Matlab Simulation of an Induction Generator Based Ac/Dc Hybrid Electric Power Generation System

INTRODUCTION

According to the statistics and the forecasts from the International Civil Aviation Organization (ICAO), the revenue passenger-kilometers (RPK) of global air transport has grown at an average yearly rate of 6.2% since 2003, and will continue to grow at an average rate of 4.5% until the year 2030 (Haitham, et. al., 2014). The electrical power produced at the generating station is delivered to the consumers through a network of transmission and distribution systems. It is difficult to draw a line between the transmission and distribution systems of large power system. The transmission and distribution systems are similar to man‘s circulatory systems. The transmission systems may be compared with in the human body and distribution systems with capillaries. They serve the same purpose of supplying the ultimate consumer in the city with life giving blood of civilization electricity. The electrical power is almost exclusive generated, transmitted and distributed in the form of alternating current. Most of the load are inductive in nature and hence have now lagging power factor. The low power factor is highly as it causes an increase in current, resulting in additional losses of real power in all the elements of power system from power generator to the utilization device. These days the most utilized charging devices for EV/HEV are regulation, that implies they permit having power spill circuit of lattice to the vehicle battery, however many research establishments are attempting to apply bi regulation charging device, with battery to network control stream. A several arrangements have the battery, or some other vitality source, similar to super capacitors or flywheels, included linear forwardly in the charging stations or UPS system. Over the last thirty years, remarkable progress has been achieved in the aircraft development moving toward MEA, where many hydraulic, mechanical, and pneumatic powered subsystems have been fully or partially replaced by electrical systems (Haitham, et. al., 2014). However, the magnitude of the benefits and negative consequences for adopting MEA initiative varies from different technical approaches which includes new electrical power system architectures and different generator types. In this paper the control scheme with constant power and sinusoidal current compensation is clarify by the creators. This paper shows a changed control scheme to compensate a distribution feeder loading with non-linear loads. The compensation comprises of three principle destinations that are:- i) Regulation of real power deliver to loads

iii) Correction of power factor.

Over the past forty years, considerable amount of research has made remarkable progress to move towards more electric aircraft systems. In recent MEA systems, numerous mechanically, hydraulically, or pneumatically powered subsystems are partially or even completely replaced by electrical counterparts. Power quality is defined as a capability of system or an equipment to function satisfactorily in its electromagnetic environment with circuit introducing intolerable electromagnetic disturbance to anything in that environment. Power quality is the combination of voltage quality and current quality. This power quality is concerned with deviations of voltage and current from the ideal. Power quality is a set of electrical boundaries that allows a piece of equipment to function in its manner with circuit significant loss of performance. They were probably susceptible to whatever power quality anomalies existed at the time but the effects were not readily discernible due to the robustness of the machines and lack of effective ways to measure power quality parameters.

A basic schematic of the non-propulsive power distribution of conventional aircraft is shown in Figure 3.1. In conventional aircraft, the jet fuel is consumed by the gas turbine engine to generate power. Most of this power is used for propulsion of the aircraft, whereas the remainder is converted into pneumatic, hydraulic, mechanical and electrical power, where:- • Pneumatic power is obtained from the high pressure compressors of the gas turbine engine. This form of power is used to supply high pressure bleed air for the environmental control system (ECS) and wing anti-icing system. For a 300 passenger civil aircraft with 40 MW equivalent propulsion thrust, the pneumatic power needed is about 1.2 MW.

The performance of the hybrid non-propulsive power system of aircraft has been improved over the years, yet its complexity has grown even faster. Presently, the conventional non- propulsive power system still represents a major factor in aircraft malfunctions and failures. Furthermore, because of the inflexible infrastructure of the pneumatic and hydraulic systems, the leakage of the systems is generally difficult to locate or accessed, resulting in a great number of aircraft maintenance \down-times" and even flight delays. Optimizing the hybrid non-propulsive power system with incremental changes to existing products individually has become increasingly difficult The AC and DC variable speed drives used on board holder cranes are critical supporters of aggregate harmonic current and voltage distortion. While SCR phase control makes the attractive normal power factor, DC SCR drives work at not as much as this. What's more, line notching happens when SCR's commutate, making transient peak recovery voltages that can be 3 to 4 times the ostensible line voltage depending on the system impedance and the speed of the drives. The frequency and severity of these power system disturbance differs with the speed of the drive. Harmonic current injection by AC and DC drives will be highest when the drives are working at slow speed. Power factor will be most reduced when DC drives are working at slow speed or during acceleration and deceleration periods, increase to its greatest value when the SCR's are phased on to deliver evaluated or base speed. Above base speed, the power factor basically stays constant. Through the work of researchers and engineers all over the world, the list of mechanical, pneumatic and hydraulic loads to be replaced by electrical counterparts are growing progressively over time. Presently, novel means of generating, distributing, storing and using non-propulsive power on board are investigated and examined at aircraft level. A possible non-propulsive power system concept of MEA is shown in Figure 3.2.

In aircraft systems, the effect of electrical power off take can sometimes have significant impact on the dynamics and control of the aircraft engine. For instance, during the transition from cruise to descent phase, the aircraft engine power is transiently reduced while maintaining high electrical power demand. This transition creates a possibility of engine instability and may require substantial electric load shedding. Furthermore, with the increasing electric power consumption in MEA, the above effect will be more severe if the electric power is solely extracted from the HP spool of the gas turbine engine. This issue can be resolved by installing an extra generator on the LP spool of the engine and sharing the power extraction between the HP and LP spools.

The idea of adding a fan-shaft generator on the low pressure spool has been widely accepted with the concept of MEE. In a twin-spool aircraft engine, the generators on HP and LP spool operate at different frequencies. In order to parallel the two generators with enhanced efficiency and reduced size and weight, a DC primary generation system with power electronic converters is preferred as an advanced more electric architecture. PM generator has been speed starter/generator and a low speed generator are placed directly on the HP and LP spool of the engine, respectively. In the engine starting process, the PM starter/generator on HP spool can operate as a motor to start the engine using ground power supply.

In AC primary generation system, the frequency insensitive loads are powered directly from the synchronous generator terminals, where the AC load voltage is regulated by adjusting the excitation of the field winding of WFSG according to the shaft speed variation. A new approach of generating CVVF AC power directly from the generator terminals without external excitation is required in the new power generation system under MEE concept.

The proposed induction generator based AC/DC hybrid generation system is shown in Fig. 4.1. In the proposed system, a high speed open-end winding squirrel-cage induction starter/generator and a low speed conventional wye-connected squirrel-cage induction generator are attached to the high pressure (HP) and low pressure (LP) spools of the engine, respectively. In generating mode of operation, the HP generator is in charge of generating all of the CVVF power, while the DC power demand is shared by both HP and LP generators. The proposed AC/DC hybrid generation architecture can supply CVVF power directly from one side of the generator winding terminals without external exciter, and generate DC power on the other side of the generator winding terminals through an inverter/rectifier unit.

As compared to the AC primary generation system in Fig. 1, the application of induction generator removes the external exciter, while the twin-spool twin-generator architecture improves the overall generation performance.

A more detailed electrical system configuration is shown in Fig. 4.2. An inverter/rectifier unit and frequency insensitive AC loads are connected to each end of the HP spool open-end winding induction generator terminals. An active rectifier unit is connected to the LP spool wye-connected induction generator. The DC output end of the inverter/rectifier unit and the active rectifier unit are paralleled to the DC bus.

DC power supply from the APU generation system or ground power supply is usually available for this process. As is shown in Fig. 4.3, in the engine starting mode of operation, the entire LP spool generation subsystem is deactivated.

Among the three generator parameters which have impact to the DC power output regulation precision of the HP spool generation subsystem, the stator resistance 𝑅𝑠1 and rotor leakage inductance 𝐿𝑙𝑟1 are relatively small, and contribute minor effect to the regulation robustness degradation. A parameter sensitivity test for DC power output in terms of HP generator stator resistance and rotor leakage inductance is performed using MATLAB. The results of the test are shown in Fig. below section.

This paper describes the simulation studies of a 3-Ø self-excited asynchronous generator (SEASG) fed RL load in conjunction with an AC/DC/AC converter fed series RLC circuit An attempt has been made to analyse the current, drawn by the rectifier circuit due to changes in the inverter frequency and their effects on the terminal voltage of the generator have been studied in open loop control. In this paper an induction generator based AC/DC hybrid generation system for MEA is presented. The application of induction generator addresses the problem of excessive fault current from generator terminals without external exciter. The Simulation results of AC/DC/AC converter for Induction generator is successfully done in Matlab Simulation, for different step

1. Haitham Abu-Rub, Mariusz Malinowski, Kamal Al-Haddad (2014). Power Electronics for Renewable Energy Systems, Transportation and Industrial Applications, NJ: Wiley, 2014 2. Lester Faleiro (2006). "Summary of the European Power Optimized Aircraft (POA) Paper," in 25th International Congress of the Aeronautical Sciences, ICAS 2006 3. B. Bhangu, K. Rajashekara (2014). ―Electric Starter Generators: Their Integration into Gas Turbine Engines," Industry Applications Magazine, IEEE, vol.20, no.2, pp.14-22, March-April 2014 4. K. Muehlbauer and D. Gerling (2010). "Two-generator-concepts for electric power generation in More Electric Aircraft Engine," 2010 XIX International Conference on Electrical Machines (ICEM), pp. 1-5 5. W. U. N. Fernando, M. Barnes, O. Marjanovic (2011). "Direct drive permanent magnet generator fed AC-DC active rectification and control for more-electric aircraft engines," Electric Power Applications, IET , vol.5, no.1, pp.14,27, January 2011 6. C.R. Avery, S.G. Burrow, P.H. Mellor (2007). "Electrical generation and distribution for the more electric aircraft," Universities Power Engineering Conference, 2007. UPEC 2007. 42nd International, vol., no., pp.1007, 1012, 4-6 Sept. 2007 7. M. J. Provost (2002). "The More Electric Aero-engine: a general overview from an engine manufacturer," Power Electronics, Machines and Drives, 2002. International Conference on (Conf. Publ. No. 487), pp. 246-251 8. G.A. Whyatt & L.A. Chick (2002). ―Electrical Generation for More-Electric Aircraft using Solid Oxide Fuel Cells,‖ Prepared for the U.S. Department of Energy under Contract DE-AC05-76RL01830 9. M. J. Cullen (2002). "Permanent Magnet Generator Options for the More Electric 10. W. Jiabin, K. Atallah, and D. Howe (2003). ―Optimal Torque Control of Fault-tolerant Permanent Magnet Brushless Machines," IEEE Transactions on Magnetics, vol. 39, pp. 2962 – 2964. 11. G. Jack, B. C. Mecrow and J. A. Haylock (1996). ―A Comparative Study of Permanent Magnet and Switched Reluctance Motors for High-Performance Fault-Tolerant Applications," IEEE Transactions on Industry Applications, vol. 32, pp. 889-895. 12. C. Mecrow, A. G. Jack, J. A. Haylock and J. Coles (1996). "Faulttolerant Permanent Magnet Machine Drives," IEE Proceedings Electric Power Applications, vol. 143, pp. 437-442.

PG Scholar, Electrical Department, Ganpat University, Mehsana, Gujarat, India