Data Rate Maximization in RIS-Assisted D2D Communication with Transceiver Hardware Impairments

We maximize the transmit rate of device-to-device (D2D) in a reconfigurable intelligent surface (RIS) assisted D2D communication system by satisfying the unit-modulus constraints of reflectin elements, the transmit power limit of base station (BS) and the transmitter in a D2D pair. Since it is a non-convex optimization problem, the block coordinate descent (BCD) technique is adopted to decouple this problem into three subproblems. Then, the non-convex subproblems are approximated into convex problems by using successive convex approximation (SCA) and penalty convex-concave procedure (CCP) techniques. Finally, the optimal solution of original problem is obtained by iteratively optimizing the subproblems. Simulation results reveal the validity of the algorithm that we proposed to solve the optimization problem and illustrate the effectiveness of RIS to improve the transmit rate of the D2D pair even with hardware impairments.

МОДЕЛЮВАННЯ ЕНЕРГЕТИЧНИХ ПРОЦЕСІВ В ГІБРИДНІЙ ФОТОЕЛЕКТРИЧНІЙ СИСТЕМІ З АКУМУЛЯТОРОМ ДЛЯ ПОТРЕБ ЛОКАЛЬНОГО ОБ’ЄКТУ

Purpose. Improving the efficiency of a hybrid photoelectric system with a rechargeable battery for the needs of the local object by improving the management of the forecast with simulation of energy processes in the system, development of principles for the implementation of energy management systems.Methodology. Analysis of energy processes in the electrical circuits of the photoelectric system with the formalization of the principles of control reconfiguration and the use of computer modeling based on archival data of photoelectric battery generation to evaluate the efficiency of energy management.Findings. Block structures and the general structure of the model of energy processes in the system for the daily cycle of work with an estimation of the cost of electricity consumed from the grid have been developed. The principles of control modes and power consumption of the system according to the forecast of photoelectric battery generation were formalized.Originality. The principles of setting the battery current according to the forecast of photoelectric energy generation, the state of battery charge and the power limit consumed from the grid have been improved. It will help to make better use of the energy of the photoelectric battery and reduce the consumption of electricity from the grid. The mathematical model of the rechargeable battery, built on the manufacturer's catalog data has been improved. The formalization of energy processes in the system with the use of additional variables, which provide reconfiguration of work with regulation of photoelectric battery generation or battery current and taking into account the power limit consumed from the grid is substantiated.Practical value. The obtained solutions are the basis for designing photoelectric control systems to meet the needs of local objects.

Analisis Pengaruh Pengaturan Sudut Penyalaan Thyristor Pada Tegangan Eksitasi Terhadap Keluaran Daya Reaktif Generator di PT.PJB PLTU Gresik Unit 3

The process of changing mechanical energy into electrical energy is carried out by a synchronous generator using an excitation system that functions to supply a DC source to the generator field winding. In this study, the excitation system used is a static excitation system that uses a transformer and several thyristors connected in a bridge configuration. The excitation system is then implemented on a generator with a capacity of 200 MVA / 15 kV using the MATLAB Simulink R2017b simulation. By using the above circuit, the thyristor ignition angle setting can be adjusted so that it can adjust the excitation voltage and obtain the appropriate excitation current to maintain the stability of the generator output voltage. The simulation was carried out with variations in generator load and using 2 different types of excitation settings. The first setting is to set the thyristor ignition angle to 30° with t=10 ms, at this setting the generator can maintain a stable V out value with a voltage regulation limit of ±5% and the reactive power that can be generated by the generator is +50 MVAr and - 40 MVAr. When given a constant excitation at an angle of 35° with t=1 ms, the value of Vout exceeds the expected regulatory limit and the resulting reactive power limit is between +60 MVAr and -100 MVAR where the reactive power does not match the load requirements. This can have an impact on the interconnection system, namely when the reactive power of the generator is greater than the load requirement, the generator with a smaller reactive power will absorb reactive power in the interconnection system and can disrupt the stability of the interconnection network.

The comparison of power capability between towed kite and horizontal axis fan

Airborne Wind Energy (AWE) mainly collects wind energy by tethered aircraft at a certain altitude. This paper discusses the recent development of AWE. The actuator disc theory is adopted to consider the influence of kites on wind flow obstruction. The difference of working mode between a horizontal-axis wind turbine (HAWT) and a crosswind kite power systems (CKPS) is compared, the power limit of HAWT and CKPS is calculated, and the reason of the limit power is analyzed. It is pointed out that CKPS has a wider range of flight and should be further analyzed and calculated rather than simply generalized by the system disk theory.

Tradeoff-HARQ Scheme for Full-Duplex SWIPT DF Relay

The SWIPT (simultaneous wireless information and power transfer) DF (decoding and forwarding) relay system could achieve the purpose of both increasing revenue and reducing expenditure. By analysing the system model and transmission characteristics of full-duplex relay, this paper optimizes the retransmission slot structure to enhance the system performance. Firstly, the state transition model is established based on the analysis of the retransmission slot structure. Secondly, the state probability of each state and the transition probability between states are calculated to obtain the total data passing rate, energy transmission efficiency, and total transmission time. Thirdly, in order to compare the performance of various HARQ (hybrid automatic repeat request) schemes more effectively, JNTP (joint normalized throughput of information transmission and energy transmission) is constructed. Monte Carlo simulations finally confirm that the proposed tradeoff-HARQ scheme outperforms the regular-HARQ scheme in terms of JNTP: the performance of the tradeoff-HARQ scheme is 0.03883 higher than that of the regular-HARQ scheme when the total power limit is 20 dB and 0.00651 higher than that of the regular-HARQ scheme when the total power limit is 30 dB.

Experimental study on the heat transfer performance of a stainless-steel heat pipe with sintered fiber wick

A kind of stainless-steel heat pipe with sintered fiber wick is investigated with the aim to improve the heat dissipation when it is used in spent fuel pool in nuclear power plant. The effects of test angle, porosity and the filling rate on the heat transfer performance of the heat pipe are studied. At test angle 90°, the permeability plays an important role on the power limit since gravity can provide the necessary driving force. Larger porosity involves with poor heat conductivity although it results in better permeability. When test angle is zero gravity is no longer the driving force. In this case, the evaporation section can still avoid dry burning because part of the evaporation section is dipped in the deionized water. Therefore, permeability and filling ratio are two important factors influencing the power limit. Filling rate determines the vapor flowing space. When test angle is smaller than zero, gravity becomes resistance force. Then the lag tension and the filling rate exert greatest influence on the performance of the heat pipe. Smaller porosity corresponds to smaller contact angle.

Ensuring Energy Safety of the Biological Separation Shop

The article considers ways to solve the problem of ensuring the energy safety of separation workshops of biological industries using the example of the Armavir Biofabrika PKP. The existing power limit does not allow increasing output. At the same time, a sufficient level of electricity supply at the existing facilities of the biofabric will allow to double the output of finished products practically. You can solve this problem using additional or redundant power sources, as well as high-efficiency electrical equipment. One solution to the problem may be to use the developed synchronized axial two-way contactless wind-solar generator and separator for polydisperse liquid systems. The designed generator will transform wind and solar energy into AC electricity, while it can be synchronized with an external three-phase AC system. Separator uses inevitable heat loss of asynchronous motor to preheat separated product.

STABILITY AND CONTROL ASPECTS OF MICRO-GRID ARCHITECTURES OF WIND POWER SYSTEM

Voltage unstability nowadays is a serious problem, Present day electric power utilities are confronting numerous difficulties because of regularly expanding multifaceted nature in their task and structure. One issue that got wide consideration is voltage instability. One of the significant reasons for voltage instability in the power framework is with its receptive power limit. It can cause different damages to our electrical appliances, and therefore the approach used in this research is for the benefit for these dangerous phenomenon. In this research Voltage control single phase STATCOM using different sources such as Photovoltaic Cell, DC generator, battery and WAPDA used, in such a way to have a backup voltage source to have an untriptable supply, in case of less than 9 V the relay converter used the DC generator as back end source. It is a controller based system, controller on the basis of voltages changes the source to PV to DC and DC generator to Battery depends upon the voltages. Inverter is used which take input of 12 V that are controlled by relay in case of PV it is stabilized by buck converter. 1kVA Transformer then sets the voltage to 230V single phase, STATCOM is used after transformer to set the voltage at 230 V Power and Voltage monitoring system is used to check power and voltages at every point.

Power Limit Control Strategy for Household Photovoltaic and Energy Storage Inverter

The increased installation capacity of grid-connected household photovoltaic (PV) systems has been witnessed worldwide, and the power grid is facing the challenges of overvoltage during peak power generation and limited frequency regulation performance. With the dual purpose of enhancing the power grid safety and improving the PV utilization rate, the maximum feed-in active power can be regulated by modifying the maximum power point tracking (MPPT) algorithm and battery energy storage (BES) accessibility as control instructions. However, the existing methods not only waste installed PV capacity, but it becomes no longer accessible when the state of charge (SOC) of the BES approaches its upper limit. In response to the above problem, this paper proposes a power limit control strategy to coordinate the MPPT algorithm and the BES accessibility. The proposed strategy directly controls the inverter output current according to the power limit instructions from the electric operation control centers, leading to a bus voltage difference. The difference serves as a control signal for BES and PV. Under a power-limiting scenario, priority is given to power regulation through energy storage to absorb the limited active power. When the SOC of the BES reaches the upper limit of charging, modification of the PV MPPT algorithm facilitates the inverter output power to meet the power limit requirements. To further verify the effectiveness of the proposed power limit control strategy, both simulation and experimental studies are conducted, which consistently indicated a synchronized inverter current with grid voltage and a rapid power response of the power-limiting instruction within 0.2 s. The power limit control strategy not only improves the PV energy utilization but also supports the safe and reliable operation of the power gird in the context of soaring renewable energy penetration.