Application of photovoltaic system technology

With the rapid development of the global economy, there has been a corresponding advancement in new energy power generation technology. Among the various renewable energy sources, solar energy has emerged as one of the most promising options due to its abundant and widely available resources. Since the turn of the 21st century, the solar photovoltaic power generation industry has witnessed a rapid growth worldwide. Its market application scale has continuously expanded, thereby assuming an increasingly crucial role in the future of energy development.

 

In the context of China, the development and utilization of solar photovoltaic technology holds significant importance. It serves as a crucial tool in the implementation of a resource-saving society, energy conservation, emission reduction, sustainable development, and enhancement of the living environment. This technology aligns perfectly with the country's goals in these areas.

 

Presently, the global energy resources are dwindling, and environmental issues are becoming more pressing than ever. Under such circumstances, the rational and effective utilization of renewable energy has emerged as a crucial concern in the quest for building a conservation-oriented society.

 

When connecting a photovoltaic inverter power to the grid in order to operate, it functions essentially as a source of electric current. It is important to note this aspect of its operation when planning and implementing its use.

 

The major challenges in the operation of photovoltaic power grid connection lie in effectively controlling the output current and minimizing harmonic pollution to the power grid, while also ensuring the same frequency and phase as the grid voltage. Grid connection technology relies heavily on inverters, which act as the central devices in the connection system. Therefore, the control and modulation technology used in inverters play a crucial role in achieving successful grid connection. Extensive research on photovoltaic grid connected systems has been conducted both at the domestic and international level. Grid connection can be viewed as a parallel connection to the power grid, and by implementing controlled inverters, grid connection can be achieved without causing any adverse impact.

 

In photovoltaic systems, inverters require a flexible and reliable control mechanism to ensure optimal performance. Current and voltage tracking-based PWM control strategies have been used in the past, with the primary focus on reducing harmonic content and improving output power quality. However, a new approach based on current control has recently emerged, which incorporates power tracking capabilities. This new strategy brings several benefits, including enhanced control over the inverter's output and efficient power management. Overall, the use of PWM modulation control strategies is critical in photovoltaic systems, as they ensure optimal performance and improved power quality.

 

Grid-connected inverters currently employ a control mechanism where the inverter output functions as the current source. In this setup, the parallel operation of the inverter with the power grid can be perceived as the parallel operation of a current source and a voltage source. When the inverter is connected to the grid, parallel operation is achieved by regulating the output current frequency and ensuring that it tracks any changes in the grid voltage. By doing so, a seamless connection between the inverter and the grid is established.

 

There are several widely used control strategies for keeping track of the current, such as triangular wave comparison control, instantaneous hysteresis control, and deadbeat control. These strategies play a significant role in regulating and monitoring the current flow. It is important to note that the choice of control strategy depends on specific requirements and circumstances. With these control techniques, ensuring accurate current tracking becomes feasible, allowing for efficient and reliable operation.