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Several correct cognition about group series inverter

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  The erroneous zone one, the group of series connection plan, each MW photovoltaic power station needs to be carried on to the up to 40 inverters to carry on the operation, is very complex, is not advantageous to the power station long-distance dispatch management.
  Positive solutions: remote control of the power station, is completed by remote communication mode, the power plant is now, centralized monitoring; string inverters accept commands and actions are consistent; can be a single operation, can press the line and operate separately, can also be full of gymnastics, there is no complex scheduling the problem.
  Error two, negative electrode grounding is currently recognized as the most reliable solution to suppress the PID effect. For string inverters, usually using the virtual cathode grounding circuit to suppress the PID effect, such as virtual circuit fault string inverters are unable to protect the inhibition of the PID effect, than the solid cathode grounding reliability.
  Positive solution: basically centralized inverter can not be done to the solid anode grounding.
  Group of virtual cathode grounding fault occurs, there will be alarm information to remind the operation and maintenance personnel to check.
  Is very important for plant protection, in zone three large ground station in fault, either by software or hardware protection protection, require the inverter can reliable operation when a fault occurs, the protection of the safe operation of power station. But for the DC DC circuit breaker switch rather than string inverters, if the ground fault occurs in DC, DC switch without breaking capacity, can not be DC fault cut off, resulting in the lack of hardware protection function.
  Positive solutions: String inverters are using the DC side of the switch, but the internal diode, relay device, limit current, anti breaking and AC and DC side effects, a hardware protection function; series inverter DC line is short, can reduce the DC arc, and can accurately detect current each series of components, DC grounding fault occurs, the machine will alarm can remind maintenance personnel check processing.
  Also features panels also decided that the short-circuit current and the actual current battery pack difference; circuit breaker centralized inverter selection, the basic existence of misoperation or not correct operation problems; centralized inverter, DC go long, must also be equipped with a junction box, DC cabinet and other equipment, line growth, equipment the increase will inevitably lead to failure of centralized inverter scheme of DC side rate; probability of occurrence of DC arc and ground fault will be greatly improved.
  Four, the series inverter is not suitable for large ground stations, not for the owners to bring the power generation and income.
Positive solutions: there is no theoretical basis that string inverters are not suitable for large ground station; instead many large foreign ground stations are taken on the domestic inverter group; HUAWEI group string type inverter is also applied to a number of large power plants, our string inverters are also used in Australia, Xinjiang and other large ground station the amount of data; from the power feedback to the owners, string inverters average generating capacity than centralized 3%-5%.
  Five, according to the calculation errors of 100MW power plant, a total of 4000 sets of string inverters, manufacturers need to provide the standby inverter number 10, the proportion was only 0.25%, but because of the large number of components series inverter, inverter topology and complex failure rate is much higher than the 0.25%.
  Positive solutions: effects of the failure rate is the amount of power generation and maintenance costs, because the string inverter power plant through simple maintenance and operation of the field of data comparison, in fact the string inverter average generating capacity than centralized high maintenance costs than centralized low. And 0.25% of the proportion of goods come from? The general group of string inverter manufacturers stocking ratio can reach 1%; 1000MW ground station, using 40KW series inverter, only 2500 Taiwan; another group of string inverter as a single replacement time up to half an hour, the power unit of generator small, recovery time is short; minimal power loss of the centralized inverter, need professional maintenance, if the inverter manufacturers do not at the scene, the waiting time for at least 48 hours, power unit power is big, caused by the loss of power is very big.
  Error six, large ground stations located in desert and Gobi, underdeveloped logistics, even if the string type manufacturers commitment in the warranty period by the manufacturer sent home recovery fault inverter, but in after the warranty period the customer is required by the inverter through the logistics transport to the designated address, for customers to say need to single 55kg inverter handling to logistics pick-up points, will increase the workload of customers.
Positive solution: logistics is not a problem, and now the logistics can be door-to-door collection;
  And is it just a series of inverter fault machines need to deal with it, the centralized inverter power module is also vulnerable to 25-30Kg, there are also transport problems.
  Error seven, large ground station area is usually larger, some power plant site road conditions are poor, special terrain, resulting in a lot of inconvenience to the site maintenance. Especially in the mountainous and hilly power station, the road condition is poor, the operation and maintenance personnel can not be directly transported to the fault point of the serial inverter to replace, time-consuming and laborious, the impact of power plant maintenance efficiency.
  Positive solutions: large ground station during the installation process will line plan, according to local conditions to the formation of land; these work on line laying, impact bracket and component installation; power plant construction process, assembly and frame can be transported in place, the inverter can also transport in place.
  In addition, the centralized inverter scheme needs to take the bus, the bus is also distributed in the distribution, and the failure rate is higher than the inverter, also need to transport.
  Error eight, string inverters replacement machine maintenance and its maintenance cost is much higher than to centralized inverter especially in the warranty period, after the string inverter maintenance costs will be in operation cost in power plant is not a small proportion. From the point of view of the life of components, the switching power supply, the life of aluminum electrolytic capacitor is the shortest, and more than 5 years ~8 years, the series inverter is required to replace the whole machine.
  Positive solutions: String inverters are used in thin film capacitors, with a life span of 15 years, the general staff can complete the replacement; on the contrary, centralized inverter is basically adopt electrolytic capacitors, short service life, and centralized inverter professional, compared to centralized operation and maintenance costs will be higher.
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