The windup phenomenon appears and results in performance degradation when the proportional-integral-derivative (PID) controller output is saturated. Integral windup is analyzed on the PI plane, and a new anti-windup PID controller is proposed to improve control performance of variable-speed motor drives and is experimentally applied to the speed control of a vector-controlled induction motor driven by a pulse width-modulated voltage source inverter. The steady-state value of the integral state is predicted while the PID controller output is saturated, and this value is utilized as an initial value of the integral state when the PID controller begins to operate in a linear range. Simulation and experiments result in more similar speed responses against load conditions and step reference change over conventional anti-windup schemes. Control performance, such as overshoot and settling time, is very similar to that determined by PID gain in the linear range.

Anti-Windup PID Controller With Integral State Predictor for Variable-Speed Motor Drives

This paper deals with the current state-of-the-art in interfacing issues related to real-time digital simulators employed in the simulation of power systems and power-electronic systems. This paper provides an overview of technical challenges encountered and their solutions as the real-time digital simulators evolved. Hardware-in-the-loop interfacing for controller hardware and power apparatus hardware are also presented.

Interfacing Issues in Real-Time Digital Simulators

This paper proposes a novel antiwindup method of current regulator for the drive system of a surface-mounted permanent-magnet synchronous motor at flux-weakening region. It is designed in conjunction with the synchronous-frame proportional and integral current regulator and the space vector pulse width modulation. The difference between the regulator output voltage and the saturated voltage on the q-axis of the regulator is used for flux-weakening control, which modifies the d-axis current reference. With this method, the antiwindup and the flux-weakening control can be achieved simultaneously. Since the proposed method utilizes the dc-link voltage more efficiently, it makes the motor generate higher output torque than the conventional antiwindup and/or flux-weakening control methods under the same voltage and current limitation. The effectiveness of this method is confirmed by computer simulations and experiments

Novel anti-windup of a current regulator of a surface-mounted permanent-magnet motor for flux-weakening control

In a power converting apparatus which converts AC power into DC power, an inverter circuit including at least one series-connected single-phase inverter is connected in a downstream of a stage in which an AC input is rectified in series therewith. In the downstream stage of the inverter circuit, there are provided a smoothing capacitor connected via a rectifier diode and a short-circuiting switch for bypassing the smoothing capacitor. The short-circuiting switch is set to an ON state only in each of short-circuiting phase ranges of which midpoint matches each of zero-crossing phases and an output of the inverter circuit is controlled by using a current command so that a DC voltage of the smoothing capacitor follows a target voltage and an input power factor is improved.

Power converting apparatus

A power conversion device includes a power switching circuit that supplies AC voltages generated between switching elements operating as upper arms and switching elements operating as lower arms, and a control circuit that generates and supplies to the driver circuit signals for controlling the switching operation of the switching elements by a PWM method in a first operational region in which frequency of an AC power to be outputted is low, and that generates and supplies to the driver circuit signals for controlling the switching operation of the switching elements at timings based upon the phase of the AC power to be outputted in an operational region in which the frequency of the AC power to be outputted is higher than in the first operational region.

Power Conversion Device

Generally, a speed servo system of a vector-controlled induction motor has limitations of motor voltage and current. When the speed servo system has a large torque reference, the output of its PI controller is often saturated. In this case, the conventional servo system stops the integral calculation of its PI controller. However, this system often has a large overshoot and/or an oscillated response caused by both a windup phenomenon and phase error on the vector control condition. This paper proposes a new speed servo system considering voltage saturation for the vector-controlled induction motor. The proposed control method compensates the phase error on vector control condition quickly, and always keeps the vector control condition. The experimental results show that the proposed system well regulates the motor speed and the secondary magnetic flux for a large torque reference without a windup phenomenon.

High-performance speed servo system considering Voltage saturation of a vector-controlled induction motor

The present invention provides a position control unit having a torque command computing device (a position control circuit, and a speed control circuit) for outputting a torque command signal (q-axis current command signal Iq*) according to a positional command signal θm* given from the outside and a positional detection signal θm for an electric motor, and a torque control device (current control circuit) for controlling a torque of the electric motor according to a torque command signal outputted from the torque command computing device, in which the torque control device selects a gain Kqp or a gain Kqi according to whether an absolute value of a positional deviation between the positional command signal θm* and the positional detection signal θm is larger or smaller than a gain switching reference value P for a positional deviation.

Position control unit for electric motor

There is provided a controlling device for an AC motor having a structure in which a current of a three phase brushless DC motor is detected and then converted to a rotor coordinate system, to separately control a torque split current (q axis) and an exciting split current (d axis), wherein an offset is estimated with a DC component of a multiplied value of the values corresponding to a d axis voltage command which is an output of an exciting split current controller and an electrical angle, and the detected current is compensated for, so that an offset of a current detector may be estimated and compensated for during its operation without stopping its rotation and the motor can rotate smoothly without a torque ripple, even in the case in which the current detector has an offset error or in the case in which an offset changes due to a temperature drift.

Controller for ac motor

Speed Servo System Considering Voltage Saturation of Indiredt Vector Control System

This paper presents real-time simulation results of a Permanent Magnet Synchronous Machine (PMSM) Drive in faulty and non-standard modes and validates these against an actual industrial PMSM drive system. The paper will put emphasis on the test of special and faulty modes in PMSM drives. Results of real-time simulation of a PMSM drive with an open phase and in passive mode (with all IGBTs switched off) will be presented. These working modes are usually difficult to simulate in real-time because of the fixed-causality models used in the real-time simulator.

Tetsuaki Nagano

Papers

High-performance speed servo system considering Voltage saturation of a vector-controlled induction motor

Position control unit for electric motor

Controller for ac motor

Speed Servo System Considering Voltage Saturation of Indiredt Vector Control System

Real-time simulation of a PMSM drive in faulty modes with validation against an actual drive system