Speed control for multi-three phase synchronous electrical motors in fault condition

The growth of electrification transportation systems is an opportunity for delving into new feasible solutions for more reliable and fault tolerant arrangements. So far, many investigations distant from the market have been carried out. Most of the works are looking at new control strategies adding extra components increasing manufacturing efforts and costs. Considering a nine phase synchronous multi-three phase electrical motor with disconnected neutral points, this manuscript compares the common speed reference configuration (where all the drives are configured in speed mode) and the torque follower configuration (where one drive is in speed mode and all the others are in torque mode). Furthermore, a post-fault operation in open-circuit condition is proposed. Analytical equations and experimental validation in nominal and fault condition are given by means of Matlab/Simulink simulations and by experimental on a 22kW test rig

Power quality improvement by pre-computed modulated field current for synchronous generators

Although power quality aspects of electrical machines have been extensively studied and investigated for a large number of years, room for improvement still exists in the field of classic, wound-field, synchronous generators. This paper proposes an innovative method of power quality improvement for single-phase synchronous generators in which the usual DC field current is replaced by a calculated current waveform. The optimised field current waveform is designed in such a way that harmonics created by the machine geometry and the winding configuration are significantly reduced

Distributed speed control for multi-three phase electrical motors with improved power sharing capability

This paper proposes a distributed speed control with improved power sharing capability for multi-three phase synchronous machines. This control technique allows the speed to be precisely regulated during power sharing transients among different drives. The proposed regulator is able to control the time constant of the current within the dq0 reference frame to a step input variation. If compared to current set-point step variations, the proposed droop controller minimises device’s stress, torque ripple, and thus mechanical vibrations. Furthermore, since distributed, it shows improved fault tolerance and reliability. The design procedure and the power sharing dynamic have been presented and analysed by means of Matlab/Simulink and validated in a 22kW experimental rig, showing good agreement with the expected performances

Response to Discussion of “A modular speed-drooped system for high reliability integrated modular motor drives”

The authors appreciate the interest shown in our paper. In the paper under discussion [1], a distributed speed control strategy suitable for multi-three-phase machines with enhanced power sharing capability is presented. The focus of the manuscript is on the power sharing transient controllability achieved by using a sharing regulator based on the droop controller, which was introduced for the first time by Fingas and Lehn [2]. In [1], the authors added the outermost loop in charge of restoring the drooped output speed. The overall control strategy and the design procedure of each loop - current, sharing, and speed - is presented and validated by means of experimental results. Two off-the-shelf three-phase induction machines coupled on the same shaft and controlled by a custom inverter were loaded by a third off-the-shelf three- phase induction machine

Enhanced power sharing transient with droop controllers for multithree-phase synchronous electrical machines

This paper presents a droop-based distributed control strategy for multithree-phase machines that provides augmented controllability during power sharing transients. The proposed strategy is able to mitigate the mutual interactions among different sets of windings without controlling any subspace variable, also offering a modular and redundant design. On the contrary, in a centralized configuration, subspaces would be controlled using the vector space decomposition, but fault tolerance and reliability levels required by the stricter regulations and policies expected in future transportation systems would not be satisfied. The proposed method is analytically compared against the state-of-the-art power sharing technique and equivalent models and control design procedures have been derived and considered in the comparison. Uncontrolled power sharing transients and their effects on mutual couplings among isolated sets of windings have been compared against the proposed regulated ones. Experimental results on a 22-kW nine-phase multithree-phase synchronous machine rig validate the design procedures showing good agreement with the expected performances

A modular speed-drooped system for high reliability integrated modular motor drives

Future transportation challenges include a considerable reduction in pollutant emissions at a time when significant increase in demand is predicted. One of the enabling solutions is the electrification of transport systems as this should lead to improved operability, fuel savings, emission reduction, and maintenance. While state-of-the-art technology has demonstrable benefits there needs to be considerable advancement to meet future transportation affordability and emission targets. Primarily, electrical drives need an improved power density, an increased reliability, and a reduced specific cost. For this reason, integrated modular motor drives (IMMDs) present an attractive solution. Modularity leads to redundancy and easier integration. This paper presents a novel speed-drooped control system applied to motors fed by modular paralleled converters. This control technique allows precise speed regulation and power sharing among different segments showing improved fault tolerance and reliability. The design procedure and the power sharing dynamic have been presented and analyzed by means of MATLAB/Simulink and validated in a 3-kW experimental rig, showing good agreement with the expected performance

A leakage-inductance-tolerant commutation strategy for isolated AC/AC converters

This paper proposes a generalised commutation strategy suitable for matrix-based isolated AC/AC conversion stages in Solid State Transformers for use whenever there is nonnegligible leakage inductance in the isolation transformer. The standard 4-step commutation used in matrix converters can no longer be applied when transformer leakage inductance is present, as overrated switching devices or dissipative snubbers would be necessary, reducing the attractiveness of the topologies that include matrix-based isolated AC/AC stages. A case study of a single-phase AC/AC converter has been investigated in detail to demonstrate the application of the proposed commutation method to a topology that has recently been identified as the potential building block for future multi-modular AC/AC converters for grid applications. The proposed leakage-inductance-tolerant commutation strategy is based on the definition of a current decoupling phase in the commutation sequence and only needs suitable timing of the commutation steps, without high bandwidth voltage or current measurements. Matching simulations and experimental results from a 3kW laboratory scale prototype are presented to support the effectiveness of the proposed strategy

Adaptive saturation system for grid-tied inverters in low voltage residential micro-grids

Provision of ancillary services, like power quality improvement is a key to attain higher utilization of multifunctional grid-tied inverter. However, the power quality improvement is mainly limited by the power capacity the grid-tied inverter. This paper explores integration issues of the next-generation intermittent power sources. In particular, two different strategies for enhancing power quality given the residual power capacity of the inverters are developed. One strategy aims to obtain the expected power quality exploiting the dynamic saturation of the inverter rated apparent power and another strategy is based on peak current detection. Both strategies offer the possibility to generate appropriate references for the inner current control loop. The two proposed strategies are compared in performance, and a discussion on their practical implementation for the best performance of the inverters is provided78478915th IEEE International Conference on Environment and Electrical Engineering (EEEIC

Control and Experimental Validation of the Series Bridge Modular Multilevel Converter for HVDC Applications

© 1986-2012 IEEE. The series bridge converter (SBC) is a modular multilevel converter (MMC) recently developed to enhance power density in high-voltage high-power applications. The MMC is a well-established solution, widely researched, and exploited in practical HVdc connections, thanks to its high power quality and high efficiency. However, the main limitation of the MMC is the relatively large energy storage, also due to the fact that power ripples in the submodule capacitors include a component at the fundamental ac frequency. As a result, volume becomes critical in applications such as offshore or city center in-feeds, where space is restricted and expensive. The SBC offers a more compact footprint by exploiting a series connection on the dc side and by operating the submodules with rectified waveforms, thus moving the minimum component of the instantaneous power to twice the ac fundamental and reducing capacitors size. The drawback of the converter is a more complex energy control compared to the MMC. This paper proposes the first experimental validation of the SBC, using a 2-kW laboratory-scale prototype. Since the basic converter design has been discussed in previous papers, the focus of this paper is on converter control design and experimental validation

Distributed current control for multi-three phase synchronous machines in fault conditions

Among challenges and requirements of on-going electrification process and future transportation systems there is demand for arrangements with both increased fault tolerance and reliability. Next aerospace, power-train and automotive systems exploiting new technologies are delving for new features and functionalities. Multi-three phase arrangements are one of these novel approaches where future implementation of aforementioned applications will benefit from. This paper presents and analyses distributed current control design for asymmetrical split-phase schemes composed by symmetrical three phase sections with even number of phases. The proposed design within the dq0 reference frame in nominal, open and short circuit condition of one three-phase system is compared with the vector space decomposition technique and further validated by mean of Matlab/Simulink ~R simulations