Detail of GB/T 30553-2023

Introduction of GB/T 30553-2023

High-voltage direct current (HVDC) power transmission using voltage sourced converters(VSC) 1 Scope This document gives general guidance on the subject of voltage sourced converters (VSC) used for transmission of power by high voltage direct current (HVDC). It describes converters that are not only voltage sourced (containing a capacitive energy storage medium and where the polarity of DC voltage remains fixed) but also self-commutated, using semiconductor devices which can both be turned on and turned off by control action. The scope includes 2-level and 3-level converters with pulse-width modulation (PWM), along with multi-level converters, modular multi-level converters and cascaded two-level converters, but excludes 2-level and 3-level converters operated without PWM, in square-wave output mode. HVDC power transmission using voltage sourced converters is known as "VSC transmission". Note: VSC direct current transmission is also known as "flexible VSC transmission". The various types of circuit that can be used for VSC transmission are described in this document, along with their principal operational characteristics and typical applications. The overall aim is to provide a guide for purchasers to assist with the task of specifying a VSC transmission scheme. Line-commutated and current-sourced converters are specifically excluded from this document. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. IEC 62501 Voltage sourced converter (VSC) valves for high-voltage direct current (HVDC) power transmission - Electrical testing IEC 62747 Terminology for voltage-sourced converters (VSC) for high-voltage direct current (HVDC) systems 3 Terms and definitions For the purposes of this document, the terms and definitions given in IEC 62747, IEC 62501 and the following apply. ISO and IEC maintain terminological databases for use in standardization at the following addresses: • IEC Electropedia: available at http://www.electropedia.org/ • ISO Online browsing platform: available at http://www.iso.org/obp 3.1 General Basic terms and definitions for voltage sourced converters used for HVDC transmission are given in IEC 62747. Terminology on electrical testing of VSC valves for HVDC transmission is given in IEC 62501. To support the explanations, Figure 1 presents the basic diagram of a VSC system. Dependent on the converter topology and the requirements in the project, some components can be omitted or can differ. 3.2 Letter symbols Uconv: line-to-line AC voltage of the converter unit(s), RMS value, including harmonics Iconv: alternating current of the converter unit(s), RMS value, including harmonics UL: line-to-line AC voltage of the AC system, RMS value, including harmonics IL: alternating current of the AC system, RMS value, including harmonic Udc: DC terminal-to-terminal voltage of one converter unit Id: DC current of the DC bus of the VSC transmission system 3.3 VSC transmission 3.3.1 Oltage sourced converters DC capacitor; VSC DC capacitor capacitor bank(s) (if any) connected between two DC terminals of the VSC, used for energy storage and/or filtering purposes 3.3.2 AC side radio frequency interference filter radio frequency interference filter; RFI filter filters (if any) used to reduce penetration of radio frequency interference (RFI) into the AC system to an acceptable level 3.3.3 converter side high frequency filter filters (if any) used to mitigate the HF stresses of the interface transformer 3.3.4 DC side radio frequency interference filter filters (if any) used to reduce penetration of radio frequency (RF) into the DC system to acceptable limits 3.3.5 type tests tests carried out to verify that the components of VSC transmission system design will meet the requirements specified Note: In this document, type tests are classified under two major categories: dielectric tests and operational tests. 3.3.6 dielectric tests tests carried out to verify the high voltage withstanding capability of the components of VSC transmission system 3.3.7 operational tests tests carried out to verify the turn-on (if applicable), turn-off (if applicable), and current related capabilities of the components of VSC transmission system 3.3.8 production tests tests carried out to verify proper manufacture, so that the properties of the certain component of VSC transmission system correspond to those specified 3.3.9 sample tests production tests which are carried out on a small number of certain VSC transmission components, for example valve sections or special components taken at random from a batch 3.4 Power losses 3.4.1 auxiliary losses electric power required to feed the VSC substation auxiliary loads Note: The auxiliary losses depend on whether the substation is in no-load or carrying load, in which case the auxiliary losses depend on the load level. 3.4.2 no-load operating losses losses produced in an item of equipment with the VSC substation energized but with the VSCs blocked and all substation service loads and auxiliary equipment connected as required for immediate pick-up of load 3.4.3 idling operating losses losses produced in an item of equipment with the VSC substation energized and with the VSCs de-blocked but with no real or reactive power output 3.4.4 operating losses losses produced in an item of equipment at a given load level with the VSC substation energized and the converters operating 3.4.5 total system losses sum of all operating losses, including the corresponding auxiliary losses 3.4.6 station essential auxiliary load loads whose failure will affect the conversion capability of the HVDC converter station (e.g. valve cooling), as well as the loads that need to remain working in case of complete loss of AC power supply (e.g. battery chargers, operating mechanisms) Note: Total "operating losses" minus "no-load operating losses" can be considered as being quantitatively equivalent to "load losses" as in conventional AC substation practice. 4 VSC transmission overview 4.1 Basic operating principles of VSC transmission 4.1.1 Voltage sourced converter as a black box The operation of a voltage sourced converter is described in greater detail in Clause 5. In 4.1 , the converter is treated as a black box that can convert from AC to DC and vice versa, and only steady-state operation is considered. Figure 2 depicts a schematic diagram of a generic voltage sourced converter connected to a DC circuit on one side and to an AC circuit on the other.

Contents of GB/T 30553-2023