KR102180879B1 - Photovoltaic power generation system with power converter connected by energy storage device and photovoltaic panel - Google Patents

Abstract

Provided is a photovoltaic system which can increase conversion efficiency of energy of the photovoltaic system. The photovoltaic system comprises: a plurality of solar power conversion devices connected to a plurality of photovoltaic panels located in different sunlight environments and converting power generated from the photovoltaic panels to output the converted power to direct current (DC) wiring; a plurality of battery power conversion devices each connected to a plurality of energy storage devices having different states and controlling power conversion between the DC wiring and the energy storage device; an alternating current (AC) power conversion device controlling power conversion between the DC wiring and AC wiring; and a central control device controlling the plurality of solar power conversion devices, the plurality of battery power conversion devices, and the AC power conversion device.

Description

A photovoltaic power generation system in which power conversion devices are connected for each energy storage device and photovoltaic power generation panel {PHOTOVOLTAIC POWER GENERATION SYSTEM WITH POWER CONVERTER CONNECTED BY ENERGY STORAGE DEVICE AND PHOTOVOLTAIC PANEL}

This embodiment relates to a photovoltaic system.

The photovoltaic power generation system includes a photovoltaic panel that generates power using sunlight and a photovoltaic power conversion device that controls the power generation of the photovoltaic panel, and controls the energy storage device and the energy storage device, if necessary. It may further include a battery power conversion device to perform.

9 is a block diagram of a general photovoltaic system.

Referring to FIG. 9, the photovoltaic power generation system 1 may convert power produced by the photovoltaic panel 10 and transmit it to the system or store it in the energy storage device 20.

The photovoltaic power generation system 1 includes a circuit breaker 40 (ACB: Air Circuit Breaker) connected in series with the first transformer 52 connected to the grid, a photovoltaic power conversion device (30, PV-INV: Photovoltaic Inverter), and It may include a solar panel 10. The power produced by the solar panel 10 is converted to AC (Alternating Current) power by the solar power conversion device 30 and then transferred to the first transformer 52 through the circuit breaker 40. In addition, the first transformer 52 may transmit the power produced by the solar panel 10 to the system or energy storage device 20 through the connection node Nc.

The photovoltaic power generation system (1) includes a circuit breaker (40) connected in series with a second transformer (54) connected to the grid, a battery power conversion device (34, PCS: Power Conditioning System), and an energy storage device (20). can do. The generated power transmitted from the solar panel 10 through the connection node Nc may be stored in the energy storage device 20. Then, the battery power conversion device 34 may convert the power stored in the energy storage device 20 and transmit it back to the system.

The photovoltaic power generation system 1 of this structure has several disadvantages.

First, the energy conversion efficiency is low. In order for the power produced by the solar panel 10 to be transferred to the energy storage device 20, it is necessary to pass through two transformers 52 and 54 as well as the photovoltaic power conversion device 30 and the battery power conversion device 34. Therefore, the loss in the transmission process appears large. In addition, since the photovoltaic power converter 30 and the battery power converter 34 are AC/DC power converters, their conversion loss is relatively large compared to the DC/DC power converter. Due to these losses, the energy conversion efficiency of the conventional photovoltaic system 1 was not high.

Second, the conventional photovoltaic power generation system 1 has a problem of disturbing the system and increasing the cost when generating power and charging power do not match. When the supply of power from the system is not desired or the unit of power to the system is not high, it is preferable that all the power produced by the solar panel 10 is stored in the energy storage device 20. By the way, in this case, the conventional photovoltaic power generation system 1 also includes the photovoltaic power conversion device 30 and the battery power conversion device so that all the power produced by the photovoltaic panel 10 is stored in the energy storage device 20. 34), but since the two devices are separated by two transformers 52 and 54, even a temporary mismatch may cause power to flow into or out of the grid. There is a problem in that the system is disturbed or costs are increased due to such unintended power outflow or inflow.

Third, the conventional photovoltaic power generation system 1 collectively controls a solar panel and an energy storage device, and it is difficult to optimally control each device. When the photovoltaic power generation system 1 uses a plurality of photovoltaic panels, each photovoltaic panel may be placed in a different environment. For example, one solar panel may be in a location where the amount of sunlight or intensity of sunlight is high, and the other solar panel may be in a location where the amount of sunlight or intensity of sunlight is relatively low due to installation restrictions. If the sunlight environment is different, the control point for optimal control may also be different, and the conventional solar power generation system 1 could not optimally control the solar panels in different sunlight environments by collectively controlling a plurality of solar panels. If the energy storage device is in different states, the control should be different. However, the conventional photovoltaic system 1 could not optimally control the energy storage devices in different states by collectively controlling a plurality of energy storage devices.

Against this background, it is an object of this embodiment, in one aspect, to provide a technology capable of increasing the energy conversion efficiency of a photovoltaic system. In another aspect, an object of the present embodiment is to provide a technique for stabilizing a system connected to a photovoltaic power generation system and maximizing cost in system connection. In another aspect, an object of the present embodiment is to provide a technology capable of optimally controlling a solar power generation system including a plurality of solar panels or a plurality of energy storage devices.

In order to achieve the above object, an embodiment provides a photovoltaic power generation system in which a power conversion device is connected for each energy storage device and a photovoltaic power panel, or a photovoltaic power generation system in which the power conversion device is distributed and arranged .

In another embodiment, a plurality of photovoltaic power conversion devices connected to a plurality of photovoltaic panels located in different sunlight environments, and converting power generated from the photovoltaic panels and outputting the power through DC wiring; A plurality of battery power conversion devices each connected to a plurality of energy storage devices having different states and controlling power conversion between the DC wiring and the energy storage device; An AC power conversion device for controlling power conversion between the DC line and the AC line; And a central control device for controlling the plurality of photovoltaic power conversion devices, the plurality of battery power conversion devices, and the AC power conversion device.

The solar power conversion device controls the output voltage or output current of the solar panel to a maximum output point according to MPPT (Maximum Power Point Tracking) control, but can flow to the plurality of energy storage devices or the AC wiring. When the power decreases, the output voltage or output current of the solar panel may be controlled to move away from the maximum output point.

The central control device divides the remaining power by subtracting the power transmitted through the AC wiring from the sum of the power produced by the plurality of solar panels to the plurality of energy storage devices through the plurality of battery power conversion devices. I can.

The central control unit is a ratio of the power to be transmitted to each energy storage device according to a function including at least two or more factors among SoC (State-of-Charge), SoH (State-of-Health), capacity, and temperature. May be determined, and power may be distributed to the plurality of energy storage devices according to the ratio.

Among the plurality of energy storage devices, the first energy storage device and the second energy storage device have different temperature states and are connected to the first battery power conversion device and the second energy storage device. The second battery power conversion device may be controlled by different charging/discharging currents.

The ratio is allocated and stored to each battery power conversion device, and each battery power conversion device may control the amount of charge and discharge using the stored value for the ratio.

As described above, according to the present embodiment, it is possible to increase the energy conversion efficiency of the solar power generation system. And, according to the present embodiment, it is possible to stabilize the system connected to the solar power generation system and maximize the cost in the system connection. In addition, according to the present embodiment, it is possible to optimally control a solar power generation system including a plurality of solar panels or a plurality of energy storage devices.

1 is a configuration diagram of a photovoltaic power generation system according to an embodiment.
FIG. 2 is a diagram illustrating an example of a path through which power generated from a solar panel flows in an embodiment.
3 is a diagram showing an example of an MPPT curve.
4 is an exemplary diagram of a control flow when a power limitation is formed in an embodiment.
5 is a flowchart of a method of controlling charge/discharge power according to a ratio in an embodiment.
6 is a diagram showing a connection relationship between each power conversion device and a DC wiring in an embodiment.
7 is a diagram illustrating a flow of power distributed to each energy storage device in an embodiment.
8 is a diagram illustrating an example of a droop curve that can be applied to an embodiment.
9 is a block diagram of a general photovoltaic system.

Hereinafter, some embodiments of the present invention will be described in detail through exemplary drawings. In adding reference numerals to elements of each drawing, it should be noted that the same elements are assigned the same numerals as possible even if they are indicated on different drawings. In addition, in describing the present invention, if it is determined that a detailed description of a related known configuration or function may obscure the subject matter of the present invention, a detailed description thereof will be omitted.

In addition, in describing the constituent elements of the present invention, terms such as first, second, A, B, (a), (b) may be used. These terms are only used to distinguish the component from other components, and the nature, order, or order of the component is not limited by the term. When a component is described as being "connected", "coupled" or "connected" to another component, the component may be directly connected or connected to that other component, but another component between each component It should be understood that elements may be “connected”, “coupled” or “connected”.

1 is a configuration diagram of a photovoltaic power generation system according to an embodiment.

1, a photovoltaic power generation system 100 includes a plurality of solar panels 10a to 10c, a plurality of photovoltaic power converters 110a to 110c, PVC: Photovoltaic Converter, and a plurality of energy storage devices 20a. ~ 20c), a plurality of battery power conversion devices (120a ~ 120c, BTC: Battery Converter), AC power conversion device (150, INV: Inverter), may include a central control device 130 and a transformer 160, etc. .

The plurality of solar panels 10a to 10c may be located in different sunlight environments. For example, the first site SITE_A where the first solar panel 10a is located may have a large amount of sunlight and a high intensity of sunlight. In addition, the second site SITE_B where the second solar panel 10b is located may have high humidity and low temperature due to surrounding wetlands. In addition, since the third site SITE_C where the third solar panel 10c is located is in an inclined position, the amount of sunlight per unit area for the solar panel may be small and the sunlight intensity may be low.

This sunlight environment can also change over time. For example, in the morning time, the sunlight intensity of the first solar panel 10a located at the first site (SITE_A) is higher than the second solar panel 10b located at the second site (SITE_B), but in the afternoon time The sunlight intensity of the solar panel 10b may be higher than that of the first solar panel 10a.

The plurality of solar power conversion devices 110a to 110c are connected to the plurality of solar panels 10a to 10c, respectively, and control the plurality of solar panels 10a to 10c with different control points for different sunlight environments. I can.

A plurality of solar power conversion devices (110a ~ 110c) can perform MPPT (Maximum Power Point Tracking) control, each solar panel (10a ~ 10c) when the sunlight environment of each solar panel (10a ~ 10c) changes. The MPPT curve of can also change. The plurality of photovoltaic power converters 110a to 110c may control the output voltage or output current of each solar panel 10a to 10c as a maximum output point that outputs the maximum power in the MPPT curve. When the plurality of photovoltaic power converters 110a to 110c are controlled while following the maximum output point, the control point may be automatically changed according to the sunlight environment. And, as a result, the plurality of solar panels 10a to 10c disposed in different sunlight environments can be controlled by different control points. This is possible because each of the solar panels 10a to 10c is not collectively controlled, but is controlled by separate solar power conversion devices 110a to 110c in a separate group according to the sunlight environment.

The plurality of photovoltaic power converters 110a to 110c may convert power produced by each of the photovoltaic panels 10a to 10c and output them to DC wirings DCLa to DCLb. The plurality of photovoltaic power converters 110a to 110c may be DC/DC power converters. The plurality of photovoltaic power converters 110a to 110c may convert DC power produced by each of the photovoltaic panels 10a to 10c and output them as DC wirings DCLa to DCLb.

The plurality of photovoltaic power converters 110a to 110c are connected to the DC wiring (DCLa to DCLb) through the first connection panel 140a, and the plurality of photovoltaic power converters 110a to 110c and the first connection panel (140a) may be disposed in an environment in which humidity and/or temperature are controlled within a single building structure. Alternatively, the plurality of photovoltaic power conversion devices 110a to 110c may be disposed adjacent to each of the photovoltaic panels 10a to 10c. In this case, the plurality of photovoltaic power converters 110a to 110c and the first connection panel 140a may be disposed to be spaced apart from each other and electrically connected by the first DC wiring DCLa. When a plurality of photovoltaic power conversion devices (110a to 110c) are disposed in close proximity to each of the photovoltaic panels (10a to 10c), between the photovoltaic power conversion devices (110a to 110c) and the solar panel (10a to 10c) Because the voltage drop of is small, the accuracy of control can be increased.

The plurality of energy storage devices 20a to 20c may have different states. Various indicators for managing the state can be used. For example, State-of-Charge (SoC), State-of-Health (SoH), capacity, temperature, etc. can determine the state of the energy storage devices 20a to 20c. It can be an indicator.

Each of the energy storage devices 20a to 20c may have a different state. As an example, the first energy storage device 20a may have an SoC of 0.8, and the second energy storage device 20b is 1 It may have an SoC of, and the third energy storage device 20c may have an SoC of 0.3. As another example, the capacity of the first energy storage device 20a may be 10Ah, the capacity of the second energy storage device 20b may be 5Ah, and the capacity of the third energy storage device 20c may be 1Ah. The capacity may have the same value initially but may vary over time, or may have different values initially-for example, when recycling used batteries, each energy storage device has a different capacity. I can -.

The plurality of battery power conversion devices 120a to 120c are connected to the plurality of energy storage devices 20a to 20c, respectively, and control the plurality of energy storage devices 20a to 20c with different charging/discharging power for different states. I can.

As an example, the plurality of battery power conversion devices 120a to 120c may control a charging current of an energy storage device having a low SoC to be greater than that of an energy storage device having a high SoC. As another example, the plurality of battery power conversion devices 120a to 120c may control the amount of change in charge/discharge current of the energy storage device having high SoH higher than that of the energy storage device having low SoH. As another example, the plurality of battery power conversion devices 120a to 120c allow an energy storage device with a large capacity to voltage control the DC wiring (DCLa to DClb), and an energy storage device with a small capacity to control the DC wiring (DCLa to DClb). ) To control the current. As another example, the plurality of battery power conversion devices 120a to 120c may control the amount of change in charge/discharge current of the energy storage device having a high temperature to be lower than that of the energy storage device having a low temperature.

A plurality of battery power conversion devices (120a to 120c) are disposed between each of the energy storage devices (20a to 20c) and DC cables (DCLa to DCLb) by using DC power formed on the DC cables (DCLa to DCLb), respectively. The energy storage devices 20a to 20c of may be charged or the DC power stored in each of the energy storage devices 20a to 20c may be discharged through the DC wirings DCLa to DCLb. The plurality of battery power conversion devices 120a to 120c may be DC/DC power conversion devices.

The plurality of battery power conversion devices 120a to 120c may be connected to the DC wirings DCLa to DCLb through the second connection panel 140b. The plurality of battery power conversion devices 120a to 120c and the second connection panel 140b may be disposed to be spaced apart from each other and electrically connected by the second DC wiring DCLb. When a plurality of battery power conversion devices (120a ~ 120c) are disposed close to each of the energy storage devices (20a ~ 20c), the voltage between the battery power conversion devices (120a ~ 120c) and the energy storage devices (20a ~ 20c) Because the drop is small, the accuracy of control can be increased.

The AC power conversion device 150 may convert DC power formed on the DC wirings DCLa to DCLb into AC power and output it through the AC wiring. The AC wiring may be connected to the transformer 160 by wiring that is connected to the system.

The central control device 130 may control a plurality of photovoltaic power conversion devices 110a to 110c, a plurality of battery power conversion devices 120a to 120c, and an AC power conversion device 150.

The central control device 130 may control the amount of power generation of the plurality of photovoltaic power conversion devices 110a to 110c. The central control device 130 may transmit a control value to each of the photovoltaic power conversion devices 110a to 110c to control each of the photovoltaic power conversion devices 110a to 110c. As an example, the central control device 130 controls each of the photovoltaic power converters 110a to 110c by transmitting the absolute value of the output current of each photovoltaic power converter 110a to 110c as a control value. can do. As another example, the central control device 130 transmits an increase or decrease of the amount of power generation of each of the solar power conversion devices 110a to 110c as a control value to control each of the photovoltaic power conversion devices 110a to 110c. I can.

The central control device 130 may control the amount of charge and discharge power of the plurality of battery power conversion devices 120a to 120c. The central control device 130 may transmit a control value to each of the battery power conversion devices 120a to 120c to control each of the battery power conversion devices 120a to 120c. As an example, the central control device 130 transmits the absolute value of the charge/discharge current of each battery power conversion device 120a to 120c as a control value to control each battery power conversion device 120a to 120c. I can. As another example, the central control unit 130 transmits an increase/decrease value for the charge/discharge current of each battery power conversion device 120a to 120c as a control value to control each battery power conversion device 120a to 120c. I can.

The central control device 130 may control the amount of grid transmission of the AC power conversion device 150. The central control device 130 may control the AC power conversion device 150 by transmitting a control value to the AC power conversion device 150. As an example, the central control device 130 may control the AC power conversion device 150 by transmitting an absolute value of the grid transmission amount of the AC power conversion device 150 as a control value. As another example, the central control apparatus 130 may control the AC power conversion apparatus 150 by transmitting an increase/decrease value of the grid transmission amount of the AC power conversion apparatus 150 as a control value.

The central control device 130 may monitor the state of the solar panels 10a to 10c and the energy storage devices 20a to 20c and obtain various information thereon. In addition, the central control unit 130 can control a plurality of solar power conversion devices (110a ~ 110c), a plurality of battery power conversion devices (120a ~ 120c) and the AC power conversion device 150 based on these various information. I can. In addition, the photovoltaic power conversion device (110a ~ 110c) can monitor the state of each solar panel (10a ~ 10c) and obtain various information about it, and the battery power conversion device (120a ~ 120c) is energy storage It is possible to monitor the state of the devices 20a to 20c and obtain various information about it.

Although not shown in the drawing, the central control device 130 may further acquire additional information through communication with an external device. For example, the central control unit 130 can obtain information on the amount of power that can be supplied to the system through communication with the system managing the system, and information on incentives and electricity prices that can be received when supplying to the system Can be obtained. In addition, the central control device 130 may obtain information on the sunlight environment, such as the amount of sunlight that may be applied to each of the solar panels 10a to 10c through communication with the weather server. The central control device 130 may control various devices in the photovoltaic power generation system 100 using such various information.

Hereinafter, examples applicable to each of the components in the photovoltaic power generation system according to an embodiment will be described in more detail.

FIG. 2 is a diagram illustrating an example of a path through which power generated from a solar panel flows in an embodiment.

Referring to FIG. 2, generated power (PPV) in the solar panel 10 may be transferred to a DC wiring (DCL) by the solar power conversion device 110. And, the generated power (PPV) delivered to the DC wiring (DCL) may be supplied as the charging power (PBT) of the energy storage device 20 along the first path (Fa), and along the second path (Fb). It can be the grid power (PPS) supplied to the grid.

In the central control unit 130, in the solar power generation system, the generated power (PPV) may be substantially equal to the sum of the charging power (PBT) and the system power (PPS). When the power of one side is limited, the central control device 130 may control the power flow of the other side so that the limit is reflected.

As an example, the central control device 130 may obtain information from a device that manages a system and check the limit of the system power (PPS) through this information. Alternatively, the central control device 130 may determine the unit price of the system power (PPS) from the system managing device and establish a certain limit on the system power (PPS) through internal gain calculation. According to this limitation, the power that can flow to the AC power conversion device 150 may be reduced. In this case, the central control device 130 may increase the charging power PBT so that the balance of power is maintained.

As another example, the central control device 130 acquires information from a device that manages the energy storage device 20-for example, the energy storage device 20 itself or the battery power conversion device 120 You can check the limit of charging power (PBT) through. Alternatively, the central control device 130 may obtain various information on the state of the energy storage device 20 from the device managing the energy storage device 20 and establish a certain limit on the charging power (PBT) according to this information. have. According to this limitation, power that can flow to the energy storage device 20 may be reduced. In this case, the central control device 130 may increase the system power PPS so that the balance of power is maintained.

It may be a problem if both the charging power (PBT) and the grid power (PPS) must be reduced according to the above limitation, in this case, the central control device 130 reduces the generated power (PPV) of the solar panel 10 The photovoltaic power conversion device 110 can be controlled so as to be.

3 is a diagram showing an example of an MPPT curve.

Referring to FIG. 3, there may be a difference in generated power output from the solar panel for each control point in the MPPT curve. The photovoltaic power conversion device according to an embodiment may control an output voltage or an output current of a photovoltaic panel to a maximum output point (A(Ia, Va)) according to MPPT control.

When performing such MPPT control and attempting to reduce the power generation of the solar panel due to various reasons as described with reference to FIG. 2, the solar power conversion device is the output voltage or output current of the solar panel. Can be controlled to move away from the maximum output point (A(Ia, Va)). For example, the photovoltaic power converter may move the control point from the first control point A(Ia, Va) to the second control point B(Ib, Vb) in order to reduce the generated power of the solar panel. .

4 is an exemplary diagram of a control flow when a power limitation is formed in an embodiment.

Referring to FIG. 4, the central control device may perform MPPT control so that each solar panel produces the maximum power generation (S401).

In addition, the central control device may distribute the remaining power by subtracting the grid power transmitted through the AC wiring from the sum of the generated power produced by the plurality of solar panels to the plurality of energy storage devices through the plurality of battery power conversion devices. .

At this time, the central control unit determines the ratio of the power to be transmitted to each energy storage device according to a function including at least two or more factors among SoC, SoH, capacity, and temperature, and to the plurality of energy storage devices according to the determined ratio. Power can be distributed.

On the other hand, when distributing power to a plurality of energy storage devices, the central control device compares the total or average SoC of the energy storage devices with the first reference value (S403), and if the SoC does not exceed the first reference value (S403 NO), it is possible to distribute power to each energy storage device by transmitting the control value distributed to a plurality of battery power conversion devices. In addition, the central control device may perform the MPPT control step (S401).

However, if the SoC exceeds the first standard value (YES in S403), the central control unit limits the power supplied to the energy storage device to the first standard value, and subtracts the power supplied to the energy storage device from the total amount of generated power. One can calculate the remaining power.

The power calculated here is determined as the system power, and the central control device may compare the system power and the second reference value (S405). If the grid power does not exceed the second reference value (NO in S405), the AC power conversion device may be controlled according to the determined grid power to transmit the grid power to the grid.

However, if the determined system power exceeds the second reference value (YES in S405), the central control unit limits the system power to the second reference value, and operates the solar power conversion device so that the generated power is reduced by the amount of system power reduced according to the limit. Low power control can be performed (S407).

Meanwhile, the central control device may determine a charge/discharge current flowing into and out of each energy storage device according to the state of each energy storage device. At this time, the central control device may determine the control value as a relative value. For example, the central control device may transmit a rate of charge/discharge power of each energy storage device as a control value. The central control unit can allocate a 20% ratio to the first energy storage device with SoC 0.8, and allocate 50% to the second energy storage device with SoC 0.6, and the third energy with SoC 0.4. You can allocate a 30% percentage to storage.

In addition, the central control device may transmit a control value for the allocated ratio to each battery power conversion device. Each battery power converter stores the allocated ratio in memory, and when the total amount of charge/discharge power of a plurality of energy storage devices is received from the central control device, the charge/discharge power amount of each energy storage device is multiplied by the corresponding charge and discharge power amount. Can be calculated.

5 is a flowchart of a method of controlling charge/discharge power according to a ratio in an embodiment.

Referring to FIG. 5, the central control device allocates a ratio to each battery power conversion device, and each battery power conversion device may receive a control value for the ratio from the central control device and store it in a memory (S500).

In addition, each battery power conversion device may receive charging/discharging power to be handled by the plurality of energy storage devices from the central control device (S502). In this case, the charging/discharging power may be calculated by subtracting the grid power transmitted through the AC wiring from the total power generated by the plurality of solar panels.

Each battery power conversion device may control the amount of charging and discharging to each energy storage device by using a value obtained by multiplying the stored rate value by the received charging/discharging power (S504).

On the other hand, each battery power conversion device checks whether the ratio is re-received from the central control unit (S506), and if the ratio is not re-received (S506), it repeats from the step (S502) of receiving the charging/discharging power again. Can be done.

However, when each battery power conversion device re-receives the ratio (YES in S506), each battery power conversion device can update the ratio stored in the memory (S508).

Since recalculating the ratio and transmitting/receiving may take a relatively long time, when each battery power converter uses the ratio value stored in the memory as described above, the control can proceed relatively quickly.

6 is a diagram showing a connection relationship between each power conversion device and a DC wiring in an embodiment.

Referring to FIG. 6, a plurality of photovoltaic power converters 110a to 110c, a plurality of battery power converters 120a to 120d, and an AC power converter 150 may be connected to one DC wiring (DCL). .

In this structure, when a plurality of power conversion devices perform voltage control on the DC wiring (DCL), a control abnormality or an operation abnormality may occur in each power conversion device according to a mismatch of the control voltage. In order to solve this problem, in the photovoltaic power generation system according to an embodiment, only one battery power conversion device among a plurality of battery power conversion devices 120a to 120d performs voltage control on the DC line (DCL), and The battery power conversion device may perform current control on the DC wiring (DCL).

In addition, the plurality of photovoltaic power conversion devices 110a to 110c and the AC power conversion device 150 may not perform voltage control on the DC wiring (DCL) or can perform current control on the DC wiring (DCL). .

In this case, it may be a problem which one of the plurality of battery power conversion devices 120a to 120d performs voltage control on the DC wiring DCL.

7 is a diagram illustrating a flow of power distributed to each energy storage device in an embodiment.

Referring to FIG. 7, a first charging power PBTa is supplied from a DC wiring (DCL) to a first energy storage device 20a, and a second charging power is supplied from the DC wiring (DCL) to a second energy storage device 20b. Power PBTb may be supplied, and third charging power PBTc may be supplied from the DC wiring DCL to the third energy storage device 20c.

The central control device may determine that the battery power conversion device corresponding to the energy storage device having the largest capacity among the plurality of energy storage devices 20a to 20c performs voltage control on the DC wiring DCL. In order to perform voltage control, it is necessary to cover all of the amount of power according to voltage fluctuations in the DC wiring (DCL). For example, if the amount of power generated by photovoltaic power generation suddenly increases, the voltage of the DC wiring (DCL) may rise. However, the battery power converter that controls the voltage of the DC wiring (DCL) suddenly increases the amount of generated power. It should be able to absorb all of them. In consideration of this, the central control device may determine that the battery power conversion device corresponding to the energy storage device having the largest capacity performs voltage control on the DC wiring (DCL).

From a similar point of view, the central control unit is a battery power conversion unit corresponding to the energy storage unit with a state-of-charge (SoC) closest to a preset value among the plurality of energy storage units 20a to 20c. It can be decided to perform voltage control on

The remaining battery power conversion devices may perform current control on the DC wiring (DCL). For example, when the first battery power conversion device 120a performs voltage control, the amount of variable power in the DC wiring DCL may be covered by the first energy storage device 20a. In addition, the second battery power conversion device 120b and the third battery power conversion device 120c may control the second energy storage device 20b and the third energy storage device 20c with a constant charge/discharge current.

Meanwhile, the plurality of battery power conversion devices may perform droop control on the DC wiring.

8 is a diagram illustrating an example of a droop curve that can be applied to an embodiment.

Referring to FIG. 8, a plurality of battery power conversion devices may perform droop control according to a voltage of a DC wiring.

The plurality of battery power conversion devices may perform droop control according to the first droop curve 810. The plurality of battery power converters can increase the charging current when the voltage of the DC wiring increases, thereby lowering the voltage of the DC wiring, and when the voltage of the DC wiring decreases, increase the discharge current to increase the voltage of the DC wiring.

The central control unit can change the flow of power in the photovoltaic system by adjusting the droop curve.

As an example, the central control device may adjust the charge/discharge control dynamics of the plurality of battery power conversion devices by adjusting the slope SL of the droop curve. When the central control unit changes the droop curve from the first droop curve 810 to the third droop curve 830, the slope SL of the droop curve changes gently (to reduce the absolute value), and the current fluctuation compared to the voltage fluctuation amount And the charge/discharge control dynamics of each battery power conversion device can be accelerated.

As another example, the central control unit may control the amount of transmission of the AC power converter to the AC wiring by controlling the Y-intercept of the droop curve. When the central control unit changes the droop curve from the first droop curve 810 to the second droop curve 820, the Y-intercept decreases and the amount of power supplied to the energy storage device for the same DC wiring voltage increases. May increase the amount of transmission Conversely, if the droop curve is changed so that the Y-intercept becomes larger, the amount of power supplied to the energy storage device for the same DC wiring voltage decreases, thereby reducing the amount of transmission to the AC wiring.

The control methods of FIGS. 6 to 7 described above may be mixed with each other. For example, the two control methods can be temporally mixed, and the central control unit operates a plurality of battery power converters in voltage control and current control as described with reference to Figs. 6 to 7 in the first time period. It can be done, and droop control can be performed as described with reference to FIG. 8 in the second time period. Alternatively, the central control unit may cause a device that performs voltage control to perform droop control, a device that performs current control to perform droop control, or both.

As described above, according to the present embodiment, it is possible to increase the energy conversion efficiency of the solar power generation system. And, according to this embodiment, it is possible to stabilize the system connected to the photovoltaic power generation system and maximize the cost in the system connection. In addition, according to the present embodiment, it is possible to optimally control a solar power generation system including a plurality of solar panels or a plurality of energy storage devices.

Terms such as "include", "consist of", or "have" described above, unless otherwise stated, mean that the corresponding component may be included, and thus other components are not excluded. It should be interpreted as being able to further include other components. All terms, including technical or scientific terms, unless otherwise defined, have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. Terms generally used, such as terms defined in the dictionary, should be interpreted as being consistent with the meaning in the context of the related technology, and are not interpreted as ideal or excessively formal meanings unless explicitly defined in the present invention.

The above description is merely illustrative of the technical idea of the present invention, and those of ordinary skill in the art to which the present invention pertains will be able to make various modifications and variations without departing from the essential characteristics of the present invention. Accordingly, the embodiments disclosed in the present invention are not intended to limit the technical idea of the present invention, but to explain the technical idea, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be interpreted by the following claims, and all technical ideas within the scope equivalent thereto should be interpreted as being included in the scope of the present invention.

Claims (6)

A plurality of photovoltaic power converters connected to a plurality of photovoltaic panels located in different sunlight environments, and converting power generated by the photovoltaic panel and outputting the converted power through DC wiring;
A plurality of battery power conversion devices respectively connected to a plurality of energy storage devices having different states and controlling power conversion between the DC wiring and the energy storage device;
An AC power conversion device for controlling power conversion between the DC line and the AC line; And
A central control device for controlling the plurality of solar power conversion devices, the plurality of battery power conversion devices, and the AC power conversion device
Including,
Each solar panel has different MPPT (Maximum Power Point Tracking) characteristics according to different sunlight environments, and the plurality of solar power converters control each solar panel to a different control point,
With respect to the first battery power conversion device and the second battery power conversion device among the plurality of battery power conversion devices, a state-of-health (SoH) of the first energy storage device controlled by the first battery power conversion device is If it is higher than the SoH of the second energy storage device controlled by the second battery power conversion device, the amount of change in charge/discharge current of the first battery power conversion device is controlled to be higher than the amount of change in charge and discharge current of the second battery power conversion device, or , When the temperature of the first energy storage device controlled by the first battery power conversion device is higher than the temperature of the second energy storage device controlled by the second battery power conversion device, the first battery power conversion device The charging/discharging current fluctuation amount of is controlled to be lower than the charging/discharging current fluctuation amount of the second battery power conversion device,
The AC power conversion device converts DC power formed on the DC wiring into AC power and outputs it to the AC wiring, and the AC wiring is connected to the system through a transformer,
The central control device,
Controls each battery power conversion device by transmitting a control value to each battery power conversion device, and the remaining power obtained by subtracting the power transmitted through the AC wiring from the sum of the power produced by the plurality of solar panels is the Distributed to the plurality of energy storage devices through a plurality of battery power conversion devices,
The central control device,
Check the grid power limit from the system managing device or form a certain grid power limit from the unit price of grid power identified from the system managing device, and calculate the power transmitted to the AC wiring according to the grid power limit. To control the AC power conversion device,
A solar power generation system in which one battery power conversion device having the largest capacity among the plurality of battery power conversion devices performs voltage control on the DC wiring, and the remaining battery power conversion devices perform current control on the DC wiring. The method of claim 1,
The solar power conversion device,
According to MPPT (Maximum Power Point Tracking) control, the output voltage or output current of the solar panel is controlled to the maximum output point, but if the power that can flow to the plurality of energy storage devices or the AC wiring decreases, the solar panel A photovoltaic power generation system that controls the output voltage or output current of the photovoltaic panel away from the maximum output point. The method of claim 1,
The central control device,
Determine the ratio of the power to be transmitted to each energy storage device according to a function that includes at least two or more factors among SoC (State-of-Charge), SoH (State-of-Health), capacity, and temperature, and the ratio In accordance with the solar power generation system for distributing power to the plurality of energy storage devices. The method of claim 1,
Among the plurality of energy storage devices, the third energy storage device and the fourth energy storage device have different temperature states and are connected to the third battery power conversion device and the fourth energy storage device. The fourth battery power conversion device is a solar power generation system controlled by different charging and discharging currents. delete delete

Images