In this report, we have proposed a diode clamped multilevel inverter using renewable energy. Now a days renewable energy is widely playing an important role in the field of generating electricity because it is pollution free, easily form and limitless. Among the renewable energy sources, the photovoltaic systems are mostly used because it is easily installable. Photovoltaic cells converts sunlight into electricity in the form of DC. For this converting purpose we want a suitable converter is needed which convert dc power into ac power. The multilevel inverters (MLI) can be used to convert dc into ac for integration of renewable energy sources into the conventional grids. But the conventional (MLIs) such as diode clamped (MLIs) require extra diodes with the active switches. This report proposed a new type of multilevel inverter which convert dc power into ac power using less number of switches. The proposed inverter can be to integrate the photovoltaic system into grid, which require the best their phase angle, amplitude, frequency, and grid voltage. The simulation on the proposed Seven level (MLI) has done in mat lab software and also results are verified.
Electrical energy generation from renewable energy sources such as sun, biomass, wind, tidal etc, are widely used due to the large consumption of electricity. Currently, people attract toward the (MLIs) multilevel inverters renewable energy systems because conventional (MLIs) such as coal, thermal, hydral, fuel etc are .We used renewable energy source, photovoltaic because it does not give any harm to the environment like it is pollution free, clean etc. The basic component of (PV) photovoltaic system is the solar cell. A solar cell directly converts energy of sunlight directly into electricity in the form of dc.
Components which have used:
? Solar plate
? Charge Controller
Working Of Each Component:
Diode is a device which has two terminals anode and cathode as shown in figure 1.1. In fig.1.1 the schematic symbol have shown that where the “+” terminal called the anode which is connected with the p-region and the “-” terminal called the cathode which is connected with the n-region. The main function of diode is to flow current in only one direction that’s why called it unidirectional device while it block current in other direction. The diode operates in three different states.
• Forward bias
• Reverse bias
When positive (+ve) side of battery is connected with p-type material and negative(–ve)side of battery is connected with N-type material across the diode, which has the effect of decreasing the PN junction diode width.
When positive (+ve) side of battery is connected with N-type material and negative (-ve) side of battery is connected with P-type material across the diode, which has the effect of increasing the PN junction diode width.
The diagram will makes you more the working of diode in forward and in reverse bias.
VI- Characteristics Of Diode
Transistor is bipolar device3 which has three terminals collector, emitter and base. There are two types of transistors BJT and FET. The BJT (bipolar junction transistor) transistor called as bipolar device because electrical charge carriers (electron and holes) are involved in making the current flow. The basic work of BJT is to amplify current that’s why it is called the current controlled device.
The BJT has two types NPN and PNP:
We have used PNP transistor in multilevel inverter.
Construction of PNP:
The construction of PNP transistor is shown in the figure below.
The emitter-base junction is connected in forward biased, and the collector-base junction is connected in reverse biased. Due to which the emitter pushes the holes in the base region. These holes produce the emitter current (IE). When these electrons move into the N-type semiconductor material or base, they combined with the electrons. The base of the transistor is thin and very lightly doped. Hence only a few holes combined with the electrons and the remaining are moved towards the collector space charge layer. Hence develops the base current (IB).
The collector-base region is connected in reverse biased. The holes which collect around the depletion region when coming under the impact of negative polarity attracted by the collector. This develops the collector current (Ic). The complete emitter current flows through the collector current IC.
Capacitor is a device which has two terminals which stores electrical charges.
Construction of Capacitor:
Capacitor has two plates called electrodes. In between two plates there is a die-electric material Such as air, paper, glass etc.
When we connect a battery means DC source with a capacitor the battery charges the capacitor until the capacitor’s voltage is equal to battery voltage. When we disconnect the battery the capacitor discharges.
• Photovoltaic cell or solar cell is a light sensor device that converts light energy into electric energy. Solar cells are basically PN junctions with a transparent P layer. Shining light on the transparent P layer causes a movement of electrons between P and N layers, thus producing a small dc voltage. Typical value is 0.5 V per cell in full sunlight.
The junction of dissimilar materials (n (+) and p (-) type silicon) creates a voltage, Energy from sunlight knocks out electrons, creating an electron, connecting both sides to an external circuit causes current to flow, In essence, sunlight on a solar cell creates a small battery with voltages typically 0.5 volt DC.
Conversion Of Efficiency PV Array Components
PV System Components:
• Modern PV cells are made from semiconductor materials.
• Different impurities are added to opposite ends of materials such as silicon or germanium, making one end the P-type and the other the N-type.
• The P-N junction between them is the potential barrier.
• The voltage gradient is formed in the depletion region because the energy level in the p-type layer is higher than the energy level in the n-type layer.
• Most of silicon PV cells are of the P on N type. The upper surface (P-type layer) is a light transparent layer.
• The P-N junction acts as a permanent electrical field. When the P-type layer is illuminated, the incident photons cause a flow of electrons and holes.
• The electrical field at P-N junction directs the flow of electrons toward the N-type layer and the flow of holes toward the P-type layer.
• The resulting unbalance of charges within the cell causes an EMF to be developed between two layers.
• The EMF can be measured with a high-sensitivity voltmeter.
• Vop refers to the open-circuit voltage of the PV cell.
• When a load resistor is connected across the surfaces, electrons and holes carriers flow through the circuit until the state of balance, called equilibrium is achieved.
• If the load resistor is replaced by a wire, the current in the circuit is called the short-circuit current Ish
• If a PV detector is not illuminated, V-I characteristic curve is similar to a general purpose diode.
• Curve 1 is the V-I characteristic of the PV cell excited by a weak illumination, and
• the curve 2 is the V-I characteristic of the PV cell excited by a strong illumination
• Light energy falling on a photoconductive cell will cause a change in the resistance of the cell. e.g cadmium sulphide
• When the surface of this device is dark, the resistance is high and vice versa
• A reflective-type of photoelectric sensor is used to detect the light beam reflected from the target.
Combining Solar Cells:
• Solar cells can be electrically connected in series (voltages add) or in parallel (currents add) to give any desired voltage and current,
• Power (Watts) output is calculated P = I x V
• Photovoltaic cells are typically sold in modules (or panels) of 12 volts with power outputs of 50 to 100+ watts.
• These are then combined into arrays to give the total desired power or watts.
Charge Controller controls the electric current which is added or drawn from electric batteries. It prevents the over Charging and may protect against overvoltage, which can the cause the battery life to be dead and also it can reduce the performance of the battery due to overcharging.
It is an electrolytic device having a chemical medium that allows the current to flow between the cathode and anode. The battery is used for DC loads.
The load is DC.
Inverter inverts the DC into AC.
The load is AC
• High efficiency for switching at fundamental frequency.
• It has ability to Pre-charge of capacitors is done while in groups as well.
• In three phase inverter, all three phases use a common Direct Current bus which reduces the requirement of capacitance.
• Efficient in back to back high-power connections.
• It has also an ability to work with SDCs.
• Its cost is Low.
• It requires less number of components.
• Its Quadratic relationship between number of diodes and number of levels is very difficult to calculate, especially when the number of levels increased and becomes stressful and you will surely want to avoid it.
• Real power flow is very difficult to understand.
• Difficult to maintain at certain time of charging and discharging level.
• If Charge increased more than three level it’s difficult to balance it.
• Limited output voltage.
• Used in high power motors.
• It is easy to interface the high DC power line and also in high Ac power line.
In this diode clamped multilevel inverter using renewable energy we have to reduced the THD (total harmonic distortion) up to 20.21 %. Smaller the THD makes the system more efficient.
For improving the (THD) total harmonic distortion of the voltage and current waveform for grid integration. There are so many techniques which can be used such as (PWM) pulse width modulation, hysteresis current control, multilevel H-bridge cascaded inverter etc. By using multilevel H-bridge cascaded inverter we have to reduce the THD. The proposed work focuses on proper formulation of values of three phase transformer leakage inductance is selected. THD of the output current and voltage waveform is analyzed with the use of FFT tool in MATLAB software.
Circuit Diagram Of Diode Clamped Multilevel Inverter Using Renewable Energy
Graphs Of Simulation On Matlab Software