Mathematical analysis of the equivalent impedance at the harmonic frequency for the proposed aircraft power system

The proposals for the `More Electric Aircraft' place a significant, increased demand on the electrical power distribution system. To increase safety and reduce aircraft maintenance times on the ground, there is a greater need to quickly identify and locate electrical faults within the electrical distribution system. The work presented in this study provides the mathematical basis for the use of power system harmonic impedance measurement for identifying and locating faults within power cables. The method is passive - that is, it does not require the injection of any test signals - and can potentially be embedded into a centralised equipment controller to provide intelligent, real time diagnostics. The method monitors the harmonic line-line self-impedance at strategic points in the distribution system; this is obtained by measuring load voltage and current. Faults can be identified and located within a few fundamental cycles, and therefore provides a `backup protection' system which does not require measurement of the line current. It also can provide details of the fault location and could therefore be a significant aid to aircraft maintenance. This study derives the theoretical basis of the scheme and provides simulation results for a proposed aircraft power system to demonstrate the validity of this approach to detect and locate faults within the system

Novel operation and control modes for series-resonant converters

A series-resonant converter (SRC) able to generate an output voltage either lower or higher than the source voltage is described. Moreover, a novel control scheme is presented which renders two degrees of freedom for control and which guarantees symmetrical steady-state waveforms in all operation modes. Both the average resonant current as well as the peak voltage of the resonant capacitor can be controlled independently. Special attention is given to an operation mode which facilitates converter operation when the output voltages approximately equal the source voltage (q approx equal to 1). Test results are presented of both controller and converter

Maximum penetration level of distributed generation without violating voltage limits

Connection of Distributed Generation (DG) units to a distribution network will result in a local voltage increase. As there will be a maximum on the allowable voltage increase, this will limit the maximum allowable penetration level of DG. By reactive power compensation (by the DG unit itself) a significant increase in allowable penetration level can be achieved. In this paper this and several methods (overrating and generation curtailment) are investigated to achieve a further increase in allowable penetration level

General control method for high-frequency multiphase power converters

The control scheme presented is useful for converters which need current references for the input side in order to be able to generate input pulse patterns. The control scheme is tested and evaluated by computer simulation of a 3—phase to 3-phase series—resonant converter. A novel time—local definition of the power factor has been introduced which forms the basis of the control scheme. In this connection a theory for the calculation of optimal input current references has been developed

Novel operation and control modes for series-resonant converters

A series-resonant converter (SRC) able to generate an output voltage either lower or higher than the source voltage is described. Moreover, a novel control scheme is presented which renders two degrees of freedom for control and which guarantees symmetrical steady-state waveforms in all operation modes. Both the average resonant current as well as the peak voltage of the resonant capacitor can be controlled independently. Special attention is given to an operation mode which facilitates converter operation when the output voltages approximately equal the source voltage (q approx equal to 1). Test results are presented of both controller and converter

Maximum penetration level of distributed generation without violating voltage limits

Connection of Distributed Generation (DG) units to a distribution network will result in a local voltage increase. As there will be a maximum on the allowable voltage increase, this will limit the maximum allowable penetration level of DG. By reactive power compensation (by the DG unit itself) a significant increase in allowable penetration level can be achieved. In this paper this and several methods (overrating and generation curtailment) are investigated to achieve a further increase in allowable penetration level

Impact of distributed generation units with power electronic converters on distribution network protection

An increasing number of distributed generation units (DG units) are connected to the distribution network. These generators affect the operation and coordination of the distribution network protection. The influence from DG units that are coupled to the network with a power electronic converter (PEC) is different from that of conventional DG units with an electrical machine directly coupled to the network. This contribution shows that PEC-based DG units can be controlled in such a way that the negative influence on the distribution network protection is limited. A decision tree and a flow-chart are presented that show how a PEC-based DG should respond to network faults. The flow-chart can be used in real time to bring the proper control algorithm in operation during a fault

Impact of distributed generation units with power electronic converters on distribution network protection

An increasing number of distributed generation units (DG units) are connected to the distribution network. These generators affect the operation and coordination of the distribution network protection. The influence from DG units that are coupled to the network with a power electronic converter (PEC) is different from that of conventional DG units with an electrical machine directly coupled to the network. This contribution shows that PEC-based DG units can be controlled in such a way that the negative influence on the distribution network protection is limited. A decision tree and a flow-chart are presented that show how a PEC-based DG should respond to network faults. The flow-chart can be used in real time to bring the proper control algorithm in operation during a fault