What is harmonics? What causes harmonics?
Harmonics are products of modern electronic and mechanical devices such as computers, electricity storage systems, inverters, arc furnaces, renewable energy converters and many other things. They are often called nonlinear downloads. These nonlinear loads create different harmonic components and return the grid through the wire network, in combination with the basic power frequency, creating distortion and distortion of the total wave in the distribution system. energy.
Harmonics are periodic, sinusoidal waves and are integer multiples of the fundamental frequency (50 or 60 Hz). These components, when added to the original sine wave (50Hz), will cause distortion and sine wave distortion.
Deformation of harmonics
The inverters are currently used a lot in modern industry for motor control, running ships, drilling rigs, pumps, fans … and this is the source of extremely popular harmonics.
Harmonics in the industries
Harm of harmonics and the reason why it is necessary to filter harmonics
What we should know is why harmonic filtering is due to harm of harmonics. Harmonics cause serious problems for the electrical system and equipment system of the plant such as unexpected damage of machinery causing stagnant operation, fire and explosion causing danger to human life, power loss energy … The following are common harms of harmonics:
– The harmonic components add virtual power to the total power consumption of the transformer, making the transformer overload, heat and burn even though the load only consumes the average power.
– Heat and fire conductors cause serious losses in electrical systems.
– Neutral conductors in 3-phase systems are heated or burned.
– N-G (neutral-earth) voltage is too large.
– CB off for unknown reasons.
– Broken PF reactive compensation capacitor.
– Interference in the communication system. The capacitor and transformer resistance can form a resonant LC circuit that causes harmonics to cause multiple capacitors and transformers, resulting in capacitor and transformer fire.
In particular, for systems that use standby generators or use on ships, rigs, and when running, due to the higher resistance characteristics of the transmitter than conventional transformers, harmonics will be Excessive amplification from 3 to 4 times, serious damage to equipment systems and even fire generators is dangerous and expensive.
The effect of harmonics can cause serious damage to devices
Methods to reduce harmonics
Replacing damaged devices that are caused by harmonics is an expensive solution, increasing investment costs and operating costs but still cannot reduce the effects of harmonics. Therefore, it is necessary to select less costly but highly effective solutions in controlling harmonics:
- + Using AC reactors or DC reactors for the inverter – the best solution for grid filtering applications with heavy loads and reduced harmonic requirements is not a top priority.
- + 12-pulse rectifier solution – gives the highest performance in reducing harmonics but the process is most complex
- + Using low frequency harmonic inverters – The inverter uses harmonic reduction technology without the use of an external filter or multi-pulse transformer with a total harmonic distortion (THDi) of less than 5%.
- + Using filters – is applied to many inverters that are parallel to each other on the same distribution line with the main task of power compensation, voltage harmonic compensation and current harmonic compensation.