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In sensorless induction motor drives, the stator model is always used to estimate the stator flux because it does not require a speed signal. Combined with the stator model, stator field orientation control strategies are preferred in implementation. In these strategies, direct torque and flux control based on space-vector modulation (SVM-DTC) is the one with good performance. It produces fast torque...
Three-phase coupling transmission line equation is derived from the distributed-parameter circuit model and telegraph equation in this paper. According to the theoretical analysis, a novel shunt filter design approach is proposed to mitigate motor terminal overvoltage caused by voltage reflection in pulse width modulation (PWM) inverter-fed AC motor drive systems with long three-phase coupling cable...
The conventional Modular Multilevel Convertor (MMC) couldn't operate in low frequency for high voltage motor drive, because of the cell capacitor voltage fluctuation increasing severely with frequency decreasing. This paper presents a new back-to-back topology of MMC with auxiliary voltage clamping circuit for motor drive. The auxiliary circuit use soft-switch strategy to transfer energy between the...
This paper presents a new integration algorithm for stator flux estimation based on voltage model. This algorithm is composed of a second-order band pass filter (BPF) and a component which can effectively compensate magnitude and phase angle errors between the BPF and ideal pure integrator. The effect of the poles location of the BPF is studied, and the poles are located adaptively according to the...
By now the modular multilevel converter (MMC) is mainly applied to high frequency applications (50 or 60Hz) especially in the field of HVDC systems. This paper presents a control scheme for modular multilevel converter, which allows the converter to operate at continuous coverage in the 0Hz to 50Hz frequency band.
Three-level neutral point clamped voltage source converter (NPC VSC) is widely used in high-power high-voltage applications. The main drawback of unequal loss distribution among the semiconductors of NPC VSC is overcomed by using active NPC (ANPC) VSC. The ANPC VSC can provide more commutations than NPC VSC and increase the maximum output power or the converter output frequency. In this paper, based...
A novel single-phase five-level rectifier with coupled inductor has been proposed. Detailed analysis of this new circuit structure and working principle has been made. Modulation strategy and control strategy of this circuit topology have been given. This new topology has unity power factor operation, low input current total harmonic distortion, stable output DC bus voltage, and no voltage balancing...
Based on a novel multilevel voltage source converter (VSC) used for electric drive, the pre-charging process of the converter is fully analyzed, so as to find a suitable pre-charging control strategy. For a single converter with redundant modules, the process is divided into two stages, the unlock charging course is in particular analyzed. To ensure the normal operation of the converter, an optimized...
In high power traction systems, indirect field oriented control is widely used due to its simplicity and robustness in implementation. The main drawback of IFOC is that motor's parameter deviation during operation will cause the detuning of the flux orientation and undermining the control ability of motor magnetizing and torque. A new auto online tuning method is proposed based on comparison between...
A modified algorithm for estimating motor flux based on the stator model are proposed in this paper. This algorithm is effective to solve the problems associated with the integration of the back electromotive force (emf), and can be used in sensorless ac motor drives over a wide speed range. The effect of parameters used in this algorithm is studied and the parameters are all assigned to appropriate...
It is well known that commonly used neutral-point clamped (NPC) three-level inverter modulation schemes generate common-mode voltages. Common-mode voltages may cause motor shaft voltages and bearing currents and electromagnetic interference (EMI). Therefore, it is important to reduce the common-mode voltage in power converter, especially at high voltage with large capacity. This paper introduces a...
This paper analyses the reason of module capacitor voltage fluctuation when the Modular Multilevel Convertor (MMC) provide low frequency output voltage to motor. In order to restrain the voltage fluctuation, appropriate values of the arm inductor and the cell capacitor must be chosen. Furthermore, the common voltage is added in output AC phase voltage and the corresponding inner current in the arms...
This paper proposes an effective space vector modulation method for three-level NPC rectifiers meanwhile proposes realated methods to reduce switching losses, to control neutral point voltage and to meet the minimum pulses requirement. Different switching sequences are explored in detail and their best arrangements are proposed to make the output waveform half-symmetrical and minimize the switching...
A novel single-phase nine-level converter based coupled inductor has been proposed. Detailed analysis of this new circuit structure and working principle has been made. This new topology based on diode clamp three-level structure increases two switching devices and a coupled inductor and the voltage level rises from five to nine. This new topology also has unity power factor operation, stable output...
Voltage-source converter (VSC) is has been applied widely in feeding the induction motor(IM). In high power wide speed-range AC drive, such as High Speed Railway Train traction converters, the IM usually are fed by Single Wave (SW) voltage in high speed reign, due to the switching loss and making full use of the voltage that DC link can provide. The amp1itude of stator voltage vector is restricted...
With the development of high power devices, Hardware in loop simulation is widely applied to power electronics to test the performance of control system. This paper describes a simulation method on basis of RT-LAB platform to test the controller of long-stator linear synchronous motor(LLSM). Three-level converter model and the dynamic mathematical model of LLSM are built in MATLAB/Simulink, after...
The influence of cross coupling effect on the performance of the indirect rotor field oriented control (IFOC) for high power AC traction drives cannot be neglected due to the wide operation range, low switching frequency and so on. In this paper, the cross coupling problem between d and q axis current component in the IFOC scheme is discussed. An improved current regulation scheme is proposed based...
A high performance controller with effective voltage balance regulation is proposed for a cascade STATtic synchronous COMpensator(STATCOM) with star configuration. Zero-sequence voltages are injected to the output voltages of STATCOM in order to compensate the unblanced load currents, which can also decouple the star-connected three-phase STATCOM system into three single-phase systems. Additionally,...
The common mode current of upper arm and lower arm in a modular multilevel converter (MMC) can be divided into two parts: a DC component and an AC component which is called the circulating current. The circulating current will increase power losses and may threaten the safe operation of the power devices and capacitors. To solve this question, this paper analyses the harmonics of the circulating current...
This paper describes the operation of modular multilevel converter (MMC). A control method of adding the feed-forward current is introduced. Another strategy of removing the second harmonic current is also described in order to improve the arm currents. Simulation results based on a detailed PSIM model prove the effectiveness of the two methods. The paper presents principle of parameters selection...
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