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In flexible DC transmission systems, when a fault occurs in the receiving-end AC system, it results in a power surplus on the receiving-end DC side. This necessitates a dynamic active power balancing device, leading to the emergence of the DC chopper in this context. However, it is important to note that overvoltage can occur during the operation of the DC chopper, requiring overvoltage suppression measures to ensure equipment safety. In this paper, aiming at a typical two-terminal flexible DC transmission system, the composition of the system is first introduced. The generation mechanism of overvoltage in the sub-modules of the DC chopper valve is analysed. Two major categories of suppression strategies, namely system-level and equipment-level strategies, are proposed. The effectiveness and applicability of each strategy are verified and evaluated through PSCAD simulations.

Switching overvoltage is closely related to the development of the power grid. In recent years, the rated voltage, line length, and transmission capacity of the power grid have been increasing, and the resulting switching overvoltage has become more serious. By using the simulation software ATP-EMTP to make the simulation model, this paper simulates the overvoltage generated by the opening and closing of the no-load line, including the simulation of the no-load line closing in different periods, adding an arrester and opening and closing resistance to limit the overvoltage. By comparing the simulation images, the limiting effects of different measures on switching overvoltage are compared.

Electrical networks are a complex field of study, and the stronghold of phenomena that are not always easy to describe, to treat, to analyse, as in the case of incidents caused by short circuits, accidental arcs, lightning, tripping of works, etc. All these phenomena lead us to focus particularly on their immediate effects from their appearance until their disappearance or elimination. The duration of this type of fault thus generates a crucial and sometimes critical transient period for the electrical networks affected, as it is generally very short, but can have disastrous consequences going as far as the total collapse of the network (black-out). In this work, we created our own code for simulating electrical network transients in the MATLAB environment using the Toolbox Simulink package to try to replace transient software (such as PSCAD), even if the steps to be taken are not can claim to result in such a professional program as PSCAD software. The purpose of this work is the study of transient overvoltage in electrical networks using elaborate code and PSCAD software. We have tried in the introduction of this work to provide a description of transient overvoltage: definition of transients, Sources of transients, Categories of transients. Secondly, we discussed the elaborate code, which I named MATP (Matlab Analysis Transients Program), which was created in MATLAB giving a description of the code and their structure with graphic windows, and then I privately described the software PSCAD. Then we simulated several faults such as: a line opening fault, a short-circuit fault, for a networked system: electrical network 05 nodes. At the end, we analysed the results of the two programs for the faults mentioned above with our electrical networks.

In order to solve the problems of complex operation steps, insufficient measurement accuracy and poor safety of the current generator excitation overvoltage protection device tester, the testing technology of generator excitation overvoltage protection device was deeply studied in this paper. Firstly, the overall architecture of the excitation overvoltage protection device tester was constructed. Secondly, it was designed from two aspects of software and hardware. Finally, combined with the actual application scenario, the developed tester was used to measure the action voltage and working voltage fluctuation range of the excitation overvoltage protection device. It was verified that the tester developed in this paper is simple to operate and the measurement results have high accuracy.

In order to suppress the transient overvoltage at the bus bar of the transmission terminal of the AC-DC system, a transient overvoltage suppression strategy based on an improved VDCOL curve is proposed. Firstly, the expression of transient overvoltage is derived based on the DC short-circuit ratio, and then an evaluation index of transient overvoltage is proposed according to the standard of overvoltage. Then, according to the control curve design principle of VDCOL, an improved VDCOL curve based on the Tanh function is proposed. Finally, this suppression strategy is used to suppress the transient overvoltage at the bus terminal. Through the actual network data verification, the results show that the improved VDCOL curve has a better suppression effect on transient voltage than the traditional control curve, which proves that the strategy has higher applicability.

The large-scale new energy station transmission system is relatively weak, and long-distance transmission is prone to transient overvoltage. The hysteresis of the control loop of the Static Var Generator (SVG) can also contribute to the increase of transient overvoltage. Therefore, this article first establishes a photovoltaic power generation model, SVG model, and photovoltaic grid-connected system. Secondly, the transient overvoltage coupling mechanism of photovoltaic grid-connected systems under various faults such as commutation failure, DC blocking, and DC restart was analyzed through PSCAD simulation. At the same time, the changes in transient overvoltage before and after the installation of SVG were compared, and SVG’s reactive power dynamic behavior was analyzed. Finally, the mechanism of SVG assisting in increasing transient overvoltage was summarized.

With the rapid increase of distributed generation (DG) in the distribution network (DN), the analysis of DG maximum bearing capacity (DGMBC) is paid more attention. However, the existing methods can not precisely simulate the overvoltage risk concerning occurrence probability and severity. To this end, the overvoltage scenario classification method and overvoltage severity coefficient correction method are proposed in this paper, which can effectively reflect the real overvoltage risk in DN. The IEEE 33-bus test feeder is used to compare the calculation results of overvoltage risk with other methods.

In developing countries, the basic problem is power fluctuation and uneven voltage, which leads to serious damage to electronic devices and electrical equipment. Power fluctuation and uneven voltage supply are significant problems in the lead industry. Under-voltage, over-voltage, brownouts, blackouts, spikes, etc., are common problems which are faced due to fluctuation. Using our project, we have attempted to resolve the problems of under-voltage and over-voltage. In our project, we will be using Arduino UNO as a control board, which will be used to calculate the input voltage and determine whether it is over-voltage, normal-voltage, or under-voltage. Depending on the input voltage, the relay will get on or off according to the command. Arduino UNO, on the other hand, sends data to the ESP8266 Node MCU. As soon as the ESP8266 Node MCU connects to the wifi network, the data will be sent to a Google sheets (with the help of API call). After the data is stored in google sheets, it will be processed, and then a graph will be created that will indicate when over-voltage and under-voltage occurred.

To address the problems of limited analysis scenarios in mathematical optimization methods and conservative assessment in random scenario simulation methods, this paper first introduces the concept of overvoltage risk and proposes an overvoltage risk-based PV capacity assessment method for distribution networks. Based on this method, the severity of overvoltage is further considered, and the overvoltage risk index is improved by introducing correction coefficients. The assessment results obtained from this method can better reflect the real overvoltage risk level of the distribution network, which is more adaptable and meaningful for actual PV capacity planning. Finally, a practical 55-bus distribution system in a region of China is used as an example to verify the adaptability and effectiveness of the proposed method.

Given that the existing passive arc suppression technology of the distribution network cannot eliminate three-phase unbalanced overvoltage and the difficulties in dynamic measurement and hardware implementation of active current arc suppression equipment based on power electronics, a new technology of unbalanced overvoltage suppression and voltage arc suppression based on flexible control of distribution network zero sequence voltage is proposed. During normal operation, we inject current to eliminate three-phase unbalanced overvoltage; in case of a grounding fault, the system neutral point voltage shall be actively regulated, the fault phase voltage shall be reduced, the arcing conditions shall be destroyed, and the fault arcing shall be fundamentally realized. The 10 kV distribution network model is built in PSCAD/EMTDC simulation environment to verify the new technology of unbalanced overvoltage suppression and voltage arc suppression of zero sequence voltage flexible control. The simulation results show that the new technology can effectively suppress three-phase unbalanced over-voltage, reduce fault phase voltage, and realize reliable arc suppression of grounding faults.