نشریه مهندسی برق و مهندسی کامپیوتر ایران
سال بیست و یکم شماره 3 (پیاپی 80، پاییز 1402)

In many microgrid control methods, the output information of sensors and actuators of neighbouring distributed generators (DGs) is used to stabilize and synchronize voltage and frequency. Many problems such as disturbances, uncertainty, unmodeled dynamics, cyber-attacks, noise, time delay, and measurement errors cause invalid data problems and errors in the system. Better microgrid control depends on the quality of data measured or sent from the output of sensors and actuators. In this paper, according to the advantages of the Cooperative distributed hierarchical control, it is used for control and synchronization in the islanded microgrid with the presence of sensor and actuator error. To synchronize DGs with multi-agent systems and communication channels, it is modeled with graph theory. To stabilize and synchronize, sensor and actuator error in the DG model is mathematically formulated. In the proof of stability and synchronization, the appropriate Lyapunov candidate is presented and the conditions of stability and synchronization are proved. Finally, to show the effectiveness of the designed controller in solving communication channel problems and verifying the presented theory, a case study is simulated in the MATLAB/Simulink software environment with the presence of error and cyber-attack of sensors and actuators.

Dual-motor drive systems have been widely favored due to many advantages, including reduced dimensions and cost. In this paper, a model-based predictive control (MPC) method for a dual-motor drive system fed by a five-leg inverter (FLI) is introduced. Among the advantages of the MPC method, the independent and fast tracking of reference control variables and the elimination of cascade control structures dependent on the modulator for multi-motor systems can be mentioned. PI loops have disadvantages such as delayed time response, as well as design limitations of PI coefficients due to the FLI structure. In this paper, using the predictive control method based on the multi-objective model proportional to speed and current (MOMPC), the PI control loops have been removed. One of the challenges of this structure is how to allocate the DC link voltage to the motors. For this purpose, by defining the duty cycle corresponding to the steady-state voltage of the motors, the DC link voltage of the inverter is shared between the motors. In addition, by using this method, the control objectives of two motors become independent from each other, which reduce the torque ripple and current ripple of the motors.

Using multi-valued logic can reduce chip interconnections, which can have a direct effect on chip area and interconnections power consumption. In recent years, due to the ability of Nano electronics in the design of multi-level circuits, research in this field has flourished. The sequential circuits, flip-flops are important components of processors and VLSI circuits. In this paper, for the first time, a ternary flip-flop with a pulse generator has been proposed, and also a ternary binary-decode flip-flop and the first flip-flop using a buffer have been introduced. Then these flip-flops are compared with themselves and previous circuits. Also, these flip-flops have been used in the design of the ternary counter. The simulation results with HSPICE software show the correct performance of the proposed circuits. There is a 20% improvement in delay and a reduction in the number of transistors in the STI pulse generator flip-flop model, 30% in the SP flip-flop, and 30% in the buffer flip-flop. Also, in the comparison table, the advantages and disadvantages of each have been examined.

Time-delay systems have been very much considered in the last few decades. Many of these time-delay systems appear in different systems and branches of science such as engineering, chemistry, physics, disease models. The presence of delay makes the analysis and control of such systems much more complicated. In fact, the application of Pontryagin’s maximum principle to the optimal control problems with time-delay results in boundary value problem involving both delay and advance terms. In this paper, we consider a time-delay optimal control problems. The first section, using the Pontryagin's maximum principle for optimal control problems with time delay, the necessary optimality conditions for this problem, are obtained. Then a new algorithm is proposed to solve this problem numerically. This algorithm is based on an approximation for derivatives and linear interpolation for delayed arguments. Finally, the resulting equations becomes a linear programming problem that can be solved numerically. The efficiency of the proposed method is evaluated by solving several numerical examples.

Transformers are one of the most expensive and important equipment in power systems that are under the influence of electrical, thermal and chemical reactions The transformer health index is a standard that is used to evaluate the condition and determine the remaining life of the transformer by using laboratory data and field inspections. The purpose of this article is to determine the relationships between electrical, physical, chemical parameters of oil, dissolved gases in oil and transformer health index. One of the advantages of using the regression method in the analysis of transformer data compared to other methods for determining the transformer health index is determining the influence of the parameters that have the greatest impact on each other. In this article, Curve Estimation Regression method is used and the results are drawn by drawing graphs by SPSS statistical software to analyze the parameters. To carry out the simulations, the laboratory data of some transformers have been considered.

Designers of modern digital and analog systems have been using multiple voltage levels in one circuit to increase performance. To convert voltage levels in high-performance circuits, it is necessary to use voltage level shifter (LS) circuits with high speed and low power consumption. In this article, a high-performance LS circuit called LSBB (Level Shifter based on Body Biasing) is presented. LSBB consists of three parts: body biasing, current mirror circuit, and pull-up and pull-down circuit. The main idea of this design is to use the biasing circuit to depend on the base of the body of the transistors of the input stages to the VDDL voltage. This dependence leads to changes in the threshold voltage and as a result changes in the delay and power consumption to increase the performance of the circuit. Implementation in 180 nm TSMC technology and simulation with VDDL equal to 0.4 V, VDDH equal to 1.8 V and input frequency 1 MHz indicates the correct operation and high-performance of the proposed circuit, the delay values are 21.9 nS, the power consumption is 129 nW and the PDP equal to 2825 nW*nS confirms the high-performance of LSBB.

In this article, the consequence of the presence of delay in the switch signal for switched affine systems is investigated. First, based on the principles of stability, the process of extracting the switch law as the only control input is examined, then by presenting the practical stability issue for switched systems, more realistic view of these systems is proposed. The main focus of the article will be on the effect of delay in the transmission of switching signal information. The presence of limited delay in switching signal is usually caused by high volume of switching law calculations or any cyber attacks. In this paper, the practical Lyapunov stability results related to the states before and after the presence of delay in switching signal for a linear switched affine system are compared analytically and simulated. The results of the comparison of these modes show that when the value of delay in switching signal increases, the ultimate limit of the error for system states becomes larger, and this means a decrease in the convergence of the system states. In this regard, the results implemented for a DC-DC power converter and the necessary comparisons are presented in the last chapter.