SOLAR INVERTERS
According to the analysis using Huawei smart IV curve diagnosis technology, the major diodes of 33 PV strings are broken down. Replace the diodes that are broken down and the six PV modules with low efficiency.
SOLAR INVERTERS
O
& M for the Golmud PV plant of Huanghe showed that the PV modules often experience the faults of loosing, hot spots, glass breakage, and failure of diodes in the connection box. The inspection on PV modules is also a difficult for a large-scale PV plant. In the PV industry, PV modules are usually spot-checked. Assuming that the spot-check ratio is 0.1 %, a spot-check costs 40,000 RMB for a 10 MW PV plant. The low spot-check ratio is not good for evaluating a PV plant in a comprehensive way. Totally eight faulty PV modules are found in PV array 38 in zone 9 at Longyangxia plant. The number of faulty PV modules accounts for 0.17 % of the total number of PV modules in the PV array. However, there is a probability of only 2.4 % that faulty PV modules in the PV array will be spot-checked according to the spot-check ratio of 0.3 % of Huanghe. That is to say, faulty PV modules will not be spotchecked in a probability of 97.6 %. The traditional O & M method is not instructive.
In addition, O & M personnel have to take appropriate test tools, remove the PV modules, and check for faults one by one manually. This not only consumes time and labor, but also makes it impossible to locate faults in a short time. The current O & M method usually identifies PV module faults by comparing the output power, open-circuit voltage, short-circuit current, operating voltage, and operating current. The fault identification rate is low and misjudgment is likely to occur. For example, the first stage of 200 MW PV plant in Golmud contains 192 PV arrays, 816,612 PV modules of nine types, 3072 combiner boxes of six types, 384 inverters of nine types, 192 box-type step-up transformers of four types, about 50 thousand DC branches, and up to about 160,000 points for collecting data. So many devices bring challenges to safe production and management.
To solve the pain points exist in the traditional inspection way, Huawei and Huanghe Hydropower Development Co., Ltd. develop the smart IV curve diagnosis technology through joint innovation. Based on the inverter output IV curve, deploy algorithms on the management system and synchronize data analysis and mode recognition to scan all PV strings of a PV plant precisely in one-click mode and locate the root cause. The IV curve diagnosis technology helps determine device faults such as hot-spot effect on PV modules, loose connection, faulty PV string, reverse connection of PV strings, incorrect connection of PV strings, disconnection of certain PV strings, faulty combiner boxes, open circuits on combiner box branches, blown of fuses in combiner boxes, and inverter faults accurately and comprehensively in an all-round manner, which reduces the inspection strength greatly.
According to the analysis using Huawei smart IV curve diagnosis technology, the major diodes of 33 PV strings are broken down. Replace the diodes that are broken down and the six PV modules with low efficiency.
From the O & M experience on the 590 MW PV plant in Golmud of Huanghe, we know that we could not focus only on the cost when selecting PV devices, but should consider the LCOE over the 25 years of service life. After a PV plant is constructed and connects to the power grid, O & M becomes the work focus for the PV plant, directly relates to its longterm stable running, and is associated with the investment value and final benefits of the PV plant. Therefore, how to optimize the initial system investment and reduce the O & M cost to achieve optimal cost per kilowatt hour and pursue the lowest LCOE over the 25 years of lifetime is owners’ real goal.
66
EQ December 2016 www. EQMagPro. com