Huawei SDS User Manual
White Paper on SDS Intelligent Joint Control Technology for Inverters and Trackers
Jointly issued by: National Energy Key Laboratory for Wind and
Solar Simulation, Testing and Certification, China General
Certification Center, and Huawei Technologies Co., Ltd.
November 2020
White Paper on SDS Intelligent Joint Control Technology for Inverters and Trackers
Preface
Currently, the smart DC system (SDS), an intelligent joint control technology for inverters and trackers developed by Huawei Technologies Co., Ltd. (hereinafter referred to as "Huawei"),
has entered the large-scale application phase. Entrusted by Huawei, China General Certification Center (CGC) has carried out a comprehensive review and verification of the SDS to verify its technical performance and application effect. Based on the review and verification results, the National Energy Key Laboratory for Wind and Solar Simulation, Testing and Certification, CGC, and Huawei jointly released the White Paper on SDS Intelligent Joint Control Technology for Inverters and Trackers. This white paper describes the development background, technical features, and application effects of the SDS in detail, helping the industry comprehensively and deeply understand the technology.
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White Paper on SDS Intelligent Joint Control Technology for Inverters and Trackers
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Technology Development Background
Continuously improving the efficiency of PV power systems is a sedulous pursuit in the industry. For this purpose, at the device end, the main goal is to improve the optical-to-electrical conversion efficiency of PV modules and reduce the energy loss of other devices. At the system end, the main goal is to increase the radiation received at the surface of the PV modules and reduce the efficiency loss.
In recent years, the efficiency improvement achievements at the device end are remarkable, but there is not much room for improvement.
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The industry has shifted the focus on the system end. The application percentage of various technologies, especially the tracking technology, is increasing, aiming to improve the radiation received by the PV module surface. Figure 1-1 shows the application percentage of trackers in bases of the second and third phases of PV Forerunner, a PV demonstration project initiated by National Energy Administration, in China. The figure indicates that the application percentage of trackers increased significantly in the third batch of bases. In addition, according to the data released by GTM, the shipments of trackers in 2017, 2018, and 2019 increased by 34%, 36%, and 66% year on year. In 2019, the global shipment of trackers was about 35 GW.
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Figure 1-1 Comparison of application scale and percentage of trackers in the second and third batches of PV Forerunner bases (partially)
The trackers have been used for a long time, but the following issues may also exist in actual applications:
(1)Most tracking system algorithms are provided by the tracker manufacturer.
Traditional astronomical algorithms are used, in which the impact of terrain conditions, blocking in the morning and evening, and weather changes is not fully considered. Due to miscalculations of the optimum tracking angle, energy yield loss may occur in some time periods and in special weather conditions. Figure 1-2 and Figure 1-3 show the examples.
Figure 1-2 Examples of shading between arrays in special areas and in the morning and evening
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White Paper on SDS Intelligent Joint Control Technology for Inverters and Trackers
Figure 1-3 Difference of received radiation at different angles on cloudy weather
(2)To solve the problems in common astronomical algorithms, the backtracking technology is used in the industry. However, the tracker angle control is relatively independent and is not associated with the I-V perception or change of the PV strings or control units. Therefore, refined adjustment or precise control cannot be implemented.
(3)In recent years, the power generation technology using the combination of trackers and bifacial PV modules has become one of the mainstream forms. This kind of system needs to dynamically adjust the control policy according to the change of external conditions. Figure 1-4 compares the daily cumulative radiation of the front and rear sides of a random 15-day period selected from the
3-month monitoring data of the CGC Inner Mongolia empirical research system (horizontal single axis and bifacial PV module power generation).
As shown in Figure 1-4, the ratio of the radiation received from the front side to that from the rear side varies greatly due to the weather. In special weather conditions, the daily accumulated radiation on the rear side is even higher than that on the front side. This means that the angle of the PV modules needs to be dynamically optimized and adjusted based on the weather conditions for the bifacial tracking power generation system, maximizing the control unit output.
Ratio of Daily Received Radiation on the Front Side to the Reference Value
Ratio of Daily Received Radiation on the Rear Side to Received Radiation on the Front Side on the Current Day
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Figure 1-4 Comparison of daily accumulated radiation on the front and rear sides (horizontal single axis)
As mentioned above, with the improvement of reliability and cost-effectiveness, the application percentage of the trackers, including the power generation technology using the combination of trackers and bifacial PV modules, will gradually increase.
To solve the issues in the application of the trackers, the big data and AI technologies are used to optimize the inverter and tracker control linkage, further improving the increase effect of the trackers. This has become one of the development directions of the tracking technology.
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White Paper on SDS Intelligent Joint Control Technology for Inverters and Trackers
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Technology Description
Figure 2-1 and Figure 2-2 show the SDS block diagram, and logical block diagram of algorithm design and angle optimization, respectively.
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Figure 2-2 Logical block diagram of algorithm design and angle optimization
The SDS technology developed by Huawei has the following features:
(1)The inverter is linked with the tracker control system and performs closed-loop control to ensure that the system runs with the maximum radiation volume received by PV modules and optimal power output.
(2)No additional sensor device is required. AI technologies are used to automatically detect shading and weather changes and automatically optimize and control the tracking angle, eliminating manual operations and experience dependence.
(3)The inverter integrates the tracker communication and power supply functions and the tracker power supply cables and communication cables are reduced thanks to MBUS.
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