CN111600338A - Photovoltaic system and control method thereof - Google Patents
Photovoltaic system and control method thereof Download PDFInfo
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- CN111600338A CN111600338A CN202010552885.1A CN202010552885A CN111600338A CN 111600338 A CN111600338 A CN 111600338A CN 202010552885 A CN202010552885 A CN 202010552885A CN 111600338 A CN111600338 A CN 111600338A
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- photovoltaic
- string
- converter
- mppt
- bypass device
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/381—Dispersed generators
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
- H02J2300/20—The dispersed energy generation being of renewable origin
- H02J2300/22—The renewable source being solar energy
- H02J2300/24—The renewable source being solar energy of photovoltaic origin
- H02J2300/26—The renewable source being solar energy of photovoltaic origin involving maximum power point tracking control for photovoltaic sources
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/50—Photovoltaic [PV] energy
- Y02E10/56—Power conversion systems, e.g. maximum power point trackers
Abstract
The application discloses a photovoltaic system and a control method thereof, which aim to improve the overall economy of the system. The photovoltaic system comprises a converter with an MPPT function and at least one photovoltaic group string which is connected to the input side of the converter and is provided with a bypass device, wherein the bypass device can bypass partial photovoltaic modules in the photovoltaic group string after being started. The photovoltaic system is used for judging whether the converter needs to operate in a power limiting mode, and if yes, at least one bypass device is started to enable the output power of the converter to meet the power limiting requirement.
Description
Technical Field
The invention relates to the technical field of power electronics, in particular to a photovoltaic system and a control method thereof.
Background
When designing a photovoltaic system, it is necessary to consider how many photovoltaic modules are most suitable for series connection in a photovoltaic string. The design of the photovoltaic string is closely related to a plurality of constraint conditions such as the specification of the photovoltaic module, the specification of the converter, the voltage range of the photovoltaic string required by safety regulations, the environmental temperature of an installation place and the like.
Under the condition that all the constraint conditions allow, the photovoltaic modules in the photovoltaic string are connected in series in the largest number as possible so as to improve the overall economy of the system. However, individual constraints (such as the light intensity at the installation site) vary with time, which results in that the expected value of the number of series-connected photovoltaic modules also varies with time, and if the actual number of series-connected photovoltaic modules is changed correspondingly with the increase and decrease of the expected value, the limited power operation of the converter may not be guaranteed in some extreme cases, as specifically analyzed below:
in a photovoltaic system, a converter with an MPPT (Maximum Power Point Tracking) function meets the requirement of Maximum Power output by Tracking an MPPT working Point of photovoltaic string voltage; when the converter needs limited power operation, the power output is reduced by shifting the string voltage of the photovoltaic string to the right from the MPPT operating point (i.e., boosting the string voltage of the photovoltaic string). However, the space for shifting the string voltage to the right is limited, and cannot exceed the voltage value specified by safety regulations, and as the number of the photovoltaic modules connected in series increases, in an extreme case, the string voltage of the photovoltaic module has shifted to the voltage value specified by safety regulations and the output power of the converter has not been reduced to the required power limit value.
Disclosure of Invention
In view of this, the present invention provides a photovoltaic system and a control method thereof to ensure limited power operation of a converter.
A photovoltaic system, comprising: the photovoltaic module string with the MPPT function is connected to the input side of the converter, at least one photovoltaic module string with a bypass device is arranged, and the bypass device can bypass part of photovoltaic modules in the photovoltaic module string after being started;
the photovoltaic system is used for judging whether the converter needs to operate in a power limiting mode, and if yes, at least one bypass device is started to enable the output power of the converter to meet the power limiting requirement.
Optionally, the photovoltaic system is configured to determine whether the converter needs to operate with limited power, if so, start at least one bypass device, then determine whether the output power of the converter meets the requirement for limited power, and if not, control the photovoltaic string voltage on at least one MPPT loop to move in a direction away from the MPPT working point until the output power of the converter meets the requirement for limited power.
Optionally, in any of the photovoltaic systems disclosed above, the converter includes: the system comprises an inverter and one or a plurality of parallel MPPT controllers connected to the direct current side of the inverter, wherein the input side of each MPPT controller is independently connected with one or a plurality of parallel photovoltaic string groups, and at least one photovoltaic string group on at least one MPPT controller is provided with a bypass device;
or, the converter is a two-stage inverter, the rear stage is an inverter circuit, the front stage is one or multiple parallel MPPT controllers connected to the dc side of the inverter circuit, the input side of each MPPT controller is independently connected to one or multiple parallel photovoltaic string, and at least one photovoltaic string on at least one MPPT controller is provided with a bypass device.
Optionally, in any of the above-disclosed photovoltaic systems, the converter needs to operate with limited power, and the converter includes: the photovoltaic system detects that the total maximum power which can be sent by all photovoltaic strings exceeds the rated power of the converter, or receives a power grid dispatching instruction which requires the converter to operate in a limited power mode.
Optionally, in any of the above-disclosed photovoltaic systems, when the photovoltaic string voltage on at least one MPPT loop is controlled to move in a direction away from the MPPT operating point, the photovoltaic system is specifically configured to control the photovoltaic string voltage on at least one MPPT loop to move rightward from the MPPT operating point.
Optionally, in any of the photovoltaic systems disclosed above, any one of the bypass devices can be independently applied to one photovoltaic string or shared by a plurality of photovoltaic strings.
Optionally, in the last pv system, a bypass device is configured on each pv string.
Optionally, the last photovoltaic system is further configured to perform amplitude limiting and amplitude limitation cancellation on the photovoltaic string voltage by adjusting the on/off of each bypass device, so as to ensure that the photovoltaic string voltage does not exceed a voltage value specified by safety regulations all the time.
Optionally, in any of the photovoltaic systems disclosed above, the bypass device includes a controllable switch S1 and a unidirectional conducting device, and the controllable switch S1 is connected in series with some of the photovoltaic modules in the photovoltaic string and then connected in reverse parallel with the unidirectional conducting device.
Optionally, in any of the photovoltaic systems disclosed above, the bypass device includes a controllable switch S2, and the controllable switch S2 is connected in parallel with a part of the photovoltaic modules in the photovoltaic string.
Optionally, in any of the photovoltaic systems disclosed above, the bypass device includes a controllable switch S3, and the controllable switch S3 is a single-pole double-throw switch; the first throw point of the single-pole double-throw switch is connected to a second throw point through a part of photovoltaic modules in the photovoltaic group string; and the common end of the single-pole double-throw switch is connected with the other photovoltaic module access circuits in the photovoltaic group string where the second throwing point is positioned, and the common end of the single-pole double-throw switch is connected with all the photovoltaic modules in the photovoltaic group string where the first throwing point is positioned.
A photovoltaic system control method, the photovoltaic system comprising: the photovoltaic module string with the MPPT function is connected to the input side of the converter, at least one photovoltaic module string with a bypass device is arranged, and the bypass device can bypass part of photovoltaic modules in the photovoltaic module string after being started;
the photovoltaic system control method comprises the following steps:
judging whether the converter needs to operate in a limited power mode;
if yes, at least one bypass device is started, so that the output power of the converter reaches the power limiting requirement.
A method of controlling a photovoltaic system, the photovoltaic system comprising: the photovoltaic module string with the MPPT function is connected to the input side of the converter, at least one photovoltaic module string with a bypass device is arranged, and the bypass device can bypass part of photovoltaic modules in the photovoltaic module string after being started;
the photovoltaic system control method comprises the following steps:
judging whether the converter needs to operate in a limited power mode;
if yes, starting at least one bypass device, judging whether the output power of the converter meets the power limiting requirement, and if not, controlling the photovoltaic group string voltage on at least one path of MPPT loop to move towards the direction far away from the MPPT working point until the output power of the converter meets the power limiting requirement.
According to the technical scheme, the appropriate number of bypass devices are used for limiting the power according to the required power limiting value, so that the situation that the photovoltaic string voltage right shift space is limited and the voltage value exceeds the safety regulation voltage value when the photovoltaic string voltage shifts from the MPPT working point to the right for limiting the power in the prior art is avoided.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a schematic structural diagram of a photovoltaic system according to an embodiment of the present invention;
FIG. 2 is a schematic structural diagram of another photovoltaic system disclosed in an embodiment of the present invention;
FIG. 3 is a schematic structural diagram of another photovoltaic system disclosed in an embodiment of the present invention;
FIG. 4 is a schematic structural diagram of another photovoltaic system disclosed in an embodiment of the present invention;
FIG. 5 is a circuit topology structure diagram of a bypass device according to an embodiment of the present invention;
FIG. 6 is a circuit topology structure diagram of another bypass apparatus according to the embodiment of the present disclosure;
FIG. 7 is a circuit topology structure diagram of another bypass apparatus according to the embodiment of the present disclosure;
FIG. 8 is a flowchart of a method for controlling a photovoltaic system according to an embodiment of the present disclosure;
fig. 9 is a flowchart of another photovoltaic system control method according to an embodiment of the present disclosure.
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, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1, an embodiment of the present invention discloses a photovoltaic system, including: the photovoltaic power generation system comprises a converter with an MPPT function, and at least one photovoltaic string which is connected to the input side of the converter and is provided with a bypass device; the bypass device is in an opening state and a closing state, after the bypass device is opened, partial photovoltaic modules in the photovoltaic group string where the bypass device is located can be bypassed, and after the bypass device is closed, the bypass of the corresponding photovoltaic modules is removed.
Alternatively, the converter may adopt any one of the following two configurations:
structure 1: the converter includes: the inverter and connect in the dc side of inverter or multichannel MPPT controller that connects in parallel, the input side of every way MPPT controller is converter input side, and the input side of every way MPPT controller inserts one or a plurality of photovoltaic group strings that connect in parallel independently, disposes bypass device on at least one photovoltaic group string on at least one way MPPT controller, for example as shown in figure 1.
Structure 2: the converter is a two-stage inverter, the rear stage is an inverter circuit, the front stage is one or multiple parallel MPPT controllers connected to the direct current side of the inverter circuit, the input side of each MPPT controller is the input side of the converter, the input sides of the MPPT controllers are independently connected to one or multiple parallel photovoltaic string, and at least one photovoltaic string on at least one MPPT controller is provided with a bypass device, for example, as shown in FIG. 2.
In the two structures, the MPPT controller is essentially a DC/DC converter, which detects the voltage of the pv string connected to its input side in real time and tracks the MPPT operating point within the voltage variation range of the pv string. The two structures differ only in that: the MPPT controller in configuration 1 is a peripheral component of the inverter, while the MPPT controller in configuration 2 is a component of the inverter itself.
It should be noted that fig. 1 and fig. 2 are only shown as individual examples of the embodiment of the present invention, and the number of MPPT controllers provided in the photovoltaic system, the number of pv strings connected to each MPPT controller, the number of bypass devices connected to each pv string, and which pv modules in each pv string are provided with bypass devices may be adaptively adjusted according to actual needs of a construction site, and are not limited to fig. 1 and fig. 2.
Alternatively, in any of the above disclosed photovoltaic systems, any one of the bypass devices may be applied to only one photovoltaic string, such as shown in fig. 1 or fig. 2; alternatively, to save costs, at least one bypass device may be shared by a plurality of strings of photovoltaic cells, such as shown in fig. 3.
Further, in any of the above-disclosed photovoltaic systems, a bypass device is disposed on each photovoltaic string, and the bypass device may be used independently or in common with other photovoltaic strings, for example, as shown in fig. 4.
Alternatively, in any of the photovoltaic systems disclosed above, the bypass device may employ a circuit topology as shown in fig. 5, 6, or 7.
The bypass device shown in fig. 5 comprises a controllable switch S1 and a unidirectional conducting device (for example, a diode D1), wherein the controllable switch S1 is connected in series with a part of the photovoltaic modules in the photovoltaic string and then connected in reverse parallel with the unidirectional conducting device. The photovoltaic modules are connected into the photovoltaic string by closing the controllable switch S1 and are separated out of the photovoltaic string by opening the controllable switch S1.
The bypass device shown in fig. 6 comprises a controllable switch S2, said controllable switch S2 being connected in parallel with a part of the photovoltaic modules in the string of photovoltaic strings. The partial photovoltaic modules are short-circuited by closing the controllable switch S2 to strip out the string and are switched into the string by opening the controllable switch S2.
The bypass device of fig. 7 comprises a controllable switch S3, the controllable switch S3 being a single pole double throw switch; the first throw point of the single-pole double-throw switch is connected to a second throw point through a part of photovoltaic modules in the photovoltaic group string; and the common end of the single-pole double-throw switch is connected with the other photovoltaic module access circuits in the photovoltaic group string where the second throwing point is positioned, and the common end of the single-pole double-throw switch is connected with all the photovoltaic modules in the photovoltaic group string where the first throwing point is positioned.
The controllable switch in fig. 5, 6 or 7 is, for example, a mechanical switch, such as a relay, or a semiconductor switch.
Wherein any of the above disclosed photovoltaic systems further comprises a control unit; the control unit is used for judging whether the converter needs to operate in a limited power mode, if so, at least one bypass device is started, and the number of the started bypass devices depends on the limited power value, so that the output power of the converter meets the requirement of the limited power.
Specifically, when the converter needs to operate with limited power (for example, when the lighting is relatively strong, the maximum power which can be sent by all the photovoltaic string strings together exceeds the rated power of the converter, the converter needs to operate with limited power, and for example, the converter receives a power grid scheduling instruction and requires the converter to operate with limited power), the output power of the photovoltaic string is generally reduced by shifting the voltage of the photovoltaic string from the MPPT operating point to the right (namely, increasing the voltage of the photovoltaic string), but the space for shifting the voltage of the photovoltaic string to the right is limited, and as the number of the photovoltaic components connected in series increases, the voltage of the photovoltaic string can exceed the voltage value specified by the safety regulations under extreme conditions, at this time, according to the required value of the limited power, an appropriate number of bypass devices are used for limiting the power, so that the problem that the space for shifting the voltage of the photovoltaic string to the right when the voltage of the photovoltaic string is shifted from the MPPT operating point to the right for limiting the, the voltage value may exceed the safety regulation.
In addition, considering the way of enabling the bypass device to reduce the output power of the converter, only abrupt power step change can be realized, and smooth stepless power regulation cannot be realized, so that the power regulation precision is low. In view of the above, the embodiment of the present invention further discloses another control unit, where the control unit is configured to determine whether the converter needs to operate with limited power, if so, start at least one bypass device, then determine whether the output power of the converter meets the power limit requirement, and if not, control the photovoltaic string voltage on at least one MPPT loop to move in a direction away from the MPPT operating point until the output power of the converter meets the power limit requirement.
The control unit limits power by starting a combined mode of a bypass device and MPPT operating point right shift, namely: firstly, starting a plurality of bypass devices to roughly adjust the output power of the converter, and then controlling the photovoltaic string voltage on at least one MPPT loop (one MPPT controller corresponds to one MPPT loop) to finely adjust the output power of the converter from the right side of the MPPT working point so as to meet the requirement of high-precision power limit; and at the moment, the space for moving the voltage of the photovoltaic string is small, so that the voltage value cannot exceed the voltage value specified by safety regulations. Of course, if the output power of the converter after coarse adjustment just meets the requirement of high-precision power limit, the MPPT operating point does not need to be moved to the right.
Although the photovoltaic string voltage can also reduce power when moving from the MPPT operating point to the left, the power change within the unit moving distance is not obvious, so when the power is limited by moving the MPPT operating point alone in the prior art, the MPPT operating point is generally moved to the right instead of the left. However, considering that the MPPT controller is only used to fine-tune the converter output power without greatly adjusting the converter output power in the combined mode of enabling the bypass device + right shift of the MPPT operating point, the MPPT controller may shift the pv string voltage from the MPPT operating point to the left to improve the power adjustment accuracy when the adjustment space allows. That is to say, in the embodiment of the present invention, at least one MPPT controller controls the photovoltaic string voltage to move in a direction away from the MPPT operating point to fine-tune the converter output power, and the moving direction is not limited, and is recommended to be a right shift.
All operations of the photovoltaic system are required to be carried out under the condition that the voltage of the photovoltaic string is not more than the voltage value specified by safety regulations. When designing a photovoltaic system, it is necessary to consider how many photovoltaic modules are connected in series in a photovoltaic string to be most suitable, and the design of the photovoltaic string is closely related to a plurality of constraint conditions such as the specification of the photovoltaic modules, the specification of a converter, the voltage range of the photovoltaic string required by safety regulations, the environmental temperature of an installation place, the illumination intensity of the installation place and the like. Under the condition that the voltage of the photovoltaic string is not more than the voltage specified by safety regulations, the photovoltaic modules in the photovoltaic string are connected in series in the largest quantity as possible, so that the overall economy of the system is improved. However, the constraints such as the illumination intensity of the installation site and the ambient temperature of the installation site are time-varying, which results in that the maximum allowable value of the number of series-connected photovoltaic modules is also time-varying. In order to change the actual serial number of the photovoltaic modules at any time conveniently, the embodiment of the invention can also change the actual serial number of the photovoltaic modules by adjusting the on-off of each bypass device, thereby carrying out amplitude limiting and amplitude limitation relieving on the voltage of the photovoltaic string and ensuring that the voltage of the photovoltaic string does not exceed the voltage value specified by safety regulations all the time.
On the basis, in the case that the maximum allowable values of the serial numbers of the photovoltaic modules in the same photovoltaic string at different times are different, a larger value (namely, any value except the minimum value) of the maximum allowable value within one year time rather than the minimum value can be selected as the serial number of the photovoltaic modules which are designed in the photovoltaic string in a unified way, and the actual serial number of the photovoltaic modules (namely, the number of the photovoltaic modules which are really used for power generation in the photovoltaic string) at different times is adjusted by turning on/off the bypass device on the photovoltaic string, so that the overall economy of the system is improved under the condition that the voltage of the photovoltaic string is not more than the voltage value defined by safety regulations.
Thereby the control unit carries out amplitude limit and degression limit to photovoltaic group string voltage through the switching of adjusting each bypass device, guarantees that photovoltaic group string voltage is no longer than the voltage value of ann's rule regulation all the time, specifically does: for each photovoltaic string in the photovoltaic system, judging the magnitude relation between the voltage V0 of the photovoltaic string and a first preset voltage value V1 and a second preset voltage value V2 in real time, wherein the second preset voltage value V2 is smaller than the first preset voltage value V1; if the photovoltaic string voltage V0 is larger than a first preset voltage value V1, a plurality of bypass devices are started, and if the photovoltaic string voltage V0 is smaller than a second preset voltage value V2, all the opened bypass devices are closed, so that the photovoltaic string voltage V0 is basically kept at a level that V2 is larger than or equal to V0 is larger than or equal to V1.
For example, in the morning, the light is slowly and strongly illuminated, the voltage of each photovoltaic module gradually rises, so that the voltage V0 of the photovoltaic string gradually rises, when the voltage V0 exceeds the first preset voltage value V1, the voltage of the photovoltaic modules in the photovoltaic string is limited by opening a plurality of bypass devices, so that the voltage V0 of the photovoltaic string is limited, and the voltage V0 of the photovoltaic string cannot exceed the voltage value defined by safety regulations under the condition that the voltage of the photovoltaic modules continues to rise (for example, a household in China requires that the voltage of a dc side design cannot exceed 1000V in a distributed photovoltaic system). After the converter is opened, the MPPT controller carries out MPPT control to the photovoltaic group string, and photovoltaic group string voltage V0 descends gradually, when V0 descends to and is less than second preset voltage value V2, removes the amplitude limit to photovoltaic group string voltage V0, and photovoltaic group string voltage V0 can not exceed the voltage value of ann's rule definition this moment, and so still improved the whole economic nature of system owing to improved the photovoltaic module series quantity this moment.
In any of the embodiments disclosed above, the opening and closing of the bypass device is controlled by the control unit in real time by communication. The Communication method may be a PLC (Power Line Communication) method, a wired Communication method, or a wireless Communication method. The wired communication mode is, for example, CAN bus communication or optical fiber communication, and the wireless communication mode is, for example, 3G, 4G, Wi-Fi or ZigBee (ZigBee) or other wireless communication modes.
Alternatively, the control unit may be a separate controller. Or, in order to save hardware cost, the functions of the control unit can be simultaneously integrated in all MPPT controllers, and each MPPT controller only controls the on and off of the bypass device on the input side.
Corresponding to the system embodiment, the embodiment of the invention also discloses a photovoltaic system control method. The photovoltaic system includes: the photovoltaic string system comprises a converter with an MPPT function and at least one photovoltaic string which is connected to the input side of the converter and is provided with a bypass device, wherein the bypass device can bypass partial photovoltaic modules in the photovoltaic string after being started.
As shown in fig. 8, the photovoltaic system control method includes:
step S01: judging whether the converter needs to operate in a limited power mode; if yes, the process proceeds to step S02, otherwise, the process returns to step S01.
Step S02: at least one bypass device is turned on to make the converter output power reach the limit power requirement, and then the step S01 is returned to.
Optionally, as shown in fig. 9, an embodiment of the present invention further discloses another photovoltaic system control method, including:
step S11: judging whether the converter needs to operate in a limited power mode; if yes, the process proceeds to step S12, otherwise, the process returns to step S11.
Step S12: at least one bypass device is turned on to bring the converter output power to the limit power requirement.
Step S13: and judging whether the output power of the converter meets the power limit requirement, if not, entering the step S14, and if so, returning to the step S11.
Step S14: and controlling the voltage of the photovoltaic string on at least one MPPT loop to move towards a direction far away from the MPPT working point, and then returning to the step S13.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. The method disclosed by the embodiment corresponds to the system disclosed by the embodiment, so that the description is simple, and the relevant points can be referred to the system part for description.
The terms "first," "second," and the like in the description and in the claims, and in the drawings, are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. 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, the use of the verb "comprise a" to define an element does not exclude the presence of another, identical element in a process, method, article, or apparatus that comprises the element.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the embodiments. Thus, the present embodiments are not intended to be limited to the embodiments shown herein but are to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (13)
1. A photovoltaic system, comprising: the photovoltaic module string with the MPPT function is connected to the input side of the converter, at least one photovoltaic module string with a bypass device is arranged, and the bypass device can bypass part of photovoltaic modules in the photovoltaic module string after being started;
the photovoltaic system is used for judging whether the converter needs to operate in a power limiting mode, and if yes, at least one bypass device is started to enable the output power of the converter to meet the power limiting requirement.
2. The photovoltaic system of claim 1, wherein the photovoltaic system is configured to determine whether the converter needs power limiting operation, if so, start at least one bypass device, then determine whether the converter output power meets the power limiting requirement, and if not, control the at least one MPPT loop to move the pv string voltage in a direction away from the MPPT operating point until the converter output power meets the power limiting requirement.
3. The photovoltaic system of claim 1 or 2, wherein:
the converter includes: the system comprises an inverter and one or a plurality of parallel MPPT controllers connected to the direct current side of the inverter, wherein the input side of each MPPT controller is independently connected with one or a plurality of parallel photovoltaic string groups, and at least one photovoltaic string group on at least one MPPT controller is provided with a bypass device;
or, the converter is a two-stage inverter, the rear stage is an inverter circuit, the front stage is one or multiple parallel MPPT controllers connected to the dc side of the inverter circuit, the input side of each MPPT controller is independently connected to one or multiple parallel photovoltaic string, and at least one photovoltaic string on at least one MPPT controller is provided with a bypass device.
4. The photovoltaic system of claim 1 or 2, wherein the converter requires limited power operation, comprising: the photovoltaic system detects that the total maximum power which can be sent by all photovoltaic strings exceeds the rated power of the converter, or receives a power grid dispatching instruction which requires the converter to operate in a limited power mode.
5. The photovoltaic system of claim 1 or 2, wherein when controlling the string voltage on at least one MPPT loop to move in a direction away from the MPPT operating point, the photovoltaic system is specifically configured to control the string voltage on at least one MPPT loop to move rightward from the MPPT operating point.
6. The pv system of claim 1 or claim 2 wherein any one of the bypass devices is independently applicable to a pv string or is shared by a plurality of pv strings.
7. The pv system of claim 6 wherein a bypass device is provided on each pv string.
8. The photovoltaic system of claim 7, further configured to clip and clip the photovoltaic string voltage by adjusting the on/off of each bypass device, so as to ensure that the photovoltaic string voltage does not exceed a voltage value specified by safety regulations at all times.
9. The photovoltaic system according to claim 1 or 2, wherein the bypass device comprises a controllable switch S1 and a unidirectional conducting device, and the controllable switch S1 is connected in series with a part of the photovoltaic modules in the photovoltaic string and then connected in inverse parallel with the unidirectional conducting device.
10. The photovoltaic system according to claim 1 or 2, characterized in that the bypass device comprises a controllable switch S2, the controllable switch S2 being connected in parallel with a part of the photovoltaic modules in the string of photovoltaic strings.
11. The photovoltaic system of claim 1 or 2, wherein the bypass device comprises a controllable switch S3, the controllable switch S3 being a single pole double throw switch; the first throw point of the single-pole double-throw switch is connected to a second throw point through a part of photovoltaic modules in the photovoltaic group string; and the common end of the single-pole double-throw switch is connected with the other photovoltaic module access circuits in the photovoltaic group string where the second throwing point is positioned, and the common end of the single-pole double-throw switch is connected with all the photovoltaic modules in the photovoltaic group string where the first throwing point is positioned.
12. A photovoltaic system control method, characterized in that the photovoltaic system comprises: the photovoltaic module string with the MPPT function is connected to the input side of the converter, at least one photovoltaic module string with a bypass device is arranged, and the bypass device can bypass part of photovoltaic modules in the photovoltaic module string after being started;
the photovoltaic system control method comprises the following steps:
judging whether the converter needs to operate in a limited power mode;
if yes, at least one bypass device is started, so that the output power of the converter reaches the power limiting requirement.
13. A photovoltaic system control method, characterized in that the photovoltaic system comprises: the photovoltaic module string with the MPPT function is connected to the input side of the converter, at least one photovoltaic module string with a bypass device is arranged, and the bypass device can bypass part of photovoltaic modules in the photovoltaic module string after being started;
the photovoltaic system control method comprises the following steps:
judging whether the converter needs to operate in a limited power mode;
if yes, starting at least one bypass device, judging whether the output power of the converter meets the power limiting requirement, and if not, controlling the photovoltaic group string voltage on at least one path of MPPT loop to move towards the direction far away from the MPPT working point until the output power of the converter meets the power limiting requirement.
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| CN112994107A (en) * | 2021-04-01 | 2021-06-18 | 华为技术有限公司 | Method, device and system for controlling power supply system |
| WO2021253734A1 (en) * | 2020-06-17 | 2021-12-23 | 阳光电源股份有限公司 | Photovoltaic system and control method therefor |
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| CN116742716A (en) * | 2023-06-13 | 2023-09-12 | 安徽华晟新能源科技有限公司 | Photovoltaic power station output power adjusting method and device and computer equipment |
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