Basic Principles of Solar Photovoltaic Power Generation

The principle of solar cell power generation is based on the photovoltaic effect that occurs when light is incident on a semiconductor material. The basic characteristics of a photovoltaic cell are similar to those of a diode and can be explained using a simple PN junction. When a photon with sufficient energy is incident on the semiconductor, electrons and holes (positively charged carriers resulting from the loss of electrons) are generated through the interaction of light with the semiconductor material. If a PN junction exists in the semiconductor, electrons diffuse to the N-type semiconductor and holes to the P-type semiconductor, accumulating at the two electrode parts, i.e., negative and positive charges accumulate at the two ends. If these two electrodes are connected with a wire, a charge flow is generated to produce electrical energy. By using this principle, solar energy can be converted into electrical energy and stored. Through adjustment and control techniques, the electrical energy can be transformed into various required standards to meet the needs of different loads. This is completely different from traditional power generation methods, as it does not have rotating parts or emit gas, and is a clean and noiseless form of power generation.

Depending on the application, photovoltaic power generation systems can generally be divided into independent photovoltaic power generation systems, grid-connected photovoltaic power generation systems, and hybrid photovoltaic power generation systems. The solar inverter power supply designed in this study mainly focuses on independent photovoltaic power generation systems. As shown in the figure below, a photovoltaic power generation system mainly includes solar panels, chargers, batteries, controllers, DC boost circuits, inverters, and solar automatic trackers.

A typical photovoltaic power generation system consists of four parts: a photovoltaic cell array, an energy storage system, an inverter, and a DC control system. The photovoltaic cell array generates a small amount of DC power from a single photovoltaic cell, and in order to meet practical application needs and obtain a sufficient amount of power generation, single photovoltaic cells are connected into a battery group, which then forms a solar photovoltaic array. The energy storage system stores the electricity generated by the photovoltaic power generation system during the day for use when needed. The inverter is used to convert the DC power generated by the photovoltaic cell array into the AC power required for practical application. The efficiency of the inverter system directly affects the efficiency of the entire system. The DC control system is used to adjust, protect, and control the entire transmission and exchange process of electrical energy from the photovoltaic array to the storage unit and then to the inverter unit, to maintain the high efficiency and safe operation of the system.

When the sunlight is strong, the low-voltage DC power generated by the solar cell directly provides power to the DC boost circuit, which charges the battery through the charger for energy storage. When the sunlight is weak, the power output of the solar cell cannot meet the requirements of photovoltaic power generation. At this time, the battery, serving as the energy storage device, provides low-voltage DC power to the DC boost circuit, ensuring the continuity and stability of the photovoltaic power generation system. The DC boost circuit raises the low-voltage DC power to high-voltage DC power of 330V, which is then converted to 50Hz/220V AC power through the inverter. The output AC voltage and current are fed back to the controller through a detection circuit, and the controller can implement closed-loop control. The solar automatic tracking system makes the solar panel follow the movement of the sun, fully utilizing solar energy and improving the efficiency of the photovoltaic power generation system.