The new 1500V inverter of Jiuquan Runke, a subsidiary of Mengshi Technology, opens a new era of photovoltaics

Reporter: What is the value and significance of the 1500V photovoltaic system?

Du Fangyong, General Manager of Jiuquan Runke: With the vigorous development of the photovoltaic industry, global photovoltaic subsidies are declining. Some European markets have cancelled subsidies and require grid parity. However, the photovoltaic installed capacity planned by various countries is increasing year by year. While ensuring the quality of power stations and long-term power generation income, how to further reduce the initial investment cost has become a top priority.

Reducing the initial investment cost can be achieved through technological changes and reducing the cost of the equipment itself. However, with the development of the photovoltaic industry and market needs, it is basically impossible to further reduce the price of key system equipment components, inverters and other equipment without new technological breakthroughs.

Reducing the initial investment cost can also be achieved by increasing the system voltage and the number of unit arrays. With the increasing size of photovoltaic power stations, the traditional 1000-volt system and 1-megawatt unit array are no longer advantageous in reducing system costs. The market is increasingly accepting high-voltage photovoltaic systems above 1000 volts. North America and Europe have become the main markets for 1500 volts. Some domestic design units and owners also tried 1500-volt photovoltaic systems in 2016.

Reporter: What are the advantages of a 1,500-volt system compared to a 1,000-volt system?

Du Fangyong, General Manager of Jiuquan Runke: The voltage resistance level of the components, inverters, cables, combiner boxes and other equipment of the 1500V system has been improved. The 1500V system has a high voltage resistance level, and each string can be connected in series with more components, saving the cost of equipment such as cables, combiner boxes, transformers, etc., reducing the line loss on the AC and DC sides and the loss on the low-voltage side of the transformer, with higher power density, smaller volume, and less transportation and maintenance.

In view of the many advantages of the 1500-volt system, Jiuquan Runke took the lead in launching inverters suitable for the 1500-volt system in 2015.

Reporter: What are the unique advantages of Jiuquan Runke's 1500V inverter compared with 1500V inverters launched by other companies?

Du Fangyong, General Manager of Jiuquan Runke: Jiuquan Runke has developed two 1500V inverters, namely ALBA air-cooled inverter and ZENIT liquid-cooled inverter.

In general, Jiuquan Runke 1500V inverter has several unique advantages: first, it is a more advanced heat dissipation solution. The air of the ALBA series does not need to circulate in the inverter, and the heat of the ZENIT series is taken out by the liquid and removed by the turbo fan. The interior is cleaner, there is no filter, and no frequent cleaning is required, which is suitable for windy and sandy areas. In any country in the world, dust removal of photovoltaic inverters is a troublesome thing. In the northwest of my country, dust accumulation has brought many fault points. The new inverters we designed are all independent air ducts, and the air exchange and heat exchange will not contact the components. Traditional air cooling and air cooling need to inhale air and do convection heat exchange, which will leave dust and humidity in the environment in the components, causing many short circuits or fault points. We have built a 10MW photovoltaic demonstration project in the Dunhuang Gobi Desert. After two years of operation, dust removal was only done twice.

The second is the more intelligent IoT monitoring system Smart HMI, which is equivalent to a super brain, more precise control, direct interface management IGBT drive, error identification, and low harmonics. The third is a lower loss control strategy, low IGBT loss, better power quality, and full power harmonics less than 1%. The fourth is a simpler circuit topology, fewer components, and low conduction loss. In addition, there is higher reliability and higher photovoltaic system efficiency. Nearly 50% of our components are imported from big brands. I once said that we want to use the best components to create the lowest-priced inverter.

Reporter: The best components and the lowest price are usually a contradiction. How do you achieve this?

Du Fangyong, General Manager of Jiuquan Runke: When I said that we should use the best components to assemble the lowest-priced inverter, many predecessors said it was impossible. But after three years of hard work, we have made it cheaper than any domestic company with nearly 50% of imported components. From a scientific research perspective, it is to simplify simple problems, rather than reducing prices by reducing or replacing components. Price reduction does not necessarily mean reducing configuration, but can be achieved by improving technology. The power density of our products is relatively large. Using control systems and integration experience, we integrate components into a power electronics system with a relatively large volume ratio, so that the overall cost is reduced. For example, the export of Runke's 2.5 MW inverter only needs to be connected to a dual-winding transformer, while the traditional 500 kW inverter requires 2.5 dual-split winding transformers to achieve the same capacity.

Power electronics is the core part of the inverter. The fewer power electronic components the inverter has, the fewer fault points there are, not the smaller the inverter, the fewer fault points there are. According to actual operation calculations, using our 1500V inverter can save 0.2 yuan per watt in initial investment.

Reporter: How does Runke's 1500V inverter reduce costs?

Du Fangyong, General Manager of Jiuquan Runke: With Runke 1500V inverter, a photovoltaic power station of the same capacity needs fewer inverters. A 100MW photovoltaic power station using the ALBA 2MW solution only needs 50 inverters, while an ordinary 500kW inverter requires 200, and an ordinary 40kW inverter requires 2500. In addition, inverters of the same capacity require fewer key components, IGBTs. Runke ALBA 2MW inverter requires 24 IGBTs, while a traditional three-level 500MW inverter requires 192 IGBTs, and a 40MW string inverter requires 600 IGBTs.

The later operation and maintenance workload is also lower. Under the condition of 2% failure rate per year, a 100MW photovoltaic power station needs 50 ALBA 2MW centralized inverters, with an average maintenance cost of 17,000 yuan per time. In 25 years, only 20 maintenances are required, and the required cost is 340,000 yuan. In contrast, 200 traditional 500kW centralized inverters are required, with an average maintenance cost of 8,000 yuan per time. In 25 years, 80 maintenances are required, and the required cost is 640,000 yuan. In contrast, 2,500 40kW string inverters are required, and the total maintenance cost in 25 years is 12 million yuan.

In addition, we have a dedicated power optimization system that can reduce system losses. The 20MW photovoltaic power station using Jiuquan Runke's 2MW solution can reduce system losses by about 5% compared with the traditional 500kW solution.