M. Cacciato

Reduction of common mode currents in PWM inverter motor drives

Modern PWM inverter motor drives are affected by dangerous common mode currents due to the high rate of variation of the modulated voltage. An inexpensive alternative to low pass filters which are normally used to limit common mode currents, consists in reducing such currents by using suitable modulation strategies. In the present paper a new approach for designing PWM strategies is presented able to reduce common mode currents by limiting the amount of variations of the common mode voltage. The main characteristics of the proposed approach are experimentally evaluated on a standard PWM induction motor drive.

Soft-Switching Converter With HF Transformer for Grid-Connected Photovoltaic Systems

In this paper, the design, realization, and performance evaluation of a single-phase 3-kW dc/ac power converter, using an active-bridge dc/dc converter and a full-bridge dc/ac, are introduced, presenting a novel solution on the industrial scenario for the considered application. Control algorithms, including the maximum power point tracking, paralleling to the grid, and converter switching signals, are digitally implemented on a standard microcontroller.

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

A high voltage gain DC/DC converter for energy harvesting in single module photovoltaic applications

As PV modules show low voltage outputs, in grid connected applications a converter with high voltage gain is needed. Standard PV conversion systems, addressing PV field composed by a large number of panels, show efficiency values up to 95–96%. Such a high efficiency is hard to reach in small power DC/DC converters with high input to output voltage ratio as those used in AC Modules. In this paper, an experimental investigation of high voltage gain DC/DC converters for renewable resource applications is presented mainly addressing the efficiency performance. A modified interleaved boost converter is proposed and compared with state-of-the-art solutions by simulation. Finally, a laboratory prototype of the proposed solution is developed and tested showing 95% CEC efficiency.

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.

Single chip integration for motor drive converters with power factor capability

In this paper, an innovative converter topology is presented that allows to improve the performance of electronically commutated motor drives, aimed to equip home appliances. The proposed topology is based on a modified C-dump converter configuration, where the energy recovery stage acts as an active power factor controller (PFC) for offline operation. This is made possible by introducing a new technique to manage the free-wheeling energy that is recovered back to the dc bus by a suitable high frequency (HF) transformer. The proposed approach allows to omit the PFC stage that is included in motor drives devoted to home appliance applications in order to comply with power quality requirements. Moreover, the proposed converter topology features only low side or high side configuration switches, allowing to simplify the design of the drive and easily integrate the power semiconductors in a single chip exploiting smart power technologies. Simulations and experimental results confirm the validity of the proposed approach.

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.