Active Power Filter (APF:Active power filter (APF) is a new type of power electronic device used to dynamically suppress harmonics and compensate reactive power. The reason why it is called active is that compared with passive LC filter which can only passively absorb harmonics of fixed frequency and magnitude, APF can control and actively output the magnitude, frequency and phase of the current by sampling the load current and separating each harmonic and reactive power, and respond quickly to offset the corresponding current in the load, thus realizing dynamic tracking compensation and compensating both harmonic and reactive power and imbalance.
二. Working Principle of APF
1. Dynamic active filter can filter 2 to 50 subharmonic at the same time and improve power quality in an all-round way.
2. Full digital control of DSP, 20KHz switching frequency, rapid response to dynamic load changes.
3. Response load changes within 40μs, with full response time less than 10ms(1/2 cycle ).
6. It has the function of automatic current limiting and will not overload.
7. Ability to compensate three-phase unbalance.
8. Single-phase dynamic compensation, not affected by system imbalance.
9, 3.8 inch QVGA display.
10. MODBUS Communication Interface Active Power Filter.
11. Using IGBT with speed up to 20KHz to eliminate harmonics perfectly.
12. Parallel installation mode, easy to install, easy to expand, up to 10 parallel connection.
13. High efficiency, full load loss less than 2.57.
14. Reduce the line loss, eliminate the heat of transformer and motor caused by harmonics, and achieve a large energy-saving system.
15. Reduce blackouts and time caused by harmonics.
16. Increasing Power Utilization Rate and Reducing Operating Cost.
17. The filtering effect of APF is not affected by the change of system impedance and can automatically suppress system resonance.
18. According to the distribution structure, local compensation, partial compensation or total compensation can be selected. CT can be located on the power or load side.
四、Economic benefits of harmonic control
1. Energy saving 5%-8%.
Seven 400KVAUPS uninterruptible power supplies in an IDC computer room cost about 15 million yuan in 2008, saving 1.1 million yuan in electricity charges and 7.3% in energy saving effect after harmonic control.
2. Capacity Reduction Reduces Investment in Transformers, Circuit Breakers and CablesA factory installed an active filter and returned a transformer to the power supply bureau, saving more than 1 million in investment to protect equipment and reducing equipment investment.The harmonic generated by the frequency converter in a paper mill in Henan burns down two blowers every month, resulting in a loss of 30,000 yuan per month.
3. Increasing productivity and maintaining continuous power supply.The daily output of an acrylic fiber factory increased from 197 tons to 210 tons after harmonic control.