TWI514714B - Distributed solar power system and controlling method thereof - Google Patents

Description

Decentralized solar power generation system and control method thereof

The present invention relates to a solar power generation system, and more particularly to a distributed solar power generation system and a control method for the same.

In general, solar power systems can be classified into at least centralized and decentralized. In a centralized solar power system, all solar modules are coupled to a DC converter and controlled by the same controller. Under such restrictions, the characteristics of all solar modules need to be as uniform as possible, but when the sunlight received by a solar module is obscured, even if only 10% of the shielding situation will cause the entire solar power system. The effect is much lower. On the other hand, in a distributed solar power system, each solar module is coupled to a DC converter, and each DC converter is controlled by a respective controller, so even if a shadowing phenomenon occurs, the solar energy Modules can be used to achieve greater power generation efficiency without being affected. However, since a plurality of controllers are provided, the control method of the distributed solar power generation system is more complicated, and how to propose an effective control method is an issue of concern to those skilled in the art.

In order to solve the above problems, an embodiment of the present invention provides a distributed solar power generation system including a plurality of solar modules, a plurality of DC converters, a plurality of conversion control circuits, and a central controller. Each DC converter has a boost mode and a buck mode. The input of each DC converter is coupled to one of the solar modules, and the outputs of the DC converter are connected in series to form a solar module and a DC converter. Photovoltaic string. The conversion control circuit separately couples and controls the DC converter, and obtains multiple power information of the solar module. The central controller receives power information from the conversion control circuit and performs a boot process and a shutdown process of the distributed solar power system. In the booting process, the central controller controls the switching control circuit to sequentially enter the pulse width modulation mode, the voltage regulation mode, and the maximum power point tracking mode. After the booting process is executed, when the output voltage of the first DC converter is lower than the first threshold, the central controller controls the first switching control circuit coupled to the first DC converter to switch from the maximum power point tracking mode. To the voltage regulation mode, the input voltage of the first DC converter is fixed. When the first switching control circuit is in the voltage stabilizing mode, and the difference between the input voltage and the output voltage of the first DC converter is less than a threshold threshold, the central controller controls the first switching control circuit to switch from the voltage stabilizing mode to The pulse width modulation mode causes the first DC converter to enter the buck mode.

In an embodiment, after the first conversion control circuit is switched from the voltage stabilization mode to the pulse width modulation mode, the central controller sets the check cycle. The central controller switches the first switching control circuit from the pulse width modulation mode to the voltage stabilization mode and determines whether the difference between the input voltage and the output voltage of the first DC converter is greater than or equal to each other. The gap threshold. If the difference between the input voltage and the output voltage of the first DC converter is greater than or equal to the threshold threshold, the central controller switches the first conversion control circuit after the output voltage of the first DC converter is greater than or equal to the first threshold To the maximum power point tracking mode.

In an embodiment, the above-described distributed solar power generation system further includes an inverter coupled to the photovoltaic string for converting the direct current power provided by the photovoltaic string into alternating current. In the booting process, the central controller determines whether the open circuit voltage of each solar module is greater than the open circuit voltage threshold according to the power information to calculate the normal number of modules, and the inverter is in the confirm mode. If the number of normal modules is greater than a preset number of power-on, the central controller controls the switching control circuit to enter the pulse width modulation mode, and controls the inverter to switch to the standby mode. In addition, the central controller determines whether the potential difference of the DC voltage is greater than the potential difference threshold. If the potential difference of the DC voltage is greater than the potential difference threshold, the central controller controls the switching control circuit to adjust the potential difference of the DC voltage to the preset power generation potential difference after waiting for a predetermined time.

In an embodiment, if the potential difference of the DC voltage is not adjusted to the preset power generation potential difference, the central controller performs a shutdown procedure. If the potential difference of the DC voltage is adjusted to the preset power generation potential difference, the central controller controls the inverter to enter the operation mode, and controls the switching control circuit to enter the voltage stabilization mode. In the regulated mode, the central controller determines whether the conversion control circuit can regulate the output voltage of each solar module according to at least one command. If the second conversion control circuit cannot according to the output voltage of the solar module corresponding to the command voltage regulation, the central controller performs a shutdown procedure or sets the second conversion control circuit to the bypass operation mode. In the bypass mode of operation, the second turn The output of the DC converter corresponding to the control circuit is turned on. If it is determined that the conversion control circuit determines that the output voltage of the solar module can be stabilized according to the command, the central controller controls the conversion control circuit to enter the maximum power point tracking mode. In the maximum power point tracking mode, if the operating power of the inverter is greater than the minimum operating power threshold, the central controller controls the inverter to remain in the operating mode. If the operating power of the inverter is not greater than the minimum operating power threshold, the central controller performs a shutdown procedure. In an embodiment, the central controller executes when the operating power of the inverter is lower than the minimum operating power threshold, when the output voltage of a DC converter is greater than the output voltage threshold, or when the operating voltage of the inverter is abnormal. Shutdown procedure. In the shutdown procedure, the central controller controls the switching control circuit to enter the regulated mode, and then controls the switching control circuit to enter the pulse width modulation mode to adjust the output voltage of the DC converter to zero. In the shutdown procedure, the central controller switches the inverter from the operating mode to the acknowledgment mode after the inverter releases the power.

An embodiment of the present invention provides a control method of the above-described distributed solar power generation system. The control method comprises: receiving power information from the conversion control circuit, executing a startup procedure of the distributed solar power generation system to control the conversion control circuit to sequentially enter the pulse width modulation mode, the voltage regulation mode and the maximum power point tracking mode; After the program, when the output voltage of the first DC converter in the DC converter is lower than the first threshold, the first conversion control circuit coupled to the first DC converter is controlled to switch from the maximum power point tracking mode to a voltage stabilizing mode for fixing an input voltage of the first DC converter; and when the first switching control circuit is in a voltage stabilizing mode and a difference between an input voltage and an output voltage of the first DC converter is less than a gap When the threshold is thresholded, the first switching control circuit is controlled to switch from the regulated mode to the pulse width modulation mode to cause the first DC converter to enter the buck mode.

The above described features and advantages of the invention will be apparent from the following description.

100‧‧‧Distributed solar power system

110, 120‧‧‧ photovoltaic strings

111~113, 141~143‧‧‧ solar modules

121~123, 151~153‧‧‧ DC Converter

131~133, 161~163‧‧‧ conversion control circuit

170‧‧‧Central controller

180‧‧‧Inverter

190‧‧‧mains grid

201‧‧‧Voltage sensor

202‧‧‧ Current Sensor

Q1~Q4‧‧‧Optoelectronics

C1, C2‧‧‧ capacitor

L‧‧‧Inductance

D‧‧‧ diode

210‧‧‧ Voltage Controller

220‧‧‧ drive

230‧‧‧ modulator

V _pv ‧‧‧Voltage information

I _pv ‧‧‧current information

V _Ref ‧‧‧ directive

301~319, 401~408, 801~811, 901~905‧‧‧ steps

510, 610‧‧‧ areas

1 is a schematic diagram showing a distributed solar power generation system according to an embodiment; FIG. 2 is a schematic diagram showing control of a DC converter according to an embodiment; FIG. 3A and FIG. 3B are schematic diagrams showing a flow of a booting process according to an embodiment. 4 is a schematic flow chart showing a special operation flow according to an embodiment; FIG. 5 is a voltage curve diagram of a DC converter without a special operation flow; FIG. 6 is a diagram showing a special operation flow according to an embodiment; FIG. 7 is a schematic diagram showing a check cycle according to an embodiment; FIG. 8 is a schematic flow chart showing a shutdown procedure according to an embodiment; and FIG. 9 is a diagram illustrating distributed solar power generation according to an embodiment. Schematic diagram of the control method of the system.

1 is a schematic diagram showing a decentralized solar power generation system in accordance with an embodiment. Referring to FIG. 1, the distributed solar power generation system 100 includes solar modules 111-113 for converting light energy into electrical energy (outputted in the form of direct current). The solar modules 111-113 are respectively coupled to the input ends of the DC converters 121-123. Each of the DC converters 121-123 has a boost mode and a buck mode for boosting or reducing the voltage output by the solar modules 111-113. In some applications, the voltages output by the solar modules 111-113 are relatively low, so the outputs of the DC converters 121-123 are connected in series with each other, so that the solar modules 111-113 and the DC converters 121-123 form a photovoltaic string. 110, used to provide a large voltage DC. However, the invention does not limit the number of solar modules in the photovoltaic string 110.

The DC converters 121 to 123 are coupled and controlled by the switching control circuits 131 to 133, respectively. The conversion control circuits 131 to 133 can control the conversion ratios (the ratio of the output voltage to the input voltage) of the DC converters 121 to 123, whereby the output power of the solar modules 111 to 113 can also be controlled. In detail, under the same sunshine conditions, the output power of the solar module will be related to the voltage and current output by the solar module. When the output power of a solar module is the largest, the current voltage and current can also be referred to as the Maximum Power Point. In order to allow each solar module to operate at the maximum power point as much as possible, the conversion control circuits 131-133 obtain the power information on the solar modules 111-113, and transmit the power information, for example, by wireless or wired transmission. To the central controller 170. Such power information is, for example, current, voltage, power, etc., and the present invention is not limited thereto. The central controller 170 executes a maximum power point tracking algorithm and issues commands to the conversion control circuits 131-133. The conversion control circuits 131-133 will further control the DC converters 121-123 according to these commands, so that the solar modules 111-113 can output the maximum power as much as possible.

Similarly, the solar modules 141-143 and the DC converters 151-153 also form the photovoltaic string 120, and the DC converters 151-153 are controlled by the switching control circuits 161-163, respectively. Since the operation of the photovoltaic string 120 and the devices in the photovoltaic string 110 are similar, the details are not repeated below. Here, the photovoltaic string 120 is connected in parallel with the photovoltaic string 110 to provide a large current. However, FIG. 1 is merely an example, and the present invention does not limit the number of photovoltaic strings in the distributed solar power generation system 100.

In the embodiment of FIG. 1, the photovoltaic strings 110, 120 are coupled to the inverter 180. The inverter 180 is configured to convert the direct current supplied from the photovoltaic strings 110, 120 into alternating current and provide the alternating current to a utility grid 190. However, in another embodiment, the photovoltaic strings 110, 120 may also be coupled to one or more batteries, or other electronic components, and the present invention does not limit the use of the power output by the photovoltaic strings 110, 120.

The central controller 170 is a boot process for executing the distributed solar power system 100, a shutdown process, and related control after powering on. In this embodiment, the central controller 170 communicates with the conversion control circuits 131-133, 161-163 in a communication protocol of a Universal Asynchronous Receiver/Transmitter (UART), but in other embodiments The central controller 170 can also use other wireless/ Wired communication protocol, the invention is not limited thereto. The operation of the central controller 170 will be described in detail below.

2 is a schematic diagram of control of a DC converter according to an embodiment. Referring to FIG. 2 , the solar module 111 , the DC converter 121 and the conversion control circuit 131 are taken as an example, and the arrangement of other solar modules is similar to that of FIG. 2 , and details are not described below. A current sensor 202 is connected in series between the solar module 111 and the DC converter 121, and the voltage sensor 201 is connected in parallel. The DC converter 121 includes transistors Q1 to Q4, capacitors C1 and C2, an inductor L, and a diode D. In an embodiment, each of the transistors Q1 to Q4 may be further connected with a Schottky Diode to reduce the switching surge of the transistor. The DC converter 121 can operate as a buck converter and a boost converter through the on and off of the transistors Q1 to Q4. However, those skilled in the art should understand the operation of the buck converter and the boost converter, and will not be described herein.

The conversion control circuit 131 obtains the current information I _pv from the current sensor 202 , obtains the voltage information V _pv from the voltage sensor 201 , and wirelessly transmits the current information I _pv and the voltage information V _pv to the central controller 170 . . After accepting the information, the central controller 170 calculates an instruction V _Ref and transmits the command to the conversion control circuit 131.

The conversion control circuit 131 includes a voltage regulator controller 210, a driver 220, and a modulator 230. In this embodiment, the conversion control circuit 131 has four operation modes, a bypass operation mode, a pulse width modulation mode, a voltage stabilization mode, and a maximum power point tracking mode.

In the bypass mode of operation, the switching control circuit 131 controls the output of the DC converter 121 to become conductive, and equivalently, the solar module 111 is removed from the associated photovoltaic string. When an abnormality occurs in the solar module 111, the switching control circuit 131 may enter a bypass operation mode to prevent the solar module 111 from affecting other solar modules on the same photovoltaic string.

In PWM (Pulse Width Modulation, PWM) mode, the modulator 230 may be determined according to an instruction transistors V _Ref Q1 ~ Q4 duty ratio (duty cycle) to output the PWM signal to the driver 220, The driver 220 thereby controls the conduction and the turn-off of the transistors Q1 to Q4.

In the regulated mode, the conversion control circuit 131 causes the solar module 111 to output a fixed voltage. For example, the voltage regulator controller 210 is a Proportional-Integral (PI) controller for subtracting the command V _Ref from the voltage information V _pv to obtain an error value. After the error value is subjected to the operation of proportional and integral, a control signal can be obtained. However, those skilled in the art should understand the operation of the PI controller and will not repeat them here. The above control signal is used to indicate the duty ratio of the transistors Q1~Q4, and the driver 220 controls the conduction and the cutoff of the transistors Q1~Q4 according to the control signal. In an embodiment, the use of a voltage stabilizing mode can avoid direct coupling of the duty cycle to cause coupling between multiple DC converters.

It is worth noting that in the pulse width modulation mode and the voltage regulation mode, the purpose of the command V _Ref is not to operate the solar module 111 at the maximum power point. However, in the maximum power point tracking mode, the command V _Ref calculated by the central controller 170 is to allow the solar module 111 to operate at the maximum power point, but the present invention does not limit the algorithm used by the central controller 170. To calculate the instruction V _Ref . In an embodiment, the central controller 170 may use the algorithm proposed by the Republic of China Invention Patent Publication No. 201100995, but the present invention should not be limited thereto. It is worth noting that the power of the solar module 111 may not be high or unstable at the beginning of the decentralized solar power system 100. Therefore, the conversion control circuit 131 is not suitable for directly entering the voltage regulation mode or the maximum power point tracking mode. . Therefore, in the booting process, the central controller 170 controls the switching control circuit 131 to sequentially enter the pulse width modulation mode, the voltage regulation mode, and the maximum power point tracking mode. The startup procedure will be described in detail below.

FIG. 3A and FIG. 3B are schematic diagrams showing the flow of a booting process according to an embodiment. Please refer to FIG. 2, FIG. 3A and FIG. 3B simultaneously. Here, the inverter 180, the conversion control circuit 131 and the central controller 170 are taken as an example to illustrate the booting procedure, but the flow of FIG. 3A and FIG. 3B can also be used in other On the conversion control circuit.

In step 301, the inverter 180 is in the acknowledgment mode, at which time the inverter 180 does not convert the DC point to AC power. At the same time, in step 302, the conversion control circuit 131 obtains the voltage information V _pv from the voltage sensor 201 to determine whether the open circuit voltage of the solar module 111 is greater than an open circuit voltage threshold. For example, the open circuit voltage threshold can be set to 32 volts (volts, V), but in practice, different open circuit voltage thresholds can be set according to different solar modules.

In step 303, the central controller 170 calculates the number of normal modules, and the number of normal modules indicates that several solar modules are open. The road voltage is already greater than the open circuit voltage threshold. If the number of normal modules is greater than a preset number of power-on, step 305 is entered to set the PWM parameters; if the number of normal modules is not greater than the preset number of power-on, then the process returns to step 303 and continues to wait.

After the PWM parameters are set, in step 306, the central controller 170 transmits an instruction to the conversion control circuit 131, causing the conversion control circuit 131 to enter the PWM mode. At this time, the switching control circuit 131 controls the DC converter 121 to raise or lower the output voltage of the solar module 111. In one embodiment, the input of the inverter 180 is a high voltage direct current (for example, between 360V and 400V), the output is 220V alternating current, and the output voltage of the solar module 111 is about 32V, and one There are 8 solar modules in the photovoltaic string, so most DC converters are in boost mode.

When the potential difference of the direct current input to the inverter 180 is greater than a certain value (for example, 100 V), the inverter 180 enters a standby mode (step 307), at which time the inverter 180 does not start generating alternating current. The central controller 170 determines whether the potential difference of the direct current input to the inverter 180 is greater than a potential difference threshold (for example, 320 V). If the potential difference of the direct current on the inverter 180 is already greater than 320V, the central controller 170 waits for a preset time (for example, 30 seconds), and then controls all the conversion control circuits on the photovoltaic string in steps 308 and 309. The potential difference of the direct current is adjusted to a preset power generation potential difference (for example, 360V).

In step 310, the central controller 170 determines whether the potential difference of the direct current on the inverter 180 can be successfully adjusted to the preset power generation potential. difference. If so, the inverter 180 will enter the operational mode (step 311), at which point the inverter 180 will convert the direct current to alternating current. If the result of step 310 is no, the central controller 170 executes a shutdown procedure (step 312).

After the inverter 180 enters the operating mode, in step 313, the central controller 170 sets the steady-state mode parameter to transmit an instruction to the conversion control circuit 131. In step 314, the conversion control circuit 131 switches to the voltage regulation mode. In step 315, the central controller 170 determines whether the conversion control circuit 131 can regulate the output voltage of the solar module 111 according to the command. If the result of step 315 is no, the central controller 170 executes a shutdown procedure (step 312). In another embodiment, if the conversion control circuit 131 cannot regulate the output voltage of the solar module 111 according to the command, the central controller 170 sets the conversion control circuit 131 to the bypass operation mode. In the bypass mode of operation, the output of the DC converter 121 is conductive. As a result, there will not be a solar module abnormality that will make the other solar modules on the entire photovoltaic string inoperable.

If the result of step 315 is yes, in step 316, the central controller 170 sets the parameters of the maximum power point tracking mode to transmit commands to the conversion control circuit 131. In step 318, the switching control circuit 131 switches to the maximum power point tracking mode. It should be noted that in the maximum power point tracking mode, the switching control circuit 131 can still use the function of the voltage regulator controller 210 to control the output voltage of the solar module 111.

Next, in step 319, the central controller 170 determines whether an operating power of the inverter 180 is greater than a power threshold. Here, the operating power of the inverter 180 can be input power or output power. rate. If the operating power of the inverter 180 is greater than the power threshold, the inverter 180 will remain in the operating mode in step 311. If the result of step 319 is no, the central controller 170 performs a shutdown procedure.

Referring back to FIG. 1, after the booting process is completed, the inverter 180 continuously converts the direct current into alternating current. In the normal case, the direct current converters 121-123 are in the boost mode. However, the output power of the solar modules 111-113 may change with the weather. For example, if the cloud shields the sunlight, the output power of the solar modules 111-113 may decrease. It is assumed that the solar module 111 is affected by the shielding, and the output power of the solar module 111 is lowered. However, since the DC converters 121 to 123 are connected in series, the current output from the DC converter 121 is reduced. The current on the photovoltaic string 110, in turn, affects the solar modules outside of the solar module 111. Therefore, in the general case, the central controller 170 may choose to lower the output voltage of the DC converter 121. However, if the output voltage of the DC converter 121 continues to decrease, the output voltage of the DC converter 121 will be closer to the input voltage. If the conversion ratio of the DC converter 121 is close to 1, it means that the DC converter 121 frequently switches between the boost mode and the buck mode, which causes an abnormal phenomenon. Therefore, this embodiment also proposes a special operation flow to solve this problem.

4 is a schematic flow chart showing a special operation flow according to an embodiment. Referring to FIG. 2 and FIG. 4, the inverter 180 is in the operating mode in step 401, while the switching control circuit 131 is in the maximum power point tracking mode in step 402. In step 403, the central controller 170 obtains the output voltage of the DC converter 121. In step 404, the central controller 170 will determine if the output voltage of the DC converter 121 is less than a first threshold (for example, 30V). If the result of step 404 is no, then in step 405, central controller 170 maintains transition control circuit 131 in the maximum power point tracking mode.

On the other hand, if the output voltage of the DC converter 121 is lower than the first threshold, in step 406, the central controller 170 switches the switching control circuit 131 from the maximum power point tracking mode to the voltage stabilization mode for fixing. The input voltage of the DC converter 121 (ie, the output voltage of the solar module 111).

In step 407, the central controller 170 determines if the regulation control is normal. In this embodiment, the central controller 170 is the control switching control circuit 131 such that the input voltage and output voltage of the DC converter 121 will be greater than a threshold threshold (eg, 1V). If the central controller 170 cannot control the difference between the input voltage and the output voltage of the DC converter 121 to be greater than the threshold value, it indicates that the voltage regulation control is abnormal, and the process proceeds to step 408. In another aspect, the central controller 170 can also determine whether the control switching control circuit 131 can regulate the input voltage of the DC converter 121 according to the received command. If not, the voltage regulation control is abnormal.

In step 408, the central controller 170 switches the switching control circuit 131 to the PWM mode and causes the DC converter 121 to enter the buck mode. The purpose of the DC converter 121 to enter the buck mode is to keep the input voltage of the DC converter 121 from being too close to the output voltage. For example, please refer to FIG. 5 and FIG. 6. FIG. 5 is a diagram showing DC conversion without special operation flow. The voltage curve of the device, and FIG. 6 is a voltage graph of the DC converter when a special operation flow is illustrated according to an embodiment. In FIG. 5, the output voltage of the DC converter is always degraded due to the influence of the shadowing, and the input voltage is violently oscillated in the region 510 because the DC converter frequently switches between the boost mode and the buck mode. In the region 610 of Figure 6, the voltage regulation mode, that is, the central controller controls the output voltage of the DC converter to be more than 1V from the input voltage. However, after the region 610, the output voltage and input voltage of the DC converter are already less than 1V, so the DC converter will be forced into the buck mode, so that the DC converter will not frequently switch between the boost mode and the buck. Between modes.

Referring back to FIG. 4, after the DC converter enters the buck mode, since the central controller 170 cannot determine whether the solar module can output a higher voltage due to the power increase, the central controller 170 sets a check cycle, and The switching control circuit 131 is switched to the voltage stabilizing mode every other check cycle. This check period is, for example, one minute, but in other embodiments the check period may be longer or shorter, and the present invention is not limited thereto. Specifically, after step 408 and after waiting for the check cycle, the central controller 170 returns to step 406 to switch the switch control circuit back to the voltage stabilizing mode. Next, in step 407, it is continued to determine whether the regulation control is normal. If the result of step 407 is YES, then return to step 403 and step 404. If it is determined in step 404 that the output voltage of the DC converter 121 is greater than or equal to the first threshold, then the process proceeds to step 405, and the central controller 170 switches the switching control circuit 131 to the maximum power point tracking mode. Conversely, if the result of step 407 is no, then it returns to step 408 and continues to wait for the check cycle. please Referring to Figure 7, Figure 7 is a schematic diagram illustrating a check cycle in accordance with an embodiment. As can be seen from Figure 7, it will continue for a while after entering the buck mode, and then try to enter the regulation mode again. If it is unable to regulate, it will return to the buck mode.

FIG. 8 is a flow chart showing a shutdown procedure according to an embodiment. Referring to FIG. 8, the inverter 180 is in the active mode in step 801, while the conversion control circuit 131 is in the maximum power point tracking mode in step 802. In some cases, a shutdown procedure is triggered in step 803. For example, in the first case, the user triggers a shutdown procedure by sending a command to the central controller 170 via a computer. In the second case, the operating power of the inverter 180 (which may be input power or output power) is too low to be less than a power threshold. In the third case, the output voltage of a DC converter is too high and is greater than an output voltage threshold. Since the components in the DC converter have an upper limit of withstand voltage, the shutdown procedure must be performed in order to avoid the component being burned. In the fourth case, when the operating voltage of the inverter 180 (which may be an input voltage or an output voltage) is abnormal, for example, the central controller 170 may perform an algorithm to detect whether the distributed solar power system 100 has an islanding effect. (The output voltage of the inverter 180 may be greater than the voltage on the mains grid 190) to determine if a shutdown procedure is to be performed.

If the shutdown procedure is triggered, in step 804, the central controller 170 first sets the parameters of the voltage regulation mode and transmits the command to the conversion control circuit 131. In step 805, the conversion control circuit 131 switches to the voltage stabilization mode after receiving the instruction. Further, in step 806, the central controller 170 also sets parameters of the PWM mode and transmits commands to the conversion control circuit 131. In step 807, the conversion control circuit 131 switches to The PWM mode is to adjust the output voltage of the DC converter 121 to zero. In step 808, the inverter 180 is still in the working mode, but as the output voltages of all the DC converters on the photovoltaic string are adjusted to zero, the potential difference of the direct current on the inverter 180 will also be zero, and the central controller 170 will The inverter 180 is switched to the confirm mode after the inverter 180 releases the power (step 809). On the other hand, in step 810, the central controller 170 will shut down, at which point the switch control circuit 131 will be in the acknowledgment state (confirm open circuit voltage) in step 811.

FIG. 9 is a flow chart showing a control method of a distributed solar power generation system according to an embodiment. Referring to FIG. 9, in step 901, power information from the conversion control circuit is received, and a boot process is executed to control the conversion control circuit to sequentially enter the pulse width modulation mode, the voltage regulation mode, and the maximum power point tracking mode. In step 902, it is determined whether the output voltage of the DC converter is lower than the first threshold. If the output voltage in the DC converter (hereinafter referred to as the first DC converter) is lower than the first threshold, in step 903, the first conversion control circuit coupled to the first DC converter is controlled from the maximum power. The point tracking mode is switched to the regulation mode to fix the input voltage of the DC converter. In step 904, it is determined whether the difference between the input voltage and the output voltage of the first DC converter is less than the threshold threshold. If the result of step 904 is YES, in step 905, the first switching control circuit is controlled to switch from the regulated mode to the pulse width modulation mode to cause the first DC converter to enter the buck mode.

However, the steps in FIG. 9 have been described in detail above, and will not be described again here. It is worth noting that the steps in Figure 9 can be implemented as multiple steps. The code or circuit, the invention is not limited thereto. In addition, the method of FIG. 9 can be used in conjunction with the above embodiments, or can be used alone. For example, if the result of step 904 is no, it may be further determined according to the flow of FIG. 4 whether the first conversion control circuit is to be switched back to the maximum power point tracking mode, and the present invention is not limited thereto.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention, and any one of ordinary skill in the art can make some changes and refinements without departing from the spirit and scope of the present invention. The scope of the invention is defined by the scope of the appended claims.

901~905‧‧‧Steps

Claims (10)

A decentralized solar power generation system includes: a plurality of solar modules; a plurality of DC converters, wherein each of the DC converters has a boost mode and a buck mode, and the input ends of each of the DC converters are coupled Connected to one of the solar modules, the outputs of the DC converters are connected in series to each other such that the solar modules and the DC converters form a photovoltaic string; a plurality of conversion control circuits are respectively coupled and coupled Controlling the DC converters and obtaining a plurality of power information of the solar modules; and a central controller receiving the power information from the conversion control circuits to execute a booting procedure of the distributed solar power generation system And a shutdown program, wherein in the booting process, the central controller controls the conversion control circuits to sequentially enter a pulse width modulation mode, a voltage stabilization mode, and a maximum power point tracking mode, after executing the booting process When an output voltage of a first one of the DC converters is lower than a first threshold, the central controller controls the a first conversion control circuit coupled to the DC converter is switched from the maximum power point tracking mode to the voltage regulation mode for fixing an input voltage of the first DC converter, when the first conversion control circuit In the voltage regulation mode, the difference between the input voltage of the first DC converter and the output voltage is less than a difference When the threshold value is reached, the central controller controls the first switching control circuit to switch from the voltage stabilizing mode to the pulse width modulation mode, so that the first DC converter enters the buck mode. The distributed solar power generation system of claim 1, wherein after the first switching control circuit switches from the voltage stabilizing mode to the pulse width modulation mode, the central controller sets a check cycle, each time the check cycle is passed The central controller switches the first conversion control circuit from the pulse width modulation mode to the voltage regulation mode and determines whether a difference between the input voltage of the first DC converter and the output voltage is greater than or equal to a threshold value, if the difference between the input voltage of the first DC converter and the output voltage is greater than or equal to the threshold value, the output voltage of the central controller at the first DC converter is greater than or equal to The first threshold control circuit switches the first switching control circuit to the maximum power point tracking mode. The decentralized solar power generation system of claim 1, further comprising an inverter coupled to the photovoltaic string for converting the direct current provided by the photovoltaic string into an alternating current, in the booting process, the central The controller determines, according to the power information, whether an open circuit voltage of each of the solar modules is greater than an open circuit voltage threshold to calculate a normal module number, wherein the inverter is in an acknowledge mode. If the number of the normal modules is greater than a preset number of power-on, the central controller controls the switching control circuits to enter the pulse width modulation mode, and controls the inverter to switch to a standby mode, and the central controller determines the DC Whether a potential difference of the voltage is greater than a potential difference threshold, if the potential difference of the DC voltage is greater than the potential difference threshold, the central controller controls the conversion control circuits to wait for a preset time to adjust the potential difference of the DC voltage Up to a preset power generation potential difference. The distributed solar power generation system of claim 3, wherein if the potential difference of the DC voltage is not adjusted to the preset power generation potential difference, the central controller performs the shutdown procedure, if the potential difference of the DC voltage is adjusted to The preset power generation potential difference, the central controller controls the inverter to enter an operating mode, and controls the switching control circuits to enter the voltage stabilizing mode, in the voltage stabilizing mode, the central controller determines the switching control circuits Whether the output voltage of each of the solar modules can be regulated according to at least one command, if a second conversion control circuit of the conversion control circuits is unable to regulate the solar module corresponding to the at least one command Outputting a voltage, the central controller executing the shutdown procedure or setting the second conversion control circuit to a bypass operation mode, wherein the output of the DC converter corresponding to the second conversion control circuit in the bypass operation mode To be conductive, If it is determined that the conversion control circuit determines that the output voltages of the solar modules can be stabilized according to the at least one command, the central controller controls the conversion control circuits to enter the maximum power point tracking mode, at the maximum power point In the tracking mode, if a working power of the inverter is greater than a minimum operating power threshold, the central controller controls the inverter to maintain the working mode, if the operating power of the inverter is not greater than the minimum operating The power threshold, the central controller performs the shutdown procedure. The distributed solar power generation system of claim 4, wherein the central controller outputs an output voltage of one of the DC converters when the operating power of the inverter is lower than the minimum operating power threshold The shutdown program is executed when an output voltage threshold is abnormal or when the operating voltage of the inverter is abnormal. In the shutdown procedure, the central controller controls the conversion control circuits to enter the voltage stabilization mode, and then controls the The switching control circuit enters the pulse width modulation mode to adjust the output voltage of the DC converters to zero. In the shutdown procedure, the central controller takes the inverter from the work after the inverter releases the power The mode switches to this confirmation mode. A control method for a distributed solar power generation system, wherein the distributed solar power generation system includes a plurality of solar modules, and a plurality of straight And a plurality of conversion control circuits, wherein each of the DC converters has a boost mode and a buck mode, and an input end of each of the DC converters is coupled to one of the solar modules The output terminals of the DC converters are connected in series with each other to form a photovoltaic string with the DC converters, and the conversion control circuits respectively couple and control the DC converters to obtain the solar modules. The plurality of power information of the group includes: receiving the power information from the conversion control circuits, executing a booting process of the distributed solar power system to control the switching control circuits to sequentially enter a pulse width adjustment a variable mode, a voltage stabilizing mode, and a maximum power point tracking mode; after the booting process is executed, when an output voltage of a first DC converter of the DC converters is lower than a first threshold, the control A first switching control circuit coupled to the first DC converter switches from the maximum power point tracking mode to the voltage stabilizing mode for fixing the first DC conversion An input voltage of the device; and controlling the first when the first conversion control circuit is in the voltage regulation mode and the difference between the input voltage of the first DC converter and the output voltage is less than a threshold threshold The switching control circuit switches from the regulated mode to the pulse width modulation mode to cause the first DC converter to enter the buck mode. The control method as claimed in claim 6 further includes: After the first switching control circuit switches from the voltage stabilizing mode to the pulse width modulation mode, setting a check cycle; switching the first switching control circuit from the pulse width modulation mode to the check cycle And determining whether the difference between the input voltage of the first DC converter and the output voltage is greater than or equal to the threshold threshold; and if the input voltage of the first DC converter and the output voltage are The difference between the gaps is greater than or equal to the threshold value, and the first switching control circuit is switched to the maximum power point tracking mode after the output voltage of the first DC converter is greater than or equal to the first threshold. The control method of claim 7, wherein the distributed solar power generation system further comprises an inverter coupled to the photovoltaic string for converting the direct current provided by the photovoltaic string into an alternating current, the control method further The method includes: determining, according to the power information, whether an open circuit voltage of each of the solar modules is greater than an open circuit voltage threshold to calculate a normal module number, wherein the inverter is in an acknowledge mode If the number of the normal modules is greater than a preset number of power-on, control the switching control circuits to enter the pulse width modulation mode, and control the inverter to switch to a standby mode; determine whether a potential difference of the DC voltage is greater than one Potential difference threshold; If the potential difference of the DC voltage is greater than the potential difference threshold, the switching control circuit is controlled to wait for a predetermined time to adjust the potential difference of the DC voltage to a predetermined power generation potential difference. The control method of claim 8, further comprising: if the potential difference of the DC voltage is not adjusted to the preset power generation potential difference, performing the shutdown procedure; if the potential difference of the DC voltage is adjusted to the preset power generation potential difference Controlling the inverter to enter an operating mode, and controlling the switching control circuits to enter the voltage stabilizing mode; in the voltage stabilizing mode, determining whether the switching control circuits can stabilize each of the plurality of instructions according to at least one instruction An output voltage of the solar module; if a second conversion control circuit of the conversion control circuits is unable to perform the shutdown process or the second according to the output voltage of the solar module corresponding to the at least one command voltage regulation The switching control circuit is set to a bypass operation mode, in which the output end of the DC converter corresponding to the second conversion control circuit is turned on; if it is determined that the conversion control circuits can be based on the at least one instruction Regulating the output voltages of the solar modules to control the conversion control circuits to enter the maximum power point tracking mode; In the power point tracking mode, if an operating power of the inverter is greater than a minimum operating power threshold, controlling the inverter to maintain the operating mode; If the operating power of the inverter is not greater than the minimum operating power threshold, the shutdown procedure is performed. The control method of claim 9, further comprising: when the operating power of the inverter is lower than the minimum operating power threshold, the output voltage of one of the DC converters is greater than an output voltage threshold And when the operating voltage of the inverter is abnormal, performing the shutdown procedure; in the shutdown procedure, controlling the conversion control circuits to enter the voltage stabilization mode, and then controlling the conversion control circuits to enter the pulse width modulation The mode is to adjust the output voltage of the DC converters to zero; in the shutdown procedure, the inverter is switched from the operating mode to the confirmation mode after the inverter releases the power.