CN104113280B - Tandem photovoltaic square formation - Google Patents

Tandem photovoltaic square formation Download PDF

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CN104113280B
CN104113280B CN201410318954.7A CN201410318954A CN104113280B CN 104113280 B CN104113280 B CN 104113280B CN 201410318954 A CN201410318954 A CN 201410318954A CN 104113280 B CN104113280 B CN 104113280B
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photovoltaic
string
voltage
power
output
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CN104113280A (en
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王哲
许兰刚
定世攀
刘丽敏
王胜利
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BEIJING CORONA WEIYE TECHNOLOGY Co Ltd
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BEIJING CORONA WEIYE TECHNOLOGY Co Ltd
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    • Y02E10/00Energy generation through renewable energy sources
    • Y02E10/50Photovoltaic [PV] energy

Abstract

A kind of tandem photovoltaic square formation, it is characterised in that described photovoltaic arrays is made up of n photovoltaic group string power unit cascade, n > 1;Photovoltaic group string power cell is composed in series by photovoltaic group string and photovoltaic group string high_voltage isolation power conditioning module.The outfan of described photovoltaic group string is connected with the input of photovoltaic group string high_voltage isolation power conditioning module, export through this photovoltaic group string high_voltage isolation power conditioning module DC/DC isolated port, make the proof voltage > straight-flow system voltage Usmax of each photovoltaic group string power cell.

Description

Tandem photovoltaic square formation
Technical field
The present invention relates to the photovoltaic group string array of a kind of solar photovoltaic generation system.
Background technology
Current photovoltaic plant develops rapidly under the Policy Encouraging of country, and photovoltaic arrays is one of important composition of photovoltaic generating system, and the square formation amount of capacity being made up of photovoltaic group string connection in series-parallel directly affects the generated energy of system.Photovoltaic group string is to be composed in series by some pieces of photovoltaic modulies, and assembly is the minimum unit of group string, maximum 22 pieces of serial number, and it is pressure that its reason depends primarily on that assembly bears.Group string voltage≤1000V power after the series connection of current home and abroad assembly is maximum≤7kWp.For improving generating merit amount, two ways is adopted in current home and abroad: one is compose in parallel square formation in parallel by a large amount of photovoltaic group string to increase output electric current, improves square formation power output in parallel, through inverter inversion exchange output, the method is also referred to as centralized or parallel structure, as shown in Figure 4.Two is group serial type photovoltaic generating system as shown in Figure 5, adopt one group serial type inverter, many groups group string is directly inputted in group serial type inverter, first realize the independent MPPT MPPT maximum power point tracking of each photovoltaic group string, afterwards in parallel inverter exchange output, this type power is less.Confluxed cabinet parallel connection by exchange by multiple stage group serial type inverter again for increasing power further.Its essence of two types is all the parallel connection between group string, and voltage is low≤and 1000V, electric current is big, cable machinery loss is big, converging equipment is many, number of cables is many and inverter is the problems such as current mode topological structure power attenuation is big.Centralized or parallel then requirement group string performance parameter is close, group cannot be realized again and go here and there independent maximum power point (MPPT) and make power loss from motion tracking.Power station, distributed roof area is limit, must take into choice during for meeting each group of string voltage equal installation group string, cause limited area loss.
Have again, parallel-connection structure by photovoltaic group string is limit, and makes every optical crosstalk volt group connection in series-parallel output voltage improve according to grid-connected electric pressure, and the input that could meet inverter starts voltage primary condition, as, in 380v ac grid system, photovoltaic group string exports DC voltage >Startup inverter basic operating conditions could be met, start the obtained electricity of voltage height limited.
The same parallel-connection structure input direct voltage < 1000v by photovoltaic group string is limit, and can only meet inverter ac output voltage≤400v hierarchical system transless grid-connected, and higher voltage grade is grid-connected, must export through transformer boost.
Owing to inverter or DC equipment are divided into current mode or voltage-type in power electronic equipment topological structure, its feature: voltage-type voltage high current is little, and loss is little, and current mode voltage low current is big, loss is big.The parallel-connection structure of same still photovoltaic group string, photovoltaic group string output voltage < 1000v, electric current is big, adopts current mode topological structure inverter.
Thus many groups group string is improved output voltage drop low transmission electric current in series connection and increase power, meet that greater degree transless is grid-connected, make photovoltaic group string more low-voltage output energy be utilized, reduce cable and converging equipment quantity, adopt voltage-type topological structure inverter or DC equipment, realize reducing circuit, inverter or DC equipment loss, reduce cable, converging equipment, transformator cost, improve photovoltaic group string generating efficiency, adapt to distributed, large-sized photovoltaic power station and the demand of following middle and high voltage direct current transmission.
The boosting output of current photovoltaic system has three kinds of modes substantially, one for photovoltaic group string in parallel (square formation in parallel) through confluxing, the output of inverter ac transformer boost, mostly be centralized;Two conflux then through transformer boost output through inverter ac for photovoltaic group string is in parallel, mostly are group string data;Three export through DC/DC boosting through confluxing for volt group connection in series-parallel (square formation in parallel).Its essence still utilizes (parallel square formation) in parallel between a large amount of group string to improve photovoltaic arrays output.
Summary of the invention
The present invention seeks to overcome the shortcomings such as the method that existing utilization group connection in series-parallel improves generated output causes transmission line, corollary equipment loss serious, it is proposed to a kind of tandem photovoltaic square formation.The present invention utilizes the MPPT photovoltaic group string MPPT maximum power point tracking of photovoltaic group string high_voltage isolation power conditioning module, DC/DC, the features such as high_voltage isolation (isolation voltage > Usmax), each photovoltaic group string is carried out high_voltage isolation by photovoltaic group string high_voltage isolation power conditioning module, improve the isolation voltage grade of each photovoltaic group string, by connecting again between photovoltaic group string high_voltage isolation power conditioning module realization group string, improve inverter or DC equipment input voltage, reduce transmission electric current and increase generated output reduction loss, meet connecting again of different capacity photovoltaic group string power simultaneously, realize photovoltaic DC high-voltage transmission.
The present invention is by the following technical solutions:
Tandem photovoltaic square formation of the present invention is made up of n photovoltaic group string power unit cascade, n > 1.Photovoltaic group string power cell is composed in series by photovoltaic group string and photovoltaic group string high_voltage isolation power conditioning module.
In photovoltaic group string power cell, the outfan of described photovoltaic group string is connected with the input of photovoltaic group string high_voltage isolation power conditioning module, exports through this photovoltaic group string high_voltage isolation power conditioning module DC/DC isolated port.Photovoltaic group string high_voltage isolation power conditioning module has a communication interface, is used for connecting optical fiber or wireless communication module.The outfan of the outfan of this photovoltaic group string high_voltage isolation power conditioning module and communication interface also photovoltaic group string power cell and communication interface.Photovoltaic group string is through isolation voltage value that the magnitude of voltage of photovoltaic group string high_voltage isolation power conditioning module isolation and amplifier is photovoltaic group string power cell.This photovoltaic group string high_voltage isolation power conditioning module DC/DC isolated port output voltage Un is also the output voltage values of photovoltaic group string power cell.Due to the addition of photovoltaic group string high_voltage isolation power conditioning module, make the isolation voltage > Usmax of photovoltaic group string power cell.
Described Usmax is also referred to as straight-flow system voltage.Usmax=U1max+U2max+U3max ... ,+Unmax, U1max, U2max ..., Unmax is the maximum of each photovoltaic group string power cell output voltage in n photovoltaic group string power cell.Owing to n photovoltaic group string power unit cascade forms tandem photovoltaic square formation, the output electric current of its photovoltaic group string power cell is exactly that tandem photovoltaic square formation output electric current Is is also referred to as straight-flow system electric current.Straight-flow system is made up of the direct current importation in tandem photovoltaic square formation, DC equipment or inverter, and straight-flow system voltage is the nominal DC input voltage of inverter or DC equipment.
Described photovoltaic group string high_voltage isolation power conditioning module is made up of self-supply power source, MPPT photovoltaic group string maximum power point automatic tracking circuit, power conditioning circuitry, communication interface circuit, rectification circuit and high voltage isolating transformer.
The outfan of photovoltaic group string is connected with the input of photovoltaic group string high_voltage isolation power conditioning module.The input of photovoltaic group string high_voltage isolation power conditioning module is connected in parallel is formed by the input of self-supply power source and the input of MPPT photovoltaic group string maximum power point automatic tracking circuit;The outfan of MPPT photovoltaic group string maximum power point automatic tracking circuit is connected with the input of power conditioning circuitry, the outfan of power conditioning circuitry is connected with the input of high voltage isolating transformer, the outfan of high voltage isolating transformer is connected with the input of rectification circuit, the outfan of rectification circuit is the outfan of photovoltaic group string high_voltage isolation power conditioning module, also it is the outfan of photovoltaic group string power cell, the output of photovoltaic group string, finally after high voltage isolating transformer electrical isolation, is exported by rectification circuit direct current.The outfan of self-supply power source respectively with MPPT photovoltaic group string maximum power point automatic tracking circuit, power conditioning circuitry, communication interface circuit power supply input be connected, it is provided that each circuit work power.Namely photovoltaic group string output electricity provides photovoltaic group string high_voltage isolation power conditioning module power itself to need in part through self-supply power source, and substantial amounts of electricity is transported to inverter or DC equipment through MPPT photovoltaic group string maximum power point from the circuit such as motion tracking, equipment by another part.Communication interface circuit is a double-width grinding outputting communication interface circuit, one end of communication interface circuit is connected with power conditioning circuitry communication interface, the other end of communication interface circuit is connected with other photovoltaic group string power cells, inverter or DC equipment by wireless or optical fiber, the control command of inverter or DC equipment and data and each photovoltaic group string power cell is interacted.
Increase with irradiation intensity when the output of photovoltaic group string and increase, and when meeting photovoltaic group string high_voltage isolation power conditioning module inside self-supply power source startup output, self-supply power source output burning voltage provides working power for all circuit, starting the work of photovoltaic group string high_voltage isolation power conditioning module, photovoltaic group string high_voltage isolation power conditioning module is by its communication interface and inverter or DC equipment communication.Photovoltaic group string is carried out MPPT maximum power point tracking by MPPT photovoltaic group string maximum power point automatic tracking circuit in real time simultaneously, and the peak power input power of tracked photovoltaic group string is regulated in circuit, power conditioning circuitry coordinates with high voltage isolating transformer according to photovoltaic group string high_voltage isolation power conditioning module control strategy and inverter or DC equipment order, photovoltaic group string peak power is carried out pwm power adjustment, and the peak power of the photovoltaic group string after being adjusted is by exporting through rectification circuit direct current after high voltage isolating transformer electrical isolation.The electrical isolation voltage > straight-flow system voltage Usmax of high voltage isolating transformer, photovoltaic group string now, due to the electrical isolation of high voltage isolating transformer, makes each photovoltaic group string power cell can bear straight-flow system voltage Usmax.
The data such as the output voltage Un of photovoltaic group string high_voltage isolation power conditioning module, output electric current Is, maximum power point power, power adjustments output are interacted communication by wireless or optical fiber and inverter or DC equipment by the described communication interface circuit in photovoltaic group string high_voltage isolation power conditioning module, otherwise the control command of inverter or DC equipment and data carry out data interaction by this communication interface circuit and each photovoltaic group string power cell.
Described photovoltaic group string is composed in series by n block photovoltaic module.Photovoltaic module is the minimum generator unit of photovoltaic group string, the serial number of photovoltaic module depends primarily on the voltage that photovoltaic module bears, typical case's photovoltaic group string is composed in series with 20~22 pieces of photovoltaic modulies, the photovoltaic group string Control of Voltage after series connection≤1000V power maximum≤7kWp.
By photovoltaic group string power cell 1, photovoltaic group string power cell 2, photovoltaic group string power cell 3, ..., between the tandem photovoltaic square formation that photovoltaic group string power cell n is composed in series, annexation is: the output negative pole end of photovoltaic group string power cell 1 is connected with the output cathode end of photovoltaic group string power cell 2, the output negative pole end of photovoltaic group string power cell 2 is connected with the output cathode end of photovoltaic group string power cell 3, by that analogy, the output negative pole end of photovoltaic group string power cell n-1 is connected with the output cathode end of photovoltaic group string power cell n, n is positive integer, n > 1.The voltage of corresponding photovoltaic group string power cell 1 output be U1, photovoltaic group string power cell 2 output voltage be U2, photovoltaic group string power cell 3 output the voltage that voltage is U3, photovoltaic group string power cell n output be Un, all photovoltaic group string power unit cascade electric currents are Is, and series current Is is also tandem photovoltaic square formation output electric current.The communication interface of photovoltaic group string power cell 1 is connected with the communication interface of photovoltaic group string power cell 2, the like, the communication interface of photovoltaic group string power cell n-1 is connected to the communication interface n of photovoltaic group string power cell n.
The High voltage output anode that output cathode end is tandem photovoltaic square formation of photovoltaic group string power cell 1, the High voltage output negative terminal that output negative pole end is tandem photovoltaic square formation of photovoltaic group string power cell n.The voltage s of described tandem photovoltaic square formation output is each photovoltaic group string power cell output voltage sum, i.e. voltage s=voltage 1+ voltage 2+ voltage 3 ... voltage n.The power of photovoltaic group string power cell can differ, but output electric current is identical, and photovoltaic group string power cell series quantity can determine according to electrical network, inverter, distributed area requirements.After n photovoltaic group string power cell concatenation, output voltage values is Us, is that 500v, n=20 then Us=10000v is significantly larger than parallel photovoltaic group string 1000v as each photovoltaic group string power cell exports average voltage, improves electric pressure, increase power.
Operation principle and the work process of the present invention are as follows:
For improving photovoltaic arrays output, adopting photovoltaic group string series system is ideal means.But bear voltage < 1000v, as photovoltaic module voltage breakdown caused to damage series connection between photovoltaic group string, increases a high_voltage isolation link between each photovoltaic group string for this, improves the isolation voltage ability of photovoltaic group string owing to photovoltaic group string is the highest.The present invention exports after each photovoltaic group string is carried out high-voltage electrical apparatus isolation by photovoltaic group string high_voltage isolation power conditioning module, make the proof voltage > straight-flow system voltage Usmax of each photovoltaic group string power cell, it is achieved the series connection of n unit photovoltaic group string power cell.
Owing to the isolation voltage of photovoltaic group string power cell improves, the output voltage of n photovoltaic group string power unit cascade connection is tandem photovoltaic square formation output voltage Us, and tandem photovoltaic square formation output voltage Us is each photovoltaic group string power cell output voltage sum: U1+U2+U3+ ... Un=Us.Owing to the photovoltaic module parameter error in each photovoltaic group string power cell or a certain moment irradiation light group string quantity that is different or that form are different, making each photovoltaic group string power cell optimum output voltage Un after photovoltaic group string high_voltage isolation power conditioning module adjusts likely different, output electric current Is is equal for all photovoltaic group string power cells.If the power of photovoltaic group string power cell output can not meet photovoltaic group string high_voltage isolation power conditioning module minimum output power, photovoltaic group string power cell exits output, is namely output as short-circuit condition.Photovoltaic group string power cell is as follows with the process prescription that inverter or DC equipment cooperation work in different situations:
Under normal irradiation, after each photovoltaic group string power cell starts, first real-time tranception inverter or DC equipment communication data export low-voltage Unmin, output voltage sum U1min+U2min+U3min+ after n unit photovoltaic group string power unit cascade ... Unmin=Usmin, the i.e. minimum output supply voltage Usmin of tandem photovoltaic square formation.
The minimum output supply voltage Usmin of tandem photovoltaic square formation is also inverter or DC equipment direct current startup voltage.When Usmin meets inverter or DC equipment starts running voltage, each photovoltaic group string power cell has monitored electric current output simultaneously.Now the photovoltaic group string high_voltage isolation power conditioning module in each photovoltaic group string power cell calculates photovoltaic group string maximum power point automatically, and transmit photovoltaic group string peak power point data by communication interface to inverter or DC equipment, after inverter or DC equipment receive data, analyze all photovoltaic group string high_voltage isolation power conditioning module data, and providing each photovoltaic group string power cell optimum voltage value Un and equal output current value Is, each photovoltaic group string power cell is according to this voltage, current value output voltage and electric current.
Increase along with irradiation intensity or reduce, photovoltaic group string output in each photovoltaic group string power cell synchronizes to increase or reduce, detect through the photovoltaic group string high_voltage isolation power conditioning module of this photovoltaic group string power cell simultaneously, and to photovoltaic group string MPPT maximum power point tracking.The photovoltaic group string peak power point data of detection, calculating is uploaded in inverter or DC equipment through communication interface by photovoltaic group string high_voltage isolation power conditioning module, after inverter or DC equipment receive data, analyze all photovoltaic group string high_voltage isolation power conditioning module data, and providing each photovoltaic group string power cell optimum voltage value Un and identical currents value Is, every photovoltaic group string power cell is according to this voltage, current value output voltage and electric current.
When certain photovoltaic group string is by obnubilation, dust, fault affects output and reduces, or without irradiation, when photovoltaic group string is output as 0v, MPPT photovoltaic group string maximum power point automatic tracking circuit detection through the photovoltaic group string high_voltage isolation power conditioning module of this photovoltaic group string power cell, photovoltaic group string output can not meet photovoltaic group string high_voltage isolation power conditioning module minimum output power, when maybe cannot meet photovoltaic group string high_voltage isolation power conditioning module self-supply power source startup power, photovoltaic group string high_voltage isolation power conditioning module quits work, the rectified circuit direct output voltage 0v of high voltage isolating transformer, output impedance is 0 Ω, be equivalent to output short-circuit, do not affect other photovoltaic group string power cell outputs in tandem photovoltaic square formation.Now inverter or DC equipment can not receive the data of this photovoltaic power unit, but what inverter or DC equipment still can receive other normal operation photovoltaic group string power cell uploads data, inverter or DC equipment data according to this are analyzed calculating and send data to other photovoltaic group string power cells, providing photovoltaic group string power cell optimum voltage value Un and equal output current value Is, photovoltaic group string power cell is according to this voltage, current value output voltage and electric current.
Inverter or DC equipment orderly closedown under normal irradiation, or surprisingly quit work, or without communication, non-loaded or input disconnect time, photovoltaic group string high_voltage isolation power conditioning module in photovoltaic group string power cell monitors the communication data of inverter or DC equipment and the output electric current Is of photovoltaic group string power cell in real time, when communication data interrupts or exports the electric current Is operating current lower limit being reduced to inverter or DC equipment, photovoltaic group string high_voltage isolation power conditioning module quickly responds, at short notice (< 20ms) enter default security duty, i.e. output micropower pulse voltage < Unmin, monitoring photovoltaic group string power cell output electric current Is in real time.When monitoring photovoltaic group string power cell output electric current Is and reaching certain value, illustrate that inverter or DC equipment have accessed entrance and started SBR, set up communication contact, now photovoltaic group string power cell output voltage Unmin simultaneously.This process is used for detecting inverter or whether DC equipment accesses tandem photovoltaic square formation or work.
Due to photovoltaic group string power cell timing output micropower pulse voltage < the startup voltage of Unmin, tandem photovoltaic square formation output voltage after n photovoltaic group string power unit cascade is very low, less than voltage sum Usmin after n unit photovoltaic group string power unit cascade, and micropower output electric current is only small, avoid the big electric current of DC high voltage very well and draw arc phenomenon, solve the selection issue of high direct voltage General Electric, in other words namely normally or surprisingly quit work at inverter or DC equipment, or without communication, non-loaded or input off-state time, photovoltaic group string power cell fast reaction, at short notice (< 20ms) change default security duty, make the output low-voltage micropower pulse of group string data photovoltaic arrays, solve high direct voltage General Electric can be switched on or switched off by low-voltage small area analysis under having loading condition.
Coordinated and managed by inverter or DC equipment owing to each photovoltaic group string power cell of tandem photovoltaic square formation is unified, its photovoltaic group string power can be different, and photovoltaic group string power cell series quantity can be determined according to electrical network, inversion and DC equipment, power station area requirements.Thus photovoltaic group string exports through photovoltaic group string high_voltage isolation power conditioning module high_voltage isolation, the isolation voltage making photovoltaic group string power cell is greatly improved, so n photovoltaic group string power cell concatenation is possibly realized, improves electric pressure, add tandem photovoltaic square formation power.
The invention have the advantages that
1, tandem photovoltaic square formation can realize the output of mesohigh direct current, improves photovoltaic array power;
2, D.C. high voltage transmission cable loss reduces, it may be achieved remote Long line transmission;
3, tandem photovoltaic square formation is due to electric pressure improve, it may be achieved the transformerless output under this electric pressure, reduces loss, reduces cost.
4, relatively parallel photovoltaic arrays, tandem photovoltaic square formation can realize the less voltage output of each photovoltaic group string and start inverter or DC equipment.
5, in tandem photovoltaic square formation, each photovoltaic group string power cell is unified is coordinated and managed by contravariant equipment or DC equipment, possess best power and regulate output, the series connection of different capacity photovoltaic group string power cell can be realized, solve building roof photovoltaic plant owing to roof area difference mounting assembly power is inconsistent and fixing object periodically blocking assembly, can not mounting assembly problem, make full use of limited space realize power station generating maximize.
6, tandem photovoltaic square formation has been abandoned converging equipment and be substantially reduced fault rate, power attenuation and cost, particularly provide simple connected mode for the distributed power station of small-power.
7, owing to adopting modularity thinking to make convenient engineering installation, use reliably.
Accompanying drawing explanation
Fig. 1 is tandem photovoltaic square formation theory diagram;
Fig. 2 is tandem photovoltaic square formation electricity generation system block diagram;
Fig. 3 is that photovoltaic group string high_voltage isolation power conditioning module internal circuit connects block diagram;
Fig. 4 is the centralized photovoltaic generating system block diagram of prior art;
Fig. 5 is the group string data photovoltaic generating system block diagram of prior art.
Detailed description of the invention
The present invention is further illustrated below in conjunction with the drawings and specific embodiments.
Tandem photovoltaic square formation of the present invention is made up of n photovoltaic group string power unit cascade, is respectively as follows: photovoltaic group string power cell 1, photovoltaic group string power cell 2, photovoltaic group string power cell 3 ... photovoltaic group string power cell n.Photovoltaic group string power cell is composed in series by photovoltaic group string and photovoltaic group string high_voltage isolation power conditioning module.
The outfan of described photovoltaic group string is connected with the input of photovoltaic group string high_voltage isolation power conditioning module, exports through this photovoltaic group string high_voltage isolation power conditioning module DC/DC isolated port.
In photovoltaic group string power cell, outfan Vzn+, Vzn of photovoltaic group string is connected with photovoltaic group string high_voltage isolation power conditioning module input Vin+, Vin-respectively, the power of photovoltaic group string output exports through this module DC/DC isolation and amplifier port Von+, Von, and magnitude of voltage is Un.Due to the addition of photovoltaic group string high_voltage isolation power conditioning module, make the isolation voltage > Usmax of photovoltaic group string power cell.Each photovoltaic group string high_voltage isolation power conditioning module has a communication interface Tn, described communication interface Tn, and DC/DC isolation and amplifier port Von+, Von of this module are also communication interface and the outfans of photovoltaic group string power cell.Equally, the isolation voltage value of photovoltaic group string high_voltage isolation power conditioning module is also the isolation voltage value of photovoltaic group string power cell.Communication interface Tn can connect optical fiber or wireless communication module.
Described photovoltaic group string high_voltage isolation power conditioning module is made up of self-supply power source, MPPT photovoltaic group string maximum power point automatic tracking circuit, power conditioning circuitry, communication interface circuit, rectification circuit and high voltage isolating transformer.
The outfan of photovoltaic group string is connected with the input of photovoltaic group string high_voltage isolation power conditioning module.As it is shown on figure 3, the input of photovoltaic group string high_voltage isolation power conditioning module is composed in parallel by the input of self-supply power source and the input of MPPT photovoltaic group string maximum power point automatic tracking circuit.The outfan of MPPT photovoltaic group string maximum power point automatic tracking circuit is connected with the input of power conditioning circuitry, the outfan of power conditioning circuitry is connected with the input of high voltage isolating transformer, the outfan of high voltage isolating transformer is connected with the input of rectification circuit, the outfan of rectification circuit is exactly the outfan of photovoltaic group string high_voltage isolation power conditioning module, also it is the outfan of photovoltaic group string power cell, the output of photovoltaic group string is finally after high voltage isolating transformer electrical isolation, exported by rectification circuit direct current, realize the photovoltaic group string DC/DC isolation and amplifier through photovoltaic group string high_voltage isolation power conditioning module.
The outfan of self-supply power source respectively with MPPT photovoltaic group string maximum power point automatic tracking circuit, power conditioning circuitry, and communication interface circuit power supply input connect, it is provided that each circuit work power.
Communication interface circuit is a double-width grinding outputting communication interface circuit, one end of communication interface circuit is connected with power conditioning circuitry communication interface, the other end is also the communication interface of photovoltaic group string power cell, communication interface circuit is connected with other photovoltaic group string power cells, inverter or DC equipment by wireless or optical fiber, the control command of inverter or DC equipment and data and each photovoltaic group string power cell is interacted.
Photovoltaic group string is carried out MPPT maximum power point tracking by MPPT photovoltaic group string maximum power point automatic tracking circuit, it is achieved photovoltaic group string maximum power output.The maximum power output of photovoltaic group string coordinates with high voltage isolating transformer through power conditioning circuitry, carries out pwm power adjustment according to the order of control strategy and inverter or DC equipment, through high voltage isolating transformer, the output of rectification circuit direct current.The wherein isolation voltage > Usmax of high voltage isolating transformer, this photovoltaic group string and other photovoltaic group string are carried out electrical isolation by high voltage isolating transformer, so, it is possible to make each photovoltaic group string power cell can bear straight-flow system maximum voltage Usmax.Pwm power adjustment in photovoltaic group string high_voltage isolation power conditioning module, output voltage Un, output electric current Is carry out communication by communication interface circuit through wireless or optical fiber and other photovoltaic group string power cells, inverter or DC equipment, complete inverter or DC equipment and intercom mutually with tandem photovoltaic square formation.
Described straight-flow system maximum voltage Usmax=U1max+U2max+U3max ...+Unmax, U1max, U2max ... Unmax be photovoltaic group string power cell 1, photovoltaic group string power cell 2 to the maximum of each photovoltaic group string power cell output voltage of photovoltaic group string power cell n, and every piece of photovoltaic group string high_voltage isolation power conditioning module isolation voltage > Usmax.
Described photovoltaic group string is composed in series by some pieces of photovoltaic modulies, and the output port of photovoltaic group string is Vzn+, Vzn-.Described photovoltaic module is the minimum generator unit of photovoltaic group string, serial number depends primarily on the voltage that photovoltaic module bears, typical photovoltaic group string adopts 20~22 pieces of photovoltaic modulies to be composed in series, the group string Control of Voltage after photovoltaic module series connection≤1000V power maximum≤7kWp.
The output negative terminal Vo1 of photovoltaic group string power cell 1 is connected with photovoltaic group string power cell 2 output plus terminal Vo2+, the output negative terminal Vo2 of photovoltaic group string power cell 2 is connected with the output plus terminal Vo3+ of photovoltaic group string power cell 3, by that analogy, the output plus terminal Von+ of output negative terminal Von-1 and the photovoltaic group string power cell n of photovoltaic group string power cell n-1 is connected, n is positive integer, n > 1.
The output voltage of photovoltaic group string power cell 1 be U1, photovoltaic group string power cell 2 output voltage be U2, photovoltaic group string power cell 3 output voltage be U3 ..., the output voltage of photovoltaic group string power cell n is Un.Tandem photovoltaic square formation output electric current is Is, also referred to as system operating current.
The communication interface T1 of photovoltaic group string power cell 1 is connected with the communication interface T2 of photovoltaic group string power cell 2, the like.The communication interface Tn-1 of photovoltaic group string power cell n-1 is connected to the communication interface Tn of photovoltaic group string power cell n.High voltage output+the end that output Vo1+ is tandem photovoltaic square formation of photovoltaic group string power cell 1, High voltage output-the end that output Von is tandem photovoltaic square formation of photovoltaic group string power cell n, its High voltage output+, High voltage output-output voltage values be Us, Us=U1+U2+U3 ... Un.Photovoltaic group string power unit cascade quantity can according to electrical network, inverter, distributed area requirements.The tandem photovoltaic square formation output voltage values concatenated through multiple photovoltaic group string power cells is Us, it is 500v as each photovoltaic group string power cell exports average voltage, n=20 then Us=10000v is significantly larger than parallel photovoltaic group string 1000v, improves electric pressure, adds power.
Fig. 2 show the structure of tandem photovoltaic square formation of the present invention.Multiple photovoltaic modulies composition photovoltaic group string, the output correspondence often organizing photovoltaic group string connects a photovoltaic group string high_voltage isolation power conditioning module.Photovoltaic group string and photovoltaic group string high_voltage isolation power conditioning module are composed in series photovoltaic group string power cell.Photovoltaic group string 1 ..., photovoltaic group string n correspondence connects photovoltaic group string high_voltage isolation power conditioning module 1 ..., photovoltaic group string high_voltage isolation power conditioning module n, carry out group string high_voltage isolation power adjustments output through photovoltaic group string high_voltage isolation power conditioning module.The positive pole of photovoltaic group string high_voltage isolation power conditioning module 1 is connected with the input anode of inverter or DC equipment, the negative pole of photovoltaic group string high_voltage isolation power conditioning module n is connected with the input negative terminal of inverter or DC equipment, composition+, positive and negative DC series formula photovoltaic arrays.
Compared with the group serial type photovoltaic generating system shown in the concentrated photovoltaic generating system shown in Fig. 4, Fig. 5, the advantage of tandem photovoltaic square formation of the present invention is:
1, the tandem photovoltaic square formation shown in Fig. 2 do not have converging equipment, header box in concentrated photovoltaic generating system shown in Fig. 4, DC cabinet, exchange cabinet in group serial type photovoltaic generating system shown in Fig. 5 broadly falls into converging equipment, the different configuration of quantity of power is different, and break down rate height, loss of converging equipment is big in photovoltaic system.Tandem photovoltaic square formation of the present invention has abandoned a large amount of converging equipment, reduces loss, reduces cost, improves reliability;
2, in the tandem photovoltaic square formation shown in Fig. 2, photovoltaic group string is connected with photovoltaic group string high_voltage isolation power conditioning module nearby, all being connected in series by unit cable between the photovoltaic group string high_voltage isolation power conditioning module of Fig. 2, output electric current is a string photovoltaic group string electric current (current photovoltaic group string maximum short circuit current < 10A).And Fig. 4, in system shown in Fig. 5, converging equipment installation site must be taken into account many group photovoltaic group string and lay layout, cause n multiple-twin cable to converging equipment installation site in converging equipment in parallel, (as 16 road header boxs complete 16 tunnel photovoltaic group string parallel connections, number of cables is 16 × 2, its electric current that confluxes is 16 × 10A=160A, the exchange output of n platform group string inverter is through n × 4 piece ac cable parallel connection, the after current that confluxes increases n times, and converging equipment then through 2 direct currents or 4 AC great current cables in parallel in upper level converging equipment or inverter, compare the tandem photovoltaic square formation shown in Fig. 2, number of cables is greatly increased, and electric current is big, loss, cost increases;
3, tandem photovoltaic square formation shown in Fig. 2, the series connection that photovoltaic group string can be passed through between photovoltaic group string high_voltage isolation power conditioning module improves inverter or DC equipment input direct voltage, it is 500v as each photovoltaic group string power cell exports average voltage, 20 photovoltaic group string power cells, then inversion, DC equipment input voltage Us=20 × 500v=10000v can far above Fig. 4, inverter input voltage < 1000v shown in Fig. 5, make cascaded structure electric current reduce when Same Efficieney, change parallel heavy-current transmission current system, reduce the power attenuation of cable and equipment, and promote photovoltaic arrays power;
4, in the tandem photovoltaic square formation shown in Fig. 2, photovoltaic group string improves inverter or DC equipment input direct voltage by the series connection between photovoltaic group string high_voltage isolation power conditioning module, it may be achieved lower than input direct voltage/The grid-connected output of transless, and the photovoltaic generating system shown in Fig. 4, Fig. 5, restriction due to inverter input direct voltage < 1000v, inverter ac output voltage≤400v system transless can only be met grid-connected, higher voltage is grid-connected then must convert output through high-tension transformer, and electric current is big, loss is big, cost is high;
5, the tandem photovoltaic square formation in Fig. 2 is positive and negative 2 line direct current outputs, adopt two direct current cables of many groups in parallel when its equal output with the centralized photovoltaic generating system of Fig. 4, group string data photovoltaic generating system shown in Fig. 5 adopts many groups 3 phase 4 line ac cable output-parallels to compare, cable greatly reduces, and electric current is little, reduce cable loss.Tandem photovoltaic square array structure shown in Fig. 2+, direct current output, add the serial number of photovoltaic group string, improve direct current supply power;
6, in the tandem photovoltaic square formation shown in Fig. 2, photovoltaic group string is flexible by photovoltaic group string high_voltage isolation power conditioning module output voltage, photovoltaic group string series connection between photovoltaic group string high_voltage isolation power conditioning module under more low voltage condition can be made to improve output DC voltage, meet inversion, DC equipment starts voltage.And the photovoltaic generating system shown in Fig. 4, owing to the parallel-connection structure of photovoltaic group string is limit, making every optical crosstalk volt group connection in series-parallel output voltage improve according to grid-connected voltage, the input that could meet inverter starts voltage primary condition, as, in 380v ac grid system, photovoltaic group string exports DC voltageMore than could meet startup inverter work primary condition.
7, inverter or DC equipment are divided into current mode or voltage-type in power electronic equipment topological structure, its feature: voltage-type voltage high current is little, and loss is little, and current mode voltage low current is big, and loss is big.Tandem photovoltaic square formation shown in Fig. 2 adopts cascaded structure, and inverter or DC equipment input current are little, make every piece of adjustment module autophage power little of fanning heat treatment.Same employing tandem photovoltaic square formation, inverter or DC equipment input voltage height electric current are little, and voltage-type topological structure inverter or DC equipment power consumption should be adopted little.And the photovoltaic generating system shown in Fig. 4 adopts parallel-connection structure, output voltage < 1000v due to photovoltaic group string, electric current is big, adopt current mode topological structure inverter, comparing the voltage-type inversion in the tandem photovoltaic square formation of Fig. 2, DC equipment, power attenuation is big, and efficiency is low.

Claims (2)

1. a tandem photovoltaic square formation, described photovoltaic arrays is made up of n photovoltaic group string power unit cascade, n > 1;Photovoltaic group string power cell is composed in series by photovoltaic group string and photovoltaic group string high_voltage isolation power conditioning module;The outfan of described photovoltaic group string is connected with the input of photovoltaic group string high_voltage isolation power conditioning module, exports through this photovoltaic group string high_voltage isolation power conditioning module DC/DC isolated port,
It is characterized in that, described photovoltaic group string high_voltage isolation power conditioning module is made up of self-supply power source, MPPT photovoltaic group string maximum power point automatic tracking circuit, power conditioning circuitry, communication interface circuit, rectification circuit and high voltage isolating transformer;
The outfan of photovoltaic group string is connected with the input of photovoltaic group string high_voltage isolation power conditioning module;The input of photovoltaic group string high_voltage isolation power conditioning module is connected in parallel is formed by the input of self-supply power source and the input of MPPT photovoltaic group string maximum power point automatic tracking circuit;The outfan of MPPT photovoltaic group string maximum power point automatic tracking circuit is connected with the input of power conditioning circuitry, the outfan of power conditioning circuitry is connected with the input of high voltage isolating transformer, the outfan of high voltage isolating transformer is connected with the input of rectification circuit, the outfan of rectification circuit is the outfan of photovoltaic group string high_voltage isolation power conditioning module, is also the outfan of photovoltaic group string power cell;The output of photovoltaic group string, finally after high voltage isolating transformer electrical isolation, is exported by rectification circuit direct current;The outfan of self-supply power source respectively with MPPT photovoltaic group string maximum power point automatic tracking circuit, power conditioning circuitry, and communication interface circuit power supply input connect, it is provided that each circuit work power;
Communication interface circuit is a double-width grinding outputting communication interface circuit, one end of communication interface circuit is connected with power conditioning circuitry communication interface, the other end of communication interface circuit is connected with other photovoltaic group string power cells, inverter or DC equipment by wireless or optical fiber, the control command of inverter or DC equipment and data and each photovoltaic group string power cell is interacted.
2. the tandem photovoltaic square formation described in claim 1, it is characterized in that, each described photovoltaic group string exports after carrying out high-voltage electrical apparatus isolation by photovoltaic group string high_voltage isolation power conditioning module, makes the proof voltage > straight-flow system voltage Usmax of each photovoltaic group string power cell.
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