With the increasing demand for electric vehicles, reliability in motor drives is an issue of growing importance. Over the years, various fault tolerant three-phase motor drive topologies have been introduced and their performances have been investigated. Evaluation of the post-fault power of a fault-tolerant drive should take into account both the post-fault torque and speed, which depend on both the post-fault current and voltage limits. Nevertheless, the post-fault motor voltage limits are usually omitted from discussion. Furthermore, current limit in induction motor drive is not as direct as that in permanent magnet motor drive, due to the presence of the flux current. In this paper, the performances of available fault tolerant three-phase induction motor drives have been reinvestigated, taking into account the impact of not just currents, but also voltage limits for both the inverter and machine. By deriving the post-fault machine voltage equations, the effects of machine parameters and operating point on voltage limit and hence speed limit are explained. Depending on the topology, the motor may be able to run above the rated speed to gain extra power. The analysis is verified through experiment results on a 1kW induction machine for four different fault tolerant drive topologies.

With the increasing proliferation of variable speed drive, the demand for the more reliable drive is also on the rise. Despite the growing interest on more advanced motors like permanent magnet and flux switching motors, three-phase induction motors (3ph-IMs) are still the main workhorse in the industry and hence fault-tolerant control of these motor drives remains an interesting and important topic. In this paper, a simple fault-tolerant field oriented control (FOC) technique for 3ph-IMs is presented. It is shown that by injecting zero-sequence compensation voltage in a feedforward manner, open-circuit faults can be effectively tolerated. Compared to the previous feedforward fault tolerant control methods, the proposed approach does not require the knowledge of the magnetizing inductance, which is tricky to be obtained in induction motors. Furthermore, the unified feedforward approach allows same control structure to be used for different fault-tolerant 3ph-IMs drive topologies, with minor modifications to the feedforward terms. In addition, the effect of inverter non-idealities on the performance of the proposed control method are also highlighted and addressed. The effectiveness of the proposed controller is verified using MATLAB simulation and further validated using experimental tests.

The inertia information of both synchronous generators (SGs)/equivalent SGs and converter interfaced generators (CIGs) are crucial to maintain the frequency stability of modern power grids. This paper proposes a novel data-driven method using ambient measurements, which seems to be the first method that can estimate the inertia constants of SGs/equivalent SGs and the virtual inertia constants of CIGs simultaneously without disturbing the system’s normal operating condition. Numerical studies in the IEEE 68-bus system demonstrate that the developed estimation method can estimate the inertia constants of different generation units accurately and is robust to measurement noises, missing measurements and the variation of operating conditions.

In this paper, a novel model-free wide-area damping control (WADC) method is proposed, which can achieve full decoupling of modes and damp multiple critical inter-area oscillations simultaneously using grid-connected voltage source converters (VSCs). The proposed method is purely measurement-based and requires no knowledge of the network topology and the dynamic model parameters. Hence, the designed controller using VSCs can update the control signals online as the system operating condition varies. Numerical studies in the modified IEEE 68-bus system with grid-connected VSCs show that the proposed method can estimate the system dynamic model accurately and can damp inter-area oscillations effectively under different working conditions and network topologies.

This study shows that modular multilevel converter (MMC) can implement deadbeat control and harmonic elimination together. MMC, under single‐phase deadbeat control, tracks the current reference exclusively, so that it is: (i) safe from large destructive currents of ac faults; and (ii) free from the odd harmonics generated by the non‐linearities of MMC. As a deadbeat control cannot filter even harmonics on the dc‐side, harmonic elimination has to be done by joint feedback–feedforward methods. However, the cost saving from capacitor size reduction, made possible by the harmonic elimination, comes to naught when large ac fault currents charge the capacitors to voltage levels destructive to insulated‐gate bipolar transistors. Deadbeat, in preventing the flow of large fault currents, safeguards capacitor size reduction made possible by the harmonic elimination methods. Redundant protection by the methods enhances reliability. Claims are validated by simulations by SIMULINK of MATLAB.

This letter proposes a matrix construction and calculation-based submodule capacitor voltage (SM-CV) measurement method for the MMC with reduced voltage sensors. The SMs in the same arm are divided into groups, and a voltage sensor is allocated to measure the group output voltage. After multiple sampling, a group output voltage vector is obtained and can be expressed by the product of the corresponding SM switching state matrix and SM-CV vector. Thus, the SM-CVs can be acquired by solving a matrix equation Ax = b . The sampling method is exquisitely manipulated so that the matrix equation is solvable, while easy and rapid to implement. The rationality and feasibility of the proposed measurement method have been verified by experimental results.