Design Ideas for Improving the Power Generation of Photovoltaic Power Plants
June is generally one of the best months of the year for power generation. The stable and efficient power generation of a power station is inseparable from a good power station design. The refined power station design includes equipment selection, component array design, sub-array wiring design, Cable layout design, etc. We share several factors that affect the power generation of photovoltaic power plants from the perspective of design, which can effectively improve the owner's income.
1. Use efficient components
High-efficiency components have the advantages of "more power, lower attenuation, and more reliability". High power and low decay rate improves power generation efficiency and service life.
2. Optimize the number of components in series and parallel
The number of PV modules in series should be calculated according to the following formula:
In the formula: Vdc max—the maximum allowable DC input voltage of the inverter (V)
Vmppt min—Inverter MPPT voltage minimum value (V)
Vmppt max—Inverter MPPT voltage maximum value (V)
Voc—PV module open circuit voltage (V)
Vpm—PV module working voltage (V)
Kv—PV module open circuit voltage temperature coefficient
K’v—temperature coefficient of operating voltage of photovoltaic modules
t'—the extreme maximum temperature under the working conditions of photovoltaic modules (℃)
t—the extreme minimum temperature under the working conditions of photovoltaic modules (℃)
N—Number of PV modules in series (N rounded up)
The maximum limit temperature of the project is considered to be 45°C, and the minimum limit temperature is considered to be -15°C. Combined with the parameters of the components (540Wp Voc=49.5VVmp=41.65V, voltage coefficient -0.27%), the upper limit of N is obtained: N≤20.
In the actual project, considering the high efficiency obtained in the full-load MPPT of the inverter, 16~18 modules are selected in series.
Note: * The temperature coefficient should be taken into account in the design.
* Know the efficiency curve and voltage-power curve of the inverter at different voltages and take into account if there are special circumstances.
1. Pay attention to the horizontal and vertical layout design of components
When the components are slightly occluded, the horizontal and vertical arrangement affects the output rate. Specific problems require specific calculations.
2. Optimizing Component String Wiring.
When the project group is connected in series, it is necessary to consider the position of the inverter and the connection circuit of the group string and adopt a method that saves more DC cables.
3. System capacity ratio design
Properly increasing the capacity ratio is conducive to improving the utilization rate of the equipment. The design requirements for the capacity ratio of the distributed power station are not particularly high and try not to cause the system to have a relatively large abandonment of light.
4. Optimized inverter access design
The application of high-power components causes some strings of the inverter to be unable to be fully connected. If the designed strings are allocated to as many MPPT channels as possible, it will not only reduce the influence of component mismatch but also maximize the power generation. Therefore, in addition to connecting a string facing or easily blocked to one MPPT in the traditional sense, because of the popularity of high-power components, the connection of all inverter MPPT channels is prioritized when connecting strings. Excess strings can be added to the sequence.
5. Inverter location design
In a distributed household scenario, the inverter is generally installed against a wall, and the inverter is selected near the grid connection point, eaves, and other places with less direct sunlight. At the same time, the inverter should be ventilated around it. It is forbidden to stack flammable items near the inverter. The height of the inverter is designed reasonably. Also, the inverter may be noisy, try to keep it away from the bedroom.
In industrial and commercial scenarios, the inverter is generally installed on the roof, and the way of anchoring is selected. The temperature of the roof is high, and the sunshade can be used to shade the inverter. Sufficient space should also be reserved around the inverter to dissipate heat to ensure the distance between the inverter and the inverter, especially the bottom space should be convenient for wiring.
6. Optimum cable selection
Cable selection generally considers the issues of current carrying capacity and line loss and voltage drop. Some industrial and commercial projects consider using aluminum cables or aluminum alloy cables to reduce costs, and at the same time consider the quality of copper-aluminum conversion construction.
From the design point of view, to improve the power generation of photovoltaic power plants, it is usually necessary to integrate multiple factors to optimize. In the end, the optimization of the cost of electricity is achieved, rather than the pursuit of one variable and the reduction of the overall system power generation caused by other factors. At the same time, as the core equipment of the conversion efficiency of the photovoltaic power generation system, the inverter should have a deep understanding of the inverter to ensure that the income of the system power station is at the highest value.
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