In August this year, the National Energy Administration issued the “Guiding Opinions of the National Development and Reform Commission and the National Energy Administration on the Implementation of “Integration of Wind, Solar, Water and Fire Storage” and “Integration of Source, Network and Load” (Draft for Solicitation of Comments). Research on the “integrated” implementation plan of bundling new energy power in the vicinity in terms of the output characteristics of the end hydropower, the characteristics of the new energy, the receiving end system conditions and the consumption space. Hydro-light complementary power generation is one of the main forms of “integration of wind, solar, water and fire storage”. At present, relevant project planning or preliminary work has been carried out in Southwest China. In March, Yunnan Province proposed to advance the construction of 3 million kilowatts of photovoltaics in a scientific and orderly manner, intending to deploy water and solar complementary power generation projects in Chuxiong and other areas with better light resources. At the end of June, the General Department of the National Energy Administration issued the “Notice on Announcement of the Results of the 2020 National Subsidy Competition for Photovoltaic Power Generation Projects”. Guizhou 1.2 million kilowatts and Guangxi’s 100,000 kilowatt water and solar complementary photovoltaic power generation projects are planned to be included in the 2020 photovoltaic power generation national bidding subsidies. List of projects. The scientific promotion of water and light complementary power generation is of great significance for promoting the high-quality development of renewable energy, improving the operating efficiency of the power system, and promoting the green and low-carbon transformation of energy.
The reliability and stability of water and light complementary power generation are significantly improved
Hydro-light complementary power generation is to make full use of the existing transmission line channels of hydropower stations and the rapid adjustment capabilities of hydropower units to bundle photovoltaic power generation and hydropower generation power to send out, improve line channel utilization, reduce the impact of photovoltaic power generation volatility, and reduce system backup. Water-light complementary power generation control mainly includes AGC and AVC control.
Among them, AGC control is under the premise of ensuring the safe and reliable operation of hydropower units and photovoltaic power generation equipment, comprehensively considering factors such as photovoltaic power generation output prediction, reservoir scheduling, hydropower generation operating conditions and consumption characteristics, and realizing automatic adjustment of active power and frequency. The control principle is to treat the photovoltaic power station as a non-adjustable unit of the hydropower station, and smooth the fluctuation of photovoltaic output through the rapid adjustment of the hydropower unit to meet the demand for photovoltaic power generation, while ensuring that the total output meets the dispatch control requirements. In addition, the AGC control sets the joint vibration zone and action threshold of the hydropower unit to ensure that the output of the hydropower unit is within a reasonable range and reduce the number of adjustments that are increased due to frequent photovoltaic fluctuations.
AVC control is to realize the automatic control of reactive power and voltage by coordinating the dynamic reactive power compensation device of the photovoltaic power station and the reactive power adjustment capability of the hydropower unit. According to the voltage or reactive power control command, the system preferentially calls the reactive power compensation equipment of the photovoltaic power station, and then uses the hydropower unit to participate in reactive power regulation under conditions that cannot meet the requirements, so as to improve the operational reliability and stability of the hydropower unit.
Four issues need to be paid attention to in the current development of hydro-light complementary power
Although the advantages of hydro-light complementary power generation are obvious, there are still many issues worthy of attention.
One is the ratio of water and light capacity. Complementary water and photovoltaic power generation can reduce the impact of direct photovoltaic grid connection on the system, but it also reduces the adjustment capacity and operational flexibility of the hydropower unit. Therefore, a reasonable ratio of water and light capacity is the key to give play to the advantages and functions of water and light complementary power generation. Based on land resources, environmental protection, watershed shipping and flood control requirements, combined with the reservoir capacity, hydroelectric generating unit regulation performance, power consumption space, load characteristics, system peak shaving demand and transmission channel capacity, etc., the photovoltaic power generation capacity should be determined as a whole. In addition, in the complementary control system, the parameter settings such as the joint vibration zone of the hydropower unit should be matched with the photovoltaic power generation capacity, so as not to affect the operation effect of the water and light complementary power generation.
The second is the problem of absorption and access to the system. The large and medium-sized hydropower stations in the southwest region are mainly connected to the grid with voltage levels of 220 kV and above, and electricity generally needs to be transmitted to the load center for long-distance consumption. For the photovoltaic power station access system, it is necessary to first analyze the direction of power consumption, and demonstrate in detail the necessity of the photovoltaic power station directly bundled with large and medium-sized hydropower stations. If the nearby area has the consumption space and delivery conditions, priority will be given to connecting photovoltaic power stations to the surrounding sites through low voltage levels; if the nearby area has no consumption space or the delivery conditions, a full technical and economic comparison of various delivery options will be made Later, it can be recommended that the photovoltaic power station be connected to a high-voltage booster station of a hydropower station, and sent out through the existing lines of the hydropower station.
The third is the coordination with conventional power supplies. The large-scale development of photovoltaic power generation in the form of complementary water and light will occupy the power space of conventional power sources, resulting in inefficient operation of some units, and intensifying conflicts of interest between power supply companies. As the current power market auxiliary service mechanism is not yet perfect, if the basic supporting role of conventional power sources is weakened, the safety and stability of the power system will be affected. Therefore, it is necessary to coordinate the coordinated development of hydro-solar complementary power generation and conventional power generation.
The fourth is the impact on the operation of the power grid. The large-scale grid connection of photovoltaics in the southwest region will continue to put pressure on power transmission sections in southwestern Guizhou, northwestern Guizhou, and northwestern Yunnan. As a large number of power electronic components are connected to the system, it may cause new problems such as reduced moment of inertia, insufficient short-circuit capacity support, and subsynchronous resonance, which affect the safe and stable operation of the power grid.
To strengthen the complementary high-quality development of water and light, efforts should be made from three aspects
In response to the above problems, it is recommended to strengthen planning coordination, coordinate the needs of all parties, and promote the high-quality development of water and light complementary. First, carry out a unified plan for large and medium-sized hydro-photovoltaic complementary power generation in the Southwest region, and promote the participation of all parties including land, environmental protection, water conservancy, power supply, and power grids, and overall consideration of resource conditions, environmental protection, flood control and shipping, power consumption and transmission, grid peak shaving and Factors such as security and stability to achieve multi-target coordination.
At the same time, improve technical standards and standardize management systems. It is recommended to formulate technical standards for large and medium-sized hydro-photovoltaic complementary photovoltaic power generation projects in accordance with the safety and stability guidelines of the power system, hydropower and photovoltaic power plant design, reservoir dispatching management, etc., to clarify the reasonable penetration rate of hydro-photovoltaic complementary, send for verification and dispatch operation Strengthen the standardized management of planning, design, construction and operation.
In addition, the market mechanism must be improved to promote coordinated development. The southwest region is under pressure to purchase renewable energy power in full guarantee, and the market value of new energy power generation has not yet been fully reflected. It is recommended to adhere to the principle of marketization, actively promote the participation of new energy power generation in market-oriented transactions, accelerate the construction of the auxiliary power service market, promote the coordination of source and network, and promote the high-quality development of hydro-electric power generation.