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Solar PV system:

• A photovoltaic (PV) system is composed of one or more solar panels combined with an inverter and other electrical and mechanical hardware that use energy from the Sun to generate electricity.
• The light from the Sun, made up of packets of energy called photons, falls onto a solar panel and creates an electric current through a process called the photovoltaic effect.
• The electricity produced from a solar panel (or array) is in the form of direct current (DC).
• Therefore, in order for solar electricity to be useful, it must first be converted from DC to AC using an inverter.
• This AC electricity from the inverter can then be used to power electronics locally, or be sent onto the electrical grid for use elsewhere.

The underground cable has more initial cost as compared with the overhead system for the same voltage as the insulation required for underground cable is more compared to overhead lines.

Comparison between the underground and overhead transmission line

1. The voltage and current rating of the overhead line are greater than underground cable.
2. Underground cables need more insulation. It is because the whole conductor is required coated with the insulation sheath.
3. Underground cables do not cause interference to the communication lines as these are buried under the earth's surface.
4. Overhead lines have high maintenance costs as compared to underground cable.
5. In the case of an overhead line, the risk of explosion or fire is more.

A voltage dip motor is not a type of 1ϕ induction motor.

Types of 1ϕ induction motor:

1.) Resistance split phase motor:

• It has a single cage rotor, and its stator has two windings known as main winding and starting winding. Both the windings are displaced 90 degrees in space.
• The main winding has very low resistance and a high inductive reactance whereas the starting winding has high resistance and low inductive reactance.
• A resistor is connected in series with the auxiliary winding. The current in the two windings is not equal as a result, the rotating field is not uniform. Hence, the starting torque is small, of the order of 1.5 to 2 times the stated running torque.

2.) Capacitor start motor:

• Capacitor Start Motors are single-phase Induction Motors that employ a capacitor in the auxiliary winding circuit to produce a greater phase difference between the current in the main and the auxiliary windings.
• I_M is the current in the main winding which is lagging the auxiliary current I_A by 90 degrees.
• Thus, a single-phase supply current is split into two phases that provide the starting torque to the motor.

3.) Two-value capacitor motor:

• There are two capacitors in this method one is used at the time of the starting and is known as starting capacitor. The other one is used for the continuous running of the motor and is known as the RUN capacitor.
• In the starting, the two capacitors are connected in parallel. The capacitor Cs is the Starting capacitor that is short-time rated.
• As the motor reaches the synchronous speed, the starting capacitor Cs is disconnected from the circuit by a centrifugal switch Sc.
• The capacitor CR is connected permanently to the circuit and thus it is known as RUN Capacitor. The run capacitor is long-time rated and is made of oil-filled paper.

The Sun tracker method cannot be used for MPPT control of wind turbines.

The Sun tracker method is used in MPPT control of the solar system.

The MPPT control method of the wind turbines are:

1.) Tip speed control​

2.) Optimum torque control 

3.) Highest electro-power control 

4.) Power signal feedback control

5.) Hill climb search control

Discharge Lamps:

• In all discharge lamps, an electric current is passed through a gas or vapor which renders it luminous.
• The elements most commonly used in this process of producing light by gaseous conduction are neon, mercury, and sodium vapors.
• The colors (i.e. wavelength) of light produced depend on the nature of the gas or vapor.
• For example, the neon discharge yields orange-red light of nearly 6,500 A.U. which is very popular for advertising signs and other spectacular effects.
• The pressure used in neon tubes is usually from 3 to 20 mm of Hg.
• High-pressure mercury vapor lamps, Neon lamps, Sodium vapor lamps, etc are examples of discharge-type lamps.
• Mercury-vapour light is always bluish-green and deficient in red rays, whereas sodium vapor light is orange-yellow.
• The discharge lamps work on the discharge phenomenon i.e, the voltage needs to discharge the ion from one side of the electrode to another side due to this high voltage is needed to pass the ion than the current so the current will lag behind the voltage at the normal working time.
• Hence Discharge lamp working at a lagging power factor.
• Due to the addition of the Choke and Capacitor, it has a high initial cost.
• It required approximately 5 minutes for starting due to the ionization process phenomena.

Types of semiconductors

1.) P-Type semiconductor

• When trivalent impurity atoms such as indium, and gallium are added to an intrinsic semiconductor, it is known as a p-type semiconductor.
• These semiconductors have 3 valence electrons, therefore accepting one electron to complete its outermost shell. Hence, it is also known as the acceptor atom impurities.
• The majority of charge carriers are holes & minority charge carriers are electrons.

2.) N-Type semiconductor

• When pentavalent impurity atoms such as antimony and arsenic are added to an intrinsic semiconductor, it is known as an n-type semiconductor.
• These semiconductors have 5 valence electrons, therefore donating one electron to complete its outermost shell. Hence, it is also known as the donor atom impurities.
• The majority of charge carriers are electrons & minority charge carriers are holes.

Irradiance and PV output

Irradiance is the amount of light energy which reaches the surface of the receiver with a square meter in a second.

Power output from the solar panel is proportional to the intensity of solar irradiation.

When all parameters are constant, the higher the irradiance, the greater the output current, and as a result, the greater the power generated.

The effect of irradiance on the I-V curve of the PV module is shown below:

PV curve of the solar system:

• The PV curve of solar PV is non-linear.
• A PV device, such as a solar module, produces its maximum current when there is no resistance in the circuit.
• This maximum current is known as the short circuit current.
• When the module is shorted, the voltage in the circuit is zero.
• These two extremes in load resistance, and the whole range of conditions in between them, are depicted on the I-V curve. Current, expressed in amps, is on the (vertical) y-axis. Voltage, in volts, is on the (horizontal) x-axis .
• The power available from a photovoltaic device at any point along the curve is just the product of current and voltage at that point and is expressed in watts.
• At the short circuit current point, the power output is zero, since the voltage is zero. At the open circuit voltage point, the power output is also zero, but this time it is because the current is zero.

Hysteresis Loss

During the cycle of magnetization and demagnetization of magnetic substances, energy is spent and this spent energy appears in the form of heat. This heat loss is known as hysteresis loss.

The hysteresis loss is given by:

\(P_h=K_h f(ϕ)^x\)

where, P_h = Hysteresis loss

f = Frequency

x = Steinmenz constant

ϕ = Flux

Hysteresis loss depends on the volume of material, class of material, frequency & flux density.

Active power and reactive power are unknown parameters for slack or reference buses.

Classification of the bus in load flow analysis

where, P = Active Power

Q = Reactive Power

V = Voltage

δ = Load Angle