A Single-Phase Rectifier Having Two Independent Voltage Outputs With Reduced Fundamental Frequency Voltage Ripples

Abstract

Half-bridge rectifiers are able to provide two voltage outputs, which offers three voltage levels, but the two voltage outputs depend on each other and also on system parameters. Moreover, the two voltage outputs contain large ripples because the currents following through the split capacitors contain significant fundamental-frequency components. In this paper, after analysing the drawbacks of half-bridge rectifiers in detail, an independently controlled neutral leg is added to conventional half-bridge rectifiers to address these drawbacks. Furthermore, the associated decoupling control strategies are proposed. The rectification leg from the conventional half-bridge rectifier is controlled to maintain the DC-bus voltage and to draw a clean sinusoidal current that is in phase with the supply voltage. The neutral leg is controlled with a PI-repetitive controller to regulate one voltage output and also to provide the current path for any DC and/or fundamental-frequency components. As a result, the two voltage outputs are regulated independently and are robust against system parameters. The output voltage ripples are also reduced and, hence, the required capacitance to achieve the same level of voltage ripples is reduced. Experimental results are provided to validate the performance of the proposed singlephase rectifiers having two independent voltage outputs.

Reducing the Inductors of Rectifiers Having Two Outputs to Improve Power Density

“…Same as the conventional RECTO proposed in [6] and [16], the improved RECTO also has two legs, i.e., the rectification leg and the neutral leg. Instead of connecting the neutral line N to the midpoint of the split capacitors, as shown in Fig.…”

“…Three loads R, R + , and R − can be operated at the same time. Since the two dc outputs are independent from each other, there are no restrictions on the ratio among the loads, which means the loads can be the same or different, as the conventional RECTO proposed in [6] and [16]. The two legs are still operated independently from each other.…”

“…where V g , I g , and ω are the peak value of the grid voltage, peak value of the grid current, and the angular line frequency, respectively. Following the procedures mentioned in [2], [6], and [7], the average circuit model of the improved RECTO can be built, as shown in Fig According to the average circuit model, the equivalent circuit of the improved RECTO in voltage sources are shown in Fig. 6.…”

“…One application for such rectifiers is to provide two independent dc outputs from one ac input. For example, many electronic systems need positive and negative dc power suppliers at the same time [6]. As a popular solution, half-bridge rectifiers are very attractive because they can provide two dc voltage outputs at relatively low costs [7].…”

“…However, this could lead to significantly reduced power density, which is unacceptable for volume-critical and/or weight-critical systems like electrical vehicles and aircraft power systems [12]- [15]. As reported in [6] and [16], the single-phase rectifier with two outputs (in short, RECTO, for simplicity) shown in Fig. 2, which is formed by adding an independently controlled neutral leg [1], [17], [18] into conventional half-bridge rectifiers, was proposed to overcome the two aforementioned drawbacks.…”