Sliding-mode controller for a step up-down battery charger with a single current sensor

This paper proposes a battery charger solution based on the Zeta DC/DC converter to provide a general interface between batteries and microgrid direct current (DC) buses. This solution enables to interface batteries and DC buses with voltage conversion ratios lower, equal, and higher than one using the same components and without redesigning the control system, thus ensuring global stability. The converter controller is designed to require only the measurement of a single inductor current, instead of both inductors currents, without reducing the system flexibility and stability. The controller stability is demonstrated using the sliding-mode theory, and a design procedure for the parameters is developed to ensure a desired bus performance. Finally, simulations and experiments validate the performance of the proposed solution under realistic operation conditions.

Research on the Dual Modulation of All-Fiber Optic Current Sensor

Acousto-optic modulator (AOM) and electro-optical modulator (EOM) are applied to realize the all-fiber current sensor with a pulsed light source. The pulsed light is realized by amplitude modulation with AOM. The reflected interferometer current sensor is constructed by the mirror and phase modulation with EOM to improve the anti-interference ability. A correlation demodulation algorithm is applied for data processing. The influence of the modulation frequency and duty cycle of AOM on the optical system is determined by modeling and experiment. The duty cycle is the main factor affecting the normalized scale factor of the system. The modulation frequency mainly affects the output amplitude of the correlation demodulation and the system signal-to-noise ratio. The frequency multiplication factor links AOM and EOM, primarily affecting the ratio error. When the frequency multiplication factor is equal to the duty cycle of AOM and it is an integer multiple of 0.1, the ratio error of the system is less than 1.8% and the sensitivity and the resolution of AFOCS are 0.01063 mV/mA and 3 mA, respectively. The measurement range of AFOCS is from 11 mA to 196.62 A, which is excellent enough to meet the practical requirements for microcurrent measurement.

Model of Magnetically Shielded Ferrite-Cored Eddy Current Sensor

Computationally fast electromagnetic models of eddy current sensors are required in model-based measurements, machine interpretation approaches or in the sensor design phase. If a sensor geometry allows it, the analytical approach to the modeling has significant advantages in comparison to numerical methods, most notably less demanding implementation and faster computation. In this paper, we studied an eddy current sensor consisting of a transmitter coil with a finitely long I ferrite core, which was screened with a finitely thick magnetic shield. The sensor was placed above a conductive and magnetic half-layer. We used vector magnetic potential formulation of the problem with a truncated region eigenfunction expansion, and obtained expressions for the transmitter coil impedance and magnetic potential in all subdomains. The modeling results are in excellent agreement with the results using the finite element method. The model was also compared with the impedance measurement in the frequency range from 5 kHz to 100 kHz and the agreement is within 3% for the resistance change due to the presence of the half-layer and 1% for the inductance change. The presented model can be used for measurement of properties of metallic objects, sensor lift-off or nonconductive coating thickness.

IoT Based Non–Technical Loss Detection and Mitigation System for Power Distribution Networks

Electrical Energy crisis is a major problem faced in the world today and it’s increasingly significant in this part of Africa. A perfect solution seems not to be feasible as several solutions have been proposed in the past by various authors with little impact on the power sector. In this work, we present a method of Non-Technical Loss (NTL) detection consisting of a microcontroller interfaced with a current sensor that measures the current on the power line. A sensor node is placed at the supply end of the pole while two or more others sensor nodes are connected to the output of the pole depending on the number of consumers. The measured value of current is sent via the microcontroller to a web cloud that is accessible by the consumers and the utility company from any part of the world by simply logging on to the website; www.electricity-theft.herokuapp.com. The design uses the principle of Kirchhoff Current Law (KCL) to achieve this aim. The consumers can therefore monitor their power consumption from any location in the world and prevent theft on the network. The results obtained from the installation of the sensor nodes were analyzed using correlation and regression analysis. A correlation analysis of the data results gave us a correlation coefficient of 0.9802, while a regression analysis provided us with a linear relationship between the dependent and independent variable expressed mathematically thus Y = 0.916x + 0.254. A regression graph is also plotted. Furthermore, a T-Test and F-Test was conducted to statistically test the sensor nodes. A NodeMCU Wi-Fi microcontroller and a self-powered Phidget current sensor is used for the sensor node design. Communication between the sensor nodes is via Wi-Fi while a 4G router was used to provide internet services.

Components’ Characterization of End-of-Life Dishwashers

The treatment of Wastes of Electrical and Electronic Equipment (WEEE) is a significant source of secondary raw materials. Ferrous and non-ferrous metals, electronic equipment, and plastics are among these materials. One of the most common metals sourced out of WEEE is stainless steel. Dishwashers are common sources of stainless steel, so large amounts of stainless steel can be recovered from them. In this project, dishwashers were submitted to size reduction via shredding, and the shredded products went through a magnetic separator (which separates all the magnetic ferrous components), an eddy current sensor (which separates all the non-ferrous components) and an induction sorting sensor (which removed all the metallic fractions). This procedure led to the following two streams: one with stainless steel, boards, and cables and another stream mainly including plastic. In the next stage, the stainless-steel stream passed through a high-intensity magnetic separator, leading to a magnetic and a non-magnetic stream. Thereafter, hand sorting was applied to both streams which aimed to increase the recovery from each stream.

A Precise Current Detection Method Using a Single Shunt and FET Rds(on) of a Low-Voltage Three-Phase Inverter

In this study, a low-voltage three-phase inverter was used alongside a shunt resistor to measure the current. However, it is known that this type of inverter and shunt resistor system has a region where the measurement of current is impossible due to structural limitations. As a result, many studies have focused on this region through the use of additional algorithms. Most studies measured current by forcibly adjusting the PWM duty in order to measure the current at the region where it could not be sensed. However, unfortunately, the total harmonic distortion (THD) increases in the current due to PWM adjustment. This causes an increase in torque ripple and inverter control instability. Therefore, in this paper, current was measured using the Rds(on) value between the drain source resistor when MOSFET was turned on and the Kalman filter in a low-voltage three-phase inverter with a single shunt. Additionally, the value was verified via comparison with the values achieved when a Hall-type current sensor and single shunt were used. As a result, this study confirmed that the inverter with a single shunt performs the same as a Hall-type sensor at the region where current cannot be detected.

Cascoded GaN half-bridge with 17-MHz wide-band galvanically isolated current sensor

A cascoded GaN half-bridge with wide-band galvanically isolated current sensor is proposed. A 650-V depletion-mode GaN FET is switched by a low-propagation-delay gate driver in active-mode. The standby and active modes are switched by a 25-V N-ch LDMOS. The current sensor uses the LDMOS as a shunt resistor, gm-cell-based sense amplifier and mixer based isolation amplifier for wider bandwidth. PVT variations of on-resistance of the current-detecting MOSFET are compensated using a reference MOSFET. A digital calibration loop across the isolation is formed to keep the current sensor gain constant within ±1.5% across the whole temperature range. The wide-band current sensor can measure power device switching current. In this study, a cascoded GaN half-bridge switching and inductor current sensing using low-side and high-side device current are demonstrated. The proposed techniques show the possibility of implementing a GaN half-bridge module with isolated current sensor in a package.