The impact of grid-connected solar photovoltaic power generation systems on future power grid development

The impact of grid-connected solar photovoltaic power generation systems on future grid development:
1. Impact of load peak and valley on power grid. Because the grid-connected solar photovoltaic power generation system does not have the ability of peak regulation and frequency regulation, it will have an impact on the morning peak load and evening peak load of the grid. The increase in the power generation of grid-connected solar photovoltaic power generation systems does not reduce the number of traditional rotary units. The power grid needs to prepare a large number of rotating standby units for the photovoltaic power generation system to solve the problem of peak loading in the morning and evening peaks. Grid-connected solar photovoltaic power generation systems supply power to the grid at the cost of reducing the number of hours per unit of utilization, which of course is not what power producers want to see.
2. The influence of day and night change, east-west time difference and seasonal change on the power grid. Due to the periodicity of sunshine and load, the increase in power generation of grid-connected solar photovoltaic power generation systems cannot reduce the demand for installed capacity of the grid.
3. Changes in meteorological conditions. When a city's photovoltaic roof grid-connected power generation reaches a certain scale, if the geography and weather change greatly, the grid will provide enough regional rotating standby units and reactive power compensation capacity for the grid-connected solar photovoltaic power generation system to control and adjust the frequency and voltage of the system. In this case, the power grid will sacrifice the economic operation mode to ensure the safe and stable operation of the power grid.
4. Long-distance photovoltaic power transmission. When the grid-connected solar photovoltaic power generation system is economically and technically capable of long-distance transmission, it will bring new stability problems to the AC grid because there is no rotary inertia, governor and excitation system for grid-connected photovoltaic power generation. If grid-connected photovoltaic power generation forms a scale to use high-voltage AC /DC transmission, it will bring stability and economic problems to the AC system adjacent to the grid-connected photovoltaic power transmission system. Transmission lines dedicated to grid-connected photovoltaic power generation, due to low efficiency, will restrict the use of desert solar energy. Transmission lines used to borrow or take into account the electricity of grid-connected solar photovoltaic power generation systems, due to low load rate, uneconomic. No matter using high voltage AC or DC transmission, photovoltaic grid-connected power stations need to be equipped with automatic reactive voltage regulation devices. As for the impact on the stability of the power grid, there is no mathematical model of photovoltaic power generation (including the power supply model and the load model) in the power grid stability calculation. It is not yet clear how much impact photovoltaic power generation will have on the safe and stable operation of the grid.
5. Consumption issues. One of the main advantages of grid-connected photovoltaic power generation is that it can replace the consumption of fossil fuels. Because grid-connected photovoltaic power generation increases the rotary reserve or thermal reserve of the power plant rotating generator, the actual consumption reduction ratio of grid-connected photovoltaic power generation should deduct the energy lost by rotary reserve or thermal reserve. The consumption reduction efficiency of grid-connected photovoltaic power generation should consider the efficiency loss caused by the reduction in the utilization hours of the generator set of the power generation company due to the electricity provided by the grid-connected solar photovoltaic power generation system. Because the power system operates as a whole, photovoltaic grid-connected power generation to the grid will infringe on the interests of other power generators, which is an issue that policy makers need to consider. This is due to the consideration that in order for the grid to operate safely, stably and economically, it is not only necessary to use the hydropower plant as a rotating backup. Therefore, the theoretical standard coal consumption reduction equivalent to the total amount of photovoltaic grid-connected power generation in the system should be multiplied by a factor less than 1, and the plant power loss of the rotating standby unit should be subtracted in equal proportion.
The formula for judging the actual consumption reduction effect of photovoltaic power generation:
w =[(Wc/Wn)* Wp-(Pc/Pn)Pd);1
1)W -- the actual consumption reduction of grid-connected photovoltaic power generation (standard for coal);
2)Wc - total thermal power generation of power grid;
3)Wn -- total power generation of the grid;
4)Wp -- Theoretical consumption reduction of grid-connected photovoltaic power generation (standard for coal)
5) PC-total power consumption of thermal power plant (standard coal);
6)Pn- total plant power consumption in the power grid (standard coal);
7) Power loss of PD-rotary standby unit (standard coal).
6. Environmental protection; Whether the emission reduction effect of photovoltaic power generation should only consider the sulfur dioxide and carbon dioxide emissions of thermal power generation remains to be studied, because when photovoltaic power generation is connected to the grid, the grid is also considering the safety, stability and economic operation of the grid, often not only the thermal power plant reduces output, but also considers the rotation of standby. Nor is it just hydropower plants that take on the task of rotating backup (hydropower plants have less to lose from rotating backup tasks).