Current Regulation Loop Research Articles

High-performance flux-based two-degrees-of-freedom uninterruptible power supply

A three-phase flux-based two-degrees-of-freedom uninterruptible power supply with improved voltage regulation performance is presented. The proposed AC supply is controlled using an outer P+resonant voltage regulation loop to nullify voltage tracking errors and compensate for unbalanced voltages. Within this outer voltage loop is a flux-based two-degrees-of-freedom inner current regulation loop for the fast compensation of dynamic load changes and other external disturbances. This inner current regulator originates from the combined use of classical two-degrees-of-freedom control theory and a hysteretic flux modulation technique. By integrating the individual advantages of P+resonant compensators, two-degrees-of-freedom control and flux modulation, the proposed AC supply can achieve both precise steady-state tracking and a fast transient response. Theory and experimental results are presented to validate the performance of the proposed AC supply.

The Use of Real-World Computer Models for Computer-Aided Design of Tracking Control Schemes for Induction Motors

The design of tracking controllers for induction motors is usually developed by neglecting the presence of power-supply devices, such as inverters, and measurement apparatuses, e.g., encoders. However, these components represent unmodeled dynamics that are present during the real operating conditions of the induction motor. Since the development of a numerical simulation study represents a low-cost, safe, and fast test to validate the design of tracking control schemes, the need arises to build a computer model of the overall system (i.e., motor, power supply, measurement devices, and tracking controller) as realistic as possible. In this context, the paper describes a computer model for simulation of an induction motor under a tracking control scheme including many real-world effects; namely, encoder's quantization, current sensors' noise, stator current dynamics, presence of a current-controlled voltage-source inverter within a stator current regulator loop, flux observer dynamics, saturation of the control signal, and discrete-time implementation of the control algorithm. The developed computer model is finally used in a case study and the simulation results obtained for an induction motor driving a single-link robotic arm under an H8 tracking control scheme are reported.

New inverter output filter topology for PWM motor drives

This paper presents a new inverter output filter topology for pulse width modulation (PWM) motor drives. It is shown that the proposed filter effectively reduces high frequency harmonics which can cause serious damage to the motor bearings and insulation. The proposed filter is comprised of a conventional resistance, inductance, capacitance (RLC) network cascaded with an LC trap filter. The LC trap, tuned to the inverter switching frequency, is very effective in reducing the switching harmonics. By using this new topology the need for high damping resistance and low RLC cut-off frequency is eliminated. This reduces the phase shift in the current regulation loop and increases the filter efficiency. Experimental verification of the filter topology is provided with a 180 V inverter and a 25 hp permanent magnet synchronous motor. Space-vector predictive current regulation is implemented as an inner-loop current regulator for the outer-loop speed control using a digital signal processor. The effectiveness of the filter at different motor speeds is presented.

A constant air flow rate control of blower for residential applications

This paper presents a technique to control a blower for residential applications at constant air flow rate using an induction motor drive. The control scheme combines a variable volt/hertz ratio inverter drive and an average motor current regulation loop to achieve control of the motor torque-speed characteristics, consequently controlling the air flow rate of the blower which the motor is driving. The controller is simple to implement and practical for commercialization. It is also reliable, since no external pressure or air flow sensor is required. Both a theoretical derivation and an experimental verification for the control scheme are presented in this paper.

Application of an extended Kalman filter for high-performance current regulation of a vector-controlled induction machine drive

Variable frequency AC drives using voltage-source inverters to supply induction motors are increasingly used in industry for high-performance speed response. Such a drive usually employs a vector-controller at the outer speed-loop which will generate the required torque-current signal. An inner current control loop is incorporated to ensure that an appropriate reference current is impressed on the stator circuit. However, due to nonlinearity and time varying characteristics of the machine circuit, a fixed-parameter regulator cannot give good current control performance in the transient state. The paper presents a model-based predictive current regulator for a vector-con trolled induction motor drive. An extended Kalman filter is employed to estimate the back-EMF of the machine stator circuit model used by the inner current regulator loop. This also estimates the rotor resistance for slip angular velocity calculation in the outer speed-loop. The adaptive feature of this controller leads to improved speed-response performance from the induction machine.

The design and implementation of a three-phase active power filter based on sliding mode control

This paper presents an active power filter for three-phase power systems. The work is motivated by the need for active filtration in a current-source excitation system for a variable-reluctance generator. The active filter is comprised of a six-switch three-phase inverter, a DC bus capacitor, and an isolation transformer. The isolation transformer is required by the application. The leakage inductance associated with each phase of the isolation transformer is used as the series impedance with each phase, by which the inverter is able to actively shape the phase currents in order to compensate for the nonlinearities of all loads within the point of common coupling. The active filter is controlled through two control loops. The inner current regulation loop uses sliding-mode control by virtue of its ease of implementation. The outer voltage loop regulates the average voltage on the DC bus capacitor. The outer voltage loop is responsible for correctly setting the commanded magnitude of the phase currents. This paper presents the analysis, design, and operation of the active filter. Experimental results are provided for the active filter compensating a phase-controlled rectifier which is drawing 10.4 kW. >

Design and Performance of PEP DC Power Systems

The PEP Magnet Power Supply System represents a significant departure from previous technology with the goal of improved performance at lower cost. In nineteen of the magnet families around the ring, Chopper power supplies are used. The many choppers are powered from two 2 MW dc supplies, and control the average power to the various magnet loads by pulse-width modulation at a 2 kilohertz repetition rate. Each chopper utilizes SCR's for switching, and stores sufficient capacitive energy for turn-off on command. Most of the energy is recirculated, resulting in high-efficiency. The two kilohertz chopping rate allows a one kilohertz unity-gain bandwidth in the current-regulator loop, and this wide bandwidth, coupled with low drift components in the error-detection system, provides a high-performance system. The PEP system has also shown that the chopper system is economical compared to standard multi-pulse controlled-rectifier.