Dqo Reference Frame Research Articles

Dynamic and steady state modeling of permanent magnet induction machine

PurposeModeling electric machines is one of the powerful approaches for analyzing their performance. A dynamic model and a steady-state model are introduced for each electric machine. Permanent magnet induction machine (PMIM) is a dual-rotor electric machine, which has various advantages such as high-power factor and low magnetizing current. Studying PMIM and its modeling might be valuable. The purpose of this paper is to introduce a simple and accurate method for dynamic and steady-state modeling of PMIM.Design/methodology/approachIn this paper, arbitrary dqo reference frame is used to model PMIM. First, three-phase dynamic equations of stator and rotors are introduced. Then, they are transferred to an arbitrary reference frame. The voltage and magnetic flux equations aligned at dqo axes are obtained. These equations give the dynamic model. To investigate the results, PMIM simulation is performed according to obtained dynamic equations. Simulation results verify the analytic calculations.FindingsIn this paper, dynamic equations of PMIM are obtained. These equations are used to determine dynamic equivalent circuits of PMIM. Steady-state equations and one phase equivalent circuit of the PMIM using phasor relations are also extracted.Originality/valuePMIM equations along dqo axes and their dynamic and steady-state equivalent circuits are determined. These equations and the equivalent circuits can be transformed to different reference frames and analyzed easily.

Grid-forming VSC control in four-wire systems with unbalanced nonlinear loads

A grid-forming voltage source converter (VSC) is responsible to hold voltage and frequency in autonomous operation of isolated systems. In the presence of unbalanced loads, a fourth leg is added to provide current path for neutral currents. In this paper, a novel control scheme for a four-leg VSC feeding unbalanced linear and nonlinear loads is proposed. The control is based on two control blocks. A main control commands the switching sequence to the three-phase VSC ensuring balanced three-phase voltage at the output; and an independent control to the fourth leg drives neutral currents that might appear. The proposed control is noninvasive in the sense that both control blocks are independently implemented, avoiding the use of complex modulation techniques such as 3D-SVPWM. Moreover, the main control is deployed in dqo reference frame, which guarantees zero steady-state error, fast transient response during system disturbances and mitigation of harmonics when nonlinear loads are present. Simulations and experimental results are presented to verify the performance of the proposed control strategy.

Implementation of a New Linear Control Technique Based on Experimentally Validated Small-Signal Model of Three-Phase Three-Level Boost-Type Vienna Rectifier

In this paper, the design and implementation of a new multiple-input-multiple-output linear control technique based on a theoretically established and experimentally validated small- signal model for the three-phase three-level boost-type ac/dc Vienna converter are presented. Averaging and local linearization techniques are used to derive the dynamic model expressed in the dqo reference frame. The resulted transfer functions are discretized for the sake of a digital controller design. Multiple-loop control strategy is adopted and consists of inner current feedback loops, which are based on the straightforward looping technique that neglects interactions between the dq components of control inputs and currents, respectively, and of an outer voltage loop, which is designed to ensure dc voltage regulation by adjusting the magnitude of the references for the inner current loops. The output dc voltage unbalance is also controlled in the inner loops. The proposed modeling and control approaches are first simulated and then validated on a 1.5-kW laboratory prototype supported by the DS 1104 digital real-time controller board of dSPACE. The obtained results prove the accuracy of the proposed new small-signal model and, therefore, its reliability for dynamic analysis and control design purposes. It is also proved that a judicious choice of controller parameters, as well as an adequate rating of boost inductors, allows one to meet the IEEE standard requirements in terms of ac line-current total harmonic distortion and power factor. The efficiency of the proposed control technique is maintained in case of disturbances occurring on both source and load sides.

Control of Single Phase Induction Motor Using Forced-Commutated Electronic Switches and Free-Wheeling Paths

Single phase induction motors show better performance and have less cost if they are controlled using electronic switches instead of mechanical switches. This paper suggests a semiconductor-based method to start the motor and to control the speed and the direction of rotation. This is achieved by feeding the two stator windings of a split-single-phase motor via two forced-commutated solid-state devices. Meanwhile, each winding is shunted by a free-wheeling path that is controlled as well by a forced-commutated solid-state device. Therefore high starting torques and low starting currents are realized. Speed control is easily achieved at higher motor efficiency, compared with the case of controlling the motor using forced-commutated electronic switches without free-wheeling paths. This paper computes detailed performance characteristics of the motor employing the suggested method. For this purpose, the motor is represented in the dqo reference frame. Then, the performance is described by a developed state space mathematical model taking care of the discontinuities introduced by the electronic switches.

Control of Single-Phase Induction Motor Using One-Phase to Two-Phase Solid-State Converter

Most of the single-phase induction motors are started with the aid of auxiliary windings, which need additional electric components and mechanical switches. Speed control through the variation of the stator voltage is done conventionally using expensive electrical equipment. Reversing the direction of rotation imposes the use of the unfavorable mechanical switches. This paper suggests an efficient, cheap, and reliable method to start, control the speed, and reverse the direction of rotation of single-phase induction motors. The method is based on feeding a motor of two symmetrical stator windings through a one-phase to two-phase converter. This converter is constructed of semiconductor devices acting as electronic switches. A rigorous state space mathematical model is developed based on a motor circuit model in the dqo reference frame. The motor is digitally simulated, and complete steady-state and transient performance is presented.

誘導発電機の瞬時値相座標モデルの導出

It is a common practice that the synchronous machines, induction machines and other rotating machines are modeled in dqO reference frame. However, the external network (transmission lines, etc) is mostly modeled in the phase-domain reference frame. Therefore, if a rotating machine can be modeled in phase-domain reference frame, we can construct the electric network model without reference frame transformation. In this paper, we derive the phase-domain model of an induction generator in terms of instantaneous values, and its validity is analyzed based on numerical simulations.

SOLID-STATE CONTROLLED SINGLE-PHASE INDUCTION MOTOR

ABSTRACT Single-phase induction motors are widely used in domestic appliances, workshops and factories. Many conventional methods are used to control these motors. There is no one method by which single phase induction motors can be started, speed-controlled and reversed. This paper presents a new method for controlling single-phase induction motors with two symmetrical stator windings utilizing two triacs; one in series with the main winding and the other with the auxiliary one. Such a connection will perform all the required jobs namely; starting, speed control and reversing the direction of rotation, the motor is represented in the dqo reference frame. A rigorous state space mathematical model is developed to describe the system. Kron's tensor technique is applied using variable connection matrix to care for the nonlinearities introduced by the triacs. Computer results for transient and steady state conditions are presented. Also, the proposed method has been verified experimentally.

Direct phase modelling of synchronous generators

Accurate nonlinear modelling of the synchronous generator in the dqo reference frame has been well documented. To extend the analysis to a wider range of loading conditions, the generator is modelled in the paper in the abc reference frame. The unsaturated, static and dynamic saturated inductances of the machine in this reference frame are obtained using conventional dqo-abc transformation techniques. A new set of equations in the phase reference frame has been derived employing the dynamic inductance concept. The model utilises new dynamic saturated inductances that remove the error present in the conventional direct phase nonlinear model using only static saturated inductances. The mathematical model has been used to simulate the performance of a laminated salient-pole alternator with direct thy-ristor excitation. The predicted results show good agreement with test results.

Time Domain General Model of the Three-Phase Symmetrical Induction Machine–Part II: Model on the dqo Reference Frame

ABSTRACT A model in the time domain, valid for any type of three-phase symmetrical induction machine, is developed. Three, three-phase rotor windings are considered. The possible common electrical path for the double-cage end rings is distinctively included. The machine inductances, in the most general form and within the practical assumptions, are defined. The machine operational equations and the equivalent circuit is presented. The parameters and variables are considered referred to the stator winding, in dqo reference frame, and per units.

Time Domain General Model of the Three-Phase Symmetrical Induction Machine–Part I: Model on the Phase Reference Frame

ABSTRACT A model in the time domain, valid for any type of three-phase symmetrical induction machine, is developed. Three, three-phase rotor windings are considered. The possible common electrical path for the double-cage end rings is distinctively included. The machine inductances, in the most general form and within the practical assumptions, are defined. The machine operational equations and the equivalent circuit is presented. The parameters and variables are considered referred to the stator winding, in dqo reference frame, and per units.

Electromagnetic Forces on the End Windings of Large Turbine Generators. II. Transient Conditions

A companion paper has explained the basic concepts of end winding forces during steady state, and has given examples of the variation of force with power factor [1]. The present paper extends the analysis to transient operation. The fields and currents are represented in the dqo reference frame. The fields are then projected onto the coil zones, and the cross product is taken in order to find the force. Several examples are given in which the instantaneous force is calculated.

Electromagnetic Forces on the End Windings of Large Turbine Generators. II. Transient Conditions

A companion paper has explained the basic concepts of end winding forces during steady state and has given examples of the variation of force with power factor(1). The present paper extends the analysis to transient operation. The fields and currents are represented in the dqo reference frame. The fields are then projected onto the coil zones, and the cross-product is taken in order to find the force. Several examples are given in which the instantaneous force is calculated.