Dr Hans Bleijs
Hans (J.A.M.) Bleijs
Lecturer in Electrical Engineering
Electrical Power and Power Electronics Research Group
MSc (Eindhoven), PhD (London), DIC, CEng, MIET, MIEEE
T: +44 (0)116 252 2553
F: +44 (0)116 252 2619
Location: Room 705, Engineering Tower
Hans Bleijs was born in Eindhoven, The Netherlands, and educated at the Van der Putt Lyceum . After a part-time university study, during which he also held appointments at the Philips' Research Laboratories, the University of Zambia and the University of Dar es Salaam (Tanzania), he was awarded the Ir. (MSc) degree in Electrical Engineering from Eindhoven University of Technology in 1982.
In 1983 he started as a Research Associate at Imperial College, University of London, to work on the development of integrated wind/diesel systems, for which he was based at the Rutherford Appleton Laboratory from 1985 to 1991. He was awarded a PhD degree from Imperial College in 1990. In 1991 he was appointed as a Lecturer in Electrical Engineering at the University of Leicester with special emphasis on research in Renewable Energy.
Main Research Interests:
For the last twenty-five years Dr Bleijs' research has focused on electricity generation from renewable energy sources, such as wind power and solar radiation. This involves theoretical as well as experimental work on electrical machines, power electronics, power systems and control. Initially this work concentrated on constant-speed wind turbines with synchronous and induction generators, connected to weak grids or stand-alone diesel generators. Of particular interest is the voltage and frequency control and stability of wind-diesel systems. Due to the variability of the wind such systems greatly benefit from energy storage, and various storage mediums have been investigated for this purpose. Initially, this concentrated on flywheels, mechanically linked to the diesel generator or connected to the system through power-electronic variable speed drives or continuously variable transmissions (CVT). Both current-source and voltage source inverters have been tested for flywheel drives. Using back-to-back voltage source inverters with vector control and dedicated power controllers, fast and accurate control of active and reactive power flow has been achieved. A related area is variable speed operation of wind turbines and diesel generators for improved efficiency and low-load operation in wind-diesel systems. Wind power smoothing for stand-alone applications has also been investigated using hydrogen electrolysis and storage.
More recently, his research interest has extended to photovoltaic (PV) systems for converting solar radiation into electricity. This involves new topologies for power-electronic converters as well as advanced control algorithms for tracking the maximum power point (MPP) of PV panels and arrays. This is particular important under rapidly changing environmental conditions and partially shaded operation.
A novel PV/grid interface for medium and large-scale systems has been developed that comprises modular low-voltage current-fed dc-dc converters, a common high-voltage dc bus and an industrial 3-phase inverter with adjustable power factor and grid supervision. Each converter contains a fast and accurate MPP tracker and the system control includes power feedforward to the inverter to minimise dc bus voltage fluctuations. Excellent MPP tracking over a wide input voltage range has been demonstrated.
Fig 1: Laboratory set-up of a modular PV/grid interface: grid inverter (l) two dc/dc converter modules (c) and two dc maximum power point sources (r)
Recent and Current Research Projects:
As part of the PV research two systems have recently been installed on University campus buildings. The first system, designed and part-funded under the EU UNIVERSOL project, is a 11 kWp research and demonstration PV system installed on an adjacent laboratory roof, comprising 64 mono-crystalline panels, flexibly arranged into 7 sub-arrays of different sizes and topologies. This system is instrumented extensively to monitor electrical and environmental variables using a dedicated data acquisition and data storage system. The second PV system of 38 kWp is integrated in the new part of the Main Library building, and uses 3 different silicon PV cell technologies (mono- and poly-crystalline and amorphous thin-film) for different locations on the building. This system, funded by a government grant and a donation from a local charity, is also being monitored to analyse the performance of each technology in each position.
Under varying irradiance conditions fast and accurate MPP tracking is required to maximise solar energy conversion. However, studies based on numerical models of PV cells and
converters have shown that fast response tracking algorithms may operate in limit cycles around the MPP or even divert from it under certain conditions if the inherent capacitance of the cells is not taken into account. Similarly, partial shading of PV panels or arrays may result in operation on a local maximum away from the MPP. Advanced tracking algorithms are under development that can recognise such conditions and ensure true MPP operation. Such algorithms are being implemented in a DSP controller and will be tested using existing converters in conjunction with a newly developed flexible solar emulator.
Fig 2: Research and demonstration PV system on roof of Concrete Laboratory next to the Engineering Building
In hot climates the increased demand for space and produce cooling is directly correlated to the prevailing solar irradiance. PV power generation can make a substantial contribution in meeting this demand. At the same time PV inverters can be exploited to maintain the desired voltage profile in the local distribution system through reactive power control. Power flow programs will be applied to find the most appropriate control algorithms to guarantee a stable voltage platform. In conjunction with Dr Lefley the use of hydrogen fuel cells for vehicle propulsion is also under investigation.
• J.A.M. Bleijs: 'Wind turbine dynamic response – difference between connection to large utility network and isolated diesel micro-grid'. IET Renewable Power Generation, Vol.1, Issue 2, June 2007, pp.95-106
• Y. Liu & J.A.M. Bleijs: ‘Dynamic Effect of PV Cell Capacitance on MPPT algorithms’. Proc 21st European Photovoltaic Conference, Dresden, 4-8 Sept 2006, pp. 2604-7
• J.A.M. Bleijs & A.D. Simmons: ‘Flexible PV Demonstration and Research System at the University of Leicester: Performance and Modelling’. Proc 20th European Photovoltaic Conference, Barcelona, 6-10 June 2005, pp. 2705-8
• J.A.M. Bleijs: ‘Continuous Conduction Mode Operation of the Three-Phase Diode Bridge Rectifier with Constant Load Voltage’. IEE Proc on Electric Power Applications, Vol.152, No. 2, March 2005, pp.359-68
• X-G. Yan, C. Edwards, S. K. Surgeon & J.A.M. Bleijs: ‘Decentralized Sliding Mode Control for Multimachine Power Systems Using Only Output Information’. IEE Proc on Control Theory Applications, Vol.151, No.5, Sept 2004, pp.627-36
• J A M Bleijs & J A Gow: ‘Fast Maximum Power Point Control of Current-Fed DC-DC Converter for Photovoltaic Arrays’. IEE Electronics Letters, 37, no.1, pp. 5-6, Jan. 2001
• J A Gow & J A M Bleijs: ‘Optimization of a Utility Interface for Large-Scale Photovoltaic Power Systems’. Proc EPE2001 Conference, Graz, Austria, 27-29 Aug 2001
• J A M Bleijs, F Hardan & A J Ruddell: ‘Flywheel Energy Storage System for Wind Power Smoothing in Weak and Autonomous Networks’. Proc ‘Wind Power for the 21st Century’ Conference, Kassel, Germany, Sept 2000, pp.270- 273