Ma Weiming

A New Critical Formula and Mathematical Model of Double-Tap Interphase Reactor in a Six-Phase Tap-Changer Diode Rectifier

This paper presents a new practical formula to calculate the critical value of interphase reactor (IPR) in a six-phase diode rectifier with tap-changer. In addition, a mathematical model of the double-tap IPR has been established by equivalent circuit method. Simulation and experimental results verify the validity of the formula and mathematical model. On the basis of the above achievements, a simple and effective approach is provided to design the IPR and to analyze the performance of the whole system

Stability of a synchronous generator with diode-bridge rectifier and back-EMF load

An equivalent circuit model of a synchronous generator with diode-bridge rectifier and back-EMF load is presented in this paper. The principle of harmonic balance is applied, which makes it possible to construct a state-space mathematical model for the system. The criterion of stability is obtained for the system under small disturbances. This stability criterion is more accurate than that presented in the existing literature. It is shown that the systems stability can effectively be improved by installing a short-circuited quadrature-axis winding on the machine rotor.

Steady-state performance of synchronous generators with AC and DC stator connections considering saturation

Synchronous generators with ac and dc stator connections are widely used in systems where simultaneous ac and dc power supplies are needed. For these systems the voltage harmonic distortion of ac voltage, dc voltage ripple, and dc voltage varying range are of special interest. Because of the commutation of rectifier and the saturation of magnetic circuit, the accurate calculation of voltage harmonic distortion and dc voltage varying range is comparatively difficult. This paper describes a mathematical model on the basis of the multiloop method and FEM, which aims at calculating the steady-state characteristics and the voltage waveforms of ac winding accurately. With this method, the full synergic effects of space harmonics resulting from the magnetic circuit geometry, saliency, saturation, winding layouts, and slotting are included. The calculated results are compared with those of experiments.

Simulation and operational protection of three-phase/twelve-phase hybrid AC-DC supply generator system

The hybrid AC-DC supply has been applied to various situations. It provides simultaneous AC and DC power with least weight, volume and cost to meet the special requirement of mobile power networks. In this paper, a mathematical model, based on the multiloop method, including speed regulator and excitation regulator, is established to reflect the system operation aspect. The simulation results of voltage harmonics are compared with experiments to verify the validity of the mathematical model. The DC side power oscillation and short circuit may result in system breakdown. The simulation program provides the guideline for system operation and protection. The simulation results showed the factors that affect the amplitude and frequency of the DC side power oscillation. The q-axis winding and feedback control of the DC load current on the excitation voltage can increase system stability. The DC side short circuit currents are also calculated for the tuning of the relays.

Different mode conducted EMI of three-phase SCR rectifier: prediction and reduction

This paper analyzes the EMI that is generated from a three-phase SCR rectifier and the effect of some common reduction measures. According to the switching function, the noise equivalent circuit is obtained. Based on these equivalent circuits, the noise spectrum calculation can be performed in the frequency-domain. The experiment results show the validity of the calculation. Since the calculation is in the frequency-domain, it does not need many parasitic parameters and the calculation time can be greatly decreased compared with time-domain simulation.

Parameter measurement of multi-phase synchronous machines with AC and DC output

Many self-contained electrical systems require simultaneous AC and DC power supply. The hybrid AC-DC supply generator (HADSG) is a good solution. Several independent Y-connected windings are equipped on the stator of HADSG, one delivers AC power and the others, termed DC windings, are connected to the bridge rectifier. Methods of parameter measurement considering DC winding resistances are presented for a typical HADSG with a 12-phase DC winding in this paper. The d-axis self and mutual reactances can be acquired by various short-circuit tests for one or two three-phase windings. Relevant formulas are derived for calculating the d-axis parameters through measuring the short-circuit currents and voltages of all open three-phase windings. According to the voltages and currents measured in slip-tests for AC and DC windings, the q-axis self and mutual reactances can be obtained. Using these reactances in the simulation program, the simulation and test results agree quite well.

Modeling and simulation of conducted electromagnetic emissions prediction in AC generator rectifier systems

This paper presents a new approach for modeling and simulation of conducted EMI prediction for widely used AC generator-rectifier systems. The mechanism of conducted EMI associated with a typical generator-rectifier system is analyzed. A high-frequency model of the generator is established. The system is simplified by a resonant circuit including the dominant stray distributed parameters. The conducted EMI of an actual system is investigated using time domain simulation. The validity of the models is confirmed by comparison to the laboratory measurements.

Modeling and simulation of 3-&3-phase AC-DC integrated synchronous generators

The simplified mathematical model and corresponding equivalent circuits for simulation of the 3-&3-phase AC-DC integrated synchronous generator (ADISG) are presented. A sudden simultaneous AC and DC short circuit is simulated. The simulation and test results agree quite well, showing the validity of the mathematical model and the method of simulation. The approach proposed is suitable for other ADISGs such as 3-&6-phase, 3-&9-phase, 3-&12-phase ADIGs, etc.

Subtransient parameters measurement of hybrid AC and DC integrated machines

Many self-contained electrical systems require simultaneous AC and DC power supply. The hybrid AC-DC integrated generator (HADIG) is a good solution. A 3-phase winding and a multi-phase winding set are installed on the stator of the machine, the former delivers AC power and the latter, termed DC windings, are connected to the bridge rectifier. In this paper, methods of subtransient parameters measurement considering stator resistances are presented for a typical HADIG with a 12-phase DC winding. Validity of the methods developed are examined on a realistic machine.

Research on voltage harmonic distortion of synchronous generators

This paper investigates the effects of the parameters as well as the operating conditions on the waveform and the harmonic analysis of AC voltage. On the basis of the multi-loop method and FEM, a mathematical model of synchronous generators is described. With this method, the full synergic effects of space harmonics resulting from the magnetic circuit geometry, saliency, saturation, winding layouts, and slotting are included. The calculated results are compared with those of experiments.