KR101587488B1 - High efficiency battery charge/discharge system and method in grid-tied system - Google Patents

Abstract

The present invention relates to a high efficiency battery charging and discharging system and method for implementing a grid-connected system that is not constrained by battery specifications.
A grid-connected system having a distributed power source and an energy storage system (ESS) according to the present invention includes: an isolation transformer capable of changing tap according to a turn ratio calculated based on voltage and current of an ESS; And a first bidirectional DC / DC converter located at a first end of the isolation transformer to adjust a first voltage of the isolation transformer; And a second bidirectional DC / DC converter located at a second end of the isolation transformer opposite the first end to match the second voltage of the isolation transformer with the voltage of the ESS.

Description

TECHNICAL FIELD [0001] The present invention relates to a high efficiency battery charge / discharge system and method in a grid-

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solar light system, and more particularly, to a system and method for charging and discharging a battery in a grid-connected system.

There are two main types of photovoltaic systems that can be installed in Korea. It is a grid-tied system and an off-grid system.

Figure 1 is a schematic diagram of a grid-connected system.

The grid interconnection type 100 converts the DC electricity produced by the solar panel 110 into AC electricity through the inverter 120. [ And the converted electricity is consumed by the household 150 and simultaneously transmitted to the utility grid 140 to obtain a profit.

In the grid-connected system of FIG. 1, only the solar panel 110, that is, the PV array, is included as a power generating part.

The photovoltaic (PV) array of the solar panel 110 is a PV array formed by collecting cells and collecting PV modules. PV arrays are generally composed of four or more modules in a single array. Nowadays, however, the concept of thin-film solar cells is getting out of line with the concept of small cells.

The DC-AC inverter 120 includes a component of a balance of system equipment (BOS), and is a device for converting direct current electricity generated from solar light into AC that can be used in the home or business.

BOS refers to a collection of equipment or components that enable a system to operate reliably. These include batteries, control units, electrical wiring, over-charge protection, and grounding utilities.

Metering 130 is a device that indicates how much energy is produced or used.

Figure 2 is a schematic diagram of a stand-alone system.

The system diagram 200 of the stand-alone system is shown in FIG. The stand-alone system has the greatest difference in that the power produced by the solar panel 210 is not supplied to the grid (140 in FIG. 1) as compared to the grid-connected grid of FIG.

The electricity generated by the solar panel 210 is charged by the charging controller 220 and the inverter 240 converts the DC electricity generated in the battery 250 into AC electricity and supplies it to the house 260 . In addition, when electricity can not be produced by only the panel 210 because the weather is bad, the generator 230 can be additionally installed to produce and supply electricity.

Figure 3 is a schematic diagram of a grid-connected system with a distributed power supply and ESS;

The grid-connected system 300 having the distributed power source 320 and the ESS 310 is compared with the grid-connected system shown in FIG. 1, and in addition to the PV array 320 serving as the distributed power source, And an ESS (Energy Storage System) 310 are additionally included.

The load 360 in FIG. 3 represents the power consumption in the home or home in FIG. 1, and is connected to the grid 370.

DC converter 380. The bidirectional DC / DC converter 330 and the solar converter 340 at the left end are separated from each other at the left end and the right end through the DC_link 380.

The bidirectional DC / DC converter 330 and the solar converter 340 are for step-up or step-down of the produced power voltage at the ESS 310 and the distributed power supply 320.

The solar converter 340 is also referred to as a DC / DC converter for controlling the distributed power supply, but is merely referred to as a solar converter in order to distinguish it from the DC / DC 330 for the ESS.

The bidirectional inverter 350 converts DC electricity into AC electricity that can be supplied to the load and the system in the same manner as the inverter 120 in FIG.

The circuit break 390 is for the separation between the grid power supply and the inverter 350.

The ESS 310 in the grid-connected system 300 with the distributed power source 320 and the ESS 310 shown in Figure 3 refers to the battery and is connected to the distributed power source 320 and / Can be charged.

In addition, when the power generation amount generated from the distributed power source 320 is not satisfied, the discharge operation of supplying power to the system 370 or the load 360 through the ESS 310 is performed.

The system of FIG. 3 is designed and manufactured in consideration of the capacity, voltage, and current specifications of the ESS 310, that is, the battery. In the system of FIG. 3, it is difficult to use a specification other than the battery of the specifications considered in the system design, and thus the degree of freedom of the grid-connected system including the distributed power supply 320 and the ESS 310 is very limited. That is, since battery specifications are different according to the battery manufacturer, there is a problem that it is necessary to use only the system that meets the specifications of each battery, that is, ESS.

The present invention relates to a system and method for high efficiency battery charging and discharging for realizing a grid-connected system which is not constrained by battery specifications.

According to an aspect of a high efficiency battery charge / discharge system in a grid-connected system according to the present invention,

In a grid-connected system with distributed power and an ESS (Energy Storage System)

An insulation transformer capable of changing the tap according to the turn ratio calculated based on the voltage and current of the ESS;

A first bidirectional DC / DC converter located at a first end of the isolation transformer to adjust a first voltage of the isolation transformer;

And a second bidirectional DC / DC converter located at a second end of the insulation transformer opposite to the first end to match a second voltage of the insulation transformer with a voltage of the ESS.

Preferably,

And a buck-boost DC / DC converter for boosting or reducing the voltage input to or from the grid or the distributed power supply.

Preferably,

And a capacitor located between the buck-boost DC / DC converter and the first bidirectional DC / DC converter.

According to another aspect of the high efficiency battery charge / discharge system in the grid-connected system according to the present invention,

In a grid-connected system with distributed power and an ESS (Energy Storage System)

A DC link for storing power input from the grid or the distributed power source or output to the grid;

A buck-boost DC / DC converter for boosting or reducing the voltage supplied from the DC link or provided to the DC link;

A DC / DC converter for converting the boosted or depressurized voltage of the buck-boost DC / DC converter to a voltage of the ESS, the isolation transformer varying according to the turn ratio calculated based on the voltage and current of the ESS, Converter.

Preferably,

The DC / DC converter

The insulation transformer capable of changing tapping according to a turn ratio calculated based on a voltage and a current of the ESS;

A first bidirectional DC / DC converter located at a first end of the isolation transformer to adjust a first voltage of the isolation transformer;

And a second bidirectional DC / DC converter located at a second end of the insulation transformer opposite to the first end to match a second voltage of the insulation transformer with a voltage of the ESS.

Preferably,

And a capacitor interposed between the buck-boost DC / DC converter and the DC / DC converter.

According to an aspect of the high efficiency battery charge / discharge method in the grid-connected system according to the present invention,

In a grid-connected system with distributed power and an ESS (Energy Storage System)

Sensing a voltage of the ESS;

Calculating a current capacity of the ESS;

Calculating a turn ratio of the insulation transformer based on the voltage of the ESS and the current capacity;

Switching taps of the insulation transformer to have the calculated turn ratio; And

And discharging the ESS by charging the ESS or powering the system from the system or the distributed power source.

Preferably,

And the tab of the insulation transformer is determined based on a maximum voltage of the ESS and a minimum voltage of the ESS.

Preferably,

And adjusting a voltage at a first end of the isolation transformer and a second end opposite the first end through at least one bi-directional DC / DC converter.

According to the system and method for high efficiency battery charging and discharging in the grid-connected system according to the present invention, it is possible to implement a grid-connected system without being constrained by the specifications of the battery.

Figure 1 is a schematic diagram of a grid-connected system.
Figure 2 is a schematic diagram of a stand-alone system.
Figure 3 is a schematic diagram of a grid-connected system with a distributed power supply and ESS;
FIG. 4 is a diagram showing a schematic configuration of a high-efficiency battery charge / discharge system in a grid-connected system having a distributed power source and an ESS according to the present invention.
FIG. 5 is a flowchart illustrating a method for charging and discharging a high efficiency battery in a grid-connected system having a distributed power source and an ESS according to the present invention.

In order to fully understand the present invention, operational advantages of the present invention, and objects achieved by the practice of the present invention, reference should be made to the accompanying drawings and the accompanying drawings which illustrate preferred embodiments of the present invention.

Hereinafter, the present invention will be described in detail with reference to the preferred embodiments of the present invention with reference to the accompanying drawings. Like reference symbols in the drawings denote like elements.

The high-efficiency battery charging and discharging system of the present invention uses a transformer for insulation and voltage lowering or voltage boosting in a battery charge-discharge circuit in a grid-connected system having a distributed power source (or PV array) and an ESS It is possible to automatically change the turn ratio of the optimum transformer according to the capacity of the battery, so that the system can be freely configured and used without changing the entire system according to the specification of the battery voltage and current.

According to the high efficiency battery charge / discharge system of the present invention, since the capacity of the grid-connected system is determined, when the battery suitable for the capacity of the system is connected, the capacity of the battery can be easily connected to the capacity of the system Can be used.

In the present invention, a grid-connected system having a distributed power source and an ESS is constructed by applying an isolation transformer capable of tap charging to solve the problems of the conventional grid-connected system. By using an isolation transformer capable of tap charge, the battery bi-directional charge converter can operate at the operating point that achieves the optimum efficiency, thereby improving the efficiency of the system. There are features.

FIG. 4 is a diagram showing a schematic configuration of a high-efficiency battery charge / discharge system in a grid-connected system having a distributed power source and an ESS according to the present invention.

The grid-connected system with a distributed power supply and an Energy Storage System (ESS) includes an isolation transformer 431 having a plurality of taps, a first bidirectional DC / DC converter 432 and a second bidirectional DC / DC converter 433, .

The insulation transformer 431 is variable in accordance with the turn ratio calculated based on the voltage and current of the ESS, that is, the battery 440, and is capable of tap switching.

The first bidirectional DC / DC converter 432 is located at the first end of the isolation transformer 431 to regulate the first voltage of the isolation transformer.

The first voltage may be a voltage input from the DC_link 410 to the insulation transformer 431 when the battery or ESS is charged. On the other hand, the first voltage refers to a voltage output from the insulation transformer 431 to the DC_link 410 when the battery or ESS is discharged.

The second bidirectional DC / DC converter 433 is located at the second end of the isolation transformer opposite the first end of the isolation transformer 431 to match the second voltage of the isolation transformer with the voltage of the ESS.

The second voltage refers to the output voltage of the insulation transformer 431 during the charging process, similar to the first voltage, but refers to the voltage input from the battery 440 to the insulation transformer 431 during the discharge process.

In the present invention, the input point and the output point may be different depending on whether the first voltage and the second voltage refer to a voltage at the same point or a charging process or a discharging process.

The high efficiency charge / discharge system in the grid-connected system with the distributed power source and the ESS according to the present invention can increase or decrease the voltage output from the system (370 in FIG. 3) or the distributed power source (320 in FIG. 3) And a buck-boost DC / DC converter 420 for the DC-DC converter.

In addition, it may further include a capacitor 450 located between the buck-boost DC / DC converter and the first bidirectional DC / DC converter.

In general, the system of the present invention includes a DC link 410 for storing power input to or from the grid or the distributed power source, a buck-boost DC for boosting or reducing the voltage supplied from the DC link or provided to the DC link, Boost DC / DC converter 420 including a buck-boost DC / DC converter 420 and an isolation transformer capable of changing tap according to a turn ratio calculated based on the voltage and current of the ESS. And a DC / DC converter 430 for matching the reduced voltage with the voltage of the ESS.

The DC / DC converter 430 includes the isolation transformer 431, the first bidirectional DC / DC converter 432, and the second bidirectional DC / DC converter 433 as mentioned above.

FIG. 5 is a flowchart illustrating a method for charging and discharging a high efficiency battery in a grid-connected system having a distributed power source and an ESS according to the present invention.

In the grid-connected system having the distributed power source and the ESS (Energy Storage System) according to the present invention, the high efficiency battery charge / discharge method starts with S510 of sensing the voltage of the battery or ESS.

The current capacity of the ESS is calculated (S520).

The turn ratio of the insulation transformer is calculated based on the voltage and current capacity of the ESS (S530).

 A tap of the insulation transformer is determined to have the calculated turn ratio (S540).

The automatic tap switching of the transformer is performed (S550).

The system starts charging the ESS from the grid or the distributed power source or discharging the ESS by supplying power to the grid (S560).

In the step of determining the tap of the insulation transformer in S540, the tab of the insulation transformer is characterized based on the maximum voltage (S541) of the ESS and the minimum voltage (S542) of the ESS.

The high efficiency battery charging and discharging method according to the present invention may further include adjusting a voltage at a first end and a second end of the insulation transformer opposite to the first end through at least one bidirectional DC / DC converter.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit and scope of the invention. It is.

410: DC_link
420: Buck-Boost DC / DC Converter
450: Capacitor
430: DC / DC converter
440: ESS or battery

Claims (9)

In a high efficiency battery charge / discharge system in a grid-connected system with a distributed power source and an ESS (Energy Storage System)
An insulation transformer capable of changing the tap according to the turn ratio calculated based on the voltage and current of the ESS;
A first bidirectional DC / DC converter located at a first end of the isolation transformer to adjust a voltage input from the distributed power supply to a first voltage of the isolation transformer; And
And a second bidirectional DC / DC converter located at a second end of the isolation transformer opposite the first end to match a second voltage of the isolation transformer with a voltage of the ESS. High efficiency battery charge / discharge system. The method according to claim 1,
Further comprising a buck-boost DC / DC converter for boosting or reducing the voltage input to or from the grid or the distributed power supply, Charge / discharge system. The method of claim 2,
Further comprising a capacitor located between said buck-boost DC / DC converter and said first bi-directional DC / DC converter. In a high efficiency battery charge / discharge system in a grid-connected system with a distributed power source and an ESS (Energy Storage System)
A DC link for storing power input from the grid or the distributed power source or output to the grid;
A buck-boost DC / DC converter for boosting or reducing the voltage supplied from the DC link or provided to the DC link; And
A DC / DC converter for converting the boosted or depressurized voltage of the buck-boost DC / DC converter to a voltage of the ESS, the isolation transformer varying according to the turn ratio calculated based on the voltage and current of the ESS, A system for high efficiency battery charging and discharging in a grid-connected system. The method of claim 4,
The DC / DC converter
The insulation transformer capable of changing tapping according to a turn ratio calculated based on a voltage and a current of the ESS;
A first bidirectional DC / DC converter located at a first end of the isolation transformer to adjust a first voltage of the isolation transformer; And
And a second bidirectional DC / DC converter located at a second end of the isolation transformer opposite the first end to match a second voltage of the isolation transformer with a voltage of the ESS. High efficiency battery charge / discharge system. The method of claim 4,
Further comprising a capacitor interposed between the buck-boost DC / DC converter and the DC / DC converter. In a high efficiency battery charging and discharging method in a grid-connected system having a distributed power source and an ESS (Energy Storage System)
Sensing a voltage of the ESS;
Calculating a current capacity of the ESS;
Calculating a turn ratio of the insulation transformer based on the voltage of the ESS and the current capacity;
Switching taps of the insulation transformer to have the calculated turn ratio; And
And charging the ESS or discharging the ESS by supplying power to the system from the system or the distributed power source. The method of claim 7,
Wherein the taps of the isolation transformer are determined based on a maximum voltage of the ESS and a minimum voltage of the ESS. The method of claim 7,
And adjusting a voltage at a first end of the isolation transformer and at a second end opposite the first end through at least one bi-directional DC / DC converter. Way.

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