Filed of the Invention

The present invention, "SWS - Small Windmill System", relates to Electricity Generation through variable & renewable like wind and hydro energy, without consuming ANY external electricity for generation of electricity! ! SWS, being a self-reliant & self-sufficient, can be used for Standalone Off-Grid power usages as primary source, or can be integrated with existing grid and provide backup in case of mains failures/ power cuts, or can acts as prolonged backup power for Disaster Management System, apart from pushing the excess power for daily consumption and offsetting the electricity bill from the day one.

Background of the Invention

Power from the Windmills and other renewable has become more important in the present scenario considering the ever growing power dependent population and the environment threatening pollution from fossil fuels. The Invention discussed here-in addresses the major short comings of already present renewables like (1) Solar, (2) Large (MW) windmills and (3) other Domestic Small (KW) windmills, which are as follows:

All the above three requires external power for its working either for generation or for regulation & charge control and even for electrical braking etc., so in absence of the external & backup power these systems become impotent, hence can't be relied upon, for standalone off-grid usages or as backup power for Disaster Management, as battery has limited backup capacity and in prolonged grid failure or failure of battery itself, these conventional power dependent systems will not deliver any useable power even when there is enough sun or wind available! ! All three power system fails when they are needed the most i.e. in prolonged power failures and in natural or manmade calamities. Further constant consumption of external power, even when not producing power, sometimes leads to negative metering i.e. consumes more power than it produces! !

Limitation specific to Solar System: it requires large surface area, regular cleaning & maintenance of panels and can't work when sun is at peak during the day because of high temperature.

Similarly, conventional Large MW windmills can't be used for Standalone Off-grid usages as it requires long transmission lines & sub-stations etc. so it is very capital intensive and is not for the mass. Other windmills require specific windy sites well placed on wind maps because these windmills has to overcome a very high starting torque because of withholding torque like in Permanent earth Magnet Generator (PMG) or high mechanical friction if geared. Other direct-drive variable speed windmills need to rotate at high RPM in-order to produce high power, which leads to higher mechanical wear & tear, faster blade erosion and constant operational loud noises. Limitation specific to other pear small PMG windmills are as follows: it has High Withholding Torque; Output power is proportionate to Speed so for higher power, such windmills have to rotate at high RPM; these are External Power Dependent windmills for AC-DC-AC conversion & charge controllers for utilization of generated power; the Earth Magnets losses its property with age, faults and temperature; a windmill designed for low wind will not have same efficiency at high winds and vice-versa.

The SWS- Small Windmill System is designed to overcome all of the above limitations of existing solar, MW windmills and pear Small Windmills. Like, SWS doesn't require high windy sites as there is no 'starting torque' requirement being a non-PMG and no gear frictions to overcome being direct drive; SWS adopt to given low or high winds by dynamically adjusting output KVA as per available input KW power of prime-mover; SWS, while yielding Maximum Power per Revolution can deliver its rated power at low RPM, so there are no mechanical stresses on the tower, significantly less blade erosion & little noise; efficiency and life span is not adversely affected because of temperature, aging, faults etc.; SWS is Electrical self-reliant so apt for Standalone Off-grid usages; while working with grid, SWS leads to Reverse Metering (not the Negative metering). With all the above strength, the SWS rightly placed for techno- commercial revolution in the area of renewable power utilization.

Object of the Invention

The main objectives of the present invention are to serve the mankind and to contribute to mother earth / nature through a technically advance, operationally safe & independent and commercially viable - renewable windmills like the SWS. These objectives are achieved by (1) Maximum Utilization of Wind, (2) Optimization of Generated Power, (3) Maximum Utilization of Generated & Stored Power, (4) Safety for the Windmill itself and the surrounding, (5) Quantifying & Registering the performance, (6) Low running & maintenance cost.

1. Maximum Utilization of any given Wind: The versatile SWS can generate power at constant rated efficiency with same ease in any winds be it low or high. Being a non-PMG; (i) SWS has No Starting Torque to overcome; and further since (ii) SWS uses the SEiSG (Self-Excited inverted Synchronous Generator) not the prevalent EESG or PMSG so there is No Load initially; and (iii) the unique hollow rotor design that provides Higher Moment of Inertia (in comparison to conventional solid shaft design) and acts as large fly wheel; (i), (ii) and (iii) together ensure that SWS is Always Already Rotating even in very low winds (1.5 to 2

M/S), that leads to higher UPTIME and better Capacity Utilization Factor. SWS, since already in state of motion (Law of Inertia), picks-up the rotational speed with little add-on wind and starts delivering usable power at around 3 M/S wind speed, irrespective KVA rating or the size of SWS i.e. both 5KW & 10KW models start respective power production at low winds. As soon as the generation starts the Digital - Dynamic Load Management System intelligently loads the SEiSG in way that the output KVA is always made equal to the input KW wind power available to shaft, at that point of time by converting Mechanical Speed to Electrical Torque. The electromagnetic field of SEiSG is manipulated such that the air gap flux leads to Maximum Power per Revolution, in any variable wind speed. Even at higher winds the RPM is maintained closer to optimum blade Tip Speed Ratio. All these ensure every drop of available wind be best utilized and leads Maximum Utilization of any given Wind.

In the present invention, Maximum Utilization of precious 'generated power' is achieved through the Digital, Ultra-Fast PWM (Pulse Width Modulation explained below in the controller system) Charge Controller with high charging current (upto 50ADC) and regulated charging DC voltage between min 110% to max 120% of battery series voltage depending on the availability of power. This restricts sulphonation & corrosion of plates, chemical overheating and saves battery life. Being PWM losses are negligible, further the charger doesn't load the generator. In-case of direct grid usage, o/p voltage is made constant by regulation of power at the generation level itself. Note - The System's charge controller doesn't use any external power for itself. So regulation is possible even when there is no AC or DC external power available! ! In the present invention maximum utilization of produced & stored power is achieved through proprietary Auto Changeover/ Toggling Switch that pushes the 'Wind Power' first & than the 'Stored Power even when the AC Grid power is available, this ensures maximum utilization of generated/ stored power from the day one and helps in Speedier Return on Investment by offsetting the Electrical Units and with best utilization of batteries on day-to-day basis which otherwise would have been lying unused till power back requirements arises. Further the Change-over Switch ensures on day-to-day basis the regulated/ controlled charging & discharging which saves battery life. Note 1- this auto toggling between Windmill Power and AC mains power is done without using any external power for itself! ! In-case of battery, the Auto changeover Switch Intelligently uses only the access battery power beyond the power requirement for backup! !

The windmill system ensures utter safety for itself and it's surrounding by protecting it from over-speed high RPM, open or no load voltage, short or full load high voltage. The present Windmill never fails to generate, regulate or brake & protect itself and surrounding for because of unavailability external electrical power. 5. The present system is provided with Smart Digital Energy Metering and a Data-logger. The proprietary energy KW/H meter digitally measures & cumulative stores the net true DC RMS (Root Mean Square value) Power being used for end uses after deducting all the internal losses and consumption. It quantifies just the net power produced/ stored and utilized. The Data Logging, stores other vitals like Maximum RPM attained Maximum Power delivered, Windmill Up-time and other performance related statistics for end-user's information. It does not require any external power; power measured is net of the power used by the meter too! !

6. The SWS- Small Windmill System has Low Maintenance and long life, achieved by minimum mechanical wear & tear, as it is a (1) Direct Drive and (2) rate of change of speed/ RPM i.e. acceleration & retardation always remain constant. Generation at constant & low RPM has many advantages like: Longer blade life as there is very little erosion due to air friction; Centrifugal forces at the hub root are exponentially low at slower RPM as it increases with speed at square of RPM; Noise level is low; Yawing is swift as little force required due to low momentum as compared to blades at high RPM. Further the generator being non-PMG and self-excited and at no load initially, so wake-up losses & stresses are low. Subsequent apt loading of the generator with respect to given wind ensure least resistance and hence smooth transition form no load to being loaded till reaches to full load. Generator type has no de-magnetization risk with time & temperature or faults, as in the case of other PMGs. Power at low RPM closer to optimum TSR (blade Tip Speed Ratio) leads to lesser erosion and hence longer life for Blades. Similarly even at high winds, the windmill's blades are fully loaded and are in state of motion, helping in converting wind's lethal Potential Energy to desirable Kinetic Energy for power generation there by not stressing the cantilever blades at root / hub. High standard components are used in electronics, hardware, bearings (SKF ZZ) and structure is also double hot zinc dipped; all this adds to safety & longer life of the system.

Summary of the Invention

The Invention achieves the above through the following core components:

1. Generator: An Inverted (Linear), Salient Pole, Synchronous Generator - SG with Self-exciting Field.

2. Controller: "Digital Dynamic Flux Management System", through algorithm that acts continuously non-discreetly on real-time dynamic data instead of working on general practice of using discreet samples or conditions based logic.

3. Digital Controlled Auto Change-over Switch and Dump Load management system pushing the Windmill Power First and then uses AC Mains if required along with protecting the system from No Load,

Over Voltage and high RPM etc.

Generator / alternator are an electrical machine that converts mechanical energy to electrical energy in the form of alternating current. These can be broadly classified as:

1. Induction Generators - because of various reasons, IGs are not used in the small windmills and hence are not discussed here-in.

2. Synchronous Generator (SG) is universally used for small windmills and can further be classified based on the field type and its excitation. Different types of SG based upon Field Type are as follows:

1. Rotating magnetic field with a stationary armature, this is mostly used for the reasons of cost & simplicity.

2. Stationary magnetic field with rotating Armature i.e. the Linear or Inverted SG are very occasionally used in the industry and has never been used for windmills. The revolving armature type has the armature wound on the rotor, where the winding moves through a stationary magnetic field. These are apt for low speed operations.

3. Permanent Magnet Field with coil wound armature. An alternator that uses a permanent magnet for its magnetic field is called a magneto. This PMA are prevalent in the windmills and called PMSG

Based on the Field Pole Types, SG are further classifies as either (1) Non- Salient or Cylinder Pole SG and (2) Salient Pole. The SWS use Salient Poles which are more common in slow & variable speed machines and hence require more number of poles, as 'Speed = 120 * frequency / Pole' i.e. RPM is inversely proportionate to number of poles. Salient Pole SG has large diameter and short axial length actually helps the SWS's center of gravity being closer to the CG of the tower and most of the weight is directly on the tower rather being cantilever or hanging out of the tower, this reduces the cost of material.

Since the early time of developing wind turbines, considerable efforts have been made to utilize three-phase synchronous machines. AC synchronous WTGs can take constant and DC excitations from:

1. Permanent Earth Magnets and are thus termed PM synchronous generators i.e. PMSG. These are very common as windmill generators but has lot of limitations like Permanent magnets are expensive; the synchronicity may cause problems during startup, synchronization & voltage regulation; does not readily provide a constant voltage; the synchronous operation causes also a very stiff performance in the case of an external short circuit, and when the wind speed is unsteady. Another disadvantage of PMSGs is that the magnetic materials are sensitive to temperature; for instance, the magnet can lose its magnetic qualities at high temperatures or during a fault. 2. Electrically externally excited synchronous generators - EESG.

3. Self-Excited Synchronous Generators - SESG. These are very rarely used as windmill generators.

Unprecedented as windmill generator & unlike any other, the generator is in an Inverted Synchronous Salient multi-pole Generator with Self-exciting Field using its own armature power through digitally controlled AC-DC convertor, in closed loop.

4. This is why and how the SWS has created altogether a new class / category in WTGs henceforth know as the "Self-Excited inverted Synchronous Generator" - SEiSG.

In PMSG & EESG, when the rotor is driven by the wind turbine, three- phase power is generated in the stator windings which are connected to the grid through transformers and power converters, but in the SEiSG when the rotor rotates then three phase AC power is produced in the rotor itself, which is collected from the slip-ring and brushes, as shown in the figure 10. For fixed speed synchronous generators, the rotor speed must be kept at exactly the synchronous speed. Otherwise synchronism will be lost. But in SEiSG rotor speed can be varied being a variable speed direct drive.

Figure-11, illustrate the different types of WTGs which are in use by different manufacturers. Comparing the generator with following WTGs available shall highlight how different is the Generator is:

Types of Wind Turbine Generators, based on the "Speed":

1) Constant speed Turbines and 2) Variable-speed Turbines.

Types of WTGs presently in use as per the speed are: 1. Fixed speed, 2. Limited variable speed, 3. Variable speed with partial power electronic conversion, 4. Variable speed with full power electronic conversion,5. Mechanical torque converter between rotor's low-speed shaft & generator's high-speed shaft controls the generator speed to the electrical synchronous speed.

Types of Wind Turbine Generators based on Generator type:

1. Squirrel cage induction generator, (SCIG),

2. Wound rotor induction generator, WRIG are of two types:

1) Opti-Slip (OSIG) and 2) Doubly-fed (DFIG)

3. Synchronous Generator, SG in present use has two types:

1. WRSG - Wound Rotor Synchronous Generator.

2. PMSG - Permanent Magnet Synchronous Generator.

Electrical aspects of variable speed WTGs: variable speed operation is desirable for two main reasons - (1) in below rated wind speed, it can extract the most energy if the TSR (Tip Speed Ratio) can be kept constant, requiring that rotor speed varies with wind speed, and (2) variable-speed operation results in reduced fluctuating stresses, and hence reduced fatigue. Variable speed operation is possible with the following types of generator: 1. Synchronous Generator (SG) - PMG and SESG - Separately Excited (Electromagnetic Field) Synchronous Generator.

2. Induction generator - Squirrel cage and Wound Rotor

3. Switched reluctance generator.

The most common out of above for continues variable speed is PMSG or EESG As can be seen from the above, in small windmills, for variable speed WRSG or PMG are used. But never has been used the SEiSG.

Clearly, it is beneficial to operate WTGs at variable speed. The reasons are several. When the wind speed is below rated, running rotor speed with the wind speed and keeping the tip speed ratio constant ensure that the wind turbine will extract the maximum energy. Variable speed operation helps reduce fluctuating mechanical stresses on machine shaft, the likelihood of fatigue and damage as well as aerodynamically generated acoustic noise. The rotor can act as a regenerative storage unit (e.g. flywheel), smoothing out torque and power fluctuations prior to entering the power generation. Direct control of the air-gap torque also aids in minimizing RPM fluctuation. Furthermore, variable speed operation enables separate control of active and reactive power, as well as power factor. In theory, some wind turbine generators may be used to compensate the low power factor caused by neighboring consumers. In economic terms, variable speed wind turbine can produce 8-15% more power than fixed speed counterparts. Considering the aforesaid advantages and many more the SWS - Small Windmill System's SEiSG is designed to be a variable & direct drive. Figure 12 - Example of Variable speed control system.

Synchronous generators are a proven machine technology since their performance for power generation has been studied and widely accepted for a long time. In theory, the reactive power characteristics of synchronous WTGs can be easily controlled via the field circuit for electrical excitation. In the case of using electromagnets in synchronous machines, voltage control takes place in the synchronous machine just like SEiSG where the output power is controlled by managing the air-gap flux using 'Digitally controlled Dynamic Load Management System'.

The conventional 'control systems' and the difference & advantage of the Dynamic Load Management Control System:

The primary purpose of any control system for wind turbines is to manage the automatic operations safely. A well designed Control System reduces the operating cost, provides consistent dynamic response, improve product quality, and ensure safety. Without it, no windmill can produce power, successfully & safely.

There are two types of controls systems based on the functioning- (1) Supervisory and (2) Dynamic controls. The Dynamic control manages those aspects of Windmill operation in which the dynamics affect the outcome of the controlled aspects. The dynamic control system is applicable to constant as well as variable speed WTG, but differently.

The Digital- Dynamic Flux/Load Management System (DDLMS) is Dynamic Control type and designed for Variable Speed, Direct Drive Windmill.

The aerodynamic torque affects all operations of a turbine and provides power that is delivered to load. It is the net torque from the wind, consisting of contributions related to the rotor tip speed ratio, blade geometry, wind speed, yaw error and any added rotor drags. Each of the above but for wind speed can be altered using a Control System, like DDLMS.

In a constant speed WTGs, generator torque is function of the fluctuating aerodynamic torque as the drive train and generator dynamics are fixed by design - Constant speed generator torque = f (aerodynamic torque, system dynamics)

Thus only method for controlling the generator torque, in a constant speed WTGs, is controlling the aerodynamic torque.

The Variable-speed WTGs can operate at different TSRs. Below rated wind, controller tries to maximize the aerodynamic torque / power and above rated wind, the controller attempt to limit the aerodynamic torque. In a variable speed, pitch regulated turbine, the generator torque can be varied independently of the aerodynamic torque and other system variables. That is - Variable speed generator torque = f (generator torque control system) In such a system the aerodynamic and generator torques can be independently controlled. The speed can be altered by change either the aerodynamic or generator torque, resulting in either an acceleration or retardation of the rotor. The DDLMS controls & manage the Generator Torque.

Normally, a Control System has following five components:

1. A process that has point(s) that allows the process to be changed or influenced. Controllable Processes in WTGs are - (1) Development of aerodynamic torque, (2) Development of generator torque, (3) Conversion of electrical current into motion e.g. Yaw & pitch control, (4) Conversion of electrical power from one form to another (AC-DC- AC converters, Charge controllers), (5) overall conversion of wind energy into electrical power i.e. converting Kinetic energy into

Electrical energy.

2. Sensors are indicator to communicate the state of the process to control the system. Wind Turbine Controller's Sensors are used to sense or measure - speed, temperature, position, electrical parameters etc.

3. A controller, consisting of H/W or S/W logic, to determine what controls actions should be taken. It may consist of computers, electrical circuits or mechanical system. Wind Turbine Controllers, provides the connection between the measurements of an aspects and actions to affect that operation. It consist of - Mechanical mechanisms, Electrical Circuit providing a direct link from the o/p of the sensors to desired control action e.g. PLC signal can be used to energize the relay coil etc., and Computers or PLC can handle digital and analog I/P and can be programmed for complex logics and provide dynamic response, ease of changing the code at any given time gives it an added advantage.

4. Power amplifiers provide power for the control action. Power Amplifier in Wind Turbines amplifies the week signals from the controllers for Actuator, like Relays, SCR, MOSFET etc.

5. Actuators are components for intervening in the process to operation of the system. Wind Turbine Actuators include - Electromechanical device e.g. DC motors, Hydraulic piston, and resistance heaters or fans.

A controller can control processes like development of Aerodynamic &

Turbine Torque and conversion of electrical energy into motion. DDLMS varies (increases or decreases) the field excitation with respect to RPM depending on the available wind, for fetching Maximum Power at that moment.

There are many design approaches for controller programming like - 'Adaptive Control', Optimal Control', 'Search Algorithm' which constantly change the rotor speed in-order to maximize the rotor power, and 'Quantitative Feedback Robust Control' which is a frequency domain approach for system with uncertain dynamics, working in a closed loop. The DDLMS primarily uses the Search Algorithm apart from Quantitative Feedback Robust Control Logic. A closed loop controller is - very accurate, unaffected even with non-linearity, and external noise is significantly reduced because of feedback mechanism which clears out the errors between input and output signals. Closed-loop transfer function in control theory is a mathematical expression algorithm describing the net result of the effects of a closed (feedback) loop on the input signal to the circuits enclosed by the loop. Standard methods like Proportional, Derivative, and integral controls. Example: The summing node and the G(s) and H(s) blocks can all be combined into one block, which would have the following transfer function: Y(s)/X(s) = G(s)/(l+G(s)*H(s)).

Linear Control theory applies to systems made of devices which obey the superposition principal, which means roughly that the output is proportional to input. They are governed by linear differential equations. These systems are amenable to powerful frequency domain mathematical techniques of great generality (bandwidth, frequency response & resonant, gain, poles, & zeros).

DDLMS is closed loop with negative feedback, Linear / Frequency domain control system.

In a conventional "Dynamic Generator Torque Control method" the speed at which a wind turbine rotates is controlled for - efficient power generation and to keep the turbine components within designed speed and torque limits. This is important as the centrifugal force on the spinning blades increases as the square of the rotation speed, which makes this structure sensitive to over-speed and the power of the wind increases as the cube of the wind speed. Wind turbines have ways of reducing torque in high winds. In a variable-speed WTG, when the wind speed is below rated, generator torque is used to control the rotor speed in order to capture as much power as possible. The most power is captured when the Tip Speed Ratio is held constant at its optimum value (typically 6 or 7). This means that as wind speed increases, rotor speed should increase proportionally. The difference between the aerodynamic torque captured by the blades and the applied generator torque controls the rotor speed. If the generator torque is lower, the rotor accelerates, and if the generator torque is higher, the rotor slows down. But it is difficult to find exact TSR, as it changes with time, location & wind type.

Tip Speed Ratio is the ratio of rotor speed to wind speed. The wind at hub is different than the wind at blade tips so the controllers using wind speed at hub for TSR will have some error. Moreover the efficiency of the systems designed to track and be closer to TSR depends upon the controller ability to change the rotor speed with wind which leads to mechanical stress, so any approach using TSR for rotor speed will not be error free and will not solve the basic problem itself.

Considering the limitations of the above methodology, DDLMS opted out of TSR calculation and chasing or accelerating suddenly to catch up with the varying winds, to keep the rotor speed closer to dynamically calculated TSR. Rather, DDLMS works on divergence of the standard theory of Search Algorithm (which tries to calculate rotor speed for maximum power at each moment. Search Algorithm maximizes rotor energy capture inspite of poorly understood rotor performance, icing, mis-pitched blades etc. In contrast to this existing methodologies, the DDLMS actually ensures that the generator is always be just appropriately loaded (neither less nor more) at any / all the given Wind Speeds & RPM while taking in account the external connected loads, too. The Output KVA of the SEiSG is matched to Input KW of the direct drive prime-mover, at any given point of time and wind speed. This unconventional approach achieves the following:

(1) Maximum possible Power per rotation or revolution, irrespective of wind speed and RPM.

(2) Rate of change rotor speed with respect to wind will always remain constant.

(3) This leads to minimum mechanical stress on the blades, tower and the other parts of the windmill, which adds to longer life and low maintenance and reduced cost per unit produced. The Wind Speed / RPM and the Field current (Load) relationship can be further explained, as under. Considering,

1. An electric machine used as a generator converts torque into current.

AND

2. As per the, 'John Smeaton', three basic rules about wind which are still applicable to windmills, though discovered in 18 ^th century:

a. The speed of blade tip is ideally proportional to speed of wind. For a direct drive generator the rotor & blade speed will be proportional to wind speed.

b. The maximum torque is proportional to speed of wind squared, c. The maximum power is proportional to speed of wind cubed.

Windmill Systems, where there is an energy or power balance: If, (Output Electrical Power) = (Input Mechanical power), then, RPM will remain constant. I.e. RPM remains constant (or within a range), when the O/P load is matched to I/P Power, irrespective of quantum of input & output powers.

As Generator is a device for converting torque into current, so when, mechanical speed is converted into Torque / Current through the Digital Dynamic Load Management System then the rate of change RPM almost remained constant.

In mechanical terms, Power = Torque * Angular Speed (1)

.'. Power is proportional to Angular Speed, if torque remains the same or

Power is proportional to Torque, if Angular Speed remains the same.

So it can be concluded that Mechanical power is proportionate to RPM, if Torque is constant.

In electrical terms, Power = voltage (E) * current (2),

Note: Induced Voltage (E) is the rate of change of flux "d p/d/" (developed by the interaction of the rotor magnetic field with the moving conductors). So it can be concluded that Electrical Power is proportionate to RPM (rate of change of flux), if Excitation Current remains constant. Since, Input power (mechanical) is proportional to (RPM * torque), and also Output power (electrical) is proportional to (RPM * current)

If I/P =0/P then, the output electrical current being drawn from the generator is proportional input mechanical torque applied.

So if, changes in input torque are matched by changes in output current using either negative feedback mechanism like the Digital Dynamic Load Management System, then the 'rate of change speed' will almost remain constant while KW generation will increase in square proportion with increase of wind.

Complex algorithm of DDLMS, continuously respond to continues realtime data (i.e. not on a discrete or sample based data) so its performance is not restricted by system clock or any external errors. But other Digital Systems are not continuous as DDLMS, but rather are sampled. Sampling and the dynamics of the A/D converters give rise to number of issues specific digital control system. The sampling rate is controlled by controller clock, affects, (1) the frequency content of processed information, (2) the design of control system, and (3) system stability. Sampling rate affect the subsequent control design and operation, including the determination of the values of constants and final system damping ratio, system natural frequency etc. Because of these effects, changes in sampling rate can also turn a stable system into unstable.

Further, The 'Digital - Dynamic Load Management System' uses PWM technology for regulation of Field Voltage based on the proprietary algorithm.

PWM - Pulse-width modulation or pulse-duration modulation (PDM), its main use is to allow the control of the power supplied to electrical loads. The average value of Voltage & Current fed to the load is controlled by turning the switch between supply and load on and off at a fast rate. The longer the switch is ON compared to the OFF periods, the higher the total power supplied to the load. The term duty cycle describes the proportion of On' time to the regular interval or 'period' of time; a low duty cycle corresponds to low power, because the power is off for most of the time. Duty cycle is expressed in percent, 100% being fully on. The main advantage of PWM is that power loss in the switching devices is very low. When a switch is off there is practically no current, and when it is on and power is being transferred to the load, there is almost no voltage drop across the switch. Power loss, being the product of voltage and current, is thus in both cases close to zero. PWM works well with Digital Control, which, because of their on/off nature, can easily set the needed duty cycle. Digital Control - By controlling analog circuits digitally, system costs and power consumption is drastically reduced. The microcontroller used here-in includes the PWM controller and includes two, each of which has a selectable on-time and period. The duty cycle is the ratio of the on-time to the period: the modulating frequency is the inverse of the period. One of the advantages of PWM is that the signal remains digital all the way from the processor to the controlled system; no digital-to-analog conversion is necessary. By keeping the signal digital, noise effects are minimized. Increased noise immunity is yet another benefit of choosing PWM over analog control. PWM is economical, space saving, and noise immune. Actual Working based on the above theory the technology and logic, is as follows:

Since the generator is self-excited and its field also draws power from its armature in a closed loop using AC-DC converter & amplifier till the buildup voltage reaches the threshold, then the "Digital Dynamic Load Management System" while maintaining the minimum field voltage starts managing the field voltage / current in way that the generator is never loaded beyond the prime-mover's than KW capacity, while the remaining armature AC power is made available for variable end usages though Voltage or Charge Controller. Note while the OP voltage varies and there may be difference between demand & supply of power, still the field current regulation remains the first priority.

DDLMS further regulates the field with respect to given wind and load, in such a way that SEiSG is never loaded beyond the present KW capacity of the prime mover, i.e. the electrical output KVA of SEiSG is made equal to input mechanical KW to the SEiSG.

When wind is positive (more) from the previous sensed wind the DDLMS also instantly increase the field excitation in way (gradually in number of dynamically calculated steps) and by exactly an amount, again dynamically calculated that output KVA is made equal to input KW. Similarly, when wind speed recedes from the previously sensed wind then field excitation is weakened tweaked for equilibrium is maintained.

Aforesaid technology and the processes are far more complex than it has been made to look-like here, for shear understanding purposes. But irrespective of complexity, what DDLMD attained is uniquely new & revolutionary; the end result is that DDLMS leads to a "Soft Start" while the windmill is self-excited, ensures "maximum power per revolution" and a constant/ linear "rate of change of speed/ RPM", irrespective of wind speed and the end load, as graph of SWS 5KW model with no load current of 1.4ADC & Full Load current of 6ADC and max RPM of 150.

In practical terms, for end-user, above technical advancements translates into (1) No Negative Metering being external power independent and so only can empower & support the electrical usage much beyond the backup hours in situation of prolonged grid failures, (2) faster Return on their Investment (Rol) because of much higher output and subsequent low maintenance cost since blades, tower and other parts are not subject to continuous momentum and stress as the Rate of Change of Speed is Constant i.e. acceleration and retardation remains constant even in turbulent and varying wind and even the while starting the gradual loading helps to averse the turbine wake losses, (3) low noise and blade erosion being not into the race of chasing the speed closer to TSR, (4) utter Safety - DDLMS being placed next/ closer to the source i.e. parameters which is to be sensed - wind speed/ RPM/ Voltage and the one which is to be altered (Field Voltage) so there are no transmission losses, execution delays and NO EXTERNAL DISTORTIONS, further being in closed negative feedback loop, along with other safety measures makes it highly reliable, (5) above all DDLMS is self-reliant i.e. it doesn't require any external power for its functioning, this gives great safety to the whole system in-case of power as well backup power failures. In nut shell, peace of mind and money saving is what end-user gets with this Digital- Dynamic Load Management System. BRIEF DESCRIPTION OF THE DRAWINGS

It will be convenient to further describe the present invention with respect to the accompanying drawings that illustrate possible arrangements of the invention. Other arrangements of the invention are possible, and consequently the particularity of the accompanying drawings is not intended to be limiting of the present invention.

Fig. l represents the block diagram of system

Fig.2 represents the Armature

Fig.3 represents the actual MS body of poles

Fig.4.1 represents the back cover for shaft mounting

Fig.4.2 represents the front cover

Fig.5 represents the rotor shaft for armature winding

Fig.6 represents the actual view of the present windmill

Fig.7 represents the rotating armature static filed

Fig.8 represents the variable speed electrical torque controller

Fig.9 represents the commonly agreed windmill

Fig.10 represents the rotors rotor itself, which is collected from the slip-ring and brushes,

Fig.11 represents the different types of WTGs

Fig.12 Example of Variable speed control system.

Fig.13 represents the block diagram of flax management system

Fig.14 represents the flow chart of digital controlled load

management system

Fig.15 represents the algorithm of auto change over switch

Fig.16 represents the block diagram of digital controlled auto change over switch

Before explaining the present invention in detail, it is to be understood that the invention is not limited in its application to the details of the construction and arrangement of parts illustrated in the accompanying drawings. The invention is capable of other embodiments, as depicted in different figures as described above and of being practiced or carried out in a variety of ways. It is to be understood that the phraseology and terminology employed herein is for the purpose of description and not of limitation.

The SWS - Small Windmill System, primarily consist of following: (1) Generator, (2) Digital Control, apart from the (3) Prime-mover - blades, hub, nose cone, (4) Wind guiding mechanism - Yaw, Tail and Transmission Assembly, (5) Tower & foundation plates, (6) Battery & Inverter, (7) Dump Load. For the sake of safety of the system and to save time & cost of packaging, loading, transportation, unloading; the SWS's, out of above constituents, the blades and tower are packed separately / individually while the Generator comes with foot mounted yaw & transmission assembly, tail at rear end and the hub on the shaft comes preassembled. Once unloaded and assembled on site, towers are stacked in descending order and can be erected on pre constructed foundation. Hub and blades are kept mechanically locked while lifting the preassembled generator, hub, blade, yaw, tail unit. Once all the nut-bolts fastened then the transmission wire is terminated at the bottom of yaw.

Other end of this wire is then terminated at RYB terminals of the control panel along with the custom designed dump resistive load at Rl & R2 and the Series Battery bank positive at B+ & negative B-, and Phase -> P & Neutral -> N are connected to Input AC Mains and Output to Inverter. Now when erection and installation is over, blades are released from mechanical brakes and ready to rotate.

Since the SEiSG by design has no starting torque and are not electrically loaded; so very soon, with little wind, rotation starts, and the wind's potential energy gets converted into kinetic energy as blades are directly mounted on the shaft. The rotor Armature Coils starts rotating in a weak residual flux of the Stationary Field (inverted SG) - Stator. Till 15 - 20 RPM, there will be no useful power output, since electromagnetic field is self-excited ¹ . But from the very first rotation, the armature 3 phase AC power though very insignificant till now, is converted into DC using a full wave bridge rectifier along with filters and other electronics, and is fed to field via a soft start circuit in a closed loop, using transformation & rectification method. This method depends on residual magnetism retained in the iron core to generate weak magnetic field which would allow weak voltage to be generated. Otherwise a generator/ alternator, not using a permanent magnet, require a DC field current for excitation ² . The field may be separately excited by a source of DC, such as a battery, or self-excited by being connected to the armature of the generator so that the generator also provides the energy required for the field current, as in SWS's SEiSG. After the self-excitation & soft-starting and once the build-up threshold voltage achieved; the pre-programmed and wired, ready to use DDLMS - 'Digital Dynamic Load Management System', takes up the control of distribution of generated AC power between field DC and the AC end-load. And very little power from the armature is fed to the filed managed by the proprietary windmill turbine controller system. DDLMS Micro-Controller is fed (Input) with (1) wind speed - sensed using a digital anemometer based sensor; (2) RPM - from Analog to Digital (A/D) Converter; (3) Field Current - through IC based analog circuit (A/D), SEiSG AC RYB; and at the output it is feed back to (1) Field - through D/A converter circuit. DDLMS logic, here, is simplified for the explanation purpose and can be represented in brief in fig 16 of flow chart.

The DDLMS is powered from the SEiSG, through the yaw mounted regulated power supply i.e. no external power is used either for generation or for power generation control system. Once the field is excited and regulated with respect to available wind speed and RPM, the generated AC power is further made available through transmission wires to the ground level Control Panel; consisting of regulation transformer, regulated power supply unit for the panel itself, AC-DC convertor full wave bridge-rectifier, micro-controller, MOSFET drivers, MOSFET, Contactor and Relay etc. This Control Panel Unit has Charge Controller, Voltage & Speed Protection and the Auto-Changeover Switch along with the other display and manual control mechanism, as explained in the block diagram.

Self-excitation ¹ : When some of the power output from the armature is used to power the field coils. The field retains magnetism when the generator is turned off. The generator is started with no load connected; the initial weak field creates a weak voltage in the armature coils, which in turn increases the field current, until the machine "builds up" to full voltage. Note: As the SEiSG uses field coils, the field current must be supplied; otherwise the generator will be useless. Thus it is important to have a reliable supply. Although the output of a generator can be used once it starts up, it is also critical to be able to start the generators reliably. In any case, it is important to be able to control the field since this will maintain the system voltage.

2'

Excitation In the case of a machine with field coils, a current must flow in the coils to generate the field; otherwise no power is transferred to or from the rotor. The process of generating a magnetic field by means of an electric current is called excitation. Starting : Self-excited generators must be started without any external load attached. An external load will continuously drain off the buildup voltage and prevent the generator from reaching its proper operating voltage.

While, the invention has been described with respect to the given embodiment, it will be appreciated that many variations, modifications and other applications of the invention may be made. However, it is to be expressly understood that such modifications and adaptations are within the scope of the present invention, as set forth in the following claims.