Represented by:

Qasim Mohammed Abbas

CONTENTS: Abstract. Introduction . Loads types: 1. Linear Loads. 2. Non-Linear Loads. The Reasons of Harmonics. What are Harmonics ? The Power Factor. Disadvantage of Low Power Factor. Power Factor Parts: 1. Displacement P.F. 2. Distortion P.F. Power Factor Correction Methods: 1. Passive P.F.C. 2. Active P.F.C. 3. Dynamic P.F.C. Techniques of P.F.C. Methods In Some Applications. P.F.C.’s Advantages Diagram. Conclusion.

we will introduce in this presentation some methods that are used for converting the non-linear load circuits into that linearity. In order to rise its efficiency and to be utilizing of the entire real power, by deleting the continuous fluctuating effect of the reactive power. All in all, we can get this via power factor correction methods.

Generally, the direction of power transmission must be from the source to the load, in order to give useful energy and it is represented in consumed real power(P)during the time. Also, this real power is always absorbed in the resistors only. Meanwhile, the direction of reactive power(Q)is fluctuating(Bi-directional)from the source to the load and vise versa, by the capacitors and the inductors in load circuits. Since, the inductors(reactors) are consuming(sink)the reactive power(+Q), and the capacitors are charging(generate)reactive power(-Q) in the loads. Whereas, these processes(sinking & generating)for reactive power, have been disturbing the voltage source and causing power losses. All in all, it is necessary to improve load circuits and to make the power in one direction, through deriving just the real power(P)by using a suitable power factor correction method for this important target.

TYPES OF LOADS:

1.Linear Loads:

The load current that is drawn has a sinusoidal waveform and it is subjected to a sinusoidal voltage waveform. Fig. shows a linear load. Current and voltage in phase, unity power factor.

2. Non-Linear Loads:

The load current that is drawn has non-sinusoidal waveform(Distorted),because it has harmonics but it is also subjected to a sinusoidal voltage waveform.Fig. shows a Non-Linear load with phase angle=45 Degree.

The main reasons are:•Loads nature ; is non-linear such as heavily inductive loads.•Non-Linear loads; as the Power Electronics devices , fluorescent lamps, arc furnaces,…, e .t .c . •Operational oscillation of network; where the automatic loading change results to un balanced loading in network.

The distortion waveform of current or(voltage) in non-linear load is analyzing into a big integer number of the sinusoidal components. The first component is called the fundamental and it has the same frequency of the source, and it apply on it(In phase) generating real power in the load. Whereas, the other sinusoidal components have a high frequencies(or; multiple of fundamental’s frequency. So, they are not applying on source voltage wave. In addition, each one has a certain amount of reactive power(+Q or –Q)according to that of current’s lagging or leading, with respect to applied source voltage in the load circuits. By summation of the components’ reactive powers, we get a total reactive power of the distorted load current wave. If these harmonics are not treated or corrected, it will cause more losses in a complex power(S)of the voltage source and they make(Distort)the sinusoidal source current waveform because of its high frequencies.

These harmonic components are making(Hysteresis and Eddy currents)losses in the synchronous machines, because of their high frequencies. The(3rd)third harmonic component in three phases system causes heating losses in(Y-connection), it makes(overload heating)because of the high current(over current)flowing in the neutral wire. Also, it makes (Copper Losses)in(Delta-connection), because of its circulating around in three phase windings. Additionally, in three phases system some of these components which have a negative-sequence such as(5th , 7th , 11th ), so they have a (-ve torques); that cause a mechanical Losses(rotating torque decreasing & vibration due to its high frequency) in the large synchronous machines.

Samples Of Harmonic Waveforms

THE POWER FACTOR: It is the ratio of the real power(P)to the apparent power (S), it is a dimensionless amount, it is ranging(0 1ـــ ), and it has a lag or a lead depending on the phase

angle between the load current and the applied voltage.

DISADVANTAGES OF LOW POWER FACTOR:

• This increases in generation and transmission(big size of OHTL& Cables) costs.

• Loss in distribution capacity.

• More Transformers.• Large size for

conductors, circuit breakers, and the other equipment.

POWER FACTOR IS DEVIDED INTO;1.DISPLACEMENT P.F. :

It is the power factor that is arising in load circuits because of the difference in the phase angle between the current and the voltage in the load.

2.DISTORTION P.F. : It is a measure of the distortion amount of the load current because of the harmonics, and they are decreasing the rate of the transmission real power to the load.

1.PASSIVE P.F.C. METHOD : This method is more ease for controlling on the load harmonic distorted current. Because, it uses a power filter and the later is passing of the load distorted current at one specific frequency(source frequency)only. This filter is consisting of group of capacitors and connection contactors.Its disadvantages are:•It needs more capacitors and contactors to operate.•Its P.F. values are low, it range(0.6-0.7-0.8)This method has two ways(methods) in using:A- Static Method:B- BULK Method.

PASSIVE P.F.C. WAYS :A- STATIC METHOD:Capacitors are connected at each starter and controlled by the starter itself.

B- BULK METHOD:Capacitors are connected at the distribution board and controlled independently.

2. ACTIVE P.F.C. METHOD: This method has a very good P.F. ,because it is ranging from(0.90)to(0.95), so it is better than the previous method. Also, this method has two main ways(methods), are:A- Using of the Power Electronics devices in order to change the waveform of the load distorted current. This is happening by releasing an Anti-Harmonic waves in load circuit to improve its power factor. This way may be done in single or multi-stage.B- By using the Synchronous Condenser(or, No-Load Synchronous Motor)method, whereas it is controlling in excitation field current and for making it a lead to eliminate the inductive effect of the load circuit. Beside, it is placed near of the power generation plants.

ACTIVE P.F.C. APPLYCATIONS 1.Active P.F.C. for (PSU)power supply unit:

2.Active P.F.C. for Synchronous Condenser:

POWER FACTOR CORRECTION METHODS:3. DYNAMIC P.F.C. METHOD: It is called(REAI-TIME P.F.C.)method too, and it is used for electrical stability in cases of rapidly loading change as the large industrial loads. Moreover, Dynamic P.F.C. method is going on improvement of high and low power factor. Also, in this method is largely using switches of Semiconductors, especially the thyristors(SCR’s)in order to connect/disconnect the capacitors and reactors(inductors) to the network(such as FACTS’ family devices)which are in fast correcting the power factor.Figure shown below for Static Var Compensator (SVC)single diagram:

* STATCOM AND STATIC VAR COMPENSATOR(FACTS).* AUTO POWER FACTOR UNIT.* ADVANCED EXCITOR.* SYNCHRONOUS CONDENSER(SM).* HARMONIC SUPPRESSION POWER FILTERS.* C-BANK FILTER.

DIAGRAM FOR ADVANTAGES OF P.F.C. METHODS:

More efforts are exerted in development and detection of the new techniques to improve the power factor, let to utilize of the electrical energy is large. Also, to benefit of the economic operation of the power system without losses. Finally, the lowest costs for both the consumer and the supplier, and getting assimilation for more distribution capacity at the same generated energy amount.