FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
As amended by the Patents (Amendment) Act, 2005
AND
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2006
COMPLETE SPECIFICATION
(See section 10 and rule 13)
TITLE OF THE INVENTION
A system with input controlled CLC filter based buck converter for solar
power applications
APPLICANT(S)
Crompton Greaves Limited, CG House, Dr. Annie Besant Road, Worli, Mumbai -400030, Maharashtra, India, an Indian Company
INVENTOR(S):
Wachasundar Shripad and Sharma Shivkant; both of Crompton Greaves Limited, Global R&D, Electronic Design Centre (EDC), Aryabatta Building, Kanjur Marg (East), Mumbai - 400042, Maharashtra, India; both Indian Nationals.
PREAMBLE TO THE DESCRIPTION;
The following specification particularly describes the nature of this invention and the manner in which it is to be performed:

FIELD OF THE INVENTION:
This invention relates to the field of electronics and electrical engineering and signal processing engineering.
Particularly, this invention relates to a system with an input controlled CLC filter based buck converter for solar power applications.
BACKGROUND OF THE INVENTION:
There is a constant endeavor to move from fossil fuel based energy sources to natural power based energy sources. Solar energy is one of the forms of natural power based energy sources which is abundantly being harnessed, today. Since sunlight or solar power is available only for a portion of a day, one of the crucial factors in harnessing this resource lies in harnessing it efficiently. Photovoltaic panels are largely used for harnessing solar power. The process of harnessing also involves the steps of converting the accumulated heat source in to usable power such as Alternating Current or Direct Current. These steps of conversion need to be accurate enough so that a smooth power wave form for industrial and home use is available to a user.
In the electrical components associated with the photovoltaic panel for harnessing electrical energy, converters are common electric apparatuses that are used for converting electricity from one form to another. Converters are used for raising or lowering voltage or current levels to adapt the voltage of a source to the voltage of the load.
Converters are also used in connection with photovoltaic (PV) panels for supplying power available from the panels. It is also necessary to extract maximum power from PV panels as per requirement of load. A DC-DC converter is used to perform the impedance conversion required to match the solar panel impedance with the load impedance, allowing the extraction of maximum power from the solar panel. Most commonly used DC-DC converter is buck converter.

The buck converter is the most widely used DC-DC converter topology in power management and microprocessor voltage-regulator (VRM) applications. Those applications require fast load and line transient responses and high efficiency over a wide load current range. They can convert a voltage source into a lower regulated voltage. The name "Buck Converter" presumably evolves from the fact that the input voltage is bucked/chopped or attenuated, in amplitude and a lower amplitude voltage appears at the output. A buck converter, or step-down voltage regulator, provides non-isolated, switch-mode DC-DC conversion with the advantages of simplicity and low cost. An input filter (C filter or LC filter) is required in order to reduce a high frequency input pulse current generated by the switching action and to stabilize the maximum power point tracking (MPPT). However, an input filter causes instability if not properly designed. Therefore, it is necessary to analyze the source of the instability and to look for methods of eliminating the instability.
PRIOR ART:
The prior art involves bulk electrolytic capacitors having less life and result in input current and voltage ripples.
US20120007576 discloses the converter circuit for use in current-fed semi-quadratic buck-boost converter. The circuit has a capacitor connected between one of input terminals and a node. A set of semiconductor components is connected in series in parallel with a series connection of another set of semiconductor components. An end of an inductive component is connected to another node formed between the former set of semiconductor components. Another end of the inductive component is connected to an output terminal. The latter set of semiconductor components is provided to control a voltage between the input terminals. The topology of the converter can be used to extract the maximum power from a power source, such as a photovoltaic panel, for example. The topology can be used for supplying voltage to a DC bus or with back end inverter to an alternating voltage grid.
US20100295502 discloses the control system for DC-DC power converter having an inductor. The control system has a low pass filter electrically coupled to an inductor for producing a source referenced voltage proportional to the current flowing through the inductor. A controller

is coupled to the low pass filter. The controller computes the current through the inductive component using the source referenced voltage, and controls the power converter using calculated current. The disclosed methods and systems may allow improvements to power converters in many different applications. One application of particular interest is power conversion in solar electric systems. A power converter is connected between a photovoltaic array and a battery. Using any of several conventional techniques generally known as Maximum Power Point Tracking (MPPT), the power converter is controlled to adjust the operating voltage of the photovoltaic array to maximize the power delivered to the battery. The desired function may include regulating the output voltage, output current, input voltage, etc., or maximizing the power either drawn from the input or delivered to the output, charging a battery, or any other function that may be required of the power converter.
US5504418 utilizes a coupled-inductor boost switching DC to DC converter topology to provide full shunt voltage limiting for a spacecraft. Unlike Ahrens, this implementation does not require a tapped solar panel array nor separate diodes and wiring at the limiter, and produces very low levels of conducted and radiated electromagnetic interference. The bus voltage limiter (BVL) includes a pulse width modulator which controls the duty cycle of a single power switch from 0% to 100% to maintain a substantially regulated bus voltage and provide a variable load current that responds to changes in payload demand. A coupled inductor type boost DC to DC converter includes a pair of main windings which cooperate with the duty cycle modulated power switch to provide the regulated bus voltage. An auxiliary winding of the coupled inductor provides input ripple current cancellation in conjunction with a second inductor and a DC blocking capacitor to reduce electromagnetic interference. A conventional current sense circuit would provide a transformer having one winding in series with the power switch to sense the current from the solar array. The sensed current produces a unidirectional voltage across a second winding. A rectifier rectifies the unidirectional voltage and produces a current sense signal. In order to accurately sense the solar array current, the coupled inductor's ferrite core must be reset between each cycle. Otherwise the core will become saturated which creates an offset in the current sense signal that causes the bus voltage limiter (BVL) to be in shunting mode all the time. At nominal duty cycles, the ferrite core has enough time to reset. However, as the duty cycle approaches 100%, as it does when the load current drops to zero, the core does not have enough time to reset and will eventually saturate from which it cannot recover. The disadvantage of this configuration

is that the transitions in the payload current as the bus voltage limiters turn on and off to meet demand are not smooth.
US2012139471 discloses a buck converter along with maximum power point tracking for a photovoltaic module. However, it does not disclose use of a CLC input filter.
US2010264869 discloses a buck converter along with maximum power point tracking for a photovoltaic module. However, it does not disclose use of a CLC input filter.
US2009296434 discloses a buck converter along with a boost converter. This boost converter may be different than a CLC converter which is proposed in this invention.
US2013169051 discloses a buck converter along with a boost converter. The boost converter is merely a CL filter and not a CLC filter as proposed in this invention.
EP2525483 discloses a buck converter along with a boost converter. The filter is merely an L filter or an L-C filter and not a CLC filter as proposed in this invention.
However, none of these provide a ripple free input to a buck converter. Also, it is difficult to track the maximum power point tracking point across a V-I characteristic curve of photovoltaic panel due to its rapid movement across a greater bandwidth. This bandwidth needs to be reduced in order to reduce the time required to track.
OBJECTS OF THE INVENTION:
An object of the invention is to provide controlled input to a buck converter, which controller input comprises relatively reduced ripple.
Another object of the invention is to reduce the bandwidth for movement of maximum power point tracking point across a V-I characteristic curve of photovoltaic panel.

Yet another object of the invention is to provide a deferred corrected input to a buck converter for reducing reduce the bandwidth for movement of maximum power point tracking point across a V-I characteristic curve of photovoltaic panel.
Still yet another object of the invention is to provide higher tracking efficiency in order to track movement of maximum power point tracking point across a V-I characteristic curve of photovoltaic panel.
SUMMARY OF THE INVENTION:
According to this invention, there is provided a system with input controlled CLC filter based buck converter for solar power applications, said system comprises:
a. at least a buck converter adapted to be coupled with a power source in order to transfers
packets of energy;
b. at least a CLC filter adapted to receive input voltage and input current from said power
source and to provide output voltage and output current to said buck converter; and
c. at least a controller adapted to work in at least three states of operation for controlling
said system in order to enable said system to achieve higher tracking efficiency for
maximum power point tracking.
Typically, said power source is a photovoltaic panel.
Typically, said buck converter comprises a series connection of at least a buck inductive component, at least a diode, and at least a buck capacitive component.
Typically, said buck converter comprises a power switch, a diode, and a buck inductive component and being accompanied by an output filter capacitive component and input filter.
Typically, said CLC filter comprises at least a first capacitive component connected between first and second input terminals, at least a second capacitive component in parallel to said first capacitive component, and at least an inductive component in series between said first capacitive component and said second capacitive component.

Typically, said capacitor is of relatively lower value and of metal film type.
Typically, said at least a controller is adapted to work in at least three states of the controller,
said at least three states being:
i) voltage of first capacitive component;
ii) current of inductive component; and
iii) voltage of second capacitive component.
Typically, said at least a controller comprises: I. at least a voltage comparator where voltage of first capacitive component is compared with a reference voltage, with compared output being fed to a first capacitive component of said CLC filter; II. at least a current comparator where current of first inductive component is compared with a reference current, with compared output being fed to a second capacitive component of said CLC filter;
III. at least an inward current transfer function block whose input is received from said second capacitive component and whose output is given to an outward current transfer function block and to an inward voltage transfer function block;
IV. at least an inward voltage transfer function block adapted to receive input from said at least an inward current transfer function block and whose output is given to an outward voltage transfer function block;
V. at least an outward current transfer function block as feedback; and VI. at least an inward voltage transfer function block as feedback.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
The invention will now be described in relation to the accompanying drawings, in which:
Figure. 1 illustrates a block circuit diagram of the input controlled CLC filter based buck converter for solar power applications;

Figure 2 illustrates a control block diagram for the input controlled CLC filter based buck converter for solar power applications;
Figure 3 illustrates a graphical representation of simulated output for a controller of Emerson of the prior art;
Figure 4 illustrates a graphical representation of simulated output for a controller of Steca of the prior art; and
Figure 5 illustrates a graphical representation of simulated output for a controller of the current invention.
DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
According to this invention, there is provided a system with an input controlled CLC filter based buck converter for solar power applications.
Figure ] illustrates a block circuit diagram of the input controlled CLC filter based buck converter for solar power applications.
In accordance with an embodiment of this invention, there is provided a buck converter (BC) adapted to be coupled with a photovoltaic panel (PV). The photovoltaic panel provides a power source. Typically, the buck converter comprises a series connection of at least a buck inductive component (BL), at least a diode (BD), and at least a buck capacitive component (BCC). The at least a buck inductive component reduces ripple in current passing through it and the output voltage of the buck converter would contain less ripple content since the current through the load resistor is same as that of the inductor. Typically, the buck converter transfers packets of energy with the help of a power switch, a diode, and a buck inductive component and is accompanied by an output filter capacitive component and input filter,
Reference numeral Vpv is input PV voltage.

Reference numeral Ipv is input PV current.
In accordance with an embodiment of this invention, there is provided a CLC filter (CLC) adapted to receive input voltage and input current from a photovoltaic panel and to provide output voltage and output current to the buck converter. The CLC filter comprises at least a first capacitive component (C1) connected between the first and second input terminals, at least a second capacitive component (C2) in parallel to the first capacitive component (C1), and at least an inductive component (L) in series between the first capacitive component (C1) and the second capacitive component (C2). As PV voltage (voltage across capacitor C1) and PV current (current through inductor L1) both are controlled to limit the voltage and current ripple of the photovoltaic panel (PV). Capacitor C1 is of lower value and metal film type. Hence, system dynamics are fast. Thus using C-L-C filter and above control strategy enables the system and method to achieve higher tracking efficiency.
In accordance with an embodiment of this invention, there is provided a controller (CT). There are three states of the controller such as: i) voltage of first capacitive component (Vc1); ii) current of inductive component (IL1); iii) voltage of second capacitive component (Vc2)- These states are available for controlling through a control mechanism. Figure 2 is a block diagram of the controller and control mechanism, thereof.
Reference numeral 12 refers to a voltage comparator. Voltage (VC1) of first capacitive component is compared with a reference voltage (Vc1 ). This output is fed to a first capacitive component C1. Reference numeral 14 refers to a current comparator. Current (IL1) of first inductive component is compared with a reference current (IL1 ). This output is fed to a second capacitive component C2. Reference numeral 16 refers to an inward current transfer function block whose input is received from the second capacitive component and whose output is given to an outward current transfer function block and to an inward voltage transfer function block. Reference numeral 18 refers to an inward voltage transfer function block receives input from the inward current transfer function block and whose output is given to an outward voltage transfer function block. Reference numeral H1 refers to an outward current transfer function block (feedback). Reference numeral H2 refers to an inward voltage transfer function block (feedback).

Figure 3 illustrates a graphical representation of simulated output for a controller of Emerson of the prior art.
Figure 4 illustrates a graphical representation of simulated output for a controller of Steca of the prior art
Figure 5 illustrates a graphical representation of simulated output for a controller of the current invention.
Figures 3 and 4 illustrate ripples in waveform which are depictive of the variation in tracking maximum power point. Figure 5 illustrates a relatively smoother waveform which depicts that the maximum power point is easily tracked due to the used of this invention. The inventive step lies in providing a buck converter and a CLC filter in line in order to accurately provide maximum power point tracking and in order to reduce ripples. The present invention provides a buck converter to control the input voltage with CLC filter on input side instead of C/LC filters to track the accurate maximum power with very less ripple in PV voltage and PV current.
While this detailed description has disclosed certain specific embodiments of the present invention for illustrative purposes, various modifications will be apparent to those skilled in the art which do not constitute departures from the spirit and scope of the invention as defined in the following claims, and it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.

We claim,
1. A system with input controlled CLC filter based buck converter for solar power applications,
said system comprising:
a. at least a buck converter adapted to be coupled with a power source in order to transfers
packets of energy;
b. at least a CLC filter adapted to receive input voltage and input current from said power
source and to provide output voltage and output current to said buck converter; and
c. at least a controller adapted to work in at least three states of operation for controlling
said system in order to enable said system to achieve higher tracking efficiency for
maximum power point tracking.
2. The system as claimed in claim 1, wherein said power source is a photovoltaic panel.
3. The system as claimed in claim 1, wherein said buck converter comprising a series connection of at least a buck inductive component, at least a diode, and at least a buck capacitive component.
4. The system as claimed in claim 1, wherein said buck converter comprising a power switch, a diode, and a buck inductive component and being accompanied by an output filter capacitive component and input filter.
5. The system as claimed in claim 1, wherein said CLC filter comprising at least a first capacitive component connected between first and second input terminals, at least a second capacitive component in parallel to said first capacitive component, and at least an inductive component in series between said first capacitive component and said second capacitive component.
6. The system as claimed in claim 1, wherein said capacitor is of relatively lower value and of metal film type.

7. The system as claimed in claim 1, wherein said at least a controller being adapted to work in
at least three states of the controller, said at least three states being:
i) voltage of first capacitive component; ii) current of inductive component; and iii) voltage of second capacitive component.
8. The system as claimed in claim 1, wherein said at least a controller comprising:
I. at least a voltage comparator where voltage of first capacitive component is compared with a reference voltage, with compared output being fed to a first capacitive component ofsaidCLC filter; II. at least a current comparator where current of first inductive component is compared with a reference current, with compared output being fed to a second capacitive component of said CLC filter;
III. at least an inward current transfer function block whose input is received from said second capacitive component and whose output is given to an outward current transfer function block and to an inward voltage transfer function block;
IV. at least an inward voltage transfer function block adapted to receive input from said at least an inward current transfer function block and whose output is given to an outward voltage transfer function block;
V. at least an outward current transfer function block as feedback; and VI. at least an inward voltage transfer function block as feedback.