KR20210073916A - Active battery filter and distributed power system to which the same is applied - Google Patents

Abstract

An active battery filter according to one embodiment of the present invention includes: a first inductor and a second inductor coupled to each other; a first capacitor, a second capacitor and a third capacitor; and first and second switches, wherein the first inductor is connected between the first node and the second node, the second switch is connected between the second node and the third node, the second inductor is connected between the third node and the fourth node, the first capacitor is connected between the first node and the fifth node, the first switch is connected between the second node and the fifth node, the second capacitor is connected between the third node and the fifth node, and the third capacitor is connected between the fourth node and the fifth node.

Description

ACTIVE BATTERY FILTER AND DISTRIBUTED POWER SYSTEM TO WHICH THE SAME IS APPLIED

The present invention relates to an active battery filter, a distributed power system to which the active battery filter is applied, and a control method thereof.

As the use of distributed power sources with high volatility such as new and renewable energy sources increases, research and application of distributed power systems using batteries to improve power quality are being actively conducted. In a distributed power system, the battery plays a role of balancing the power demand/supply of the distributed power source and the load, so it is characterized by frequent charging and discharging operations.

In the case of a battery applied to a distributed power system such as the above-mentioned renewable energy, the fluctuation of the output power of the renewable energy is severe, so the fluctuation of the battery charge and discharge current is large, which adversely affects the battery performance and lifespan. In addition, the DC link stage of the distributed power system linked to the battery is a point where the power converter that connects various distributed power sources and loads is connected in common, and a low level of harmonic noise is generated for the connection of the distributed power source and stable power supply to the load. is required Therefore, there is a need for an active battery filter capable of reducing battery charge/discharge current ripple and reducing harmonic noise of the DC link stage.

In addition, the control method that can charge and discharge the battery at an appropriate time in various situations is one of the core technologies of the distributed power system, and an active battery operation technology that applies a control method suitable for various situations is also required.

Accordingly, an object of the present invention is to provide an active battery filter for solving the problem of harmonic noise of a DC link stage of a distributed power system associated with battery life and a battery, and a distributed power supply system to which the active battery filter is applied.

Another object of the present invention is to provide a control method capable of performing suitable operations, such as charging mode and discharging mode, depending on the state of the system, distributed power supply, load, and battery.

In order to achieve the above object, an active battery filter according to an embodiment of the present invention includes: a first inductor and a second inductor coupled to each other; a first capacitor, a second capacitor and a third capacitor; and a first switch and a second switch, wherein the first inductor is connected between the first node and the second node, the second switch is connected between the second node and the third node, and the second The inductor is connected between the third node and the fourth node, the first capacitor is connected between the first node and the fifth node, and the first switch is connected between the second node and the fifth node. and the second capacitor is connected between the third node and the fifth node, and the third capacitor is connected between the fourth node and the fifth node.

Distributed power system according to an embodiment of the present invention to achieve the above object, the active battery filter; and a controller for controlling the first switch and the second switch, wherein a battery is connected to the first node and a DC link terminal is connected to the fourth node.

According to an embodiment of the present invention, in the charging mode for charging the battery, the controller turns the first switch OFF, and turns the second switch ON and OFF alternately.

According to an embodiment of the present invention, the controller turns the second switch OFF and turns the first switch ON and OFF alternately in a discharging mode for discharging the battery.

According to an embodiment of the present invention, the controller, based on the state information of at least one of a system connected to the DC link terminal, a distributed power source and a load, and the battery, the active battery filter is a charging mode, a discharging mode and The first switch and the second switch are controlled to operate in one of the sleep modes.

According to an embodiment of the present invention, the state information includes at least one of a voltage and a current of the DC link terminal, and a residual capacity and a temperature of the battery.

According to an embodiment of the present invention, the controller operates the active battery filter in the sleep mode when the state of at least one of the system, the distributed power supply, the load, and the battery is outside a preset safe area. control to do

According to an embodiment of the present invention, when receiving a request from a system operator, the controller controls the active battery filter to operate in the charging mode or the discharging mode according to the system operator's request.

According to an embodiment of the present invention, the controller is, when the distributed power supply or the system is connected to the DC link terminal, and the remaining capacity of the battery _{is less than a predetermined maximum remaining capacity (SOC max} ), the active type The battery filter is controlled to operate in the charging mode.

According to an embodiment of the present invention, when the controller is not connected to the distributed power supply or the system to the DC link terminal, and the remaining capacity of the battery _{is greater than a predetermined minimum remaining capacity (SOC min} ), the active battery The filter is controlled to operate in the discharge mode.

The present invention can reduce battery charge/discharge current ripple by using a bidirectional active battery filter to which a coupled inductor is applied. Accordingly, the battery life may be extended by preventing a sudden change in the battery input current. In addition, it is possible to reduce the harmonics of the system connected to the DC link stage by reducing the DC link stage current ripple of the battery-related distributed power system. Accordingly, the power quality is improved and the lifespan of the electrolytic capacitor used in the input stage of the power converter is extended, so that the overall system reliability can be improved.

In addition, according to the battery charge/discharge control method of the present invention, there are three cases: 1) when the distributed power supply and the battery are connected, 2) when the system and the battery are connected, and 3) when the distributed power, the system and the battery are connected at the same time Both structures can charge and discharge batteries with low current reflow.

1 is a system block diagram of a distributed power system to which an active battery filter is applied according to an embodiment of the present invention.
2 is a circuit diagram of an active battery filter according to an embodiment of the present invention.
3 is a circuit diagram illustrating an operation of an active battery filter in a charging mode.
4 is a circuit diagram illustrating an operation of an active battery filter in a discharging mode.
5 is a block diagram for current ripple compensation control according to an embodiment of the present invention.
6 is a diagram illustrating a current waveform flowing through an inductor before and after application of an active battery filter according to an embodiment of the present invention and an output current waveform output to a battery or a DC link terminal.
7 is a flowchart illustrating a method of controlling a battery filter controller according to a battery charging/discharging mode, a system, a distributed power supply, and a load according to an embodiment of the present invention.
8 is a flowchart of a system request mode that is a sub-flow chart of FIG. 7 .

It should be noted that, in the following description, only parts necessary for understanding the embodiments of the present invention are described, and descriptions of other parts will be omitted so as not to obscure the gist of the present invention.

The terms or words used in the present specification and claims described below should not be construed as being limited to their ordinary or dictionary meanings, and the inventors have appropriate concepts of terms in order to best describe their inventions. It should be interpreted as meaning and concept consistent with the technical idea of the present invention based on the principle that it can be defined in Accordingly, the embodiments described in this specification and the configurations shown in the drawings are only preferred embodiments of the present invention, and do not represent all of the technical spirit of the present invention, so various equivalents that can be substituted for them at the time of the present application It should be understood that there may be variations and variations.

1 is a block diagram of a distributed power supply system to which an active battery filter is applied according to an embodiment of the present invention.

A distributed power system according to an embodiment of the present invention includes a battery 100 , an active battery filter 110 , a bidirectional DC-AC inverter 120 , a bidirectional DC-DC converter 130 , a grid 140 , and a load 150 . , 160 ), a distributed power supply 170 , and a battery filter controller 180 .

1 , a solid line indicates a flow of power in a distributed power supply system, and a dotted line indicates a flow of a control signal.

The active battery filter 110 is located between the battery 100 and the DC link terminal 190 to reduce the harmonic noise of the charge/discharge current input/output to the battery and the current input/output to the DC link terminal.

The DC link stage 190 is connected to the grid 140 , the loads 150 and 160 , and the distributed power supplies 170 through the bidirectional DC-AC inverter 120 and the bidirectional DC-DC converter 130 . For example, the DC link stage 190 is connected to the grid 140 and the load 150 through the bidirectional DC-AC inverter 120 , and the load 160 and distribution through the bidirectional DC-DC converter 130 . It may be connected to the power source 170 .

The battery filter controller 180 may check the voltage (v _grid ) and the current (i _grid ) of the grid 140 to determine whether there is a request from the grid operator.

The battery filter controller 180 checks whether the operating environment of the battery 100 is within a preset safe area by checking the SOC and the temperature of the battery 100 .

The battery filter controller 180 is the voltage (v _grid ) and current (i _{grid ) of the grid 140 , the voltage (v in_DC} ) and current (i _{in _DC} ) of the distributed power supply 170 , and the voltage of the battery 100 . Determine the appropriate operating mode for each situation by checking (v _bat ) and current (i _{bat ).} The operating mode may include a charging mode, a discharging mode, a sleep mode, and a grid demand mode. The battery filter controller 180 controls the active battery filter 110 with _{control signals g 1} and g _{2 according to the determined operation mode.}

2 is a circuit diagram of an active battery filter according to an embodiment of the present invention.

The active battery filter includes first and second switches Q ₁ , Q ₂ , first and second inductors L ₁ , L ₂ , first, second and third capacitors C ₁ , C ₂ , C ₃ ) may be included.

More specifically, the first inductor L _{1 is} connected between the first node N1 and the second node N2 , and the second inductor L _{2 is} connected to the third node N3 and the fourth node N2 . (N4), the first switch (Q ₁ ) is connected between the second node (N2) and the fifth node (N5), the second switch (Q ₂ ) is the second node (N2) and a third node N3 , the first capacitor C ₁ is connected between the first node N1 and the fifth node N5 , and the second capacitor C ₂ is a third It is connected between the node N3 and the fifth node N5 , and the third capacitor C ₃ is connected between the fourth node N4 and the fifth node N5 . The fifth node N5 may be a common node or a ground node.

The first and second inductors L ₁ and L ₂ may be coupled inductors 200 coupled to each other.

The left end 210 of the active battery filter 110 , that is, the first node N1 and the fifth node N5 may be connected to the battery 100 . The right end 220 of the active battery filter 110 , that is, the fourth node N1 and the fifth node N5 is connected to the DC link terminal 190 .

The first and second switches Q ₁ and Q ₂ are controlled by receiving the pulse width modulation control signals g ₁ and g ₂ from the battery filter controller 180 .

When the battery 100 is in the charging mode, the current flows from the right end 220 to the left end 210, and in the discharging mode, the current flows from the left end 210 to the right end 220 to reduce the battery charge/discharge current ripple. can

3 is a circuit diagram illustrating the operation of the active battery filter in the charging mode, and FIG. 4 is a circuit diagram illustrating the operation of the active battery filter in the discharging mode.

For convenience of description, it _{is assumed that the battery voltage (v bat} ) is always lower than the DC link terminal voltage (v _{DC _link ).} The active battery filter 110 operates in a step-down mode in the battery charging mode, and operates in a step-up mode in the battery discharging mode.

3 shows the states of the first and second switches Q ₁ and Q _{2 in the charging mode.}

In the charging mode, the first switch Q ₁ is always OFF, and the second switch Q ₂ may be alternately ON and OFF. _{The control signal g 1} for controlling the ON/OFF of the first switch Q ₁ is always 0, and the _{control signal g 2} for controlling the ON/OFF of _{the second switch Q 2} is generated by the battery filter controller 180. PWM signal is coming in.

When the second switch Q ₂ is in the ON state, energy is stored in the first inductor L ₁ and the first capacitor C _{1 through the second switch Q 2 .}

A second switch in the (Q ₂₎ in the OFF state, the first switch, the second switch (Q ₂₎ through the parasitic diode of the (Q ₁₎ a first inductor (L ₁₎ and a first capacitor (C ₁₎ in the ON state The energy stored in the battery 100 is charged.

4 shows the states of the first and second switches (Q ₁ , Q _{2 ) in the discharge mode.}

In the discharging mode, the second switch Q ₂ is always OFF, and the first switch Q ₁ may be alternately ON and OFF. _{The control signal g 2} for controlling the ON/OFF of the second switch Q ₂ is always 0, and the _{control signal g 1} for controlling the ON/OFF of _{the first switch Q 1} is generated by the battery filter controller 180. PWM signal is coming in.

When the first switch Q ₁ is in an ON state, energy is stored in the first inductor L ₁ and the first capacitor C _{1 through the first switch Q 1 .}

In the first switch (Q ₁ ) OFF state, the _{first switch (Q 1} ) is stored in the first inductor (L ₁ ) and the first capacitor (C ₁ ) in the ON state through the parasitic diode of _{the second switch (Q 2 )} The battery 100 is discharged with energy.

5 is a block diagram for current ripple compensation control according to an embodiment of the present invention.

First, the battery filter controller 180 _{senses the voltage (v bat ) of the battery 100 and the voltage (v DC _link} ) of the DC link terminal 190 through the voltage sensor, and the first inductor (L _{1 ) through the current sensor} ) of the current (i _L1 ), the current (i _bat ) of the battery 100 and the current (i _{DC _link} ) of the DC link terminal 190 are sensed.

In battery charging mode, the output voltage (v _o ) becomes the battery voltage (v _bat ), the reference voltage (v _ref ) becomes the battery reference voltage (v _{ref _bat} ), and the reference average current (i _{ref _ av} ) is the battery average It becomes the current (i _{bat _ av ).}

v _o = v _bat , v _ref = v _{ref _bat} , i _{ref _ av} = i _{bat _ av}

In the battery discharge mode, the output voltage (v _o ) becomes the DC link end voltage (v _{DC _link} ), the reference voltage (v _ref ) becomes the DC link end reference voltage (v _{ref _DC_link} ), and the reference average current (i _{ref _ av} ) becomes the DC link end average current i _{DC _link_ av} .

v _o = v _{DC _ link} , v _ref = v _{ref _DC_ link} , i _{ref _ av} = i _{DC _link_ av}

The summer 300 calculates the error value (e) of the value obtained by applying the gain 360 _{to the selected reference voltage (v ref} ) and the output voltage (v _o ) according to the battery charge/discharge mode, and the equation is as follows.

e = v _ref - kv _o

Thereafter, the proportional controller 310 calculates the reference current i _ref using the error value e calculated above.

)를 계산한다. 리플 보상 기준 전류(

)는 앞서 계산한 기준 전류(i_ref)와 배터리 충·방전 모드에 따라 선택된 기준 평균 전류(i_{ref_av}) 그리고 기준 전류 변화량(Δi_ref)의 합으로 계산되고, 식은 다음과 같다.Thereafter, the summer 320 sets the ripple compensation reference current (

) is calculated. Ripple Compensation Reference Current (

) is calculated as the sum of the previously calculated reference current (i _{ref ), the reference average current (i ref_av} ) selected according to the battery charge/discharge mode, and the reference current change amount (Δi _ref ), and the equation is as follows.

= p(v_ref - kv_o) + Δi_ref + i_{ref _ av}

= p(v _ref - kv _o ) + Δi _ref + i _{ref _ av}

Here, Δi _ref =Δi, and Δi is the _{amount of change in the ripple of the first inductor current i L1} , which is shown in FIG. 6 .

)과 앞서 계산한 리플 보상 기준 전류(

)를 비교해 제1 인덕터 전류의 절대 값(

)이 리플 보상 기준 전류(

)보다 크면 1을, 작으면 0을 Set-Reset 플립플롭(340)의 R로 출력한다.The comparator 330 determines the absolute value of the first inductor current (

) and the previously calculated ripple compensation reference current (

) by comparing the absolute value of the first inductor current (

) is the ripple compensation reference current (

) is greater than 1, and if less than 0, outputted to R of the Set-Reset flip-flop 340 .

To reduce the calculation error, the absolute value of _{the first inductor current i L1 is used.}

The set-reset flip-flop 340 outputs a PWM (pulse width modulation) signal based on the R value inputted through the comparator 330 and the clock value inputted to S (if S is 1, Q outputs 1 and , if R is 1, Q outputs 0, if both are 1, Q outputs 1, and if both are 0, Q outputs the previous Q value).

When the active battery filter 110 operates in the battery discharge mode, the PWM signal output from the Set-Reset flip-flop 340 becomes a control signal g1 and controls the first switch Q ₁ .

When the active battery filter 110 operates in the battery charging mode, the PWM signal output from the Set-Reset flip-flop 340 becomes the control signal g2 and controls the second switch Q ₂ .

6 is a diagram illustrating a current waveform flowing through an inductor before and after application of an active battery filter according to an embodiment of the present invention and an output current waveform output to a battery or a DC link terminal.

_{As shown in (a) of FIG. 6 , the ripple of the first inductor current (i L1} ) decreases after application of the active battery filter 110, and as shown in FIG. 6 (b), the active battery filter 110 Output current after application (i _bat , i _{DC _link} )'s ripple is reduced.

_{Therefore, the inductor current (i L1} ) is reduced through the current ripple compensation control method according to an embodiment of the present invention, and as a result, the output current (i _bat , of the battery 100 and the DC link stage 190) i _{DC _link} ) may be reduced.

Therefore, by reducing the charging and discharging current of the battery 100, it is possible to improve the performance and extend the life of the battery 100, and to reduce the harmonic noise of the DC link stage 190 can improve the power quality of the entire system.

7 is a flowchart illustrating a method of controlling a battery filter controller according to a battery charging/discharging mode, a system, a distributed power supply, and a load according to an embodiment of the present invention.

As shown in FIG. 7 , in the control method according to an embodiment of the present invention, the reference voltage (v _ref ) and the reference average current (i _{ref _ av} ) are can be decided.

First, in step 400 , the battery filter controller 180 checks the current state of the system 140 , the distributed power supply 170 , and the battery 100 .

In the next step 410, the battery filter controller 180 determines the voltage and current of the battery 100, the DC link terminal 190, based on information about the current state of the system 140, the distributed power supply 170, and the battery 100. Check that the operating environment, such as voltage and current of the battery, and the remaining capacity and temperature of the battery, is within the preset safe area.

At this time, if any one of the voltage and current of the battery 100, the voltage and current of the DC link terminal 190, and the remaining capacity and temperature of the battery is out of the safe range, the process goes to step 420, and the battery filter controller 180 controls the active battery filter 110 to operate in a sleep mode.

In the sleep mode, the reference voltage (v _ref ) and the reference average current (i _{ref _ av} ) are zero, and thus the first and second switches Q ₁ and Q ₂ of the active battery filter 110 are all OFF. .

Alternatively, if all values are within the safe area in step 410, the process proceeds to step 430. In step 430, the battery filter controller 180 checks whether there is a request from the system operator.

If there is a request from the system operator in step 430, the flow advances to step 440, which is a sub-flow chart shown in FIG.

If there is no request from the system operator in step 430, the flow advances to step 450. In step 450 , the battery filter controller 180 checks whether power terminals such as the distributed power source 170 and the grid 140 are connected to the DC link terminal 190 .

If the power supply terminal providing energy to the DC link terminal 190 is not connected to the DC link terminal 190 in step 450 , the process proceeds to step 460 and the battery filter controller 180 checks the remaining capacity of the battery 100 .

If the remaining capacity of the battery 100 _{is greater than the preset minimum value (SOC min} ), the process proceeds to step 470 , and the battery filter controller 180 performs the DC link stage 190 in the battery 100 through the active battery filter 110 . ) so that the battery 100 is discharged by transferring energy.

Accordingly, the reference voltage v _ref becomes the DC link end reference voltage v _{ref _DC_link} , and the reference average current i _{ref _ av} becomes the DC link end average current i _{DC _link_ av} .

v _ref = v _{ref _DC_ link} , i _{ref _ av} = -i _{DC _link_ av}

Alternatively, if the remaining battery capacity is _{less than the preset minimum value (SOC min} ) in step 460 , the operation of the battery filter controller 180 ends.

Alternatively, if the power supply terminal is connected to the DC link terminal 190 in step 450 and thus energy is being supplied, the process proceeds to step 480 and the battery filter controller 180 checks the remaining battery capacity.

If the checked remaining battery capacity is _{less than the preset maximum value (SOC max} ), the process proceeds to step 490 , and the battery filter controller 180 performs the battery 100 in the DC link stage 190 through the active battery filter 110 . The energy is transferred to the battery so that the battery 100 is charged.

Accordingly, the reference voltage v _ref becomes the battery reference voltage v _{ref _bat} , and the reference average current i _{ref_av} becomes the battery average current i _{bat _ av} .

v _ref = v _{ref _ bat} , i _{ref _ av} = -I _{bat _ av}

Alternatively, when the remaining battery capacity is _{greater than the preset maximum value (SOC max} ) in step 480 , the operation of the battery filter controller 180 ends.

FIG. 8 is a flowchart of a system request mode that is a sub-flow chart of FIG. 7 . This flowchart is executed at the request of the grid operator in step 430 .

In step 441, the battery filter controller 180 confirms the request from the system operator, and proceeds to step 442.

In step 442, the battery filter controller 180 checks whether the system operator's request is a battery charging mode or a discharging mode.

At this time, if the grid operator requests the battery discharge mode, it goes to step 443, the reference voltage (v _ref ) becomes the DC link terminal reference voltage (v _{ref _DC_link} ), and the reference average current (i _{ref _ av} ) is the DC link terminal It becomes the average current (i _{DC _link_ av ).}

v _ref = v _{ref _DC_ link} , i _{ref _ av} = -i _{DC _link_ av}

Alternatively, if the grid operator requests a battery charging mode, the _{flow advances to step 444 , the reference voltage v ref} becomes the battery reference voltage v _ref _bat , and the reference average current i _{ref _ av} is the average battery current (i _{bat _ av} ).

v _ref = v _{ref _ bat} , i _{ref _ av} = -I _{bat _ av}

The control method of the battery filter controller 180 according to an embodiment of the present invention may be implemented in the form of a program readable through various computer means and recorded in a computer readable recording medium.

On the other hand, the embodiments disclosed in the present specification and drawings are merely presented as specific examples to aid understanding, and are not intended to limit the scope of the present invention. It is obvious to those of ordinary skill in the art to which the present invention pertains that other modifications based on the technical spirit of the present invention can be implemented in addition to the embodiments disclosed herein. In addition, although specific terms have been used in the present specification and drawings, these are only used in a general sense to easily explain the technical contents of the present invention and help the understanding of the present invention, and are not intended to limit the scope of the present invention.

100: battery 110: active battery filter
120: bidirectional DC-AC inverter 130: bidirectional DC-DC converter
140: grid 150, 160: load 170: distributed power
180: battery filter controller
Q ₁ , Q _2: first and second switches L ₁ , L ₂ : first and second inductors
C ₁ , C ₂ , C ₃ : first, second and third capacitors

Claims (10)

a first inductor and a second inductor coupled to each other;
a first capacitor, a second capacitor and a third capacitor; and
a first switch and a second switch;
The first inductor is connected between the first node and the second node,
The second switch is connected between the second node and the third node,
The second inductor is connected between the third node and the fourth node,
The first capacitor is connected between the first node and the fifth node,
The first switch is connected between the second node and the fifth node,
the second capacitor is connected between the third node and the fifth node;
and the third capacitor is connected between the fourth node and the fifth node. The active battery filter according to claim 1; and
Including; a controller for controlling the first switch and the second switch;
A battery is connected to the first node,
A DC link terminal is connected to the fourth node, a distributed power supply system. The method of claim 2, wherein the controller comprises:
In the charging mode to charge the battery,
turn off the first switch,
A distributed power supply system that alternately turns on and off the second switch. The method of claim 2, wherein the controller comprises:
In a discharging mode to discharge the battery,
turn off the second switch,
A distributed power system that alternately turns on and off the first switch. The method of claim 2, wherein the controller comprises:
The first switch and the second switch so that the active battery filter operates in one of a charging mode, a discharging mode and a sleep mode based on status information of at least one of a system connected to the DC link terminal, a distributed power source and a load, and the battery Distributed power system, controlling 2 switches. The distributed power supply system of claim 5 , wherein the state information includes at least one of a voltage and a current of the DC link terminal, and a residual capacity and a temperature of the battery. According to claim 5, wherein the controller,
and controlling the active battery filter to operate in the sleep mode when the state of at least one of the system, the distributed power supply, the load, and the battery is outside a preset safe area. According to claim 5, wherein the controller,
In response to a request from a grid operator, controlling the active battery filter to operate in the charging mode or the discharging mode according to the request of the grid operator. According to claim 5, wherein the controller,
If the distributed power source or the system is connected to the DC link terminal and the remaining capacity of the battery _{is less than a predetermined maximum remaining capacity (SOC max} ), controlling the active battery filter to operate in the charging mode, distributed power system. 10. The method of claim 5 or 9, wherein the controller is
If the distributed power source or the system is not connected to the DC link terminal, and the remaining capacity of the battery _{is greater than a predetermined minimum remaining capacity (SOC min} ), controlling the active battery filter to operate in the discharging mode, distributed power system.

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