Hardware Realization Of Single Stage Rectifier

Hardware Realization Of Single Stage Rectifier

Arun kumar.V

Electrical and Electronics Engineering Department (P.G)

Sri Ramakrishna Engineering College Coimbatore, India

Prof. D. Prakash Asst. Professor (SR.G)

Electrical and Electronics Engineering Department(U.G)

Sri Ramakrishna Engineering College Coimbatore, India

Dr.R.Mahalakshmi, Professor &Head

Electrical and Electronics Engineering, Sri Krishna College of Technology, Coimbatore, India

Abstract This paper describes a single stage AC-DC converter with high power factor. The diode-capacitor type of rectifier cause low power factor because of its nonlinearity. PFC serves to smooth out power drawn and regulates the output voltage. High power factor at the input is assured by operating the buck-boost converter at discontinuous conduction mode of operation. With same operation on both cycle and detailed designed circuit parameter, zero- voltage switching on all the active switches of the converter can be retained to achieve good efficiency. This gives soft switching condition which increases the efficiency of the system and reduces the switching power losses. The buck boost converter and the filter circuit are used to re-shape the input current waveform so as to be in phase with input voltage waveform. The design, analysis, simulation and hardware realization of the AC-DC converter with soft switching.

Keywords-Buck-boost converter, full-bridge resonant converter, power factor correction (PFC), zero-voltage switching(ZVS).

1. INTRODUCTION

   Power factor (PF) is the cosine of the angular difference between voltage and current. It is calculated as PF = cos = cos (Vs^Is). It can vary between zero and one depending on the type of load. If the supply voltage and current are in-phase with each other, then the power factor of the circuit (cos) is unity. The power electronic switching devices introduce distortion into the system. As a result, the power factor gets lowered.

   The diode bridge rectifier with capacitive filter is used as the fundamental block of many power electronics converters. Due to its non-linear nature, non-sinusoidal current is drawn

   from the utility and harmonics are injected into the utility lines. The injected current has lower order of harmonics and causes voltage distortion and poor power factor at input AC mains. This causes slow varying ripples at DC output load resulting in lower efficiency and larger size of AC and DC filters [2]. These converters are required to operate with high switching frequencies due to demand for small filter size and high power density. High-switching frequency operation results in higher switching losses, increased electromagnetic interference (EMI), noise and reduced converter efficiency [3]. To overcome these drawbacks, the switches of buck-boost converter are operated with zero voltage and zero current switching. High-switching frequency with SS provides low switching stress and losses, high-power density, less volume and lowered ratings for the components, high reliability and efficiency.

   To improve the efficiency, a large number of soft switching technique including resonant circuits have been proposed [4]- [7]. But these converters increase the number of switches and stages in power conversion circuit thus complicating the sequence of switching operation, excessive voltage and current stresses, and also narrower line and load ranges[8],[9].

   This paper describes a single stage AC-DC converter with high power factor. For high power application power handling capacity is increased so full bridge resonant converter is adopted which is combined with two Buck-boost type PFC circuits. Two active power switches act as a PFC circuits Therefore, power handing capacity increased. A high power factor at the input line is achieved by operating the PFCs at discontinuous conduction mode. The output voltage is regulated by controlling the ON/OFF time of switches present in buck-boost converter. The higher order harmonics are eliminated by using low pass filter, which reduce the size of filter and increases the power factor. Here soft switching can be obtained by using a new partial resonant converter. The higher order harmonics are eliminated by using low pass filter, which reduce the size of filter and increases the power factor.

   Here soft switching can be obtained by using a full bridge resonant converter. The proposed system has the advantage of less components and less switching losses.

2. PROPOSED CIRCUIT CONFIGURATION

   A single stage ac-dc converter is integrated with PFCs as

   gating signal are given to MOSFETs (M1 and M4) but there are still in off condition. The voltage in the reactive component L1 is equal to the line voltage. The inductor current Ip1 increases linearly from zero. Then M1 is turned on at zero voltage.

   D3 L2

   D1

   shown in the figure 1.The diodes (D9-D12) represents the intrinsic body diodes of the MOSFETs. A series resonant

   Pulse genertor

   L1

   M1 D9

   M3 D11 C3

   circuit and a transformer T1

   form the load resonant circuits.

   L4 C2

   (PFC1 and PFC2) to make the sine wave sinusoidal and inAC phase with the input line voltage. PFC1 and PFC2 operating simultaneously at both positive half cycle and negative half

   cycle of the input line. A small low pass filter is used to remove the high frequency component at the input.

   D3 L2

   C1

   Pulse

   D2 genertor

   L3

   D4

   T

   M2 D10

   C4

   M4 D12

   100mH

   D5 D6

   L1

   2.81mH

   AC 100 µF

   D1

   PULSE GENE RTOR 1

   C1

   PULSE GENE RTOR 2

   D2

   M1 M3

   C3

   C3

   100µF

   L4 C2

   2.81mH 100µF

   T

   C4

   100µF

   M2 M4

   B. MODE II

   D3

   D7 C5 D8

   LOAD

   L3 L2

   100mH

   D4 D1

   Pulse

   D11

   D5 D6

   C5

   Genertor

   L1

   M1 D9

   L4 C2

   M3 C3

   D7 D8

   100µF

   1µH

   AC C1 T

   LOAD

   Figure 1: Single stage high power factor converter

3. CIRCUIT OPERATION

There are four switches, namely M1., M2,M3,and M4 are

Pulse genertor

D2

L3

M2 D10

C4

M4 D12

controlled by four gating signals,namely,V

1,V 2,V

3, and D4

gs gs gs

D5 D6

Vgs4 respectively. Gating signal Vgs1and Vgs4 and gating signals Vgs2 and Vgs3 forms two voltage waveforms. The gated signals have equal and same waveform. M1 and M4 is turned on, M2 and M3 is turned off simultaneously and vice versa, each gated signals has a duty ratio of 0.5.

Since the circuit operates equally, the operation of the negative half cycle of the line voltage are equal to positive half cycle, except for inductor and power factor correction circuit

.Hence the circuit is analyzed for positive half cycle only. The circuit operation divided into seven modes of operation with respect to conducting switches. Each modes are explained below.

A. MODE I

This mode begins at when turning off the MOSFETs (M2 and M3), since the load current ir is negative at the switching off time. The diodes (D9 and D12) are forced to freewheel ir.The drain to sources voltage (Vds2 and Vds3) of M2 and M3 are combined to -0.7 v. The voltage across the resonant circuit is equal to dc-link voltage Vdc3 and Vdc4.After some time

D7 C5 D8

LOAD

During this mode, ir is still negative.small part of IP1 flow through M1, but it is equal to ir which flows to D12. This mode will end at when Ir passes zero and becomes positive,hen M4 turned on approximately at zero voltage

C. MODE III

D3 L2

E. MODE V

D3 L2

D1

Pulse genertor

M1 D9

D11

D1

D1

M3 C3

L1

L4 C2

Pulse

genertor

L1

M1 D9

M3 D11 C3

AC C1

T

Pulse

C4 AC

L4 C2

C1

T

D2 genertor

L3

M2 D10

M4 D12

Pulse

D2genertor

M2 D10

C4

M4 D12

D4 L3

D5 D6

D7 C5 D8

LOAD

D4

D5 D6

During this mode, M1 and M4 are kept at ON state. Since the line voltage keeps applying on inductor L1, ip1 increases continuously and flows through switch M1, current ir is positive and flows through switches M1 and M4.

D7 C5 D8

LOAD

When the rectified input voltage is at high level, the peak value of ip1 is high. On this condition, ir declines to zero before

D. MODE IV

D3 L2

D1

Pulse

genertor

D9 D11

M1 M3 C3

ip1 does. When ir resonates to pass zero, the circuit operation enters mode 5. At this instant, D2 and D 3 turn off naturally ,and M2 and M3 are turned on at nearly zero voltage to carry ir.

1. MODE VI

   When the rectified input voltage is at low level, the peak of ip1 is small and declines to zero before ir resonates to zero.

   L1

   L4 C2

   The circuit operation will enter mode 6 when ip1 decreases to zero. In this mode ends D3 is off and ir keep flowing through

   AC C1

   T

   D10 and D11. This mode ends at the time when ir resonates to zero. Then,M2 andM4 are turned at zero voltage to carry ir .

   C4

   Pulse

   D2genertor

   L3

   M2 D10 D3

   M4 D12

   L2

   D4

   D5 D6

   D1

   Pulse

   genertor

   L1

   D9

   M1 M3 C3

   L4 C2

   D7 C5 D8

   LOAD

   AC C1 T

   C4

   This mode begins when M1 and M4 are turned off. At the

   Pulse

   D2 genertor

   M2 D10

   M4 D12

   switching off instant ,ip1

   reaches its peak and ir

   is positive. L3

   Current ir will freewheel through D10 and D11 to charge the

   D4

   capacitor. Then diode D5 is reverse biased and ip1 will flow

   through diode D7 to charge the capacitor. The voltage across L1 is Vdc1, therefore,ip1 starts to decrease linearly.

   Since the peak of ip1 is proportional to the rectifier input voltage, the duration for ip1.

   D5 D6

   D7 C5 D8

   LOAD

   3

   4

   3

   4

2. MODE VII

   VOLTAGE (V)

   VOLTAGE (V)

   D3 1

   L2

   L1

   AC C1

   D1

   Pulse

   genertor

   D9

   M1 M3

   L4 C2

   T

   D11 C

   C

   0.5

   0

   0 1 2 3 4 5

   Pulse

   D2 genertor

   M2 D10

   M4 D12

   Time (S)

   Fig. 2 Gate pulses for switches M1 & M4

   x 10-4

   L3

   D4

   VOLTAGE(V)

   VOLTAGE(V)

   1

   1

   D5 D6

   C5

   D7 D8

   LOAD

   During this mode,ir is negative and flows through M2 and M3. The capacitor supply energy to the load resonant circuit, then both the switching devices are turned off.

   0.5

   0

   0 1 2 3 4 5

   IV. RESULTS

   The simulation result of proposed converter was analysed by MATLAB/Simulink Software. Fig. 1 shows the input voltage and current waveform of the proposed converter

   Voltage and Current waveform

   Voltage and Current waveform

   400

   200

   400

   output voltage (v)

   output voltage (v)

   300

   200

   100

   0

   Time(S)

   Fig. 3 Gate pulses for switches M2 & M3

   x 10-4

   0 0 5

   Time(s)

   10 15

   -200

   -400

   0 0.01 0.02 0.03 0.04 0.05

   Time(s)

   Fig. 1 Input voltage and current waveform

   Fig. 4 output voltage of the proposed converter

   Output Current(A)

   Output Current(A)

   1.5

   1

   0.5

   0

   -0.5

   0 5 10 15

   Time(s)

   Fig. 5 Output current of the proposed converter

   Fig. 1 shows the input voltage is sinusoidal and the input current is also in phase with each other and the power factor the proposed circuit is 0.99 for the given inductive load.

   Fig. 2 and Fig. 3 shows the gate pulses for the switches whenever the gate pulses is given switches will in the on condition whenever the gate pulses is not given the switches will in the off condition.

   Fig 4 shows the output voltage of the proposed converter. The output voltage of the proposed converter is 300V for the given switching sequence. The output voltage waveform stabilizes after 10 seconds

   Fig 5 shows the output current of the proposed converter.The output current of the proposed converter is 1A the output current waveform stabilizes after 10 seconds.

   Fig .6 Output voltage waveform

   Fig .6 shows the pratical output voltage waveform of the proposed converter for the given load

   1. CONCLUSION

      The power factor of the AC-DC converter has been improved by using power factor correction circuit and filter. In this project, comparative results of voltage regulation of AC- DC converter with load conditions and the power factor correction also realized in MATLAB environment. The switching power losses and stresses has been minimized due to soft switching technique.

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