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  • Is the 1500Vdc photovoltaic system still far from large-scale applications?
    Time:2020-03-22 Browse:1423
    Is the 1500Vdc photovoltaic system still far from large-scale applications?
    Compared with the 1000Vdc photovoltaic system widely used in photovoltaic power stations, the research of 1500Vdc photovoltaic systems led by inverter manufacturers has recently become an industry technology hot spot.
    It's easy to have questions like this:
    Why raise the voltage from 1000Vdc to 1500Vdc?
    Except the inverter, can other electrical equipment withstand the high voltage of 1500Vdc?
    Is anyone using the 1500Vdc system now? How's the effect?
    I. Technical Advantages and Disadvantages of 1500Vdc Photovoltaic System
    1 Advantage Analysis
    1) Reduce the use of combiner boxes and DC cables. Each string of a 1000Vdc system is generally 22 components, while each string of a 1500VDC system can allow 32 components.
    Take a 265W module 1MW power generation unit as an example,
    1000Vdc system: 176 photovoltaic strings and 12 combiner boxes;
    1500Vdc system: 118 photovoltaic strings and 8 combiner boxes;
    Therefore, the amount of DC cables from photovoltaic modules to the combiner box is about 0.67 times, and the amount of DC cables from the combiner box to the inverter is about 0.5 times.
    2) Reduce DC line loss ∵P loss = I2R cable I = P / U
    ∴U increases by 1.5 times → I becomes (1 / 1.5) → P loss becomes 1 / 2.25
    In addition, the R cable = ρL / S, the L of the DC cable becomes 0.67, 0.5 times of the original
    ∴R cable (1500Vdc) <0.67R cable (1000Vdc)
    In summary, the 1500VdcP loss of the DC part is about 0.3 times of the 1000VdcP loss.
    3) Reduce a certain amount of engineering and failure rate
    As the number of DC cables and combiner boxes is reduced, the number of cable joints and combiner box wiring installed during construction will be reduced, and these two points are prone to failure. Therefore, 1500Vdc may reduce a certain failure rate.
    2 disadvantage analysis
    1) Increase in equipment requirements Compared with a 1000Vdc system, increasing the voltage to 1500Vdc has a significant impact on circuit breakers, fuses, lightning arresters and switching power supplies, and puts forward higher voltage and reliability requirements. improve.
    Linbai Electric has successfully developed 1500VDC fuses, 1500VDC circuit breakers, 1500VDC isolation switches, and 1500VDC surge protectors for the solar photovoltaic field, which are used in DC combiner boxes and power distribution cabinets in multiple 1500VDC solar photovoltaic systems.
    2) Higher safety requirements After the voltage is increased to 1500Vdc, the danger of electrical breakdown and discharge is increased, so that insulation protection and electrical clearance should be improved. In addition, if an accident occurs on the DC side, it will face a more serious DC arc extinguishing problem. Therefore, the 1500Vdc system raises the system's requirements for safety protection.
    3) Increasing the possible PID effect After the PV modules are connected in series, the leakage current formed between the high-voltage modules' cells and the ground is an important reason for the PID effect (for a detailed explanation, please reply to "103" in the background). After the voltage is increased from 1000Vdc to 1500Vdc, it is clear that the voltage difference between the battery chip and the ground will increase, which will increase the possibility of PID effect.
    4) Increasing matching loss There is a certain matching loss between photovoltaic strings, which is mainly caused by the following reasons:
    The factory power of different photovoltaic modules will have a deviation of 0 ~ 3%.
    Hidden cracks formed during transportation and installation will cause power deviation
    Uneven attenuation and uneven shielding after installation will also cause power deviation.
    In view of the above factors, increasing each string from 22 components to 32 components will obviously increase the matching loss.
    3 Comprehensive analysis In the above analysis, how much 1500Vdc can be compared with 1000Vdc can improve the cost performance, and further calculations are needed.
    Introduction: Compared with the 1000Vdc photovoltaic system widely used in photovoltaic power plants, the research of 1500Vdc photovoltaic systems led by inverter manufacturers has become an industry technology hotspot recently. Then we can easily have such questions.
    Second, the core equipment of photovoltaic system at 1500Vdc
    1Photovoltaic modules At present, FirstSolar, Artes, Trina, Yingli and other companies have launched 1500Vdc photovoltaic modules, including conventional modules and double glass modules.
    2 Inverter At present, mainstream manufacturers have launched 1500Vdc inverters with a capacity of 1MVA ~ 4MVA, which have been applied in demonstration power stations. The voltage level of 1500Vdc has been covered by the relevant IEC standards.
    3 Standards for combiner boxes and other key components Combiner boxes and key components have been prepared, and 1500Vdc has entered the combiner box certification standard CGC / GF037: 2014 "Technical Specifications for Photovoltaic Combined Equipment";
    1500Vdc has been clarified by most IEC standards as belonging to the category of low voltage directives, such as circuit breaker standards IEC61439-1 and IEC60439-1, photovoltaic special fuses IEC60269-6, and photovoltaic special lightning protection devices EN50539-11 / -12.
    However, since the 1500Vdc photovoltaic system is still in the demonstration stage and the market demand is limited, the above-mentioned equipment has not yet started mass production.
    Application of 1500Vdc photovoltaic system
    1: Macho Springs Solar Power Station
    Firstsolar announced in May 2014 that the first 1500Vdc power station completed in Deming, NewMexico was put into use. The total capacity of the power station is 52MW, 34 arrays use 1000Vdc structure, and the remaining arrays use 1500Vdc structure.
    SMA announced in July 2014 that its 3.2MW photovoltaic power plant in Sandershauser Bergindustrialpark, an industrial park in Niestetal, Kassel, northern Germany, has been put into use. The power plant uses a 1500Vdc system.
    2 Application cases in China
    Golmud Sunshine Qiheng New Energy Golmud 30MW Photovoltaic Project
    In January 2016, the first domestic 1500Vdc photovoltaic power generation system demonstration project, Golmud Sunshine Qiheng New Energy Golmud 30MW photovoltaic grid-connected power generation project, was officially connected to the grid for power generation, marking that the domestic 1500Vdc photovoltaic system has actually entered the actual demonstration application stage.