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Producing nine-level voltage waveform from a single-DC source and two DC capacitors while the capacitors are actively balanced

The challenge in power electronic converters

  • Voltage Source Inverters (VSIs) have become a dominant power electronics converter in various industrial applications such as those related to renewable energy, Uninterruptible Power Supply (UPS), electrical motor drives, Active Power Filter (APF), Power quality, Electric traction, Transportation and electrification, and High-Voltage Direct-Current (HVDC)
  • Certain designs of Multilevel Voltage Source Inverters (MVSIs) were developed by introducing three-level neutral-point-clamped (NPC) inverters
  • MVSIs are generally used in higher voltage and power applications, MVSIs use multiple semiconductor devices capable of dividing the DC voltage coming from DC sources or auxiliary capacitors to produce multiple voltage levels at the output terminal
  • Hybrid structures of MVSIs were also developed to increase number of voltage levels without reducing the number of components and some MVSIs require many additional components and present complex structures
  • The trade-off of increased output voltage levels for additional components and increased topology complexity is commonplace
  • Existing inverters necessitate additional switches and complex voltage balancing of auxiliary capacitors. Improvements are therefore needed

Design of multilevel voltage source converters

  • The invention is a novel single-DC source nine-level inverter topology called Packed E-Cell (PEC)
  • According to the PEC topology, the auxiliary capacitors are split using bidirectional switches to form the E-Cell and provide more paths to capacitors currents and voltages
  • There would be enough charging and discharging states for split capacitors that their voltages are actively balanced to determined level
  • Only one voltage sensor must be installed across DC-link to measure capacitors voltages
  • PEC is capable of continuing its operation with five-level output voltage while the capacitors voltages are balanced if a fault occurs on the bidirectional switches
  • PEC output voltage levels can be extended by horizontal and vertical expansion of the actual structure to reach N levels
  • PEC cell can be used in cascade configuration with other standard two, three and 5 level converters to multiply output voltage levels as well
  • PEC works as a bidirectional power flow converter by which both DC-AC and AC-DC conversion are operational
  • Therefore, PEC can be exploited as a converter with a high reliability to be used in both standalone and grid connected mode of operations
  • Technology developed by Kamal Al-Haddad and Mohammad Sharifzadeh at École de Technologie supérieure (ÉTS)

Competitive advantages

  • It requires single-DC source and it has single auxiliary DC-link
  • Only one sensor needs to be used to measure DC-link voltage. So, not only number of components is decreased but also there would be less complexity in control strategy or modulation technique
  • The capacitors voltages are actively balanced using redundant switching states, so no need for external controller or pre-charging conditions for capacitors
  • More voltage levels are produced while number of components is optimized
  • Two switches operate at the fundamental frequency, and the remaining operate at the switching frequency
  • Standalone/Grid-Tied modes of operations
  • Operation in mode rectifier and inverter
  • Topology can be easily extended to generate more output voltage levels
  • Can operate in remedial mode during faulty conditions
  • Multi output AC terminal is accessible for different multilevel voltage waveforms generations

Market applications

  • Uninterruptable power suppliers
  • Grid connect converter for solar energy
  • Electric drives
  • Small wind generators
  • PV systems
  • Microgrid systems
  • Electrification and transportation
  • Ozone production power supply
  • Battery chargers
  • High voltage generator
  • Large bandwidth instrumentation generator
  • LED high beam power supply
  • Electrical Vehicle

Business opportunity 


If you are interested by this technology, please contact :
Dareen Toumi, Technology Analyst & Business Development, Engineering
dtoumi@aligo.ca, (514) 618-9297


École de Technologie supérieure (ÉTS)

Main inventors


Kamal Al-Haddad, Professor, Department of Electrical Engineering

Prof. Al-Haddad received the B.Sc.A. and M.Sc.A. degrees from the University of Québec à Trois-Rivières, Canada, and the Ph.D. degree from the Institute National Polytechnique, Toulouse, France. He has been the holder of the senior Canada Research Chair in Electric Energy Conversion and Power Electronics since 2002. He successfully transferred 26 technologies to the Canadian industry since 1984. He is a Consultant and has established very solid link with many Canadian industries working in the field of power electronics, energy conversion, electric transportation, renewable energy, multilevel topologies, aeronautics, and telecommunications. He coauthored 720 transactions and conference papers, 6 patents, and two books. He has supervised 173 Ph.D. and M.Sc.A. students. Life fellow of the IEEE, a fellow of the Canadian Academy of Engineering, he received several prestigious international technical achievement awards, Prof. Al-Haddad is a member of the Academy of Sciences and fellow of the Royal Society of Canada.


Mohammad Sharifzadeh, Researcher, Department of Electrical Engineering

Mohammad Sharifzadeh received the B.Sc. and M.Sc. degrees in power electrical engineering from Babol Noshirvani University of Technology (NIT), Babol, Iran. He is currently pursuing his PhD in power electrical engineering at the École de Technologie Superieure (ÉTS), Montreal, Canada. His research interests include new multilevel converters topologies, PWM switching techniques particularly Selective Harmonic Elimination/Mitigation techniques, advanced control of multilevel inverters in grid connected applications, optimization methods applications in power system, machine learning applications for power electronic converters, smart power converter, Uninterruptible Power Supply (UPS), Modular Multilevel Converter (MMC) for HVDC applications, multilevel inverter for microgrid system, rectifier converters and battery chargers.

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