- Power System Protection
- Control and Protection of Inverter-Based Power Grids
- Engineering Education
Mahamedi, B, Eskandari, M, Fletcher, JE & Zhu, J 2019, 'Sequence-Based Control Strategy with Current Limiting for the Fault Ride-Through of Inverter-Interfaced Distributed Generators', IEEE Transactions on Sustainable Energy.View/Download from: Publisher's site
IEEE Three-phase three-leg inverters comprise the majority of inverters that are integrated into power grids. They can develop positive- and negative-sequence components under unbalanced conditions including asymmetrical faults, but not zero sequence. This indicates that a sequence-based control strategy is required for a comprehensive control of inverter currents and voltages, hence positive- and negative-sequence components must be controlled separately with their own dedicated controllers. Given this critical need, a sequence-based control technique for grid-forming and grid-feeding inverter-interfaced distributed generators (IIDG) is proposed. As a necessary part of the fault ride-through (FRT) capability of IIDGs, a current limiter is developed which can limit inverter currents at a pre-defined threshold for both balanced and unbalanced faults/voltage sags. Whilst the current regulators work in the synchronous reference frame with simple PI controllers, the limiter works in natural reference frame and thus treats each phase current separately, which results in current limiting at the threshold for all phases. The advantage of the proposed limiter is that it virtually acts instantaneously such that the inverter current can be limited from the start of the disturbance. The simulation results in MATLAB/SIMULINK reveal promising performance of the proposed control strategy with the proposed current limiting.
Mahamedi, B, Zhu, JG, Eskandari, M, Fletcher, JE & Li, L 2018, 'Protection of inverter-based microgrids from ground faults by an innovative directional element', IET GENERATION TRANSMISSION & DISTRIBUTION, vol. 12, no. 22, pp. 5918-5927.View/Download from: UTS OPUS or Publisher's site
Mahamedi, B & Zhu, JG 2017, 'Double-ended technique for distinguishing series faults from shunt faults on transmission lines using the sequential components of impedance', IET Generation, Transmission and Distribution, vol. 11, no. 6, pp. 1381-1388.View/Download from: UTS OPUS or Publisher's site
© 2017 The Institution of Engineering and Technology. This study describes a new double-ended technique for distinguishing series faults from shunt faults. The proposed method is based on the sequential components of impedance. Using the local and remote positive-sequence voltage and the local positive-sequence current, a new value is introduced and utilised to distinguish series faults, mostly known as broken conductors, from shunt faults. As the proposed method utilises a double-ended technique, it will act when the necessary information of the remote end of the line is received. By detecting the broken conductor condition within a few power cycles, this method can trip the circuit breakers at both line ends before any conductor contacts the earth, and thus can avoid safety problems and damages to the electrical equipment. Moreover, it can also classify which type of broken conductor (one-phase or two-phase) condition has occurred. The excellent performance of the proposed method is demonstrated by extensive simulation studies with MATLAB/Simulink.
Mahamedi, B, Zhu, JG & Hashemi, SM 2016, 'A Setting-Free Approach to Detecting Loss of Excitation in Synchronous Generators', IEEE TRANSACTIONS ON POWER DELIVERY, vol. 31, no. 5, pp. 2270-2278.View/Download from: Publisher's site
Mahamedi, B, Sanaye-Pasand, M, Azizi, S & Zhu, JG 2015, 'Unsynchronised fault-location technique for three-terminal lines', IET Generation, Transmission & Distribution, vol. 9, no. 15, pp. 2099-2107.View/Download from: Publisher's site
This study describes a new fault-location technique using negative-sequence voltage for three-terminal lines.
The ratios between the negative-sequence voltage magnitudes measured at each terminal are utilised to first
determine the faulted section and then to estimate the exact fault location within the section. Since the current data is
not deployed, the influence of inherent errors of current transformers can be avoided. The proposed method can
accurately locate the unbalanced faults, that is, single-phase-to-ground, double-phase-to-ground, and phase-to-phase
faults, regardless of the fault resistance and pre-fault conditions and without any need to identify the fault type. The
method requires only the negative-sequence reactance behind each terminal which can be estimated by the shortcircuit
analysis with an acceptable accuracy. Reliability and practicality of the proposed method make it an attractive
option to include in numerical protective relays. Simulation experiments with different fault cases reveal the capability
of the proposed method.
Mahamedi, B & Zhu, JG 2014, 'Unsynchronized Fault Location Based on the Negative-Sequence Voltage Magnitude for Double-Circuit Transmission Lines', IEEE TRANSACTIONS ON POWER DELIVERY, vol. 29, no. 4, pp. 1901-1908.View/Download from: UTS OPUS or Publisher's site
Mahamedi, B & Zhu, J 2013, 'Fault Classification and Faulted Phase Selection Based on the Symmetrical Components of Reactive Power for Single-Circuit Transmission Lines', IEEE Transactions On Power Delivery, vol. 28, no. 4, pp. 2326-2332.View/Download from: UTS OPUS or Publisher's site
This paper presents a fault classification method with faulted phase selection action for single-circuit transmission lines which is based on the symmetrical components of reactive power. The proposed method does not need any threshold to operate and it
Mahamedi, B & Zhu, J 2012, 'A Novel Approach To Detect Symmetrical Faults Occurring During Power Swings By Using Frequency Components Of Instantaneous Three-Phase Active Power', Ieee Transactions On Power Delivery, vol. 27, no. 3, pp. 1368-1376.View/Download from: UTS OPUS or Publisher's site
Since distance relays are prone to interpret a power swing as a three-phase fault, they should be blocked during the power swing to prevent undesired trips. On the other hand, if any fault occurs during a power swing, they should be fast and reliably unb