double frequency buck converter ppt

04/07/2023 1EEE Dept: 'VJIT' Hyderabad

DOUBLE-FREQUENCY BUCK CONVERTER

PRESENTED BY

SAI SRINIVAS YASASWI 08911A0285SRAVAN KUMAR 08911A0296SANTHOSH 09915A0208


ABSTRACT

Improving the efficiency and dynamics of power converters is a concerned tradeoff in power electronics.

The increase of switching frequency can improve the dynamics of power converters, but the efficiency may be degraded.

A double-frequency (DF) buck converter is proposed to address this concern. This converter is comprised of two buck cells: one works at high frequency, and another works at low frequency


Chapter-1 (Introduction)

Chapter-2 (Basics of dc-dc converters)

Chapter-3 (Double Frequency Buck converter)

Chapter-4 (Simulation and Simulation result)

Chapter-5 (Conclusion and future work)

contents


Chapter-1 (Introduction)

The Demand of high-performance power converter is increased dramatically with the broadening of power converter’s application fields.

In order to improve the transient and steady state performance of power converters and to enhance power density, high switching frequency is an effective method


More ever to overcome this problems we are proposes a novel converter topology to achieve high dynamic response and high efficiency of buck-type converters.

This topology consists of a high-frequency buck cell and a low-frequency buck cell; and we call it the “double- frequency buck converter” (DF buck).


Overview of Project:

To enhance the steady-state response and the transient response of the buck converter, the switching frequency should be increased; but higher switching frequency steps up the switching loss dramatically. An CCS, which is in parallel with the load terminal, is added to tackle this loss problem


2.1 Introduction:

Chapter-2 (Basics of dc-dc converters)

A dc-to-dc converter is used to change the dc voltage from one level to another.

In this case, the dc input voltage is fixed and the level of the dc output voltage depends upon the converter’s topology.

The dc output voltage can be higher or lower than the input voltage since the advent of diodes; the techniques have been developed to obtain the dc voltage from the time-varying sinusoidal (ac) supply


Simple DC –DC Converter

Output voltage as a function of time


Types of DC to DC Converters:

Buck Converter

Boost Converter

Buck – Boost Converter

Cuk Converter


Buck converter:A buck converter is a step down dc-dc converter. Its design is similar to the step-up boost converter, and like the boost converter it is a switched-mode power supply that uses two switches (a transistor and a diode) and an inductor and a capacitor.

Buck Converter Operation:


Voltages & currents waveforms with time in an ideal Buck converter continuous mode


Discontinuous mode:


Average model of buck converter with the added CCS:The topology of a conventional buck converter In the steady state, the input (uin) and the output (uin) of the converter are governed by Uo = D · Uin

where D is the duty ratio


3.1 Introduction

Chapter-3 (Double Frequency Buck converter)

To enhance the steady-state response and the transient response of the buck converter, the switching frequency should be increased; but higher switching frequency steps up the switching loss dramatically.

For these purpose a novel converter topology used to achieve high dynamic response and high efficiency of buck-type converters.

This topology consists of a high-frequency buck cell and a low-frequency buck cell; and we call it the “double- frequency buck converter” (DF buck)


Proposed double frequency buck converter:


The cell containing L, S , and SD works at higher frequency, and is called the high-frequency buck cell.

Another cell containing La, Sa, and Da works at lower frequency, and is called the low-frequency buck cell.

The high frequency buck cell is used to enhance the output performance, and the low-frequency buck cell to improve the converter efficiency.


SWITCHING STATES

StateActive Switches

S Sa

a ON ON

b OFF ON

c ON OFF

d OFF OFF


State ‘a’ :Equivalent circuit of DF buck converter when s-on,sa=on

uL = Uin – U0

The governing equations of state’a’ are expressed as

uLa = 0


State ‘b’ :

The governing equations of state ‘b’ can be described by uL = -U0

uLa = Uin


State ‘c’ :

In state c, the equivalent circuit equations are derived as, uLa = - Uin uL = Uin – U0


State ‘d’ :

In state ‘d’, the equivalent circuit equations are derived as uL = - U0 ULa = 0


Voltage and current waveforms in one switching period Tsl.


Performance evaluation of double frequency buck converter:


Proposed double frequency buck converter fed with dc motor

Dc motor has good speed control response, wide speed control range.

It is widely used in speed control systems which need high control requirements, such as rolling mill, double-hulled tanker, and high precision digital tools.

When it needs control the speed step less and smoothness, the mostly used way is to adjust the armature voltage of motor.


Modeling of Buck-converter Dc Motor System:

This section provides a brief description on the modeling of the buck-converter driven dc motor,


PI controllers:

Chapter-4 (Simulation and Simulation result)

Proportional term: The proportional term makes a change to the output that is proportional to the current error value. The proportional response can be adjusted by multiplying the error by a constant Kp, called the proportional gain.The proportional term is given by: Pout = Kp e(t) Where•Pout : Proportional output•Kp : Proportional Gain, a tuning parameter


Integral term: The contribution from the integral term is proportional to both the magnitude of the error and the duration of the error. Summing the instantaneous error over time (integrating the error) gives the accumulated offset that should have been corrected previously

The integral term is given by: I out=K


Simulation result:steady state response:

DF

HF

LF

output voltage steady state response comparison of the double frequency, single high and low frequency buck converter.


transient response when load is step up:

Hf

Lf

fig:Output voltage transient response comparison on of the double frequency, single high and low frequency buck converter when load is step up

Df


Transient response when load is step down:

Hf

Lf

Fig 5.3.2.(c): output voltage transient response comparison of the double frequency, single high and low frequency buck converter when load is step down

Df


Df

Hf

Lf

step change waveforms

Fig step change waveforms of the double frequency buck converter, single high frequency, and low frequency buck converter.


S

Sa

Sd

switching states of the switches(S, Sd, Sa)

Fig switching states of the high frequency buck cell switches(S, Sd),and low frequency switch Sa of the double frequency buck converter


Simulation result for double frequency buck converter fed with dc motor

Fig : Double frequency buck converter fed with dc motor output armature current ,eletromagentic torque ,speed wave forms


Double frequency buck converter not only exhibits the same steady state and transient performance but also improves the efficiency of conventional buck converter

The Double frequency buck converter does not need the load transient change information for accurate current control and does not have the current circulating problem

The proposed converter greatly improves the efficiency and exhibits nearly the same dynamics as the conventional high-frequency buck converter and efficiency of the double frequency converter is nearer to the low frequency buck converter.

Conclusion


Future work will investigate whether the proposed buck converter is applicable for high current or high dynamics specifications.

Scope of the future work:


THANK “U” ?????

double frequency buck converter ppt

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