String inverters are suitable for small and medium rooftop photovoltaic power generation systems and small ground power stations. The photovoltaic power station system applying the string inverter includes components, DC cables, inverters, AC power distribution, and power grids. PowMr is one of the top sellers of the best string inverters, if you don't understand anything, you can ask online customer service.
String inverter advantages:
- The network structure of the string inverter is simple, and it can be installed outdoors and nearby. Select the appropriate inverter flexibly according to the roof capacity, make full use of the roof area, and increase the investment income.
- The type of equipment is simple, saving investment. DC combiner boxes, DC power distribution cabinets, isolation transformers, machine rooms, and related civil works can all be omitted while reducing the difficulty of on-site construction organization and shortening the construction period. Comprehensive calculations show that the civil construction workload of the string inverter system is only 1/4 of that of the centralized inverter system; in terms of safety and reliability, it avoids the risk that the DC side of the traditional centralized solution cannot be extinguished.
- The inconsistency of components has little impact on the power generation, the inverter self-consumption is less, and the self-consumption power of the string type is 20W, which is only 1.3% of the centralized type. According to the test of the actual project, the system efficiency of the string-type scheme is About 5% higher than the centralized solution.
- Each inverter has 3 independent MPPTs, which track each channel independently, with little impact on single-channel failure, refined management of the output of each battery panel, and high power generation in the whole system. In the event of partial occlusion, partial contamination (such as bird droppings), and partial failure, in addition to the influence of the power generation of the affected part, the rest can still guarantee the maximum power output.
- The string inverter does not require maintenance by professional engineers, the equipment is modular, and the on-site installation and debugging are simple. The replacement of an inverter can be completed in 20 minutes, without the need for professionals to be on duty, and realize "fool-style" maintenance; a single inverter The influence of inverter failure on power generation is low, and the system reliability and annual availability rate are high, and the annual inverter failure rate is less than 0.5%.
- Each inverter can realize intelligent monitoring of 6 strings, reduce fault location time by 80%, independently detect the voltage and current of each input, sample string current and voltage in real-time, and find line faults and component faults in time, occlusion, etc. Through the horizontal comparison of strings, comparison of meteorological conditions, comparison of historical data, etc., the detection accuracy is improved. In addition, it can cooperate with the background network management to provide automatic operation and maintenance suggestions, such as cleaning, string matching optimization, inverter coordination, etc.
- The MPPT voltage range of the string inverter is wide, generally 250-800V, and the component configuration is more flexible. On cloudy and rainy days, in areas with a lot of fog, the power generation time is long.
- The inverter is maintenance-free, naturally dissipating heat (fanless design - Huawei is currently doing more in this regard), has low self-power consumption, IP65, and can operate reliably in the rain, sand, and salt spray environments; PowMr is selling The body of the string inverter adopts an all-aluminum one-piece enclosed shell, and no external fan design (this is very important, the external fan is one of the most prone to failure and corrosion in the inverter), the inverter The outer casing of the radiator is sprayed with a high weather-resistant outdoor coating for protection, the radiator adopts a thickened anodizing process, and all installation parts are made of corrosion-resistant materials such as stainless steel, which truly realizes IP65 protection, thus meeting the application in salt spray and high humidity environments.
Disadvantages of string inverters:
- There are many electronic components, power devices, and signal circuits on the same board, which is difficult to design and manufacture, and the reliability is slightly poor.
- The electrical clearance of power devices is small, which is not suitable for high-altitude areas. Outdoor installation, wind, and sun exposure can easily lead to aging of the casing and heat sink.
- There are no DC circuit breakers, AC circuit breakers, and no DC fuses. When the system fails, it is not easy to disconnect, and the short circuit of the component strings will cause serious accidents.
- A single inverter can realize the zero-voltage ride-through function, but when multiple inverters are connected in parallel, it is difficult to realize the zero-voltage ride-through function, reactive power regulation, active power regulation and other functions.
- A 10MW power station needs 300-400 string inverters. According to the theory of electrical power supply reliability, the power station failure rate is more than 10 times that of a 500KW inverter.
- 6. The larger the scale of the string power station, the more communication nodes, and the comprehensive relay protection system needs to be redesigned.
- The string inverter can only run at full capacity under the condition of an ambient temperature of 4CTC, and the derating will be reduced by 5% for every 10°C rises. The 500KW inverter can operate at an ambient temperature of 55°C: 1: 1.1 Full operation.