Isolated operation of pmsg based variable speed wind turbine generating system with management of hy

International Journal of Research in Advanced Technology - IJORAT Vol. 2, Issue 2, FEBRUARY 2016

All Rights Reserved © 2016 IJORAT 1

ISOLATED OPERATION OF PMSG

BASED VARIABLE SPEED WIND

TURBINE GENERATING SYSTEM WITH

MANAGEMENT OF HYBRID ENERGY

STORAGE S.Nirosha Devi

1, Liza.V

2, S.Usha Rani

3

123Student, Dept of EEE, FRANCIS XAVIER ENGINEERING COLLEGE, Tamilnadu, India

Abstract: This project will demonstrate the standalone operation of a PMSG with a hybrid energy storage

system consisting of a battery storage and supercapacitor where both are connected to the DC bus of the

remote area power supply system. An energy management algorithm is proposed for the hybrid energy

storage with a view to improve the performance of the battery storage. The supercapacitor absorbs the ripple

or high frequency power component of demand generation mismatch while leaving the steady component for

battery storage. The proposed control algorithm is able to manage power balance in remote area power

supply system. The simulation result was demonstrated to determining the following objectives: a) robust

voltage and frequency regulation, b) effective management of the hybrid storage system.

Keywords: PMSG, Battery, Supercapacitor, DC link, Voltage source inverter.

I. INTRODUCTION

The renewable energy sources provide

sustainable energy services. It is becoming clear that

future growth in the energy sector will be primarily in

the new regime of renewable energy. The major

components a typical wind energy conversion system

includes a wind turbine, generator, interconnection

apparatus and control systems.

Wind turbines can be classified into the

vertical axis type and the horizontal axis type. Most

modern wind turbines use a horizontal axis

configuration with two or three blades, operating

either down-wind or up-wind. A wind turbine can be

designed for a constant speed or variable speed

operation.

Variable speed wind turbines can produce

8% to 15% more energy output as compared to their

constant speed counterparts, however, they

necessitate power electronic converters to provide a

fixed frequency and fixed voltage power to their

loads. Most turbine manufacturers have opted for

reduction gears between the low speed turbine rotor

and the high speed three-phase generators. Direct

drive configuration, where a generator is coupled to

the rotor of a wind turbine directly, offers high

reliability, low maintenance, and possibly low cost

for certain turbines.

The renewable energy sources are one of the

biggest concerns of our times. High prices of oil and

global warming make the fossil fuels less and less

attractive solutions. Wind power is a very important

renewable energy source. It is free and not polluter

unlike the traditional fossil energy sources. It obtains

clean energy from the kinetic energy of the wind by

means of the wind turbine. The wind turbine

transforms the kinetic wind energy into mechanical

energy through the drive train and then into electrical

energy by means of the generator.

There are different wind turbine

configurations. They can have or not gearbox, the

generator can be synchronous or asynchronous.

Different modes of operation can be used in wind

turbine.



Normally an asynchronous generator is used

and it is directly connected to the grid. For the

variable-speed operation, maximum efficiency is

obtained the system is controlled to maximize the

power extracted from the wind. Among all these

configurations, the trend is to use variable-speed

wind turbines because they offer more efficiency and

control flexibility which is becoming very important

to comply with the grid requirements.

In order to operate with low speeds, a high

number of poles is used in PMSG wind turbines.

Instead of electrical DC excitation the magnetic rotor

field is provided by permanent magnets. Due to the

equal distribution of the surface mounted magnets

and a permeability of the magnet material μm

approximately as big as the air gap permeability the

reactance in d- and q-axis differ by only a few

percent , so that surface mounted PMSGs can be

considered as round rotor machines (xd = xq).

Because the multipole PMSG is a converter

connected low speed application (in contrast to high

dynamic drives) no damper winding is necessary.

The use of permanent magnets eliminates the DC

excitation system, which means a reduction of losses

(high field ampere turns in multipole generators) and

the omission of slip rings and thus maintenance

requirements.

Several manufacturers have opted for the

direct drive configuration in the recent turbine

designs. At the present time and in the near future,

generators for wind turbines will be synchronous

generators, permanent magnet synchronous

generators, and induction generators, including the

squirrel cage type and wound rotor type.

For small to medium power wind turbines,

permanent magnet generators and squirrel cage

induction generators are often used because of their

reliability and cost advantages. Induction generators,

permanent magnet synchronous generators and

wound field synchronous generators are currently

used in various high power wind turbines.

Interconnection apparatuses are devices to achieve

power control, soft start and interconnection

functions. Very often power electronic converters are

used as such devices.

Most modern turbine inverters are forced

commutated PWM inverters to provide a fixed

voltage and fixed frequency output with a high power

quality. Both voltage source voltage controlled

inverters and voltage source current controlled

inverters have been applied in wind turbines.

All renewable energy (except tidal and geothermal

power), ultimately comes from the sun. The earth

receives 1.74 x 1017

watts of power (per hour) from

the sun. About one or 2 percent of this energy is

converted to wind energy (which is about 50-100

times more than the energy converted to biomass by

all plants on earth. Differential heating of the earth’s

surface and atmosphere induces vertical and

horizontal air currents that are affected by the earth’s

rotation and contours of the land wind. e.g.: Land Sea

Breeze Cycle. Winds are influenced by the ground

surface at altitudes up to 100 meters. Wind is slowed

by the surface roughness and obstacles. When

dealing with wind energy, we are concerned with

surface winds. wind turbine obtains its power input

by converting the force of the wind into torque

(turning force) acting on the rotor blades. The amount

of energy which the wind transfers to the rotor

depends on the density of the air, the rotor area, and

the wind speed. A typical 600 kW wind turbine has a

rotor diameter of 43-44 meters, i.e. a rotor area of

some 1,500 square meters. The rotor area determines

how much energy a wind turbine is able to harvest

from the wind. Since the rotor area increases with the

square of the rotor diameter.

II. PROPOSED SYSTEM

A. CIRCUIT DIAGRAM

Fig 1 Circuit diagram of proposed system

The PMSG performs as the main source of energy

and is interfaced with an uncontrolled rectifier-

inverter arrangement before connecting to the mains

load. In this regard, control is developed for the Line

Side Converter (LSC) and DC/DC converter.



B. BOOST CONVERTER

A boost converter (step-up converter) is

a power converter with an output DC voltage greater

than its input DC voltage. It is a class of switching-

mode power supply (SMPS)containing at least

two semiconductor switches (a diode and a transistor)

and at least one energy storage element. Filters made

of capacitors (sometimes in combination

with inductors) are normally added to the output of

the converter to reduce output voltage ripple.

Fig 2 schematic of boost converter

The key principle that drives the boost

converter is the tendency of an inductor to resist

changes in current. When being charged it acts as a

load and absorbs energy (somewhat like a resistor);

when being discharged it acts as an energy source

(somewhat like a battery). The voltage it produces

during the discharge phase is related to the rate of

change of current, and not to the original charging

voltage, thus allowing different input and output

voltages.

C. BUCK-BOOST CONVERTER

Two different topologies are called buck–

boost converter. Both of them can produce an output

voltage much larger (in absolute magnitude) than the

input voltage. Both of them can produce a wide range

of output voltage from that maximum output voltage

to almost zero.

The inverting topology – The output voltage is of the

opposite polarity as the input.

A buck (step-down) converter followed by

a boost (step-up) converter – The output voltage is of

the same polarity as the input, and can be lower or

higher than the input. Such a non-inverting buck-

boost converter may use a single inductor that is used

as both the buck inductor and the boost inductor.

D. THE INVERTING TOPOLOGY

Figure 3 schematic of a buck–boost converter

The buck–boost converter is a type of DC-

to-DC converter that has an output voltage magnitude

that is either greater than or less than the input

voltage magnitude. It is a switched-mode power

supply with a similar circuit topology to the boost

converter and the buck converter.

The output voltage is adjustable based on

the duty of the switching transistor. One possible

drawback of this converter is that the switch does not

have a terminal at ground; this complicates the

driving circuitry.

Also, the polarity of the output voltage is

opposite the input voltage. Neither drawback is of

any consequence if the power supply is isolated from

the load circuit (if, for example, the supply is a

battery) as the supply and diode polarity can simply

be reversed. The switch can be on either the ground

side or the supply side.

Operating principle

The basic principle of the buck–boost

converter is fairly simple.

While in the On-state, the input voltage

source is directly connected to the inductor (L). This

results in accumulating energy in L. In this stage, the

capacitor supplies energy to the output load.

While in the Off-state, the inductor is

connected to the output load and capacitor, so energy

is transferred from L to C and R. Compared to

the buck and boost converters, the characteristics of

the buck–boost converter are mainly Polarity of the

output voltage is opposite to that of the input, the

output voltage can vary continuously from 0 to

(for an ideal converter). The output voltage ranges

for a buck and a boost converter are respectively 0

to and to .

http://en.wikipedia.org/wiki/Power_converter

http://en.wikipedia.org/wiki/Switched-mode_power_supply


http://en.wikipedia.org/wiki/Semiconductor

http://en.wikipedia.org/wiki/Diode

http://en.wikipedia.org/wiki/Transistor

http://en.wikipedia.org/wiki/Energy

http://en.wikipedia.org/wiki/Capacitor

http://en.wikipedia.org/wiki/Inductor

http://en.wikipedia.org/wiki/Inductor

http://en.wikipedia.org/wiki/Buck_converter

http://en.wikipedia.org/wiki/Boost_converter

http://en.wikipedia.org/wiki/DC-to-DC_converter

http://en.wikipedia.org/wiki/DC-to-DC_converter











E. LINE SIDE CONVERTER

The LSC is modeled as a voltage controlled

voltage source inverter. The control objective of the

LSC is to regulate the magnitude and frequency of

the load side voltage. In this regard vector control has

been employed to develop the control associated with

the LSC.

F. BATTERY CHARACTERISTICS

Nominal Voltage (V)

The nominal voltage (Vnom) of the battery

(volts). The nominal voltage represents the end of the

linear zone of the discharge characteristics.

Rated Capacity (Ah)

The rated capacity (Qrated) of the battery in

ampere-hour. The rated capacity is the minimum

effective capacity of the battery.

Initial State-Of-Charge (%)

The initial State-Of-Charge (SOC) of the

battery. 100% indicates a fully charged battery and

0% indicates an empty battery. This parameter is

used as an initial condition for the simulation and

does not affect the discharge curve (when the option

Plot Discharge Characteristics is used).

Use parameters based on Battery type and

nominal values

Load the corresponding parameters in the

entries of the dialog box, depending on the selected

Battery type, the Nominal Voltage and the Rated

Capacity. When a preset model is used, the detailed

parameters cannot be modified. If you want to

modify the discharge curve, select the desired battery

type to load the default parameters, and then uncheck

the Use parameters based on Battery type and

nominal values checkbox to access the detailed

parameters.

Maximum Capacity (Ah)

The maximum theoretical capacity (Q),

when a discontinuity occurs in the battery voltage.

This value is generally equal to 105% of the rated

capacity. Fully charged Voltage (V) The fully

charged voltage (Vfull), for a given discharge

current. Note that the fully charged voltage is not the

no-load voltage.

Nominal Discharge Current (A)

The nominal discharge current, for which

the discharge curve has been measured. For example,

a typical discharge current for a 1.5 Ah NiMH battery

is 20% of the rated capacity: (0.2 * 1.5 Ah / 1h =

0.3A).

Internal Resistance

The internal resistance of the battery (ohms).

When a preset model is used, a generic value is

loaded, corresponding to 1% of the nominal power

(nominal voltage * rated capacity of the battery). The

resistance is supposed to be constant during the

charge and the discharge cycles and does not vary

with the amplitude of the current.

Capacity (Ah) @ Nominal Voltage

The capacity (Qnom) extracted from the

battery until the voltage drops under the nominal

voltage. This value should be between Qexp and

Qmax.

Exponential zone [Voltage (V), Capacity (Ah)]

The voltage (Vexp) and the capacity (Qexp)

corresponding to the end of the exponential zone. The

voltage should be between Vnom and Vfull. The

capacity should be between 0 and Qnom.

G. SUPERCAPACITOR

The capacitance of a capacitor is closely

related to the surface area of the electrodes .A super

capacitor is a component which has relatively high

specific power ability in comparison to batteries

much like a capacitor, while it has much higher

specific energy than a conventional capacitor, more

like a battery.

The electric chemical super capacitor is

constructed with a carbonized porous material as one

electrode, which has a large surface area due to the

cavities. The other electrode is a liquid chemical

conductor which is electrically isolated through an

isolating layer between the electrodes.

The thickness of the dielectric layer equals

the distance between the electrodes. In order to have

high capacitance, the isolator is very thin, usually in

order of tenths of nm. Due to these factors, high

capacitance is accomplished. The maximum voltage

difference between the electrodes is related to the

dielectric breakdown of the isolator, which in turn is

related to its thickness and material.



H. SIMULATION OF PROPOSED

SYSTEM The energy management algorithm applied

for both storage options have been developed to

satisfy the above-stated objectives. The energy

management algorithm for the battery storage and

super capacitor is depicted. The input signal to the

energy management algorithm is selected as the

demand-generation mismatch with a view to achieve

the first objective. To realize the second objective,

the demand-generation mismatch is estimated. The

application of energy storage to a standalone power

system can be used to fulfill one or more of the

following requirements: (1) to improve the efficiency

of the entire RAPS system, (2) to reduce the primary

fuel (e.g., diesel) usage by energy conversion, and (3)

to provide better security of energy supply. The

justification behind the integration of energy storage

into a wind energy application is based on the factors

which include total wind turbine inertia, low voltage

ride through capability, power quality issues, etc...For

a wind turbine based RAPS system, an ideal ESS

should be able to provide both high energy and power

capacity to handle situations such as wind gust or

sudden load variations which may exist for a few

seconds or even longer.

Fig 4 Simulink model of proposed system

. Permanent Magnet Synchronous Generator

(PMSG) offers many advantages but not limited to

self excitation capability which allows operation at a

high power factor and improved efficiency, gear-less

transmission, high reliability, good control

performance, Maximum Power Point Tracking

(MPPT) capability, low noise emissions, etc.. The

performance of the components of a hybrid RAPS

system is investigated under fluctuating wind and

variable load conditions. The PMSG performs as the

main source of energy while the hybrid energy

storage together with the dump load perform as

auxiliary system components to maintain the active

power balance of the RAPS system and to extract the

maximum power from wind.

An isolated operation of a PMSG with a

battery storage system is only covers a RAPS system

consisting of PMSG and battery storage. A multilevel

energy storage consisting of flow battery storage and

a super capacitor is explained. Different control

strategies proposed for the battery-super capacitor

hybrid energy storage system. It only examines the

different control strategies that could be applied to a

hybrid energy storage system. In an optimal energy

management scheme for battery-super capacitor

hybrid energy storage. In order to obtain the optimal

solution, have formulated the problem as an

optimization problem for minimization of the

fluctuation of the current flowing in and out of the

battery and the energy loss seen by the super

capacitor.

However, optimization is generally

application-oriented and the optimized parameters for

one system may not be suitable for another. a power

sharing strategy is formulated for battery energy

storage and super capacitor based on the demand-

generation variations of the RAPS system.

Fig 5 waveform for supercapacitor voltage

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.420

30

40

50

60

70

80

Time (sec)

vol (v)

<Voltage V>



This figure shows the output voltage of

supercapacitor during under generation condition.

Fig 6 waveform for supercapacitor current

This fig shows output current of the

supercapacitor during low or no generation

Fig 7 waveform for supercapacitor power

This figure represents the output for

supercapacitor during under generation condition

where the supercapacitor delivers the power to the

load.

Fig 8 waveform for battery current

This fig shows the output of the battery current is

delivered to the load.

Fig 9 waveform for soc of supercapacitor

Fig 9 shows the state of charging level of the

supercapacitor during over generation condition.

Fig 10 waveform for frequency regulation

This figure represents the output for

frequency regulation at load side. The operating

frequency of the system is regulated with in rated

value.

Fig 11 waveform for load voltage

This figure shows the output for load

voltage during both over generation and under

generation condition. Here we can achieve the three

phase 400V supply.

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4-3

-2.5

-2

-1.5

-1

-0.5

0

0.5x 10

4

Time (sec)

current (A

)<Current I>

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4-2.5

-2

-1.5

-1

-0.5

0

0.5x 10

6

Time (sec)

pow

er

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4-2000

-1500

-1000

-500

0

500

Time(sec)

current(A

)

<Current (A)>

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.430

40

50

60

70

80

90

100

110

Time (sec)

voltage (v)

<SOC %>

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.450

50.005

50.01

50.015

50.02

50.025

50.03

50.035

Time (sec)

freq (

Hz)

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4-400

-300

-200

-100

0

100

200

300

400

Time (sec)

voltage (v)

Vload



Fig 12 waveform for load current

Fig 12 represents the output for load current.

Here we can get the 15A current.

Fig 13 waveform for load power

This figure shows the load power during

both over generation and under generation condition.

Also, the sudden wind speed changes cause rapid

variations of the wind power output.

CONCLUSION

The proposed standalone operation of

PMSG with hybrid energy storage system includes a

wind turbine which takes up the wind speed. The

mechanical output of the wind turbine is then

transmitted to the PMSG. The AC output of the

generator is then converted to DC by means of a

rectifier. The rectified output of the generator is then

boosted up by a boost converter. The output of boost

converter is fed to the inverter to make it suitable for

further connection of system to load. The hybrid

energy storage system is connected between rectifier

and inverter for improving the power balance of the

entire remote area power supply system. The energy

management algorithm is proposed for hybrid energy

storage system with a view to improve the

performance of the battery.The main focus of this

paper is on proposing an effective management of

hybrid energy storage system and to obtain the robust

voltage and frequency regulation.

Further work could be accomplished by

means of implementing a storage system to ensure

constantpower output to the load.

ACKNOWLEDGMENT

First of all we would like to thank the

almighty for giving me sound health throughout my

paper work. This research was supported/partially

supported by our college. We thank our staffs from

our department who provided insight and expertise

that greatly assisted the research, although they may

not agree with all of the interpretations/conclusions

of this paper.

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0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4-15

-10

-5

0

5

10

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Time (sec)

current (A

)

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Time (sec)

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Isolated operation of pmsg based variable speed wind turbine generating system with management of hy

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Transcript of Isolated operation of pmsg based variable speed wind turbine generating system with management of hy