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.

Ripple Mitigation With Improved Line-Load Transients Response in a Two-Stage DC–DC–AC Converter: Adaptive SMC Approach

Abstract: A substantial pulsation of the second-order harmonic current ripple with angular frequency $2\omega$ is reflected at the input of a single-phase inverter when loads are supplied at its output with angular frequency $\omega$ . Moreover, this ripple back-propagates and injects into the source in the absence of a bulky dc-link passive filter, an active compensator or a suitable digital controller with a front-end converter in the two-stage converter. This paper proposes a new adaptive sliding mode control for a two-stage dc–dc–ac converter to reduce proliferation of ripple without compromising dynamic performance. The front-end boost converter in the considered two-stage converter interfaces a battery bank and single-phase inverter fed loads. The control shapes the output impedance of the boost converter to reduce the ripple component at battery input. Second, the proposed controller achieves good dynamic performance at line and load transients. A fast voltage recovery with small undershoot/overshoot can be achieved at transients using the proposed controller. The proposed technique is validated using a hardware of the 1-kW two-stage converter.

Generator load response control

Abstract: A voltage regulating system for a generator that supplies the battery and electrical loads on a motor vehicle The system includes a load response control for detecting whenever a substantial electrical load is applied to the generator tending to cause a drop in generator output voltage and when such a condition is detected field current is controlled to gradually increase field current from some value The load response control includes means for storing an electrical signal that corresponds to generator field current and for utilizing this stored value to set generator field current at a value corresponding to a field current that occurred just prior to the detected drop in voltage and then increasing field current slowly from this value The system includes means for preventing a subsequent drop in detected load voltage from actuating the load response control for the time duration that field current is being slowly increased by the load response control once it has been triggered by an initial drop in voltage

Generating Multi-Scroll Chua's Attractors via Simplified Piecewise-Linear Chua's Diode

Abstract: High implementation complexity of multi-scroll circuit is a bottleneck problem in real chaos-based communication. Especially, in multi-scroll Chua's circuit, the simplified implementation of piecewise-linear resistors with multiple segments is difficult due to their intricate irregular breakpoints and slopes. To solve the challenge, this paper presents a systematic scheme for synthesizing a Chua's diode with multi-segment piecewise-linearity, which is achieved by cascading even-numbered passive nonlinear resistors with odd-numbered ones via a negative impedance converter. The traditional voltage mode op-amps are used to implement nonlinear resistors. As no extra DC bias voltage is employed, the scheme can be implemented by much simpler circuits. The voltage-current characteristics of the obtained Chua's diode are analyzed theoretically and verified by numerical simulations. Using the Chua's diode and a second-order active Sallen-Key high-pass filter, a new inductor-free Chua's circuit is then constructed to generate multi-scroll chaotic attractors. Different number of scrolls can be generated by changing the number of passive nonlinear resistor cells or adjusting two coupling parameters. Besides, the system can be scaled by using different power supplies, satisfying the low-voltage low-power requirement of integrated circuit design. The circuit simulations and hardware experiments both confirmed the feasibility of the designed system.

Soft-Switching PWM Technique for Grid-Tie Isolated Bidirectional DC–AC Converter With SiC Device

Abstract: Soft-switching techniques have become very attractive in bidirectional grid-tie dc–ac converters utilizing high-frequency link transformers for galvanic isolation. This paper presents a new pulse-width modulation (PWM) switching technique for controlling a bidirectional isolated dc–ac–ac converter along with its soft-switching method. The proposed PWM technique has the ability to control the input dc current and to inject a sinusoidal three-phase current to the grid at unity power factor. In the first stage, an H-bridge converter is used to convert the dc voltage to a high-frequency square-wave single-phase voltage. In the second stage, a matrix converter is used to convert the high-frequency voltage waveform to conventional three-phase voltage synchronized with the grid. Therefore, a single-phase high-frequency transformer is used to link the H-bridge output voltage to the matrix converter input voltage. The proposed soft-switching technique is achieved by connecting shunt ceramic capacitors across all converter switches. The mathematical model and the circuit operation for soft-switching are presented along with the voltage controllable limits. The effectiveness of the proposed technique has been verified experimentally using a laboratory prototype.

Controlling for variable impedance and voltage in a memory system

Abstract: A memory interface device, system, method, and design structure for controlling for variable impedance and voltage in a memory system are provided. The memory interface device includes a calibration cell configurable to adjust an output impedance relative to an external reference resistor, and driver circuitry including multiple positive drive circuits and multiple negative drive circuits coupled to a driver output in a memory system. The memory interface device further includes impedance control logic to adjust the output impedance of the calibration cell and selectively enable the positive and negative drive circuits as a function of a drive voltage and a target impedance.