G. Scelba

Steady-State and Transient Operation of IPMSMs Under Maximum-Torque-per-Ampere Control

This paper analyzes different aspects of the maximum-torque-per-ampere (MTPA) vector control of interior permanent-magnet synchronous motors at steady state and transient. Two different implementations are considered: a nonlinear-model-based MTPA profile including saturation and cross-saturation effects and a technique based on the maximization of the motor input power versus stator current. Furthermore, this paper analyzes the torque evolution during a transient under an MTPA control strategy on motors with different characteristics. Useful modifications of the current loop are suggested to improve the drive performance. The effects of the torque transient on the sensorless rotor position estimation are also taken into consideration, in case a sensorless MTPA implementation is required. Experimental results confirm the theoretical analysis, showing the benefits of the new control schemes.

Multicriteria Optimal Sizing of Photovoltaic-Wind Turbine Grid Connected Systems

Power generation systems (PGSs) based on hybrid renewable energy are one of the promising solutions for future distributed generation systems. Among different configurations, hybrid photovoltaic-wind turbine (PV-WT) grid connected PGSs are the most adopted for their good performance. However, due to the complexity of the system, the optimal balance between these two energy sources requires particular attention to achieve a good engineering solution. This paper deals with the optimal sizing of PV-WT by adopting different multicriteria decision analysis (MCDA) optimization approaches. Sensitivity of MCDA algorithms has been analyzed, by considering different weighting criteria techniques with different fluctuation scenarios of wind speed and solar radiation profiles, thus highlighting advantages and drawbacks of the proposed optimal sizing approaches. The following study could be assumed as a powerful roadmap for decision makers, analysts, and policy makers.

An Effective Energy-Saving Scalar Control for Industrial IPMSM Drives

This paper deals with the analysis and implementation of a new scalar control technique for industrial interior permanent-magnet synchronous motor drives that exploits energy-saving capability. In particular, the proposed control strategy forces the conditions of maximum torque per ampere (MTPA), flux weakening (FW), and maximum torque per voltage (MTPV) simply by assigning polynomial relationships between the operating angles of the machine. Although the dynamic performance of the drive is worsened compared to that of vector control schemes, the modified scalar control allows us to work in energetic conditions, very close to those obtained with vector-controlled drives exploiting MTPA, FW, and MTPV strategies. The control techniques are implemented without using any speed and voltage measurement and with only a single current feedback. This paper provides a detailed study of the control strategy, showing the effectiveness and limitations of the method through simulations and experimental results.

Efficiency optimization techniques via constant optimal slip control of induction motor drives

The paper proposes a novel control technique that is able to optimize the efficiency in scalar controlled induction motor drives. The proposed strategy is based on a constant-optimal slip control and is able to modify the magnetizing flux value increasing the efficiency at light loads. Differently from the optimization methods present in the literature, the proposed approach does not require the model of the machine, does not solve any losses minimization equation and is not based on a minimum losses or minimum power search algorithm. The presented technique is based on an intuitive adaptation of the well known maximum torque per ampere (MTA) algorithm to a new version for scalar control, ensuring a constant-optimal slip. A key point is the possibility to achieve the efficiency optimization by using the same hardware as in standard adjustable speed drives operated by V/f or conventional slip control. An experimental evaluation has been accomplished on a 1,5 Hp induction motor drive to measure the losses minimization and verify the dynamic performance of the proposed method

Modified Space-Vector-Modulation Technique for Common Mode Currents Reduction and Full Utilization of the DC Bus

Unless overmodulation is adopted, utilization of DC bus of the Modified Space Vector Modulation (MSVM) is a drawback that has severely limited the applicability of this modulation technique. This paper presents some solutions that, looking for a good compromise between increasing the use of DC bus and reducing common mode currents, allow to apply MSVM to most electrical drives on the market. Furthermore, the choice of the switching patterns is performed according to the sign of the load currents thus reducing the common mode voltage variations to a single pulse per switching period in presence of large dead-times. Experimental results are presented in order to confirm the feasibility of the proposed approach.

Sensorless Vector Control of PM Synchronous Motors During Single-Phase Open-Circuit Faulted Conditions

This paper deals with the study and development of new control solutions of permanent-magnet synchronous motor (PMSM) drives specifically aimed to operate under sensorless vector control even during fault conditions. The phase imbalance produced by an open-phase fault leads to the failure of several sensorless estimation algorithms based on either machine models or high-frequency signal injection. Exploiting a recently proposed machine model for three-phase faulted PMSM drives, the practical implementation of sensorless vector controls for such drives under asymmetric conditions due to a single-phase open-circuit fault is performed. The effects of the magnetic/geometrical asymmetries during the fault are studied, and the techniques able to mitigate such effects on the rotor position information are provided. The rotor position estimation is achieved in a wide operating range during the fault as it is confirmed by experimental tests.

Modeling control of IPM synchronous motors

Almost all authors that have implemented current vector control of interior permanent magnet synchronous motors, need to compensate the nonlinear effects characterizing such machines due to saturation and air-gap flux redistribution. In this paper, with the intent of offering an analytical approach to the control laws that govern any optimized operation of the motor on a wide speed range including field-weakening, a nonlinear model of the IPM machine is introduced and adopted as the tool to deduce the control equations. Experimental tests are performed on a IPM machine to show the non linearities, to model them accurately, and to check the validity of the proposed control techniques.

Fault-tolerant rotor position and velocity estimation using binary hall-effect sensors for low-cost vector control drives

High-resolution position and velocity estimation algorithms based on binary Hall-effect sensors for low-cost vector control drives have been the subject of significant research in recent years. While different estimation algorithms have been proposed and analyzed, no contribution so far has dealt with Hall-effect sensor faults and their repercussion on the drive. Here, single and multiple Hall-effect sensor faults are analyzed, and a method to detect, identify, and mitigate such faults is investigated. The method is general, and it ensures proper operation of the drive and is not dependent on the particular estimation algorithm that is used; by way of example, here it will be applied to a vector-tracking observer. Limitations on the performances of the faulty system are discussed, and experimental results are reported to confirm the theoretical analysis.

Fault-Tolerant AC Multidrive System

This paper deals with an original control strategy for AC multidrive systems able to mitigate the effects of failures occurring on one or more drives. A key feature of the proposed technique is that fault tolerance capability is achieved by a suitable reconfiguration of the system in order to allow the healthy drives to provide additional paths for the currents of the faulty drives. Moreover, a modified control algorithm able to enforce the vector control in damaged drives has been implemented, by cooperatively managing some or all the drives of the system. Therefore, differently from previous techniques, the fault tolerance capability is achieved by exploiting the healthy drives, rather than activating back-up inverter legs. As a result, no additional high-frequency switching power devices and related drives circuitries are needed. In the following, two different scenarios will be analyzed, highlighting pros and cons of the proposed approach through simulations and experimental results.

Real-Time Model-Based Estimation of SOC and SOH for Energy Storage Systems

To obtain a full exploitation of battery potential in energy storage applications, an accurate modeling of electrochemical batteries is needed. In real terms, an accurate knowledge of state of charge (SOC) and state of health (SOH) of the battery pack is needed to allow a precise design of the control algorithms for energy storage systems (ESSs). Initially, a review of effective methods for SOC and SOH assessment has been performed with the aim to analyze pros and cons of standard methods. Then, as the tradeoff between accuracy and complexity of the model is the major concern, a novel technique for SOC and SOH estimation has been proposed. It is based on the development of a battery circuit model and on a procedure for setting the model parameters. Such a procedure performs a real-time comparison between measured and calculated values of the battery voltage while a PI-based observer is used to provide the SOC and SOH actual values. This ensures a good accuracy in a wide range of operating conditions. Moreover, a simple start-up identification process is required based on battery data-sheet exploitation. Because of the low computational burden of the whole algorithm, it can be easily implemented in low-cost control units. An experimental comparison between SOC and SOH estimation performed by suggested and standard methods is able to confirm the consistency of the proposed approach.