Economical single-ended cascaded hybrid HVDC transmission system with bi-directional power flow

Abstract

The invention discloses an economical single-ended cascaded hybrid DC power transmission system with two-way flow of the tidal current, which comprises: a rectification station and an inverter station, the DC sides of the rectification station and the inverter station are connected through a DC transmission line; the rectification station and the inverter station The inverter station includes a thyristor converter LCC and a modular converter connected to each other; it also includes a sending-end AC grid and a receiving-end AC grid; the thyristor converter LCC and the modular converter are respectively connected to each other through a double-winding transformer The AC grid at the sending end is connected to the AC grid at the receiving end. The present invention proposes a new LCC‑MCSM (monopole current sub‑module)‑HVDC type hybrid converter valve. Under the constraint that the current direction only flows in one direction, the DC power flow can be realized by using the polarity reversal of the DC port voltage. two-way flow.

Description

Economical single-ended cascaded hybrid DC transmission system with bidirectional flow of power technical field The present invention relates to the technical field of direct current power transmission, especially a kind of economical single-ended cascaded hybrid with bidirectional flow of tidal current. Combined DC transmission system. Background technique [0002] Conventional DC transmission systems, also known as line-commutated DC transmission systems (LCC-HVDC), employ thyristor valve banks It has the characteristics of large transmission capacity, high voltage level, low cost and small loss, and has been widely used; but the limit of thyristor is Due to its own semi-controlled characteristics, it is easily affected by voltage fluctuations and sags of the connected AC system, resulting in commutation failure, resulting in output The electrical system is blocked and the power flow is interrupted, which in turn causes the voltage stability problem of the AC system ...

AI Technical Summary

Problems solved by technology

However, in this LCC-HBSM-HVDC hybrid DC transmission system, the LCC type converter valve only allows unidirectional current to pass through, and its power flow reversal depends on the reversal of the DC voltage; while the HBSM-MMC type soft DC converter valve allows Bidirectional current flows, but DC voltage cannot be reversed

Secondly, when one end of the DC system (such as the transmitting end or the rectifying end) adopts the LCC-HBSM-HVDC converter valve, if the other end (the receiving end or the inverter end) is affected by an AC fault and causes the DC bus voltage at this end to suddenly When it drops significantly, the LCC-HBSM-HVDC converter valve cannot quickly control the large-scale drop of the near-end DC voltage, so that it cannot suppress the rise of the DC system current

[0010] Although the existing LCC-HBSM-HVDC single-ended cascaded hybrid DC transmission system has advantages in overall operating characteristics and project cost, it is only suitable for The unidirectional power flow operation mode under the unidirectional current constraint cannot realize the bidirectional flow of power flow

At the same time, for the LCC-HBSM-HVDC converter valve, the LCC converter valve is limited by the response speed of the phase control system and cannot quickly control the DC voltage, while the DC voltage fluctuation range of the HBSM-MMC flexible DC converter valve and its Limited, usually the DC voltage drops below 0.9 times the rated voltage and cannot operate. Therefore, the LCC-HBSM-HVDC converter valve composed of the two cascaded with each other cannot control the wide range of DC voltage changes

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