Laboratory Demonstration of a Multi-Terminal VSC-HVDC Power Grid (original) (raw)
Related papers
Power‐dependent droop‐based control strategy for multi‐terminal HVDC transmission grids
IET Generation, Transmission & Distribution, 2016
The concept of Voltage Source Converter based MultiTerminal High Voltage Direct Current (VSC-MTDC) grids, represents both challenges and opportunities for the future of large power transfer and integration of renewable energy sources. For this kind of grids, the control aspect is of great importance, with voltage-droop based methods considered as one of the most attractive solutions. All existing strategies are designed to maintain the level of voltage in the MTDC grid constant during unexpected events, thus sacrificing the power flow. The aim of this paper is to propose a new droop controller structure that maintains the dc-grid voltage close to the nominal value and at the same time tries to preserve the power flow in the dc grid, following events such as faults or disconnection of stations. The control scheme is presented and simulations are carried out in a four-and five-terminal MTDC grid, proving the validity of the concept. 1
Local and primary controls of a multi-terminal HVDC grid in an experimental setup
2015 17th European Conference on Power Electronics and Applications (EPE'15 ECCE-Europe), 2015
This paper focuses on the experimental implementation of local and primary controls for MT-HVDC in a real test bench (P nom = 6 kW). A local control with two different time scales, one for the current and the other for the voltage, and primary control (droop control), which is responsible to vary the reference voltage when a disturbance appears in the network, are addressed in this paper.
Design considerations for primary control in multi-terminal VSC-HVDC grids
Electric Power Systems Research, 2015
Multi-terminal dc networks based on voltage source converters (VSC) are the latest trend in dc-systems; the interest in the area is being fueled by the increased feasibility of these systems for the large scale integration of remote offshore wind resources. Despite the active research effort in the field, at the moment issues related to the operation and control of these networks, as well as sizing are still uncertain. This paper intends to make a contribution in this field by analyzing the sizing of droop control for VSC together with the output capacitors. Analytical formulas are developed for estimating the voltage peaks during transients, and then it is shown how these values can be used to dimension the dc-bus capacitor of each VSC. Further on, an improved droop control strategy that attenuates the voltage oscillations during transients is proposed. The proposed methods are validated on the dc-grid benchmark proposed by the CIGRE B4 working group. Starting from the structure of the network and the power rating of the converters at each terminal, the output capacitors and the primary control layer are designed together in order to ensure acceptable voltage transients.
Local and primary controls od a Multi-terminal HVDC Grid in an experimental setup
HAL (Le Centre pour la Communication Scientifique Directe), 2015
This paper focuses on the experimental implementation of local and primary controls for MT-HVDC in a real test bench (P nom = 6 kW). A local control with two different time scales, one for the current and the other for the voltage, and primary control (droop control), which is responsible to vary the reference voltage when a disturbance appears in the network, are addressed in this paper.
Power Flow Control in Multi-Terminal HVDC Grids Using a Serial-Parallel DC Power Flow Controller
IEEE Access
Multi-terminal HVDC (MT-HVDC) grids have no capability of power flow control in a self-sufficient manner. To address this important issue, utilization of dc-dc high power and high-voltage converters is motivated. However, proposing suitable partial-rated dc-dc converters as well as their suitable modeling and control in both primary and secondary control layers as well as the stability analysis are the existing challenges that should be alleviated beforehand. This paper addresses the control of power flow problem through the application of a power converter with a different connection configuration, namely, serial parallel dc power flow controller (SPDC-PFC). The SPDC-PFC input is the transmission line voltage, and its output is transmission line current. Therefore, employing a full-power dc-dc converter is avoided as a merit. Additionally, in this paper, the common two-layer MT-HVDC grid control framework comprised of primary and secondary layers is efficiently modified in order to integrate the SPDC-PFC. A differential direct voltage versus active power droop control scheme is applied to the SPDC-PFC at the local control layer, guaranteeing dynamic stability, while an extended dc power-flow routine-integrating the SPDC-PFC-is developed at the secondary control layer to ensure the static stability of the entire MT-HVDC grid. The proposed control framework enables the SPDC-PFC to regulate the flow of current/power in the envisioned HVDC transmission line. From the static and dynamic simulation results conducted on the test CIGRE B4 MT-HVDC grid, successful operation of the proposed SPDC-PFC and control solutions are demonstrated by considering power flow control action. In more detail, the SPDC-PFC successfully regulates the compensated lines' power to the desired reference both in static and dynamic simulations by introducing suitable compensation voltages. In addition, good dynamic performance under both SPDC-PFC power reference and wind power-infeed change is observed. INDEX TERMS Control of power flow, hierarchical control framework, serial-parallel dc power flow controller (SPDC-PFC), MT-HVDC grids, voltage source converter.
2014 Power Systems Computation Conference, 2014
The HVDC links are increasingly used not only to interconnect asynchronous AC systems but are also embedded into a same meshed AC power system. Thanks to its speed and flexibility, the HVDC technology is able to provide transmission system advantages as transfer capacity enhancement and power flow control. In addition, studies have shown that the way of controlling the HVDC converters impacts the stability of the AC system. This can be particularly exploited to enhance the dynamic power system performances during transients. In this paper a robust multivariable control design for HVDC link converters is proposed. It is based on the coordination of the control actions of the HVDC converters and the use of a control model which takes into account the dynamics that mostly impact stability of the neighbor zone of the HVDC link. This new methodology was used to synthesize the controller for an actual grid 1000 MW HVDC link reinforcement project called "Midi-Provence" in the southern part of the French grid. The synthesis, implementation and validation processes are presented in detail. The new controller is tested in comparison with the standard vector control. A large-scale dynamic model of the whole European power system, currently used and updated by the European TSO's for the interconnection studies has been used with Eurostag simulation software.
Voltage Stability Improvement in Multi-Terminal HVDC grids: A Case Study of Cigré B4 HVDC Test Grid
56TH INTERNATIONAL UNIVERSITIES POWER ENGINEERING CONFERENCE, 2021
High voltage direct current (HVDC) breaker is among the essential components of HVDC grids. Currently, DC circuit breakers (DCCBs) of HVDC grids require relatively large DC reactors to limit the rate of increase of fault current. However, DC reactors have destructive effects on the multiterminal HVDC (MT-HVDC) grid dynamic stability, and in such a system, despite the variety of controllers, the system dynamics are highly sensitive to the operating point. This paper proposes a modification to be applied to the droop control of Multi-terminal HVDC (MT-HVDC) grids for stabilizing the DC voltage and power variations in case of transient events by the introduction of a Dead Band Direct Current Power System Stabilizer (DBDC-PSS). Also, this paper presents the classification of MT-HVDC grid dynamic behavior in different scenarios including without DC-PSS, conventional DC-PSS, and DBDC-PSS. All simulations and analytical studies are conducted on Cigré DCS3 test HVDC grid in MATLAB/Simulink.
Implementation of DC voltage controllers on enhancing the stability of multi-terminal DC grids
International Journal of Electrical and Computer Engineering (IJECE), 2021
Because of the increasing penetration of intermittent green energy resources like offshore wind farms, solar photovoltaic, the multi-terminal DC grid using VSC technology is considered a promising solution for interconnecting these future energies. To improve the stability of the multi-terminal direct current (MTDC) network, DC voltage control strategies based on voltage margin and voltage droop technique have been developed and investigated in this article. These two control strategies are implemented in the proposed model, a ±400 kV meshed multi-terminal MTDC network based on VSC technology with four terminals during the outage converter. The simulation results include the comparison and analysis of both techniques under the outage converter equipped with constant DC voltage control, then the outage converter equipped with constant active power control. The simulation results confirm that the DC voltage droop technique has a better dynamic performance of power sharing and DC voltage regulation.
IEEE Transactions on Power Delivery, 2021
In this paper, a reliable methodology is proposed in order to implement and validate a Model Predictive Control (MPC) scheme on an actual Voltage Source Converter (VSC) integrated in a scale-down multi-terminal DC grid. The objective of the investigated MPC controller is to enable AC frequency support among two asynchronous AC areas through a High Voltage Direct Current (HVDC) grid, while considering physical constraints, such as maximum and minimum DC voltage. A systematic and accurate implementation strategy is proposed, based mainly on the Hardware In the Loop (HIL) and Power Hardware In the Loop (PHIL), leading to the real-life testing on VSC, controlled by a classical microcontroller. The technical problems during the implementation process, as well as the proposed solutions, are described in detail through this paper. This procedure is deemed valuable to bridge the gap between offline simulation and the actual implementation of such advanced control scheme on experimental test rig.
Renewable Energy, 2017
New high voltage direct current (HVDC) installations are expected to be able to provide stability support to the main synchronous networks to which they are connected. In multi-terminal HVDC (MTDC) schemes incorporating offshore wind farm this issue could be addressed by setting aside a reserve of wind energy by the curtailment of wind turbine generators (WTGs). This paper proposes a communication-less dc voltage cooperative control strategy for MTDC transmission systems. A grid side converter, the master, and a wind farm are designed to work cooperatively to maintain a stable dc link voltage, facilitating normal power dispatch orders and the provision of frequency support. The proposed control maintains a wind energy reserve and uses a flexible dc link voltage at the master converter. Allowing the local master dc voltage to vary within certain limits encourages the wind farm to participate in dc link voltage control and hence no communication system is required. The master converter automatically assumes control of the dc link voltage in the absence of wind or when the wind reserve is used up. A four terminal MTDC system comprising one master converter, two active/reactive power converters and one wind farm is studied. The effectiveness of the proposed control strategy is validated through simulation using MATLAB ®-SIMULINK ® .