Multi-stage injection current source inverter

The concept of harmonics injected power converters have been used in the history of half a century . But the harmonic injection for power converter as a way to reduce the harmonic content . Multi-stage injection current amplitude and phase matching conditions of work , through the use of additional thyristor trigger control and achieve a natural commutation ripple voltage , frequency and phase of the injected current synchronized with the power supply . Based on the fixed relationship between the amplitude of the injected current and direct current , the optimal harmonic suppression is guaranteed for all operating conditions , the DC voltage waveform and the alternating current waveform quality is further improved. In the literature , the concept of a new injection of DC current , and found six times the fundamental frequency of the injected current with the pulse current source converter 12 can play full effect of suppressing harmonics . Which research methods to find unconventional system of injection current waveform amplitude , so as to achieve a minimum harmonic distortion rate . And rigorous mathematical analysis summarized this idea , the ability to completely eliminate export standard 12-pulse current source  2000 watt power inverter   AC output waveform measured ideal harmonic injection waveform. 12-pulse current source converter , the operating mode of the main circuit and the general three-phase full-controlled bridge converter same , each bridge in six 60 ° intervals sequentially triggered thyristor conduction, each main switch is turned on 120 bridge °. Thus, for two parallel three-phase full -controlled bridge , the bridge every 30 ° to trigger a switch arm , any time there are two switch conduction. It does not change with the AC system voltage , system synchronization and communication connections can also be run as a rectifier and an inverter operation . When the active power fed from the AC system to the DC system , the state of the rectifying operation of the apparatus , when the conveying system to the alternating current from the active system , the device in the inverter state . Multi-stage injection current source  Off grid inverter  (MLCR-CSC) DC voltage can be positive or negative, the converter requires the use of a switching device with symmetrical features , namely bi-directional voltage blocking capability and unidirectional current flow capacity of the device has . So IGBT can not be directly used for MLCR-CSC, diode and IGBT series to meet this performance requirement , but the device will cause a series of additional power loss. Since MLCR-CSC relatively low switching frequency, suitable for high-power thyristors MLCR-CSC. Due to the presence of DC side inductance , making DC current flow in one direction , while the DC voltage polarity may change instantaneously , so the multi-stage injection current source inverter switching devices need to be bi-directional voltage blocking capability and unidirectional current flow capacity .