DESIGN AND DEVELOPMENT OF CHARGE ... this is much less than higher speed generators, and certainly...

Volume 1, Issue 3, June 2016 E-ISSN: 2456-0006

International Journal of Science Technology

Management and Research Available online at: www.ijstmr.com

IJSTMR © 2016 | All Rights Reserved 25

DESIGN AND DEVELOPMENT OF CHARGE

CONTROLLER FOR 5kW WIND TURBINE

Priyanka Pawar M.E Scholar, Electrical Department,

S.N.D College of Engineering & Research

Center, Yeola, MH, India

[email protected]

Prof. Rakesh Kumar Jha Head of Electrical Engineering Department,

S.N.D College of Engineering & Research

Center, Yeola, MH, India

[email protected]

____________________________________________________________________________________________________

Abstract: This paper presents a design and development of charge controller for 5kw wind turbine. Energy sources are

broadly divided into to two main types renewable and non renewable. A Sustainable/renewable energy sources are wind,

water, solar energy which can be converted to electrical energy. Wind energy is converted to electrical energy with the

help of turbines, but must be controlled before feeding to any grid or storage devices. To control the power generated

from turbine to store or to feed any grid a system is needed which will stabilize the power generated. Charge controller is

a device which will control the power generated from the wind and fed it to storage device such as batteries. Charge

controller is the controller uses electronic means to regulate the incoming power and apply the correct charging voltage

to the installed battery. Proposed controller monitors the battery/system voltage and supply power for load consumption

and battery charging. As soon as batteries reaches to a fully charged state, the excess voltage from the generator will be

transferred to a dump load heating element via solid state device MOSFET. The voltage which is to be dumped can be

utilized form any purposes like to drive domestic loads, driving irrigation pumps or etc. Simulation results of proposed

charge controller is validated in MATLAB software to observe it’s actual behavior when it is installed.

Keywords: Charge controller, wind turbine system, permanent magnet synchronous generator (PMSG)

___________________________________________________________________________________________________

I. INTRODUCTION

With the present situation of increasing energy demand, rising energy prices, and reinforcement of countermeasures for global

warming and environment deterioration, sustainable energy sources have taken the spotlight. The establishment of a sustainable

energy future is one of the most pressing tasks of mankind for the 21st century. With the exhaustion of fossil fuel resources, the

energy economy has to change from a chemical to a physical base. Discussions on environmental problems in energy policy,

particularly global warming issues, have been given much attention these days. Scientific temperature observations, begun in the

19th century, have shown that the pace of temperature increase in the latter half of the 20th century has been faster. Currently, the

amount of fossil fuel origin carbon dioxide discharge has been increasing, with the corresponding increase in energy demand. Due

to this increase, it has been strongly claimed that the artificial greenhouse effect is the main cause. For these global warming

problems, the United Nations Framework Convention on Climate Change was issued in 1994, and Kyoto Protocol was issued in

February of 2005 [1]. The protocol called for efforts to reduce the amount of greenhouse type gas emissions from in advanced

countries from 2008 to 2012, ultimately aiming for 1990 levels. After the united nations organization (UNO’s) Conference of the

Parties (COP 15) negotiations in Copenhagen in December of 2009, one of the outcomes was that The Copenhagen Accord

recognizes the scientific view that an increase in global temperature below 2 degrees is required to stave off the worst effects of

climate change [1]. At this point the effort appears to be focused on CO2 reduction in society. Considering renewable energy

forms like wind power, their introduction has been promoted as a core program towards a low carbon social structure.

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Priyanka et. al., International Journal of Science Technology Management and Research

Volume 1 , Issue 3 , June 2016

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The electricity grid can provide households and communities with reliable, high quality, predictable and cheap

electricity, but this is far from the norm for the majority of the world’s population. Whilst being in the forefront of many

governments stated development objectives, widespread electrification is still the dream rather than the reality for most. Electricity

can bring many benefits; for those in the developed world it is taken for granted. In areas without the grid, some households use

motorcycle, car or lorry batteries to power radios or TV. This small amount of energy can disproportionately improve the standard

of living for the poorest. When there is enough to also provide lighting, it can improve children’s opportunities in later life by

enabling them to study after dark. To overcome all this problems wind energy is more environmentally benign than many

alternatives. Although energy is used in the wind generators manufacture, once in operation it does not consume fossil fuels and

does not emit greenhouse gases. Because the electricity produced and used for lighting displaces the use of kerosene, the

household environment improves. Wind generators produce some noise, but for machines designed to revolve at low rotational

speeds this is much less than higher speed generators, and certainly far quieter than a diesel generator set. Grid connection is the

preferred choice of most households, even if it appears unlikely to occur within the next ten years or so. If the grid is planned to

arrive in the short term (within 2 to 3 years), it may be more prudent for the household to wait, providing initial connection

charges and tariffs can be afforded. In the medium term, there may be a reluctance to invest in wind generators, especially if it is

perceived that they cannot provide grid-quality electricity (230v, 50Hz). This need not be the case, however, since the output from

the battery, charged by a wind generator, can be modified to run AC (alternating current similar to mains electricity) appliances. If

the grid does arrive in the future, these same appliances can be run from the mains, or the use of the wind generator continued.

Secondhand wind generators can find a ready market in areas where the grid has not arrived; this can reduce the risk of purchase.

This paper is mainly concern on the reducing cost of wind turbine energy system in long term. Maintaining the system

without proper controller may cause the battery frequently damage since overcharging and deep discharging repeatedly occurs. It

is not proficient to keep changing the battery, because it will lead the battery life to degrade. Proposed charge controller will be

functioning for the battery to have longer lifespan as it avoid the overcharge and deep discharge of the battery. Furthermore, by

using shunt charge controller, it can increase the performance of the wind turbine energy system without damage the wind turbine

since it connected to the dump load to avoid the rotation of the blades goes to high which may damage the wind turbine.

Following are the main objectives of the paper.

1. To build the charge controller for wind turbine of (3 phase, 5kW, 48v AC) output.

2. To find suitable type of battery for the controller.

II. WIND ENERGY SYSTEM

The wind energy system block diagram is shown in Figure 1 which incorporates a wind turbine for converting wind energy to the

electric energy, in the block diagram shown below there is three phase wind turbine generator which produces three phase output

[6]. From the wind turbine the AC three phase output is fed to the charge controller. Charger controller includes three phase full

wave rectifier that converts the AC output of the turbine to DC up to such level battery(48V) can be charged. Charge controller

also detects the maximum charged level of the battery and give an indication in the form of blinking LED. If the battery gets over

charged up to 20% i.e 57V then charging current and voltage needs to be diverted to prevent damage to the battery, therefore

charge controller diverts power from the battery to a Dump load. The stored power may be used directly by connecting to DC

loads like Blowers, DC motors etc. or by connecting the output of battery to inverter for converting DC output to AC and use AC

loads like TV, Radio etc. To store the energy generated by the wind, wind-turbine needs a charge controller to adjust the generator

voltage up to the battery voltage level. The alternating voltage generated is in the form of phase, and the battery voltage is

continuous, so that converter is necessary and hence charge controller also comprises of the converter circuitry (bridge rectifier) to

convert AC supply voltage from turbine to DC. A typical installation of wind charge controller is as shown in Figure 3.2 The




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system includes a wind turbine, Charge Controller, Divert Resistor, battery and an inverter. The inverter is additional and converts

the battery DC power into standard AC power, such that common mains powered appliances can be supplied [8].

Figure 1: Block diagram of wind energy system

III. PERMANENT MAGNET SYNCHRONOUS GENERATOR (PMSG) MODEL

MSGs are synchronous AC machines. The PMSG consist of 3-phase stator winding similar to the squirrel cage induction

generator (SCIG), while the rotor winding is replaced by the permanent magnets. The advantage of eliminating the rotor field

winding have reduced copper losses, Higher power density, lower rotor inertia and more . The demerits are loss of flexibility in

field flux control, possible demagnetization/saturation ff magnetic material and parameter variation over time. Depending on the

magnet placed on the rotor, PMSGs are divided into two categories which is. Surface permanently Magnet machines (SPM) and

interior permanent magnet machines (IPM) [10].

In SPM synchronous machines, the permanent magnets are mounted on the rotor Surface. The rotor has an iron core which can be

solid or made of Punched laminations with skewed poles to minimize cogging torque, and it’s simple design makes it easy to

build. This configuration is used for low speed operation. The permeability of magnetic material approximates air, producing an

effectively large air gap. Moreover, the smooth rotor surface design minimizes saliency in the rotor, contributing to a low

armature reaction effect due to low magnetization inductance [10].

In IPM synchronous machines, magnets are installed inside the rotor. The IPM rotor is difficult to fabricate, although the

robust design makes it most suitable for high speed applications. The unequal effective air gap distribution renders it as salient

pole machine, where the direct axis inductance is less than quadrature axis inductance (Ld < Lq). Permanent magnet synchronous

machines, magnets are placed on the rotor as alternate N and S poles. These magnets cause the development of magnetic flux in

the air Gap. When the stator windings are excited, they develop their own magnetic flux, and the close interaction between the

rotor and stator magnetic fields produces electromagnetic torque in the rotor [4]. Figure 2 (a) &(b) shows a simplified cross-

section view of 3-phase, 2-pole PMSG and IPMSG with symmetrical stator windings, displaced from each other at a 120 electrical

angle. The relative motion between rotor and stator induces sinusoidal MMF waves on the magnet axes of the respective phases.

The phase difference between rotor magnetic flux and the the magnetic axis of stator phase-a winding is known as rotor position

angle (θr) [10]. The rate of change of rotor position angle further calculates the angular rotor speed (ωr)




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Figure 2: Cross sectional view of rotor design of a) SPMSG and b) IPMSG

IV. METHODOLOGY

Figure 3:- MATLAB simulation of wind energy system and charge controller

Charge controller is simulated using MATLAB/Simulink, where the entire replica of the proposed system is simulated with the

48v lead-acid battery and permanent magnet wind turbine of 5kW under various condition, i.e. at a fixed speed (Constant voltage

and current) and variable speed (variable voltage and current).Battery used in the simulation is the led-acid battery of 48v and

200Ah. State of charge (SOC) of battery and voltage is continuously measured on the scope and displayed on the display. The

MOSFET is used as the switch for avoiding the battery to get overcharged above 20% of its fully charged voltage level. And when

battery reaches to the fully charged level, then the supply to the battery is shifted from battery to dump load avoiding battery to get

further charged. Trigger control block and battery discharge block are created to detect the triggering point (voltage) of the dump

load and discharge block is created to discharge the battery after charging. Complete simulation diagram is shown in Figure 3. In




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this simulation of 200Ah battery is used for charging, the simulation takes 2hr i.e 7200sec to charge battery completely at constant

wind speed.

The generator block is the three phase permanent magnet synchronous generator with output voltage of 48v peak to peak,

mechanical input to this generator is in the form of torque, which is fed from a wind turbine and electromagnetic torque Te, rotor

speed !m and current in all the phases is taken on the scope for monitoring. In simulation block of wind turbine the pitch angle is

kept constant and the base speed of the wind turbine is kept 9m/s as per the specifications of the wind turbine. The wind turbine is

connected to a manual switch for selecting the mode of operation at constant speed and variable speed, and wind speed is

continuously monitored on scope [7]. A three phase inductor block is putted in series with the three phase output line of the

generator to minimize the impedance of the line. Also, three phase small RLC load kept in the simulation to avoid the MATLAB

error it acts as a leakage load. V − I measurement block is there to measure the current and voltage of the wind energy system.

The main purpose behind designing of the charge controller is not allowing battery to get over charge above the

particular limit. To increase the battery life, it is an important task for any charger designer that the battery should get

disconnected from the supply automatically when it will reach to that fully charged triggering level. Now, rectification of AC to

suitable DC level is achieved for battery charging, and according to the nature of the Lead-acid battery it charges with 48v DC

voltage. But the objective of project is to disconnect the battery automatically when it reaches to the voltage level of 57.6v, which

is 20% more than its rated charged level for avoiding the battery damage by over charging.

Two testing circuits are developed for the testing and to observe charge controller operation. As observed in MATLAB

simulation provision of both variable speed and fixed speed operation of turbine is provided. For testing of charge controller’s

working also, there are two different circuits developed one to make it operate at constant frequency and another is for variable.

Testing unit consists of three phase Variac for increasing and decreasing the voltage output of the transformer. Current

transformers are clamped across each line to measure the current in them and voltmeter across each phase for measuring the

voltage, and the output of transformer is fed to charge controller for testing it at constant frequency.

V. RESULTS

Input and output of generator

Figure 4:- Variable wind speed vs time




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Battery charging

Figure 5:- State of charge of battery in percentage vs time

Figure 6:- Battery voltage while charging vs time

CONCLUSION

Hybrid wind-solar charge controller can be made to use the benefits of both the energies an help to improve the

efficiency of the renewable energy powered system. Low voltage disconnect circuitry can be introduced in this charge

controller to auto disconnect the load connected to battery when the battery voltage goes down beyond an specific point.

The charge controller in the proposed circuit is capable of detecting the full charged level of the battery by giving an

indication in form of a glowing green LED and allows the battery to charge further up to 20% i.e. 57v. When battery

voltage reaches to the predefined value of 57v the MOSFET bank switches the charging voltage form battery to the dump

load, by prevent the battery to charge further up to danger level and also prevents the batteries life to degrade by over

charging. In future expansion instead of dumping the generated extra power, that power can be used for charging another

set of batteries or for operating motors for many purposes, boiling water and for the heating particular areas.




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DESIGN AND DEVELOPMENT OF CHARGE ... this is much less than higher speed generators, and certainly...

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