Analysis and Output Power Control of Unidirectional Secondary-Resonant Single-Active-Half-Bridge DC-DC Converter

Development of high-frequency-isolated DC-DC converters is underway for charging and discharging electric vehicle batteries. As a charger, a Single Active Bridge (SAB) converter, which is composed of a primary full-bridge converter, a high-frequency transformer, and a secondary full-bridge diode rectifier circuit, has been proposed as a unidirectional high frequency isolated DC-DC converter. In this paper, as a simple circuit configuration, a Secondary-Resonant Single-Active-Half-Bridge (SR-SAHB) converter, in which the primary and secondary circuits of the SAB converter are both half-bridge circuits, and a resonant capacitor connected in parallel to each secondary diode, is created. Due to the partial resonance on the secondary side, power transmission with unity transformer turn ratio and unity voltage conversion ratio can be realized, and a high total input power factor of the transformer can be achieved. As a result, the maximum voltage and current of the switching devices and the transformer voltage can be reduced. Moreover, soft switching in all commutations can be realized. The operation waveform is analyzed, and output power control is derived using the variable frequency control method. The effectiveness of the proposed SR-SAHB has been verified by experimental results using a 2.4 kW 20 kHz, 265V laboratory prototype.

Hardware Implementation of Differential Oscillatory Neural Networks Using VO 2-Based Oscillators and Memristor-Bridge Circuits

Oscillatory Neural Networks (ONNs) are currently arousing interest in the research community for their potential to implement very fast, ultra-low-power computing tasks by exploiting specific emerging technologies. From the architectural point of view, ONNs are based on the synchronization of oscillatory neurons in cognitive processing, as occurs in the human brain. As emerging technologies, VO2 and memristive devices show promising potential for the efficient implementation of ONNs. Abundant literature is now becoming available pertaining to the study and building of ONNs based on VO2 devices and resistive coupling, such as memristors. One drawback of direct resistive coupling is that physical resistances cannot be negative, but from the architectural and computational perspective this would be a powerful advantage when interconnecting weights in ONNs. Here we solve the problem by proposing a hardware implementation technique based on differential oscillatory neurons for ONNs (DONNs) with VO2-based oscillators and memristor-bridge circuits. Each differential oscillatory neuron is made of a pair of VO2 oscillators operating in anti-phase. This way, the neurons provide a pair of differential output signals in opposite phase. The memristor-bridge circuit is used as an adjustable coupling function that is compatible with differential structures and capable of providing both positive and negative weights. By combining differential oscillatory neurons and memristor-bridge circuits, we propose the hardware implementation of a fully connected differential ONN (DONN) and use it as an associative memory. The standard Hebbian rule is used for training, and the weights are then mapped to the memristor-bridge circuit through a proposed mapping rule. The paper also introduces some functional and hardware specifications to evaluate the design. Evaluation is performed by circuit-level electrical simulations and shows that the retrieval accuracy of the proposed design is comparable to that of classic Hopfield Neural Networks.

NORMALIZED PARAMETERS OF A MAGNETORESISTIVE SENSOR IN BRIDGE CIRCUITS

Magnetoresistive sensors are considered as part of bridge circuits for measuring magnetic field strength and electric current value. Normalized or relative expressions are introduced to change the resistance of the sensor and the measured bridge voltage to increase the information content of the regime to provide the possibility of comparing the regimes of different sensors. To justify these expressions, a geometric interpretation of the bridge regimes, which leads to hyperbolic straight line geometry and a cross ratio of four points, is given. Upon a change in the sensor resistance, the bridge regime is quantified by the value of the cross ratio of four samples (three characteristic values and the current or real value) of voltage and resistance. The cross ratio, as a dimensionless value, is taken as a normalized expression for the bridge voltage and sensor resistance. Moreover, the cross ratio value is an invariant for voltage and resistance. The proposed approach considers linear and nonlinear dependences of measured voltage on sensor resistance from general positions.

Voltage and frequency control of standalone wind-driven self-excited reluctance generator using switching capacitors

This paper presents a methodology for voltage and frequency (V–f) control of a standalone wind-driven self-excited reluctance generator (WDSERG). The methodology is based on proposing two different compensation configurations using two switching capacitors (short-shunt and long-shunt compensation) for (V–f) control. The dynamic and steady-state performances of the two configurations are discussed under different operating conditions: wind speeds, load currents and power factors. This analysis is done by developing a complete dynamic model of WDSERG including the excitation capacitors and load. Therefore, complete equivalent circuits are proposed. The values of capacitors are controlled by adjusting the duty cycle of H-bridge circuits with PI controllers. To validate the proposed configurations and their dynamic models and equivalent circuits, simulation results for a 1.5-kW standalone WDSERG and experimental results for 0.2 kW reluctance generator driven by a DC motor, emulating the wind turbine, are carried out. The results show a significant enhancement in voltage and frequency regulation with the selected optimal capacitances for each configuration; however, short-shunt compensation is the preferred configuration as it controls the output voltage and frequency with minimum values of capacitances and minimum required duty variation.

Hyper redundancy for super reliable FPGAs

The subject of the research presented in the article is hyper-redundant elements and FPGA devices that can be used in highly reliable digital systems (HRDS). The current work develops hyper-reliable logic elements, memory elements, and buffer elements for HRDS based on FPGAs, their simulation, and reliability assessment. Objective: to develop fault-tolerant logical elements of LUT for one, two, and three variables. Develop fault-tolerant static random access memory, D – flip-flop, and buffer element. To do a simulation in NI Multisim to validate performance and estimate complexity and power consumption. Derive formulas for assessing the reliability of the developed elements and devices and build graphs of comparison with known methods of triple modular redundancy. Methods used the introduction of redundancy in transistor level, simulation methods in Multisim, mathematical estimations of transistor number, reliability calculations. The following results were obtained: when introducing redundancy at the transistor level and using series-parallel circuits, it is necessary to at least quadruple the number of transistors. Passive-fail-safe elements and devices have been developed that can withstand one, two, and three transistor failures (errors). An assessment of their effectiveness has been conducted, showing their preference over the majority reservation. Conclusions. The synthesis and analysis of passive-fault-tolerant circuits with an ocean of redundancy, which ensures the preservation of a logical function for a given number of failures (from one to three), have been conducted. The costs are more than to maintain functional completeness in the method previously proposed by the author, but they are worth it. Despite the significantly greater redundancy compared to majority redundancy, power consumption turned out to be lower with an insignificant increase in latency. The proposed hyper-fault-tolerant FPGAs are advisable to use in critical application systems when maintenance is impossible. In the future, it is advisable to consider the issue of redundancy at the transistor level using bridge circuits.

Controllable-Dual Bridge Fault Current Limiter for Interconnection Micro-Grids

Different types of fault current limiters (FCLs) have been developed and designed based on non-superconducting DC reactors (NSDRs). This paper proposes a controllable dual-bridge FCL (CDBFCL) based on the NSDR for use in an AC-type micro-grid. It includes a NSDR and two series and shunt bridge circuits. The series bridge is based on diode semiconductor switches and is coupled in series with the line via a transformer. The shunt bridge is based on thyristor semiconductor switches and is coupled in parallel with the line. The shunt bridge provides a variable voltage source. It compensates for the DC side voltage drop due to NSDR resistance and semiconductor switches during normal operating condition. In addition, by controlling the shunt bridge firing angle, it produces a controllable DC voltage, which can control the fault current amplitude during a fault. The structure, principle operating work, and control system of the proposed CDBFCL are presented. The CDBFCL performance is studied analytically and through simulation by the PSCAD/EMTDC software. In addition, the simulation results are compared with those obtained experimentally from a prototype CDBFCL and show a close correlation.

RESEARCH OF ELECTRIC POWER QUALITY OF TRACTION SUBSTATIONS OF A HIGH MOUNTAIN MINER

The paper presents a methodology for researching the levels of higher harmonic in networks with a voltage of 6 kV and developed measures to eliminate harmonics of the non-canonical series. According to the results of the research, it was found that the sources of high-er harmonic ones are the ATP-500 traction substations, connected to the 6 kV network in groups and alone. In the 6 kV network, the 3rd, 5th, 7th and 11th harmonics of the canonical series, as well as the 3rd, 4th, 6th and 8th harmonics of the non-canonical series, are distin-guished, the levels of which significantly exceed the permissible levels according to GOST. The presence of non-canonical harmonics is caused by the asymmetry of the bridge circuit (current asymmetry relative to the abscissa axis). An instruction has been developed for the pre-start check of the bridge circuit gates to eliminate asymmetry. The prevalence of 5 and 7 higher harmonics in the 6 kV network was established and it was recommended to take into account the possibility of resonance phenomena in the pulse-phase control circuits of electric drives connected to the 6 kV network of the mine and open pit. The implementation of the recommen-dations set forth in the work increases the reliability of the bridge circuits of traction substa-tions and eliminates the possibility of the appearance of non-canonical harmonics, which im-proves the voltage quality in accordance with the requirements of GOST.

Sensors of Rapidly Changing Pressure Based on Jet Force

Static and dynamic characteristics of rapid response pneumatic digital systems are determined with the help of pneumatic-galvanometric sensors that consist of pneumatic optical converters, electrical bridge circuits and magnetoelectric galvanometers. This paper presents theoretical and experimental studies of the pneumatic optical converter whose mode of operation is based on the jet force effect on a plate of limited dimensions commensurate with the dimensions of the contact area between the jet and the plate. The investigations are based on the equality of moments of the jet force and the counter-moment of the rod that the plate is fixed on. The sensitivity and other static characteristics of the converter (linearity, measurement rage) as well as other parameters necessary for interpreting the readings, calculating errors and calibrating the scale are determined. The natural frequency is sufficient to control dynamic processes controlled by pneumatic systems. For the design of converters, it is proposed to use the aggregate criterion of the quality factor that equals the product of the sensitivity and the natural frequency squared. The performed calculations are verified by experiments.