Colin Charnock Davidson

Calculation of power losses for MMC-based VSC HVDC stations

VSC technology is now well established in HVDC and is, in many respects, complementary to the older Line Commutated Converter (LCC) technology. Many advantages have been claimed for VSC technology in HVDC, including the smaller site footprint. On the other hand, VSC HVDC stations have higher power losses than LCC stations. Although the relative advantages and disadvantages are well known within the industry, there have been very few attempts to quantify these factors on an objective basis. In part, this is because of the lack of applicable standards for determining the power losses of a VSC station. No equivalent of IEC 61803 is today available for VSC-HVDC, but now a draft IEC standard (IEC 62751) is in preparation, which will permit objective comparisons to be made between power losses of LCC and VSC stations.

IGBT overcurrent turn-off tests for the MMC-based VSC valves

Nowadays, the Multi-level Modular Converter (MMC) has shown more and more advantages over the traditional Pulse Width Modulation (PWM)-based converter and has been widely adopted as the preferred topology for VSC (Voltage Sourced Converter) valves for High Voltage Direct Current (HVDC). Though IEC 62501 has been published since 2009 to define the requirements of the electrical testing for the VSC valves, so far very few papers have really discussed the test methods for any VSC valve tests or disclosed any test results. In this paper, one of the most important tests required by IEC 62501, the IGBT Overcurrent Turn-off test, is discussed for MMC-based VSC valves. Several faults that may occur when the IGBT can experience overcurrent are analysed, the test methods for several supplementary tests are discussed and finally the relevant test results are presented.

Electrical type tests for the voltage sourced converter valves based on modular multi-level converter

Though IEC 62501 was already published in 2009 to define the requirements of the electrical type testing for the Voltage Sourced Converter (VSC) valves for High Voltage Direct Current (HVDC) transmission, so far very few papers have really discussed the test methods for VSC valve nor disclosed any test results [1, 2]. In this paper, all the type tests required by IEC 62501 are discussed for a Modular Multi-level Converter (MMC)-based VSC HVDC valve based upon the half-bridge topology, with a method introduced for each test and the corresponding test results presented.