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A REVIEW ON PERFORMANCE ANALYSIS OF BRIDGE TYPE DUAL INPUT CHOPPER
1SUPIYA DAS, 2SHAILENDRA VERMA
1,2Department of Electrical engineering, SSTC-FET, Bhilai, India
1[email protected], 2[email protected]
Abstract:- Two novel bridge type dual input dc_dc converter topologies are introduced for integrating two input energy sources The major advantages o f the improved converter as compared with the basic topology is capability to perform the buck, boost, and buck_boost modes of operation by using the same structures. The multi-port dc/dc converter is one of the common converters which are widely used in dc renewable energy sources. The multi- port Dc /dc converters are divided into three categories which are single-input multi- output, multiinput single- output, and multi-input multi-output converters in the structure of the electric power system of modern EVs/HVs systems, more than one of these units may be employed to improve the performance and efficiency; therefore utilization of a multi- input dc-dc converter is inevitable to obtain a regulated bus dc voltage. DC–DC converters with voltage boost capability widely used in a large number of power conversion applications in which fundamental energy storing elements (inductors and capacitors) and/or transformers in conjunction with switch(es) and diode(s) are utilized in the circuit.
In a microgrid sysem when a power electronic interface between the grid bus and the storage system, it detects mode of operation and provide seamless operation and the power flow in both directions.
Index Terms - Dual input bridge type dc-dc converters, multi-port dc/dc converter, renewable energy sources, bidirectional dc-dc converters.
1 INTRODUCTION In Hybrid Energy System (HES)
Conventionally single input DC-DC converters has been used to integrate multiple numbers of input sources .Multiple Input DC-DC Converter (MIC) has been developed to nullify the complexity, high cost, lower efficiency and dropping of compactness in high system.
The concept of Multiple Input DC-DC Converter (MIC) has been developed to
nullify these demerits. Comparatively simple and compact structure, lower part counts and higher efficiency are the potential merits of multiple input DC-DC converters (MICs). The isolated and non- isolated types of MIC are widely reported.
In isolated topologies, the presence of multi-winding transformers provides electrical isolation but increases the system complexity and cost compared to non-isolated topologies. Hence the use of non-isolated MIC is favored in the applications where efficiency and cost of the system are significant concerns. A non-isolated MIC for solar-PV application has drawback that it delivers power from one energy source at a time, and simultaneous power delivery from the input sources are not possible. In this paper, two dual input DC-DC converters are presented in which one converter is
the improved forms of the other converter.
The converters introduced have higher efficiency compared to other MICs.
DUAL INPUT DC-DC CONVERTERS:
The detailed description of both BDC and IBDC converters are illustrated.
NOMENCLATURE:-
Switching V1; V2 Source voltage 1, source voltage 2
VL,IL Inductor voltage and inductor current
I1; I2; I3 Average values of three source currents
d1; d2; d3 Duty ratios of switches S1, S2 and S3
dm Duty ratio of the mode selection switch
V0; I0 Converter output voltage and convertor output current
Vin Average value of input source voltages rL_ esr Equivalent series resistance of the inductor
rC_ esr Equivalent series resistance of the capacitor
L Inductance
T; fs Time period and frequency R Load Resistance
2 1.1 BRIDGE TYPE DUAL INPUT DC-DC
(BDC) CONVERTER
The circuit representation of BDC converter is shown in Fig. 1. Here, two
input energy sources, i.e., V1 and V2 are co the input sources and the load is managed by adjusting the duty ratios of power switches (S1, S2 and S3).
Fig. 1.circuit representation of BDC converter
Fig. 2. Different operating states of the BDC converter. (a) Source V1 charges the inductor.
(b) Source V2 charges the inductor. (c) Sources V1 and V2 together charge the inductor. (d) Freewheeling period of the load current
1.2 IMPROVED BRIDGE TYPE DUAL INPUT DC-DC (IBDC) CONVERTER
The IBDC converter contains four power switches (S1, S2, S3 and Sm) and two
diodes (D1 and D2). Diodes must be replaced by the power switches with anti- parallel diode to operate IBDC converter in the bidirectional mode.
Fig. 3. circuit representation of IBDC converter
TABLE : Possible operating states of IBDC converter in buck-boost operation
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Fig. 4. Different operating states of IBDC converter during buck-boost operation. (a) Contribution from source 1.(b) Contribution from source 2. (c) Contribution from both
sources V1 and V2 together. (d) Freewheeling period.
Fig. 5. Different operating states of IBDC converter during buck operation. (a) Source 1 charges the inductor and supplies the load. (b) Source 2 charges the inductor and supplies the load. (c) Source 1&2 together charge the inductor and supply the load. (d) Freewheeling
period.
2. CONTROL STRATEGY FOR IBDC CONVERTER
To resolve the power management problems in a MIC, an appropriate control strategy is necessary. The strategy is mainly dependent on the type of input energy sources connected where the dynamic and steady state response of the connected sources are different .therefore a power control algorithm which can consider the steady state and dynamic characteristics of each connected source would be a better choice for MIC
2.1 CONTROL STRATEGY BASED ON AVERAGE CURRENT MODE METHOD This control schemes includes either load side control or source side control. Under load side control, the current through the inductor is directly monitored and controlled to regulate the load voltage;
whereas in source side control, the inductor current is indirectly controlled by monitoring the respective source currents for the load condition given.
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Fig. 6. Control strategy for IBDC converter based on ACM control.
2.2 CONTROL STRATEGY BASED ON ONE CYCLE CONTROL METHOD
The One Cycle Control (OCC) method has been implemented for the proposed IBDC converter which is helpful for reducing the control complexity by avoiding the control loop interactions because it is a nonlinear control strategy, it takes the merits of nonlinear characteristics of power converters and provides instant dynamic control of the switched variable. Under this strategy, the average value of switched variable will reach a new steady state condition within one switching cycle followed by a transient condition.
Fig. 7. Control strategy of IBDC converter with OCC.
3 MICROGRID
A network of local electric power sources, energy storage units, power conversion systems, and communication systems is known as microgrid which operate in parallel with the utility grid (grid- connected mode) or independently as a stand-alone system (islanded mode).
Bidirectional power converters play a key role in interfacing DES units to the microgrid .which transfer power from the dc bus to the distributed energy storage (DES) unit during normal mode of
operation and transfer power from the DES unit to the dc bus when distributed energy resources (DERs) and utility grid are not available.
3.1 WORKING OF A MICROGRID
The grid connects homes, businesses and other buildings to central power sources, which allow us to use appliances, heating/cooling systems and electronics.
But this interconnectedness means that when part of the grid needs to be repaired, everyone is affected..This is where a microgrid can help. A microgrid generally operates while connected to the grid, but importantly, it can break off and operate on its own using local energy generation in times of crisis like storms or power outages, or for other reasons. A microgrid can be powered by distributed generators, batteries, and/or renewable resources like solar panels. Depending on how it’s fueled and how its requirements are managed, a micro-grid might run indefinitely.
4 BIDIRECTIONAL BUCK-BOOST DC- DC CONVERTER
This topology is able to step up or step down the voltage with power flow in both directions. The converter operates as a buck converter and charges the battery from the dc bus at a voltage VDC. During the charging mode.. During the discharging mode, the converter operates as a buck or boost converter to transfer power from the battery to the dc bus, depending on overvoltage or under voltage state of VDC. The bidirectional dc-dc converter interface has two main objectives: (a) To control the direction and amount of power to and from the storage device and (b) to control the dc link.
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Batteries are integral to maintaining the stability and reliability of the microgrid.
Fig. 8. Microgrid architecture scheme.
Fig. 9.Bidirectional Buck Boost DC-DC converter 5 FUTURE TRENDS
There is a major flaw in the proposed topology. Whenever switch S3 will conduct, it will short-circuit both the sources.
Hence huge short circuit current will flow in the circuit and damages the switches.
To overcome this problem, a modification in the topology will be proposed. The presented topology in working as dual input single output in the unidirectional mode of operation. It will be modified to the Bidirectional mode of operation. The presented topology is dual input and a single output. The modified topology will be able to operate as dual input single output and single input dual output. The presented work is implemented with the asymmetrical configuration of the voltage sources. In the modified work symmetrical and asymmetrical configuration of the voltage source can be taken. The presented topology is operating under the open loop. The modified topology can be operated under the closed loop.
6 CONCLUSION
Two DC-DC converters (BDC converter and IBDC converter) topologies are used .The IBDC converter which is derived from BDC converter has been carried out for three possible modes of operations such as buck, boost and buck-boost .By using the transient analysis of the converter the steady state and dynamic behavior of the IBDC converter are observed. Two control strategies (ACM and OCC) have been developed and regulation of the output voltage at the required value has been tested. The OCC method offers excellent dynamic response compared to the ACM method.. The BDC and IBDC converters have the compact structure and fewer components which increase their importance in micro grid
application. Some design
recommendations and future trends were presented in this paper .A better regulated output voltage is expected in future. Also the large-scale practical use of IBDC is expected. And in the future, the design and performance optimization of IBDC
6 based on advanced topology will be the trend.
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