The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
Islanded operation mode of HVDC sending terminal is the condition that generators are only connected to DC system, disconnected with main AC networks. When disturbed, an islanded system is more prone to be frequency instable than a connected system. In this paper, a type of frequency controller based on phase compensation principle is proposed. By changing the closed-loop dominated poles to expected...
Recently, a power plant such as a thermal power station tends to be built in a remote location and the transmission distance becomes longer. Hydro power plants are built in an intermountain region. Since they are quite away from an urban area and the generation power is transmitted via long-distance transmission lines, this power system has some problems such as steady-state stability, transient stability...
In recent years, pin corrosion on porcelain and glass insulators has occurred on many UHVDC transmission projects in China. With the operation surrounding of insulators taken into consideration, the mechanism of pin corrosion is studied and analyzed in this paper. Mechanical characteristics tests are also carried out. Test results indicate that pin corrosion can decrease the mechanical strength of...
Alternate arm converter (AAC) and hybrid cascaded multi-level converter (HCMC) are two promising hybrid multi-level converters (HMCs) for long-distance overhead line (OHL) based high voltage direct current (HVDC) transmission systems. This paper first outlines the basic operational principles of AAC and HCMC and based on their topological features, the initial required numbers of the H-bridge cells...
According to the design scheme of the Zhundong-Wannan ±1100kV power transmission project built this year, there are 24 grounding switches (GS) configured in the valve hall to ensure safety when maintenance. A huge investment is required due to the expensive GS and their huge volume causing a huge valve hall area. Therefore, it is necessary to optimize the grounding switches configuration (GSC) to...
When the requirement to perform dynamic insulation coordinate on a real-time simulator has recently surfaced in the design cycle of MMC-HVDC systems, accurate real-time simulation models for surge arrestors and MMC are of great importance to perform such tests. This paper presents an iterative algorithm to solve the mathematical model of arrestor and a multi-rate model for the MMC-HVDC system running...
In order to study the secondary arc characteristics of single-phase transient fault in UHV transmission lines with hybrid reactive compensation, a transmission line electromagnetic coupling model is presented in this paper. Dynamic model of secondary arc was established on the basis of improved Mayer equation. Based on the transient simulation and the method of Laplace transform, the law of secondary...
In a high-voltage direct current (HVDC) transmission system, it is increasingly adopted to connect or replace a part of its traditional line commutated converters (LCCs) with modular multilevel converters (MMCs), forming a hybrid HVDC system. This hybrid topology achieves high performance at a relatively low cost and thus has gained lots of attention from industry. This paper analyzes the DC resonance...
Aging characteristics of conductor surface of ultra-high voltage direct current (UHVDC) power transmission lines have a large influence on ground-level resultant electric field. A method to analyse the impact of the aged conductors on resultant electric field is introduced in this paper. Firstly, the surface profile and surface roughness of the new and aged conductors are measured by scanning electron...
Because 1000kV UHV substations cover enormous area, it is hoped that lightning rods be installed on the frames of main transformers to reduce installation of excessive independent lighting rods, and thus to reduce substation area and cost. Referring to years of operating experience of many 110–500kV substations, lightning rods might be installed on the frames of main transformers to shield direct...
Partial discharge test is one of the most important tests for on-site converter transformer. However, this test is often encountered some interference, such as corona, suspended discharge, power supply-side interference and so on. The precision of transformer partial discharge test which can be affected by those interference. In this paper, the common interference factors of converter transformer...
Offshore wind farm is usually integrated into bulk grid onshore through the AC submarine cable. The voltage stability of grid is affected due to reactive voltage characteristics and compensation scheme. It's necessary to study reactive voltage and control strategy in-depth with offshore wind farms integration in order to increase transmission capacity, reduce impact of large scale of wind power on...
Selecting inter-phase circulation, up and lower bridge arm current, and AC output voltage wave of the inverter as research objects, this paper analysed harmonic components in Modular Multilevel Converter (MMC) in Nearest Level Modulation (NLM) when MMC is used as inverter. With theoretical deduction, this paper points out that the up and lower bridge arm current mainly contains DC current component,...
The voltage dependence of HVDC (High Voltage Direct Current) converters as a load in ac systems is studied in this paper. Analytical studies are conducted for various HVDC control modes. It is shown that HVDC converter behaves between constant power and constant current. Its reactive power is more close to constant current type load. It is also demonstrated that the unfavorable load voltage relationship...
With the construction of UHV power grid, state assessment and diagnosis of power equipment in transmission and transformation systems have increasingly become the key technology to ensure the safety and stability of power system. Currently, state diagnosis of power equipment is mostly based on one single monitoring parameter. In this paper, a comprehensive analysing method was presented based on the...
This paper presents the mechanism of LCC-HVDC system's commutation failures arising from ac faults. The theoretical analysis of commutation failure is developed by considering direct current dynamics. On the basis of the theoretical analysis, the impacts of ac fault level and fault occurring time on commutation failure are quantified. Moreover, this paper provides a more precise commutation failure...
Compared with traditional AC distribution system, DC distribution system is provided with significant advantages in various aspects. In order to maintain a steady voltage under different operating conditions in DC distribution system, this paper proposes a coordinated scheme for automatic voltage control by conducting a comprehensive optimization for DC voltage error control and droop control. Reference...
The efficiency of the Modular Multilevel Converters (MMC) makes it the preferable VSC solution for the HVdc field. The knowledge of its modus operandi and their devices it is extremely important to improve the MMC performance. This work analyzes the on-state mode of the half-bridge cell semiconductors in respect to the active/ reactive power flow conditions of the MMC. The MMC-HVdc INELFE project...
This paper presents a simple, fast, accurate fundamental frequency estimation method with good resistance to harmonics and noise. In the proposed method named the accumulated sum method (ASM), a new data sample of a measured signal is constructed using the summation of the samples in the original sampling data. The effects of harmonics and noise are mitigated by the proposed algorithm. Performance...
The gains of phase-locked-loop (PLL) and outer-loop control have significant impacts on the power transfer limits for the voltage source converter (VSC) connected to weak ac system. Therefore, in this paper, an enhanced control diagram with advanced outer-loop control is proposed. First, the P-V slope controller is proposed based on the participation factor analysis. Second, considering the overvoltage...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.