The DC reactor for the inverter is also called the flat wave reactor, which is connected in series in the DC bus (terminals P1 and P+). The main thing is to reduce the higher harmonic component of the input current and improve the power factor of the input power supply (to 0.95). This reactor can be used at the same time as the AC reactor, and the DC reactor is only considered when the power of the inverter is greater than 30kW.
The DC reactor is connected to the filter capacitor, which suppresses the amplitude of the inrush current after rectification into the capacitor, and improves the power factor and reduces the bus communication pulsation. The greater the power of the inverter, the more DC reactor should be used, because there is no DC reactor, the capacitance filter of the inverter will form severe distortion of the current waveform and make the grid voltage waveform severe distortion, and it is very harmful to the rectifier bridge and filter capacitor life of the inverter.
DC reactor is used to improve the input current waveform distortion and improve the power factor, reduce and prevent the rectifier bridge damage and capacitor overheating due to the impulse current when the resistance of the power transformer and transmission line is small, and the power grid transient frequency is frequent. The DC reactor can make the operation of the inverter link more stable and can constrain the short-circuit current.
The selection of the inductance value of the DC reactor is generally 2-3 times of the 3% impedance inductance of the inverter communication reactor, and at least 1.7 times, that is
LCD=(2——3)LAC
Example: Calculation of DC reactor for three-phase 380V90kW inverter:
LCD=(2——3)LLA1=(2——3)×0.123=0.246——0.369mH
Select a reactor with an operating current of 170A and an inductance of 0.2mH.
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