1. Energy analysis
A rotating solar inverter converts the energy of a DC power source into AC electrical energy and inputs it into the power grid. It is divided into two parts: one part is directly converted into AC electrical energy through a distribution switch, which is carried out in the low-voltage winding, and the other part is converted into AC electrical energy through a rotating magnetic field, which is carried out in the high-voltage winding.
2. Torque analysis
The rotating solar inverter itself does not output torque, but it generates torque internally. DC current is generated in the low-voltage winding through a distribution switch, driving the rotor magnetic poles to generate active torque; The braking torque generated by the induced current in the high-voltage winding is balanced with it.
3. Performance formula for three-phase rotating active solar inverters
The designed three-phase rotating active solar inverter is modified from a DC motor, and the speed of the solar inverter is calculated according to the calculation method of the DC motor.
Among them:
The rotational speed (r/m) of the n rotating solar inverter is generally designed to be 3000r/m to reduce costs
U battery voltage
Φ The magnetic field strength of the rotor pole can be taken as 10000-12000 Gauss
Total turns of W low-voltage coil
Ce motor structure constant, determined based on magnetic field area, winding short distance coefficient, and distribution coefficient
Calculation of output voltage of three-phase rotating active solar inverter.
Among them:
Effective value of V single-phase voltage
U battery voltage
Total turns of W low-voltage coil
Partial voltage ratio of K high and low voltage windings
Ke conversion coefficient
- Performance of three-phase rotating active solar inverters
Transform the winding of a 400 watt DC motor into a three-phase winding, add permanent magnet poles and guide switches, and transform it into a 1000 watt three-phase rotating active solar inverter. Due to the lack of grid certification, its performance has not yet been tested through actual grid connection.
In the subsequent work, it is necessary to first set up a 220 volt residential power grid environment in the laboratory and test its performance.
This article elaborates on the design of three-phase rotating active solar inverters, which have three major advantages compared to PWM systems:
(1) Solved the problem of electromagnetic pollution. The three-phase current generated by it is a pure sine wave, which will not cause electromagnetic pollution to the power grid, solving the long-standing problem of electromagnetic pollution caused by solar inverters to the power grid.
(2) Greatly reducing the cost of solar inverters. The three-phase rotating active solar inverter designed in this article is modified from ordinary three induction motors and does not use expensive power electronic devices such as MOS or IGBT. The cost is 1/3 to 1/5 of the price of an active solar inverter operating in PWM mode.
(3) Improved RAMS. The three-phase rotating active solar inverter designed in this article does not have high-power power semiconductor devices, which improves reliability; Adopting a fully enclosed structure improves maintenance free performance.
Solar inverters can be widely applied in distributed household photovoltaic systems, with low cost and long lifespan and maintenance free performance, which contribute to the large-scale application of distributed household photovoltaic systems and have a positive effect on promoting carbon neutrality and peak carbon work.