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Weixing Lin - IEEE Xplore Author Profile

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The energy storage converter is the bridge between the battery system and the grid. In this paper, a two-stage topology is used to add a Buck/Boost type bidirectional DC/DC converter topology between the DC side capacitors of the energy storage unit and the power sub-module, so that the DC side capacitor is not directly connected in parallel with the battery and the impact of the DC side second ha...Show More
As new energy sources play an increasingly important role in the energy supply system and control the development of power semiconductor devices, a wide variety of power semiconductor devices have become an integral part of industrial, consumer and scientific research. Modular multilevel converter (MMC) has the characteristics of small switching loss and low output voltage harmonic distortion wind...Show More
With the rapid development of distributed photovoltaic industry and new energy electric vehicles as well as flexible DC transmission, the phenomenon of three-phase imbalance in the distribution station area is becoming more and more serious. The phase change switch can solve the problem of three-phase unbalance by regulating the load balance and has been applied in the power grid. However, the cur...Show More
To integrate large-scale islanded onshore wind power with different sizes, this paper proposes an integration system based on the cascaded hybrid HVDC transmission system, which consists of LCC and several MMCs in series connection at the DC side of the rectifier. A large-scale wind farm is connected with one LCC and one MMC while several small-scale wind farms are connected with MMCs directly. Ow...Show More
Primary single-end line protection strategies of modular multilevel converter (MMC)-HVdc systems are difficult to make a tradeoff between fast detection speed and high reliability. To improve reliability, the pilot protection schemes based on communication and data exchange can be adopted. However, the communication-based schemes suffer from potential communication failure problems, such as data e...Show More
The wideband oscillation of the hybrid modular multilevel converter (MMC)induced by excessive power infeed under weak ac power system integration is analyzed in this article. A closed-loop state-space-based time-domain small-signal model is firstly established to investigate the instability problem. Different from the findings in two-level voltage-source-converters (VSCs) or half-bridge MMCs, the ...Show More
Voltage source converters (VSCs) with self-commutation ability are suitable for interconnecting weak ac systems. This article conducts a comparative study of the small-signal stability characteristics for three typical VSCs, namely, the two-level VSCs (TL-VSCs), the half-bridge modular multilevel converters (HB-MMCs), and the hybrid MMCs (HY-MMCs), under weak ac system integration with special con...Show More
This paper proposes an adaptive fault current limiting control (AFCLC) for modular multilevel converters (MMC). Without introducing extra current limiting devices, this control scheme enables fast fault current suppression during DC faults. The AFCLC will be triggered automatically once DC faults occur. By adaptively reducing the output DC voltages of MMCs, the fault current can be suppressed. Com...Show More
A novel fault current limiting control for half-bridge modular multilevel converters (MMC) is proposed in this paper. This control scheme is able to limit the fault current without implementing extra devices. It will be triggered automatically once DC faults occur and can suppress the fault current by reducing the output DC voltages of MMCs. Compared with the existing fault current limiting method...Show More
This paper proposes a cascaded converter dedicated to a long-distance high-voltage direct current (HVdc) infeed and asynchronous back-to-back interconnection of receiving grids. The cascaded converter consisted of modular multilevel converters (MMCs) in series and parallel connection, meeting the high dc voltage and power demand of the HVdc system. It realizes the hierarchical feeding and asynchro...Show More
To handle with the DC line faults in a DC grid, this paper proposed an active current-limiting controller for hybrid MMC. With this active current-limiting control strategy, the requirement of interruption current of DCCB will be significantly decreased, and the investment of DC grid will be reduced obviously. Firstly, the control architecture of active current-limiting controller is disclosed. To...Show More
Fast and reliable DC fault detection is one of the main challenges for modular multilevel converter (MMC) based DC grid with DC circuit breakers (DCCBs). This paper extracts the high-frequency components in transient voltages by wavelet transform and proposes a fault identification method based on the difference of square of transient voltages to identify the faulted lines for DC grids using overh...Show More
Due to the hybrid composition of half-bridge submodule (HBSM) and full-bridge sub-module (FBSM) in each phase arm, hybrid modular multilevel converter (MMC) is able to actively adjust the output DC voltage and operate under reduced DC voltage. Sub-module balancing is one of the most concerned issues regarding low DC voltage operation. This paper analyzes the impact of sub-module balancing constrai...Show More
Hybrid high voltage direct current circuit breakers (DCCBs) are capable of interrupting a fault current within a few milliseconds, but this technology suffers from high capital costs, especially in a meshed HVDC grid. To increase the economic competitiveness of hybrid DCCBs, this paper proposes a capacitor commutated DC circuit breaker (CCCB). The CCCB mainly comprises an auxiliary branch with a f...Show More
This paper studies protection and control methods for a large dc grid based solely on full-bridge modular multilevel converters (MMCs). An initial theoretical study concludes that dc circuit breakers (CB) energy dissipation will depend on inductance and square of fault current, but not on protection operating time. Using differential protection is proposed because of robust selectivity and since i...Show More
This paper presents an enhanced independent pole control scheme for hybrid modular multilevel converter based on a full-bridge submodule and half-bridge submodule. A detailed analysis of the power distribution between upper and lower arms under asymmetrical dc pole voltages is presented. It is found that the fundamental ac currents in the upper and lower arms are asymmetrical. To enable operation ...Show More
This article studies the protection of DC grid based on full bridge (FB) MMC and mechanical DC circuit breakers. A four terminal DC grid cropped from the CIGRE B4 DC grid test system is used as the studied system. Three level cascaded controllers are installed at each FB MMC, along with central DC grid dispatcher. In the proposed approach FB MMCs are operated through DC faults exploiting FB MMC ca...Show More
It is a necessity to use DC-DC transformers when interconnecting two DC systems with different voltages levels. This article designs the prototype of bidirectional DC-DC autotransformer (DC AUTO) and voltage step-up unidirectional DC AUTO (UUDAT). The article firstly illustrates the electrical primary system in experimental prototype, then studies its control strategy and the corresponding control...Show More
Compared with half bridge MMC, the hybrid MMC based on full bridge sub-modules (FBSM) and half bridge sub-modules (HBSM) has more control freedoms. It has been reported that the hybrid MMC can regulate the cell capacitor voltages independent of the DC-link voltage. Thus it is able to ride through pole-to-pole DC fault without tripping IGBTs. But few literatures studied the fault ride through contr...Show More
Three-channel controller of FB-MMC HVDC that enables four-quadrant operation on DC side and fault ride through on AC and DC sides without blocking IGBTs is proposed. Phasor modeling of FB MMC is studied to provide insight into independent AC and DC control. Three modulation indices are used: the conventional d-axis, q-axis AC-side modulation indices Md, Mq and a newly proposed DC modulation index ...Show More
Self-blocking modular multilevel converter (SB-MMC) is able to block dc fault current with relatively lower number of power semiconductors and lower valve power loss compared to other dc fault tolerant MMC topologies. Operating principle, design, reliability, and redundancy analysis of SB-MMC have been studied while the equivalent modeling and application of SB-MMC at overhead VSC-HVDC have not be...Show More
This paper proposes a simple and accurate average value model (AVM) of a high-power half-bridge MMC for electromagnetic-transient (EMT) studies. Least number of generic EMT blocks is used. Functioning as voltage source converter (VSC), the accuracy of a simplified MMC model would eventually be determined by its accuracy in reproducing the cell charging/discharging dynamics of the detailed models u...Show More
Self-blocking MMC (SB MMC) is able to isolate DC fault current and is promising for use in overhead HVDC transmission. Each converter arm of a SB MMC is consisted of half the self-blocking sub-module (SBSM) and half the half bridge (HB) sub-module. This hybrid design achieves the DC fault isolation capability without significantly increase of the cost and power loss. The detailed electro-magnetic ...Show More
Design and operation of FB (full bridge) MMC that meets HVDC specifications are studied in this paper. Three new design parameters: the over-modulation index (kMMC), the DC modulation index (Mdc), the minimal DC voltage (Vminpu) are introduced to specify the operation of a FB MMC. Power increase and semiconductor count increase with the increase of kMMC is analyzed to understand benefits of over-m...Show More
Modelling of Modular Multilevel Converter (MMC) for electromagnetic transient type (EMT-type) simulations is challenging due to numerous IGBTs/diode devices. Detailed models of HVDC-MMC transmission systems require long computation times. Simplified models have been proposed in the past to overcome this problem. However, some of these types of model require a hard-coding development which depends ...Show More