Band 24, Heft 2

In view of sensitivity, selectivity, and operating speed of the relay, the current differential technique is an alternative against overcurrent and distance-based techniques for long transmission line protection. Moreover, this technique has limited performance due to Line Charging Capacitive Current (LCCC), Current Transformer (CT) saturation further, by using synchronized data, the effect of LCCC can be nullified. However, in case of synchronition is lost, the performance of the current differential is not reliable. Hence, in this paper, the Inverse of Difference of both end Current phasors (IDC) is applied to prevent maloperation due to channel delay and synchronization loss. The simulation experiments are conducted under various operating conditions on a 345 kV, 50 Hz, IEEE 39-bus network using PSCAD 4.5 and MATLAB (R2020a). Results reveal the enhanced security under CT saturation, LCCC and sensitivity under high resistance line to ground faults.

This paper demonstrates the operational efficacy of a newly proposed fuzzy tuned fractional order controller to offer an improved frequency regulation of a multi area renewable energy source (RES) integrated nonlinear power system. The effect of governor dead band nonlinearity and generation rate constraint of hydro and thermal power plants are considered in the system. Moreover, a proposed appropriate High voltage direct current (HVDC) tie line model is incorporated in this work, to verify the frequency deviation. Different test cases are applied to verify the robustness of the controllers on frequency response. The superiority of the proposed controller upon Proportional integral and derivative (PID), fuzzy logic controller and fuzzy PID controller in minimizing frequency deviation has been verified through MATLAB SIMULINK environment.

It is essential to analyse the dielectric performance in a humid environment of insulating liquids of plant origin, considered as alternatives to mineral oil (MO) which is not environmentally friendly. This paper focuses on the effects of different moisture levels on the dielectric strength and partial discharge initiation voltage of two natural monoesters, based on castor oil (CO) and palm kernel oil (PKO), and MO. The different samples were moistened with a glycerol solution, then sealed and stored for 12 days to allow further diffusion of moisture into the samples. Dielectric strength was statistically evaluated from IEC 60156. Partial discharge inception voltage (PDIV) experiment was performed in conformity with a modified IEC 61294 purpose at ambient temperature. Based on the experimental observations, the moisture has different behavior on dielectric strength and PDIV of insulating oils. Monoesters have a better withstand to water contamination than MOs in power transformers.

The ultra high voltage direct current (UHVDC) technology plays an important role in the long-distance and large-capability transmission of renewable energy. Power grid company has to improve the reliability and efficiency of UHVDC transmission systems to support renewable energy utilization. In this paper, Six Sigma method is considered for improving the operation and maintenance (O&M) performance of UHVDC converter stations. The working tasks for the operation team and the maintenance team are introduced at first, respectively. The limitation of current O&M management is analyzed. A five-stage implementation of Six Sigma method is discussed in detail. The formed negative feedback ensures the sustainability of implementation and realizes closed-loop management. A representative equipment disposal case is used to demonstrate the adaptability and operability of the potential application of Six Sigma method.

This research was conducted on the ability of Power Line Communication (PLC) technology to communicate data for home energy management system through the traditional home electrical grids in Thailand. The study found that the Narrow-Band Power Line Communication (NB-PLC) is most suitable for smart home applications and safe for health of the residents. The results showed that the efficacy of PLC is mostly dependent on the service life time factor of the cables. The regression rate of signal level for the newest electric wire (1–15 years) is 83% lower than the oldest (30–45 years) and 47% lower than the middle life time (16–30 years). Also, the regression rate of signal level for the middle life time was 69% lower than the oldest wire. Whereby we could predict the signal level according to the changing length and service life time of electric cable. In this research, it was found that the carrier frequencies also are influence on the signal level of the power line communication. The signal level of KNX PL110 standard which used the frequency range 105 and 115 kHz is higher than the signal level of IDIS that used the frequency range 63.3 and 74.5 kHz and the regression of signal level of KNX PL110 standard is 68% lower than the IDIS standard. The experimental results also showed that baud rate “2400” is the best for power line communication because it generates more stable signal levels.

With the rapid development of the power system, the complexity of power system continues to increase. The large-scale of clean energy increases the complexity of the power system structure, which makes the power system’s operating status complex and changeable. To ensure the safety, stability, and economic operation of the power system, the power system needs to maintain a certain spinning reserve capacity and ensure that the reserve is available. The spinning reserve optimization method based on fixed partitions cannot effectively deal with the source-net-load volatility and the line congestion problems caused by wind power. To this aim, this paper proposes a power system reserve capacity partitioning algorithm based on the spectral clustering algorithm considering wind power. First, the energy-reserve joint optimization unit commitment problem is built. Secondly, considering the uncertainty of wind power output and the line N  − 1 failure, a risk assessment method for line congestion is established; then the power transfer distribution factor (PTDF) of the congested line is considered as the similarity measure. A method based on the iterative partition method based on spectral clustering is proposed. Finally, the reserve capacity configuration based on the dynamic partition results is determined. The IEEE-118 bus system is used in this paper to verify the proposed method. The results show that the reserve capacity dynamic partition method proposed in this paper determines the number of partitions automatically. Reserve capacity partitions are built reasonably. After the reserve capacity partitions, the availability of spinning reserve capacity is effectively guaranteed.

Distributed feeder automation (FA) needs to automatically recognize the changes in the feeder topology in real-time and has to configure the application topology of the corresponding distributed functions. This paper analyzes the application topology’s requirements when implementing distributed FA for the feeder equipped with a smart terminal unit (STU) and a fault passage indicator (FPI). Based on IEC 61850, the functional logic node and topology configuration of intelligent electronic devices (IEDs) are studied. The application topology identification and data flow dynamic binding methods for fault location, fault isolation, and power supply restoration are proposed. A case study verifies the effectiveness of the proposed method.

Hybrid AC–DC microgrid (HMG) is formed by connecting separate AC and DC microgrids with an interlinking converter (IC). In islanded mode of operation of the HMG its AC and DC subgrids are droop controlled to achieve power-sharing. The power flow between the subgrids happens through the IC, which regulates the amount of power being transferred based on the values of the frequency of AC bus voltage and the voltage at the DC bus. This paper presents the utilization of power-electronic converters to form the droop-controlled AC–DC subgrids of an islanded HMG which will be beneficial for further studies of IC and HMG. The detailed design and analysis of the closed-loop control system parameters of both the power converters is presented. The results obtained from simulations carried out in MATLAB/Simulink, and the real-time simulation results obtained by implementation using OPAL-RT OP4500 real-time digital simulator hardware are presented for the verification.

This article presents the grid connected hybrid solar-wind energy conversion system (HSWECS) using the cascaded diode clamped multilevel inverter (CDCMLI). The advantage of CDCMLI over the conventional cascaded H-bridge multilevel inverter (CHBMLI) is that the power transfer capacity of the CDCMLI is doubled. The solar and wind energy conversion systems are connected individually to the DC-links of CDCMLI through the DC–DC converter which is used to get maximum power from solar and wind systems. Due to the fluctuating power supply by renewable sources, the isolated DC-links of separate inverters suffer from varying DC-link voltages. A control scheme is proposed which is capable of balancing these DC-link voltages under various power generation scenarios, extracting the maximum possible power from renewable energy sources (RES), and injecting it into the grid at near unity power factor. The proposed control also monitors the power quality of the injected current into the grid. Furthermore, it allows the system to be connected to the grid without any transformer. In addition, mathematical modeling of the CDCMLI has been presented. The performance of the system is analyzed with Matlab/Simulink and confirmed by a prototype model with dSpace 1104.

Grid integration of solar photovoltaic (PV) systems is becoming popular recently due to the merits of stable support to conventional grid, limiting global warming and reduced emissions. However, maintaining capacitor voltage balancing, unity power factor, sinusoidal grid current and harmonic profile improvement are the challenging tasks owing to change in irradiation conditions. Multi-level inverters in grid connected systems will enhance the power quality of the system in terms of voltage and current total harmonic distortion. This paper proposes a highly reliable, robust and modular single phase solar PV fed fault tolerant hybrid cascaded H-bridge inverter with individual voltage/current control strategy for grid integration. Higher reliability and modularity, power factor correction, able to with stand without degrading the performance of the topology even under faulted conditions and harmonic profile improvement are the main objectives of the proposed system. The proposed system has been simulated and validated with experimental results on the developed prototype for different irradiation conditions and tested the performance of the topology with creation of faults on different modules at different times.

Because the existing maintenance models are not statistically analyzed, the maintenance effect is not ideal. Therefore, a distribution network area opportunistic maintenance model considering the total supply capability promotion of distributed generation is designed to achieve the total supply capability promotion and reduce the network loss rate after maintenance. Considering multiple time scales, the distribution network total supply capability model is constructed, and the improved repetitive power flow algorithm is used to count the model; taking the total supply capability model as the reliability basis of the distribution network system, and the maximum power supply capacity as the goal, the regional opportunistic maintenance model of total supply capability promotion is constructed, and the model is used to determine the area to be repaired, fully considering the reliability requirements of the distribution system, and combining with the node depth coding technology and the simulation Genetic algorithm optimizes the network structure, realizes the network reconfiguration, and completes the model solution. Through the analysis of the actual data, using this model to repair the regional equipment of distribution network can obtain good maintenance results. After the completion of maintenance, the network loss rate is low, but the total supply capability is high, which has good maintenance effect.