Solar inverter is a key component of the entire solar power generation system. It converts the variable DC voltage output of the photovoltaic unit into a clean 50Hz or 60Hz sinusoidal voltage source, thereby supplying power to the commercial power grid or the local power grid. Because the solar panel's photoelectric conversion efficiency may be affected by the angle of sunlight, clouds, shadows, or climatic conditions, the solar power system must convert the constantly changing DC power into a well-adjusted AC power source. The maximum output power of the rechargeable battery should appear at the peak of the voltage and current product of the photovoltaic cell. In order to achieve the maximum power point output tracking (MPPT), the microcontroller must run the MPPT algorithm to adjust the direction of the solar panel, the output DC voltage and current, so that it can obtain the peak power output, you need to use a microcontroller and sensors To track the sun's azimuth and altitude. At present, in the tracking system of adaptive solar azimuth, altitude and radiation intensity, the components include radiation intensity sensor, tracking sensor, automatic control chip, stepper motor and subdivision driver, mechanical transmission mechanism and energy gathering platform, etc. section. For the wind / solar integrated power generation system, the output voltage / current of the photovoltaic array, tracking light intensity, ambient light intensity, battery charging current / voltage, inverter output AC current, AC voltage, ambient temperature, battery Temperature, photovoltaic array temperature, solar azimuth, altitude angle and wind speed. Therefore, high requirements are placed on the data acquisition capability of the microcontroller and A / D conversion and processing. In large-scale deployment of solar grid-connected power plants, the number of photovoltaic panels is very large. For this reason, TI has proposed the concept of "micro inverter", which can scan individual solar energy in a wide range The peak power point of the battery board avoids the local peak value as the MPP point, and at the same time, it can improve the efficiency of output tracking at the maximum power point. The architecture of such a system proposed by TI is shown in the figure. It can be seen from the above that the demand for DC / DC converters, DC / AC converters, controllers and communication interfaces is also very large. The characteristic of the micro inverter is that each photovoltaic panel has its own independent inverter system. The main benefit of this topology is that the photovoltaic array of the solar power station can continuously output power, even when one of the inverter functions Abnormal times. In addition, because each solar system can use high-resolution PWM algorithm to adjust the conversion parameters, so that the system can be adjusted at any time according to the load changes, and the use of on-chip peripherals such as SPI, UART and other interfaces to achieve each micro inverter Therefore, it is possible to provide the most optimized conversion efficiency for each photovoltaic panel and the entire power plant system. At present, the Piccolo MCU launched by TI is designed to provide higher efficiency and control functions for solar panels. The micro-inverter can maximize the power output of each single panel. The principles for choosing a microcontroller for a solar inverter include: low cost targets to meet the needs of a large number of deployments; small form factor; complete control functions; the ability to achieve data exchange with the controller of each micro inverter; powerful Parallel computing capability; interface with analog devices such as current and voltage sensors to achieve real-time monitoring of system peak power; built-in A / D converter; solar ground leakage current detection capability; the ability to control the solar panel steering motor. Power device for solar inverter In the design of solar inverters, commonly used IGBTs are planar IGBTs and channel IGBTs. In planar IGBTs, polysilicon gates are distributed in a "planar" or horizontal distribution relative to the p + body region. In a channel IGBT, the polysilicon gate enters the p + body region in a "channel way down". This structure has the advantage that it can reduce the resistance of the channel to the flow of electrons and eliminate the current crowding phenomenon, because at this time electrons flow vertically in the channel. In a planar IGBT, electrons enter the channel at a certain angle, causing current crowding, thereby increasing the resistance of electron flow. In the channel type IGBT, the enhancement of electron flow greatly reduces Vce (on). In addition to reducing Vce (on), switching energy can be reduced by changing the IGBT to a thinner structure. The thinner the structure, the faster the hole-electron recombination speed, which reduces the tail current when the IGBT is turned off. In order to maintain the same ability to withstand breakdown voltage, an n-field stop layer is constructed in the channel IGBT to prevent the electric field from reaching the collector region when the voltage on the IGBT increases. The lower conduction energy and switching energy achieved in this way allow the inverter to be smaller in size, or the power density of inverters of the same size to be larger. In solar power systems, solar panels need to work in series or parallel. The DC voltage generated by the solar module is in the order of hundreds of volts, such as 600V or 1200V. The above-mentioned latest IGBT technology makes the latest generation of 600V channel IGBTs for 20kHz switching applications Was realized. Taking IR company's 500W DC / AC inverter demo board built with a full-bridge topology as an example, the measured power consumption reduction shows that the use of a new optimized channel IGBT device can reduce the heat sink temperature by 16%. The reduction in power consumption has increased the efficiency of the IGBT by nearly 30% compared to the previous generation of IGBT devices. In general, in the design of DC / AC inverter systems, the basic criteria for selecting IGBT devices are to improve the conversion efficiency, reduce the size of the system heat sink, and increase the current density on the same circuit board. At present, many companies on the market provide power devices for solar inverters, including IR, Infineon, ST, Fairchild Semiconductor, Vishay, Microsemi, Toshiba and other companies. Typical grid-connected power generation system Although the solar energy resources are endless, the solar energy reaching 800,000 kilowatts per second on the surface of the earth, however, because the solar radiation density is too low, the conversion efficiency of solar cells is very low. The efficiency of a solar inverter that converts direct current into alternating current is very important for improving the efficiency of solar power generation. High-efficiency and cost-effective inverters have become key indicators for evaluating the merits of solar power generation systems. The key to future development and the focus of competition is to improve the photoelectric conversion efficiency. Experts predict that the market for three-phase central inverter systems is expected to have very good market performance in the next five years due to the stimulus from the deployment of large-scale solar power plants. From the perspective of technology trends, inverter expert J. Vanden KeyBus of TriphaseNV pointed out that the future three-phase inverter will be composed of inverter control unit, IGBT inverter, PWM generator, ADC, dead zone protection circuit, Ethernet , Networked personal computer and other components, as shown in Figure 3. The purpose of constructing such a system is to realize the grid-connected solar battery pack to supply power to the grid, and to achieve the highest efficiency of solar grid-connected power generation by tracking the peak power point by means of networked control. The solar grid-connected power generation system will generate huge demand for the following systems and devices: 1) Grid management network system; 2) Ethernet port; 3) AD converter; 4) PWM generator; 5) inverter controller; 6) IGBT module and inverter; 7) solar panel azimuth and Altitude steering motor and its control device; From the point of view of power discrete devices, with the increase in the scale of solar grid-connected power plants, the use of 1200VIGBT will be the future development trend. In response to the needs of inverters of various specifications, IGBT modules present a trend of increasing integration. It is worth noting that in order to obtain higher conversion efficiency, the use of SiC diodes to design solar inverter systems is the latest development trend. The reasons are: (1) The thermal conductivity of SiC is several times that of gallium arsenide and three times that of Si, which will make devices with higher current density; (2) The breakdown electric field of SiC is almost Si breakdown Ten times the electric field penetration, so the same design using SiC will obtain ten times the rated breakdown voltage of the silicon element, therefore, it is possible to develop a very high voltage Schottky diode; (3) SiC is a wide energy band Materials, therefore, SiC can operate at much higher temperatures than any silicon device. In addition, because solar micro-inverters need to monitor current, voltage, temperature and other analog parameters, microcontrollers with analog and digital mixed signal processing capabilities are expected to find use here. Using new materials to improve the photoelectric conversion efficiency Solar cells provide huge business opportunities for large-scale power generation in the future, but the output power of most solar cells is relatively low at present, and the typical output efficiency is about 15 %%. "The solar energy generated by the Sun every day is 165,000 terawatts (TeraWatt), as long as we can get a very small part of the energy, we can make a big step towards solving the energy crisis," said LucVandenhove, chief operating officer of IMCE, "we are now The biggest technical challenge is how to reduce the cost of solar cells and improve their efficiency. "The schedule of IMEC's ​​solar cell development plan is that the efficiency of 120-micron crystalline silicon cells is expected to reach 20% by 2011; by 2015, The efficiency of crystalline silicon solar cells with a thickness of 80 microns will be higher than 20%. The technical development idea is to increase the absorption coefficient of the material so that it is close to the maximum photon flux of the solar spectrum and has a higher mobility. In addition, by applying the spin coating process to improve the film morphology, the carrier mobility and repeatability are improved. On the other hand, researchers at Deft University of Technology and the Fundamental Research Foundation of the Netherlands pointed out that very small specific semiconductor crystals can produce electronic "avalanche effects." In traditional solar cells, one photon can only accurately release one electron, and in some semiconductor nanocrystals, one photon can release two or three electrons, which is called the "avalanche effect" . These free electrons can ensure the operation of solar cells and provide electricity. The more electrons released, the greater the output power of the solar cell. This physical effect paves the way for the production of inexpensive, high-output solar cells, and is expected to use semiconductor nanocrystals (crystal size in the nanometer range) to manufacture new types of solar cells. This new discovery shows that theoretically, the maximum output energy efficiency of a solar cell composed of semiconductor nanocrystals may reach 44%, while helping to reduce production costs. In addition, IBM recently claimed that they have realized the technology of extracting 230W of energy from a 1 square centimeter solar panel in the laboratory and finally obtaining 70W of available power. Shenzhen Joy LED Display Co., Ltd. , https://www.joe-led.com