CN108565891B - Photovoltaic group string turn-off device and method and photovoltaic system - Google Patents
Photovoltaic group string turn-off device and method and photovoltaic system Download PDFInfo
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Abstract
The invention discloses a photovoltaic string turn-off device which comprises a switch device, a collecting device and a turn-off controller. When the shutdown controller judges that the operation signal acquired by the acquisition device meets a preset shutdown condition, the MPPT unit is triggered to enter a string shutdown mode from a current maximum power tracking mode, so that the voltage corresponding to the maximum power of each photovoltaic string is increased to an open-circuit voltage, and when the open-circuit voltage is reached, the shutdown controller controls a target switch device on a loop with abnormity to be disconnected. When the open-circuit voltage is reached, the current output by the photovoltaic string approaches zero, the requirement on a switching device is low, and the photovoltaic string can be reliably disconnected; in addition, after the target switching device is disconnected, the input current, voltage and power of the direct current side of the inverter unit are very small, phenomena such as overheating and electric leakage are not easy to cause, and the direct current turn-off device can be turned off reliably. In addition, the invention also discloses a photovoltaic string shutdown method and a photovoltaic system, and the effect is as above.
Description
Technical Field
The invention relates to the technical field of photovoltaic power generation, in particular to a photovoltaic string turn-off device and method and a photovoltaic system.
Background
At present, the photovoltaic system is widely applied, and particularly, the distributed photovoltaic system is popularized. Although the development of photovoltaic systems has led to better utilization of renewable energy sources, photovoltaic systems have also brought about problems in recent years, for example, photovoltaic fire accidents have gradually threatened the safety of residential buildings, commercial facilities, public facilities and their photovoltaic systems. The photovoltaic system comprises a photovoltaic string, an MPPT unit (MPPT, namely maximum power point tracking) connected with the photovoltaic string, an inversion unit, a direct current side turn-off device and other components. The MPPT unit is mainly used for controlling the photovoltaic strings to work at a maximum power point, the MPPT unit is mainly used for controlling each photovoltaic string to work at a maximum power mode, the inversion unit is mainly used for carrying out inversion output on direct current generated by the photovoltaic strings, and the direct current side turn-off device is used on the direct current side of the inversion unit and used for cutting off input of the inversion unit, so that the reliability and stability of the direct current side turn-off device are directly related to stable power generation and income of a photovoltaic system, and safe and reliable operation of the photovoltaic system is directly influenced.
In the prior art, most of the dc-side turn-off devices used on the dc side of the inverter unit are ac switches or their improved products, and therefore, the dc-side turn-off devices are not dc switch devices with safety arc extinction and high power cut-off really applied in the photovoltaic system. The arc extinguishing capacity and rated load cut-off power of the switches are far from enough, so that overheating, electric leakage and sparks are easily caused, and the whole photovoltaic power station is even burnt out in severe cases. Meanwhile, as the voltage level of the direct current side of the photovoltaic system is gradually increased to 1500V, the power level of a single machine is increased, the requirements of the inverter unit on the withstand voltage level and the breaking capacity of the direct current side turn-off device are stricter, the direct current side turn-off device in the market possibly has design defects, so that the switch cannot be completely cut off, even an arc discharge phenomenon is generated, and the generated huge heat becomes the hidden danger of an electrical fire of the photovoltaic system.
In summary, how to ensure reliable turn-off of the dc-side turn-off device is an urgent problem to be solved by those skilled in the art.
Disclosure of Invention
The invention aims to provide a photovoltaic string turn-off device, a photovoltaic string turn-off method and a photovoltaic system, which are used for ensuring the reliable turn-off of a direct-current side turn-off device.
In order to solve the technical problem, the invention provides a photovoltaic string turn-off device which comprises a switch device arranged on each photovoltaic string loop, a collecting device used for collecting operation signals of each photovoltaic string loop, and a turn-off controller connected with the collecting device and an MPPT unit; the switching-off controller is used for triggering the MPPT unit to enter a string switching-off mode from a current maximum power tracking mode when the operation signal meets a preset switching-off condition so that the MPPT unit controls each photovoltaic string loop to increase from a voltage corresponding to the maximum power to an open-circuit voltage, and controls a target switching device to be switched off when the open-circuit voltage is reached.
Preferably, the shutdown controller specifically includes an a/D conversion device connected to the acquisition device, a signal conditioning device connected to the a/D conversion device, and an MCU connected to the signal conditioning device.
Preferably, the switching device is specifically a relay, a contact of the relay is arranged on the photovoltaic group series circuit, and a coil of the relay is connected with the turn-off controller.
Preferably, the MPPT circuit further comprises diodes arranged on each photovoltaic string loop, anodes of the diodes are connected with the photovoltaic strings, and cathodes of the diodes are connected with the MPPT unit.
Preferably, the shutdown controller is further configured to trigger the MPPT unit to enter the string shutdown mode when an external shutdown control instruction is received.
Preferably, the turn-off controller is further configured to trigger the MPPT unit to enter the maximum power tracking mode after the target switching device is turned off.
Preferably, the collecting device is a current sensor, a voltage sensor, and a temperature sensor, and the corresponding operating signal is a current of the photovoltaic string loop, a voltage of the photovoltaic string loop, and a temperature of the photovoltaic string loop.
In order to solve the above technical problem, the present invention further provides a method for shutting off a photovoltaic string, including:
collecting operation signals of each photovoltaic group string loop;
and acquiring the operation signal, triggering the MPPT unit to enter a string shutdown mode from a current maximum power tracking mode when the operation signal meets a preset shutdown condition so that the MPPT unit controls each photovoltaic string loop to increase from a voltage corresponding to the maximum power to an open-circuit voltage, and controlling a switching device arranged on a target photovoltaic string loop to be switched off when the open-circuit voltage is reached.
Preferably, after determining that the operating signal does not satisfy the preset turn-off condition, the method further includes:
judging whether an external turn-off control instruction is received or not;
and if so, triggering the MPPT unit to enter the string shutdown mode.
In order to solve the technical problem, the invention provides a photovoltaic system which comprises the photovoltaic string turn-off device.
The invention provides a photovoltaic string turn-off device, which comprises a switch device, a collecting device and a turn-off controller, wherein, the switch device is arranged on each photovoltaic group string loop and is controlled by the turn-off controller to realize the turn-on and turn-off, the acquisition device acquires the running signal on each photovoltaic group string loop, then the signal is sent to a shutdown controller, the shutdown controller judges whether the running signal is abnormal or not by utilizing a preset algorithm, namely whether the preset turn-off condition is met, if so, the circuit in which the running signal is positioned is abnormal, the shutdown controller triggers the MPPT unit connected thereto to enter the string shutdown mode from the current maximum power tracking mode, the MPPT unit controls each pv string to increase from a voltage corresponding to the maximum power to an open-circuit voltage, the turn-off controller controls the target switching device on the loop where the abnormality occurs to be turned off when the open circuit voltage is reached. Obviously, when the open-circuit voltage is reached, the current output by the photovoltaic string approaches zero, so that the requirements on the switching device are low, and the switching device can be reliably switched off; in addition, after the target switching device is disconnected, the input current, voltage and power of the direct current side of the inverter unit are very small, phenomena such as overheating and electric leakage are not easy to cause, and the direct current turn-off device can be turned off reliably. In conclusion, the device can reduce the requirement on the direct current turn-off device, improve the reliable turn-off of the direct current side of the inverter unit and prevent the photovoltaic system from generating potential hazards such as electrical fire and the like.
Drawings
In order to illustrate the embodiments of the present invention more clearly, the drawings that are needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings can be obtained by those skilled in the art without inventive effort.
Fig. 1 is a structural diagram of a photovoltaic string shutdown device according to an embodiment of the present invention;
fig. 2 is a structural diagram of a photovoltaic system according to an embodiment of the present invention;
fig. 3 is a schematic diagram illustrating voltage and current variations of a string circuit according to the present invention;
fig. 4 is a flowchart corresponding to an active shutdown mode according to an embodiment of the present invention;
fig. 5 is a flowchart corresponding to a passive shutdown mode according to an embodiment of the present invention;
fig. 6 is a flowchart of a method for shutting down a photovoltaic string according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments of the present invention without any creative work belong to the protection scope of the present invention.
The core of the invention is to provide a photovoltaic string shutdown device, a method and a photovoltaic system, wherein the device aims to improve the reliable shutdown of a direct current side shutdown device.
In order that those skilled in the art will better understand the disclosure, the invention will be described in further detail with reference to the accompanying drawings and specific embodiments.
Example one
Fig. 1 is a structural diagram of a photovoltaic string shutdown device according to an embodiment of the present invention. As shown in fig. 1, the apparatus includes a switching device 10 disposed on each photovoltaic string loop, a collecting device 11 for collecting an operation signal of each photovoltaic string loop, and a turn-off controller 13 connected to the collecting device 11 and the MPPT unit 12; the shutdown controller 13 is configured to trigger the MPPT unit 12 to enter a string shutdown mode from a current maximum power tracking mode when the operation signal meets a preset shutdown condition, so that the MPPT unit 12 controls each photovoltaic string loop to increase a voltage corresponding to the maximum power to an open-circuit voltage, and controls the target switching device to be turned off when the open-circuit voltage is reached.
The object of the invention is to increase the reliable switching off of a dc-side switching-off device, on the basis of which the solution is to improve the dc-side switching-off device itself on the one hand and to reduce the requirements on the dc-side switching-off device on the other hand, which is the solution provided by the invention.
Fig. 2 is a structural diagram of a photovoltaic system according to an embodiment of the present invention. It should be noted that, in general, a photovoltaic system includes a plurality of photovoltaic string circuits, PV 1-PVN. Each photovoltaic group string loop corresponds to one group of switch devices (one switch device can be multiple) and one group of collecting devices (one type of sensor can be used, multiple types of sensors can be used), the switch devices are mutually independent and can only realize the on-off of the loop, and the collecting devices are mutually independent and can only collect the running signals of the loop.
In a specific implementation, the operation mode of the MPPT unit is divided into a maximum power tracking mode and a string shutdown mode, and the control of the two modes is determined by a control signal of a shutdown controller. Fig. 3 is a schematic diagram of voltage and current variations of a photovoltaic string loop according to the present invention. Wherein the abscissa represents the voltage value and the ordinate represents the current value. When the working point of the I-V curve is positioned at the maximum power point MPP, the maximum power tracking mode is adopted; and when the voltage of the working point of the I-V curve is positioned at the Uoc, the string cutting-off mode is realized. The two modes are switched by actively adjusting the working voltage of the string. Under normal conditions, the turn-off controller sends a control signal for entering a maximum power tracking mode to the MPPT unit, at the moment, the MPPT unit controls the voltage of each photovoltaic group string to operate at the voltage corresponding to the maximum power point according to the maximum power tracking mode, and under the mode, the voltage of each photovoltaic group string loop is at the voltage U corresponding to the maximum power pointMPPThe voltage is usually high, for example, 800V in fig. 3, at this time, the voltage borne by the dc-side shutdown device on the dc side of the inverter unit is also 800V, if the photovoltaic string loop is abnormal, the dc-side shutdown device needs to cut off the input of the inverter unit under the condition of 800V voltage, obviously, the requirement for the dc-side shutdown device is very high, and once the dc-side shutdown device does not meet the requirement, accidents such as fire disasters and the like easily occur to the photovoltaic system. Based on this, in this embodiment, the shutdown controller pre-writes the judgment logic of the operation signal, that is, what type of operation signal should meet what kind of requirement, and once the operation signal is not met, it indicates that the pv string loop corresponding to the operation signal is abnormal, and the shutdown controller triggers the MPPT unit to enter the MPPT from the current maximum power tracking mode according to the judgment resultString off mode. At the moment, the MPPT unit adjusts the voltage on the corresponding photovoltaic string loop to be increased to the open-circuit voltage U according to a preset algorithmOCIn this case, the turn-off controller is turned off by the switching device connected to the turn-off controller (i.e., the target switching device, which is a switching device corresponding to the abnormal pv string loop), so that the corresponding pv string loop is turned off. When the target switching device is disconnected, the input current, voltage and power of the direct current side of the inverter unit are very small, the phenomena of overheating, electric leakage and the like are not easy to cause, and the direct current turn-off device can be turned off reliably.
For the sake of clarity, the adjusting of the voltage on the corresponding pv string loop to the open-circuit voltage U mentioned in the present invention is performed by those skilled in the artOCThis embodiment will be described in detail. Firstly, the working voltage U of the lifting systemOPI.e. the operating voltage UOPFrom maximum power voltage UMPPThe working voltage delta U of the system is lifted by starting to accumulate fixed step length voltage, and the working voltage after each adjustment is UOP＝UOP+. DELTA.U; u for simultaneously optimizing maximum working voltageOP≥Max[UOP,UMPP]Meanwhile, the working voltage U is judged by combining whether the current is minimum or notOPWhether it settles at the voltage maximum, i.e. whether the open circuit voltage Uoc is reached. The adjustment result of the open circuit voltage mode is the string working current IOPReaching a minimum limit value I of the off-currentrefThe switching device of the ith loop may be switched off. Then, short-time software delay delta T is carried out, and the action of the switch device is completely finished.
It should be noted that the preset shutdown condition in this embodiment may determine the condition itself according to the type of the operation signal acquired by the acquisition device, for example, if the operation signal is a current signal, the preset shutdown condition may be a range related to a current value, and if the preset shutdown condition exceeds the range (over-current detection), the preset shutdown condition is considered to be abnormal, that is, the preset shutdown condition is satisfied. Other types of operation signals are the same as above, and are not described in detail. As a preferred embodiment, the collecting device is specifically a current sensor, a voltage sensor, and a temperature sensor, and the corresponding operating signal is specifically a current of the photovoltaic string loop, a voltage of the photovoltaic string loop, and a temperature of the photovoltaic string loop. It will be appreciated that there are many types of operating signals, and that the preferred embodiments described above are only three of these and are not intended to represent only these three types of signals.
In addition, an electrical topology circuit corresponding to the MPPT unit is mainly a single-phase or three-phase H-bridge type inverter circuit in a first-stage inverter topology; in the two-stage inversion topology, a DC/DC booster circuit and a DC/AC inversion circuit are mainly used.
The application scenario of the string shutdown device provided by the present invention is not limited, and the string shutdown device may be applied to a pre-stage BOOST type MPPT unit of a pre-stage combiner box of a string inversion unit or a distributed inversion unit, and may also be applied to a three-phase H-bridge inversion type MPPT unit of a centralized inversion unit.
The photovoltaic string shutdown device provided by the embodiment comprises a switching device, a collecting device and a shutdown controller, wherein, the switch device is arranged on each photovoltaic group string loop and is controlled by the turn-off controller to realize the turn-on and turn-off, the acquisition device acquires the running signal on each photovoltaic group string loop, then the signal is sent to a shutdown controller, the shutdown controller judges whether the running signal is abnormal or not by utilizing a preset algorithm, namely whether the preset turn-off condition is met, if so, the circuit in which the running signal is positioned is abnormal, the shutdown controller triggers the MPPT unit connected thereto to enter the string shutdown mode from the current maximum power tracking mode, the MPPT unit controls each pv string to increase from a voltage corresponding to the maximum power to an open-circuit voltage, the turn-off controller controls the target switching device on the loop where the abnormality occurs to be turned off when the open circuit voltage is reached. Obviously, when the open-circuit voltage is reached, the current output by the photovoltaic string approaches zero, which is equivalent to load reduction or even no load, so that the requirements on the switching device are low, and the switching device can be reliably switched off; in addition, after the target switching device is disconnected, the input current, voltage and power of the direct current side of the inverter unit are very small, phenomena such as overheating and electric leakage are not easy to cause, and the direct current turn-off device can be turned off reliably. In conclusion, the device can reduce the requirement on the direct current turn-off device, improve the reliable turn-off of the direct current side of the inverter unit and prevent the photovoltaic system from generating potential hazards such as electrical fire and the like.
As a preferred embodiment, the shutdown controller specifically includes an a/D conversion device connected to the acquisition device, a signal conditioning device connected to the a/D conversion device, and an MCU connected to the signal conditioning device.
In general, the operation signal acquired by the acquisition device is an analog signal, and the analog signal needs to be converted into a digital signal for subsequent logic determination. The signal conditioning device is used for performing signal conditioning on the received signal, wherein the signal conditioning includes operations of signal amplification, filtering and the like. The MCU is a core device for performing logic judgment, and may be a single chip microcomputer, and the like, which is not described in this embodiment.
In a preferred embodiment, the switching device is embodied as a relay, the contacts of which are arranged on the photovoltaic array series circuit, and the coil of which is connected to the switch-off controller.
Relays are commonly used in automated control circuits, which are actually "reclosers" that use small currents to control large current operation. Therefore, the circuit plays the roles of automatic regulation, safety protection, circuit conversion and the like. It should be noted that the switching device may be a contactor or other types of switches besides a relay, and this embodiment is not limited.
Example two
As shown in fig. 2, in addition to the first embodiment, as a preferred embodiment, the MPPT unit further includes a diode D provided on each of the photovoltaic string circuits, an anode of the diode D is connected to the photovoltaic string, and a cathode of the diode D is connected to the MPPT unit 12.
In the embodiment, the diode mainly has the reverse isolation function, and because PV + and PV-among different groups of strings converge in the MPPT unit, after the direct current of a certain group of strings is cut off, the high voltage at two ends of a contact of a switching device still has certain potential safety hazard; the diodes can prevent other strings or the rear stage of the MPPT unit from reversely pouring current of the strings. The photovoltaic string can be effectively prevented from being damaged by current reversal through the diode, parameters of the diode need to be determined according to actual parameters of a specific photovoltaic string loop, and the embodiment is not limited.
EXAMPLE III
In the above embodiment, the turn-off controller performs logic judgment according to the operation signal of the photovoltaic string loop, so as to control the MPPT unit to be in the maximum power tracking mode or the string turn-off mode. In specific implementation, in addition to the MPPT unit entering the string shutdown mode (active shutdown mode) caused by the abnormal operation signal, the shutdown controller is further configured to trigger the MPPT unit to enter the string shutdown mode (passive shutdown mode) when receiving the external shutdown control instruction.
The active turn-off mode is mainly a protective turn-off action made by the string turn-off device when overcurrent, leakage current, overvoltage, over-high temperature of the inverter unit, automatic load reduction, arc fault and fire hazard occur.
Fig. 4 is a flowchart corresponding to an active shutdown mode according to an embodiment of the present invention. As shown in fig. 4, the preset turn-off condition is 5 sub-conditions, including the following steps.
S40: whether the photovoltaic string loop is over-current;
s41: whether the photovoltaic string loop is over-voltage or not;
s42: whether the photovoltaic string loop leaks current or not;
s43: whether the inversion unit is over-temperature or not;
s44: whether an arc fault exists in the photovoltaic string.
If the above conditions are all negative, the sub-routine is judged to be finished, otherwise, if the judgment result of one condition is positive, the step S45 is executed;
s45: and marking the position 1 of an active turn-off mark of the corresponding photovoltaic group string loop.
The shutdown controller then triggers the MPPT unit to enter a string shutdown mode.
The passive turn-off mode mainly comprises the step of manually inputting a turn-off control instruction during power station routing inspection, component testing and maintenance, or receiving a turn-off control instruction sent by a superior measurement and control device. Fig. 5 is a flowchart corresponding to a passive shutdown mode according to an embodiment of the present invention. The external shutdown control instruction specifically includes a manual input shutdown instruction and a shutdown instruction issued by a higher level, as shown in fig. 5, and includes the following steps:
s50: whether a turn-off instruction is manually input or not;
s51: whether a shutdown instruction issued by the upper level exists or not.
If the above conditions are all negative, the sub-routine is judged to be finished, otherwise, if the judgment result of one condition is positive, the step S52 is executed;
s52: and marking the passive turn-off of the corresponding photovoltaic string loop at a position 1.
Example four
In the above embodiment, if an abnormality occurs in a certain photovoltaic string loop and the MPPT unit enters the string shutdown mode, the target switching device corresponding to the certain loop is turned off. At this time, the other pv string loops are still in a normal state, so the shutdown controller is further configured to trigger the MPPT unit to enter the maximum power tracking mode after the target switching device is turned off.
In this embodiment, can be after the unusual emergence, can control all the other photovoltaic group string return circuits in the photovoltaic system again and get into normal operating condition, avoid the long-time low efficiency operation of photovoltaic system.
EXAMPLE five
The embodiments described above are directed to a method for shutting down a photovoltaic string, and the present invention further provides embodiments corresponding to the method for shutting down the photovoltaic string. Fig. 6 is a flowchart of a method for shutting down a photovoltaic string according to an embodiment of the present invention. As shown in fig. 6, the method includes:
s60: collecting operation signals of each photovoltaic group string loop;
s61: the method comprises the steps of obtaining an operation signal, triggering the MPPT unit to enter a string shutdown mode from a current maximum power tracking mode when the operation signal meets a preset shutdown condition so that the MPPT unit controls each photovoltaic string loop to increase from a voltage corresponding to the maximum power to an open-circuit voltage, and controlling a switch device arranged on a target photovoltaic string loop to be disconnected when the open-circuit voltage is reached.
As a preferred embodiment, after determining that the operation signal does not satisfy the preset turn-off condition, the method further includes:
judging whether an external turn-off control instruction is received or not;
and if so, triggering the MPPT unit to enter a string shutdown mode.
Since the embodiment of the apparatus portion and the embodiment of the method portion correspond to each other, please refer to the description of the embodiment of the apparatus portion for the embodiment of the method portion, which is not repeated here.
The photovoltaic string shutdown method provided by this embodiment may judge the operation signal acquired by the acquisition device, and when it is judged that the operation signal satisfies the preset shutdown condition, trigger the MPPT unit to increase the voltage corresponding to the maximum power to the open-circuit voltage, and control the switching device arranged on the target photovoltaic string loop to be turned off when the open-circuit voltage is reached. Obviously, when the open-circuit voltage is reached, the current output by the photovoltaic string approaches zero, which is equivalent to load reduction or even no load, so that the requirements on the switching device are low, and the switching device can be reliably switched off; in addition, after the target switching device is disconnected, the input current, voltage and power of the direct current side of the inverter unit are very small, phenomena such as overheating and electric leakage are not easy to cause, and the direct current turn-off device can be turned off reliably. In conclusion, the method can reduce the requirement on the direct current turn-off device, improve the reliable turn-off of the direct current side of the inverter unit and prevent the photovoltaic system from generating hidden dangers such as electrical fire and the like.
EXAMPLE six
The embodiment of the invention also provides a photovoltaic system, which can be understood to comprise components such as an inverter unit, a photovoltaic string, a direct current turn-off device and the like, and further comprise the photovoltaic string turn-off device in the embodiment. Please refer to the above description for the structure of the specific photovoltaic string shutdown device, which is not described in detail in this embodiment.
The photovoltaic system provided by this embodiment includes, in addition to components included in the photovoltaic system itself, a photovoltaic string shutdown device, where the device includes a switching device, an acquisition device, and a shutdown controller, where the switching device is disposed on each photovoltaic string loop and is controlled by the shutdown controller to be turned on and off, the acquisition device acquires an operation signal on each photovoltaic string loop, and then transmits the operation signal to the shutdown controller, the shutdown controller determines whether the operation signal is abnormal by using a predetermined algorithm, that is, whether a preset shutdown condition is satisfied, if so, it indicates that the loop where the operation signal is located is abnormal, the shutdown controller triggers an MPPT unit connected to the shutdown controller to enter a string shutdown mode from a current maximum power tracking mode, and the MPPT unit controls each photovoltaic string to increase a voltage corresponding to a maximum power to an open-circuit voltage, and when the open-circuit voltage is reached, the shutdown controller controls a target switching device on the abnormal loop to be turned off. Obviously, when the open-circuit voltage is reached, the current output by the photovoltaic string approaches zero, which is equivalent to load reduction or even no load, so that the requirements on the switching device are low, and the switching device can be reliably switched off; in addition, after the target switching device is disconnected, the input current, voltage and power of the direct current side of the inverter unit are very small, phenomena such as overheating and electric leakage are not easy to cause, and the direct current turn-off device can be turned off reliably. In conclusion, the device can reduce the requirement on the direct current turn-off device, improve the reliable turn-off of the direct current side of the inverter unit and prevent the photovoltaic system from generating potential hazards such as electrical fire and the like.
The photovoltaic string shutdown device, the photovoltaic string shutdown method and the photovoltaic system provided by the invention are described in detail above. The embodiments are described in a progressive manner in the specification, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. The device disclosed by the embodiment corresponds to the method disclosed by the embodiment, so that the description is simple, and the relevant points can be referred to the method part for description. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention.
It is further noted that, in the present specification, relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
Claims (9)
1. A photovoltaic string turn-off device is characterized by comprising a switching device arranged on each photovoltaic string loop, a collecting device used for collecting operation signals of each photovoltaic string loop, and a turn-off controller connected with the collecting device and an MPPT unit; the switching-off controller is used for triggering the MPPT unit to enter a string switching-off mode from a current maximum power tracking mode when the operation signal meets a preset switching-off condition so that the MPPT unit controls each photovoltaic string loop to increase from a voltage corresponding to the maximum power to an open-circuit voltage, and controls a target switching device to be switched off when the open-circuit voltage is reached;
the acquisition device is specifically a current sensor, a voltage sensor and a temperature sensor, and the corresponding operating signals are specifically the current of the photovoltaic string loop, the voltage of the photovoltaic string loop and the temperature of the photovoltaic string loop.
2. The string shutdown device according to claim 1, wherein the shutdown controller specifically includes an a/D conversion device connected to the collection device, a signal conditioning device connected to the a/D conversion device, and an MCU connected to the signal conditioning device.
3. The pv string shutdown device according to claim 1, wherein the switching device is specifically a relay, contacts of the relay are disposed on the pv string loop, and a coil of the relay is connected to the shutdown controller.
4. The string shutdown device of claim 1, further comprising a diode disposed on each string loop, an anode of the diode being connected to the string, and a cathode of the diode being connected to the MPPT unit.
5. The string shutdown device of claim 1, wherein the shutdown controller is further configured to trigger the MPPT unit to enter the string shutdown mode upon receiving an external shutdown control instruction.
6. The string shutdown device of claim 1, wherein the shutdown controller is further configured to trigger the MPPT unit to enter the maximum power tracking mode after disconnecting the target switching device.
7. A method for shutting down a photovoltaic string, comprising:
collecting operation signals of each photovoltaic group string loop;
acquiring the operation signal, triggering the MPPT unit to enter a string shutdown mode from a current maximum power tracking mode when the operation signal meets a preset shutdown condition so that the MPPT unit controls each photovoltaic string loop to increase from a voltage corresponding to the maximum power to an open-circuit voltage, and controlling a switching device arranged on a target photovoltaic string loop to be disconnected when the open-circuit voltage is reached;
the acquisition device is specifically a current sensor, a voltage sensor and a temperature sensor, and the corresponding operating signals are specifically the current of the photovoltaic string loop, the voltage of the photovoltaic string loop and the temperature of the photovoltaic string loop.
8. The string shutdown method according to claim 7, further comprising, after determining that the operating signal does not satisfy a preset shutdown condition:
judging whether an external turn-off control instruction is received or not;
and if so, triggering the MPPT unit to enter the string shutdown mode.
9. A photovoltaic system comprising the photovoltaic string shutdown device of any one of claims 1 to 6.
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| CN113675892B (en) * | 2021-09-27 | 2024-05-14 | 阳光电源股份有限公司 | Photovoltaic power generation system, control method thereof and power converter |
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