Energy is a fundamental driving force for human civilization and socio-economic development. With the energy crisis and environmental pollution becoming increasingly severe, countries worldwide are prioritizing the development and utilization of sustainable and clean energy as part of their future energy development strategies. Solar energy, with its unique advantages of being clean and pollution-free, having no geographical boundaries, and being inexhaustible, has become a focus of attention. Grid-connected photovoltaic (PV) power generation is currently one of the main applications of solar power. The grid-connected inverter is the core component of a solar PV grid-connected power generation system. Solar energy is converted into direct current (DC) electricity through photovoltaic modules, and then the grid-connected inverter converts the DC electricity into a sinusoidal current with the same frequency and phase as the power grid, feeding it back into the grid. This allows green and clean solar energy to efficiently serve humanity.
Current Status of Domestic and International Grid-Connected Photovoltaic Inverter Products
Major international manufacturers of grid-connected photovoltaic (PV) inverters include SMA, Fronius, Kaco, and Shap. SMA is the world's earliest and largest PV inverter manufacturer. Foreign PV inverter manufacturers, represented by SMA, have an early start and mature technology, leading the technological innovation and development of the global PV industry. Currently, they produce a wide variety of products with complete series, exhibiting high stability, reliability, and conversion efficiency. Another characteristic of foreign products is their high level of intelligence. Based on the actual application of PV systems, they have developed highly intelligent PV inverter products, which, combined with monitoring systems and power distribution protection systems, form a fully functional PV power generation system.
There are many domestic inverter manufacturers, but only a few specialize in photovoltaic (PV) power generation system inverters. Many manufacturers have expanded their production and R&D to PV inverters based on their existing technologies in vehicle inverters, communication inverters, power inverters, and UPS systems. Due to their years of experience in the inverter industry, many domestic companies have achieved a certain scale and competitiveness. Major domestic PV inverter manufacturers include: Hefei Sunshine, Beijing Kenuoweiye, Beijing Suoying, Nanjing Guanya, Zhicheng Champion, and Shanghai Yingweili New Energy. Table 1 lists several major domestic PV grid-connected inverter manufacturers and their main product types.
Grid-connected photovoltaic power generation projects are the main application area of photovoltaic inverters. At present, most photovoltaic power generation projects are in the demonstration stage and are concentrated in economically developed cities such as Beijing, Shenzhen and Shanghai. With the maturity of technology and the support of national policies, it is expected that the development will extend to the central and western regions with abundant solar resources in the future.
Analysis of Major Domestic Grid-Connected Photovoltaic Inverters
Photovoltaic grid-connected inverters are mainly divided into two categories: centralized and distributed. In China, Hefei Sungrow Power Supply Co., Ltd. is a representative of centralized grid-connected inverters. Other manufacturers such as Kenuo Weiye, Suoying Electric, Guanya, and Zhicheng Champion are also manufacturers of centralized grid-connected inverters, but they lag behind Hefei Sungrow Power Supply in terms of scale and product range. Shanghai Yingweili Technology Co., Ltd. has adopted a completely different development strategy from traditional centralized grid-connected inverters and is the first company in China to develop distributed photovoltaic grid-connected micro-inverters. The following analysis will focus on Sungrow Power Supply and Yingweili New Energy as representatives of these two types of grid-connected inverter products.
Sungrow's photovoltaic grid-connected inverters are divided into string type and power station type, both of which are centralized grid-connected inverters. Centralized grid-connected inverters combine multiple photovoltaic modules in series and parallel to form a sufficiently high voltage or power output, which is then connected to the grid. String type photovoltaic grid-connected inverters are suitable for small and medium-sized photovoltaic power generation systems, while power station type photovoltaic grid-connected inverters are suitable for large and medium-sized photovoltaic power generation systems. Their main performance characteristics are as follows:
1) Power rating: String type 1.5kW~10kW, Power station type 30kW~1MW;
2) Input voltage level: String type 150V or above, substation type 450V or above;
3) Output voltage: 220VAC, 380VAC;
4) Maximum conversion efficiency: 94.5%~95%;
5) Maximum Power Point Tracking (MPPT) efficiency: 99.9%;
6) Communication and protection functions: comprehensive;
Founded in 2008, Invesco New Energy Technology (Shanghai) Co., Ltd. is the first and currently the only company in China to independently develop a grid-connected photovoltaic micro-inverter. Micro-inverter technology maximizes the power generation efficiency of a single photovoltaic module by matching each module with an inverter that has independent DC/AC conversion and MPPT functions.
The main performance characteristics of Invesco's microinverter products are as follows:
1) Power rating: Matched to a single photovoltaic module, 180W~300W;
2) Input voltage level: Matched to a single photovoltaic module, 20V~40V;
3) Output voltage: 220VAC;
4) Maximum conversion efficiency: 95%;
5) Maximum Power Point Tracking (MPPT) efficiency: 99.9%;
6) Communication and protection functions: comprehensive;
Centralized photovoltaic grid-connected inverters have an early start and a complete product series. They are the mainstream products in the photovoltaic inverter market and occupy a dominant position. However, with the increasing maturity of technology and the continuous development of commercial applications, the problems of centralized photovoltaic grid-connected power generation systems have gradually attracted attention: (1) Reliability: In centralized photovoltaic grid-connected power generation systems, the inverter is the key link and also the weak link in the whole system. The failure of a single inverter will lead to the collapse of the entire system; (2) MPPT tracking efficiency: Although most centralized photovoltaic inverter manufacturers claim that the tracking efficiency can reach 99.9%, in fact, since its MPPT tracking is aimed at the entire photovoltaic array, it cannot take into account each photovoltaic module. The power loss caused by module matching, partial shading and other factors is considerable; (3) System scalability: The characteristics of centralized systems determine that their system scalability is poor.
Distributed microinverter technology was developed to address the numerous problems associated with centralized grid-connected photovoltaic inverters. Although its development started later and its product range is still incomplete, it remains in its early stages. However, in terms of current product performance, microinverters are in no way inferior to, and may even outperform, traditional centralized inverters. By directly connecting to individual photovoltaic modules, microinverters can achieve true MPPT (Multi-Level Productivity) for each module, maximizing its power generation efficiency. They offer flexible installation and expansion, are plug-and-play, and can be modularly produced. Microinverter manufacturers can collaborate with photovoltaic module manufacturers to customize inverters for specific photovoltaic modules, thereby accelerating their commercialization and marketization.
in conclusion
1) With the development of solar photovoltaic power generation technology, photovoltaic inverter technology has become increasingly mature, and the product series has become increasingly complete, enabling it to meet the application needs of different power levels;
2) Traditional centralized grid-connected inverters have an early start and relatively mature development, and have achieved a certain degree of promotion and application, occupying a dominant position in the market;
3) Distributed microinverter technology started relatively late, but has developed rapidly. The main product technical indicators are now comparable to, or even superior to, centralized grid-connected inverters;
4) Distributed microinverter technology has a very broad application prospect, especially suitable for urban, photovoltaic building and other application fields. The strong alliance between microinverter technology and photovoltaic module manufacturers will greatly accelerate the further development of microinverter technology and increase its market share.
