James E. Walters

A 4-kW 42-V induction-machine-based automotive power generation system with a diode bridge rectifier and a PWM inverter

In recent years, the electrical load demand in automobiles has been increasing steadily due to the usage of several subsystems to improve engine performance, passenger comfort and safety. The current production Lundell alternator is not able to meet the future growing power demand due to its inherent design limitations. Therefore, an efficient, high power generation system is needed to meet the growing electric power demand in automobiles. The recent trend to adopt the 42 V power system in automobiles allows one to add more subsystems in an efficient way. In this paper, a three-phase, 42 V, 4 kW, induction machine based automotive power generation scheme is proposed to meet the future electrical power demand in automobiles. This scheme uses a low cost diode bridge rectifier directly connected to the induction machine to transfer active power to the battery and the load. The excitation to the machine is supplied by means of a low power PWM inverter to control the output voltage of the generator connected to the diode bridge rectifier. This paper presents a new control methodology to regulate the output voltage of an induction generator directly connected to a diode bridge rectifier by controlling the auxiliary PWM inverter. The simulated performance results of a 4 kW, 42 V induction generator scheme at various speeds and loads are presented.

Optimum torque control of permanent magnet AC machines in the field-weakened region

This paper presents a novel current regulation algorithm for permanent-magnet ac (PMAC) machines that provides maximum torque-per-ampere capability in the entire field-weakened region. The algorithm provides robust current regulation with maximum efficiency and torque capability for PMAC machines despite significant changes in the voltage source and machine parameters. The algorithm identifies when the current regulator starts to saturate and determines the optimum d-axis current command for the machine. The q-axis current command is determined from the torque command and d-axis current feedback. When the voltage angle reaches the maximum angle, the current magnitude is decreased to provide maximum torque per ampere. Experimental results from a machine prototype show that the algorithm provides good overall dynamic response and smooth transitions into the field-weakened region with maximum torque-per-ampere capability in all four quadrants of operation.

Current Control of Induction Machines in the Field-Weakened Region

This paper presents a novel current regulation algorithm for induction machines that enables smooth operation and maximum torque-per-ampere capability over the entire field-weakened region. The algorithm enables robust current regulation with maximum torque capability despite significant variation in voltage source and machine parameters. The algorithm identifies when the current regulator begins to saturate and determines the optimum d-axis current command for the machine. The q-axis current command is determined as a function of the torque command and the d-axis current feedback. In the field-weakened region, the q-axis current is monitored not to exceed the maximum q-axis current. The maximum q-axis current is calculated based on the maximum slip frequency, which is a function of rotor frequency, q-axis current ges maximum q-axis current (in motoring mode) indicates that the machine entered field-weakened region II, and the q-axis current is limited to its maximum value. Experimental results from a machine prototype show that the algorithm provides good overall dynamic response and smooth transitions into the field-weakened region with maximum torque-per-ampere capability in all four quadrants of operation

Optimum torque control of induction machines in the field-weakened region

This paper presents a novel current regulation algorithm for induction machines that enables maximum torque-per-ampere capability over the entire field-weakened region. The algorithm enables robust current regulation with maximum efficiency and torque capability despite significant variation in voltage source and machine parameters. The algorithm identifies when the current regulator begins to saturate and determines the optimum d-axis current command for the machine. The q-axis current command is determined as a function of the torque command and the d-axis current feedback. When the voltage angle reaches the maximum allowable angle, the output of the q-axis and the d-axis current regulators are clamped, and the slip frequency that provides maximum torque is maintained. Experimental results from a machine prototype show that the algorithm provides good overall dynamic response and smooth transitions into the field-weakened region with maximum torque-per-ampere capability in all four quadrants of operation

Application of Auto-Coding for Rapid and Efficient Motor Control Development

In hybrid and electric vehicles, the control of the electric motor is a critical component of vehicle functions such as motoring, generating, engine-starting and braking. The efficient and accurate control of motor torque is performed by the motor controller. It is a complex system incorporating sensor sampling, data processing, controls, diagnostics, and 3-phase Pulse Width Modulation (PWM) generation which are executed in sub-100 uSec periods. Due to the fast execution rates, care must be taken in the software coding phase to ensure the algorithms will not exceed the target processors throughput capability. Production motor control development often still follows the path of customer requirements, component requirements, simulation, hand-code, and verification test due to the concern for processor throughput. In the case of vehicle system controls, typically executed no faster than 5-10 mSec periods, auto-coding tools are used for algorithm development as well as testing. The advantages of auto-coding to greatly speed the development process by linking the tools for simulation, code generation and testing early in the development process as well as to more easily investigate performance issues late in the process are well known. It is not uncommon, however, to lose coding efficiency with this approach. While the loss of efficiency may be tolerable for slow periods, it is not acceptable at faster periods used in motor controls as it will preclude the algorithms from executing or drive unnecessarily expensive solutions. This paper will present an auto-coding process applied to motor controls, including full implementation on a production permanent magnet motor drive. Best practices for implementing requirements into models that generate efficient code will be highlighted. An overview of the issues associated with model-based documentation will also be covered. The use of test vectors at the component, model and hardware-in-the-loop (HIL) level will be presented to show the benefits derived from using a formalized process and the natural linkage to a SPICE ® compliant process. A timing study performed during