Three-phase parallel ac active harmonic filters used to mitigate decreasing voltage distortion

Three-phase parallel ac active harmonic filters used to mitigate decreasing voltage distortion

Description

The wide application of nonlinear power equipment produces a lot of distorted current harmonics, which cause harmonic voltage when flowing in power grid. This harmonic pollution threatens the safety and stability of power system seriously. Together with electromagnetic interference, power factor reduction, are the three major public hazards for power system. 

Active power filter(APF/AHF for short) is a perfect comprehensive solution to power quality problems with power grid such as harmonic wave(can filter 2nd to 50th harmonic interference completely), reactive power, and 3 phase load unbalance.APF is connected in parallel in power grid, to detect the harmonic wave in power grid in real time, generate the reverse-phase compensation current through the converter, and dynamically filter the harmonic wave in power grid. The operation of APF is unaffected by power grid structure and load type, and it will not produce harmonic oscillation with the system, thus perfectly realizing harmonic wave control of various loads. APF can also realize dynamic reactive compensation, and control the capacitor switching, to improve the power factor of power grid. Meanwhile, APF has the function of controlling the 3 phase load current unbalance, thus comprehensively solving various power quality problems with power grid.

Installation method

Working principle

Application Site

Active Harmonic Filtering technology can be applied to wide range of industrial or commercial environments where good power quality is essential. Active Harmonic Filters have been used for the processes that use variable speed drives (VSD), fast fluctuating loads such as welding machines, uninterrupted power supply (UPS) systems and DC load, single phase loads such as lighting and computers as well as electric arc furnaces and rolling mills.in addition,applications in data centers & IT, hospitals and laboratories,shopping malls,wind and solar farms,metro stations,steel industry,pharmaceutical industry etc.

Advantages

1. It can filter out harmonic currents below 2~50 times at the same time, so that the current distortion rate of the power supply side is THDI<3% at full load, and THDI<4% at half load;

2. Working mode: filter harmonics, reactive power compensation, filter harmonics and reactive power compensation, and set the priority of functions;

3. Using sliding window iterative DFT detection algorithm, fast calculation speed, instantaneous response time is less than 0.1ms, device compensation full response time is less than 10ms;

4. The original adaptive current average value control algorithm is adopted to narrow the frequency spectrum of the high-frequency harmonics generated by the IGBT of the device itself, and the output current distortion rate is less than 2.5%;When the three-phase load current is unbalanced, the filter can normally compensate and eliminate the unbalance phenomenon;

5. Using reliable current limiting control links, when the harmonic current in the system is greater than the device capacity of the active filter, the filter can automatically limit the current at 100% capacity output.

6. The switching device adopts the IGBT of the international famous brand, which is extremely reliable, combined with the unique active clamping technology, to ensure that the IGBT will not have an over-voltage explosion tube failure under any extreme conditions.

7. The main circuit adopts 3H bridge type three-level structure, the output waveform quality is high, and the switching loss is lower.

8. Adopting high-definition touch screen, easy to operate, real-time display system and device operating parameters on the screen, with fault alarm and recall function;

9. The output filter adopts the LCL structure, which not only prevents the high-order harmonics generated by the IGBT high-frequency switch during ZBAPF compensation from being injected into the grid, the compensation effect is better, and it is also adaptable in any on-site grid system impedance, resonance will not occur, ensuring the safety of the installation;

10. Use Xilinx's military-grade FPGA for centralized control. The FPGA clock frequency can be up to 200MHz. There are 84 hardware DSP units inside. DSP runs in parallel. The operation speed is much higher than that of a single DSP control method. The communication delay is small and the response speed is faster. The program needs to be called, and the anti-interference ability is strong, and there will be no program runaway failure.

11. 12 devices can be connected in parallel and only one FPGA controller can be used for centralized control.

12. The input end of the active filter is equipped with a reliable lightning surge protection device. When a lightning wave occurs, the protection device plays a protective role and does not damage the equipment.

Technical Parameters

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