• Active Power and DC Voltage Coordinative Control for Cascaded DC–AC Converter With Bidirectional Power Application

      Tian, Yanjun; Chen, Zhe; Deng, Fujin; Sun, Xiaofeng; Hu, Yanting; University of Chester (IEEE, 2015-10-31)
      Two stage-cascaded converters are widely used in dc–ac hybrid systems to achieve the bidirectional power transmission. The topology of dual active bridge cascaded with inverter DABCI) is commonly used in this application. This paper proposes a coordinative control method for DABCI and it is able to reduce the dc-link voltage fluctuation between the DAB and inverter, then reduce the stress on the switching devices, as well as improve the system dynamic performance. In the proposed control method, the DAB and inverter are coordinated to control the dc-link voltage and the power, and this responsibility sharing control can effectively suppress the impact of the power variation on the dc-link voltage, without sacrificing stability. The proposed control method is also effective for DABCI in unidirectional power transmission. The effectiveness of the propose control has been validated by both simulations and experiments.
    • Comparing Terahertz transmission response on pH-dependent apomyoglobin proteins dynamics with circular dichroism

      Qiu, Junyi; Yang, Bin; Sushko, Oleksandr; Pikersgill, Richard W.; Donnan, Robert S.; University of Chester (IEEE, 2014-12-08)
      Terahertz time domain spectroscopy (THz-TDS) was used to study the transmission responses of pH-dependent apomyoglobin (ApoMb) dissolved solutions in 0.2-2.2 THz frequency domain, the THz-TDS technique was also benchmarked against circular dichroism (CD) by studying pH-related folding states changes of ApoMb protein. Results revealed that differences of pH-dependent ApoMb/water dynamics can be detected directly by the THz refractive index spectrum, and these differences are further proved to be caused mainly the effect of protonation of water and possibly water response leaded by protein conformation change.
    • DC-Link Voltage Coordinated-Proportional Control for Cascaded Converter with Zero Steady-State Error and Reduced System Type

      Tian, Yanjun; Loh, Poh C.; Deng, Fujin; Chen, Zhe; Hu, Yanting; 1. Department of Energy Technology, Aalborg University, Denmark; 2. Faculty of Science and Engineering, University of Chester, UK (IEEE, 2015-06-11)
      Cascaded converter is formed by connecting two sub-converters together, sharing a common intermediate DC-link voltage. Regulation of this DC-link voltage is frequently realized with a Proportional-Integral (PI) controller, whose high gain at DC helps to force a zero steady-state tracking error. Such precise tracking is however at the expense of increasing the system type, caused by the extra pole at the origin introduced by the PI controller. The overall system may hence be tougher to control. To reduce the system type while preserving precise DC-link voltage tracking, this paper proposes a coordinated control scheme for the cascaded converter, which uses only a proportional DC-link voltage regulator. The resulting converter is thus dynamically faster, and when compared with the conventional PI-controlled converter, it is less affected by impedance interaction between its two sub-converters. The proposed scheme can be used with either unidirectional or bidirectional power flow, and has been verified by simulation and experimental results presented in the paper.
    • Design and specification of building integrated DC electricity networks

      Stewart, M.; Counsell, John M.; Al-Khaykan, A.; University of Chester (IEEE, 2017-01-19)
      Adoption of millions of small energy efficient, low power digital and DC appliances at home and at work is resulting in a significant and fast growing fraction of a building's electricity actually consumed in low voltage DC form. Building integrated energy systems featuring renewable photovoltaics are also increasingly attractive as part of an overall electricity and emissions reduction strategy. This paper details design and specification of a novel system level method of matching building integrated photovoltaic electricity generation with local low voltage DC appliances in office and other ICT intensive environments such as schools. The chosen scenario considers load components consisting of a diverse range of modern low power ICT and DC appliances, networked and powered by industry certified smart DC distribution technologies. Energy supply to the converged DC, IT and ICT network is described as featuring a roof-mounted or other on-site photovoltaic array in combination with conventional supply from the local grid infrastructure. The direct and strategic benefits of smart DC infrastructures are highlighted as the enabling technology for optimal demand reduction through fully integrated energy management of DC systems in buildings.
    • Impedance coordinative control for cascaded converter in bidirectional application

      Tian, Yanjun; Deng, Fujin; Chen, Zhe; Sun, Xiaofeng; Hu, Yanting; University of Chester (IEEE, 2015-06-30)
      Two stage cascaded converters are widely used in bidirectional applications, but the negative impedance may cause system instability. Actually the impedance interaction is much different between forward power flow and reversed power flow, which will introduce more uncertainty to the system stability. This paper proposes a control method for the constant power controlled converter in cascaded system, and consequently it can change the negative impedance of constant power converter into resistive impedance, which will improve the cascaded system stability, as well as merge the impedance difference between forward and reversed power flow. This paper addresses the analysis with the topology of cascaded dual-active-bridge converter (DAB) with inverter, and the proposed control method can also be implemented in unidirectional applications and other general cascaded converter system. The effectiveness has been validated by both simulation and experimental results.
    • Mechanism between Material Microstructures and Terahertz Dielectric Properties

      Yang, Bin; University of Chester (IEEE, 2019-10-21)
      Significant progress has been made in developing reliable Terahertz (THz) measurement spectroscopy to extract materials’ dielectric properties, however, systematic research on exploring intrinsic mechanism between microstructure of ceramics and THz dielectric properties such as loss, permittivity and dispersive characters has barely started. The paper focuses on one dielectric ceramic system (TiO2), its addition with Zn2SiO4 dielectrics and one hexa-ferromagnetic system to expatiate the association.
    • Micromachined Thick Mesh Filters for Millimeter-Wave and Terahertz Applications

      Wang, Yi; Yang, Bin; Tian, Yingtao; Donnan, Robert S.; Lancaster, Michael J.; University of Bolton (IEEE, 2014-03-01)
      This paper presents several freestanding bandpass mesh filters fabricated using an SU-8 based micromachining technique. The important geometric feature of the filters, which SU8 is able to increase, is the thickness of the cross-shaped micromachined slots. This is 5 times its width. This thickness offers an extra degree of control over the resonance characteristics. The large thickness not only strengthens the structures, but also enhances the resonance quality factor (Q-factor). A 0.3 mm thick, single layer, mesh filter resonant at 300 GHz has been designed, fabricated and its performance verified. The measured Q-factor is 16.3 and the insertion loss is 0.98 dB. Two multi-layer filter structures have also been demonstrated. The first one is a stacked structure of two single mesh filters producing a double thickness, which achieved a further increased Q-factor of 27. This is over six times higher than a thin mesh filter. The second multi-layer filter is an electromagnetically coupled structure forming a two-pole filter. The coupling characteristics are discussed based on experimental and simulation results. These thick mesh filters can potentially be used for sensing and material characterization at millimeter-wave and terahertz frequencies.
    • Research on the synchronization control strategy for microgrid-connected voltage source inverter

      Cao, Yuanzhi; Hu, Yanting; Hu, Rui; Chen, Jianfei (IEEE, 2015-06-30)
      Microgrid is intended and featured to be able to operate in both grid-connected and islanded mode to ensure high quality and reliable power supply. In order to achieve stable operation of the microgrid-connected voltage source inverter (MVSI) units under paralleled or grid-connected mode, a novel synchronization method based on droop control is proposed in this paper. The difference of phase and amplitude between different MVSI units is detected and is used to calculate the output frequency and amplitude of the MVSI. This method can smooth transfer the MVSI units from standalone mode to paralleled mode. The simulation and experimental results show that the proposed method is effective in achieving paralleled operation of the MVSI units.