Feature

Research Focus: How does a new high gain dc-dc converter perform on a solar PV module?


Lopamudra Mitra, School of Electrical Engineering, KIIT University

A new Research paper accepted by the Journal presents a new prototype – a high-efficiency, high voltage gain DC-DC converter, which could be used with photovoltaic modules to increase output voltage in standalone or grid connected systems. In the study, a single switched high voltage gain DC-DC converter with a voltage gain of 10 is analysed, demonstrating low switching and conduction losses.

Title of Peer Reviewed and Accepted Research Paper

Author(s)

  • Lopamudra Mitra, School of Electrical Engineering, KIIT University
  • Ullash Kumar Rout, School of Electrical Engineering, KIIT University

What are the key findings of your research (in brief)?

It is common nowadays within Solar PV systems to use DC-DC converters that increase the input voltage. This research paper analyses the performance of a new high-gain converter, which allows direct connection to the grid through an inverter if the numbers of PV cells is high enough.

For this study we designed a complete system using the above-mentioned converter, a solar PV module and an MPPT tracker. We used three MPPT algorithms, and the modified Perturb & Observe (P&O) algorithm to provide the best performance result in the quickest time (the converter could be used with a standalone or a grid-connected PV system). It also provided high output voltage, which can be used with grid-connected systems through an inverter.

The converter analysed displayed the following advantages and features:

  • The voltage stress on the switch was found to be low for different power levels;
  • The input current was ripple free, meaning that a lower rating of switch could be selected for the PV module.

Can you give some broad, technical details?

This study used a new single switched high gain DC-DC converter within a PV system to convert low DC output voltage of the module into high DC output voltage.

The prototype converter in the study used a single switch, an inductor and a capacitor to transfer the inductive and capacitive energy simultaneously, achieving a high boost ratio. The voltage gain of the DC-DC converter was obtained as 10.

Most solar PV systems employ dc-dc converters such as boost converters that are used to increase input voltage. But for a boost converter to obtain a voltage gain of 10, the duty ratio has to be D=0.9. For an input voltage of 20V for example, if we want to achieve a voltage gain of 10 that is output voltage is 200V, the duty ratio has to be 0.9.
For the converter in the study, to obtain a voltage gain of 10 the duty cycle D is found to be 0.6. Considering an input voltage of 20V and output voltage of 200V, the duty cycle has to be 0.6. For D=0.8, the voltage gain is 20, with output voltage 400V. For D=0.7, voltage gain is 13.33 with output voltage 266.6V. For D=0.5, voltage gain is 8 with output voltage of 160V.

We also found that the converter displayed the following advantages and features:

  • The voltage stress on the switch was found to be low, within a voltage range of 50V to 110V for different power levels.
  • The converter had low turnoff current, and so we were able to reduce the switching losses in the experimental results.
  • The maximum voltage across the output diode was 350V for different input voltage and power levels.
  • As the input current was ripple free, this meant low conduction losses of the switch.

Why do these findings matter?

We consider these advantages to be important compared to many systems in operation today. Many topologies use transformers, and many switches have high-switching stress. The use of high frequency transformers for high voltage gain has some limitations, as parasitic capacitance can be a large source of loss within the transformer. When the switch turns on and off, the leakage inductance of a transformer often causes a sudden increase in voltage, which can get worse as operating voltage increases.

Voltage drops across leakage reactance often cause undesirable supply regulation with varying transformer load. Also, the amount of magnetic material cannot be reduced through higher operating frequency as there will be higher insulation requirements for higher-voltage applications.

Therefore, a transformer-less converter could be considered to avoid the difficulties experienced with a high voltage transformer.

Accessing the full text version of the paper
Performance analysis of a new high gain dc-dc converter interfaced with a Solar Photovoltaic module - Click here for full text access to the Paper, subscription or pay per view available.

About the Author:
Ms. Lopamudra Mitra is a Research Scholar in the School of Electrical Engineering, KIIT University, Bhubaneswar, India. She received her B.Tech in Electrical and Electronics Engineering from the National Institute of Science and Technology and M.Tech with specialization in Power Electronics and Drives from KIIT University, Bhubaneswar. Her research interests include Power Electronics, Renewable Energy Systems, Optimization Techniques and Power system.

 

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This article is featured in:
Energy efficiency  •  Energy infrastructure  •  Energy storage including Fuel cells  •  Photovoltaics (PV)  •  Policy, investment and markets  •  Solar electricity

 

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