Motor Emulator Research Articles

Research on current sharing control of parallel inverters used on electric motor emulator

AbstractParallel inverters have the advantages of low‐output harmonics and high‐parallel power, making them very suitable as the topology structure for an electric motor emulator. However, parallel inverters can also bring about circulating current issues, especially when using carrier phase shifted sinusoidal PWM (CPS‐SPWM) control mode, which significantly increases circulating current, leading to increased output harmonics and losses in the system. In order to suppress circulating currents, this paper provides a detailed analysis from both high‐frequency and low‐frequency perspectives in CPS‐SPWM control mode. A circulating current suppression method that combines hardware and software systems, adopting a cascaded coupled output network structure along with a corresponding error voltage space vector control method to achieve circulating current suppression, is proposed. By constructing a 6‐branch parallel output experimental platform, the feasibility and effectiveness of the proposed method have been verified, suppressing current circulating currents and improving current quality.

Complex Vector-Based Stability Analysis of the High-Speed Electric Motor Emulator

Complex Vector-Based Stability Analysis of the High-Speed Electric Motor Emulator

A Novel Control Scheme for the Electric Motor Emulator to Improve the Voltage Emulation Accuracy

A Novel Control Scheme for the Electric Motor Emulator to Improve the Voltage Emulation Accuracy

Information Acquisition of Pulsating Voltage for Electric Motor Emulator Applications

Information Acquisition of Pulsating Voltage for Electric Motor Emulator Applications

Emulation of Integrated Starter/Generator Using Power Electronic Devices

Integrated starter/generator (ISG) is an important facility in transportation power systems. Using power electronics based motor emulator (ME) to test the motor controller is an emerging technique to optimize the design process of the motor drive system. In this paper, an ME is designed to test the control system of ISG in the full operation process. Facing the challenge of dual-mode emulation, a voltage-in-voltage-out interface is proposed to handle the causality problem caused by operation mode change during the starting/generating process. The LCL interface with predictive voltage closed-loop control is proposed to ensure emulation accuracy. A prototype of ME has been developed. The experiment has been done to validate the performance of the emulator, showing that the proposed method can be used to test the ISG controller in full operational mode with accuracy and fast dynamics.

Power Electronic Converter Based Induction Motor Emulator With Stator Winding Faults

The induction machine (IM) is commonly adopted in industry, which plays an important role in energy conversion between mechanical and electrical power. This paper proposes a power electronic converter-based IM power hardware-in-the-loop (PHIL) emulator, which is able to emulate an IM with internal faults. The risk, time, and cost associated with generating real faults can be reduced, helping to overcome safety issues with actual faulted machines. The technique could also be applied in fault detection, diagnosis, and fault control areas. Firstly, the IM mathematical model with inter-turn short circuit of the stator winding is established. Based on that, the PHIL emulator is developed and tested for different inter-turn short circuit conditions of an IM. A comparison of the emulator results with simulation results and actual IM results demonstrates the validity of the proposed solution.

Imagining the way forward: A review of contemporary motor imagery theory.

Over the past few decades, researchers have become interested in the mechanisms behind motor imagery (i.e., the mental rehearsal of action). During this time several theories of motor imagery have been proposed, offering diverging accounts of the processes responsible for motor imagery and its neural overlap with movement. In this review, we summarize the core claims of five contemporary theories of motor imagery: motor simulation theory, motor emulation theory, the motor-cognitive model, the perceptual-cognitive model, and the effects imagery model. Afterwards, we identify the key testable differences between them as well as their various points of overlap. Finally, we discuss potential future directions for theories of motor imagery.

Improving Dynamic Accuracy of the Electric Motor Emulator at High Speed via MIMO Design Method

The application of electric motor emulators (EME) has been prosperous in recent years along with the advancement in power hardware-in-the-loop technology. However, EME design methods based on a typical modeling approach and control structure tend to be invalid in promising a clear, dynamic accuracy objective and a robust dynamic accuracy performance over wide working points, especially at high operating speed. Hence, a new EME design method based on multi-input multioutput (MIMO) modeling and a MIMO closed-loop current control (MCLCC) structure is proposed in this article. Singular values of the MIMO motor model are analyzed to clarify the influence of the rotor speed on the dynamic accuracy objective of EME for the first time, based on which an unknown input observer is designed in the MCLCC structure to compensate for disturbance voltages caused by modeling errors. The transient tracking errors of both current and torque responses can thus be remarkably reduced at 300-Hz electrical speed in the experiment even if 35% modeling errors exist, verifying the superiority of the proposed EME design method in dynamic accuracy.

Does mental rotation emulate motor processes? An electrophysiological study of objects and body parts.

Several arguments suggest that motor planning may share embodied neural mechanisms with mental rotation (MR). However, it is not well established whether this overlap occurs regardless of the type of stimulus that is manipulated, in particular manipulable or non-manipulable objects and body parts. We here used high-density electroencephalography (EEG) to examine the cognitive similarity between MR of objects that do not afford specific hand actions (chairs) and bodily stimuli (hands). Participants had identical response options for both types of stimuli, and they gave responses orally in order to prevent possible interference with motor imagery. MR of hands and chairs generated very similar behavioral responses, time-courses and neural sources of evoked-response potentials (ERPs). ERP segmentation analysis revealed distinct time windows during which differential effects of stimulus type and angular disparity were observed. An early period (90–160 ms) differentiated only between stimulus types, and was associated with occipito-temporal activity. A later period (290–330 ms) revealed strong effects of angular disparity, associated with electrical sources in the right angular gyrus and primary motor/somatosensory cortex. These data suggest that spatial transformation processes and motor planning are recruited simultaneously, supporting the involvement of motor emulation processes in MR.

Improved Accuracy of Power Electronic-Based Motor Emulation With Compensation for Signal Transmission Delay

The power electronic based motor emulator (ME) has shown the prospect of replacing the mechanical back-to-back dynamometers with a power converter to validate the performance of the inverter under test (IUT). In real application of the ME to test the IUT, the controller of the IUT is independent from the ME, so that there’re time delays caused by the input voltage sampling of ME, ME calculation and the position signal transmission. Such a delay will cause cross coupling between dq axis which severely influence the emulation accuracy, especially under higher emulated motor speed. A compensation method is proposed to eliminate the cross coupling. A prototype is designed and simulation and experiment results are provided and compared to that of the normal motor emulator to verify the compensation effect. The experimental results have shown that the proposed compensation method can improve the emulation accuracy and a wider speed range of the motor can be emulated accurately.

A Parallel Topology Based Power-Stage PMSM Emulator With Accurate Ripple Current Reproduced

As a power hardware-in-the-loop (PHIL) technology, the power-stage motor emulator (ME) can be employed for the port characteristics emulation of motors. Meanwhile, the ripple current reproduction is one of the key technologies for achieving the high precision emulation of the port characteristics. Commonly, the high requirement for the hardware topology and the modulation strategy with rapid response and low harmonics are the main challenges. Aiming to obtain the precision ripple current, a ME scheme with dual-branch parallel topology is proposed in this paper, of which the equivalent switching frequency can be increased greatly by mean of interleaving switch. Furthermore, a new three-level space vector modulation strategy based on the idea of virtual transformation is presented. With the proposed strategy, the dual-branch parallel topology can be equivalently transformed into a specific three-phase three-level back-to-back topology. Finally, simulation and bench experiments have been conducted to validate the effectiveness of the proposed scheme. The results indicate that the proposed topology combined with the modulation strategy has a superior performance in improving the ripple current tracking accuracy of ME. Moreover, the proposed method can provide an excellent insight into improving the emulation accuracy of motor characteristics in practical applications.

Design and Implementation of a Novel Intelligent Strategy for the Permanent Magnet Synchronous Motor Emulation

In this paper, an intelligent neural network‐based controller is designed and implemented to control the speed of a permanent magnet synchronous motor (PMSM). First, the exact mathematical model of PMSM is presented, and then, by designing a controller, we apply the wind turbine emulation challenges. The designed controller for the first time is implemented on a Arm Cortex‐M microcontroller and tested on a laboratory PMSM. Since online learning neural network on a chip requires a strong processor, high memory, and convergence guarantee, this article uses the offline method. In this method, first, for different work points, the neural network is trained by local controllers, and then, the trained network is implemented on the chip and used. Uncertainty in the parameters and the effect of load torque as challenges of control systems are applied in the proposed method, and a comparison with other methods is performed in the implementation results section.

FPGA Implementation for Rapid Prototyping of High Performance Voltage Source Inverters

Field-programmable gate array (FPGA) is a powerful platform that can play an essential role in high-performance digital control of power electronics systems. However, the FPGA system’s design is quite different from that of a traditional microprocessor or a digital signal processor (DSP). Instead of sequential programming using high-level languages, such as C/C++, FPGA controller implementation requires a hardware description language (HDL) such as Verilog and VHDL, which requires extensive verification and optimization during the design process. This paper proposes a systematic FPGA design methodology with optimum resource utilization for rapid prototyping of high-performance power electronics applications to facilitate the widespread adoption of FPGA technology in power electronics. The FPGA controller design is concurrent with the power stage and utilizes high-level synthesis (HLS) tools and Simulink code generation toolbox. This paper covers the detailed design, implementation, and experimental validation of two specific applications, i.e., an active power filter (APF) and a motor emulator (ME), demonstrating the generalized features of the methodology. Employing fundamentally different control structures, both application examples achieve ultra-high current control bandwidth leveraging SiC MOSFETs switching at no less than 100 kHz.

A Common DC-Bus-Configured Traction Motor Emulator Using a Virtually Isolated Three-Phase AC-DC Bidirectional Converter

An industrial drive testing, with a `real-machine' can pave way, for some serious issues to test-bench and motor. A slight disturbance in control logic amid testing, can damage the physical machine or drive. Such dangerous testing conditions can be avoided by supplanting real motor with a power electronic converter based `Motor Emulator' (ME) test-bench system. The conventional ME comprises of two-stage three-phase AC-DC-AC conversion with first-stage AC-DC as emulator and second-stage DC-AC as regenerating unit. This two-stage power conversion, require independent control algorithm, burdening control complexity as well as the number of power electronic switches are quite significant. Hence, to economize and downsize conventional multistage ME system, this paper experimentally validates a common DC-bus-configured ME system with only the AC-DC regenerative emulator stage. A virtually isolated bidirectional two-level three-phase AC-DC converter is proposed as the regenerative emulator converter in a common DC-Bus-configured ME system. The Proposed converter's operating principle along with mathematical design and control strategy are also presented. To validate the operation of the proposed converter as a common DC-bus-configured emulator, a permanent magnet synchronous motors (PMSM) of 7.5 kW is emulated and its experimental results are presented here.

FPGA-Based High-Bandwidth Motor Emulator for Interior Permanent Magnet Machine Utilizing SiC Power Converter

A high-bandwidth (>20 kHz) motor emulator (ME) prototype for ac machines, utilizing field programmable gate array (FPGA)-based hybrid model predictive control (MPC) and a high fidelity motor model and implemented with a voltage source power converter, and fast-switching SiC devices, is presented in this article. The hybrid MPC incorporates a unique gate stitching modulation strategy that synchronizes the inverter switching state with the ME switching state for an accurate representation of the emulated motor currents in the physical inverter hardware output. The gate stitching MPC hybrid algorithm avoids the need for an excessively high switching frequency of the ME power converter. The developed high-bandwidth ME can emulate up to the switching ripple current of the inverter under test (IUT) where the current slope can change up to six times within one switching period when using space vector pulse width modulation (PWM). The FPGA-based fast iterating online motor model is another key component which along with the high-performance ME current regulation algorithm can accurately emulate the motor current. The bandwidth achieved far exceeds that of existing ME solutions that can only emulate fundamental current and only a few orders of harmonic content. The high bandwidth also allows the use of a small line inductor, which reduces the size and cost of the ME system. Simulation and experiment results are provided to the FPGA implementation and validate the high-bandwidth current emulating capability.

A Power Circulation Method Using Two Frequencies in Motor Emulator System

When an inverter is tested with a motor emulator, most of the power circulates in a loop consisting of inverter, emulator, and DC-DC converter. Only the device losses are compensated from the grid, so they usually do not exceed 20% of the circulating power. Most commonly, an isolated bi-directional DC-DC converter is used between the back ends of motor emulator and inverter. In this work, the bi-directional DC-DC converter is replaced by a three phase high frequency system between two PWM (AC-DC) converters. Furthermore, two frequency current components are used independently based on two different reference frames: the 60 Hz is utilized for power trading with the grid, whereas 2 kHz is employed for power circulation. The high frequency link is especially beneficial, since it reduces the size of isolation transformer drastically. The effectiveness of the control algorithm is supported by computer simulation and experimental results.

A Power Loss Decrease Method Based on Finite Set Model Predictive Control for a Motor Emulator with Reduced Switch Count

This paper presents a power loss decrease method based on finite set model predictive control (FSMPC) with delay compensation for a motor emulator with reduced switch count. Specifically, the topology and mathematical model of the proposed motor emulator with reduced switch count are firstly built. Secondly, in light of given instructions, the normal or fault reference current of the motor emulator is set by a reference current setter. Then delay compensation is applied for the predictive current model to calculate the current residual generated by each switch control signal, and the current tracking performance under actions of two adjacent switch control signals is evaluated for each sector. Finally, a switch power loss objective function is defined, then the two adjacent switch control signals that generate the lowest switch power loss are selected for the next second instant, which minimizes the power loss of the motor emulator with ensuring satisfied current tracking performance. Simulation and experimental results show the feasibility and effectiveness of the proposed method.

Performance Analysis of Solid-State Fractional Capacitor-Based Analog $$\hbox {PI}^\lambda \hbox {D}^{\mu }$$ Controller

This work reports analog implementation of $$\hbox {PI}^\lambda \hbox {D}^\mu $$ controller realized by solid-state fractional capacitor. The fractional integrator is implemented with a solid-state fractional capacitor fabricated by the authors, and the fractional differentiator circuit is implemented using optimal pole–zero interlacing algorithm. The paper proposes a tuning algorithm for finding the parameters of the fractional $$\hbox {PI}^{\lambda }\hbox {D}^{\mu }$$ controller to get the desired time domain performance. Using the tuning algorithm, the combinations of $$\lambda $$, $$\mu $$ and gain values of the controller are evaluated on a DC motor emulator to limit % overshoot $$\le $$ 12% and settling time < 13 ms. The performance of the controller (with $$\lambda = \mu = 0.4$$) on speed regulation of DC motor emulator has also been discussed in detail both in simulation and in hardware.

Power Electronic Converter-Based Induction Motor Emulator Including Main and Leakage Flux Saturation

Different electric machines are considered for electrified transportation systems. A failure in the control algorithm can result in damage to both the drive and the connected machine. In this paper, an induction motor emulator based on a power electronic converter is developed to allow detailed testing the converter and controller. A proportional-resonant current controller in the abc-frame and pulsewidth modulation is employed. The conventional model of the induction machine with constant parameters does not represent accurately the machine’s performance for severe transients specifically during starting and loading conditions. Magnetic saturation effects should be considered. Hence, experimental procedures to determine the flux saturation characteristics in the main and both stator and rotor leakage flux paths are achieved. An approach that utilizes finite-element modeling to separate the leakage reactance at rated current and when the machine is deeply saturated is discussed and verified experimentally. Machine models that consider or neglect the main and leakage flux saturation are compared with experimental results. The model, which considers the magnetic saturation effect in both flux paths, results in more accurate transient responses. Likewise, the dynamic response of the induction motor emulator during startup and loading transients shows the effectiveness of using the developed emulator to resemble closely a real motor.

LABORATORY STAND FOR SMALL WIND TURBINE SIMULATION

The article presents a concept of the laboratory stand for wind turbine simulation, built on the basis of cage induction motor, supplied from a frequency converter. The model assumes control of the engine torque, using simple constant Volt/Hertz control with slip regulation, taking into account the moment of inertia of the simulated turbine. Performance of the system for different wind and generator load conditions has been shown. Test results proved, that the turbine torque is well tracked by the wind motor emulator.