Review of Field Weakening Control Strategies of Permanent Magnet Synchronous Motors

Due to high power density,high efficiency,and accurate control performance,permanent magnet synchronous motors(PMSMs)have been widely adopted in equipment manufacturing and energy transformation fields.To expand the speed range under finite DC-bus voltage,extensive research on field weakening(FW)control strategies has been conducted.This paper summarizes the major FW control strategies of PMSMs,which are categorized into calculation-based methods,voltage closed-loop control methods,and model predictive control related methods.The existing strategies are analyzed and compared according to performance,robustness,and execution difficulty,which can facilitate the implementation of FW control.

A Novel Flux-weakening Control Method with Quadrature Voltage Constrain for Electrolytic Capacitorless PMSM Drives

In electrolytic capacitorless permanent magnet synchronous motor(PMSM) drives, the DC-link voltage will fluctuate in a wide range due to the use of slim film capacitor. When the flux-weakening current is lower than-ψf/Ld during the high speed operation, the flux-weakening control loop will transform to a positive feedback mode, which means the reduction of flux-weakening current will lead to the acceleration of the voltage saturation, thus the whole system will be unstable. In order to solve this issue, this paper proposes a novel flux-weakening method for electrolytic capacitorless motor drives to maintain a negative feedback characteristic of the control loop during high speed operation. Based on the analysis of the instability mechanism in flux-weakening region, a quadrature voltage constrain mechanism is constructed to stabilize the system.Meanwhile, the parameters of the controller are theoretically designed for easier industrial application. The proposed algorithm is implemented on a 1.5 kW electrolytic capacitorless PMSM drive to verify the effectiveness of the flux-weakening performance.

A Review of Sensorless Control Methods for AC Motor Drives

In recent years,the application of sensorless AC motor drives is expanding in areas ranging from industrial applications to household electrical appliances.As is well known,the advantages of sensorless motor drives include lower cost,increased reliability,reduced hardware complexity,better noise immunity,and less maintenance requirements.With the development of modern industrial automation,more advanced sensorless control strategies are needed to meet the requirements of applications.For sensorless motor drives at low-and zero-speed operation,inverter nonlinearities and motor parameter variation have significant impact on the stability of control system.Meanwhile,high observer’s bandwidth is required in high-speed region.This paper introduces the state of art of recent progress in sensorless AC motor drives.In addition,this paper presents the sensorless control strategies we investigated for practical industrial and household applications.Both advanced sensorless drives of induction motor(IM)and permanent magnet synchronous motor(PMSM)are presented in this paper.

Self-Adaptive Stepsize Affine Projection Based Parameter Estimation of IPMSM Using Square-Wave Current Injection

Affine projection algorithm(APA)has been used to estimate the parameters of interior permanent magnet synchronous motor(IPMSM).However,there is not a strict guideline of choosing the stepsize of this algorithm to make sure that the results of parameter estimation are convergent.In order to solve such problem,self-adaptive stepsize affine projection algorithm for parameter estimation of IPMSM is proposed in this paper.Compared with traditional affine projection algorithm,this method can obtain the stepsize automatically based on the operation condition,which can ensure the convergence and celerity of the process of parameter estimation.Then,on the basis of self-adaptive stepsize affine projection algorithm,a novel parameter estimation method based on square-wave current injection is proposed.By this method,the error of estimated parameter caused by stator resistance,linkage magnetic flux and dead-time voltage can be reduced effectively.Finally,the proposed parameter estimation method is verified by experiments on a 2.2-kW IPMSM drive platform.

Message from Editors

ELECTRICAL machine systems have found extensive applications,for which various machine topologies have been proposed in the recent years.Performance analysis and optimal design with theoretical methods and multi-field finite element methods are key issues for developing high-end products.Meanwhile,control strategies linked with specific machine topologies and design considerations are rather beneficial for the electrical machine systems,in the aspects of energy efficiency,output smoothness,control precision,dynamic response,and many others.

Inaugural Statement on the First Issue of the New Journal

IT is a great honor for us to make an inaugural statement on the new journal-CES Transactions on Electrical Machines and Systems(CES TEMS).We wish this new publication would be popular among the readers concerned.The journal is co-sponsored by China Electrotechnical Society(CES)and the Institute of Electrical Engineering of the Chinese Academy of Sciences(IEECAS).It is technically co-sponsored by the IEEE Power Electronics Society(PELS)and all our contents will be hosted by IEEE Xplore with Open Access.

Review of Inductance Identification Methods Considering Inverter Nonlinearity for PMSM

Permanent magnet synchronous motors(PMSMs)are widely used in high-power-density and flexible control methods.Generally,the inductance changes significantly in real-time machine operations because of magnetic saturation and coupling effects.Therefore,the identification of inductance is crucial for PMSM control.Existing inductance identification methods are primarily based on the voltage source inverter(VSI),making inverter nonlinearity one of the main error sources in inductance identification.To improve the accuracy of inductance identification,it is necessary to compensate for the inverter nonlinearity effect.In this study,an overview of the PMSM inductance identification and the related inverter nonlinearity self-learning methods are presented.

Modular Multilevel Converter with Thyristor DC-link Switch for Full-torque Variable-speed Drives

The modular multilevel converter(MMC)is a promising topology for medium-voltage drive applications due to its high-quality output waveforms,low device switching frequency and voltage rating.However,the large cell capacitor voltage ripple is a severe challenge faced by MMC at low motor speeds.Recently,a hybrid MMC(HMMC)topology is proven to be a competitive solution because of its lower cell capacitor voltage ripple and not demonstrating a common-mode voltage(CMV)problem compared with other methods.However,the DC-link switch with IGBT limits HMMC from being applied in highvoltage applications.This paper uses a thyristor instead of IGBT as the DC-link switch.To ensure the thyristor can be softly turned on and safely turned off,a new control scheme is proposed.When using this proposed scheme,HMMC can also tolerate the failure of the thyristor being turned-off without shutting down the system,effectively improving its reliability.The cell capacitor voltage ripple analysis is presented considering the effects of the thyristor switching process.In addition,a decoupled energy balancing control is utilized to suppress the fluctuation of the DC current.Experimental results obtained from a 380 V/7.5 kW downscaled prototype validate the effectiveness of starting up a motor from the standby mode to rated speed applying full-torque.

Multi-objective energy management system for DC microgrids based on maximum membership degree principle

With the increasing quantity of DC electrical equipment, DC microgrids have been paid more and more attention. This paper proposes an approach to multi-objective optimisation of an energy management system(EMS) for a DC microgrid that includes a hybrid energy storage system(HESS). The operating and maintenance cost and the loss of power supply probability(LPSP) of the system are used as optimisation targets. The power flows of all distributed generators(DGs) in the DC microgrid during operating period are optimized. Based on the improved differential evolution(DE) algorithm, and by using the multi-objective non-dominated sorting method and the maximum membership degree principle(MMDP) of fuzzy control, the overall satisfaction degree of Pareto solutions to power flow optimization can be obtained. Simulation results verify the effectiveness of the proposed EMS optimization scheme, which is able to achieve an effective trade-off between the economy and the reliability of microgrid operation.

Review of Parameter Identification and Sensorless Control Methods for Synchronous Reluctance Machines

Synchronous reluctance machines(SynRMs)have drawn increasing attention in recent years owing to their advantages such as low cost,simple structure,ease of manufacture,and high robustness.The main obstacle to the promotion of SynRMs is severe parameter nonlinearity,which deteriorates drive performance.Sensorless control methods for SynRMs are critical technologies that can broaden the industrial applications of SynRMs.Various methods of parameter identification and sensorless control strategies are reviewed and discussed,including self-commissioning,which is analyzed in detail.Furthermore,sensorless control strategies that can improve the industrial application of SynRMs are described.Finally,future research trends concerning SynRMs are analyzed and discussed.

Saliency-Based Position Sensorless Control Methods for PMSM Drives-a Review

Permanent magnet synchronous motor(PMSM)drives are finding expanded use for industrial and domestic drive applications.With the distinguished characteristics such as reduced cost and increased reliability and robustness,position sensorless(self-sensing)control techniques have been good candidates for reliable and costless PMSM drives.The saliency-tracking based techniques further bring the expansion of applications with the extended controllable sensorless operating speed range.This paper presents a review on state of the art techniques for position sensorless drives using the saliency-tracking based methods.The signal injection methods and the future scope of research including the dynamic bandwidth improvement and the acoustic noise reduction are discussed.

Robust Damping Method For Voltage Source Converter with LCL-type Filter Under Weak Grid Conditions

Power electronic converters under weak grid conditions may trigger new dynamic stability problems.Even though massive internal and external damping methods have been investigated,their system costs and robustness have not been solved in an effective way.This paper first proposes a sensorless active damping method based on the grid current feedback filter.The mid-frequency non-passive region of converters can be reduced effectively,thus system stability improvement in weak grids can be realized.Then this paper analyzes the feedback filter which may bring about additional non-passive regions in high frequency.What’s more,it has a poor robustness.The residual mid-frequency non-passive region can be enlarged under converter parameter variations.Furthermore,this paper proposes a hybrid active damping method.The grid voltage is fed forward through a low pass filter.The robustness against parameter variation is greatly improved and the non-passive region in high frequency is also totally eliminated.In order to further improve the system robustness in high frequency,a simple passive damping is also added.The damping resistor is designed small to reduce the damping loss.The simulation and experimental results prove that the proposed sensorless method can realize robust damping in an economic way.

Effective Control of Smart Hybrid Power Systems:Cooperation of Robust LFC and Virtual Inertia Control Systems

A modern power system is expected to consist primarily of renewables,which either lack or have less rotating masses(i.e.,source of inertia)compared to the traditional generation sources.However,the growth of renewables generation,based on power electronics,can substantially decrease the inertia levels of renewable power grids,which can create several frequency stability issues,resulting in power system degradation.To address this issue,this paper presents a recent virtual inertia scheme predicated on electric vehicles(EVs)to mimic the necessary inertia power in low-inertia smart hybrid power systems(SHPSs),thus regulating the system frequency and avoiding system instability.Moreover,to guarantee robust performance and more stability for SHPSs against multiple perturbations,system uncertainties,and physical constraints,this paper also proposes a robust control strategy relying on a coefficient diagram method(CDM)for the load frequency control(LFC)of SHPSs considering high renewables penetration and EVs.The efficacy of the proposed system(i.e.,robust LFC with the proposed VIC strategy)is validated by comparison with a conventional LFC with/without the proposed VIC system.In addition,the simulation outcomes show that the proposed system can considerably support smart low-inertia hybrid power systems for many different contingencies.