A hybrid voltage source converter arrangement for HVDC power transmission and reactive power compensation

IET Generation, Transmission & Distribution

Clare

2016

The recently proposed parallel hybrid modular multilevel converter is considered to be a low loss, low component count converter with soft switching capability of the 'main' H-bridge. The converter has similar advantages to other emerging modular multilevel converter circuits being considered for HVDC power transmission and can be made compact which is desirable for offshore application. However, during ac network unbalance the individual 'chain-links' exchange unequal amounts of power with the grid which requires appropriate remedial action. This paper presents research into the performance of the converter and proposes a suitable control method that enables the converter to operate during grid voltage unbalance. The proposed control concept involves the use of asymmetric third harmonic voltage generation in the 'chain-links' of the converter to redistribute the power exchanged between the individual 'chain-links' and the grid. Mathematical analysis and simulation modelling with results are presented to support the work described.

Section: Introductionmentioning

confidence: 99%

Operation of a hybrid modular multilevel converter during grid voltage unbalance

IET Generation, Transmission & Distribution

Clare

2016

“…Research into the performance of the converter in a balanced network is presented in [7,[9][10][11][12][13]. The converter uses a cascade of half bridge cells to produce a full wave rectified multilevel waveform for each phase according to (1) during balanced network operations according to (2).…”

Section: Introductionmentioning

confidence: 99%

“…At the zero crossing of the chainlink voltage, the 'main' H-bridge units are soft switched to "unfold" the chainlink voltage into AC at the network frequency. Under such operating conditions, it is has been shown that AC-DC power balance can be achieved without the chainlinks having to source or sink power [12]. Although, in practice an appropriate control action is required to achieve AC-DC power balance and ensure sustainable converter operation.…”

Section: Introductionmentioning

confidence: 99%

Control of a hybrid modular multilevel converter during grid voltage unbalance

11th IET International Conference on AC and DC Power Transmission

Wheeler

et al. 2015

Self Cite

The recently proposed parallel hybrid modular multilevel converter is considered to be a low loss, low component count converter with soft switching capability of the 'main' bridge. The converter has similar advantages to other emerging modular multilevel converter circuits being considered for HVDC power transmission. However, during ac network unbalance the individual 'chain-links' exchange unequal amounts of power with the grid which requires appropriate remedial action. This paper presents research into the performance of the converter and proposes a suitable control method that enables the converter to operate during grid voltage unbalance. The proposed control concept involves the use of asymmetric third harmonic voltage generation in the 'chain-links' of the converter to redistribute the power exchanged between the individual 'chain-links' and the grid. Mathematical analysis and simulation modelling with results are presented to support the work described.

“…Each of the topologies offer specific improved converter characteristics or performance such as DC fault ride through [4], low component count [1] and a transformerless converter topology [2] (which affects weight and cost of an HVDC converter station). However, the voltages on the associated capacitors of the many half/full bridge converter units need to be controlled within a tolerance band to ensure sustainable operation of the M2L converter circuit.…”

Section: Introductionmentioning

confidence: 99%

Experimental validation of a parallel hybrid modular multilevel voltage source converter for HVDC transmission

2013 Twenty-Eighth Annual IEEE Applied Power Electronics Conference and Exposition (APEC)

Feldman

et al. 2013

This paper discusses a small scale laboratory model constructed to validate the operation of a recently proposed parallel hybrid modular multilevel voltage source converter which is intended for HVDC applications. The converter is characterized by a 'chainlink' arrangement composed of a number of half bridge cells capable of operating with bidirectional current and an associated full bridge converter for each converter phase arrangement. Each half bridge cell is made up of two bidirectional switches and a local storage capacitor. The voltages on the local storage capacitors of the 'chainlink' cells need to be controlled within a tolerance band to ensure sustainable operation of the converter. The paper also presents a capacitor voltage balancing scheme for this converter and further demonstrates black start capability using a lower rated auxiliary DC source. Four quadrant operation of the converter is also demonstrated as would be expected of a grid connected voltage source converter. Simulation and experimental results are presented to support the converter operation.