__FTEEE-1641 A DC–DC Converter With High Voltage Gain and Two Input Boost Stages – IEEE EEE Project 2016 – 2017 __

__FTEEE-1641 A DC–DC Converter With High Voltage Gain and Two Input Boost Stages – IEEE EEE Project 2016 – 2017__

__ABSTRACT:__

__ABSTRACT:__

Two stage conversion systems (TSCSs) normally use either boost converter or high gain dc-dc converter along with dc-ac inverter in order to transfer power from low input voltage dc source to high voltage ac load. When these TSCSs operate at extremely low input voltages, the boost converter has to operate at extremely high duty ratios. This in turn results in more losses and reverse recovery problems. Usage of high gain dc-dc converter results in more number of components, increase in control complexity and decrease in reliability. Single stage conversion systems (SSCSs) are formed by merging both dc-dc and dc-ac conversion processes. These SSCSs have advantages like low loss, more compact and less reverse recovery problems. In this paper, a high gain coupled inductor based single-phase SSCS is presented. This SSCS topology has many desirable features such as high gain, less switching losses, free from leakage inductance adverse elects and compact. Principle of operation, steady state analysis and design of the proposed topology are described in detail. MATLAB Simulation results of the proposed topology and experimental results using DSP28335 based experimental setup are presented to validate the proposed scheme.

Output voltage from photovoltaic (PV) is dc, which depends on several factors like insolation, temper-nature etc. This voltage varies all the time depending upon the aforementioned factors. To deliver power to loads or grid from PV, a suitable power conversion system (PCS) is required. The PCS has to buck/boost the input voltage followed by dc-ac power conversion. This is a typical two stage power conversion system. Several two stage PCSs have been reviewed. Two stage PCS is a cascade connection of high gain dc-dc buck/boost converter and dc-ac inverter. This kind of PCS su_ers from several drawbacks like lower e_ciency, lower reliability, large size and higher cost, especially when it operates at low input voltages. Single-stage topologies combine the performance of each stage in multistage power converters, which in turn results in high e_ciency, more reliability and low cost.

A single stage high gain topology using coupled inductor is proposed. This converter scheme has several advantages like less number of components and high gain. Due to the leakage inductance associated with coupled inductor, the topology is suitable only for low power applications. Normally when coupled inductors are used in power converters, the leakage inductance with them causes several undesirable e_ects like high voltage stress and energy loss. Several converter topologies, which can mitigate the adverse e_ects of leakage inductance are proposed. The converter presented has several desirable features like less number of components, high gain and does not require any additional capacitors to trap leakage energy. Therefore, this topology is used as a part of single stage conversion scheme presented in this paper. A single stage high gain buck-boost inverter using a single coupled inductor is presented in this paper.

The proposed converter has following advantages: The topology gives high gain due to the use of coupled inductor, which makes this topology works better even in low input voltage conditions. Only one active switch out of operates at high frequency, thus its operation gives less switching loss. No bulky capacitors are required to capture leakage energy associated with the coupled inductor, which in turn results in compact size. The topology operation requires simple sinusoidal pulse width modulation (SPWM), hence avoids complex modulation techniques. As coupled inductor is used instead of two inductors, core requirements and space requirements will be reduced.

__STEPS:__

__STEPS:__

- Circuit Configuration and Working
- Mathematical Analysis
- Design of the Components
- Control Technique
- Simulation Studies
- Report Generation

**Circuit Configuration and Working***:*

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** **The proposed topology consists of active power switches, two passive power switches, an output capacitor and a coupled inductor. Out of _ve switches, only switch (Sp) operates at high frequency and remaining four switches operate at frequency of output voltage. Diode

(D1) is mainly intended for shorting inductor (L1) to the output voltage (vo) when the switch (Sp) gets turned o, in turn it avoids the adverse e_ects of leakage inductance associated with the coupled inductor. The operation of the proposed topology is same and symmetrical in each switching cycle of both the half cycles of output voltage. Therefore, only a switching cycle of positive half cycle of output voltage is considered for explanation. During positive half cycle of output voltage, switches (S2 and S4) are turned on and switches (S1 and S3) are turned o. Similarly, during negative half cycle of output voltage, switches (S1 and S3) are turned on and switches (S2 and S4) are turned.

**Mathematical Analysis:**

During each half cycle of output voltage, switch (Sp) operates with SPWM, ensuring transfer of power from input dc source to output ac load in each switching cycle. Several assumptions are made in order to explain the steady state operation of the proposed topology. These assumptions are: All parasitic components except leakage inductance of coupled inductor are neglected. The on-state resistance of the switches and forward voltage drop of the diodes are ignored. Capacitor (CL) is large enough to be consider it as a constant voltage source over a switching cycle. The topology is operating under continuous conduction mode (primary inductor current (iL1) is operating in continuous conduction mode).

**Design of the Components**

All parasitic components, on-state resistance of the active switches and forward voltage drop of the diodes are ignored. Leakage inductance of the coupled inductor is only considered in voltage gain calculation and in remaining parts, it is neglected in order to simplify calculations. Capacitor (CL) is large enough to be considered as constant voltage source over a switching cycle. Since, Mode 2 interval time is very less compared to switching period that can be discarded for calculating the voltage gain.

**Control Technique**

Double-loop control presented is used for controlling both output voltage and current in inductor (L1). Control block diagram of proposed converter. As per double loop control, voltage control loop (outer loop) for the proposed converter is derived. Similarly, current control loop (inner loop) for the proposed converter is derived. Here rL1 and rc are the equivalent series resistances associated with L1 and CL. In both simulation and experimental conditions, inner loop controllers are tuned for 4 kHz bandwidth with 600 phase margin and outer loop controllers are tuned for 2 kHz bandwidth with 600 phase margin.

**Simulation Studies***:*

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** **The Proposed 2kW converter topology is simulated using MATLAB/SIMULINK and the parameters. First, this proposed topology is tested with the resistive load mentioned, and corresponding results. Gating pulses for all the active switches. From the switching pulses, it is evident that only one switch (Sp) will be operated at higher frequency out of all switches. Input source current (iin), current through inductors (iL1 and iL2), and voltage across switch (vSp) are shown in Fig. 10b. As seen from Fig. 10b, all currents are varying in recited sinusoidal manner in each full cycle of output voltage. Input current (iin) and secondary inductor current (iL2) are always discontinuous. Primary inductor current (iL1) is combination of 50 Hz recited sine wave and high frequency (50 kHz) ripple, which can be evident. The waveform of voltage across switch (vSp) clearly indicates the alleviation of harmful elects of the leakage inductance associated with coupled inductor.

**Report Generation:**

A high gain single stage buck-boost dc-ac inverter topology is proposed. This topology has advantages such as high gain, low switching loss and compact in size. Operation principle of the proposed topology is explained with analytic details and complete design of the topology components is presented. From the mathematical analysis, it is observed that the topology provides high gain and performs dc-ac power conversion in single stage. This observation has con_rmed by detailed simulation and experimental studies. The detailed simulation and experimental results demonstrate the electiveness of topology in terms of high gain and free from harmful e_ects of leakage inductance. Due to these features the proposed topology with input side passive later can be used electively in transferring the power from applications like photovoltaic, where source output voltage (dc) varies with time.

__REFERENCE:__

__REFERENCE:__

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