National Semiconductor distributed MPPT to improve the efficiency of solar PV system

National Semiconductor distributed MPPT to improve the efficiency of solar PV system




This paper analyzes the solar photovoltaic system, solar panels as part of the electricity generated by the shielding and the problem of declining capacity, and introduced the board level in the battery using a distributed maximum power point tracking system (MPPT) advantages, but also on the use of technology in all SolarMagic kinds of case study results were discussed.



Solar energy is the most promising renewable energy sources. Since the introduction of incentive policies and traditions of the impact of rising electricity costs, more and more families are turning to solar energy, and the roof-mounted photovoltaic (PV) systems. PV systems at current prices, the user typically 7-8 years to get return on investment. Government incentives and the service life of PV system must be able to continue for 20 years or older. Solar PV systems return on investment depends on the annual capacity of the system, so users need to PV system must have efficient, reliable and easy maintenance features to get maximum generating capacity.



Today, many users who install solar PV systems have been realized in part or intermittent shelter will affect the system's generating capacity.



Part of the shadow mask of the solar PV systems:



When the trees, chimneys or other objects blocking the view projection of the shadow of PV systems, they will cause the system to result in a "mismatch" problem. Even if the PV system has only been obscured by the shadow of a little bit of generating capacity will lead to sharp decline. Part of the shelter system due to mismatch of the actual impact of electricity generation through a simple formula is difficult to obtain. Affect the system capacity because of many factors, including the internal battery module interconnects, module orientation, photovoltaic cells series-parallel connection between the two groups of issues and power inverter configurations. Photovoltaic modules interconnected by a number of battery strings formed, each battery string is called a "group out." Column for each group by a bypass diode to protect, so that one or more of the battery is obscured or damage cause the entire battery string were damaged because of overheating. The battery packs in series or in parallel columns can make solar panels have a relatively high voltage or current.



Photovoltaic arrays together by a series of photovoltaic modules by parallel composition. Each PV module string must be less than the maximum voltage inverter maximum input voltage rating.



When the PV system was partially obscured when the battery has not been sheltered in the current flowing through the masked part of the bypass diode.



When the PV array be obscured The occurrence of such situation, we will generate an electrical VP has more than one peak curve. Figure 1 shows the maximum power point with a centralized tracking system (MPPT) function of the standard grid configuration, in which a group of columns two panels have been obscured. Centralized MPPT DC voltage can not be set, so could not make out the output power of the two groups have reached maximum. The high DC voltage points (M1), MPPT so that the column is not obscured group reached the maximum output power. In the low DC voltage point (M2), MPPT group would shadowing the column reaches the maximum output power: Bypass diodes to bypass the shielding panels, this group is not shielded column panels will provide the full amount of current. MPP may result in multiple arrays to focus the maximum power point tracking (MPPT) to configure the additional losses as the maximum power point tracking device may get the wrong message to stop in the local maximum point, and stability characteristics of the times that have advantages of VP.