battery racks to block based on the calculated switching loss value or temperature. For example, according to the currently calculated switching loss value, a switching loss value of 30 may be exceeded. And, a switching loss effect of -10 may be possible whenever a battery rack is shut off. Therefore, according to an example, the charge control unit 111 may block three battery racks to control the switching loss to prevent the temperature of the entire charge control unit 111 from rising.

The embodiments described above are not limited to the configurations and methods described above, but the embodiments may be configured by selectively combining all or a part of the embodiments so that various modifications can be made.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, It will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the present invention.

Claims (8)

A method for controlling a battery power supply system,
Controlling on / off of the input / output converted power;
Determining a switching loss according to the power on / off;
Determining a number of battery racks to be blocked among a plurality of battery racks constituting a battery energy storage system according to the determination result of the switching loss; And
And controlling a switch included in the battery rack by a predetermined number of battery racks among the battery racks to shut off the battery rack. The method according to claim 1,
The step of determining the switching loss
Calculating a switching power loss, and comparing the calculated value with a predetermined value
A method of controlling a battery power supply system. The method according to claim 1,
The step of determining the switching loss
Detecting a temperature rise caused by a switching loss, and comparing the sensed temperature with a predetermined value
A method of controlling a battery power supply system. delete A battery energy storage system including a plurality of battery racks each having a switch and for charging / discharging electric power according to a power supply situation of the system or load; And
A charging controller for controlling on / off of the input / output converted power, determining a switching loss according to the power on / off, and determining the number of battery racks to be disconnected from the plurality of battery racks based on the determination result Including,
Wherein the charge control unit controls the switch included in the battery rack by the number of battery racks determined to be blocked among the plurality of battery racks to shut off the battery rack. 6. The method of claim 5,
The charge control unit calculates a switching loss and compares the calculated value with a predetermined value to determine the switching loss
Battery power supply system. 6. The method of claim 5,
The charge control unit senses a temperature rise caused by a switching loss and compares the sensed temperature with a preset value to determine the switching loss
Battery power supply system. delete

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