Comparative Feasibility Studies of High Voltage Circuit Breaker Operating in the LFAC System With Different Frequencies

Abstract

With the development of the flexible low frequency transmission technology following the improvement of offshore wind power transmission, it is of great significance to investigate the operation adaptability of the main equipment especially under the low frequency conditions. A comparative study was performed in the present work to discuss the dynamic operation performance of a 252 kV/50 kA puffer-type circuit breaker influenced by the system operational frequency. Since the decreased operational frequency would result in a longer arc duration, a pre-designed driving mechanism with characteristics of high speed control was proposed and compared with a conventional unit. Moreover, as one of the reasonable indicators to evaluate the interruption performance of the circuit breaker, the critical rate of rise of recovery voltage (RRRV) that the circuit breaker can withstand after the arc extinguishment under different low frequencies were computationally obtained by an established arc model. The effects of the frequency change on the arc dynamic characteristics during the interruption of circuit breaker were comprehensively discussed as well and it could reasonably provide technical optimisation for the development of low-frequency-based circuit breaker for further engineering applications by analysing its interruption feasibility.INDEX TERMS offshore wind power, low frequency, high speed control, RRRV, arc dynamic characteristics, interruption feasibility

Design and control of modular multilevel matrix converter with symmetrically integrated energy storage for low frequency AC system

“…The main circuit configuration of SI-AM 3 C is similar to that of conventional M 3 C, where low frequency system (LFS) side three phases m (A, B, C) are connected to power frequency system (PFS) side three phases n (a, b, c) via nine arms in a matrix form. Each arm is composed of a series-connected arm inductor and cascaded SMs.…”

“…Moreover, the additional bi-directional DC/DC converter enhances the ESU controllability with a broader operating voltage range. The basic operating principle of SI-AM 3 C is illustrated by the power flow chart also given in Figure 1. The converter input active power and reactive power from LFS are denoted by P G , Q G , and the converter output active power and reactive power to PFS are denoted by P g , Q g .…”

“…LFAC improves the AC line transmission capacity with the lower operating frequency, which still retains the AC transmission property. The conventional HVAC transmission equipment including circuit breakers and transformers can be used in the LFAC system with adaptive modifications [3], thus providing the technology advantage of LFAC over HVDC in the fault handling problem and the multi-terminal system construction. And the elimination of sending-end converter station makes the LFAC scheme more economical than the HVDC scheme for renewable energy base integration, such as offshore wind power transmission system [4].…”

“…Modular multilevel matrix converter (M 3 C) that is a family member of the modular multilevel converter (MMC) is now accepted as the potential AC/AC converter topology in the LFAC system [5]. Compared to other two typical alternatives, the Hexverter and the back-to-back MMC, M 3 C shows economic advantages in the high-power high-voltage field [6,7]. The M 3 C based LFAC scheme was adopted in the Hangzhou 220 kV demonstrate project and the Taizhou 35 kV demonstrate project located in China.…”

“…The rest of this paper is organized as follows. In Section 2, converter topology and operating characteristics of SI-AM 3 C are first introduced. The evaluation method for the required SMs integrated with ESUs is presented in Section 3.…”