Four quadrant frequency converter suppliers remind you that most ordinary frequency converters use diode rectifier bridges to convert AC power into DC power, and then use IGBT inverter technology to convert DC power into AC power with adjustable voltage and frequency. This type of frequency converter can only operate in electric mode, so it is called a two quadrant frequency converter. Due to the use of a diode rectifier bridge in the two quadrant frequency converter, it is impossible to achieve bidirectional energy flow, so it is not possible to return the energy from the motor feedback system to the power grid. In some applications where electric motors need to feedback energy, such as elevators, elevators, and centrifuge systems, a resistance braking unit can only be added to the two quadrant frequency converter to consume the energy feedback from the electric motor. In addition, in some high-power applications, diode rectifier bridges cause serious harmonic pollution to the power grid.
In order to enable the frequency converter to operate in the power generation state, feedback the braking energy to the grid, reduce energy consumption, and achieve four quadrant operation, there are usually two methods:
1. Equip the frequency converter with one or more energy feedback units, which can be connected in parallel to feed back energy to the grid, but cannot automatically adjust the bus voltage, harmonics, and power factors. This method is low-cost and can reduce energy consumption to a certain extent, but the effect is relatively low, and it has no optimization or protection function for the operation of the frequency converter;
2. Equipping a frequency converter with an active front-end, commonly known as AFE, can achieve controllable rectification and energy feedback. The bus voltage and power factor can be adjusted, effectively reducing harmonics. Within a certain range, the impact of bus voltage fluctuations can be basically ignored. This method is effective, but the cost is relatively high. It is usually used in situations where power factor requirements are high or frequent braking is needed, such as elevators, mine lifting and lowering, lifting and lowering, etc.
Introduction to Active Front End AFE
The active front-end can achieve controllable rectification and energy feedback. Our MD050 is the active front-end, which is different from ordinary energy feedback units. The active front-end processor is a high-speed DSP chip that can achieve controllable rectification. The power factor is very high, usually up to 99%, and the harmonic is very small, usually less than 5%. The bus voltage is adjustable, and even if the input voltage fluctuates, it can ensure a constant bus voltage within a certain range.