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A novel switching table of direct power control (DPC) strategy for three-level NPC rectifier is proposed in this paper. With the theory of instantaneous reactive power, it gets the inner relationship between instantaneous power (active power and reactive power) and space voltage vectors. The dc-link voltages are maintained at the required level using hysteresis controller for the NP current exploiting...
A novel switching table of direct power control (DPC) strategy for three-level NPC rectifier is proposed in this paper. With the theory of instantaneous power, it gets the inner relationship between instantaneous power (active power and reactive power) and space voltage vectors. The dc-link voltages are maintained at the required level using hysteresis controller for the NP current exploiting the...
For high power three-level Neutral Point Clamped (NPC) converter widely used in medium voltage speed regulation system, which has the characteristics of low switching frequency and complex harmonic distribution of output current waveform, output filter is needed in order to protect AC-side device. Normally, LC filter is used for its good performance. However, the low switching frequency and complex...
A novel carrier-based modulation strategy of NPC three-level converter which achieves neutral point voltage balance under the whole modulation index and power factor is proposed in this paper. It divides the traditional single modulation wave of each phase in SPWM strategy into two modulation waves, which are compared respectively with the carrier to decide the output switch state of the converter...
For high power three-level NPC grid connected inverter, which has the characteristics of low switching frequency and complex harmonic distribution of output current waveform, it deduces the total output filter inductor expression and researches the relational expression between inductance ratio, damping ratio and resonant frequency, harmonic attenuation ratio, as well as damping power. Based on this,...
In this paper, four kinds of multicarrier PWM strategies used in three-level converters which are called PD-PWM, POD-PWM, COPWM-A and COPWM-B are evaluated in three aspects: influence of the neutral point (NP) potential fluctuation, fundamental amplitude and THD performance of output waveform. The analysis shows that: 1) Comparing with PD-PWM and POD-PWM, CO-PWMA and CO-PWMB have smaller NP potential...
Parameter identification of an induction motor (IM) at standstill based on Recursive Least Squares (RLS) essentially requires the derivative terms of the stator voltages and currents. However, the use of the analog or digital differentiators will greatly increase the complexity of identification algorithm and reduces the system reliability. In this paper, a simple parameter identification algorithm...
This paper presents the analysis, control strategy and realization of a digital frequency controller of a two stage ballast for HID Lamps. First, the small signal phasor model of the LCSCP resonant inverter is established and verified. Based on this model, a double loop digital compensator is designed to control the current and power of the lamp. Then the overall control strategy for the long term...
For speed sensorless stator-flux-oriented control (SFOC), the accuracy of the estimated flux position decides the performance of the speed sensorless drive. In this paper, a novel flux estimation method is proposed in which the pure integrator is replaced by a low pass filter (LPF) to resolve the DC-drift and saturation problem and the phase error with the LPF is approximately compensated by the reference...
Multiphase motor drives have many advantages over the traditional three-phase motor drives. In this paper we firstly deduce the mathematic modeling for a dual-three-phase permanent magnet synchronous motor (PMSM) according to vector space decomposition theory. Then, a sensorless vector control based on the model reference adaptive system (MRAS) is developed for a dual-three-phase PMSM and the system...
The large capacity harmonic current generator based on three-phase-four-wire configuration uses four-leg converter as its main circuit. So it is different from the traditional small capacity linear current source. The whole equipment can output steady harmonic current include the selective order harmonic (below 25th order), reactive current and unbalanced current. Besides, dynamic change process of...
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