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Bài báo nghiên cứu lựa chọn các giải pháp đấu nối nhà máy điện gió ngoài khơi vào hệ thống điện Việt Nam, với hai giải pháp đấu nối hiện nay là truyền tải điện xoay chiều (HVAC) và truyền tải điện một chiều (HVDC). Bài báo đã thực hiện tính toán phân tích ảnh hưởng của nhà máy điện gió ngoài khơi đến hệ thống điện dựa vào các tiêu chuẩn kỹ thuật yêu cầu đảm bảo khi thực hiện đấu nối với hai giải pháp truyền tải trên. Ngoài các tính toán trào lưu công suất và phân tích ảnh hưởng đến hệ thống điện bằng hai giải pháp đấu nối, bài báo đã thực hiện phân tích kinh tế tổng mức đầu tư cho hai giải pháp đấu nối cho nhà máy Điện Gió Ngoài Khơi (ĐGNK) Trung Nam công suất 800MW đang đề xuất bổ sung Quy hoạch nhằm lựa chọn giải pháp đấu nối cho nhà máy điện gió ngoài khơi đảm bảo về mặt kỹ thuật và kinh tế cho dự án. Kết quả cho thấy, phương án đấu nối bằng HDVC đảm bảo được các yếu tố về kỹ thuật và kinh tế.

With the penetration of distributed generation (DG) units, the power systems will face insecurity problems and voltage stability issues. This paper proposes an innovatory method by modifying the conventional continuation power flow (CCPF) method. The proposed method is realized on two prediction and correction steps to find successive load flow solutions according to a specific load scenario. Firstly, the tangent predictor is proposed to estimate the next predicted solution from two previous corrected solutions. And then, the corrector step is proposed to determine the next corrected solution on the exact solution. This corrected solution is constrained to lie in the hyperplane running through the predicted solution orthogonal to the line from the two previous corrected solutions. Besides, once the convergence criterion is reached, the procedure for cutting the step length control down to a smaller one is proposed to be implemented. The effectiveness of the proposed method is verified via numerical simulations on three standard test systems, namely, IEEE 14-bus, 57-bus, and 118-bus, and compared to the CCPF method.

The subsynchronous resonance (SSR) is an important problem in the power system, and especially the series compensated transmission lines may cause SSR in the turbine generators, such that it leads to the electrical instability at subsynchronous frequencies and potential turbine-generator shaft failures. Taking the Vietnamese Vungang thermal plants as an example, a shaft failure of Vungang I thermal power unit has occurred on November 24, 2015, due to SSR. The main cause for this failure is a resonance caused by the series capacitors on the 500 kV grid. This paper analyzes the SSR based on the location of shaft cracks and turbine generator mode shape for Vungang I and II thermal power plants. On the basis of that, it develops a novel control strategy for each Flexible AC Transmission system (FACTS) device as the thyristor controlled series compensator (TCSC), static VAR compensator (SVC), and static synchronous compensator (STATCOM). Then they are comparable to one another in order to choose a feasible solution for mitigating the SSR. The effectiveness of the proposed control strategy is verified via time domain simulation of the Vietnamese 500/220 kV transmission system using EMTP-RV and PSS/E programs. The obtained results show that the proposed strategy for SVC can be applied to immediately solve the difficulties encountering in the Vietnamese power system.

The Vietnamese power system has experienced instabilities due to the effect of increase in peak load demand or contingency grid faults; hence, using flexible alternating-current transmission systems (FACTS) devices is a best choice for improving the stability margins. Among the FACTS devices, the thyristor-controlled series capacitor (TCSC) is a series connected FACTS device widely used in power systems. However, in practice, its influence and ability depend on setting. For solving the problem, this paper proposes a relevant method for optimal setting of a single TCSC for the purpose of damping the power system oscillations. This proposed method is developed from the combination between the energy method and Hankel-norm approximation approach based on the controllability Gramian matrix considering the Lyapunov equation to search for a number of feasible locations on the small-signal stability analysis. The transient stability analysis is used to compare and determine appropriate settings through various simulation cases. The effectiveness of the proposed method is confirmed by the simulation results based on the power system simulation engineering (PSS/E) and MATLAB programs. The obtained results show that the proposed method can apply to immediately solve the difficulties encountering in the Vietnamese power system.

The primary goal of this paper is to develop and apply an adaptive fuzzy (AF) based on the proportional integral derivative (PID) controller for the automatic voltage regular (AVR) system in the synchronous generator (SG) to improve output voltage stability. This proposed AF-PID is applied to ameliorate the shortcomings of the traditional PID controller by determining the optimal coefficients for the controller. Firstly, the initial coefficients of the traditional PID controller are calculated by using the Ziegler-Nichols method. After that, it develops the AF algorithm based on the fuzzification, rules of the fuzzy controller, and defuzzification of the voltage signals for self-tuning the coefficients to add the traditional PID controller. The transient response of the system is simulated and analyzed by considering the different step changes in reference voltage. The efficacy of the proposed AF-PID controller for the AVR system in the SG is illustrated by comparing it with traditional PID and without the controller based on the obtained results from the case studies. It can be concluded that when applying the proposed method, the transient response characteristics of the system from the perspective of simulating via the time domain under any sudden load changes in system operation, such as the rise time, steady-state error, max peak overshoot, and settling time are greatly improved. The simulation has been performed using the MATLAB/Simulink program. [ABSTRACT FROM AUTHOR]

One of the significant obstacles in electrical power transmission is the incident of failures, most notably the fault in transmission lines. It can influence the quality of the supplied electrical power, and actually, the country’s security and economy are threatened. Researching an intelligent solution to diagnose the fault is the done thing. This paper integrates deep learning methods, namely the discrete wavelet transform (DWT), GoogleNet, and probabilistic neural network (PNN) approaches, to detect, classify, and locate the fault. The DWT-based multiresolution analysis (MRA) is used for fault identification to process energy distribution during the transient states. After feature extraction, the obtained energy of the subband signal is used as the feature vector. It is employed as an input of GoogleNet for the fault type classification. The effectiveness of the proposed method has been demonstrated on the 220kV transmission line between the Hoa Khanh and Hue substations of Vietnam via time-domain simulation using EMTP-RV and MATLAB softwares. The simulated results are compared to the accuracy of the line distance protection REL521 for considering even cases, including the normal case and ten different fault causes, and the conditions of the pre-fault load changes. As a result, it concludes that the proposed method is a favourable method applied to the problem of analyzing the power system stability in the field of power transmission. [ABSTRACT FROM AUTHOR]

This paper presents an entirely new subject to prevent SSR in thermal power plants. The SSR phenomenon is firstly analyzed by using the frequency scanning method in the frequency domain under considering other operating conditions for operating grid-configurations, and then the SSR due to the self-excitation and the transient phenomenon is analyzed to provide the inputs for working out an effective solution. Three devices, namely the thyristor controlled series capacitor (TCSC), static synchronous compensator (STATCOM), and blocking filter (BL) are considered as a proposed choice, and the control strategy for each mentioned device is developed to mitigate the SSR. For TCSC, the control strategy is designed based on two PI controllers for the voltage and current regulator, respectively; besides, the auxiliary subsynchronous damping controller is proposed to provide a supplementary signal of dynamic current on the input signal that is chosen the generator rotor speed deviation. For STATCOM, two PI controllers, using for the DC and connected point voltage regulator, proposed; besides, the auxiliary sub-synchronous damping controller is proposed to provide a supplementary signal of dynamic current on the input signal that is chosen the generator rotor speed deviation. For BL, the natural torsional vibration frequency of models to ensure that SSR due to torsional interaction (TI), torque amplification (TA), and induction generator effect (IEG) are prevented. The effectiveness of this study is verified via a time-domain simulation of the Vietnam Quang-Tri electric power system connected to the 500/220 kV transmission system using EMTP-RV and PSS/E programs. The obtained results show that the frequency scanning method is chosen as a useful method to analyze SSR and the effective solution can be applied to immediately solve the difficulties encountering in the Vietnamese power system to be BL. [ABSTRACT FROM AUTHOR]

A number of techniques have been proposed to dampen the power system oscillations in the electric power systems. Flexible alternating current transmission system (FACTS) devices are becoming one of them. Among the FACTS family, the static synchronous compensator (STATCOM), a shunt connected FACTS device, has been widely used to provide smooth and rapid steady state, limit transient voltage, and improve the power system stability and performance by absorbing or injecting reactive power. However, the influence ability depends on its placement, control signal, and place of receiving-signal in the network. In order to satisfy these issues, this paper proposes a method for optimal setting and signal position of the STATCOM into the multi-machine power systems with the aim for damping the electromechanical oscillations. This method is developed from the energy approach based on Gramian matrices considering multiple tasks on the Lyapunov equation, in which the observability Gramian matrix is used to seek an optimal location for STATCOM placement. The another is the controllability one used to determine the best local input signal placement that is chosen as a feedback signal for the power oscillation damping (POD) of STATCOM. In addition, the Krylov-based model reduction method is introduced to shorten the calculation time. The proposed method has been verified on the IEEE 24-bus system by analyzing the small-signal stability to search several feasible placements, and then the transient stability is analyzed to compare and determine an optimal placement through testing various cases. The obtained result is also compared with other optimal method. [ABSTRACT FROM AUTHOR]