With the increased proliferation of non-linear loads in today’s electrical networks and with the introduction to KVAh billing in a number of sates it has become important not only to provide fundamental reactive power ( through the use of capacitor banks) but also compensate for the distortion component of reactive power using suitable equipment for harmonic filtration.
As explained in the article on PF correction, the relationship between displacement PF and true PF in the presence of harmonics can be expressed by the following equation:
The pfdisp or cos φ is a measure of the distortion created by the current and voltage harmonics present in the supply system where as the pfdist is the ratio of fundamental active power to apparent power.
What shall be the PFtrue recorded by the meter when PFdisp is 0.78 and the THD values are 34% and 4% for current and voltage respectively.
= 0.78 x 0.91
Dual Compensation (Reactive Power + Harmonic Mitigation)
A Hybrid PF Correction Panel (commonly known as Hybrid Panel) has dedicated components that provide both reactive power ( required to improve pfdisp) and harmonic filtration equipment ( required to improve pfdist) so as to improve the pftrue near unit. The harmonic filtration equipment if correctly sized is also capable of delivering load balancing across the three phases.
Hence Hybrid Panels combine the following functions in a single devcie:
- Elimination of harmonic currents and voltages.
- Power factor correction (lagging or leading).
- Voltage variations (sags & swells) reduction.
- Voltage fluctuations (flicker) mitigation.
- Load balancing in three-phase systems.
- Controlled & selectable harmonic mitigation
The Hybrid Panels have switched capacitor banks and Active Harmonic Filter ( AHF) as the key building blocks often controlled using a common HMI cum control unit.
Shematic Diagram of a Hybrid Panel
Step Less Reactive Compensation
The Hybrid Panels are capable of providing stepless compensation for reactive power requirements which is not possible with conventional capacitor banks. The AHF component of the Hybrid Panel can provide reactive current ( lead or lag) as reuqired to ensure that the exact reactive power requirement to meet the set PF is provided that too at near real time basis.
Comparison of Hybrid Panels with conventional capacitor banks, reactor banks or passive harmonic filters.
- Equipment using variable frequency & speed drives (VFD & VSD)
- Arcing devices: Electric arc furnances (EAF), discharge-type lighting (fluorescent, sodium vapor and mercury vapor) and arc welders.
- Switch mode power supplies: Computers, TVs, battery chargers, LED lightings, PLC, etc.
- UPS systems.
- Solar Inverters and wind turbine generators.
- Modulated phase controllers, cycloconverters and thyristor-controlled AC voltage regulators.
- Saturable/rotating devices: Induction heaters, transformers, generators, reactors and motors.
- Installations with fast changing reactive power demand or highly dynamic loads like ball mills.
- Correction of leading power factor like in data centers allowing back-up generators operation.
- Railway electrification systems: Trains & trams.
- Loads with low power factor: Motors, cables, lightly loaded transformers, lighting, etc
To learn more about BITCON’s range of Hybrid Power Factor Correction panels, please visit (link to the hybrid panel page).
Referene materials: http://www.elcopower.com.my/