Introduction of Electric Car

You need the following to get started:

- Detailed pre-plans on how to construct your own electric car.

- You can use any vehicle- gas, diesel 

- A garage, shop or barn is nice, but not necessary 

- Simple tools every home workshop has- wrenches, drills etc. 

- A large DC motor (9 inches or larger) and a source of  batteries. Note that AC motors can be used as well but they are a bit more expensive so we went with DC. They are easier to install too. 

- You can, of course buy all these parts brand new but this is the heaviest cost of the whole project so we suggest using the sources of free DC motors and free industrial batteries listed in the plans. 

- They’re not hard to find either and since a DC motor will run for probably longer than you will own your car, using salvaged motors makes sense.

- After obtaining your DC motor and batteries you have to remove your gas engine from your car. 

- Leave the clutch and flywheel assembly and detach the rest. That will leave you room for batteries and DC motor mounting. 

- It is imperative that you only use a standard transmission vehicle for your conversion as automatic transmissions simply won’t work. 

- Don’t worry, you won’t even have to shift gears in traffic once the conversion is done. It will drive just like an automatic transmission, which is nice. Put it in gear and go. When you stop the engine simply stops too. It doesn’t keep idling, requiring clutching like a gas engine. 

Electric Car

Learning how to build your own electric car is a lot of fun too. Putting together the controller and motor assembly is not that difficult either. 

Your new Electric car will be able to go 50 mph and travel up to 200 miles on a single charge too. Isn’t it amazing. Try it!!

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WORKING PRINCIPLE OF STEPPER MOTOR

Stepper motors consist of a permanent magnetic rotating shaft, called the rotor, and electromagnets on the stationary portion that surrounds the motor, called the stator. Figure 1 illustrates one complete rotation of a stepper motor. At position 1, we can see that the rotor is beginning at the upper electromagnet, which is currently active (has voltage applied to it). To move the rotor clockwise (CW), the upper electromagnet is deactivated and the right electromagnet is activated, causing the rotor to move 90 degrees CW, aligning itself with the active magnet. This process is repeated in the same manner at the south and west electromagnets until we once again reach the starting position.

Figure 1

In the above example, we used a motor with a resolution of 90 degrees or demonstration purposes. In reality, this would not be a very practical motor for most applications. The average stepper motor's resolution -- the amount of degrees rotated per pulse -- is much higher than this. For example, a motor with a resolution of 5 degrees would move its rotor 5 degrees per step, thereby requiring 72 pulses (steps) to complete a full 360 degree rotation.

You may double the resolution of some motors by a process known as "half-stepping". Instead of switching the next electromagnet in the rotation on one at a time, with half stepping you turn on both electromagnets, causing an equal attraction between, thereby doubling the resolution. As you can see in Figure 2, in the first position only the upper electromagnet is active, and the rotor is drawn completely to it. In position 2, both the top and right electromagnets are active, causing the rotor to position itself between the two active poles. Finally, in position 3, the top magnet is deactivated and the rotor is drawn all the way right. This process can then be repeated for the entire rotation.

Figure 2

There are several types of stepper motors. 4-wire stepper motors contain only two electromagnets, however the operation is more complicated than those with three or four magnets, because the driving circuit must be able to reverse the current after each step. For our purposes, we will be using a 6-wire motor.

Unlike our example motors which rotated 90 degrees per step, real-world motors employ a series of mini-poles on the stator and rotor to increase resolution. Although this may seem to add more complexity to the process of driving the motors, the operation is identical to the simple 90 degree motor we used in our example. An example of a multipole motor can be seen in Figure 3. In position 1, the north pole of the rotor's permanent magnet is aligned with the south pole of the stator's electromagnet. Note that multiple positions are aligned at once. In position 2, the upper electromagnet is deactivated and the next one to its immediate left is activated, causing the rotor to rotate a precise amount of degrees. In this example, after eight steps the sequence repeats.

Figure 3

The specific stepper motor we are using for our experiments (ST-02: 5VDC, 5 degrees per step) has 6 wires coming out of the casing. If we follow Figure 5, the electrical equivalent of the stepper motor, we can see that 3 wires go to each half of the coils, and that the coil windings are connected in pairs. This is true for all four-phase stepper motors.

Figure 4

However, if you do not have an equivalent diagram for the motor you want to use, you can make a resistance chart to decipher the mystery connections. There is a 13 ohm resistance between the center-tap wire and each end lead, and 26 ohms between the two end leads. Wires originating from separate coils are not connected, and therefore would not read on the ohm meter.

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Auto Transformers basics.....

  An auto transformer is an electrical transformer having only one winding. The winding has at least three terminals which is explained in the construction details below.

Some of the advantages of auto-transformer are that,

• they are smaller in size, 
• cheap in cost, 
• low leakage reactance,
• increased kVA rating, 
• low exciting current etc. 

An example of application of auto transformer is, using an US electrical equipment rated for 115 V supply (they use 115 V as standard) with higher Indian voltages. Another example could be in starting method of three phase induction motors. 

Construction Of Auto Transformer

 An auto transformer consists of a single copper wire, which is common in both primary as well as secondary circuit. The copper wire is wound a laminated silicon steel core, with at least three tappings taken out. Secondary and primary circuit share the same neutral point of the winding. The construction is well explained in the diagram. Variable turns ratio at secondary can be obtained by the tappings of the winding (as shown in the figure), or by providing a smooth sliding brush over the winding. Primary terminals are fixed.

Thus, in an auto transformer, you may say, primary and secondary windings are connected magnetically as well as electrically.

Working Of Auto Transformer

As I have described just above, an auto transformer has only one winding which is shared by both primary and secondary circuit, where number of turns shared by secondary are variable. EMF induced in the winding is proportional to the number of turns. Therefore, the secondary voltage can be varied by just varying secondary number of turns.

As winding is common in both circuits, most of the energy is transferred by means of electrical conduction and a small part is transferred through induction.

The considerable disadvantages of an auto transformer are,

• any undesirable condition at primary will affect the equipment at secondary (as windings are not electrically isolated),
• due to low impedance of auto transformer, secondary short circuit currents are very high,
• harmonics generated in the connected equipment will be passed to the supply.

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Unity Power Factor AC–DC Power Converter

·          This article presents a power converter and its control circuit for high-frequency-fed ac to dc conversion.
·        Based on the resonant technique, the input current is shaped to be sinusoidal and is forced to follow the high-frequency sinusoidal input voltage so as to achieve unity power factor.

·        With the proper selection of the characteristic impedance of the resonant tank, the converter is able to perform the function of a buck, boost, or buck–boost converter.
·         The initial condition of the resonant tank is used to control the output voltage gain of the converter.

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CURRENT-FED PUSH–PULL CONVERTER TRIGGERING USING SOFT-SWITCHING

 A push–pull converter is suitable for low-voltage photovoltaic ac module systems, because the step-up ratio of the high-frequency transformer is high, and the number of primary-side switches is relatively small. 

PUSH PULL CONVERTER

However, the conventional push–pull converter does not have high efficiency because of high-switching losses due to hard switching and transformer losses (copper and iron losses) as a result of the high turn ratio of the transformer. In the proposed converter, primary-side switches are turned ON at the zero-voltage switching condition and turned OFF at the zero-current switching condition through parallel resonance between the secondary leakage inductance of the transformer and a resonant capacitor. The proposed push–pull converter decreases the switching loss using soft switching of the primary switches. In addition, the turn ratio of the transformer can be reduced by half using a voltage-doubler of secondary side. 

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ZETA CONVERTER

• A  non isolated power factor corrected (PFC) converter is being proposed to be used at the front end to improve the power quality of an SMPS for a PC. 
• The front end converter is able to reduce the 100 Hz ripple in its output that is being fed to the second stage isolated converter. 
• The performance of the front-end Zeta converter is evaluated in three different operating conditions to select the best operating condition for the proposed SMPS system.

 ZETA CONVERTER

• The zeta converter is a dc to dc converter .It can be operated at buck and boost modes.
• we can able to step down either step up of the output voltage.

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HPF CONVERTER WITH ZVS TRANSITION

• This article presents a single-phase high-power factor ac/dc converter with soft-switching characteristic. The boost converter performs the function of power-factor correction (PFC) to obtain high power factor and low current harmonics at the input line.
• The buck converter further regulates the dc-link voltage to provide a stable dc output voltage.

                        

HPF converter with ZVS transition

• Without using any active-clamp circuit or snubber circuit, the active switches of the proposed converter can achieve zero-voltage switching-on (ZVS) transition together with high power factor that satisfies the IEC 61000-3- 2 standards over a wide load range from 30% to 100% rated power.
• The steady-state analysis is developed and a design example is provided. A prototype circuit of 60 W was built and tested.
• Experimental results verify the feasibility of the proposed circuit with satisfactory performance

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IMPLEMENT DIMMING METHOD FOR HOT CATHODE FLUORESCENT LAMP USING A RESONANT INVERTER

• This article describes a dimming method for hotcathode fluorescent lamp (HCFL) using a resonant inverter operating at fixed switching frequency. 
• The proposed method is based on burst dimming and decreases the inverter output voltage during the burst-off period by changing the switching pattern of the inverter.

A DIMMING METHOD FOR HOT CATHODE FLUORESCENT LAMP USING A RESONANT INVERTER OPERATING 

•  Consequently, the lamp can be turned OFF, while the filaments of lamp are kept preheated without adding an inverter for preheating.
•  Once the lamp is turned OFF, N-times resonant mode (where N means a natural number) occurs because the characteristic of the resonant circuit (which depends on lamp impedance) changes drastically.
•  This mode keeps the root mean square of filament currents large enough to ensure long lamp life. Moreover, the inverter operates in zero-voltage-switching resonant mode during both the burst-on and burst-off periods. 
•  The proposed method thus contributes to achieving long lifetime, small size, and low cost of lighting system for HCFLs. 

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BrushLess DC MOTOR DRIVE WITH POWER FACTOR CORRECTION

• This article presents a power factor correction (PFC)-based bridgeless canonical switching cell (BL-CSC) converter-fedbrushless dc (BLDC) motor drive.
•  The proposed BL-CSC converter operating in a discontinuous inductor current mode is used to achieve a unity power factor at the ac mains using a single voltage sensor.
•  The speed of the BLDC motor is controlled by varying the dc bus voltage of the voltage source inverter (VSI) feeding the BLDC motor via a PFC converter.

BLDC MOTOR DRIVE WITH POWER FACTOR CORRECTION

•  Therefore, the BLDC motor is electronically commutated such that the VSI operates in fundamental frequency switching for reduced switching losses. 
• Moreover, the bridgeless configuration of the CSC converter offers low conduction losses due to partial elimination of diode bridge rectifier at the front end. 
• The proposed configuration shows a considerable increase in efficiency as compared with the conventional scheme.
•  The performance of the proposed drive is validated through experimental results obtained on a developed prototype. 
• Improved power quality is achieved at the ac mains for a wide range of control speeds and supply voltages.
•  The obtained power quality indices are within the acceptable limits of IEC 61000-3-2.

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INPUT-PARALLEL OUTPUT-SERIES DC/DC CONVERTER WITH COUPLED INDUCTORS

The primary windings of two coupled inductors are connected in parallel to share the input current and reduce the current ripple at the input. On the other hand,the proposed converter inherits the merits of interleaved series-connected output capacitors for high voltage gain, low output voltage ripple, and low switch voltage stress. Moreover, the secondary sides of two coupled inductors are connected in series to a regenerative capacitor by a diode for extending the voltage gain and balancing the primary-parallel currents. In addition, the active switches are turned on at zero current and the reverse recovery problem of diodes is alleviated by reasonable leakage inductances of the coupled inductors. Besides, the energy of leakage inductances can be recycled

         

DC/DC CONVERTER

DC-DC Converters:

 There are three basic types of dc-dc converter circuits, termed as buck, boost and buck-boost. In all of these circuits, a power device is used as a switch. This device earlier used was a thyristor, which is turned on by a pulse fed at its gate. In all these circuits, the thyristor is connected in series with load to a dc supply, or a positive (forward) voltage is applied between anode and cathode terminals.

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DC–DC CONVERTER INTEGRATING COUPLED-INDUCTOR AND DIODE CAPACITOR TECHNIQUES

• The high-voltage gainconverter is widely employed in many industry applications, such as photovoltaic systems, fuel cell systems, electric vehicles, and high-intensity discharge lamps. 
• This paper presents a novel single-switch high step-up nonisolated dc–dc converter integrating coupled inductor with extended voltage doubler cell and diode–capacitor techniques. 
• The proposed converter achieves extremely large voltage conversion ratio with appropriate duty cycle and reduction of voltage stress on the power devices.

High voltage gain DC DC converter

•  Moreover, the energy stored in leakage inductance of coupled inductor is efficiently recycled to the output, and the voltage doubler cell also operates as a regenerative clamping circuit, alleviating the problem of potential resonance between the leakage inductance and the junction capacitor of output diode. 
• These characteristics make it possible to design a compact circuit with high static gain and high efficiency for industry applications.

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Basics of Micro grids

Definition of microgrid

A microgrid is a local energy grid with control capability, which means it can disconnect from the traditional grid and operate autonomously.

Structure of microgrid

Working of microgrid

To understand how a microgrid works, you first have to understand how the grid works. The grid connects homes, businesses and other buildings to central power sources, which allow us to use appliances, heating/cooling systems and electronics. But this interconnectedness means that when part of the grid needs to be repaired, everyone is affected. This is where a microgrid can help. A microgrid generally operates while connected to the grid, but importantly, it can break off and operate on its own using local energy generation in times of crisis like storms or power outages, or for other reasons. A microgrid can be powered by distributed generators, batteries, and/or renewable resources like solar panels. Depending on how it’s fueled and how its requirements are managed, a microgrid might run indefinitely.

Way to connect microgrid with main grid

A microgrid connects to the grid at a point of common coupling that maintains voltage at the same level as the main grid unless there is some sort of problem on the grid or other reason to disconnect. A switch can separate the microgrid from the main grid automatically or manually, and it then functions as an island.

Main advantage of micro grid

A microgrid not only provides backup for the grid in case of emergencies, but can also be used to cut costs, or connect to a local resource that is too small or unreliable for traditional grid use. A microgrid allows communities to be more energy independent and, in some cases, more environmentally friendly.

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NEED OF HVDC THAN HVAC

HVDC - What and Why?

HVDC stands for high voltage direct current, a well-proven technology used to transmit electricity over long distances by overhead transmission lines or submarine cables

HVDC stands for high voltage direct current, a well-proven technology used to transmit electricity over long distances by overhead transmission lines or submarine cables. It is also used to interconnect separate power systems, where traditional alternating current (AC) connections cannot be used.

In an HVDC system, electric power is taken from one point in a three-phase AC network, converted to DC in a converter station, transmitted to the receiving point by an overhead line or cable and then converted back to AC in another converter station and injected into the receiving AC network. Typically, an HVDC transmission has a rated power of more than 100 MW and many are in the 1,000 – 3,000 MW range.

With an HVDC system, the power flow can be controlled rapidly and accurately in terms of both power level and direction. This possibility is often used to improve the performance and efficiency of the connected AC networks. There are three different categories of HVDC transmission projects:

- Point-to-point transmission

- Back-to-back stations

- Multi-terminal systems.

The first commercial HVDC scheme, based on mercury arc valves was commissioned in 1954. This was a link between the Swedish mainland and the island of Gotland in the Baltic sea. The power rating was 20 MW and the transmission voltage 100 kV There was a significant improvement in HVDC technology in 1970 when thyristor valves were introduced in place of the mercury arc valves. This reduced the size and complexity of HVDC converter stations substantially. The use of microcomputer control equipment in today’s projects has also contributed to HVDC’s current success as a powerful alternative to AC power transmission.

HVDC TRANSMISSION

WHY HVDC?

The reasons for selecting HVDC instead of AC for a specific project are often numerous and complex. The most common arguments in its favour are:

1. Lower investment cost

2. Long distance water crossing

3. Lower losses

4. Asynchronous interconnections

5. Controllability

6. Limited short-circuit currents

7. Environment.

In general, the different reasons for using HVDC fall into two main groups, namely: - HVDC is necessary or desirable from the technical point of view (that is controllability). - HVDC results in a lower total investment (including lower losses) and/or is environmentally superior.

In many cases, projects are justified by a combination of benefits from the two groups. Environmental aspects are also increasingly important and HVDC has the advantage of a lower environmental impact than AC since the transmission lines are much smaller and need less space for the same power capacity. One of the most important differences between HVDC and AC is the possibility to accurately control the active power transmitted on a HVDC line. This is in contrast to AC lines, where the power flow cannot be controlled in the same direct way. The controllability of the HVDC power is often used to improve the operating conditions of the AC networks where the converter stations are located.

Another important property of an HVDC transmission is that it allows the interconnection of asynchronous networks. 

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ADVANCED CASCADED MULTILEVEL INVERTER

• In this article, a new cascaded multilevel inverter is presented.
•  For the proposed inverter, two different algorithms to determine the magnitude of dc voltage sources are proposed. 
• Then, in order to generate maximum numbers of output voltage levels by using constant number of power switches and or dc voltage sources, several optimum structures of the proposed inverter are obtained.

•                    NEW CASCADED MULTILEVEL INVERTER WITH REDUCED NUMBER OF COMPONEN
• •  In comparison with the conventional cascaded multilevel inverters, the proposed inverter is able to generate high number of output voltage levels by using lower number of power electronic devices such as power switches, driver circuits, power diodes and dc voltage sources. 
  • In addition, the low amount of blocked voltage by switches is another advantage of the proposed inverter. 
  • The accuracy performance of the proposed inverter in generation the positive and negative voltage levels is verified through the experimental results on a 61- level inverter.
  
  
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MPPT technique for PV system under fast-varying solar irradiation

This article presents a simpler fast-converging MPPT technique, which excludes the extra control loop and intermittent disconnection. In the proposed algorithm, the relationship between the load line and the I–V curve is used with trigonometry rule to obtain the fast response. Results of the simulation and experiment using single ended primary-inductor converter showed that the response of the proposed algorithm is four times faster than the conventional incremental conductance algorithm during the load and solar Irradiation variation. Consequently, the proposed algorithm has higher efficiency.

MPPT technique for PV system under fast-varying solar irradiation 

The  frequently referred to as MPPT, is an electronic system that operates the Photovoltaic (PV) modules in a manner that allows the modules to produce all the power they are capable of. MPPT is not a mechanical tracking system

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