Design of High Gain Switched Capacitor Z-Source Converter with

Extended SC Cells

Kaveri Sanjeevreddy

1 a

and M. S. Aspalli

1 b

Department

of Electrical and Electronics Engineering (Affiliated to VTU Belgaum)

Poojya Doddappa Appa College of Engineering, Kalaburagi (Affiliated to VTU Belgaum), Karnataka, India

Keywords: Z Source Converter, Switched Capacitor Converter, High Gain Converter, Voltage Stress.

Abstract: In this paper, a switched capacitor-based z source converter is proposed and extended with switched capacitor

cells to further improve the voltage conversion ratio(1). The proposed converter minimizes the stress of the

power electronic switches and diodes less than that of half the load voltage and provides a high voltage

conversion ratio unaccompanied by any changes in the duty ratio and also minimizing the requirement of

passive or active components. The modes of operation of the converter is analysed and comparison of

proposed converter with similar structures of dc-dc converters are provided. The simulation work is carried

out in MATLAB/Simulink software. A hardware model is developed and the performance of the converter is

validated.

1 INTRODUCTION

Recently, greater focus has been placed on the

technological advancement of renewable energy

generation, such as Solar and wind energy. The low

voltage output of the solar panels is one of the primary

limitations of PV generating. To increase the Solar

panel voltage to values like 400 V in order to fulfil the

DC MG's voltage requirements, a converter with a

large voltage conversion ratio is needed. The PV

voltage can be increased using two usual methods:

pairing solar panels in series, or using a standard boost

converter. Because the entire system is affected if one

of the solar panels fails, the series connection is

unreliable. The typical boost converter offers

extremely high duty cycle and great voltage gain.

However, it frequently has serious output diode

reverse-recovery issues, low efficiency, and excessive

stress from voltage over the power electronic switches

and output diode. In order to increase the PV voltage

and get around the issues that the serial arrangement

of solar panels and the traditional boost converter

present, sophisticated high boost DC-DC converters

are being investigated (Habibi, S,2021). Due to the

extensive use of components,

________________________________

https://orcid.org/ 0009-0004-0499-2075

https://orcid.org/ 0000-0002-5483-6415

architectures constructed around SL and SC modules

are both expensive and complex. With a converter

constructed using coupled inductor or built in

transformer to hold onto the energy from inductance

leakage and lessen the strain caused by voltage across

the power switches, a clamping circuitry is necessary.

Recently, the idea of increasing voltage through quasi-

source (qZS) and Z-source (ZS)converter topologies

are being used. The voltage conversion ratio for

traditional ZS and (qZS) topologies, however, is

insufficient. A novel of higher boosting ZS converters

was created by integrating the SL technique into

traditional ZS network and was utilised as an input

phase of a two stage, 3ф Z-Source inverter. There are

many components and a duty cycle limit of 0.33, a

value below the threshold of 0.5 for the traditional ZS

topology, despite the voltage conversion ratio being

raised and voltage is contrasted to the traditional

similar topologies. The inclusion of the SC cells and

the traditional (qZS) network produced a novel

converter with a high voltage conversion ratio and

minimal voltage strain on the semiconductors

(Rahimi,2020).

In this paper, a new structure of Z Source converter

(Naser Vosoughi Kurdkandi,2020) is designed by the

integration of switched capacitor cells to the

traditional Z source impedance network, in order to

achieve high voltage conversion with reduced switch

voltage stress and minimum number of passive

components(Hu, X et al.,2020). The proposed

Sanjeevreddy, K. and Aspalli, M.

Design of High Gain Switched Capacitor Z-Source Converter with Extended SC Cells.

DOI: 10.5220/0012505900003808

Paper published under CC license (CC BY-NC-ND 4.0)

In Proceedings of the 1st International Conference on Intelligent and Sustainable Power and Energy Systems (ISPES 2023), pages 32-37

ISBN: 978-989-758-689-7

converter topology eliminates the limitations on the

duty ratio. It is further extended by introducing the

switched capacitor cells controlled by an auxiliary

switch which further improves the voltage conversion

ratio without adding to the voltage stress.

2 SYSTEM DESCRIPTION

The proposed system is provided below in Fig 1.

Figure 1: Proposed system Block diagram.

The DC voltage source is connected to the

proposed converter which provides boosted voltage to

the load based on the pulse provided by the pulse

generation unit. The proposed converter is of two parts

switched capacitor-based Z Source converter and

extended SC cells so that the voltage conversion ratio

is improved.

The ZS DC-DC converter below is comprised of

single mosfet S with inductors (L1, L2), diodes (D1,

D2, D3, D4) and capacitors (C1, C2, C3, C4, Co). The

traditional ZS impedance network is coupled with

switched capacitor cells, a new impedance converter

is designed (SC-ZS converter) which possess a

symmetrical composition, improves the voltage

conversion ratio and also minimizes the switch

voltage stress across the diodes and power electronic

switch.

Figure 2: SC-ZS converter.

The operational stages of the above-mentioned

converter is provided below:

Stage 1:

When the switch is ON, the capacitors C1 and C2 are

discharging along with inductors L1 and L2. The

capacitors C3 and C4 are charging. The output

capacitance Co provides energy to the load.

Figure 2(a): Stage 1 operational circuit of SC-ZS converter.

Stage 2:

When the switch is OFF, the capacitors C1 and C2 are

charging along with inductors L1 and L2. The

capacitors C3 and C4 are discharging provides supply

to the load.

Figure 2(b): Stage 2 operational circuit of SC-ZS converter.

The voltage conversion ratio G is:

The voltage across the power electronic switch S and

diodes D1-D4 are calculated as:

Extended Switched Capacitor cell:

Design of High Gain Switched Capacitor Z-Source Converter with Extended SC Cells

It is further extended by adding switched capacitor cell

with auxiliary switch to improve the voltage

conversion ratio without increasing the stress on the

diodes and power electronic switches.

Figure 3: Improved SC-ZS converter with extended SC

cells.

The operation of this proposed converter is same as

conventional SC-ZS converter for modes 1 and 2.

Stage 3:

In this, the capacitor C2 and C2’ are used to improve

the voltage conversion ratio. When the switch Sa is

ON, the C1 discharges and charges capacitor C2’

through the diode Do2. Diode Do2’ is reverse biased

where Do2 conducts.

Figure 3(a) Stage 3: operational circuit of proposed

converter.

Stage 4:

When the switch Sa is OFF, C2’ discharge and

provides energy to load along with C1 and C2. The

diodes Do1 and Do2 are reverse biased where Do2’

conducts.

Figure 3(b) Stage 4: operational circuit of proposed

converter.

3 SIMULATION SETUP &

RESULTS

The simulation parameters for the proposed converter

are shown below in Table 1.

Table 1: Simulation Parameters.

Input Voltage

12 V

Input power

450W

Switching Frequency

5 KHZ

Inductor

91.1mH

SC cell Capacitor

56µF

Output Capacitor

20mF

Load voltage

220V

Load Resistance

100 ohm

The simulation circuit of the high gain voltage

converter is provided below:

Figure 4: Simulation circuit of SC-ZS converter.

In this, the input voltage is provided as 12V and the

output voltage is designed for 220V. The duty ratio is

around 0.44 for gating pulse of 5KHz switching

frequency. The waveforms of the load voltage and

current is shown below:

Figure 5: Simulation Waveforms of load voltage and current

of SC-ZS converter.

ISPES 2023 - International Conference on Intelligent and Sustainable Power and Energy Systems

The load voltage is around 220V and current is 2A.

The switching gate pulse and the switch voltage stress

is provided below:

Figure 6: Gate Pulse and voltage waveforms of SC-ZS

converter.

The switch voltage is calculated as 104V and here

we achieve the switch voltage around 104.5V in

simulation of the high gain converter. The efficiency

of power curves of the converter is provided below:

Figure 7: Input Power, Load Power and %Efficiency

waveforms of SC-ZS converter.

Figure 8: Simulation circuit of the SC-ZS converter with

extended SC cells.

The input power is around 447W and load power

is around 415W with efficiency as 93.65%. The

extended cell is added to the high gain converter and

is given in figure 8.

In this, a switched capacitor cell is connected

along with the high gain converter and provides

supply to the load. The waveforms of load voltage and

current of the proposed converter is provided in

figure.9 The load voltage is around 275V and load

current is 2.6A for the same duty ratio of 0.44. The

voltage conversion ratio is further improved by 1.25

times than that of converter without extended

switched capacitor cell.

Figure 9: Simulation waveforms of Load voltage and current

of SC-ZS converter with extended SC cells.

Design of High Gain Switched Capacitor Z-Source Converter with Extended SC Cells

The efficiency of power curves of the converter is

provided below:

Figure 10: Input Power, Load Power and %Efficiency

waveforms of SC-ZS converter.

The input power is around 745W and load power

is around 700W with efficiency as 93.1%.

A hardware prototype model of proposed

converter with input voltage of 12V is developed with

output voltage of 220V with load resistance of 1KΩ.

The hardware parameters is provided below in the

following Table 2.

Table 2: Hardware Parameters.

Arduino uno control is used for generating the

pulses for the proposed converter and it is provided to

driver circuit (TLP 250) in order to drive the mosfets

IRF 250.

The load voltage is provided below:

Figure 11: The load voltage of the proposed converter is

around 240V with 100V/div in the above waveform.

Figure 12: Hardware Setup of proposed system.

4 CONCLUSIONS

In this paper, switched capacitor based z source

converter is designed and the operational modes of the

converter was analysed with extended switched

capacitor cells. The voltage stress of the switch was

calculated and verified with the simulation results.

The voltage conversion ratio of sc-zs converter was

18.33 and further improved by 1.25 times by adding

switched capacitor cells without any changes in duty

ratio. The efficiency of the proposed converter is

measured as 93.1% for the input power of 750W and

load of 100 ohm. A hardware prototype model was

developed and the operation of the proposed converter

is verified with the results.The main advantages and

applications of this proposed converter are, the

voltage gain can be increased without increasing the

pulse width and hence the voltage stress is kept lower.

ISPES 2023 - International Conference on Intelligent and Sustainable Power and Energy Systems

The voltage gain can be further extended by increasing

the switched capacitor cells compared to the literature

and It can be used for battery charging applications,

dc drives, renewable energy.

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Design of High Gain Switched Capacitor Z-Source Converter with Extended SC Cells