Views: 4 Author: Site Editor Publish Time: 2021-12-23 Origin: Site
"Self-generation and self-use, and the balance on the grid" means that the electricity generated by photovoltaics is given priority to the load, and the load is not used up, and then sent to the grid. Friends who are in contact with photovoltaics for the first time will have many questions: how can the electricity from photovoltaics be guaranteed to be used by the load first, instead of sending photovoltaic electricity to the grid, and the load taking electricity from the grid? Is there any basis to explain that the electricity used by the load is photovoltaic electricity, not electricity sent from the grid? Will the inverter or equipment be affected by frequent switching between photovoltaic power generation and mains power?
1. The current has only one direction at the same time
From the circuit principle, the current flows from a place with a high voltage to a place with a low voltage. At the same time, the direction of the current is unique, that is, the current cannot flow in and out at the same point at the same time. We take the user-side electric meter as the node. At the same time, the current has only one direction, either the photovoltaic current flows to the grid or the grid current flows to the load. Therefore, there is no situation in which photovoltaic power is sent to the grid at the same time and the load is drawn from the grid.
2. Why can photovoltaic power be used first?
Photovoltaic power generation is a kind of power source, it can output electric energy, and it can only output electric energy, and the power grid is a special kind of power source, it can not only provide electric energy to the load, but also can be used as a load to receive electric energy, according to the current is from the high voltage The principle that places flow to places with low voltages, when photovoltaic power generation, from the load point of view, the voltage of the grid-connected inverter is always a little higher than the voltage of the grid, so the load uses photovoltaic power generation first, only when the photovoltaic power is less than the load After the power is turned on, the voltage at the grid connection point will drop and the grid will supply power to the load. Distributed photovoltaic, self-generated and self-used, and the balance is connected to the Internet. Generally, two electric meters are installed. The inverter is installed with an electric meter to record the photovoltaic power generation. The grid buys electricity.
In the grid-connected feeder system, the mains power is mainly used to construct the voltage/frequency/phase of the power grid. The grid-connected inverter does not output voltage, but tracks the phase and waveform of the grid, and only outputs current to the grid, because the voltage of the photovoltaic inverter is higher than the grid voltage. According to the circuit principle, the current flows from a place with a high voltage to a place with a low voltage. Therefore, as long as photovoltaic energy can generate electricity, it will be sent to the load end first.
From the load point of view, the current consumed by the load is obtained from the current source closest to itself. Taking the roof system as an example, the grid-connected inverters are all after the mains transformer, and of course the grid-connected inverters are used first.
3. Will the inverter or equipment be affected by frequent switching between photovoltaic power generation and mains?
Because the light is unstable, the power of photovoltaic power generation is also unstable in time and time, so the electricity used for the load may sometimes be photovoltaic power, sometimes it may be city power, and sometimes it may be both photovoltaic power and city power supply. In fact, this is the surface Up. Theoretically, the electricity used by users is the electricity of the grid, because the inverter has a function that can turn the electricity generated by the components into the same electricity as the grid, with the same voltage, the same frequency, and the same electricity. Phase. This switching process actually does not exist.