ABSTRACT: A new soft switching circuit topology is derived from semi dual active bridge converter which is proposed for applications requiring only unidirectional power flow such as the dc–dc stage of a photovoltaic power converter, and battery charger for electric vehicles. The proposed converter consists of three ports,two bidirectional ports and one output port.It is similar to semi dual active bridge converter, no additional switches are used.The energy stored in the leakage inductance of the transformer is utilized to achieve zero-voltage switching for all the primary-side switches. The topology offers several other advantages including extended zero-voltage switching (ZVS), and smaller output filter requirement. MATLAB/SIMULINK is used for the system.
 F. Krismer, S. Round, and J. Kolar, “Performance optimization of a high current dual active bridge with a wide operating voltage range,” in IEEE Power Electronics Specialists Conference (PESC), 2006, pp. 1–7, Jun. 2006.  H. Qin and J. W. Kimball, “Ac-ac dual active bridge converter for solid state transformer,” in IEEE Energy Conversion Congress and Exposition (ECCE),2009, pp. 3039–3044, 2009.  Kheraluwala, M. N., Randal W. Gascoigne, Deepakraj M. Divan,
Solid state transformer is a high frequency transformer can be used as power electronic converter. The three stage SST configuration includes ac to dc rectifier, isolated dc to dc dual active bridge converter, dc to ac inverter. The switching frequency of inverter part is greater than DAB part so inverter stage is model for double line frequency i.e. at 120 Hz. The second harmonics are dominant at this frequency. For better performance of DAB converter PI control is used but at 120 Hz it has limited gain. To proposed methods are PI plus feed forward and PI plus Resonant controller.
ABSTRACT: The use of DC-DC Converters has been increased for high power applications i.e., power flow is from source to load. As per this conversion switch stress, voltage regulation, reliability, high efficiency, cost etc., comes into picture. However the converter with more reliability, less weight, less cost is much preferred.For power conversion applications requiring bidirectional power flow, the dual active bridge (DAB) is a preferred topology. S emi-dual active bridge (S-DAB) converter is obtained from Dual Active bridge converter (DAB) by replacing two switches(MOSFET or IGBT) to the two diodeson the load side. As the no of switches are less when compared to dual Active Bridge converter (DAB), it has high efficiency, unidirectional power flow and less stress on switches.Along with the above advantages it undergoes Zero Voltage Switching (ZVS) is achieved such that switching loss is less. This topology is for unidirectional power flow and its applications for photovoltaic power converter, battery charger for electrical vehicles. MATLAB Simulink of semi-dual active bridge converter is designed.
T HE global population without access to electricity exceeds 1.4 billion, whereas the rural electrification rate is below 65% . An estimated 171 TWh of off-grid electricity will need to be generated by 2030, which is equivalent to 100 GWp of pho- to photo voltaics (PVs) . The intermittent nature of PV and other renewable energy sources, and thus the need for energy storage and/or load shedding, is a major challenge in small- scale PV-based power grids. This is despite power quality requirements. Low-power dc–dc microconverters ,  and ac–dc microinverters (MIV) ,  provide high-granularity maxi- mum power point tracking (MPPT) ,  at the module or substring level. This leads to increased robustness to clouds, dirt, and aging effects, as well as irradiance and temperature gradients . A conventional MIV-based ac power system is shown in Fig. 1. The energy storage system (ESS), which is definitely required for islanded operation on the scale of one or more houses, for example, is usually based on a high-power centralized bidirectional ac–dc converter, which is interfaced to a battery bank or a flywheel , .
In Fig. 9 shows the block diagram of PI controller ,  is used to control the CFDAB converter. Open loop converter is the plant to be controlled and the reference input is the set point to control the output voltage. Difference between reference input and feedback signal is called as error signal . The output of the error is given to the PI Controller and then compared with repeating sequence of 100 kHz to generate the duty ratio of the primary active switches.
The PI controller is a basic controller which controls the duty cycle of the switches with a delay angle between the primary side converter and the secondary side converter. The other two controllers are advancements to the PI controller to make the output stable in a lesser time. A simple PI control diagram is shown below designed in MATLAB simulink.
The population without access to electricity globally exceeds1.4 billion, whereas the rural electrification rate is below 65%.The intermittent nature of PV and other renewable energy sources, and thus the need for energy storage and or load shedding, is a major challenge in small- scale PV-based power grids.[1,2,3]. This is despite power quality requirements. Low-power dc–dc micro converters and ac– dc (MIV) provide high-granularity maximum power point tracking (MPPT) at the module or substring level. This leads to increased robustness to clouds, dirt, and aging effects, as well as irradiance and temperature gradients. A conventional MIV-based ac power system with the energy storage system (ESS), which is definitely required for islanded operation on the scale of one or more houses, for example, is usually based on a high power centralized bidirectional ac–dc converter, which is interfaced to a battery bank or a flywheel is shown in fig 1 Existing MIV architectures satisfy the need for low capital cost and expandable ac generation, whereas there is a compelling argument to extend this technology to include small scale distributed storage. A novel topology with distributed storage is proposed for grid stabilization while potentially improving the generator lifetime and saving fuel. MIV integrated storage helps to buffer the frequent irradiance
Abstract— Three-phase Dual Active Bridge converter is advisable for the High-power DC-DC conversion system. In the ac link, galvanically isolated transformer operated at a medium frequency range provides stepping up or down of the secondary bridge voltage. This paper provides a magnetic design optimization of the medium frequency transformer for maximizing its efficiency when excited by a non-sinusoidal waveform. In this paper, a mathematical design of a 10kVA non-sinusoidal transformer had been developed and validated using two-dimensional (2D) transient finite element analysis (FEA). The set of selected design variables is defined in order to enhance the power density and efficiency of the targeted transformer and an optimization is carried out. Finally, a 10kVA transformer is prototyped and the results of core losses for non- sinusoidal excitation is confirmed experimentally.
transformer core and deteriorate the converter operation. The saturation may cause the non-zero average flux in the transformer core which gives DC offset to the converter AC waveforms . It can be overcome by controlling the DC offset to zero or designing the transformer at an appropriate operating flux density. Authors in  have demonstrated that this DC offset can be controlled by phase shift (PS) angle control. Another method to overcome DC offset is to connect two coupling capacitor in series with the primary and secondary windings  but this method uses additional passive device in the AC circuit which can cause additional failure to the converter. The authors in  also addressed the DAB converter performance when a fault happened in the switches. This type of fault in switches may either open or short the circuit. If short, the fault is going to be similar to pole to ground fault (unsymmetrical fault).
26 Read more
Abstract-- This work deals with design, modeling and simulation of the PI & the Fuzzy controlled DAB DC to DC converter systems. Open loop system is simulated with step change in input voltage. The output voltage in closed loop system is regulated using PI and Fuzzy controllers. The response of these two systems are compared. This converter has advantages like low EMI,less switching loss and improved dynamic response. The simulation results of PI & FLC DAB DC to DC converter systems are presented in this paper.
A bi-directional converter can move power in either direction, which is useful in applications requiring regenerative braking. In these DC to DC converters, energy is periodically stored into and released from a magnetic field in an inductor or a transformer, typically in the range from 300 KHz to 10 MHz By adjusting the duty cycle of the charging voltage (that is, the ratio of on/off time), the amount of power transferred can be controlled.Pulse-width modulation (PWM), or pulse-duration modulation (PDM), is commonly used technique for controlling power to inertial electrical devices, made practical by modern electronic power switches. The average value of voltage (and current) fed to the load is controlled by turning the switch between supply and load on and off at a fast pace. The longer the switch is on compared to the off periods, the higher the power supplied to the load.
efficiency than the F2F equivalent. This is because the semiconductor switches of the low-voltage side converter experience half the current stresses relative to that of an equivalent F2F connection (at a conversion ratio of 2). However, insertion of large number of FB cells in some of its arms in order to be able to cope with dc network faults at either dc side represents a limitation as it will jeopardize the high efficiency that could be achieved when only HB cells are employed. An additional problem of the asymmetric auto dc transformer in Fig. 12(b) is that it exposes both windings of the coupling transformers to high dc voltage stresses. This situation could be avoided should the auto dc transformer is rearranged to be symmetrical configuration so that both transformer windings avoid dc voltage stress. To support this discussion, the auto dc transformer of Fig. 12(b) is simulated using an average model, with the operating conditions shown in the caption of Fig. 13. Fig. 13 (a), (b) and (c) show current waveforms in the ac link and in the arms of the upper and lower converters of the auto dc transformer. The total power of 1400 MW is exchanged between the two dc sides, and the switching devices of the upper and lower converters experience equal current stresses (because V dc1 =2V dc2 ). Fig. 13 (d) and (e) show the dc link currents at the high and
26 Read more
To validate simulation results an experimental converter has been built and tested, as shown in Fig. 17. The power converters used for this experiment is one of the ‘off the shelf’ converters manufactured by SEMIKEON . These two-level converters have R-C snubbers and input and output common mode inductors. The converter also has onboard defined dead-time that varies from 4 – 4.1 μs along with propagation delay which varies from 0.1 to 0.2 μs and thus becomes very difficult to align the pulses for dead-time voltage spike removal algorithm. The power circuit of the experimental converter is shown in Fig.18. The system has been tested with an R-L load and the parameters are shown in table I. To demonstrate the behavior of the dual inverter system with predictive control, a demand reference current of 4Amps sinusoidal reference with a 50 Hz frequency was applied. The results are shown in Fig. 19 and can be
10 Read more
The above literature does not deal with reduction of Ripple in the output using a cascade filter. The above papers do not report closed loop controlled DAB Converter for fuel cell based systems. It is proposed to use cascade filter at the output to reduce the ripple. This work aims to control the closed loop systems using PI ( Proportional Integral) and Fuzzy logic controllers by using MATLAB simulation.
balance controller is also key except of important current controllers, and it is whether the performance of power balance controller is perfect or not that will have direct affect on control stability of two stage converters and power quality in both AC and DC sides. C oordinate transformation s of the sensed grid voltages and grid currents are made to implement decoupled control of P/Q, and the real-time active power and reactive power calculated by the instantaneous active and reactive power theory, together with the power references from grid, construct negative feedback control to implement direct power control.
The current-fed full-bridge boost converter with zero voltage switching is simulated using matlab simulink and implemented using 16F8778 microcontroller. With proper selection of phase shift angle ϕ and duty cycle D, the current fed dual active bridge converter can achieve high efficiency. Seven sub areas that can be obtained by combining the four operating mode symmetrically, out of these modes, mode 1 and mode 2 is more suitable for CF-DAB converter operation. In addition soft switching conditions and minimum RMS current is also achieved. Further, efficiency can also be improved by using higher variable dc link voltage corresponding to the input voltage.
Abstract—Multi-megawatt scale isolated DC-DC converters are likely to become increasingly popular as means to interconnect the MVDC grids of different voltage levels. Three- phase dual active bridge DC-DC (3DAB) converters operating with the zero-voltage switching (ZVS) is a promising candidate for the target multi-megawatt application. This paper presents a systematic approach of the design considerations for a 3DAB converter. Firstly, the use of snubber capacitors in medium voltage and medium frequency operating conditions is proposed. Snubber capacitor influence on turn-off current levels and ZVS operating range are introduced and analyzed. In addition, details of thermal management design are introduced. It is established through power loss analysis that the proposed design method reduces the semiconductor losses substantially at full load conditions. Finally, the proposed method has been validated from a 10kW simulation model using PLECS software package.
In  R. W. De Donker , D. M. Divan quoted on “A three-phase soft-switched high power density dc/dc converter for high power applications”, Three DC/DC converter topologies suitable for high-power-thickness high-power applications are introduced. Each of the three circuits work in a delicate exchanged way, making conceivable a diminishment in gadget exchanging misfortunes and an increment in exchanging recurrence. The three-stage double extension converter proposed is appeared to have the most positive attributes. This converter comprises of two three- stage inverter stages working in a high-recurrence six-stage mode. As opposed to existing single-stage AC-join DC/DC converters, lower turn-off top streams in the force gadgets and lower RMS current appraisals for both the info and yield channel capacitors are acquired. This is notwithstanding littler channel component values because of the higher- recurrence substance of the data and yield waveforms. Besides, the utilization of a three-stage symmetrical transformer rather than single-stage transformers and a superior usage of the accessible evident force of the transformer (as an outcome of the controlled yield inverter) altogether expand the force thickness feasible.
The proposed solid state transformer in the IEM is used to enable active management of DRER, DESD and loads, rather than a 60 Hz traditional transformer. The four-quadrant power flow control provided by the SST allows the plug-and-play of distributed generation and also allows for the addition of storages and loads to the grid with no adverse effects on nearby users. The SST will provide power quality improvement to residential users and industry customers. The FREEDM system understands the value of different types of energy and maximizes green energy utilization, which improves the energy efficiency of the total system.
174 Read more