《光伏发电系统接入配电网技术规定》标准解读和修订建议Interpretation and revision proposals ofGB/T 29319-2012, Technical requirements for connecting photovoltaic power system to distribution networkAbstract: In the context of clean and low-carbon energy transformation and new power system, China’s photovoltaic power generation will usher in great development. Its large-scale access impacts the safe and stable operation of the power grid with increasing significance. In order to strengthen the support and leading roles of the standards, it is urgent to revise the national standard GB/T 29319-2012, Technical requirements for connecting photovoltaic power system to distribution network , based on the current development trend of photovoltaic power generation and power grid transformation needs. This paper firstly interprets the important technical provisions of the standard, then analyzes the problems in its implementation and finally proposes some revision suggestions in terms of grid adaptability, power control and fault crossing, to facilitate safe and orderly development of photovoltaic power generation in China.Keywords: photovoltaic power generation, distribution network, standard guide, amendmentsBy Lu Minhui 1 Sun Wenwen 2 He Guoqing 2文/路民辉1 孙文文2 何国庆2(1. State Grid Gansu Electric Power Company; 2. China Electric Power Research Institute)1. IntroductionTo exert the supporting and leading roles of the standards, the paper interprets the important provisions of GB/T 29319-2012, for two purposes, on the one hand, enhancing the industry personnel’s understanding of the technical provisions to better implement the standard; and on the other hand, analyzing the limitations of these provisions and proposing reasonable revision suggestions for those which cannot meet current and future development needs of PV power in China.2. Interpretation of the technical standard for grid connection2.1 ScopeThis standard is applicable for building, rebuilding or expanding PV power system connected to the grid with voltage of 380V, or to the user-side with voltage of 10(6)kV. The PV power system should meet other requirements in case of connecting to the public power grid with voltage of 10(6)kV or 35kV or above.BETTER COMMUNICATION ｜ GREATER VALUE2.2 Power control2.2.1 Active power controlActive power control means that, the PV power system has the ability of active power regulation and is able to accept the command signals of power grid scheduling dept. to adjust its active power output. Due to the small scale of PV power development at an early stage, given to the cost and technical considerations, the standard doesn’t specify mandatory requirements on the active power control of the PV power system.2.2.2 Reactive power controlConnected to the grid through inverters, PV power has strong ability of reactive power control. Therefore, according to the standard, the power factor of the PV power system should be adjustable continuously in the range of ±0.95. Moreover, it should be able to adjust reactive output based on the voltage of the connecting points and to participate in adjusting the voltage of the grid.2.3 Operational adaptabilityThe purpose of demanding the operational adaptability of PV power system is to enhance the operational reliability of the PV power system. It is unavoidable for various disturbances to occur in the course of grid operation. When the voltage and frequency are within the specified limits, the PV power system is required to be able to operate normally, to avoid its frequent start-stop to impact users’ interest and grid safety and stability. The operational adaptability means mainly the voltage adaptability and frequency adaptability.3. Problems in connection technical standards3.1 Overlapping and inconsistency of some provisionsImpacted by the revision cycle, some standards are inconsistent, or even contradictory, in terms of the provisions of voltage adaptability and frequency adaptability. For instance, for the PV power system connecting to the user-side with 10(6)kV voltage, the operating range of voltage is specified as 0.9p.u.~1.1p.u. in GB/T 29319, but 0.85p.u.~1.1p.u. in GB/T 3359.3.2 Low requirements of some provisionsAs constant increase of the installed capacity of PV power in recent years, its large-scale connection impacts grid safety more and more significantly. Countries around the world have revised their technical standards for PV power connection timely. Comparison with them suggested that, the requirements in national technical standards of PV power connection are lower, in terms of power control, fault crossing, frequency/voltage tolerance and grid supporting capacity.3.3 Some provisions unavailableThe PV power witnessed the histor y of slow development in the early stage to explosive growth in the later stage. The standard adapted itself to the development of PV power at the time. The core concept was that PV power did not participate in adjusting the frequency and voltage. That is to say, the system frequency and voltage were adjusted by the grid. However, as technological progresses and the new challenges produced by large-scale connection of PV power to the grid, the PV power needs new requirements, like cluster control, primary frequency regulation and power prediction, to improve the hospitality of PV power connection.4. Revision proposals4.1 Active power control1) The PV power system connected to the grid with voltage of 10(6)kV~35kV should be provided with active power control system to have the ability of smooth regulation of active power. The PV power system should be able to receive and automatically execute the control orders of active power and active power change issued by the power scheduling dept. The active power and active power change rate should meet the requirements of the scheduling control of the power system.2) The PV power system connected to the grid withvoltage of 380V should have the ability of active power control and receive the control orders of the scheduling dept. in the manner of cluster control. Based on the actual connection situation of the PV power system in China, the cluster control is illustrated in Figure 1.3) A PV power project of a whole county developed by one owner should be provided with the centralized monitoring system, which is able to receive the scheduling control orders.4.2 Primary frequency regulation1) The PV power system connected with voltage of 10(6)kV~35kV should have the ability of primary frequency regulation. When the system frequency is without the dead zone, the PV power system should be able to regulate the active power output automatically as per the frequencies. The parameters of frequency dead zone, difference coefficient and response time should be determined after negotiating with the grid scheduling dept.2) The PV power system connected with voltage of 380V should have the ability of primary frequency regulation.4.3 Grid adaptabilityThe voltage and frequency ranges should be enlarged for continuous and stable operation of the PV power system.1) When the voltage of the connecting points of the PV power system is within 0.85p.u.~1.1p.u. nominal voltage, the PV power system should be able to operate normally.2) When the frequency of the connecting points of the PV power system is within 48.5Hz~50.5Hz, the PV power system should be able to operate normally.4.4 Power prediction1) The PV power system, of which the connecting voltage is 10(6)kV~35kV and the installed capacity is above 10MW, should be provided with power prediction system, which should have the ability of short-term prediction of 0h~72h and super short-term prediction of 0.25h~4h.2) For the PV power system connected to the grid with voltage of 380V, since there is a great number of it and it cannot provide a power prediction system for a single PV system, the regional power prediction can be adopted, so as to achieve power prediction to all the PV systems in the region. The prediction methods usually include gridding and statistical scaling.4.5 Fault crossing1) The PV power system connected with voltage of 10(6) kV~35kV should have the ability of zero voltage crossing. Within and below the voltage contour in Figure 2, the PV power system should be able to operate continuously without disconnection; otherwise, it will be disconnected.2) For the PV power system connected with voltage of 10(6)kV~35kV, within the voltage contour in Figure 3, the PV power system should be able to operate continuously without disconnection; otherwise, it will be disconnected.Figure 1: Technical routine of low-voltage distributed PVcontrolFigure 2: Requirement on low-voltage crossing of PVpower system BETTER COMMUNICATION ｜ GREATER VALUE3) The PV power system, which connects the grid with voltage of 10(6)kV~35kV and has not disconnected from the grid during low/high-voltage crossing, should recover the power before the fault with at least 20% of the PN/ s power change rate when the voltage at the connecting points is between 0.85p.u.~1.1p.u. nominal voltage.5. ConclusionsThe paper interprets the important provisions of GB/T 29319-2012 and analyzes the problems in its implementation, on which basis, proposes reasonable revision suggestions: first, enhance vertically the technical requirements on PV power system connected with the grid and elevate the voltage/frequency tolerance and fault crossing of the PV power system; second, extend horizontally the coverage of the standard to add new technical requirements like power prediction, primary frequency regulation, low-voltage crossing and high-voltage crossing.6. AcknowledgementsThis paper is sponsored by the science and technology project: Research on electromagnetic and electromechanical transient modeling of Gansu Power Grid based on UHV AC/DC transmission of high proportion renewable energy and its influence on transmission capacity.Figure 3: Requirement on high-voltage crossing of PVpower system[1] , Important Speech of President Xi Jinping on the General Debate of the 75th United Nations General Assembly [N/OL]. (2020-09-23). /n1/2020/0923/ c64094-31871240.html.[2] , the Speech of President Xi Jinping on the Climate Ambition Summit [N/OL]. (2020-09-23). http://cpc.people. /n1/2020/1213/c64036-31964469.html.[3] General Administration of Quality Supervision, Inspection and Quarantine of P.R.C., Standardization Administration of P.R.C. GB/ T 29319-2012 Technical Requirements for Connecting Photovoltaic Power System to Distribution Network [S]. Beijing: China Standards Press, 2017 .[4] Chen Hu, Zhang Tian, Pei Huiming, et al. 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Proceedings of the CSEE, 2015, 35 (14): 3699-3705 .[9] Liang Zhifeng, Ye Chang, Liu Ziwen, et al.Grid-Connected Scheduling and Control of Distributed Generations Clusters: Architecture and Key Technologies [J]. Power System Technology, 2021, 45 (10): 3791-3802 .[10] Wu J unpeng, Yang Xiaodong, Zhai Xue, et al. Analysis of Primary Frequency Regulation of Grid-connected PV Station in Power System [J]. Electrical Measurement & Instrumentation, 2016, 53 (18): 88-92.About the authors:Lu Minhui, Professorate Senior Engineer, engaged primarily in the research on grid connection technology of new energy power generation. Sun Wenwen, Corresponding Author, Engineer, engaged primarily in the research on grid connection technology of new energy power generation. He Guoqing, Professorate Senior Engineer, engaged primarily in the research on grid connection technology of new energy power generation. References。
