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Model complexity may have a significant impact on transient stability results of mixed AC/DC systems. The dynamics of various mixed AC/DC models with a focus on different generator orders and multi-level modular converter (MMC) VSC-HVDC model types is investigated within this paper. MMC VSC-HVDC converter models are based on average value model (AVM) and simplified AVM, while 2nd, 3rd and 6th order...
High voltage dc networks are a promising technology to flexibly transmit power over long distances. However, dc grid protection is still a major challenge. DC fault clearance can be mainly achieved with three devices. These are ac circuit breakers (ACCBs), dc circuit breakers (DCCBs) and converters with fault current blocking (FB) capability. In spite of their great operational advantages, FB converters...
Weak AC grids can pose serious interconnection problems by limiting the amount of wind power that can be integrated. Weak AC grids have high transmission impedance compared to strong AC grids. The connection of more wind power generators into weak AC grids may be constrained by voltage instability on the AC grids. This paper analyses and compares the power transfer characteristics of wind farms connected...
As armed forces begin to adopt more widespread use of pulsed-power loads and more capable energy storage solutions, there is a need to consider the electrical system design to best service the expected network loads. The challenges for voltage control, load sharing and stability under fault have strong parallels with those faced by the Electricity Supply Industry (ESI). The work presented in this...
With the proliferation of HVdc systems around the world, the reliability performance of HVdc system and the impact of HVdc systems on the reliability performance of overall power systems is becoming an important issue. In the past, predominantly analytical techniques were used to assess the reliability of HVdc systems. One of the major disadvantages with analytical techniques is that the models of...
This paper investigates the application of unidirectional DC circuit breakers namely current releasing DC circuit breaker in protection of multi-terminal HVDC grids. The design procedure is extended for multi-terminal HVDC grid. Furthermore, a newly proposed fast non-unit protection algorithm is adopted for unidirectional protection of multi-terminal grid. The results of this study confirm that unidirectional...
High Voltage Direct Current (HVDC) grid concept has recently been introduced as the next step to the point-to-point HVDC links to maximise the benefits of more power flow share, and reduce the impact of renewables intermittency. However, the integration of DC grid within existing AC systems is complex and very challenging. The compatibility between the two systems under different operating conditions...
This paper presents a small signal eigenvalue analysis applied to a droop-controlled HVDC terminal based on the Modular Multilevel Converter (MMC) topology. The applied linearised model is derived from previous modelling efforts recently proposed in the literature, which rely on the application of three Park transformations at different frequencies (ω, −2ω and 3 ω) applied to associated variables...
This paper investigates a Wide Area Measurement based robust damping control for multi-infeed VSC HVDC links embedded in the ac system. The feedback signal for the controller design is synthesized from the local and remote signals which results in a good pole-zero separation, which results in improved damping of the swing modes. Furthermore, the paper demonstrates utilization of additional degrees...
Protecting a future HVDC network from short circuit DC faults is presently expected to require extensive implementation of fast HVDC circuit breakers, allowing for rapid fault isolation. The requirement for circuit breakers may, however, be reduced or removed depending on the protection methodology, resulting in a slower post-fault recovery. The expected fault response and the subsequent network recovery...
This research paper presents an unconventional control for the operation of a STATCOM coupled at the interconnection point of the United Arab Emirates and Kuwait in the GCC Interconnection. The primary objective of this research work is to investigate transmission power system network operational control challenges and convincing impact of employing a STATCOM, with an unconventional control algorithm...
Accurately scaled low-powered analogue models of High Voltage Direct Current (HVDC) converters and their operation in real time is a well-established method of validating their operation and performance. Such Small Scale Prototypes (SSPs) are particularly useful in developing and proving control methods in steady state and dynamic conditions, and the transient conditions experienced during AC and...
In large scale distant off-shore wind parks, the generated power is often imported to the mainland via an HVDC transmission link. This kind of off-shore grids can be sensitive to remote end transient recoverable disturbances, as the generation is unable adapt to such events. Measures are required to be incorporated in the system in order to increase the stability of the generation park and the DC...
Application of power electronics for bulk power transfer or integration of remote renewable energy resources into the AC network is at present well-established. Significant proportion of the HVDC transmission schemes are in point-to-point configuration. However, there is an apparent increase in the need for multi-terminal schemes from the perspective of integration of distributed resources or load...
This paper analyses and compares different methodologies for supporting system frequency in low inertia power systems using HVDC interconnectors. Reduced system inertia, caused by the massive integration of converter-interfaced renewables and the displacement of conventional synchronous generation, can result in high values of rate of change of frequency (ROCOF), increasing the risk of frequency stability...
A protection strategy for Multi-terminal HVDC (MTDC) grids based on AC/DC converters without fault handling capability such as half-bridge MMC converters is presented in this paper. The key components of the proposed strategy consist of DC breakers located at each converter station DC side and at each transmission line (overhead line or cable) end, all of them based on low-speed mechanical DC breaker...
ANGLE DC is an innovative project which will convert two existing AC distribution circuits from the island of Anglesey to the Welsh mainland to operate as DC circuits. At present, there is a double circuit 33kV AC connection between the Llanfair PG sub-station on Anglesey and the Bangor 33kV sub-station on the mainland. For the ANGLE DC project, the 3-phases of one AC circuit will be connected in...
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