In distributed photovoltaic systems, ensuring that loads prioritize using photovoltaic (PV) power is key to enhancing energy efficiency and economic benefits. Here’s an overview of the fundamental principles and operational methods involved.
1. Circuit Principles
Electric current flows from areas of higher voltage to lower voltage. At any given moment, the direction of current is singular, meaning that at one point, current cannot both flow out and in simultaneously. Therefore, it’s impossible for PV power to be fed into the grid while the load simultaneously draws power from the grid.
2. Priority of Photovoltaic Generation
As a power source, PV generation can only output energy, while the grid can both supply and receive energy. When solar power is generated, the voltage from the grid-tied inverter is slightly higher than that of the grid, causing the load to prioritize using the PV power. Only when the power generated by the PV system is less than the load demand will the grid supply electricity.
3. Role of the Inverter
Grid-tied inverters do not output voltage but track the grid’s phase and waveform, only sending current to the grid. Since the voltage of the PV inverter is higher than that of the grid, current flows from the PV inverter to the load, ensuring the load uses solar power first.
4. Meter Configuration
Distributed PV systems typically require two meters: one to record the PV generation and another, a bi-directional meter, to track the electricity flowing to the grid and the electricity purchased from the grid.
5. Relationship Between PV Power and Load
- When PV Power is Less Than Load: PV generation is prioritized for the load, known as self-consumption.
- When PV Power Exceeds Load: Excess power generated by the PV system is fed into the grid, referred to as surplus feed-in.
6. Location of the Grid Connection Point
The PV connection point should be installed inside the user’s meter, close to the load. This configuration helps maintain grid stability while ensuring that the proportion of PV generation remains relatively low, minimizing any potential impact on the grid.
Conclusion
Through these principles and configurations, inverters can ensure that loads prioritize using photovoltaic power, enhancing energy self-sufficiency and reducing reliance on the grid. This design not only improves the economic efficiency of PV generation but also supports the stable operation of the grid.