Photovoltaic power generation is the second largest application field of SiC devices in addition to the field of new energy vehicles. As the conversion equipment of photovoltaic power station, the main role of photovoltaic inverter is to convert the direct current generated by solar cell modules into alternating current. As the photovoltaic industry enters the era of "large modules, large inverters, large span brackets, and large strings", the voltage level of photovoltaic power stations will be increased from 1000V to 1500V and above, which puts forward higher requirements for the physical properties of power devices, and silicon carbide has entered the public eye.
In photovoltaic power generation applications, although the cost of traditional inverters based on silicon-based devices accounts for about 10% of the system, it is one of the main sources of system energy loss. Compared with silicon-based IGBTs, SiC MOS has the advantages of lower conduction loss, lower switching loss, no current tailing, high switching speed, etc., and can work in harsh environments such as high temperatures, which is conducive to improving the service life of photovoltaic inverters. Based on the excellent performance of SiC, the application of SiC in the photovoltaic field is gradually maturing, and with the further improvement of permeability, it is expected to gradually replace the application of silicon-based IGBT in photovoltaic inverters.
As an important green power generation method, photovoltaic power generation has broad development prospects. In the future, with the acceleration of the replacement of traditional fuels by new energy, the development of inverters in the direction of high efficiency, high power density and high reliability, SiC power devices with the advantages of high power, high voltage resistance, high temperature resistance, high frequency and low energy consumption will also usher in new opportunities for development.
l1-10 kW for life applications
l100 W to 300 kW for commercial applications
l10-500 kW (2 MW~20 MW in the future) for utility systems
Merit:
1. Maximum Power Point Tracking (MPPT) function
Maximum Power Point Tracking (MPPT) is a core technology of PV inverters. Since the output power of a PV module varies with the intensity of solar radiation and the temperature of the module itself, there is an optimal operating point, the maximum power point (MPP). The function of MPPT is to make the photovoltaic module always work near the maximum power point, so as to maximize the power generation efficiency.In order to achieve MPPT, the PV inverter constantly detects the current and voltage changes of the PV module and adjusts the working state of the inverter according to these changes. Normally, MPPT is implemented through a DC/DC conversion circuit, and the PWM drive signal duty cycle of the DC/DC converter is adjusted so that the output of the PV module is always kept near the maximum power point.
2. Power grid monitoring function
The grid monitoring function enables the PV inverter to monitor the status of the grid in real time, including voltage, frequency, phase and other parameters to ensure the compatibility and stability of the PV power station with the grid. Through grid monitoring, the inverter can adjust its own output in real time to adapt to changes in the grid and ensure that the power quality meets the requirements of the grid. In addition, the power grid monitoring function can also help managers understand the operation status of the power grid, find and deal with potential problems in time, and ensure the stable operation of photovoltaic power plants.
3. Fault protection function
The PV inverter has a complete fault protection function to cope with various abnormal situations that may occur during actual use, and protect the inverter itself and other components of the system from damage. These failsafe features include:
Input under-voltage and over-voltage protection: When the input voltage is lower than or higher than a certain range of the rated voltage, the inverter will activate the protection mechanism to avoid damage to the equipment.
Overcurrent protection: When the working current exceeds a certain proportion of the rated current, the inverter will automatically cut off the circuit to prevent excessive current from causing damage to the equipment.
Output short-circuit protection: The inverter has a fast-response short-circuit protection function, which can be reversed after the short-circuit occurs-input reverse polarity protection: when the positive and negative poles of the input terminal are reversed, the inverter will start the protection mechanism to avoid the equipment being damaged by the reverse voltage.
Lightning protection: The inverter has a built-in lightning protection device, which can protect the equipment from lightning damage in lightning weather.
Over temperature protection: The inverter also has an over temperature protection function, when the internal temperature of the equipment is too high, it will automatically reduce the power or stop the machine to prevent the equipment from being damaged due to overheating.
Together, these fail-safe functions ensure the stable operation and safety of the PV inverter. In practical applications, the fault protection function of photovoltaic inverter is of great significance to improve the reliability and stability of photovoltaic power plants.
