We need to refine the product selection of each link so that we can obtain the maximum investment income.
Through the understanding of some projects and years of experience, this paper discusses the selection of two core components (components and inverters) in the photovoltaic system.
Selection of components
The selection of components needs to consider two aspects: component appearance and electrical parameters;
You can't just look at the power that the component manufacturer promises, and the appearance of the component is also important for more than 25 years of service life.
1. Component appearance: class A component.
Industry generally for A and B (and C grade and other lower level) components division is not based on electrical parameters of the component but according to the appearance of the cell as well as packaging appearance to distinguish between the components.
Ⅰ, battery piece of bad appearance: brown spots, color difference, aluminum spines, beat, broken gate, node, graphics, migration, lack of Angle, the collapse edge, gap...
Ⅱ, components, packaging appearance bad: back failure, cell virtual welding, welding, sealing is not good, back scratch, border cut, cut, junction box packaging bad...
AM = 1.5;
1000 w / ㎡;
Under the condition of 25, there is no difference between the test and the electrical parameters, but it is difficult to guarantee the power generation and the service life of 25 years under the harsh conditions of outdoor use.
1. Electrical parameters:
Ⅰ, Pmax (maximum output power), FF fill factor, is the most intuitive for determining component conversion efficiency on the basis of:
Selection components of output power at the same time to consider the supply of the market, not to blindly pursue efficient components and reduces the choice and lose the price advantage, and certainly not to low efficiency of the component, and should choose the mainstream of the market can supply components.
In addition, when selecting components, it is necessary to consider the best working electrical parameters of the following inverter, which will lead to unnecessary power loss or waste.
Ⅱ, Voc open circuit voltage, Vmp maximum working voltage, short-circuit current, Isc Imp maximum working current, when used at the scene of the plant components series inverter best working voltage, parallel get per the maximum current of all the way, so as to let the current similar components in series, the voltage of similar components parallel of the child;
Because parallel of photovoltaic modules have "wooden barrel effect", the low performance of the component can lower performance good efficiency of the component, so we can't just only look at the so-called monolithic component output power, but to see the worst of the degree of the component is poor.
Selection of inverters.
The most mainstream debate about inverter today than a set of string type and centralized, each have each, also can not be partial to the negative or simple recognition, or need more user experience!
1, the set of string type inverter advantage: multi-channel Mppt tracking, easy single power points and shadows shade, adverse effects and bring the output of the component, and the single inverter power is smaller, the more obvious advantages, single fault is easy to repair;
Group of disadvantage: string type inverter in large power plant, because of the large quantity, thus increasing the operational time and energy, and installation costs (cables, communication junction box) relative to the centralized will be a little higher, if the whole set of string type inverter performance is not stable, for the overall operations of power station, power loss is great;
Applicable power stations: scattered roof power stations, uneven mountain power stations, beach power stations, shaded power stations, component arrays facing different power stations, agricultural greenhouse power stations...