CN107658900B - Photovoltaic grid-connected system - Google Patents
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- CN107658900B CN107658900B CN201710951923.9A CN201710951923A CN107658900B CN 107658900 B CN107658900 B CN 107658900B CN 201710951923 A CN201710951923 A CN 201710951923A CN 107658900 B CN107658900 B CN 107658900B
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- 230000001360 synchronised effect Effects 0.000 description 4
- 238000010586 diagram Methods 0.000 description 3
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- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
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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
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- 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 invention discloses a photovoltaic grid-connected system. The system comprises: a photovoltaic power generation device for outputting direct current power; the bidirectional converter is connected between the photovoltaic power generation equipment and the alternating current power grid; the inverter is connected between the photovoltaic power generation equipment and the alternating current load; the first detection equipment is arranged between the photovoltaic power generation equipment and the bidirectional converter; the second detection equipment is arranged between the alternating current power grid and the bidirectional converter; a third detection device provided between the ac load and the inverter; the MPPT controller, MPPT controller's input end connection first check out test set, second check out test set and third check out test set, MPPT controller's output end connection bidirectional current converter and dc-to-ac converter. The invention solves the technical problem that the MPPT design of the existing photovoltaic power generation system is not suitable for a photovoltaic grid-connected system integrating power generation and power utilization.
Description
Technical Field
The invention relates to the field of power transmission, in particular to a photovoltaic grid-connected system.
Background
Solar energy is widely concerned by people as a clean and environment-friendly energy source, and is widely applied to various occasions for more than 20 years. Solar photovoltaic power generation is an important form of solar energy utilization, is a power generation form of converting light energy into electric energy by adopting a photovoltaic module, and is one of power generation technologies with the greatest development prospect probably along with the continuous progress of the technology.
In a photovoltaic power generation system, the utilization rate of a photovoltaic module is affected by factors such as irradiance, load, and stability of the use environment, in addition to being related to the internal characteristics of the photovoltaic cell. Under different ambient conditions, the photovoltaic modules may operate at different and unique maximum power points. Therefore, the mppt (maximum Power Point tracking) is an important technology for converting light energy into electric energy to the maximum.
The existing photovoltaic power generation system completes MPPT control mainly by performing loop design between the output of a photovoltaic module and the current and voltage of a power grid so as to realize synchronous performance indexes of light energy electric energy and the power grid and the like. Therefore, the current photovoltaic power generation system mainly plays a role in power generation, mainly aims at converting light energy into electric energy synchronous with a power grid to the maximum extent, and can be approximately considered as a power grid system; the power consumption of the rear-end load is uniformly scheduled by the power grid after the electric energy is converted by solar energy and is converged into the power grid. Therefore, the key of MPPT control only needs to ensure the synchronization of the photovoltaic electric energy and the power grid.
In the photovoltaic system integrating power generation and utilization, a load cannot be simply approximated to a power grid, a rear-end load needs to be considered and directly controlled, and a working mode of the photovoltaic system is no longer a pure power generation mode, wherein the photovoltaic system needs to be switched in real time in various modes, however, the stability of intermediate direct-current bus voltage and the control target of power factor sine wave current cannot be guaranteed by maintaining the result of the existing MPPT parameter control, that is, the existing MPPT design of the photovoltaic power generation system is not suitable for the photovoltaic grid-connected system integrating power generation and utilization. No effective solution to this problem has been proposed.
Disclosure of Invention
The embodiment of the invention provides a photovoltaic grid-connected system, which at least solves the technical problem that the MPPT design of the existing photovoltaic power generation system is not suitable for a power generation and utilization integrated photovoltaic grid-connected system.
According to an aspect of an embodiment of the present invention, there is provided a photovoltaic grid-connected system, including: a photovoltaic power generation device for outputting direct current power; the bidirectional converter is connected between the photovoltaic power generation equipment and an alternating current power grid, wherein the photovoltaic power generation equipment corresponds to a direct current end of the bidirectional converter, and the alternating current power grid corresponds to an alternating current end of the bidirectional converter; an inverter connected between the photovoltaic power generation device and an ac load, wherein the photovoltaic power generation device corresponds to a dc terminal of the inverter, and the ac load corresponds to an ac terminal of the inverter; the first detection equipment is arranged between the photovoltaic power generation equipment and the bidirectional converter and at least used for detecting output parameters of the photovoltaic power generation equipment; the second detection equipment is arranged between the alternating current power grid and the bidirectional converter and at least used for detecting the synchronous parameters of the alternating current power grid; third detection means, provided between the ac load and the inverter, for detecting at least a matching parameter of the ac load; an MPPT controller having an input terminal connected to the first detecting device, the second detecting device, and the third detecting device, and an output terminal connected to the bidirectional converter and the inverter, for controlling the bidirectional converter and/or the inverter according to at least one of the following parameters: the output parameter, the synchronization parameter, and the matching parameter.
Preferably, the MPPT controller is configured to switch to a control mode corresponding to a connection relationship among a plurality of control modes according to the connection relationship among the ac grid, the ac load, and the photovoltaic power generation facility.
Preferably, the above-mentioned photovoltaic grid-connected system further includes: and a switching device connected between the ac grid, the ac load, and the photovoltaic power generation facility, wherein when the switching device is in any one of a plurality of states, the connection relationship is switched to a connection relationship corresponding to the any one of the states.
Preferably, when the switching device is in a first state of the plurality of states, the photovoltaic power generation apparatus is disconnected from the ac grid and the ac load, and the MPPT controller switches to a no-load mode of the plurality of control modes; and/or, when the switching device is in a second state of the plurality of states, the ac load is disconnected from the photovoltaic power generation equipment and the ac grid, and the MPPT controller switches to a power generation mode of the plurality of control modes to control the bidirectional converter according to the output parameter and the synchronization parameter; and/or, when the switching device is in a third state of the plurality of states, the ac grid is disconnected from the photovoltaic power generation equipment and the ac load, and the MPPT controller switches to a load mode of the plurality of control modes to control the inverter according to the output parameter and the matching parameter; and/or, when the switching device is in a fourth state of the plurality of states, the photovoltaic power generation apparatus is connected to the ac grid through the bidirectional converter and is connected to the ac load through the inverter, and the MPPT controller switches to a load power generation mode or a load power utilization mode among the plurality of control modes, wherein in the load power generation mode, the MPPT controller is configured to control the bidirectional converter and/or the inverter based on the output parameter, the synchronization parameter, and the matching parameter, and/or in the load power utilization mode, the MPPT controller is configured to control the bidirectional converter and/or the inverter based on the output parameter and the matching parameter.
Preferably, the switching device includes at least one of: a first switching device connected between the photovoltaic power generation equipment and a direct current bus, wherein the direct current bus is a transmission line between the bidirectional converter and the inverter; a second switching device connected between the photovoltaic power generation apparatus and the ac power grid, the second switching device being provided on the dc bus; and a third switching device connected between the photovoltaic power generation equipment and the ac load, and the third switching device is disposed on the dc bus.
Preferably, the above-mentioned photovoltaic grid-connected system further includes: and a mode controller connected to the switching device and the MPPT controller, the mode controller controlling the switching device to switch between the plurality of states and controlling the MPPT controller to switch to a control mode corresponding to the connection relationship.
Preferably, the mode controller is configured to control the switching device according to the detected capacity of the photovoltaic power generation apparatus, the detected capacity of the ac power grid, and the detected capacity of the ac load.
Preferably, the above-mentioned photovoltaic grid-connected system further includes: and a fourth detecting device disposed on a dc bus, the dc bus being a transmission line between the bidirectional converter and the inverter, the fourth detecting device being connected to the input end, wherein the MPPT controller is configured to control the bidirectional converter and/or the inverter according to the output parameter, and/or the synchronization parameter, and/or the matching parameter, and a voltage and/or a current detected by the fourth detecting device at a corresponding detection point.
Preferably, the MPPT controller is configured to control the bidirectional converter and/or the inverter by a signal of one of: voltage signal, current signal, pulse width modulation signal.
Preferably, the photovoltaic power generation apparatus includes: the photovoltaic cell, the confluence unit and the power distribution unit; and/or, the AC load comprises an air conditioner; and/or the transmission line connected between the alternating current network and the bidirectional converter is a three-phase power transmission line or a single-phase power transmission line; and/or the transmission line connected between the alternating current load and the inverter is a three-phase power transmission line or a single-phase power transmission line.
Firstly, in the embodiment of the present invention, a new architecture of a power generation and utilization integrated power supply system is provided, a photovoltaic grid-connected system applied to the architecture may include a bidirectional converter and an inverter sequentially connected between an ac power grid and an ac load, and a photovoltaic power generation device connected between the bidirectional converter and the inverter, wherein the photovoltaic power generation device may transmit electric energy to the power grid on one side and transmit electric energy to the ac load on the other side, the ac power grid may draw electric energy from the photovoltaic power generation device on one side and may transmit electric energy to the ac load on the other side, so as to form a power generation and utilization integrated system, and since the photovoltaic power generation device may directly feed energy to the ac load, the utilization rate of the electric energy generated by the photovoltaic power generation and utilization integrated system may be improved.
Further, in the embodiment of the present invention, an input end of the MPPT controller may be connected to the first detection device, the second detection device, and the third detection device respectively corresponding to the photovoltaic power generation device, the ac grid, and the ac load, so as to obtain related parameters such as voltage, current, power, and the like fed back at the corresponding detection points, so that the MPPT controller may implement effective control of the bidirectional inverter and/or the inverter according to an output of one or more of the detection devices, that is, one or more of the related parameters respectively collected at the photovoltaic power generation device side, the ac grid side, and the ac load side, thereby achieving a better power supply efficiency, and solving a technical problem that the MPPT design of the existing photovoltaic power generation system is not suitable for the photovoltaic grid-connected system with the electricity generation and utilization integrated.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the invention without limiting the invention. In the drawings:
fig. 1 is a schematic diagram of an alternative photovoltaic grid-connected system according to an embodiment of the invention;
FIG. 2 is a schematic diagram of an MPPT control scheme according to the prior art;
fig. 3 is a schematic diagram of another alternative photovoltaic grid-connected system according to an embodiment of the invention.
Detailed Description
The invention will be described in detail hereinafter with reference to the accompanying drawings in conjunction with embodiments. It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict.
Example 1
According to an embodiment of the present invention, there is provided a photovoltaic grid-connected system, as shown in fig. 1, the apparatus includes:
1) a photovoltaic power generation device 102 for outputting direct-current power;
2) the bidirectional converter 104 is connected between the photovoltaic power generation equipment 102 and the alternating current power grid 106, wherein the photovoltaic power generation equipment 102 corresponds to the direct current end of the bidirectional converter 104, and the alternating current power grid 106 corresponds to the alternating current end of the bidirectional converter 104;
3) the inverter 108 is connected between the photovoltaic power generation equipment 102 and the alternating current load 110, wherein the photovoltaic power generation equipment 102 corresponds to the direct current end of the inverter 108, and the alternating current load 110 corresponds to the alternating current end of the inverter 108;
4) the first detection device 112 is arranged between the photovoltaic power generation device 102 and the bidirectional converter 104 and is at least used for detecting output parameters of the photovoltaic power generation device 102;
5) a second detection device 114, arranged between the ac power grid 106 and the bidirectional converter 104, for detecting at least a synchronization parameter of the ac power grid 106;
6) a third detection device 116, disposed between the ac load 110 and the inverter 108, for detecting at least a matching parameter of the ac load 110;
7) an MPPT controller 118, an input end of the MPPT controller 118 is connected to the first detecting device 112, the second detecting device 114 and the third detecting device 116, and an output end of the MPPT controller 118 is connected to the bidirectional converter 104 and the inverter 108, for controlling the bidirectional converter 104 and/or the inverter 108 according to the output parameter, and/or the synchronization parameter, and/or the matching parameter.
It should be clear that one of the problems to be solved by the technical solution of the present invention is to provide a grid-connected system to implement grid connection of the photovoltaic power generation device 102 to the ac power grid 106, that is, the electric energy provided by the photovoltaic power generation device 102 can be effectively collected into the ac power grid 106, and the ac power grid 106 can effectively schedule the electric energy, so as to improve the power supply capacity of the ac power grid 106.
In order to solve the above problem, according to the photovoltaic grid-connected system provided by the embodiment of the present invention, unlike the inverter connected between the photovoltaic power generation equipment 102 and the ac power grid 106 generally adopted in the prior art, in the embodiment of the present invention, the bidirectional converter 104 may be connected between the photovoltaic power generation equipment 102 and the ac power grid 106, so that the supply of the electric energy to the power grid may be realized through the bidirectional converter 104, specifically, the supply power may be represented as an increase, wherein the function of this alternative will be described in detail in the following embodiments.
Specifically, in the embodiment of the present invention, the photovoltaic power generation apparatus 102 may generally include a photovoltaic cell, a junction unit, and a power distribution unit, where the photovoltaic cell is used to directly convert solar energy into electric energy, for example, a commonly-used silicon photovoltaic cell may be used, the junction unit may collect electric energy generated by the photovoltaic cell array, for example, a commonly-used junction box may be used, and the power distribution unit is used for dc power distribution, or a commonly-used power distribution cabinet may also be used, but the present invention is not limited thereto.
Further, in order to synchronize the ac power provided by the photovoltaic power generation device 102 through the bidirectional converter 104 with the power of the ac power grid 106 and achieve a better output power point of the photovoltaic power generation device 102, in some embodiments of the present invention, the MPPT controller 118 may be used to modulate the power fed back from the photovoltaic power generation device 102 to the ac power grid 106 in a manner of controlling the bidirectional converter 104, so as to improve the grid-connection efficiency.
In the embodiment of the present invention, the input parameter of the MPPT controller 118 may be the output from the first detection device 112 and the second detection device 114, wherein the output of the first detection device 112 may be an electrical parameter detected by the first detection device 112 at a detection point thereof, that is, near the output end of the photovoltaic power generation device 102, which is denoted as an output parameter, and the output of the second detection device 114 may be an electrical parameter detected by the second detection device 114 at a detection point thereof, that is, near the input end of the ac power grid 106, which at least includes a synchronization parameter, which is used for synchronization between the photovoltaic power transmission and the power grid to achieve better energy feeding efficiency, wherein the electrical parameter may be either a voltage or a current, or a parameter related to the power provided or drawn by the photovoltaic power generation device 102 and/or the ac power grid 106, such as the power obtained by the detection device based on the electrical parameter, correspondingly, the first detection device 112 and the second detection device 114 may include a voltage sensor and/or a current sensor, etc., wherein, in particular, the electrical parameters fed back by the detection devices may be represented by electrical signals output by the detection devices, and the MPPT controller 118 may collect the electrical parameters through input terminals connected to the detection devices. More specifically, in the embodiment of the present invention, the input terminal of the MPPT controller 118 may be a terminal block including at least three connection terminals, wherein the three connection terminals may be respectively connected to the first detecting device 112, the second detecting device 114 and the third detecting device 116, the third detecting device 116 is disposed at the ac load 110, and the specific operation manner thereof is similar to that of the first detecting device 112 and the second detecting device 114, and the present invention will not be described herein in detail.
It should be noted that, the present invention does not limit any internal structure of the three detecting devices and the specific connection manner in the line thereof, for example, in the embodiment of the present invention, the current sensors in the detecting devices may be electromagnetic current transformers connected in series in the detecting line, or hall sensors, and the like, where the specific implementation manner of the detecting devices does not affect the implementation of the technical solution of the present invention and the implementation of the technical effect thereof, and should not be construed as limiting the present invention.
Similarly, in the embodiment of the present invention, a specific implementation manner of the MPPT controller 118 may also adopt a circuit or a device similar to those in the prior art for implementing the above-mentioned control function, for example, a typical three-loop control structure for MPPT control may be as shown in fig. 2, wherein input parameters of the MPPT controller 118 may be a voltage and a current collected at the side of the photovoltaic power generation device 102 and a voltage and/or a current collected at the side of the AC power grid 106 as a synchronization signal, and output parameters thereof may be pulse width modulation signals for controlling a DC/DC converter and a DC/AC converter in the inverter 202, so that the MPPT may adjust the pulse width modulation signals, such as the duty ratio thereof, according to the synchronization condition, thereby implementing adjustment of the AC output generated by the inverter 202. Of course, the above is only an example, and the present invention is not limited to this, for example, in some embodiments of the present invention, the output of the MPPT controller 118 may also not be limited to the form of pulses, for example, the control of the output of the inverter 202 connected to the photovoltaic power generation apparatus 102 may be realized by analog signals such as voltage signals or current signals, that is, in embodiments of the present invention, the MPPT controller 118 controls the bidirectional converter 104 and/or the inverter 108 by a signal of one of the following: voltage signal, current signal, pulse width modulation signal. Furthermore, the MPPT controller 118 may also track the maximum power point in conjunction with control logic written into the controller chip, such as dynamic tracking of the maximum power point through a sweep of the amplitude and/or phase of the output voltage and/or current, etc. It should be understood that the above-described embodiments of the present invention are all considered to be within the scope of the present invention.
Through the technical solutions described in the above embodiments, effective grid connection from the photovoltaic power generation device 102 to the ac power grid 106 can be achieved, wherein a framework provided by the above solutions similar to the prior art can be summarized as that the photovoltaic power generation device 102 supplies power to the ac power grid 106, and then the ac power grid 106 after capacity expansion is connected to each ac load 110. In a conventional power generation system, the framework can achieve a relatively ideal power supply efficiency, however, in a system integrating power generation and power utilization, since the load of the photovoltaic power generation device 102 cannot be simply approximated to a power grid, and the influence of a rear-end load on the power supply efficiency needs to be considered, the conventional MPPT design cannot meet the design requirement of effectively controlling a converter in the system integrating power generation and power utilization with more complicated influence factors to achieve a more optimal power supply efficiency.
In view of this problem, in the embodiment of the present invention, a new architecture is firstly proposed, and specifically, the photovoltaic grid-connected system may further include an ac load 110, wherein an inverter 108 may be connected between the photovoltaic power generation device 102 and the ac load 110, so that the photovoltaic power generation device 102 may deliver electric energy to the grid on one side and deliver electric energy to the ac load 110 on the other side, which forms a system integrating power generation and power utilization, and since the photovoltaic power generation device 102 may directly feed energy to the ac load 110, direct drive utilization rate of the generated electric energy may be improved. Further, in the embodiment of the present invention, the input end of the MPPT controller 118 may be further connected to a third detection device 116 disposed at the access end of the ac load 110, so as to collect electrical parameters such as voltage, current, and power related to the ac load 110, which are used for reflecting the matching condition of the ac load 110 with the photovoltaic power supply device and the ac grid 106, and the electrical parameters are recorded as matching parameters, so that the MPPT controller 118 may implement effective control on the bidirectional converter 104 and/or the inverter according to the output of one or more of the detection devices, that is, one or more of the electrical parameters collected on the photovoltaic power generation device 102 side, the ac grid 106 side, and the ac load 110 side, thereby achieving better power supply efficiency.
On the basis of the above description, in order to further achieve more effective control of the power generation and utilization integrated system, the above-mentioned photovoltaic grid-connected system provided according to the embodiment of the present invention may further include a switching device, and further, the switching device may be used to achieve switching between different application modes of the power generation and utilization integrated system, so as to achieve the purpose of flexibly matching between the capacity of the photovoltaic power generation device 102, the capacity of the ac power grid 106, and the capacity of the ac load 110, where the switching device may be connected between the ac power grid 106, the ac load 110, and the photovoltaic power generation device 102, and when the switching device is in any one of a plurality of states, the connection relationship between the ac power grid 106, the ac load 110, and the photovoltaic power generation device 102 may be switched to a connection relationship corresponding to any one of the states. On the other hand, the MPPT controller 118 may also cooperate with the switching device to execute a control strategy corresponding to the application mode, so as to achieve better power supply efficiency, that is, in the embodiment of the present invention, the MPPT controller 118 may also be configured to switch to a control mode corresponding to a connection relationship among the plurality of control modes according to the connection relationship among the ac power grid 106, the ac load 110, and the photovoltaic power generation apparatus 102. For example, as a possible implementation manner, in an embodiment of the present invention, the photovoltaic grid-connected system may include:
1) a switching device connected between the ac grid 106, the ac load 110, and the photovoltaic power generation apparatus 102;
wherein the content of the first and second substances,
when the switching device is in a first state of the plurality of states, the photovoltaic power generation apparatus 102 is disconnected from the ac power grid 106 and the ac load 110, and the MPPT controller 118 may switch to an idle mode of the plurality of control modes; and/or the presence of a gas in the gas,
when the switching device is in a second state of the plurality of states, the ac load 110 is disconnected from the photovoltaic power generation apparatus 102 and the ac power grid 106, and the MPPT controller 118 may switch to a power generation mode of the plurality of control modes for controlling the bidirectional converter 104 according to the output parameters and the synchronization parameters; and/or the presence of a gas in the gas,
when the switching device is in a third state of the plurality of states, the ac grid 106 is disconnected from the photovoltaic power plant 102 and the ac load 110, and the MPPT controller 118 may switch to a load mode of the plurality of control modes for controlling the inverter 108 according to the output parameters and the matching parameters; and/or the presence of a gas in the gas,
when the switching device is in a fourth state of the plurality of states, the photovoltaic power generation apparatus 102 is connected to the ac grid 106 via the bidirectional converter 104 and to the ac load 110 via the inverter 108, the MPPT controller 118 may switch to a load power generation mode or a load power utilization mode of a plurality of control modes, wherein,
in the load power generation mode, MPPT controller 118 is configured to control bidirectional converter 104 and/or inverter 108 based on the output parameters, the synchronization parameters, and the matching parameters, and/or in the load power consumption mode, MPPT controller 118 is configured to control bidirectional converter 104 and/or inverter 108 based on the output parameters and the matching parameters.
In the present embodiment, when the switching device is in the first state, the ac grid 106 is connected to the ac load 110 through the bidirectional converter 104 and the inverter 108, wherein the electric energy may be converted from ac to dc through the bidirectional converter 104, and then the dc is converted into ac through the inverter 108 to be supplied to the ac load 110, in which case the bidirectional converter 104 operates as a rectifier. The photovoltaic power generation device 102 is disconnected from both the ac grid 106 and the ac load 110, the ac grid 106 fully supports the power supply to the ac load 110, and the photovoltaic power generation device 102 does not output electric energy, so that only the matching between the characteristics of the ac load 110 and the ac grid 106 needs to be considered, the MPPT controller 118 does not need to perform the adjusting function of the MPPT controller 118 on the power supply efficiency of the photovoltaic power generation device 102, and the MPPT controller 118 can operate in a standby state or an idle state.
When the switching device is in the second state, the photovoltaic power generation apparatus 102 is connected to the ac power grid 106 through the bidirectional converter 104, wherein the electric energy may be converted from dc to ac through the bidirectional converter 104, so as to realize the energy feeding of the photovoltaic power generation apparatus 102 to the ac power grid 106, and in this scenario, the bidirectional converter 104 operates as an inverter 108. The ac load 110 is disconnected from both the photovoltaic power generation device 102 and the ac grid 106, the ac load 110 is not used, and the electric energy generated by the photovoltaic power generation device 102 is completely imported into the ac grid 106, so that only the synchronization between the photovoltaic power generation device 102 and the ac grid 106 and the maximization of the power supply efficiency need to be considered, and the MPPT controller 118 may operate in a conventional mode or a power generation mode, where the control parameters of the MPPT are the output parameters of the photovoltaic power generation device 102 and the grid synchronization parameters, that is, the outputs of the first detection device 112 and the second detection device 114.
When the switching device is in the second state, the photovoltaic power generation apparatus 102 is connected to the ac power grid 106 via an inverter 108, wherein electrical energy can be converted from dc to ac via the inverter 108, so as to supply the ac load 110 with power from the photovoltaic power generation apparatus 102. The ac grid 106 is disconnected from both the photovoltaic power generation device 102 and the ac load 110, the ac grid 106 neither sinks electric energy from the photovoltaic power generation device 102 nor supplies power to the ac load 110, and the electric energy generated by the photovoltaic power generation device 102 is completely used for driving the ac load 110, so that only the matching between the photovoltaic power generation device 102 and the ac load 110 needs to be considered, and the MPPT controller 118 can operate in a load mode, where the control parameters of the MPPT are the output parameters of the photovoltaic power generation device 102 and the matching parameters of the ac load, that is, the outputs of the first detection device 112 and the third detection device 116.
When the switching device is in the fourth state, the photovoltaic power generation apparatus 102 is connected to the ac grid 106 through the bidirectional converter 104 and is connected to the ac load 110 through the inverter 108, and this connection corresponds to two application modes of the power generation and utilization integrated system: 1) in the load power utilization mode, the capacity of the direct current power generation system is smaller than that of the alternating current load 110, the alternating current grid 106 also needs to supply power to the alternating current load 110, and the bidirectional converter 104 works as a rectifier; 2) in the load power generation mode, the capacity of the dc power generation system is larger than the capacity of the ac load 110, a part of the electric energy generated by the dc power generation system may be supplied to the ac load 110, and another part may be collected into the ac grid 106, and the bidirectional converter 104 may operate as the inverter 108. Correspondingly, the MPPT controller 118 may also operate in two modes: 1) in the load power utilization mode, since the photovoltaic power generation device 102 does not feed energy to the ac grid 106, the output parameters of the photovoltaic power generation device 102 do not need to be synchronized with the ac grid 106, but it still needs to ensure matching between the photovoltaic power generation device 102 and the ac load 110, where the control parameters of MPPT may be the output of the photovoltaic power generation device 102 and the matching parameters of the load, that is, the outputs of the first detection device 112 and the third detection device 116; 2) in the load power generation mode, since the photovoltaic power generation device 102 needs to feed energy to the ac grid 106 while supplying the ac load 110, the target of the MPPT control requires not only matching of the photovoltaic power generation device 102 with the ac grid 106 but also matching of the photovoltaic power generation device 102 with the ac load 110, so that the control parameters of the MPPT may include the output of the photovoltaic power generation device 102, the relevant parameters of the ac grid 106, and the relevant parameters of the ac load 110, that is, the outputs of the first to third detection devices 116.
Through the switching device in the photovoltaic grid-connected system, the power generation and utilization integrated system can work in one or more modes. More specifically, in the embodiment of the present invention, the above switching device may have various implementations, wherein, at most basically, the switching device may be implemented by a switching device, for example, as shown in fig. 3, the switching device may include at least one of the following:
1) a first switching device 302 connected between the photovoltaic power generation apparatus 102 and a dc bus, the dc bus being a transmission line between the bidirectional converter 104 and the inverter 108;
2) a second switching device 304 connected between the photovoltaic power generation apparatus 102 and the ac power grid 106, the second switching device 304 being disposed on the dc bus;
3) and a third switching device 306 connected between the photovoltaic power generation apparatus 102 and the ac load 110, and the third switching device 306 is disposed on the dc bus.
The first switching device 302, the second switching device 304, and the third switching device 306 respectively correspond to the photovoltaic power generation equipment 102, the ac grid 106, and the ac load 110 in the photovoltaic grid-connected system, so that when the first switching device 302 is disconnected, the photovoltaic power generation equipment 102 is disconnected, the switching device can be switched to the first state, when the second switching device 304 is disconnected, the ac grid 106 is disconnected, the switching device can be switched to the third state, and when the third switching device 306 is disconnected, the ac load 110 is disconnected, the switching device can be switched to the second state. More specifically, the switching devices may be semiconductor switches such as IGBTs driven by push-pull amplifiers, or may include high-power switches such as relays, contactors, etc. controlled by a chip, which is not limited in this respect.
It is to be noted that the implementation of the above-mentioned switching means by one or more of the above-mentioned three switching devices is not the only embodiment of the present invention and should not be understood as limiting the present invention, for example, in some embodiments of the present invention, the above-mentioned three switching devices may also be formed in one piece, such as by a selector switch or selector, etc. It is to be understood that such equivalents and obvious variations of the embodiments of the present invention are deemed to be within the scope of the present invention.
Further, in order to reduce the power consumption of the first to third detection devices 116 and/or the MPPT controller 118, in an embodiment of the present invention, the grid-connected photovoltaic system may further include at least one of:
1) a fourth switching device, one end of which is connected to the input end and the other end of which is used for connecting the first detection device 112;
2) a fifth switching device having one end connected to the input terminal and the other end for connecting to the second detecting device 114;
3) and a sixth switching device having one end connected to the input terminal and the other end connected to the third detecting device 116.
The fourth to sixth switches can connect the corresponding detection device to the input end of the MPPT controller 118 in a certain state and mode, which can save energy consumption, and cut off unnecessary signal transmission lines to reduce interference to the signal transmission lines transmitting required electrical parameters, thereby further optimizing the power generation and utilization integrated system.
Furthermore, in an embodiment of the present invention, the photovoltaic grid-connected system may further include:
1) and the mode controller is connected with the switching device and the MPPT controller 118, and is used for controlling the switching device to switch among a plurality of states and controlling the MPPT controller 118 to switch to a control mode corresponding to the connection relation among the alternating current power grid 106, the alternating current load 110 and the photovoltaic power generation equipment 102.
In general, in the embodiment of the present invention, the mode controller may adopt a design of combining a control loop with a power element, but the present invention is not limited to this, wherein the mode controller and the MPPT controller 118 may be independent from each other or may be integrated into one body, for example, may appear as one integrated controller, wherein the integrated controller may also include two-stage control loops. Specifically, for the foregoing embodiment, the mode controller may control the first to third switching devices, and further, the mode controller may also control the fourth to sixth switches together, which depends on the requirement of the control integration level in the specific implementation of the present invention, and the present invention is not limited thereto. More specifically, in the embodiment of the present invention, the mode controller may control the switching device according to the detected capacity of the photovoltaic power generation apparatus 102, the detected capacity of the ac power grid 106, and the detected capacity of the ac load 110, for example, the efficiency of the photovoltaic power generation apparatus 102 may be maximized according to the photovoltaic priority principle, but the present invention is not limited thereto.
Based on the above description, in view of the requirement of stability of the electric energy transmitted on the dc transmission line connected between the bidirectional converter 104 and the inverter 108, or the dc bus for splitting or converging in the architecture provided by the embodiment of the present invention, in the embodiment of the present invention, the photovoltaic grid-connected system may further include:
1) and a fourth detection device disposed on the dc bus, the dc bus being a transmission line between the bidirectional converter 104 and the inverter 108, the fourth detection device being connected to the input end, wherein the MPPT controller 118 is configured to control the bidirectional converter 104 and/or the inverter 108 according to the output parameter, and/or the synchronization parameter, and/or the matching parameter, and the voltage and/or the current detected by the fourth detection device at the corresponding detection point.
In the embodiment of the present invention, the electrical parameter on the dc bus as the MPPT control target and other aforementioned input parameters of the MPPT controller 118 may be simultaneously obtained from one or more of the first to fourth detection devices, and the control object thereof may still be the bidirectional converter 104 and/or the inverter 108, wherein a specific control strategy may generally adopt a state space control manner, which is not limited in this embodiment of the present invention.
The technical solution and the operation principle of the present invention are explained by the above embodiments, however, it should be noted that the above embodiments are only used for understanding the technical solution of the present invention, and do not constitute any unnecessary limitation to the present invention, for example, fig. 3 shows a possible connection relationship of the first to third switching devices, however, in other embodiments of the present invention, the second switching device 304 and the third switching device 306 may be disposed outside the bidirectional connector and the inverter 108, respectively, and so on.
It should be further noted that, in the embodiment of the present invention, the connection lines in fig. 1 and fig. 3 are only used as an illustration of the connection relationship between the devices, and it is not meant to limit the transmission lines corresponding to these connection lines to only one in the embodiment of the present invention, and specifically, in the embodiment of the present invention, the transmission lines connected between the ac grid 106 and the bidirectional converter 104 and between the ac load 110 and the inverter 108 may be three-phase power transmission lines, and the transmission lines connected between the bidirectional converter 104 and the inverter and between both the bidirectional converter 104 and the photovoltaic power generation apparatus 102 may be dc transmission lines. Of course, this is merely an example, and in some embodiments of the present invention, the transmission lines connected between the ac power grid 106 and the bidirectional converter 104 and between the ac load 110 and the inverter 108 may also be carriers of other ac power transmission, such as a single-phase power transmission line, and the present invention is not limited thereto.
In addition, in the embodiment of the present invention, there may be a plurality of specific forms of the ac loads 110, which may be regarded as representing the entirety of the loads connected in the pv grid-connected system, and is not limited to a specific type, wherein a plurality of ac loads 110 or sub-networks may be connected in the load network, and the specific topology structure thereof may be various, which may be determined according to the specific application of the pv grid-connected system, for example, for the pv air-conditioning network, the loads driven by the load network may include an air conditioner, or a power device inside the air conditioner, such as a centrifugal compressor, and the like, which does not affect the implementation of the technical solution of the present invention and the implementation of the technical effect thereof, and the present invention is not limited in any way.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (5)
1. A grid-connected photovoltaic system, comprising:
a photovoltaic power generation device for outputting direct current power;
the bidirectional converter is connected between the photovoltaic power generation equipment and an alternating current power grid, wherein the photovoltaic power generation equipment corresponds to a direct current end of the bidirectional converter, and the alternating current power grid corresponds to an alternating current end of the bidirectional converter;
the inverter is connected between the photovoltaic power generation equipment and an alternating current load, wherein the photovoltaic power generation equipment corresponds to the direct current end of the inverter, and the alternating current load corresponds to the alternating current end of the inverter;
the first detection equipment is arranged between the photovoltaic power generation equipment and the bidirectional converter and at least used for detecting output parameters of the photovoltaic power generation equipment;
a second detection device arranged between the alternating current network and the bidirectional converter, at least for detecting synchronization parameters of the alternating current network;
the third detection equipment is arranged between the alternating current load and the inverter and at least used for detecting the matching parameters of the alternating current load;
an MPPT controller having an input connected to the first, second and third detection devices and an output connected to the bidirectional converter and the inverter for controlling the bidirectional converter and/or the inverter according to at least one of the following parameters: the output parameter, the synchronization parameter, the matching parameter;
the MPPT controller is used for switching to a control mode corresponding to the connection relation among a plurality of control modes according to the connection relation among the alternating current power grid, the alternating current load and the photovoltaic power generation equipment;
a switching device connected between the ac grid, the ac load, and the photovoltaic power generation apparatus, wherein when the switching device is in any one of a plurality of states, the connection relationship is switched to a connection relationship corresponding to the any one of the states;
the mode controller is connected with the switching device and the MPPT controller, and is used for controlling the switching device to switch among the states and controlling the MPPT controller to switch to a control mode corresponding to the connection relation;
the mode controller is used for controlling the switching device according to the detected capacity of the photovoltaic power generation equipment, the detected capacity of the alternating current power grid and the detected capacity of the alternating current load;
a fourth detection device arranged on a dc bus, the dc bus being a transmission line between the bidirectional converter and the inverter, the fourth detection device being connected to the input end, wherein the MPPT controller is configured to control the bidirectional converter and/or the inverter according to the output parameter, and/or the synchronization parameter, and/or the matching parameter, and the voltage and/or current detected by the fourth detection device at the corresponding detection point.
2. The grid-connected PV system of claim 1,
when the switching device is in a first state of the plurality of states, the photovoltaic power generation equipment is disconnected from the alternating current grid and the alternating current load, and the MPPT controller is switched to an idle mode of the plurality of control modes; and/or the presence of a gas in the gas,
when the switching device is in a second state of the plurality of states, the AC load is disconnected from the photovoltaic power generation equipment and the AC power grid, and the MPPT controller switches to a power generation mode of the plurality of control modes for controlling the bidirectional converter according to the output parameter and the synchronization parameter; and/or the presence of a gas in the gas,
when the switching device is in a third state of the plurality of states, the alternating current power grid is disconnected from the photovoltaic power generation equipment and the alternating current load, and the MPPT controller is switched to a load mode of the plurality of control modes and used for controlling the inverter according to the output parameter and the matching parameter; and/or the presence of a gas in the gas,
when the switching device is in a fourth state of the plurality of states, the photovoltaic power generation apparatus is connected to the AC power grid through the bidirectional converter and to the AC load through the inverter, the MPPT controller switches to a load power generation mode or a load power utilization mode of the plurality of control modes, wherein,
in the load power generation mode, the MPPT controller is configured to control the bidirectional converter and/or the inverter according to the output parameter, the synchronization parameter, and the matching parameter, and/or in the load power consumption mode, the MPPT controller is configured to control the bidirectional converter and/or the inverter according to the output parameter and the matching parameter.
3. The grid-connected photovoltaic system according to claim 1, wherein the switching device comprises at least one of:
the first switching device is connected between the photovoltaic power generation equipment and a direct current bus, and the direct current bus is a transmission line between the bidirectional converter and the inverter;
the second switching device is connected between the photovoltaic power generation equipment and the alternating current power grid and arranged on the direct current bus;
and the third switching device is connected between the photovoltaic power generation equipment and the alternating current load, and is arranged on the direct current bus.
4. The grid-connected photovoltaic system according to any one of claims 1 to 3, wherein the MPPT controller is configured to control the bidirectional converter and/or the inverter by a signal of one of: voltage signal, current signal, pulse width modulation signal.
5. The grid-connected PV system of any one of claims 1 to 3,
the photovoltaic power generation apparatus includes: the photovoltaic cell, the confluence unit and the power distribution unit; and/or the presence of a gas in the gas,
the AC load comprises an air conditioner; and/or the presence of a gas in the gas,
the transmission line connected between the alternating current power grid and the bidirectional converter is a three-phase power transmission line or a single-phase power transmission line; and/or the presence of a gas in the gas,
the transmission line connected between the ac load and the inverter is a three-phase power transmission line or a single-phase power transmission line.
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| CN104135225A (en) * | 2014-07-11 | 2014-11-05 | 珠海格力电器股份有限公司 | Photovoltaic inverter and air conditioner |
| CN106936156A (en) * | 2015-12-30 | 2017-07-07 | 中国科学院西安光学精密机械研究所 | A kind of photovoltaic power generation grid-connecting power supply control apparatus |
| CN106602605B (en) * | 2017-01-03 | 2024-05-03 | 珠海格力电器股份有限公司 | Maximum power point tracking control system of photovoltaic array and photovoltaic air conditioning system |
| CN108092316B (en) * | 2018-01-16 | 2020-05-08 | 博阳能源科技有限公司 | Modularized photovoltaic power generation system |
| CN108281952B (en) * | 2018-02-10 | 2024-04-16 | 珠海格力电器股份有限公司 | Photovoltaic power supply system and power supply control method thereof |
| CN115882516B (en) * | 2023-03-08 | 2023-06-06 | 杭州欣美成套电器制造有限公司 | Photovoltaic grid-connected control device and method for high-efficiency photovoltaic charging control |
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| CN101841188A (en) * | 2010-02-08 | 2010-09-22 | 哈尔滨工业大学 | Hybrid power supply uninterruptible inverted power supply of power feedback type optical network |
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| CN203895990U (en) * | 2013-12-24 | 2014-10-22 | 珠海格力电器股份有限公司 | Photovoltaic grid-connected system |
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| JP5081596B2 (en) * | 2007-12-04 | 2012-11-28 | シャープ株式会社 | Power supply system |
| KR101084215B1 (en) * | 2009-12-16 | 2011-11-17 | 삼성에스디아이 주식회사 | Energy storage system and method for controlling thereof |
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| CN102088190A (en) * | 2009-12-03 | 2011-06-08 | 三星Sdi株式会社 | Grid-connected power storage system and method for controlling grid-connected power storage system |
| CN101841188A (en) * | 2010-02-08 | 2010-09-22 | 哈尔滨工业大学 | Hybrid power supply uninterruptible inverted power supply of power feedback type optical network |
| CN102931653A (en) * | 2012-11-02 | 2013-02-13 | 浙江工业大学 | Comprehensive coordination control method of wind-solar direct current micro-grid |
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