Search Results (13)

The implementation of low-cost sensitive and selective gas sensors for monitoring fruit ripening and quality strongly depends on their long-term stability. Gas sensor drift undermines the long-term reliability of low-cost sensing platforms, particularly in precision agriculture. We present a real-time drift compensation framework based on a lightweight Temporal Convolutional Neural Network (TCNN) combined with a Hadamard spectral transform. The model operates causally on incoming sensor data, achieving a mean absolute error below 1 mV on long-term recordings (equivalent to <1 particle per million (ppm) gas concentration). Through quantization, we compress the model by over 70%, without sacrificing accuracy. Demonstrated on a combustion-type gas sensor system (dubbed GMOS) for ethylene monitoring, our approach enables continuous, drift-corrected operation without the need for recalibration or dependence on cloud-based services, offering a generalizable solution for embedded environmental sensing—in food transportation containers, cold storage facilities, de-greening rooms and directly in the field. Full article

The rapid development of prosumer renewable energy sources (RESs) observed in Poland in recent years causes problems in distribution networks such as current amplitude and voltage asymmetry increases, power and energy loss increases, and reverse power flows, and related are voltage control problems, deterioration of energy quality, etc. Moreover, in the case of planned repair/maintenance works in the network and the need to supply energy consumers in an islanded MV grid, the problem of the correct operation of such a subsystem appears. This occurs when the power production by the prosumers’ energy sources at a given moment exceed the power consumption. In such a case, reverse power flows occur in MV/LV transformers, i.e., from the LV network to the MV network. This causes reverse power flow to the diesel generator, leading to its shutdown and, in extreme cases, to damage. The solution to this problem is to use a mobile system equipped with energy storage in addition to a diesel generator and an LV/MV transformer. An additional problem in the case of using a mobile system (diesel generator) to power an MV island is the islanded MV network grounding. Grid islanding changes the earth fault current and electric shock voltages. In general, MV networks in Poland operate as compensated, i.e., grounding transformers are used, the star point of which is grounded by a compensation choke. Unfortunately, in the case of powering an MV island from a mobile system, there is no real possibility of grounding the star point of the LV/MV transformer used there. This article proposes an algorithm of a diesel generator with an energy storage selection, including electric shock protection requirements verification, for the use in suppling energy via an islanded MV network. Full article

The correct and safe operation of electricity grids is a fundamental consideration in guaranteeing the supply of electricity with the correct parameters to consumers. One of the key aspects is how neutral point earthing works. In grids with the neutral point grounded by a Petersen coil, it is very important to properly tune its inductance in relation to the natural capacitance of the power grid. This is important both for the proper operation of earth fault protection and from the point of view of power quality, especially voltage asymmetry. Asymmetry of phase voltages in MV networks has a very negative impact on the operation of the railway network supplied by 12-pulse rectifiers. In this paper, the authors present the influence of the detuning factor of the earth fault compensation and the length and cross-section of the line on the value of voltage asymmetry factors. As the analyses carried out have shown, significant (up to 90%) values of the zero-sequence asymmetry factor can occur at low detuning, which can contribute not only to a decrease in the quality of the transmitted electricity but also to the unnecessary activation of protections. The values of the negative-sequence voltage asymmetry factor are much smaller (do not exceed 0.5% in the analysed cases) and do not depend on the network detuning factor. As the distance from the substation increases, an increase in the values of both types of asymmetry factors is also observed, with the relationship already negligibly small at considerable distances (above 20 km). Full article

Wireless sensor network (WSN) is an important component of healthcare. The design of the power management unit for WSN poses significant challenges, as it not only needs to achieve good current efficiency but also requires high power supply rejection (PSR) and good load transient performance. This paper presents a low-dropout regulator (LDO) with a low quiescent current and fast transient response to adequately meet the power supply requirements of WSN systems. To ensure system stability and reduce voltage spikes during load transients, an adaptive frequency compensation network is integrated into the circuit. Additionally, the LDO incorporates a level shifter that facilitates the bi-directional transmission of voltage signals across different power systems. The proposed LDO is designed and simulated in a 180 nm BCD process. It operates under a wide input voltage range from 0.8 V to 5.5 V, supports maximum load currents of up to 500 mA, and allows output voltages to vary from 0.8 V to 3.6 V by adjusting the feedback resistance. As a result of implementing the adaptive frequency compensation circuit, the overshoot and undershoot voltages at an output voltage of 1 V are measured to be only 23 mV and 5 mV, respectively. Moreover, the LDO achieves a PSR of −83 dB for bias voltage and −91 dB for input voltage at 1 kHz. The level shifter’s highest working frequency can reach 20 MHz under supply voltages (V_in = 1.65 V to 5.5 V; V_out = 3.6 V), thereby enabling high-speed data transmission. Finally, the LDO consumes a quiescent current of 42 μA while incorporating a bandgap reference circuit and other auxiliary circuits. Full article

The paper proposes a new local method of controlling the on-load tap changer (OLTC) of a transformer to mitigate negative voltage phenomena in low-voltage (LV) networks with a high penetration of photovoltaic (PV) installations. The essence of the method is the use of the load compensation (LC) function with settings determined via artificial neural network (ANN) algorithms. The proposed method was compared with other selected local methods recommended in European regulations, in particular with those currently required by Polish distribution system operators (DSOs). Comparative studies were performed using the model of the 116-bus IEEE test network, taking into account the unbalance in the network and the voltage variation on the medium voltage (MV) side. Full article

This article presents an original methodology to determine the optimal level of reactive energy transmission to low-voltage consumers supplied from MV/LV substations that guarantees the lowest total costs of reactive energy transmission through the DSO network and its generation in receiving installations within the reactive power compensation process. The average value of the optimal factor tgφ to be maintained by customers depends on the efficiency of the network, the characteristics of the load, and the market costs of energy losses due to the transmission of reactive energy through the network that are covered by the DSO and the costs of reactive energy generation in receiving installations. The results presented for real MV/LV substations operating in the Polish distribution network demonstrate the application of annual measurements of active and reactive energy consumed and generated registered by AMI systems to calculate the optimal reactive power compensation level. They can be applied to verify the permissible levels of reactive energy compensation applied by the DSOs until now within the yearly tariffs for customers. Full article

Wild mushrooms are not only tasty but also rich in nutritional value, but it is difficult for non-specialists to distinguish poisonous wild mushrooms accurately. Given the frequent occurrence of wild mushroom poisoning, we propose a new multidimensional feature fusion attention network (M-ViT) combining convolutional networks (ConvNets) and attention networks to compensate for the deficiency of pure ConvNets and pure attention networks. First, we introduced an attention mechanism Squeeze and Excitation (SE) module in the MobilenetV2 (MV2) structure of the network to enhance the representation of picture channels. Then, we designed a Multidimension Attention module (MDA) to guide the network to thoroughly learn and utilize local and global features through short connections. Moreover, using the Atrous Spatial Pyramid Pooling (ASPP) module to obtain longer distance relations, we fused the model features from different layers, and used the obtained joint features for wild mushroom classification. We validated the model on two datasets, mushroom and MO106, and the results showed that M-ViT performed the best on the two test datasets, with accurate dimensions of 96.21% and 91.83%, respectively. We compared the performance of our method with that of more advanced ConvNets and attention networks (Transformer), and our method achieved good results. Full article

The article presents a method for detecting earth faults in a compensated medium-voltage network, which can be used especially in fault current passage indicators, but also in standard protection devices. The method is based on the adaptation process of the zero-sequence current protection setting, with the adaptation factor depending on the current value of the zero-sequence voltage. In this article, a comparative analysis of the classical and adaptive zero-sequence current criterion is conducted, taking into account the errors of the measuring system. The results of simulations performed in the PSCad environment are also presented. For a representative set of example short circuits, it was shown that the effectiveness of the presented criterion can be more than 50% higher than that of the standard criteria, taking into account the range of detected transition resistances. A comparison of the proposed method with admittance criteria was also drawn, and it was shown that it is suitable for the detection of high-resistance earth faults. Full article

In this paper, we provide a thorough analysis and enhancement techniques of the linearity between the input voltage and output current in charge storage field effect transistor (FET) cells for a vector–matrix multiplier array in neural networks. A planar floating gate FET cell revealed superior linearity, because of boosting the floating gate using a drain voltage through capacitive coupling. If the coupling capacitance is extended by up to half of the gate capacitance, the coefficient of determination for linear regression is easily greater than 99.5%. However, the linearity of the charge trap FET, which keeps electrons in the insulating gate dielectric, must be compensated by either boosting the drain voltage, using a non-linear input driver, or supplying a quadratic current through an auxiliary path in the cell. Drain voltage boosting is limitedly effective over a small input range, while the auxiliary current path shows a coefficient of determination greater than 99.5% over a 500 mV input range. If the cell area matters, the charge trap FET with a diode connected FET as an auxiliary current path revealed the best performance, with an effective number of bits of 5.67, in a 21.3 F² cell area. Full article

The quality of electricity is a very important indicator. The durability and reliable operation of all connected devices depend on the quality of the network voltage. Rapid changes in loads, changes in network connections and the presence of uncontrolled energy sources require the development of new voltage regulation systems. This requires voltage regulation systems capable of responding quickly to sudden voltage changes. In substations with control transformers, it is possible thanks to the use of semiconductor tap changers. Moreover, voltage regulation and reactive power compensation systems should be built as one system. This is due to the close dependence of voltage and reactive power in the network node. Therefore, it was proposed to use artificial intelligence methods to build a new voltage regulation and reactive power compensation system using all measurement voltages of network nodes. In the first stage of the research, active and reactive powers, as well as the voltage of the reference node, were selected for 6420 periods of the mains voltage. The simulation results were compared for the classic voltage regulation system with semiconductor tap changers and the evolution algorithm based on voltage measurements from the entire MV network. A significant improvement in the quality of voltage regulation with the use of an evolutionary algorithm was demonstrated. Then, a second set of input data with increased values of reactive power was generated. The results of the evolutionary algorithm after the application of the classic, independent reactive power compensation system and two-criteria optimization were compared. It has been shown that only the two-criteria optimization algorithm keeps both |tgφ| within the acceptable range and the quality of voltage regulation is the best. The article compares different working algorithms for semiconductor tap changers. Full article

Digital communication over power lines is an active field of research and most studies in this field focus on low-voltage (LV) and medium-voltage (MV) power systems. Nevertheless, as power companies are starting to provide communication services and as smart-grid technologies are being incorporated into power networks, high-voltage (HV) power-line communication has become attractive. The main constraint of conventional HV power-line carrier (PLC) systems is their unfeasibility for being migrated to wideband channels, even with a high signal-to-noise ratio (SNR). In this scenario, none of the current linear/non-linear equalizers used in single carrier schemes achieve the complete compensation of the highly dispersive conditions, which limits their operation to 4 kHz channels. In this paper, a new PLC-channel model is introduced for transmission lines incorporating the effects of the coupling equipment. In addition, the use of the single-carrier frequency-division modulation (SC-FDM) is proposed as a solution to operate PLC systems in a wide bandwidth, achieving transmission speeds above those of the conventional PLC system. The results presented in this paper demonstrate the superior performance of the SC-FDM-PLC over conventional PLC systems, obtaining a higher transmission capacity in 10 to 30 times. Full article

Energy losses and bus voltage levels are key parameters in the operation of electricity distribution networks (EDN), in traditional operating conditions or in modern microgrids with renewable and distributed generation sources. Smart grids are set to bring hardware and software tools to improve the operation of electrical networks, using state-of the art demand management at home or system level and advanced network reconfiguration tools. However, for economic reasons, many network operators will still have to resort to low-cost management solutions, such as bus reactive power compensation using optimally placed capacitor banks. This paper approaches the problem of power and energy loss minimization by optimal allocation of capacitor banks (CB) in medium voltage (MV) EDN buses. A comparison is made between five metaheuristic algorithms used for this purpose: the well-established Genetic Algorithm (GA); Particle Swarm Optimization (PSO); and three newer metaheuristics, the Bat Optimization Algorithm (BOA), the Whale Optimization Algorithm (WOA) and the Sperm-Whale Algorithm (SWA). The algorithms are tested on the IEEE 33-bus system and on a real 215-bus EDN from Romania. The newest SWA algorithm gives the best results, for both test systems. Full article

The provision of ancillary services by electric vehicles (EVs) such as load smoothing and renewable energy (RE) compensation in the form of an aggregated storage is more regulated in the smart grid context. As such, the presence of multiple EV aggregators in the distribution network requires adept supervision by the distribution system operator (DSO). In this paper, a coordination scheme of aggregators is proposed to smoothen the load profile of distribution networks by enacting EV discharging during peak load and off-peak charging, keeping in view the EV driving requirements. A bi-level on-line interaction procedure from the DSO to the aggregators and vice versa is devised to manage the aggregators based upon their energy capacity and requirements. The aggregators employ a water-filling algorithm in a two-step EV power allocation method. The proposed scheme operation is demonstrated on an medium voltage (MV) distribution feeder located in Seoul with its actual traffic density data. The results show the achievement of peak shaving and valley filling objectives under aggregator coordination and that the EVs are completely charged before departure. The effect of various EV penetration levels and adaptivity of the scheme to RE incorporation is also verified. Furthermore, a comparison with an existing peak shaving method shows the superior performance of the proposed scheme. Full article