Pulse-width Modulated Current-source Rectifiers Research Articles

Grid Harmonics Compensation Using High-Power PWM Converters Based on Combination Approach

For high-power pulsewidth modulation (PWM) converters, selective harmonic elimination (SHE) modulation scheme is commonly adopted to reduce the low-order harmonics caused by a low switching frequency. However, the SHE scheme itself lacks the capability to actively compensate the grid background harmonics. To enable the active compensation ability of the SHE-modulated PWM converters, a selective harmonic compensation scheme and an SHE phase jittering method have been proposed in the previous works, and their effectiveness to actively attenuate the one grid line current harmonic was verified on a high-power PWM current-source rectifier (CSR) system application. Nevertheless, both the two methods have difficulty in compensating two harmonics simultaneously, which limits their applications with a low resonant frequency of converter system's filter circuit. This paper extends the previous studies to enable the high-power PWM converters to actively compensate two grid background harmonics. The proposed method can not only further reduce the grid line current distortion but also make the application of the active compensation no longer limited by the filter circuit. The experimental results of its application on a high-power PWM CSR system are provided to verify the effectiveness.

An Active Damping Method Using Inductor-Current Feedback Control for High-Power PWM Current-Source Rectifier

Due to the inductor-capacitor filter, a pulse width modulation current-source rectifier (CSR) may experience LC resonance. A smaller ratio between the switching frequency and the resonant frequency of the CSR presents a challenge in designing active resonance damping methods in high-power applications. In this paper, different feedback states of filter inductor current and capacitor voltage are investigated to damp out the LC resonances. Besides proportional capacitor-voltage feedback (CVF), the derivative inductor-current feedback (ICF) provides an alternative approach for active damping and is comprehensively analyzed. Compared with the virtual-resistance (VR)-based active damping strategy, controller design is simpler in this method. Furthermore, the active damping method is able to damp the resonance under short-circuited dc-link conditions. The ICF-based active damping strategy works well for CSRs with low switching frequencies. Simulation and experimental results verify the feasibility and validity of the method.

Current-source-rectifier topologies for sinusoidal supply current: theoretical studies and analyses

For current-source-rectifier (CSR)-based systems, sinusoidal supply current and unity displacement power factor in the utility are achieved through either a pulsewidth-modulation CSR or a phase-controlled rectifier in conjunction with an active filter. This paper investigates theoretical studies and analyses for the two topologies from the standpoint of converter kilovoltampere rating and switch rating.

Input Filter Design for PWM Current-Source Rectifiers

Pulse-width modulated (PWM) rectifiers are increasingly used because they allow the elimination of low-order harmonics, and therefore a reduction in input filter components. Filtering requirements for PWM current-source rectifiers are usually satisfied through the use of low-pass LC input filters. This paper offers a systematic and user-friendly approach to choosing the filter components. Design of LC filters involves the positioning of the resonant frequency to meet the harmonic attenuation requirements (THD), and introducing damping at the resonant frequency to avoid amplification of residual harmonics. The problem is further complicated by considerations related to cost, power factor, voltage attenuation, system efficiency, and filter parameter variation. The systematic approach proposed in this paper focuses on PWM rectifiers, but can easily be extended to other classes of converters. Practical design considerations are detailed and design equations derived. Simulated results are presented to validate the design approach