Harmonics in the power system come from electrical equipment, that is to say, from generating equipment and electrical equipment.
1.Harmonic source (the harmonic source at the power supply end generally points to the electrical equipment that injects harmonic current into the public grid or generates harmonic voltage in the public grid). Some nonlinear devices will generate harmonics when they work in the grid. For example, single-phase rectifiers, electric arc furnaces, rectifiers, inverters, frequency converters, arc welding machines, induction heating equipment, electromechanical equipment with magnetic saturation, etc. Harmonics generated by electrical equipment, especially rectifier thyristor equipment, are commonly used in electric locomotives, Lu electrolyzers, switching power supplies, etc., and have a wide range of applications. Most rectifier thyristor equipment adopts phase-shift control, so it will leave a lot of harmonics to the power grid. According to technical data statistics, the harmonics generated by the rectifier device account for 40% of all harmonics, and are usually identified as the largest source of harmonics. Frequency conversion equipment generally adopts phase control, so the generated harmonics are more complex, usually including integer harmonics and fractional harmonics. Due to the high power of the frequency conversion equipment, the harmonic content generated will also increase. As well as household electrical equipment, because most of them have voltage regulating and rectifying devices, they will also generate deeper fundamental harmonics. At the same time, the change of the unbalanced current will also cause the change of the waveform. Due to the large number of household appliances, the total amount of harmonics generated is also very large. Most of them are switching power supply equipment based on power electronic components.
2. The transmission and distribution system itself will also generate harmonics. The main source of harmonics is the power transformer. Due to the saturation of the transformer core, the magnetizing current will show a peak waveform, that is, odd harmonics. The higher the saturation of the transformer core, the larger the harmonic current and the higher the harmonic content generated. It belongs to the iron core device with ferromagnetic saturation characteristics.
3. The power generation source is difficult to achieve absolute perfect symmetry in technology in the assembly and production of the three-phase winding of the generator set, and the iron core on the generator cannot be completely uniform in quality and texture, etc., resulting in the quality of the generated power. not high, resulting in harmonics.
4. Gas discharge electric light source. For example, fluorescent lamps, high-pressure sodium lamps, metal halide lamps, etc., because of their serious nonlinearity, will also cause odd harmonic currents to the power grid. It belongs to the equipment with arc as the working medium with strong nonlinear characteristics.
In order to limit the harmonics in the power system. Usually, the pulse number of the converter device is increased and an AC filter is installed. Strengthen harmonic management. The high and low voltage reactive power compensation device produced by Hongyan Electric, the high and low voltage integrated capacitor compensation device and the high and low voltage reactive power dynamic and static filter compensation device are all very reliable equipment for reducing harmonic hazards.
Post time: Apr-13-2023