KR102246043B1 - Tcs solar generation system and method - Google Patents

Abstract

According to the present invention, provided is a TCS solar power generation system which comprises: a solar cell string configured of a plurality of solar cell modules; a junction box connected to the plurality of solar cell strings; a TCS inverter connected to the plurality of junction boxes to receive current; and a power system receiving power from the plurality of TCS inverters and transmitting the same to a power demand destination, wherein the TCS inverter detects a problem while monitoring the junction box and the solar cell string, and improves power efficiency through MPPT control. In addition, a plurality of sub-inverters are independently built in block units and are driven or stopped in accordance with a power generation capacity by time period to function as a circulation inverter, thereby prolonging the lifespan and reducing maintenance and operating costs.

Description

TCS solar power generation system and power generation method {TCS SOLAR GENERATION SYSTEM AND METHOD}

The present invention relates to a TCS photovoltaic power generation system and a power generation method. More particularly, a TCS capable of supplying a constant voltage for each string by individually MPPT controlling a solar cell string having a low output with a low current value through monitoring the current value of a TCS inverter. It relates to a solar power generation system and power generation method.

In general, solar power generation consists of a combination of solar modules in series and parallel, and the power and open-circuit voltage of about 100 to 400 W per module is 42 to 52 V. Due to the series combination of about 12 to 18 modules, the primary output combined voltage is DC. It is supplied to the inverter at 520~700V.

Voltage and current are generated according to the amount of irradiation of the string, and the current synthesis is output at about 8~12A for each primary string, so in the case of a 100KW solar power plant, the total output current is 160~240A.

Recently, solar power plants collect and operate a number of circuits in series and parallel as above through a junction box, but it is a facility to prevent fire due to the occurrence of circulating current in the junction box due to the difference in power generation by string. “Reverse current prevention diode” for each string is attached for each circuit.

However, the reverse current prevention diode has a problem of causing considerable damage in the solar junction box, "property damage due to burnout due to fire in severe cases along with the increase in size of the enclosure due to the establishment of heat dissipation measures due to overheating and heat dissipation structure"

Accordingly, the type of solar panel without reverse current prevention diode has become a global trend in recent years.

Korean Registered Patent Publication No. 10-1282993 (2013.06.28)

In accordance with the above-described problem, and according to the trend, the present invention divides the operating time of the inverter to the circulating inverter (Team Control System) according to the amount of input power. In case of exceeding the standard value, it is operated with an integrated solution equipped with a TCS control algorithm that controls low power + excess power within the standard value through MPPT constant voltage control of individual strings of the junction box to prevent unbalanced circulating current of the solar power generation system and to prevent the inverter. The purpose is to provide a TCS solar power generation system to maximize the overall limit life of the power conversion system by alternating operation.

The TCS solar power generation system according to the present invention for achieving the above object comprises: a solar cell string composed of a plurality of solar cell modules; A junction box connected to the plurality of solar cell strings; A TCS inverter connected to a plurality of the junction boxes to receive current; And a power system that receives power from the plurality of TCS inverters and transmits it to a power demand site; including, wherein the TCS inverter detects a problem while monitoring the junction box and the solar cell string, and improves power efficiency through MPPT control. It is characterized in that a plurality of sub-inverters are independently built in block units and are driven or stopped according to the generation capacity for each time period to function as a circulating inverter.

Preferably, the TCS photovoltaic power generation method according to the present invention for achieving the above object comprises the steps of: (a) receiving, by the TCS inverter, current values from a plurality of junction boxes; (b) determining, by the TCS inverter, a connection box having a problem with the current value after receiving the current value; (c) determining, by the TCS inverter, a solar cell string having a problem with a current value among a plurality of solar cell strings connected to the junction box determined in step (b); (d) controlling, by the TCS inverter, MPPT control for a solar cell string having a problem due to a low current value; And (e) converting, by the TCS inverter, DC power transmitted from the junction boxes into AC power and transferring it to a power system.

The TCS solar power generation system and method according to the present invention can remove unbalanced circulating current by individually MPPT controlling a solar cell string having a low output at a low current value through monitoring the current value of the TCS inverter and supplying a constant voltage for each string.

In addition, the TCS photovoltaic power generation system and method according to the present invention is composed of a plurality of sub-inverters independently driven according to the capacity of the TCS inverter so that the circulating inverting is performed, thereby extending the lifespan and reducing maintenance costs and operating costs. It can have an effect.

1 is a diagram of a TCS solar power generation system according to the present invention.
2 is a detailed block diagram of a TCS solar power generation system according to the present invention.
3 is a graph of an increase in generation power and an increase in generation time by MPPT control of a TCS solar power generation system according to the present invention.
4 shows the number of sub-inverters that may be provided according to the capacity of the TCS inverter of the TCS solar power generation system according to the present invention.
5 is a view for explaining the principle of circulating a TCS inverter of the TCS solar power generation system according to the present invention.
6 is a diagram for explaining an algorithm for selecting a TCS inverter of the TCS solar power generation system according to the present invention.
7 is a flow chart of a method for controlling MPPT per junction box of a TCS solar power generation system according to the present invention.
8 is a configuration diagram for controlling MPPT for each string unit of the TCS solar power generation system according to the present invention.
9 is a flowchart of a method for controlling MPPT per string of a TCS solar power generation system according to the present invention.
10 is a flowchart of a TCS solar power generation method according to the present invention.
11 is a flowchart of a step of determining a problem access box in the TCS solar power generation method according to the present invention.
12 is a flowchart of a step of determining a problematic solar cell string in the TCS solar power generation method according to the present invention.

The terms or words used in the present specification and claims are not limited to their usual or dictionary meanings and should not be interpreted, and the inventor may appropriately define the concept of terms in order to describe his own invention in the best way. Based on the principle that there is, it should be interpreted as a meaning and concept consistent with the technical idea of the present invention.

Therefore, the embodiments described in the present specification and the configurations shown in the drawings are only the most preferred embodiment of the present invention, and do not represent all the technical spirit of the present invention, so that they can be replaced at the time of application. It should be understood that there may be various equivalents and variations.

Hereinafter, a TCS solar power generation system according to the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram of a TCS solar power generation system according to the present invention.

As shown in Figure 1, the TCS solar power generation system according to the present invention includes a solar array 100, a junction box 200, a TEAM CONTROL SYSTEM (TCS) inverter 300, and a power system 400. .

The solar cell array 100 converts sunlight into electric power and provides it to the junction box 200.

Looking at the structure of the above-described solar cell array 100 in more detail, as shown in FIG. 2, the solar cell array 100 is composed of a plurality of solar cell strings 110, and each of the plurality of solar cell strings 110 ) Is composed of a plurality of solar cell modules 111.

The solar cell module 111 constitutes the solar cell string 110 by connecting a plurality of solar PV modules, solar BIPV modules, or solar tracking modules in series.

Each of the solar cell strings 110 configured in the solar cell array 100 may have different power generation capacity for each string according to an environment.

That is, the solar cell string 110 may generate different capacities depending on the time, direction, weather, or obstacles such as trees when the solar cell string 110 receives sunlight.

The junction box 200 includes a plurality of string optimizers 210 therein and is connected to each of the solar cell strings 110 under the control of the TCS inverter 300 to control MPPT (Maximum Power Point Tracking). .

The string optima 210 of the junction box 200 controls the MPPT of the solar cell string 110 so that each of the plurality of solar cell strings 110 generates the maximum power.

The junction box 200 has a structure that can be attached to a unit in a live state, and outputs a constant voltage boost of the output end with a power generation voltage of 100 to 850V DC of a wide input end and a 650V _{DC constant voltage with a rated capacity of 6kW based on RPS.}

The junction box 200 prevents solar fire by removing an unbalanced circulating current during constant voltage output-parallel operation by controlling the boosting MPPT for each string through the string optimizer 210.

The TCS inverter 300 is composed of five sub-inverters, as described in detail below, and determines whether a current value coming from the junction box 200 is normal.

That is, the TCS inverter 300 calculates the average value, that is, the average current of the currents input from the plurality of junction boxes 200, and the current of any junction box 200 having a current value closest to the average current value. In the case of the junction box 200 maintained for a set time (5 minutes or 10 minutes) within the range of ±α% based on the value, it is determined to be in the normal range.

Conversely, the TCS inverter 300 has a set time (5 minutes or less) within the range of ±α% based on the current value of any junction box 200 having the current value closest to the average current value of the junction box 200. In the case of the access box 200 that cannot be maintained for 10 minutes), it is determined that it is not in the normal range.

If the current input to the junction box 200 is within a set range, it is determined as normal, and if there is a significant difference from the average value of the calculated current outside the set range, it is determined as not normal.

At this time, the TCS inverter 300 calculates an average value of the currents input to the plurality of junction boxes 200 only with the state of the current input to the junction box 200, and the current input to the junction box 200 Determine whether is within the set range.

Here, determining whether the TCS inverter 300 is normal with only current is the solar cell string 110 or the junction box 200 with an average voltage value since the junction boxes 200 are connected in parallel and all voltages are the same. It is pointless to judge whether or not it is normal.

When different currents are input from the solar cell string 110, a so-called circulating current flows inside. In the present invention, a connection box 200 is installed at the output terminal of the solar cell string 110, and a plurality of the connections are at the top. A TCS inverter 300 connected to the box 200 is installed to remove the circulating current.

Different currents are output from the solar cell string 110 in the same way that the same current may flow under the same environmental conditions at first, but as time passes, trees grow and leaves cover the solar cell module 111. It is due to environmental changes.

As another example, dust may accumulate in the solar cell string 110 or a difference in currents generated by the plurality of corresponding solar cell strings 110 may occur due to whitening caused by chemical corrosion in a factory.

The above-described TCS inverter 300 monitors the plurality of junction boxes 200 connected to the input terminal, calculates an average value of the current as already mentioned, determines that the average value is within a predetermined range, determines that it is normal, and determines the predetermined range. If it is outside of, it is judged as abnormal.

For example, when the TCS inverter 300 and 10 junction boxes 200 are connected, the TCS inverter 300 is the current output from the 10 junction boxes 200 from 1 to 10. If the average is calculated and the average is 180A (ampere), and the 7th junction box 200 is 180A, the 7th junction 200 is taken as a reference point, and the reference point can always be changed.

The TCS inverter 300 analyzes whether or not it is normal in time according to the reference point.

That is, when the TCS inverter 300 is in a state in which No. 2 and No. 10 of the junction box 200 are higher or lower than the average current, the setting time is changed (Δt) while continuing 2 It informs that there is a problem with junction boxes 200 of nos. and 10.

In addition, the TCS inverter 300 determines whether the 20 solar cell strings 110 constituting the solar cell array 100 connected to the junction box 200 are abnormal, as described above, for each of the solar cell strings 110. Determine whether there is any abnormality.

That is, the TCS inverter 300 calculates an average current for the plurality of (EX>20) solar cell strings 110 constituting the solar cell array 100, and a current greater than or equal to the average current If the value is continuously output for the set time, it is determined that there is an error.

The TCS inverter 300 determines that the current value in the second junction box 200 is out of the average current and is abnormal, and among the plurality of solar cell strings 110 connected to the second junction box 200, 11 It is determined that the constant voltage control is not performed on the th to fifteenth solar cell strings 110, and thus the stringing optima junction box 200 may be commanded to control MPPT for each string.

In a more specific example, when the solar cell array 100 is composed of 20 solar cell strings 110 and generates a current of 9A (ampere) per solar cell string 110, the connection box 200 transmits a current of 180A to the TCS inverter 300.

Thereafter, the TCS inverter 300 calculates the average current value of the currents transmitted from the 10 junction boxes 200, and when the average current value is 150A and the current in the 7th junction box is 150A, the 7th connection Analyze the rest of the access boxes to see if they are maintained for a set time (5 minutes or 10 minutes) within ±20% of the box 200.

If the current value of the 5th junction box is 100A, the TCS inverter 300 determines that there is a problem in the 5th junction box out of the reference range, and the solar cell array 100 connected to the 5th junction box The 20 solar cell strings 110 to be configured are checked.

In addition, when the current value of the 5th junction box is in the reference range as 130A, but does not meet the duration, the TCS inverter 300 determines that there is a problem in the 5th junction box and is connected to the 5th junction box. The 20 solar cell strings 110 constituting the solar cell array 100 are inspected.

Again, the TCS inverter 300, as described above, through a mechanism for finding a problem junction box among the plurality of junction boxes 200, the solar cell string 110 having an abnormality among the 20 solar cell strings 110. ).

Thereafter, the TCS inverter 300 may determine that the constant voltage control is not performed on the solar cell string 110 having an abnormality and may command the junction box 200 to control MPPT for each string.

As a result, it is possible to increase the power generation of the entire system as shown in FIG. 3A through the MPPT power control for each string, not the MPPT power control for each junction box 200, and reduce the power generation time as shown in FIG. 3B. It can be increased, so that the power generation efficiency is improved.

As shown in FIG. 4, the TCS inverter 300 may have 50kW, 100kW, 500kW, and 1000kW class depending on the power generation capacity, and 50kW has 5 10kW class inverters, and 100kW has 5 20kW class inverters. , 500kW consists of 5 100kW class inverters, and 1000kW class 200kW class inverters independently or distributed.

As described above, the reason why the TCS inverter 300 is composed of a plurality of independent inverters is to block a plurality of inverters according to capacity to function as a circulating inverter.

For example, when the capacity of the TCS inverter 300 is 1000kW consisting of five 200kW sub-inverters as shown in FIG. In the case of %, only the first 200kW sub-inverter is driven. In the morning when the power generation amount is 20-40%, the second and third sub-inverters are driven. Instead, the driving of the first sub-inverter is stopped.

Next, the TCS inverter 300 stops the driving of the two second and third sub-inverters that were being driven when the amount of power generation is 40-60%, and instead, the fourth and fifth sub-inverters that have not been driven once and for a while Start the first sub-inverter that was stopped.

In addition, the TCS inverter 300 stops driving of the first sub-inverter that was being driven when the power generation amount is 60 to 80%, and drives the second and third sub-inverters that were being stopped.

Finally, the TCS inverter 300 drives the first sub-inverter in the stopped state when the amount of power generation is 80 to 100% so that all the sub-inverters are driven.

More specifically, the TCS inverter 300 generates 2 hours at 0<20%, 2 hours at 20-40%, 2 hours at 40-60%, 2 hours at 60-80%, 80-100% When it is assumed that both are operated for 10 hours a day, according to the driving rule as described above, the first to fifth inverters are driven for 6 hours each, and if not in an independent structure, it is 4 hours compared to 10 hours driving. By driving less, the service life is prolonged.

As described above, extending the life of the TCS inverter 300 has an effect of reducing maintenance costs and operating costs.

As shown in FIG. 6, the junction box 200 may have a high voltage junction box 200H and a low voltage junction box 200L separated, and the low voltage junction box 200L does not generate a voltage up to 500V and thus 720V. When the voltage is boosted, the efficiency of the string optima 210 in the junction box is lowered and a cost increase factor occurs, so that the inverter output terminal can be connected to the ON GRID by connecting the inverter for low voltage.

In particular, in the junction box 200, a solar module such as BIPV has a small amount of power generation and, as mentioned above, for efficient control, a high voltage junction box 200H and a low voltage junction box 200L may be separated, the TCS inverter ( As described above, the high voltage junction box 200H and the low voltage junction box 200L may be MPPT controlled in units of junction boxes.

On the other hand, at the front end of the TCS inverter 300, an IGBT non-sequential switching unit 310 having a fast switching speed is formed, and the IGBT non-sequential switching unit 310 is a plurality of the TCS inverters 300 according to the amount of power generation. Selectively switch so that the sub-inverter of is selectively driven.

A method of controlling MPPT for each junction box by the TCS inverter 300 will be described with reference to FIG. 7.

First, the TCS inverter 300 performs a step of recognizing an ID for each string optimizer (S11).

The TCS inverter 300 performs a step of receiving an input voltage for each string optima 210 measured by the junction box 200 (S12).

Thereafter, the TCS inverter 300 performs a step of determining whether the received input voltage for each string optimizer 210 is the voltage of the low voltage junction box 200L or the high voltage junction box 200H (S13).

The TCS inverter 300 performs a step of transmitting the MPPT voltage control signal of the low voltage junction box 200L when the voltage is at the low voltage junction box 200L (S14).

On the other hand, the TCS inverter 300 performs the step of transmitting the MPPT voltage control signal of the high voltage junction box (200H) when the voltage is the high voltage junction box (200H) (S14`).

The low voltage junction box 200L and the high voltage junction box 200H receive an MPPT voltage control signal and perform an MPPT voltage control step for each string optimizer 210 included in each junction box (S15).

The TCS inverter 300 compares currents for each of the plurality of stringing optimizers 210 included in the low voltage junction box 200L and the high voltage junction box 200H, and then the MPPT voltage of the string optima 210 having a small current value. Performs a step of compensating for (S16).

The TCS inverter 300 performs the step of selecting a maximum compensation voltage in comparison to the power increase efficiency compared to the compensated voltage (S17).

The TCS inverter 300 transmits an MPPT voltage control signal for equal voltage control for each string optima 210 (S18).

Through the steps S11 to S18 as described above, the TCS inverter 300 performs a source control step of controlling the unbalanced circulating current due to sunrise, sunset, cloud failure, or foreign substance failure for each string (S19).

Meanwhile, a configuration for controlling the MPPT for each string unit by the TCS inverter 300 is as shown in FIG. 8.

As shown in FIG. 8, the TCS inverter 300 and the junction box 200 are basically generated from the junction box 200 to a voltage of 500V to 1kV without distinction between the high voltage junction box 200H and the low voltage junction box 200L. It is a one-to-one connection, and the TCS inverter 300 controls the MPPT in units of strings in the junction box.

A method of controlling the MPPT in units of strings by the TCS inverter 300 will be described with reference to FIG. 9.

First, the TCS inverter 300 performs a step of recognizing an ID for each string optimizer (S21).

The TCS inverter 300 performs a control signal transmission command step for each string optimizer 210 (S22).

The junction box 200 receives a control signal for each string optima 210 from the TCS inverter 300 and performs an MPPT voltage control step for each string optima 210 included in each junction box (S23).

The junction box 200 transmits the current measurement data of the string optima 210 to the TCS inverter 300 (S24).

The TCS inverter 300 performs a step of compensating the MPPT voltage of the string optima 210 having a small current value after comparing currents for each of the plurality of string optimas 210 included in the junction box 200 (S25). ).

The TCS inverter 300 performs the step of selecting a maximum compensation voltage in comparison to the power increase efficiency compared to the compensated voltage (S26).

The TCS inverter 300 performs a step of transmitting an MPPT voltage control signal for equal voltage control for each string optima 210 (S27).

Through the steps S21 to S27 as described above, the TCS inverter 300 performs a source control step of controlling the unbalanced circulating current due to sunrise, sunset, cloud failure, or foreign substance failure for each string (S29).

The power system 400 receives power from the plurality of TCS inverters 300 and transmits it to a required location.

On the other hand, the TCS solar power generation system according to the present invention further includes an integrated control module 500 to control the TCS inverter 300 to transmit power to the power system 400, and the TCS inverter 300 It may be controlled to find a problem junction box 200 among the plurality of junction boxes 200.

A TCS solar power generation system and power generation method according to the present invention having the above-described configuration will be described with reference to FIG. 10.

First, the TCS inverter 300 is connected to a plurality of junction boxes 200 and performs a step of receiving a current value from the corresponding junction boxes 200 (S100).

The TCS inverter 300 performs a step of determining a junction box 200 having a problem due to a low current value through monitoring while receiving a current value from the junction boxes 200 (S200).

In this case, the determination of the junction box in question is not limited to the current value, but may be a power having a variable current value.

Next, the TCS inverter 300 determines the problematic solar cell string due to a low current value among the plurality of solar cell strings 110 included in the solar array 100 connected to the problematic junction box 200. Performing the step (S300).

In step S300, the TCS inverter 300 performs a step of controlling the MPPT control to be performed on the solar cell string 110 in question due to a low current value (S400).

The TCS inverter 300 converts DC power transmitted from the junction boxes 200 into AC power and transfers it to a three-phase power system (S500).

When the step S200 is described in more detail with reference to FIG. 7, the TCS inverter 300 performs a step of calculating an average current for current values received from a plurality of junction boxes 200 (S210). .

The TCS inverter 300 performs a step of setting a reference current corresponding to ±α% of the current value of the junction box closest to the average current (S220).

The TCS inverter 300 performs a step of determining whether the current value of the junction boxes 200 corresponds to a reference current (S230).

When the current value of the junction boxes 200 corresponds to the reference current in step S230, the TCS inverter 300 again performs a step of determining whether to maintain the reference current for a set time (Δt) (S240).

In the step S240, the TCS inverter 300 performs the step S500 of transferring the output power to the power system when the current value of the junction boxes 200 maintains the reference current for a set time.

Meanwhile, when the current value of the junction boxes 200 does not correspond to the reference current in step S230 and the current value of the junction boxes 200 in step S240 does not maintain the reference current for a set time, the TCS inverter 300 Determines the problem connection and performs step S300 of determining the solar cell string.

The mechanism for discriminating the problematic solar cell string is similar to the mechanism for discriminating the problematic connection box. When described in more detail with reference to FIG. 12, the TCS inverter 300 is the problem connection box 200 A step of calculating the average current of the current values received from the plurality of solar cell strings 110 connected to is performed (S310).

The TCS inverter 300 performs a step of setting the current value of the solar cell string 110 closest to the average current as a reference current corresponding to ±β (S320).

The TCS inverter 300 performs a step of determining whether the current value of the solar cell strings 110 corresponds to the reference current (S330).

When the current value of the solar cell strings 200 corresponds to the reference current in step S330, the TCS inverter 300 again performs a step of determining whether the solar cell strings 110 maintain the reference current for a set time. It performs (S340).

In the step S340, the TCS inverter 300 performs the step S500 of transferring the output power to the power system when the current value of the solar cell strings 110 maintains the reference current for a set time.

Meanwhile, when the current value of the solar cell strings 110 does not correspond to the reference current in step S330, and the current value of the solar cell string 110 does not maintain the reference current for a set time in step S340, the TCS inverter ( 300) determines that the solar cell string 110 in question and performs the step S400 of controlling the MPPT, and then performs the step S500 of transferring power to the power system.

In the above, the technical idea of the present invention has been described together with the accompanying drawings, but this is illustrative of a preferred embodiment of the present invention and does not limit the present invention. In addition, it is obvious that any person of ordinary skill in the technical field to which the present invention pertains can make various modifications and imitations without departing from the scope of the technical idea of the present invention.

100: solar array
110: solar cell string
111: solar cell module
200: access box
210: String Optima
300: TCS inverter
400: power system
500: integrated control module

Claims (12)

A solar cell string composed of a plurality of solar cell modules;
A junction box connected to the plurality of solar cell strings;
A TCS inverter connected to a plurality of the junction boxes to receive current; And a power system that receives power from a plurality of the TCS inverters and transmits it to a power demand site;
The TCS inverter monitors the output terminals connected in parallel of the input junction box, and detects the junction box in question by determining whether the junction box is normal based on a current value and a set time, but the current value is currents input from a plurality of junction boxes. By defining a reference current corresponding to ±α% to the current value of an arbitrary junction box close to the average current for, ordering the inspection of a plurality of solar cell strings connected to the lower end of the junction box where a current outside the corresponding reference current range is input, In addition, even if a current within the reference current range is input from any of the plurality of junction boxes, if it cannot be maintained for a set time (Δt) within the reference current range, check the plurality of solar cell strings connected to the lower end of the junction box. Command,
The TCS inverter detects the solar cell string in question by determining whether the plurality of solar cell strings connected to the lower end of the corresponding junction box is normal based on a current value and a set time, and the current value is a plurality of solar cell strings. A solar cell in which a current outside the range of the reference current is input by calculating the average current for the currents input from the battery string and defining a reference current corresponding to ±β% to the current value of an arbitrary solar cell string close to the average current. MPPT constant voltage control is commanded for the string, and MPPT constant voltage control is performed for the solar cell string, even if the current within the reference current range is input from the solar cell string, if it cannot be maintained for a set time (Δt) within the reference current range. By order,
TCS photovoltaic power generation system, characterized in that to suppress the generation of unbalanced circulating current between the solar cell strings connected in parallel in the junction box.
delete delete delete delete The method of claim 1,
The TCS inverter is
A TCS solar power generation system, characterized in that a plurality of sub-inverters are independently built in block units and are driven or stopped according to the generation capacity for each time period to function as a circulating inverter. delete delete delete delete delete delete

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