The principle of solar inverters

Usually convert ac power to dc can call rectification, the process of phase controlled rectifier is one of the most common ac to dc conversion process; And call direct current process which can transform into ac power inverter, it is the inverse process of rectification. In the inverter circuit, according to the properties of the load, inverter can be divided into active and passive inverter inverter. If the ac side of the circuit to the ac power, convert direct current (dc) can pass straight - communication, inverter to the ac power up with frequency alternating current (ac) to return to the grid, called active inverter. The corresponding device is called active inverter, control Angle is greater than 90 ° phase rectifier for common active inverter. And direct current (dc) can transform into ac power, directly to the power supply circuit, power supply load is called passive inverter circuit, also known as the frequency converter.
Inverter type has separately excited, self-excitation inverter,  2000 watt power inverter  pulse width modulation (PWM) inverter. Which he excitation voltage source inverter need external communication, provide thyristor rectifier voltage. He wound inverter is mainly used in high power grid; Whose power is less than 1 mw photovoltaic power generation systems, mainly adopts the way of self-excitation inverter. Self-excited does not require an external voltage source inverter, rectifier voltage by the  2500 watt power inverter  part of the energy storage element (such as capacitance) to provide or by increasing stay shut off rectifier valve (like MOSFET and IGBT) resistance value. Be self-excited pulse modulation inverter output voltage is called the pulse inverter. This kind of inverter pulse switching times, by increasing the cycle to reduce the harmonic content of voltage and current; Harmonic content was positively than with pulse switching times. At present, the output of the grid inverter control mode there are two main types: voltage type control mode and current mode control mode. Voltage type control mode based on the principle of the output voltage controlled quantity, as the system output voltage and power grid of the same frequency and phase of voltage signal, the whole system is equivalent to a controlled voltage source internal resistance is small; The principle of current mode control mode is output inductor current as control target, the system output voltage and power grid of the same frequency and phase current signal, the whole system is equivalent to a larger internal resistance of the controlled current source.
At present, there are many kinds of solar inverters, topology structure, the most common of which are used for single-phase half bridge, bridge and HerIC (Sunways patent) inverter, as well as six pulse for the three-phase bridge and midpoint clamping (NPC) inverter. Solar inverter four commonly used the typical architecture of full bridge topology of the switch