Ivan Spina

High performance control technique for unbalanced operations of single-vsi dual-PM brushles motor drives

The paper deals with isotropic PM-brushless drives in configuration “single-inverter, dual-motor” operating with unbalanced load-torques. After a short review of some control techniques based on the classical control methodologies of single-motor PM drives, an innovative control algorithm is presented. It is suitable to minimize the resultant armature current needed to obtain an assigned resultant motor torque, whatever is the load unbalance. Simplified analytical expressions are given in order to quickly evaluate optimized reference currents with good approximation. From these reference values, a predictive feeding algorithm evaluates the reference voltage space-vector for the inverter supplying the two motors in parallel. Current and torque oscillation, torque/current ratio, dynamic response and stability are the mainly observed quantities. Effectiveness of proposed control technique is highlighted.

A parameter estimation method for on-line failure detection in permanent magnet AC-brushless motors having current-dependent parameters

With reference to anisotropic permanent magnet (PM) brushless motors, the papers deals with a procedure for on-line identification of electrical parameters, based on the “recursive least square method”, designed for the cases of strong parameters variation depending on the operating condition. The identification procedure is superimposed to a conventional control diagram of PM AC-brushless drives (either torque-control or speed-control) and is really very simple. The results of this analysis can be used as identifiers of failure conditions in the drive; otherwise, during motor characterization on a test-bench, the method can be a simple instrument to map motor parameters in different operating conditions. The proposed technique is tested by means of numerical investigation on a motor whose electrical parameters have been off-line evaluated by experimental measurements and mapped in different operating conditions.

Comparative analysis of performance and energy losses in light railways vehicles equipped with IM or PMSM drive

With reference to light railways transportation systems, in the paper a comparison is carried out between vehicles equipped with either Induction Motor Drive or Permanent Magnet Brushless Motor Drive. The attention is particularly focused on energetic performance, in term of losses and efficiency. The main characteristics of the traction units of the two compared vehicles have been chosen in accordance with the real constraints, usually imposed or suggested by the motor type, which influences mechanical and electrical configurations, control architectures and techniques. Thus, the analysis has not the aim to compare specific devices, which are different for the two considered cases, but the whole traction units, each one with its own proper characteristics. Based on both assigned characteristic of the railways sections and vehicle mission, an extensive numerical analysis has been carried out in various operating conditions, with the aim to comparatively evaluate either fast dynamic performance, in response to the PWM modulation, or slow dynamic performance, concerning the time constant of mechanical quantities, or losses and energy efficiency.

A nomogram for estimating energy loss in a distribution network due to penetration of V2G

As Vehicle-to-Grid (V2G) concept convenes strong interests among automakers, electric utility owners, and policy makers, it is critical to investigate the potential impacts of V2G on the electric distribution system. Such study, together with other benefits of V2G, may encourage utility support for V2G commercialization. This paper focuses on a pressing technical issue associated with the penetration of V2G into the electric distribution network-the energy loss in the feeders. Mathematical models are formulated to investigate how V2G reactive power injection and different load patterns can impact energy loss on a distribution system. It is shown that loss reduction can be greatly influenced by reactive loading factor, the pattern of loading, the amount of V2G reactive power injection, and the position of V2G parking lot on the feeder segment. Useful results are obtained, with a promise that more than 95% energy loss reduction (relative to energy loss in the system without V2G installed) is possible by optimally locating a V2G parking lot along the feeder. The results in this study may serve as a nomogram to determine energy loss at the planning stage of installing a V2G parking lot on a distribution feeder segment.

Controlled Fault-Tolerant Power Converters for Power Quality Enhancement

Power quality depends generally on the interaction of electrical power with electrical equipments. If electrical equipments operate correctly and reliably without being damaged or stressed, a suitable level of power quality is assured. On the other hand, if the electrical equipment malfunctions, is unreliable, or is damaged during normal usage, power quality is poor and probably the economical loss could be important like the technical one. In the scenario of the Distributed Generation, power quality issues will be moreover important because an higher dissemination of power conditioning equipment will be requested and this obviously increases the sources of vulnerability of the electrical system. In this paper fault tolerant power converters are considered as a viable solution of power quality problems and a suitable control algorithm of them is presented. The control proposed in the paper is based on the model of the power converter reformulated in terms of healthy leg binary variable and the paper shows how this control is able to save the aspect of power quality when the converter works in the linear range. The effectiveness of such an algorithm and of the fault tolerant power converters are finally verified by means of simulations.

A Novel Fuel Cell-Based Power System Modeling Approach

Nowadays, fuel cells are the most promising source of energy for stationary applications. Unfortunately, the power density of fuel cells is not adequate for modern applications. A fuel cell - based hybrid power supply is required. The fuel cell is coupled with a high-energy density power source to improve performances of the composite power source. A power management stage is introduced between the two basic sources to control the power flow path from the fuel cell to the auxiliary source and the load. In order to avoid effects of a limited power density of the fuel cell on the whole power supply, sophisticated power management algorithms are implemented. Accurate modeling is required to test hybrid source performances as closely as possible to the actual working conditions since the simulation step, avoiding risks of experimental failure. In this paper, a fuel cell - battery hybrid power supply system for household appliances is presented. The power system is implemented in PSIM environment, the house model is implemented in MATLAB environment and MATLAB co-simulation is provided to test the whole composite system. Simulation results are shown to test the efficiency of the novel approach.

A simple on-board electric generator for road electric vehicles based on single-cylinder engine and PM-brushless generator

The article discusses the proposal, specifications and overall performance of a 10 kW electric power range extender suitable for electric plug-in and series hybrid vehicles, based on a single cylinder, four stroke internal combustion engine, derived from a motorcycle engine, modified and developed at Istituto Motori CNR of Italy, coupled with a PM generator. This unit has been thought as a low-cost mobile recharging system for city cars and small commercial vehicles and its based on the required characteristics of a modern electric city car to define the reference power for the range extender. In the paper is explained the ratio which leaded to the adoption of a single cylinder internal combustion engine, followed by details of the main design characteristics of the unit, which has been assembled just with off-the-shelf elements, in order to reduce the cost coming from new design and making. The use of the air cooling for the electric generator (a permanent magnet axial unit) permitted to simplify the whole system, still allowing an easy packaging of the same for the final application on the vehicle. As field test, a complete description of functioning of the internal combustion engine and the generator has been reported; then the two sub-systems have been coupled together and finally tested as a whole system with conventional unleaded gasoline.

Simplified Optimum Control Method for Monoinverter Dual Parallel PMSM Drive

This paper proposes a simplified optimum control strategy for a monoinverter dual parallel (MIDP) permanent magnet synchronous motor (PMSM). With reference to the parallel PMSM unified model, two different auxiliary conditions are investigated. The first minimizes the supplied inverter current, and the second maximizes the motors efficiency. Their formal expressions are derived by the introduction of three new normalized variables, linked to the load conditions. Thus, the optimum tracking considerations are general, and the parameters are independent. Simplified closed analytical forms are found for the optimum tracking, independently under steady-state and transient conditions. The selection of the best solution is then found via a parameter independent look-up table, and imposed through a closed-loop control diagram. The proposed control is compared to the present state of the art via experiments on a 1400-W MIDP PMSM test bench, showing an equivalent performance, with a lower computational burden.

Model predictive control for PMSM with flux-current nonlinear maps

Typical operating conditions of permanent magnet synchronous motors correspond to nonlinear relationships between fluxes and currents. The determination of equivalent motor parameters is a non trivial task and can be critical for the design of motor controllers, which is typically based on a mathematical model. In this paper an experimental method to determine the flux-current nonlinear maps and a model based approach to implement a predictive controller capable to deal with such nonlinearities is presented. Numerical results show that the optimization technique is able to provide the maximum torque per ampere tracking.

A voltage divider strategy for reducing the hot spot temperature in partially shaded solar panels

Over-temperature occurring in silicon solar panels, subject to partial shadowing, are reduced by means of a series connected voltage divider which sustains part of the reverse voltage developing across the shaded solar cells. The circuit is based on a power MOSFET which is driven by the output voltage of the solar panel. When the solar panel is uniformly illuminated the MOSFET is in the ON state and does not affect the operation of the module, while, when the solar panel is partially shaded, and the output voltage decreases, the MOSFET enters in the pinch-off operation mode, thus subtracting its voltage from the reverse voltage across the shaded cell. Experiments performed on a commercial solar panel showed one third of reduction of the reverse voltage across shaded solar cells, with a reduction of the hot spot temperature of about 25°C.