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 and method for maximum efficiency tracking in variable speed generator.
APPLICANT (S)
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company
INVENTOR(S)
Saha Raja, Wachasundar Shripad and Hassan Hafiz Imtiaz; all of Crompton Greaves Limited, Electronic Design Centre, Aryabhatta Building, CG Global R&D Centre, Kanjurmarg (East), Mumbai - 400 042, Maharashtra, India; all 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 power electronics and their control systems.
Particularly, this invention relates to a system and method for maximum efficiency tracking in variable speed generator.
BACKGROUND OF THE INVENTION:
Electrical components, devices, equipment require a continuous feed of electric power for their working. In some instances, failure of power supply is catastrophic to the component, device, and equipment and can lead to cascaded catastrophic events to the system, at large.
Hence, back-up power supply is provided to such electrical components. Back-up power supply may be provided by an engine or a generator such as a diesel generator. A diesel generator is the combination of a diesel engine with an electrical generator (often called an alternator) to generate electrical energy. Diesel generating sets are used in places without connection to the power grid, as emergency power-supply if the grid fails. Sizing of diesel generators is critical to avoid low-load or a shortage of power and is complicated by modern electronics, specifically non-linear loads.
During the switching from a main supply to a back-up supply, the speed of the engine of the generator needs to be set in accordance with the load that is to be served. Each engine is provided with a rated speed load curve which includes speed load corresponding characteristics.
Hence, according to the prior art system and method, a speed load characteristic monitor and adjustment is provided so that the diesel generator speed can be set in

accordance with the load. But there are further losses in in-line associated assemblies of the engine. These in-line associated assemblies include alternators and power electronics. If this same system and method is followed for a variable speed integrating generator, the engine has to cater to losses of generator and power electronics connected to the system, thereof.
There is a non-linear relationship between load and speed, as engine follows speed as demanded by load. This system and method includes the following drawbacks:
1. the characteristic between load (power) and speed is changed from system to system;
2. the implementation of this non-linear characteristic requires some linearization, which will cause error in speed identification; and
3. this characteristic is given for engine only, hence the characteristic for complete VSIG system will be different (as there will be losses in alternator, PMG, and power electronic systems).
Hence, there is no platform for accurate detection of optimum speed at which generator should operate at a given load, because losses occurring at the alternator and power electronics which are further in line after the generator cannot be accounted for. This leads to a non-optimum engine / generator operation, resulting in fuel losses. Eventually, this may result in depreciation of life or health of components of the back-up power supply system.
Hence, there is a need for finding out an integrated speed load characteristic for efficient operation of the back-up power supply system.
OBJECTS OF THE INVENTION:

An object of the invention is to provide a system and method for maximum efficiency tracking in variable speed generator; which provided maximum efficiency tracking in engines / generators of VSIG or back-up power supply systems.
Another object of the invention is to provide a system and method for maximum efficiency tracking in variable speed generator; which reduces fuel consumption of engines / generators of VSIG or back-up power supply systems.
Yet another object of the invention is to provide a system and method for maximum efficiency tracking in variable speed generator; which provides optimum speed for engines / generators of VSIG or back-up power supply systems for any load serviced by the engines / generators of VSIG or back-up power supply systems.
Still another object of the invention is to account for losses occurring in the backup power supply system.
SUMMARY OF THE INVENTION:
According to this invention, there is provided a system for maximum efficiency tracking in variable speed generator system, said system comprises:
a. flow meter adapted to be associated with an engine / generator of said variable
speed generator system for sensing flow rate of fuel to said engine / generator;
b. varying means adapted to vary speed of said engine / generator;
c. means to record fuel flow rate at a first instance before varying speed of said
engine / generator in order to obtain an old flow rate;
d. means to record fuel flow rate at a second instance before varying speed of said
engine / generator in order to obtain a new flow rate; and

e. control module adapted to control engine / generator speed in relation to comparison of said new flow rate and old flow rate in accordance with predetermined parameters of working.
Typically, said system comprises power measurement means adapted to measure power output from said variable speed generator system.
Typically, said system comprises speed measurement means adapted to measure speed output from said variable speed generator system.
Typically, said control module comprises reading means adapted to read data from said flow meter to measure fuel flow rate, at a first time instance, of the engine of the variable speed generator system, said measured fuel rate being an old flow rate
(Cold)-
Typically, said control module comprises reading means adapted to read data from said flow meter to measure fuel flow rate, at a second time instance, of the engine of the variable speed generator system, said measured fuel rate being a new flow rate (Cnew).
Typically, said control module comprises comparator means adapted to compare old flow rate with respect to new flow rate in order to obtain a comparative output.
Typically, said control module comprises speed varying mechanism adapted to vary speed of said engine / generator in relation to a comparative output.

Typically, said control module comprises speed increment means adapted to increment engine / generator speed if new flow rate is greater than the old flow rate.
Typically, said control module comprises speed decrement means adapted to decrement engine / generator speed if new flow rate is lesser than the old flow rate.
According to this invention, there is also provided a method for maximum efficiency tracking in variable speed generator system, said method comprises the steps of: i. sensing flow rate of fuel to said engine / generator; ii. recording fuel flow rate at a first instance before varying speed of said
engine / generator in order to obtain an old flow rate; iii. varying speed of said engine / generator; iv. recording fuel flow rate at a second instance before varying speed of said
engine / generator in order to obtain a new flow rate; v. comparing new flow rate with old flow rate; and vi. controlling engine / generator speed in relation to comparison of said new
flow rate and old flow rate in accordance with pre-determined parameters of
working.
Preferably, said method comprises the steps of:
vii. measuring fuel flow rate at first time instance in order to obtain an old flow
rate (C0ld); viii. increasing speed of said engine / generator; ix. measuring fuel flow rate at second time instance, after increasing speed of
said engine / generator, in order to obtain a new flow rate (Cnew); x. comparing said old flow rate (C0ld) with said new flow rate (Cnew);

xi. decreasing speed of said engine / generator if said old flow rate (C0ld) is
lesser than said new flow rate (Cnew.); and xii. increasing speed of said engine / generator if said new flow rate (Cnew) is lesser than said old flow rate (C0ld.).
Alternatively, said method comprises the steps of:
xiii. measuring fuel flow rate at first time instance in order to obtain an old flow
rate (C0ld); xiv. decreasing speed of said engine / generator; xv. measuring fuel flow rate at second time instance, after increasing speed of
said engine / generator, in order to obtain a new flow rate (Cnew); xvi. comparing said old flow rate (C0ld) with said new flow rate (Cnew); xvii. increasing speed of said engine / generator if said old flow rate (Cold) is
lesser than said new flow rate (Cnew.); and xviii. decreasing speed of said engine / generator if said new flow rate (Cnew) is
lesser than said old flow rate (C0ld)
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
Figure 1 illustrates a schematic of a conventional variable speed generator system.
The invention will now be described in relation to the accompanying drawings, in
which:
Figure 2 illustrates a schematic of a variable speed generator system;
Figure 3 illustrates a graphical view of speed versus flow-rate of working of engine of variable speed generator system of Figure 2.

Figure 4 illustrates a flowchart of the working of the variable speed generator system of Figure 2.
DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
Figure 1 illustrates a schematic of a conventional variable speed generator system.
A diesel generator or engine (E), an alternator (A), and power electronics (PE) are connected to a load (L) which requires the back-up electric power supply. Changes in load lead to changes in speed of engine. Although, speed load characteristics for the engine are provided, losses in alternator and power electronics are unaccounted for while supply is given to a load. Therefore, the engine speed may not function according to the rated speed load characteristics. This results in inefficient functioning of the engine and results in fuel wastage. There is a need for a system which optimises fuel intake to the engine by adjusting engine speed to optimal value.
According to this invention, there is provided a system for maximum efficiency tracking in variable speed generator system.
Figure 2 illustrates a schematic of a variable speed generator system;
Figure 3 illustrates a graphical view of speed versus flow-rate of working of engine of variable speed generator system of Figure 2.
Figure 4 illustrates a flowchart of the working of the variable speed generator system of Figure 2.

In accordance with an embodiment of this invention, there is provided a mass flow meter (FM) adapted to be associated with the engine / generator of said variable speed generator system. Usage of mass flow meter is to measure the flow rate (Volume / second) of fuel intake by engine.
In accordance with another embodiment of this invention, there is provided a control module (CM) adapted to control engine speed in relation to measured flow of fuel and in accordance with pre-determined parameters of working.
In accordance with an embodiment of the control module, there is provided a power measurement means adapted to measure power of the variable speed generator system that is being output.
In accordance with another embodiment of the control module, there is provided a speed measurement means adapted to measure speed of the variable speed generator system.
In accordance with yet another embodiment of the control module, there is provided a reading means to read data from the mass flow meter to measure fuel flow rate, at a first time instance, of the engine of the variable speed generator system. The first time instance is an old time instance. This measured flow rate is stored to be old flow rate (C0ld). Further, the fuel flow rate, at a second time instance, of the engine of the variable speed generator system is measured, after the speed of the engine is varied (increased). This measured flow rate is stored to be new flow rate (Cnew). The second time instance is a new time instance.
In accordance with still another embodiment of this invention, there is provided a comparator means adapted to compare fuel flow rate at first time instance with

respect to fuel flow rate at second time instance in order to obtain a comparative output.
In accordance with yet another embodiment of this invention, there is a speed varying mechanism adapted to vary speed of the engine in relation to comparative output. If the new flow rate is greater than the old flow rate, then speed varying mechanism increases engine speed. If the new flow rate is lesser than the old flow rate, then speed varying mechanism decreases engine speed.
At a particular load (power), speed is varied to track the minimum flow rate. The graph of figure 3 shows the three ISO power curve, where P3 > P2 > PI (power in kW). CI, C2 and C3 is the minimum fuel consumption rate at speed wl, w2 and w3 respectively.
According to this invention, there is provided a method for maximum efficiency tracking in variable speed generator system.
The following are the steps of the method:
Step 1: Start
Step 2: Measure Power (P). Measure Speed (W). Measure fuel flow rate at first
time instance, i.e. old flow rate (C0ld).
Step 3: Increase speed of the engine of the VSIG system.
Step 4: Measure fuel flow rate at second time instance, i.e. new flow rate (Cnew).
Step 5: Compare old flow rate (C0ld) with new flow rate (Cnew)-
Step 6: If Cnew> C0ld, then go to step 7, else go to step 3.
Step 7: Decrease the speed.
Step 8: Measure new flow rate.
Step 9: If Cnew > Cold, then go to step 3, else go to step 7.

The following are alternative steps of the method:
Step 1: Start
Step 2: Measure Power (P). Measure Speed (W). Measure fuel flow rate at first
time instance, i.e. old flow rate (C0ld).
Step 3: Decrease speed of the engine of the VSIG system.
Step 4: Measure fuel flow rate at second time instance, i.e. new flow rate (Cnew)-
Step 5: Compare old flow rate (C0ld) with new flow rate (Cnew).
Step 6: If Cnew> C0ld, then go to step 7, else go to step 3.
Step 7: Increase the speed.
Step 8: Measure new flow rate.
Step 9: If Cnew> C0id, then go to step 3, else go to step 7.
The technical advance of this invention lies in obtaining or varying speed of the engine or generator component of a VSIG system in relation to measured flow rate of fuel to the engine or generator component of the VSIG system.
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 for maximum efficiency tracking in variable speed generator
system, said system comprising:
a. flow meter adapted to be associated with an engine / generator of said
variable speed generator system for sensing flow rate of fuel to said
engine / generator;
b. varying means adapted to vary speed of said engine / generator;
c. means to record fuel flow rate at a first instance before varying speed of
said engine / generator in order to obtain an old flow rate;
d. means to record fuel flow rate at a second instance before varying
speed of said engine / generator in order to obtain a new flow rate; and
e. control module adapted to control engine / generator speed in relation
to comparison of said new flow rate and old flow rate in accordance
with pre-determined parameters of working.
2. The system as claimed in claim 1, wherein said system comprising power measurement means adapted to measure power output from said variable speed generator system.
3. The system as claimed in claim 1, wherein said system comprising speed measurement means adapted to measure speed output from said variable speed generator system.
4. The system as claimed in claim 1, wherein said control module comprising reading means adapted to read data from said flow meter to measure fuel flow rate, at a first time instance, of the engine of the variable speed generator system, said measured fuel rate being an old flow rate (C0ld).

5. The system as claimed in claim 1, wherein said control module comprising reading means adapted to read data from said flow meter to measure fuel flow rate, at a second time instance, of the engine of the variable speed generator system, said measured fuel rate being a new flow rate (Cnew).
6. The system as claimed in claim 1, wherein said control module comprising comparator means adapted to compare old flow rate with respect to new flow rate in order to obtain a comparative output.
7. The system as claimed in claim 1, wherein said control module comprising speed varying mechanism adapted to vary speed of said engine / generator in relation to a comparative output.
8. The system as claimed in claim 1, wherein said control module comprising speed increment means adapted to increment engine / generator speed if new flow rate is greater than the old flow rate.
9. The system as claimed in claim 1, wherein said control module comprising speed decrement means adapted to decrement engine / generator speed if new flow rate is lesser than the old flow rate.
10. A method for maximum efficiency tracking in variable speed generator system, said method comprising the steps of:
i. sensing flow rate of fuel to said engine / generator; ii. recording fuel flow rate at a first instance before varying speed of said
engine / generator in order to obtain an old flow rate; iii. varying speed of said engine / generator;

iv. recording fuel flow rate at a second instance before varying speed of said engine / generator in order to obtain a new flow rate;
v. comparing new flow rate with old flow rate; and
vi. controlling engine / generator speed in relation to comparison of said new flow rate and old flow rate in accordance with pre-determined parameters of working.
11.The method as claimed in claim 10 wherein, said method comprising the steps of: vii. measuring fuel flow rate at first time instance in order to obtain an old
flow rate (C0ld); viii. increasing speed of said engine / generator; ix. measuring fuel flow rate at second time instance, after increasing
speed of said engine / generator, in order to obtain a new flow rate
x. comparing said old flow rate (C0ld) with said new flow rate (Cnew); xi. decreasing speed of said engine / generator if said old flow rate (Cold)
is lesser than said new flow rate (Cnew); and xii. increasing speed of said engine / generator if said new flow rate (Cnew)
is lesser than said old flow rate (C0ld.)
12.The method as claimed in claim 10 wherein, said method comprising the steps of: xiii. measuring fuel flow rate at first time instance in order to obtain an old
flow rate (Cold); xiv. decreasing speed of said engine / generator; xv. measuring fuel flow rate at second time instance, after increasing speed
of said engine / generator, in order to obtain a new flow rate (Cnew);

xvi. comparing said old flow rate (C0ld) with said new flow rate (Cnew); xvii. increasing speed of said engine / generator if said old flow rate (C0ld) is
lesser than said new flow rate (Cnew); and xviii. decreasing speed of said engine / generator if said new flow rate (Cnew)
is lesser than said old flow rate (C0ld.)