Research on Saturated Iron-Core Superconductive Fault Current Limiters Applied in VSC-HVDC Systems

Nonlinear Control of Back-to-Back VSC-HVDC System via Command-Filter Backstepping

“…With the rapid development of economy, the demand for energy is rising [1]. There is a great technological development in the power generation, transmission, distribution, and other aspects [2]. However, with the development of power energy, there are a lot of new technical problems in terms of transmission, such as economic grid-connected technology of decentralized and small renewable energy power generation, power supply technology of isolated island and other passive load, expansion of urban electric load capacity and reconstruction technology of urban power grid, remote power supply, and grid connection of nonsynchronous power grid and microgrid.…”

“…However, with the development of power energy, there are a lot of new technical problems in terms of transmission, such as economic grid-connected technology of decentralized and small renewable energy power generation, power supply technology of isolated island and other passive load, expansion of urban electric load capacity and reconstruction technology of urban power grid, remote power supply, and grid connection of nonsynchronous power grid and microgrid. The traditional AC and DC transmission technology is still unable to effectively solve the above problems in the technical and economic benefits [2]. With the development of power electronics and control technology, the above problems can be solved by using voltage-source-converter high voltage direct current (VSC-HVDC) composed of IGBT, IGCT, and other new full controlled power electronic devices, which can realize the independent control of active power and reactive power [3].…”

“…With the development of power electronics and control technology, the above problems can be solved by using voltage-source-converter high voltage direct current (VSC-HVDC) composed of IGBT, IGCT, and other new full controlled power electronic devices, which can realize the independent control of active power and reactive power [3]. VSC-HVDC has the following two main advantages, one is that VSC-HVDC transmission technology supplies power to the passive load without the commutation voltage of the AC system, the other one is that VSC-HVDC does not need AC power grid to provide reactive power to stabilize DC voltage, which can work as static synchronous compensator (STATCOM) [2][3][4]. Moreover, the other advantages are the following: large transmission capacity, small harmonic of output voltage, low cost and little loss, and the current of the AC-side being controlled so that the short-circuit capacity of the system can not be added [2][3][4][5].…”

“…VSC-HVDC has the following two main advantages, one is that VSC-HVDC transmission technology supplies power to the passive load without the commutation voltage of the AC system, the other one is that VSC-HVDC does not need AC power grid to provide reactive power to stabilize DC voltage, which can work as static synchronous compensator (STATCOM) [2][3][4]. Moreover, the other advantages are the following: large transmission capacity, small harmonic of output voltage, low cost and little loss, and the current of the AC-side being controlled so that the short-circuit capacity of the system can not be added [2][3][4][5]. Therefore, VSC-HVDC play a very significant role in the gird-connection of largescale wind farm and the development of new technologies such as urban power supply and isolated island power supply, which meet the energy demand of continued rapid growth and efficient use of energy.…”

“…Backstepping is widely used in the control system design of VSC-HVDC, which has obtained some achievements [15][16][17][18][19][20][21][22]. But this kind of controller has the following two main disadvantages: (1) the derivative of each virtual controller needs to be analyzed and calculated, and the calculation process is very complicated, so it is difficult to be applied in practical engineering; (2) physical limitations in practical systems are not considered in the design process of controller, which may cause the problem of control saturation [14]. Currently, there are many ways to solve the above problems, such as dynamic surface control [23,24] and command filter [25,26].…”