1. Introduction
The benefits of replacing fossil fuel with solar energy have emerged recently. However, with government subsidies going less and less, PV industry should rely on lower Levelized Cost of Electricity (LCOE) to get higher market share.
Then, how to achieve lower LCOE? There are two ways, the first is through raising efficiency, the other is through reducing system cost.In the past 20 years, thanks to advancing technology and innovation, the cost of solar power has dropped down significantly. The ordinary 1000 Vdc technology is rather mature and is experiencing a bottleneck for further cost saving.
Meanwhile, the emerging 1500 Vdc technology, which can not only lift efficiency but also reduce cost, will soon become the mainstream PV technology.
2. The 1500 Vdc PV system
2.1 How 1500Vdc system raises efficiency
Less cables, combiners, and PV inverters, less loss of cables and switches.
Higher system voltage leads to lower working current, and reduces loss of cable.
Higher voltage at the low voltage side of the transformer, less low voltage winding loss.
2.2 How 1500Vdc system reduces cost
A 50% reduce of number of strings for the system which means less cables, combiners, PV inverters, and other electrical equipment. Thus the cost of equipment and construction is cut down.
A further reduction of cost on O&M was brought by the low amount of equipment.
The 1500Vdc PV inverter has a higher power density and lower cost.
2.3 1500 Vdc vs. 1000 Vdc
While the system voltage rises from 1000 Vdc to 1500 Vdc, this poses higher requirements of dielectric for key components, and the cost for individual equipment rises accordingly. However, the number of equipment goes down and the entire system cost is less than that of a 1000 Vdc system. The cost for 1500 Vdc system will continue to drop as it becomes more and more popular.
| Key Components | 1500V VS 1000V | Comments |
| Module | High insulation requirement for 1500 Vdc PV modules, slightly higher cost;
The 1500 Vdc PV modules can be connected with 1.5 times more modules than 1000 Vdc PV strings. So it can reduce the number of strings. |
Higher voltage costs lower safety and more obvious Bucket Effect
Longer string, suitable for large utility PV plants. |
| Cable | The DC cable should be able to endure 1500 Vdc and has increased 2% to 5% unit cost.
More less cable used. |
Lower cable cost for 1500 Vdc. |
| Combiner | Higher requirements for dielectric and insulation for 1500 Vdc combiners | Higher requirements of dielectric and cooling for devices like switch. |
| PV inverter | Three-level technology and higher durable power components. | Higher requirements for PV inverter designing. |
| Transformer | Higher voltage at the low voltage side | Lower cost for transformer. |
It is not difficult to realize the 1500 Vdc technology. The major hindrance is lack of standards and judgments for risks. It is predictable that 1500 Vdc will be on high demand in the near future.
3. Sungrow 1500 Vdc system solution
Since its foundation in 1997, Sungrow has always been focused on developing PV inverter technologies and has shipped over 38 GW of inverter equipment worldwide by the end of 2016. Sungrow has not only accumulated rich advanced technologies, but also a stable quality control system. Since 2015, Sungrow has been the world’s no.1 in terms of PV inverter shipment. Sungrow’s innovation is driven by customers’ needs and the target of grid parity. As a leader in the PV inverter industry, Sungrow has paid close attention to the new 1500 Vdc technology and taken great efforts in developing and promoting it.
As mentioned above, the 1500 Vdc PV system is born with many advantages and is also facing many challenges presented by the lifted voltage. The key point of competition for players in this field is on enhancing power yield and stability of the PV inverter and driving the system price down at the same time. Sungrow is a customer-oriented company and adopts the design philosophy of ‘Scientific Design for Different Applications’ which means providing appropriate system solutions for different applications, in order to maximize ROI for its customers.
Central PV inverter solution is promoted for utility-scale PV plants on flat terrain. The SG2500HV/SG3000HV turnkey station solution developed by Sungrow has inherited all the features from its 1000 Vdc predecessors, and also has solved problems brought by the 1500 Vdc system..
With its global total installation soaring, PV has become an important part of the public energy mix and is facing issues of grid support. First of all, the PV inverter should be compatible with real time grid regulation. Sungrow PV inverters can react to the regulation order instantly and takes control of power output. Secondly, higher unit power of PV inverters can decrease the number of equipment and the risk of resonance and off-grid. Thirdly, when the voltage of the grid becomes irregular, the PV inverter should be able to ride through the fault voltage and protect a stable operation of the system. Finally, the inverter is becoming more and more important in the power system and will be added with more value in the future.
String inverter solution promoted for complicated applications. The SG125HV 1500 Vdc string inverter, the largest of its kind in the world, is a diversified product. Sungrow has developed a Virtual Central Inverter solution based on the new SG125HV string inverters which are installed together for the convenience of O&M.
4. Case reference
In the second half of 2015, the first 1500 Vdc solar power plant was built by Sungrow and the plant was connected to the grid in early of 2016.
China Three Gorges New Energy built a 50MW power plant in Datong, Shanxi province, China, in May of 2016. And 20MW of 50MW utilized the 1500 Vdc system solution with central inverter SG2500HV supplied by Sungrow. According to the plant manager, the 1500V central inverter SG2500HV was proved to work stably and have a higher unit capacity compared to the 1000 Vdc inverter. “A lot of troubles and losses have been avoided by using Sungrow’s inverters due to its high power generation and low failure rate. Now, its 1500 Vdc inverters are as stable and effective as it used to be, and we will continue to cooperate with Sungrow for the future 1500V projects,” said the plant manager.
Sungrow’ inverters and combiner boxes have been deployed in plenty of power plants, up to the first half of 2017. More plants with Sungrow’s 1500 Vdc inverters will be connected to the grid in India, North America and so forth in 2017. Sungrow is ready to embrace the era of the 1500 Vdc system for solar power plants.
