CN105305407A - Photovoltaic high-voltage DC transmission system - Google Patents
Photovoltaic high-voltage DC transmission system Download PDFInfo
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- CN105305407A CN105305407A CN201510696953.0A CN201510696953A CN105305407A CN 105305407 A CN105305407 A CN 105305407A CN 201510696953 A CN201510696953 A CN 201510696953A CN 105305407 A CN105305407 A CN 105305407A
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Abstract
The invention discloses a photovoltaic high-voltage DC transmission system, which comprises at least two photovoltaic power generation units and one photovoltaic hot standby power generation unit, wherein the more than two photovoltaic power generation units are serially connected and are serially connected with the output side of the photovoltaic hot standby power generation unit (15) and then connected into a high-voltage DC transmission line (16); the output side of the high-voltage DC transmission line (16) is connected with the input side of a high-voltage inverter (17); the high-voltage inverter (17) outputs high-voltage three-phase AC and is accessed to an AC high-voltage power grid (18); low-voltage isolation switch input sides of the multiple photovoltaic power generation units and the photovoltaic hot standby power generation unit (15) are parallelly connected via a photovoltaic input side parallel connection line (110); a system controller (15) is connected with a converter controllers of the photovoltaic power generation units and the photovoltaic hot standby power generation unit via signal lines for controlling on the photovoltaic power generation units and the photovoltaic hot standby power generation unit; and the high-voltage inverter (17) adopts a modular multilevel topology structure.
Description
Technical field
The present invention relates to a kind of photovoltaic power generation equipment access HVDC (High Voltage Direct Current) transmission system.
Background technology
The energy plays an important role in modern society, is one of modern society's foundation stone of depending on for existence and development, is also current International Politics, economic focal issue.Energy problem is related to International Politics wind and cloud, is related to the socio-economic development of country.Utilizing renewable energy power generation to substitute fossil energy, is the general choice of current various countries.Photovoltaic generation is as the important form of renewable energy power generation, and due to its cleaning, environmental protection, Land use systems feature flexibly, be subject to increasing attention, its installed capacity develops rapidly at home.
The grid-connected form of common photovoltaic generating system is to be incorporated to AC network.And current domestic flexible direct current and Traditional DC transmission of electricity fast development, demonstrative project gets more and more, and photovoltaic generation must possess the ability of access high-voltage dc transmission electrical network.
It is lower to there is output voltage in common photovoltaic DC converter, and be difficult to disposablely boost to very high-tension problem, high-voltage direct current power grid is incorporated in order to realize photovoltaic system output, the input of multiple photovoltaic DC converter is generally taked to connect independent photovoltaic assembly at present, the mode exporting series connection improves the output voltage of system, thus reaches and export more High Level DC Voltage thus the object of access high-voltage direct current power grid.Domestic at present have more document and patent to set forth the program.
CN204103503U proposes a kind of scheme being exported series connection access mesohigh direct current system by photovoltaic generation unit; but the input that in scheme, each exports tandem photovoltaic generator unit is independent separately; be difficult to realize power coordination export; and do not provide the coordination control strategy of each photovoltaic generation unit; because multiple photovoltaic generation unit exports series connection, as riches all the way, electric unit goes wrong simultaneously, then whole system cannot be shut down.
201310244951.9 propose a kind of photovoltaic DC transmission system of similar modular multi-level converter structure, but its DC converting and power cell are non-isolated topology, the secured electrical isolation between high voltage power transmission and photovoltaic module cannot be realized, and due to the existence of redundant module, the photovoltaic module that during non-faulting, redundant module is corresponding cannot realize power stage, during fault, single photovoltaic generation unit is isolated, and photovoltaic module cannot realize power stage, reduces the utilance of photovoltaic module.
CN204068816U, proposes a kind of block coupled in series that utilizes and improves the method for output voltage, and the output being specially multiple voltage transformation module is in series composition photovoltaic plant successively, as the input of high voltage direct current transmission after the output parallel connection of multiple photovoltaic plant.And which propose a kind of topological project of voltage transformation module.But this invention still exists the problem that when single module goes wrong, system cannot be run, and do not illustrate the control method adopted when adopting the program.
In this type of scheme of current proposition and patent, detailed embodiment photovoltaic DC converter being exported to series topology is set forth.But there are some problems in the program:
1. input photovoltaic DC converter that is independent, that export series connection connects in topology, the photovoltaic module connected due to photovoltaic DC converter is different, the fluctuation of its input power causes more greatly its output voltage to change greatly, must strictly control multiple photovoltaic DC converter output voltage all to press, this type of control algolithm is complicated, and reliability is lower.
2. photovoltaic DC converter export for being connected in series, modules flow through identical grid-connected current, when certain module breaks down, whole system cannot be run, and reduce the reliability of this system.During malfunctioning module excision, the photovoltaic module of this model calling is also cut simultaneously, reduces the utilance of photovoltaic module, reduces the photovoltaic power generation quantity in this power station.
3. this system access high-voltage direct current power grid, its voltage is generally more than 10kV, and withstand voltage over the ground 1kV or 1.5kV that be generally of photovoltaic module, in order to the personal safety of the device security and assembly attendant that ensure photovoltaic module, the high-pressure system of DC converter both sides and low-pressure system must be isolated.
Summary of the invention
The present invention seeks to overcome photovoltaic HVDC (High Voltage Direct Current) transmission system control complexity, low, easy problem low-pressure system being introduced to high pressure of reliability that prior art exports series topology, propose a kind of photovoltaic HVDC (High Voltage Direct Current) transmission system.
The technical solution adopted in the present invention is as follows:
Photovoltaic HVDC (High Voltage Direct Current) transmission system of the present invention comprises photovoltaic generation unit, the hot standby generator unit of photovoltaic, photovoltaic input side interconnection, system controller, HVDC (High Voltage Direct Current) transmission line in parallel, and high-voltage inverter.Described photovoltaic generation unit and the hot standby generator unit outlet side of photovoltaic are connected in parallel, and connect HVDC (High Voltage Direct Current) transmission line subsequently, are alternating current incoming transport high-voltage fence at ultra-high-tension power transmission line opposite side by high-voltage inverter by DC power conversion.Described photovoltaic generation unit at least adopts 2, and the hot standby generator unit of photovoltaic at least adopts 1.Connect between multiple described photovoltaic generation unit, and be connected in series with the hot standby generator unit outlet side of photovoltaic; Described system controller is used for unifying to control to all photovoltaic generation units and the hot standby generator unit of photovoltaic; Described high-voltage inverter is centralized high-voltage inverter, adopts modular multilevel topological structure.
Photovoltaic generation unit comprises photovoltaic module, photovoltaic MPPT (MaximumPowerPointTracking, MPPT maximum power point tracking) DC/DC converter, low voltage isolation switch, photovoltaic booster converter and high_voltage isolation by-pass switch.Photovoltaic module, photovoltaic MPPT DC/DC converter, low voltage isolation switch, between photovoltaic booster converter and high_voltage isolation by-pass switch, sequential series connects.Photovoltaic module is sent Energy transfer to outlet side when being used for normal work by photovoltaic generation unit.
The hot standby generator unit of photovoltaic comprises low voltage isolation switch, photovoltaic booster converter and high_voltage isolation by-pass switch.Between low voltage isolation switch, photovoltaic booster converter, high_voltage isolation by-pass switch, sequential series connects; The hot standby generator unit of photovoltaic is used for after certain photovoltaic generation unit failure removal of photovoltaic HVDC (High Voltage Direct Current) transmission system of the present invention, puts into operation under the non-stop-machine state of system, thus improves the reliability of photovoltaic HVDC (High Voltage Direct Current) transmission system of the present invention.The low voltage isolation switch input side of photovoltaic generation unit and the hot standby generator unit of photovoltaic realizes in parallel by photovoltaic input side interconnection in parallel;
Low voltage isolation switch comprises an isolating switch.Described isolating switch can be mechanical contactor, circuit breaker, can be also electronic power switch device, as IGBT; Current transformer input side disconnects when being used for photovoltaic booster converter fault by described low voltage isolation switch, is convenient to change current transformer.
High_voltage isolation by-pass switch comprises a fault isolator and a switch failure by-pass, and switch failure by-pass is connected in parallel on the outlet side of fault isolator; Described fault isolator and switch failure by-pass can be mechanical contactor, circuit breaker, can be also electronic power switch devices, as IGBT; By current transformer bypass when described high_voltage isolation by-pass switch is used for photovoltaic booster converter fault, and forms isolating points with high voltage power transmisson system, be convenient to replacing current transformer.
Photovoltaic MPPT DC/DC converter realizes the maximal power tracing function to photovoltaic module, and its concrete topology can be isolated topology also can be non-isolated topology.Described converter, for hicap, can be Boost topology, thus can improve output dc voltage reduction system loss; Described converter front end at least connects a road photovoltaic module, and when connecting multi-path light photovoltaic assembly, converter comprises photovoltaic conflux module.
Photovoltaic booster converter topology is necessary for isolated topology and possesses certain boost capability, and the isolating transformer of described photovoltaic booster converter is withstand voltage should be DC transmission system maximum voltage; Described photovoltaic booster converter also comprises an inverter controller, for current transformer disorderly closedown, online drop into time transient process control current transformer operating state; Described photovoltaic booster converter designs for high modularization, adopts the mode of integral replacing to safeguard when a failure occurs, greatly reduces system maintenance time, improves system reliability.
The low voltage isolation switch input side of photovoltaic generation unit and the hot standby generator unit of photovoltaic utilizes photovoltaic input side interconnection in parallel to realize in parallel, thus realizes the series connection of photovoltaic booster converter input side Parallel opertation side, thus simplifies system control scheme.
System controller adopts unified Duty ratio control to all photovoltaic generation units and the hot standby generator unit of photovoltaic; System controller at least gathers high-voltage direct current power grid grid-connected current, after producing algorithm computing when normal operation according to unified duty ratio, export duty cycle signals to inverter controller, the current transformer of photovoltaic generation unit runs according to duty cycle signals, the current transformer of photovoltaic generation unit receives only duty cycle signals and does not run, and is in hot standby state.
When the photovoltaic booster converter fault of a certain photovoltaic generation unit, system controller sends control signal, the photovoltaic generation unit that bypass is broken down, and start the hot standby generator unit of photovoltaic, its output voltage is made to reach equal voltage levels, realize the Energy transmission to fault photovoltaic generation unit front end photovoltaic module, make full use of photovoltaic module energy output; System controller sends signal to the low voltage isolation switch of fault photovoltaic generation unit and high voltage isolator subsequently, is isolated by fault photovoltaic booster converter, can carry out safeguarding or keeping in repair.
The quantity of the hot standby generator unit of photovoltaic is comprehensively determined according to the quantity of photovoltaic generation unit and failure-frequency, and failure-frequency height then photovoltaic after heat preparation electric unit quantity is many; The selection of photovoltaic input side interconnection cable cross-sections in parallel is relevant with photovoltaic hot standby generator unit quantity, the maximum current that the area of section of photovoltaic input side interconnection cable in parallel can flow through according to it and interconnection cable type are determined jointly, and the maximum current flowing through photovoltaic input side interconnection in parallel during fault meets following formula:
Wherein P is the power of photovoltaic generation unit, and U is the voltage of photovoltaic input side interconnection in parallel, and m is the quantity of the hot standby generator unit of photovoltaic, flows through the maximum current of photovoltaic hot standby generator unit when I is fault.
The hot standby generator unit of photovoltaic generation unit, photovoltaic, system controller, photovoltaic input side interconnection in parallel forms a road photovoltaic DC high voltage power generation unit, the wherein outlet side of photovoltaic generation unit and the hot standby generator unit outlet side series connection of photovoltaic, photovoltaic generation unit and photovoltaic hot standby generator unit low voltage isolation switch input side are together in parallel by photovoltaic input side interconnection in parallel, and system controller controls inverter controller by output action signal controlling low voltage isolation switch and high_voltage isolation by-pass switch, output control signal.Photovoltaic HVDC (High Voltage Direct Current) transmission system of the present invention is according to the capacity of grid connection capacity and direct current high tension transmission net, can be designed with multichannel photovoltaic DC high voltage power generation unit independent of each other, the output-parallel of multichannel photovoltaic DC high voltage power generation unit independent of each other is connected in direct current high tension transmission net.
Beneficial effect of the present invention:
1. for traditional output tandem photovoltaic generator unit, the present invention is by increasing photovoltaic input side interconnection in parallel in low voltage isolation switch front end, thus reach the object of balanced each photovoltaic booster converter input power, thus enormously simplify the control mode of photovoltaic booster converter, adopt interconnection to carry out power equalization to avoid because direct current confluxes the excessive loss problems of too caused of electric current simultaneously, improve system effectiveness.
2. the present invention is outside conventional photovoltaic generator unit, be equipped with again the hot standby generator unit of photovoltaic, normal operation time latent heat preparation electric unit connecting system but do not run through-put power, when certain photovoltaic generation unit fault is out of service, this hot standby unit puts into operation, taken over the electric energy of its front end photovoltaic module by interconnection, after converting, be incorporated to high-voltage direct current power grid.The system that achieves is not shut down and is dropped into hot standby generator unit, substantially increases system reliability.
3. the present invention increases isolating switch in photovoltaic booster converter low-pressure side and high-pressure side, and malfunctioning module can excise by guarantee in the non-stop-machine situation of system, and forms electrical isolation with operational system, facilitates module to remove repair and maintenance.
Accompanying drawing explanation
Fig. 1 is the system schema topological diagram of the embodiment of the present invention;
In figure: 11 first photovoltaic generation units, 12 second photovoltaic generation units, 13 (n-1)th photovoltaic generation unit n-1,14 n-th photovoltaic generation unit n, the hot standby generator unit of 15 photovoltaic, 16 HVDC (High Voltage Direct Current) transmission line, 17 high-voltage inverters, 18 ac high-voltage electrical networks, 19 system controllers, 110 photovoltaic input sides interconnection in parallel.
Fig. 2 is the structure chart of embodiment of the present invention photovoltaic generation unit;
In figure: 21 photovoltaic modulies, 22 photovoltaic MPPT DC/DC converters, 23 low voltage isolation switchs, 24 photovoltaic booster converters, 25 high_voltage isolation by-pass switches, 26 inverter controllers;
Fig. 3 is the hot standby generator unit structure chart of embodiment of the present invention photovoltaic,
In figure: 23 low voltage isolation switchs, 24 photovoltaic booster converters, 25 high_voltage isolation by-pass switches, 26 inverter controllers.
Fig. 4 is embodiment of the present invention low voltage isolation switch structure chart;
Fig. 5 is embodiment of the present invention high_voltage isolation by-pass switch structure chart,
In figure: QF2 fault isolator, QF3 switch failure by-pass;
Fig. 6 is embodiment of the present invention system controller structure chart,
In figure: 191 low voltage isolation switch actuating signals, 192 photovoltaic generation units and the hot standby generator unit of photovoltaic unify duty cycle signals, 193 high_voltage isolation by-pass switch actuating signals, 194 photovoltaic generation unit output electric current measure signals.
Embodiment
The present invention is further illustrated below in conjunction with the drawings and specific embodiments.
Fig. 1 is embodiment of the present invention topological diagram.As shown in Figure 1, photovoltaic HVDC (High Voltage Direct Current) transmission system of the present invention comprises the first photovoltaic generation unit 11, second photovoltaic generation unit 12, (n-1)th photovoltaic generation unit 13, n-th photovoltaic generation unit 14, the hot standby unit 15 of photovoltaic generation, photovoltaic input side interconnection 110, system controller 19, HVDC (High Voltage Direct Current) transmission line 16 in parallel, and high-voltage inverter 17.In the present embodiment, photovoltaic generation unit at least adopts n, and n is integer, n > 1, and the hot standby generator unit of photovoltaic adopts 1; Be one another in series between n photovoltaic generation unit, and be connected in series with the hot standby generator unit outlet side of photovoltaic, access HVDC (High Voltage Direct Current) transmission line 16 subsequently, the outlet side of HVDC (High Voltage Direct Current) transmission line 16 is connected with the input side of high-voltage inverter 17, high-voltage inverter 17 exports high pressure three-phase alternating current, the low voltage isolation switch input side being incorporated to ac high-voltage electrical network 18, n photovoltaic generation units and the hot standby generator unit of photovoltaic is connected in parallel by photovoltaic input side interconnection 110 in parallel.Described system controller 19 controls for unifying all photovoltaic generation units and the hot standby generator unit of photovoltaic, this controller comprises at least three output signals, an input signal, three output signals are respectively the hot standby generator unit of low voltage isolation switch actuating signal 191, photovoltaic generation unit and photovoltaic and unify duty cycle signals 192, high_voltage isolation by-pass switch actuating signal 193, and input signal is photovoltaic generation unit output electric current measure signal 194.Described high-voltage inverter 17 is centralized configuration, adopts modular multilevel topological structure.
Fig. 2 is the structure chart of embodiment of the present invention photovoltaic generation unit.As shown in Figure 2, photovoltaic generation unit comprises photovoltaic module 21, photovoltaic MPPT DC/DC converter 22, low voltage isolation switch 23, photovoltaic booster converter 24, high_voltage isolation by-pass switch 25; The output of photovoltaic module 21 connects the input side of photovoltaic MPPT DC/DC converter 22, the photovoltaic MPPT outlet side of DC/DC converter 22 connects one end of low voltage isolation switch 23, the other end of low voltage isolation switch 23 connects the input side of photovoltaic booster converter 24, the outlet side of photovoltaic booster converter 24 is connected in series high_voltage isolation by-pass switch 25, high_voltage isolation by-pass switch 25 outlet side forms the outlet side of photovoltaic generation unit, and inverter controller 26 and photovoltaic booster converter 24 become one.
Photovoltaic MPPT DC/DC converter 22 realizes the maximal power tracing function to photovoltaic module, and its concrete topology can be isolated topology also can be non-isolated topology; Described photovoltaic MPPT DC/DC converter 22, for hicap, can be Boost topology, thus can improve output dc voltage reduction system loss; The described photovoltaic MPPT front end of DC/DC converter 22 at least connects a road photovoltaic module, and when connecting multi-path light photovoltaic assembly, photovoltaic MPPT DC/DC converter comprises photovoltaic conflux module.
Fig. 3 is the hot standby generator unit structure chart of embodiment of the present invention photovoltaic.As shown in Figure 3, the hot standby generator unit 15 of photovoltaic comprises low voltage isolation switch 23, photovoltaic booster converter 24, high_voltage isolation by-pass switch 25, inverter controller 26.Said elements sequential series connects.
The hot standby generator unit of photovoltaic 15 pairs of photovoltaic generation units are formed hot standby.Time out of service for photovoltaic generation unit fault, take over the photovoltaic module of photovoltaic generation unit front end out of service, after the transformation of electrical energy sent by photovoltaic module, import high direct voltage electrical network.
The topology of photovoltaic booster converter 14 is necessary for isolated topology, and possesses certain boost capability, and the isolating transformer of described photovoltaic booster converter 24 is withstand voltage should be DC transmission system maximum voltage; Described photovoltaic booster converter also comprises an inverter controller, for current transformer disorderly closedown, online drop into time transient process control current transformer operating state; Described photovoltaic booster converter designs for high modularization, adopts the mode of integral replacing to safeguard when a failure occurs, greatly reduces system maintenance time, improves system reliability.
Fig. 4 is the structure chart of embodiment of the present invention low voltage isolation switch 23.Described low voltage isolation switch 23 comprises an isolating switch QF1.Fig. 5 is embodiment of the present invention high_voltage isolation by-pass switch 25 structure chart.High_voltage isolation by-pass switch 25 comprises fault isolator QF2 and switch failure by-pass QF3.Isolating switch QF1, fault isolator QF2, switch failure by-pass QF3 can be mechanical contactor, circuit breaker, can be also electronic power switch devices, as IGBT; Mechanical type isolating switch easily forms mechanical power-off, advantageously in repair and maintenance, the isolating switch that power electronic device is formed, can be used for cutting off running current or equipment circulation, power electronic device form isolating switch can be used alone, also can with isolation switch with the use of.Current transformer input side disconnects for during photovoltaic booster converter fault by described low voltage isolation switch 25, isolating points is formed with photovoltaic MPPT DC/DC controller 22, described switch failure by-pass QF3 be used for photovoltaic booster converter fault time by current transformer bypass, current transformer outlet side disconnects for during photovoltaic booster converter fault by described high_voltage isolation by-pass switch 25, form isolating points with high voltage power transmisson system, be convenient to change current transformer.Low voltage isolation switch 23 and high_voltage isolation by-pass switch 25 for bypass photovoltaic booster converter during fault, and form significantly electrically power-off with side, front and back, and convenient extraction out by the photovoltaic booster converter of high modularization is safeguarded.
Fig. 6 is the structure chart of embodiment of the present invention system controller 19.The output signal of system controller 19 mainly contains: 191 low voltage isolation switch actuating signals, and 192 photovoltaic generation units and the hot standby generator unit of photovoltaic unify duty cycle signals, 193 high_voltage isolation by-pass switch actuating signals.The input signal of system controller mainly contains 194 photovoltaic generation unit output electric current measure signals.System controller 19 adopts unified Duty ratio control to all photovoltaic generation units and the hot standby generator unit of photovoltaic; System controller 19 at least gathers high-voltage direct current power grid grid-connected current, after producing algorithm computing when normal operation according to unified duty ratio, export duty cycle signals to inverter controller, the current transformer of photovoltaic generation unit runs according to duty cycle signals, the current transformer of photovoltaic generation unit receives only duty cycle signals and does not run, and is in hot standby state.
The low voltage isolation switch input side of photovoltaic generation unit and the hot standby generator unit of photovoltaic utilizes photovoltaic input side interconnection in parallel to realize in parallel, thus realizes the series connection of photovoltaic booster converter input side Parallel opertation side, thus simplifies system control scheme.
When the photovoltaic booster converter fault of a certain photovoltaic generation unit, system controller sends control signal, the photovoltaic generation unit that bypass is broken down, and start the hot standby generator unit of photovoltaic, its output voltage is made to reach equal voltage levels, realize the Energy transmission to fault photovoltaic generation unit front end photovoltaic module, make full use of photovoltaic module energy output; System controller sends signal to the low voltage isolation switch of fault photovoltaic generation unit and high voltage isolator subsequently, is isolated by fault photovoltaic booster converter, can carry out safeguarding or keeping in repair.
The quantity of the hot standby generator unit of photovoltaic is comprehensively determined according to the quantity of photovoltaic generation unit and failure-frequency, and failure-frequency height then photovoltaic after heat preparation electric unit quantity is many; The selection of photovoltaic input side interconnection cable cross-sections in parallel is relevant with photovoltaic hot standby generator unit quantity, the maximum current that the area of section of photovoltaic input side interconnection in parallel can flow through according to it and interconnection cable type are determined jointly, and the maximum current flowing through photovoltaic input side interconnection in parallel during fault meets following formula:
Flow through the maximum current of photovoltaic hot standby generator unit when wherein I is fault, P is the power of photovoltaic generation unit, and U is the voltage of photovoltaic input side interconnection in parallel, and m is the quantity of the hot standby generator unit of photovoltaic.
The multiple photovoltaic generation units exporting series connection export, the hot standby generator unit of photovoltaic exports and system controller exports series connection, and the hot standby generator unit of photovoltaic generation unit, photovoltaic, system controller and photovoltaic input side interconnection in parallel forms a road photovoltaic DC high voltage power generation unit.Photovoltaic HVDC (High Voltage Direct Current) transmission system of the present invention is according to the capacity of grid connection capacity and direct current high tension transmission net, multichannel photovoltaic high direct voltage generator unit independent of each other can be designed with, the output-parallel of multichannel photovoltaic high direct voltage generator unit, is connected in direct current high tension transmission net.
Photovoltaic HVDC (High Voltage Direct Current) transmission system of the present invention, by increasing photovoltaic input side interconnection in parallel, thus reach the object of balanced each photovoltaic booster converter input power, thus enormously simplify the control mode of photovoltaic booster converter, adopt interconnection to carry out power equalization to avoid because direct current confluxes the excessive loss problems of too caused of electric current simultaneously, improve system effectiveness.The present invention is equipped with the hot standby generator unit of photovoltaic, and avoid the energy output loss caused because part photovoltaic generation unit releases operation, the system that achieves is not shut down and dropped into hot standby generator unit, substantially increases system reliability, takes full advantage of photovoltaic module.The present invention both increases isolating switch in booster converter low-pressure side and high-pressure side; malfunctioning module can excise by guarantee in the non-stop-machine situation of system; and form electrical isolation with operational system; module is facilitated to remove repair and maintenance; substantially reduce the power failure preventive maintenance time of system, improve systems generate electricity amount.
Claims (10)
1. a photovoltaic HVDC (High Voltage Direct Current) transmission system, it is characterized in that: described photovoltaic HVDC (High Voltage Direct Current) transmission system comprises photovoltaic generation unit, the hot standby unit of photovoltaic generation (15), photovoltaic input side interconnection (110) in parallel, system controller (19), HVDC (High Voltage Direct Current) transmission line (1), and high-voltage inverter (17), described photovoltaic generation unit is at least 2, and the hot standby generator unit of photovoltaic (15) at least adopts 1, connect between the described photovoltaic generation unit of more than 2, and be connected in series with the outlet side of the hot standby generator unit of photovoltaic (15), access HVDC (High Voltage Direct Current) transmission line (16) subsequently, the outlet side of HVDC (High Voltage Direct Current) transmission line (16) is connected with the input side of high-voltage inverter (17), high-voltage inverter (17) exports high pressure three-phase alternating current, be incorporated to ac high-voltage electrical network (18), the low voltage isolation switch input side of multiple photovoltaic generation unit and the hot standby generator unit of photovoltaic (15) is connected in parallel by photovoltaic input side interconnection (110) in parallel, described system controller (15) is connected, for the control to photovoltaic generation unit and the hot standby generator unit of photovoltaic by the inverter controller of holding wire with photovoltaic generation unit and the hot standby generator unit of photovoltaic, described high-voltage inverter (17) adopts modular multilevel topological structure.
2. photovoltaic HVDC (High Voltage Direct Current) transmission system according to claim 1, is characterized in that: described photovoltaic generation unit comprises photovoltaic module (21), photovoltaic MPPT MPPT maximum power point tracking DC/DC converter (22), low voltage isolation switch (23), photovoltaic booster converter (24) and high_voltage isolation by-pass switch (25), the output of photovoltaic module (21) connects the input side of photovoltaic MPPT with DC/DC converter (22), the photovoltaic MPPT outlet side of DC/DC converter (22) connects one end of low voltage isolation switch (23), the other end of low voltage isolation switch (23) connects the input side of photovoltaic booster converter (24), the outlet side of photovoltaic booster converter (24) is connected in series high_voltage isolation by-pass switch (25), the outlet side of high_voltage isolation by-pass switch (25) forms the outlet side of photovoltaic generation unit, inverter controller (26) and photovoltaic booster converter (24) become one.
3. photovoltaic HVDC (High Voltage Direct Current) transmission system according to claim 1 and 2, is characterized in that: the composition structure of the hot standby generator unit of described photovoltaic (15) is identical with photovoltaic generation unit; The hot standby generator unit of photovoltaic is used for after certain photovoltaic generation unit failure removal, puts into operation under the non-stop-machine state of system.
4. photovoltaic HVDC (High Voltage Direct Current) transmission system according to claim 2, is characterized in that: described low voltage isolation switch (23) comprises an isolating switch (QF1); Described isolating switch (QF1) is mechanical contactor, circuit breaker or electronic power switch device; When described low voltage isolation switch (23) is for photovoltaic booster converter fault, photovoltaic booster converter input side is disconnected.
5. photovoltaic HVDC (High Voltage Direct Current) transmission system according to claim 2, is characterized in that: described high_voltage isolation by-pass switch (25) comprises a fault isolator (QF2) and a switch failure by-pass (QF3); Described fault isolator (QF2) and switch failure by-pass (QF3) are mechanical contactor, circuit breaker or electronic power switch device; Described high_voltage isolation by-pass switch (25) for during photovoltaic booster converter fault by current transformer bypass, and form isolating points with high voltage power transmisson system.
6. photovoltaic HVDC (High Voltage Direct Current) transmission system according to claim 2, is characterized in that: described photovoltaic MPPT DC/DC converter (22) realizes the maximal power tracing function to photovoltaic module; For hicap, described photovoltaic MPPT DC/DC converter (22) is Boost topology, improves output dc voltage and reduces system loss; Described photovoltaic MPPT DC/DC converter (22) front end at least connects a road photovoltaic module, and when connecting multi-path light photovoltaic assembly, described photovoltaic MPPT DC/DC converter (22) comprises photovoltaic conflux module.
7. photovoltaic HVDC (High Voltage Direct Current) transmission system according to claim 2, is characterized in that: described photovoltaic booster converter is isolated topology and possesses boost capability, and the isolating transformer of described photovoltaic booster converter is withstand voltage should be DC transmission system maximum voltage; Described photovoltaic booster converter also comprises an inverter controller, for current transformer disorderly closedown, online drop into time transient process control current transformer operating state; Described photovoltaic booster converter is modularized design.
8. photovoltaic HVDC (High Voltage Direct Current) transmission system according to claim 1, it is characterized in that: described system controller (15) at least gathers high-voltage direct current power grid grid-connected current, after producing algorithm computing when normal operation according to unified duty ratio, export duty cycle signals to inverter controller, the current transformer of photovoltaic generation unit runs according to duty cycle signals, the current transformer of photovoltaic generation unit receives only duty cycle signals and does not run, and is in hot standby state.
9. photovoltaic HVDC (High Voltage Direct Current) transmission system according to claim 1, it is characterized in that: when the photovoltaic booster converter fault of a certain photovoltaic generation unit, system controller (15) sends control signal, the photovoltaic generation unit that bypass is broken down, and start the hot standby generator unit of photovoltaic, make its output voltage reach equal voltage levels, realize the Energy transmission to fault photovoltaic generation unit front end photovoltaic module; System controller (15) sends signal to the low voltage isolation switch of fault photovoltaic generation unit and high voltage isolator subsequently, is isolated by fault photovoltaic booster converter, carries out safeguarding or keeping in repair.
10. photovoltaic HVDC (High Voltage Direct Current) transmission system according to claim 1, it is characterized in that: the quantity of the hot standby generator unit of described photovoltaic is determined according to the quantity of photovoltaic generation unit and failure-frequency, failure-frequency height then photovoltaic after heat preparation electric unit quantity is many; The selection of photovoltaic input side interconnection cable cross-sections in parallel is relevant with the quantity of the hot standby generator unit of photovoltaic, the area of section of photovoltaic input side interconnection in parallel is determined jointly according to its maximum current flow through and interconnection cable type, and the maximum current flowing through photovoltaic input side interconnection in parallel during fault meets following formula:
Wherein P is the power of photovoltaic generation unit, and U is the voltage of photovoltaic input side interconnection in parallel, and m is the quantity of the hot standby generator unit of photovoltaic, flows through the maximum current of photovoltaic hot standby generator unit when I is fault.
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