A NOVEL ON HYBRID WIND SOLAR ENERGY CONVERSION SYSTEM TO IMPROVE THE POWER QUALITY USING CASCADED H-BRIDGE MULTILEVEL INVERTER MEKALA MANIKUMAR [1] P.G SCHOLAR DAVULURI SRIKANTH [2] ASSISTANT PROFESSOR P.PURNA CHANDRA RAO [3] ASSOCIATE PROFESSOR & M.TECH (PH.D) [1,2,3] DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING [1,2,3] CHALAPATHI INSTITUTE OF TECHNOLOGY, MOTHADAKA, GUNTUR, A.P. ABSTRACT This thesis presents an improved cascaded H-Bridge multilevel inverter (CHBMLI) based grid connected hybrid wind-solar energy conversion system (HWSECS) with the mandate of power quality. The wind energy conversion system (WECS) and solar energy conversion system (SECS) are connected individually to an isolated dc-links of the CHBMLI through their respective DC/DC converters based maximum power point tracking (MPPT) system. The CHB topology when endorsed as PWM rectifier sustain with the capacitor unbalancing issues among the dc links feeding distinct dc loads and the same arise when piloted in regenerative operation with distinct sources popping uneven power into each cell. The proposed HWSECS system suffers the similar unbalance voltages as two distinct sources (WECS and SECS) are augmented among isolated dc-links. The author made efforts in exploiting the advantages of topology concurrently inscribed the solution to the hurdles during the system operation and control. The features of the proposed system and the control scheme impart maximum power extraction from RES and injection into grid along with other advantages. The simulation studies has been carried out in MATLAB/Simulink. I. INTRODUCTION The hybrid renewable energy sources (HRES) have been progressively researched and invented to satisfy the increasing energy demand, and gained broad attention in recent years as of their prosperity of being ample and non-pollutant nature. In diverse hybrid systems, two or more RES are joined simultaneously for enhancing the power supply reliability [1–4]. Among these different RES, wind and solar energy sources have been mostly and efficiently used together. Wind power is one such most prominent RES as it is easily available and collected by wind turbines with high power capacity. Solar power is another auspicious green energy source since it is most abundant and easily harnessed by using PV modules. Actually, wind and solar power complement each other since during the night time and cloudy days when solar power is less available but strong winds are mostly to occur whereas weak winds usually occur in sunny days [5– 7]. Hence, irrespective of varying environmental conditions a hybrid wind-solar energy conversion system (HWSECS) can deliver continuous output power supply than any other individual power generation systems. With the remarkable fast growth of power electronics devices and control techniques, the use of grid-connected HWSECS has been increased significantly [8]. For HWSECS, design and control of power electronic converters are prime interest. In this type of HRES, rectifiers, boost converters and inverters used for the efficient power conversion. Separate DC/DC converters for each power generating source or single DC/DC converter for whole system can be used [8–11]. In addition, the need of inventive and futuristic DC/AC converter configuration and their efficient control mechanism is required. Recently multilevel inverters (MLI) topologies have been become popular as they are more propitious; having higher voltage handling capability, nearly sinusoidal output voltage waveform with better harmonic spectra, good electromagnetic compatibility and lower voltage stress for the switches when compared to a basic 2-level inverter [12]. Various conventional symmetrical, asymmetrical and reduce device count MLI topologies along with control mechanism and modulation techniques were proposed for grid integration of RES in [9,12,13]. Some power quality problems like voltage variations, harmonic generation, flickers and unbalanced dc-link capacitor voltages are arises during working of HWSECS. Unwanted harmonics produced due to the presence of power converters. Due to the varying wind speed and solar irradiation, flicker or voltage variation occurs in output power supply. As a result, peak value of the DC currents in the DC capacitor links becomes different, which result in unbalanced dc-link capacitor voltages. This in turn leads to unequal voltage stress across the switching devices, making the use of DC/AC converters unproductive. So the
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A NOVEL ON HYBRID WIND SOLAR ENERGY CONVERSION SYSTEM
TO IMPROVE THE POWER QUALITY USING CASCADED H-BRIDGE
MULTILEVEL INVERTER
MEKALA MANIKUMAR
[1] P.G SCHOLAR
DAVULURI SRIKANTH[2]
ASSISTANT PROFESSOR
P.PURNA CHANDRA RAO[3]
ASSOCIATE PROFESSOR & M.TECH (PH.D)
[1,2,3]DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING
[1,2,3]CHALAPATHI INSTITUTE OF TECHNOLOGY, MOTHADAKA, GUNTUR, A.P.
ABSTRACT
This thesis presents an improved
cascaded H-Bridge multilevel inverter (CHBMLI)
based grid connected hybrid wind-solar energy
conversion system (HWSECS) with the mandate of
power quality. The wind energy conversion system
(WECS) and solar energy conversion system (SECS)
are connected individually to an isolated dc-links of
the CHBMLI through their respective DC/DC
converters based maximum power point tracking
(MPPT) system. The CHB topology when endorsed
as PWM rectifier sustain with the capacitor
unbalancing issues among the dc links feeding
distinct dc loads and the same arise when piloted in
regenerative operation with distinct sources popping
uneven power into each cell. The proposed HWSECS
system suffers the similar unbalance voltages as two
distinct sources (WECS and SECS) are augmented
among isolated dc-links. The author made efforts in
exploiting the advantages of topology concurrently
inscribed the solution to the hurdles during the
system operation and control. The features of the
proposed system and the control scheme impart
maximum power extraction from RES and injection
into grid along with other advantages. The simulation
studies has been carried out in MATLAB/Simulink.
I. INTRODUCTION
The hybrid renewable energy sources
(HRES) have been progressively researched and
invented to satisfy the increasing energy demand, and
gained broad attention in recent years as of their
prosperity of being ample and non-pollutant nature.
In diverse hybrid systems, two or more RES are
joined simultaneously for enhancing the power
supply reliability [1–4]. Among these different RES,
wind and solar energy sources have been mostly and
efficiently used together. Wind power is one such
most prominent RES as it is easily available and
collected by wind turbines with high power capacity.
Solar power is another auspicious green energy
source since it is most abundant and easily harnessed
by using PV modules. Actually, wind and solar
power complement each other since during the night
time and cloudy days when solar power is less
available but strong winds are mostly to occur
whereas weak winds usually occur in sunny days [5–
7]. Hence, irrespective of varying environmental
conditions a hybrid wind-solar energy conversion
system (HWSECS) can deliver continuous output
power supply than any other individual power
generation systems. With the remarkable fast growth
of power electronics devices and control techniques,
the use of grid-connected HWSECS has been
increased significantly [8].
For HWSECS, design and control of power
electronic converters are prime interest. In this type
of HRES, rectifiers, boost converters and inverters
used for the efficient power conversion. Separate
DC/DC converters for each power generating source
or single DC/DC converter for whole system can be
used [8–11]. In addition, the need of inventive and
futuristic DC/AC converter configuration and their
efficient control mechanism is required. Recently
multilevel inverters (MLI) topologies have been
become popular as they are more propitious; having
higher voltage handling capability, nearly sinusoidal
output voltage waveform with better harmonic
spectra, good electromagnetic compatibility and
lower voltage stress for the switches when compared
to a basic 2-level inverter [12]. Various conventional
symmetrical, asymmetrical and reduce device count
MLI topologies along with control mechanism and
modulation techniques were proposed for grid
integration of RES in [9,12,13]. Some power quality
problems like voltage variations, harmonic
generation, flickers and unbalanced dc-link capacitor
voltages are arises during working of HWSECS.
Unwanted harmonics produced due to the presence of
power converters. Due to the varying wind speed and
solar irradiation, flicker or voltage variation occurs in
output power supply. As a result, peak value of the
DC currents in the DC capacitor links becomes
different, which result in unbalanced dc-link
capacitor voltages. This in turn leads to unequal
voltage stress across the switching devices, making