Negative impedance converter

About: Negative impedance converter is a research topic. Over the lifetime, 5801 publications have been published within this topic receiving 87636 citations.

Three-phase AC-to-AC series resonant power converter with reduced number of switches

Abstract: An apparatus and method is disclosed for an improved AC--AC series-resonant converters incorporating power pulse modulation with internal frequencies of tens of kHz is applied to a series-resonant converter system for generating synthesized multiphase bipolar waveforms with reversible power flow and low distortion. The high pulse frequency allows the application of the principle of modulation and demodulation for fast system response. Switches are required which have bidirectional current conduction and voltage blocking ability. The conventional series-resonant AC--AC converter applies a total of 24 anti-parallel thyristors. The circuit configuration of the present invention is a series-resonant AC--AC converter with only 12 thyristors. Use of the converter results in a higher efficiency and lower costs. The alternative power circuit has three neutrals, related to the polyphase source, the load and the converter, which may be interconnected and the high-frequency component of the source and load currents will flow through the connection between the neutrals.

A single-switch high gain quadratic boost converter based on voltage-lift-technique

Abstract: In this paper, based on the traditional voltage-lift-technique, a modified voltage-lift cell is proposed. A single-switch high gain quadratic boost converter is obtained by applying the modified voltage-lift cell to quadratic boost converter, the voltage gain of the converter is improved and the switch voltage stress of the converter is also reduced. The operation principle of the quadratic boost converter with modified voltage-lift cell is analyzed. Compared with quadratic boost converter and the other single-switch high gain boost converter, the voltage gain of quadratic boost converter with modified voltage-lift cell is highest, and the switch voltage stress of quadratic boost converter with modified voltage-lift cell is lowest. Experimental results are presented to verify the theoretical analysis results.

Voltage Stability Analysis and Sliding-Mode Control Method for Rectifier in DC Systems With Constant Power Loads

Abstract: Voltage stability draws more and more attentions in dc systems due to the high penetration of constant power loads. This paper gives comprehensive analysis for the voltage stability and proposes a sliding-mode control method to enhance the voltage stability margin of dc systems. First, by the impedance-based stability analysis approach, the voltage stability of the three-phase rectifier serving as the source converter is examined when interacted with tightly regulated load converter. The dynamic input characteristics of the load side converter are investigated to find the relationship between the negative incremental impedance and the output power of the load converter. Second, a new sliding-mode control method is proposed to achieve the large-signal stability. Lyapunov function is used to ensure the stability of the proposed controller. Finally, the effectiveness of the proposed control method is verified by simulation results.

On the anomalous peak and negative capacitance in the capacitance–voltage (C–V) plots of Al/(%7 Zn-PVA)/p-Si (MPS) structure

Abstract: The frequency and voltage dependence of the capacitance–voltage (C–V) and conductance–voltage (G/ω–V) characteristics of the Al/(%7 Zn-doped PVA)/p-Si (MPS) structure were investigated in the wide range of frequency and voltage. Frequency and voltage dependence of C and G/ω shows that these parameters are functions of frequency and voltage. The C–V plot has an anomalous peak and an intersection/crossing point around 1.4 V after which C becomes negative. This negative capacitance (NC) phenomena was attributed to the surface states (Nss), series resistance (Rs) and minority carrier injection. The intensity of NC decreases with increasing frequency and the minimum value of C corresponds to the maximum value of G/ω at strong accumulation region. Whereas the C–V plots have only one peak at low frequencies, they have two peaks at high frequencies due to the special density distribution of Nss and their relaxation time. In addition, the changes in the C and G/ω were attributed to the increase in the polarization and the increased number of carriers in the structure. Impedance method was used for calculation of Rs whereas Nss was obtained using two methods; (i) the high–low frequency capacitance and (ii) Hill-Coleman method as a function of voltage and frequency, respectively. The Fermi energy level (EF), the concentration of doping acceptor atoms (NA) and barrier height (ΦB) values were obtained from reverse bias C−2 vs V plots for each frequency.