The following specification particularly describes the invention and the manner in which it is to be performed

INTRODUCTION: -

This invention relates to the field of Energy and Power Electronics. Still further this invention relates to Bidirectional DC-DC Converters which are also known as BDC’s. The BDC’s, allows the benefits in either increasing or decreasing the level of voltage between two DC sources along with the bidirectional power flow capability. BDC’s predominantly find their use in the field such as Hybrid Electric Vehicle (HEV), Uninterruptible Power Supply (UPS), Renewable Energy Systems (RES) and Fuel cell energy systems.

BACKGROUND OF INVENTION: -

It is well known that, the Commonly available renewable energy sources such as solar and wind energy system make them inappropriate to serve as a standalone system due to instability nature in the power generation. The only key to tackle this instability problem is to implement a common auxiliary storage device such as batteries or super-capacitors.

This type of energy storage will supply an uninterrupted power to the load connected to it. However, to accomplish the exchange of energy between the system and the auxiliary storage device, a DC-DC converter is required as a mediator. Therefore, it can be seen that a BDC should possess flexible control of bidirectional power flow in all the modes of operation. Thus, the modeling and the control of bidirectional DC-DC converters becomes an important issue. The basic demands of BDC in such an application require low output ripple, compact design of size and weight which in turn increase the converter efficiency. It is observed that most of the work carried out so far is mainly dealt with the performance of BDC in open loop mode and the major concern is associated with converter efficiency, inrush current, high output power and reverse recovery problem. Power converters are highly affected by various disturbances either from the devices attached to it or from a power source. These disturbances may cause damage to the system, if it is not controlled.

Thus, it can be seen that it is very essential to operate the converter in a closed loop mode irrespective of input and output disturbances, so as to maintain the output voltage at regulated level. Soft Computing Techniques (SCT) based controllers is proposed in this application for patent with the following core objectives of identifying the suitable controller with good regulation for BDC, and to obtain a reduced ripple content in the output voltage/current, and also, to improve the dynamic behavior of the converter.

OBJECT OF THE INVENTION

It is a principal object of the present invention is to identify the suitable controller with good regulation for BDC (Bi Directional DC- DC Converters)

It is yet another object of the present invention is to obtain a reduced ripple content in the output voltage/current.

It is still another object of the present invention is to improve the dynamic behavior of the converter.

DESCRIPTION OF THE INVENTION

Hence in order to meet the objective criteria, proposed controller techniques has been realized by using Non-isolated BDC using coupled inductor (NBDCCI). However, the performance of proposed converters is highly influenced due to the presence of ripples in the output. This can be reduced by implementing Quad filter at the output for the reduction of ripple content in BDC. From the analysis, it is evident that quad filter shows superior performance.

The objectives of this work are addressed in four phases of research work. Circuit models are developed for both boost and buck modes of all the three proposed modules. The first phase describes the performance of a novel NBDC with filters and controllers. The simulation results are verified with experimental results which ensure the effective performance of the proposed module with low ripple loss and improved efficiency. The second phase investigates the implementation of a high efficient NBDCCI. The results obtained from simulation and experiment could be validated so as to verify the effectiveness of the proposed converter.The third phase of research work presents the performance of IBDC and are measured by both experimental and simulation results. The fourth phase of research work is focused in the comparison of these proposed converters with RLE and Brushless Direct Current Motor (BLDCM) load through an inverter circuit. The comparison is done in terms of mechanical power output and Total Harmonic Distortion (THD). From the comparative study, it is clearly proven that performance of NBDCCI is good when compared with other two modules. NBDCCI fed BLDC drive system produces high mechanical output power of 586.3Watts with low THD of 32.45%. An experimental setup of the proposed NBDCCI with RLE load and quad filter is implemented to confirm its feasibility. The results obtained from both simulation and experiment could be validated so as to improve the performance of the proposed converter to a greater extent. Therefore, from all the conditions investigated, NBDCCI is identified as the most attractive module for HEV applications among the three proposed converters.

Description of the invention with reference to the Drawings

The structure of proposed NBDCCI is shown in Figure l.The configuration of the NBDCCI consists of two switches SI and S2 and has a coupled inductor whose winding turns remains the same in both sides. Switch S3 acts as synchronous rectifier.

During boost mode, the switching pulses generated by the PWM technique controls the action of the switches S I and S2 concurrently and the switch S3 acts as a synchronous rectifier. During buck mode, the switching pulses generated by the PWM technique controls the switch S3 and the switches S 1& S2 acts as synchronous rectifiers. Thus the NBDCCI converter has improved voltage gains in both buck/boost modes when compared with conventional bidirectional converter (Lung-Sheng et al. 2012). RESULTS AND DISCUSSION

The comparison of the response of proposed NBDCCI in boost mode with conventional and SCT based controllers are summarized in Table l.The comparison is done in terms of rise time, peak time, settling time and steady state error.

Table 1 NBDCCI: Comparison of responses with various controllers in boost mode

The comparison indicates that the response with neural controller is superior to that of fuzzy and other conventional controllers because the output power and voltage reaches steady state condition without any fluctuation.Thus, the choice of optimal control for the proposed converter operating in boost mode is chosen with neural controller.

While designing the bidirectional converters, the trustworthiness and efficiency of the converter plays a vital role. Thus the output power, THD and reduced torque ripple evaluations are carried out for comparison analysis of three topologies with RLE and BLDCM load. Table 2 presents the comparison of proposed modules with RLE load and the same using BLDCM load is given in Table 3. Table 2 Comparison of proposed converters using RLE load

Table 3 Comparison of proposed converters using BLDCM load

From table 2, it is found that NBDCCI using RLE load produces higher output power with low THD. From the table 3, it is observed that the torque ripple reduced is high in NBDCCI with BLDCM load and at the same time, THD is also low. This in turn increases the life time of the components present in the system. Figure 2, demonstrates the comparison of THD values of three proposed converters using RLE and BLDCM Load. From the Figure 2, it is evident that the proposed NBDCCI using both RLE and BLDCM load produces high mechanical output power with low THD comparatively than other two proposed modules. From the results, it is inferred that for all conditions investigated, NBDCCI provides high output power, less harmonic distortion and reduced torque ripple. At the same time, the speed of the motor is high when it is driven using NBDCCI. This in turn increases the efficiency of the system for all types of loads. Hence, it is concluded that the proposed NBDCCI converter is more suitable for HEV applications when compared to other two proposed modules.

Thus, the dynamic performance of these three modules over the classical converter is clearly demonstrated by both simulation and experiment. From the results, it is clearly proven that the performance of NBDCCI with both the loads is good when compared with other two modules. The THD of the system is very low and at the same time, the torque of 15.21Nm and mechanical output power of 586.3Watts are high. This in turn increases the life time of the components present in the system.

The motor drive should have high performance while designing for HEV applications. This can be achieved by implementing a BDC. The tasks have been completed in this work are listed as follows,

Three different types of bidirectional DC-DC converters (NBDC, NBDCCI and IBDC) have been analysed. Incorporated ZVS-PWM technique to reduce the ripple losses in the converter. Developed MATLAB simulink models for SCT based FLC and Neural controlled systems.

Developed MATLAB simulink models for FPID controlled systems.

Proposed NBDCCI for BLDCM drive.

Proposed HC in the converter to reduce output current ripple.

Therefore from the analysis, it is observed that NBDCCI is identified as the most attractive concept of the investigated converters. Hence, it is concluded that the proposed NBDCCI converter is more suitable for HEV applications when compared to other two proposed modules.

The proposed techniques discussed can be implemented in Microgrid systems. The investigations can be expanded by introducing advanced SCT based controllers for BLDC fed drive systems.

Research on the Power management strategy will be incorporated.