Reactive Power Primer: Page 3 of 3 | SolarPro Magazine
Power factor is the ratio between active power and apparent power. The relation between the real power (kW), the apparent power (kVA) and the reactive . Feb 8, A difference of phase appears between the power in the grid and the power in the load. It can be seen as a simple RL circuit and as shown. power (called Q). In this part of article, real power and reactive power are explained in detail. Search for: Commercial Applications & Electrical Projects.
Reverse Real and Reactive Power Phasors
Declining component cost has hastened implementation of two different methods. The filter consists of capacitors or inductors, and makes a non-linear device look more like a linear load. An example of passive PFC is a valley-fill circuit. A disadvantage of passive PFC is that it requires larger inductors or capacitors than an equivalent power active PFC circuit.
- Power factor
- Understanding Power Factor and why it’s important
- Reverse Real and Reactive Power Phasors
Active power factor correction can be single-stage or multi-stage. In the case of a switched-mode power supply, a boost converter is inserted between the bridge rectifier and the main input capacitors. The boost converter attempts to maintain a constant DC bus voltage on its output while drawing a current that is always in phase with and at the same frequency as the line voltage.
Another switched-mode converter inside the power supply produces the desired output voltage from the DC bus.
Power factor - Wikipedia
This approach requires additional semiconductor switches and control electronics, but permits cheaper and smaller passive components. It is frequently used in practice. For a three-phase SMPS, the Vienna rectifier configuration may be used to substantially improve the power factor. That feature is particularly welcome in power supplies for laptops.
Dynamic PFC[ edit ] Dynamic power factor correction DPFCsometimes referred to as "real-time power factor correction," is used for electrical stabilization in cases of rapid load changes e. DPFC is useful when standard power factor correction would cause over or under correction.
Reactive Power Primer: Page 3 of 3
Importance of power factor in distribution systems[ edit ] 75 Mvar capacitor bank in a kV substation Power factors below 1. This increases generation and transmission costs.
For example, if the load power factor were as low as 0. Line current in the circuit would also be 1. Alternatively, all components of the system such as generators, conductors, transformers, and switchgear would be increased in size and cost to carry the extra current.
So the power wave form is first positive and then negative. To create this power flow the current lags behind the voltage by 90o. This to and fro flow of electrical power is called reactive and is caused by power devices that can store energy in a magnetic field motors, fluorescent lamps, etc.
The main electrical services comprising a typical load would be electrical motor, lighting, and heating devices. These entire loads will draw KW from the supply because they all provide power out puts, but motors and florescent lighting have coils and steel cores so they also require KVAr. From the diagram below: Temporary Storage of Energy: The blue line shows all the power is stored temporarily in the load during the first quarter cycle and returned to the grid during the second quarter cycle, so no real power is consumed.
Releasing the Stored Energy: As the reactive power is mainly due to the inductive effect, the current lags behind the voltage causing the lagging power factor to reduce the effect and reversal of reactive power to the active power, so we introduce a capacitance.
Thus the net effect is nullified to obtain the required real power. From a theoretical point of view, in a circuit of any topology, with sinusoidal or n-sinusoidal supply voltage, the apparent power S may be analytically decomposed into two components [ 6 ].
On the contrary, many definitions have been formulated to represent non-active power for n-sinusoidal situations in linear and nonlinear power systems.
It is our conviction that apparent power concept should be represented by a set of adaptable orthogonal terms to any association criteria.
Starting with the works of Budeanu and Fryze, numerous valuable works have appeared [ 8 — 11 ] aimed to characterize the power equation into different components, among them reactive and distortion powers, with diverse names and meanings without a powerful reason for it.
But none of these have succeeded in defining a concept that not only accounts for the total non-active power but also satisfies a multivectorial representation. The discussion on this matter is still open, and there is not yet a generalized power theory that can be assumed as a common base for power quality evaluation and harmonic source detection. It is well known that the distorted current causes disturbances on the supply side, because of the nonzero impedance of the source.
The load side of the power system also is affected by the distorted currents. However, in some applications this approach is not appropriate to provide correct information about the source producing harmonic distortion. Furthermore, some approaches have been proposed for evaluation and detection harmonic sources.
They can be mainly classified in two groups, single-point and multipoint measurement methods [ 13 ]. Both techniques have their advantages and disadvantages. Unfortunately, in some practical applications, these approaches cannot provide correct information about the customer and the supply side harmonic contributions.
Nevertheless, we must recognize that single-point method presents many advantages as simple instrumentation, low cost, and easy implementation. For all this, we believe that a good solution to the problem can be the measure of a multivectorial index with its three attributes, magnitude, direction, and sense, which carries all necessary information. This index is based on the power multivector concept [ 14 ].