High-voltage Direct Current Power Systems Research Articles

Economic environmental operation in bulk AC/DC hybrid interconnected systems via enhanced artificial hummingbird optimizer

Innovative technologies of multi-terminal high voltage direct current (HVDC), often known as “MTDC,” represent additional features for better active and reactive power control when hybridized with traditional AC power systems. In this sequence, optimal operation in hybrid AC and MTDC power systems becomes highly economically and environmentally necessary. This paper presents an Improved Artificial Hummingbird Optimizer (IAHO) technique for reducing total generation fuel costs, environmental pollution, and whole power losses in AC-MTDC power systems. The proposed IAHO includes a variety of territorial foraging tactics (TFTs) and a Linear Control Process (LCP) which improve both local and universal searching capabilities. The proposed IAHO and AHO are performed on modified IEEE 57-bus and 30-bus hybrid AC and multi-terminal HVDC power systems. The simulation findings declare high economic, environmental, and technical benefits based on the proposed IAHO. A significant reduction in fuel costs, emissions, and losses with 22%, 59.51%, and 71.83% compared to the initial case for the IEEE 57-bus hybrid AC-MTDC power system. Also, the IEEE 30-bus hybrid AC-MTDC power system significantly reduced fuel costs, emissions, and losses by 17.01%, 16.04%, and 28.49% compared to the initial case. Moreover, the significant outperformance of the proposed IAHO is demonstrated over several reported algorithms.

Research on the Transient Interrupting Voltage of Mechanical HVDC Circuit Breaker and Its Influences on the Postarc Dielectric Recovery Process

The flexible high-voltage direct current (HVDC) power system develops quickly with the large-scale utilization of new energy and the increase of direct current (dc) loads in recent years. HVDC circuit breakers are very important components in the flexible HVDC power system. The mechanical HVDC circuit breaker including vacuum interrupters is a potential solution for HVDC interruption. After the current interruption, a transient interrupting voltage (TIV) generated from the interaction with the external circuit will be applied to the mechanical HVDC circuit breakers and might cause a failure interruption. However, there are still few studies about the influences of TIV on the postarc dielectric recovery process of mechanical HVDC circuit breakers. In this article, a circuit model based on the simplification of a 10-kV mechanical HVDC circuit breaker is developed for the purpose of studying the characteristics of TIV. Then the effects of the parallel snubber circuit on the TIV are discussed. Moreover, the influence of TIV on the postarc residual plasma dissipation process is simulated by a particle-in-cell (PIC) model. The results show that the TIV with a parallel snubber circuit has little effect on the whole dissipation time compared with that without a parallel snubber circuit. It should be noted that the microdissipation processes of the above two situations are different.

Editorial: Polymeric materials for HVDC insulation

High voltage direct current (HVDC) power transmission plays a key role in the global power grid today and in the future, particularly for high-capacity, long-distance, and regional power grid interconnections. With the high voltage level of the HVDC power system, the most important concern is the operating safety of polymeric materials as well as solutions for HVDC insulation. During polarity reversal and overvoltages on the HVDC system, polymeric insulation can breakdown in cables, cable accessories, apparatus bushings and gas insulated switchgears. The issues regarding polymeric materials which includes the DC conductivity, charge transportation and partial discharge, have become key problems in restraining the development of the HVDC power system.

Optimized algorithm of active injection circuit to calibrate DC circuit breaker

The widely acknowledged high-voltage direct current (HVDC) technology has now been accepted as a solution of connecting renewable energy sources. However, this technology is vulnerable when facing DC-side faults; due to the low DC impedance, the fault current can rise to an extremely high value in a short time. In addition, when building a multi-terminal DC (MTDC) system, the fault can make a worse failure or blackout of the system when it is not cleared or isolated in time. The urgent need to ensure reliable mentioned HVDC power system can be realized by making use of DC circuit breaker (DCCB). The vacuum CB, which is one division of active DCCBs, has its own operational limit; it can interrupt fault currents when the di/dt of injected current is lower than a critical value, otherwise the arc may reignite. Therefore, the designing and testing of a DCCB must consider this feature. On the other hand, because of the complex configuration of an MTDC system, one DC-side fault can result in different fault currents at faulty line’s terminals; thus, the DCCB needs to be calibrated based on its local fault information. This paper presents an algorithm to optimize the DCCB according to its critical di/dt and local fault current. Furthermore, the operational delay and chopping current of circuit breaker are also considered and modelled. The simulation results from PSCAD platform verify the effectiveness of the presented algorithm.

Decoupled TAB converter with energy storage system for HVDC power system of more electric aircraft

It is an important trend to develop the more electric aircraft (MEA) ±270 V high-voltage direct current (HVDC) power system because of its better reliability, power quality and power density. However, there also exists the low-voltage 28 V DC system in HVDC power system, for the aviation battery and some equipment still rely on it. In traditional MEA power systems, battery is only used as a backup power supply, hardly participating in the adjustment of the power system. On the other hand, the function of turbine engine is unidirectional. Hence, it's necessary to add an energy storage port. In this research, the authors put forward the problems of power coupling and strong non-linearity in traditional three-port triple active bridge (TAB) converters, and propose a decoupled TAB topology, which has the feature of decoupled power flow. The topology is compatible with ±270 V DC, 28 V DC and energy storage system with high-power density and efficiency. In addition, the authors unify the efficiency optimisation problem of dual active bridge topology mathematically and provide an optimal parameter design approach for inductance and turns ratio. Simulation results show the power flow control strategy is appropriate for the topology.

Potential of silicon carbide MOSFETs in the DC/DC converters for future HVDC offshore wind farms

High-voltage direct current (HVDC) is more and more often implemented for long distance electrical energy transmission, especially for off-shore wind farms. In this study, a full DC off-shore wind farm, which requires a high-power and high-voltage DC/DC converter, is considered. In order to reduce the size of the converter, the trend is to increase operating frequency. Silicon carbide (SiC) metal–oxide–semiconductor field-effect transistors (MOSFETs) are becoming industrially available and give scope for the realisation of high-performance DC/DC converters based on modular architectures. This study presents a prospective analysis of the potential of such devices in HVDC power systems. Considering the characteristics of Si insulated-gate bipolar transistor and SiC MOSFET power modules, two DC/DC converter topologies are compared in terms of losses and number of components. In conclusion, a study of the efficiency based on converter energy loss is presented.

Integration of Large-Scale Offshore Wind Energy via VSC-HVDC in Day-Ahead Scheduling

This paper presents a security-constrained unit commitment (SCUC) solution for the optimal integration of large-scale offshore wind energy into a power grid. The solution considers a linear static state representation of multiterminal voltage source converter (VSC)-based high voltage direct current (HVDC) network and effectively incorporates this model into SCUC. The proposed algorithm consists of two major solution components: 1) component implements a SCUC solution for the inland power system; 2) component executes a scheduling of multi-terminal VSC-based offshore HVDC power system. Auxiliary problem principle technique is utilized to coordinate the power injections/withdrawals at HVAC/DC grid interfaces, which are obtained from both the inland and offshore scheduling components. Numerical tests illustrate the effectiveness of the proposed algorithm in the integration of large-scale offshore wind energy into the power grid.

A Study on Maximum Wind Power Penetration Limit in Island Power System Considering High-Voltage Direct Current Interconnections

The variability and uncontrollability of wind power increases the difficulty for a power system operator to implement a wind power system with a high penetration rate. These are more serious factors to consider in small and isolated power systems since the system has small operating reserves and inertia to secure frequency and voltage. Typically, this difficulty can be reduced by interconnection with another robust power system using a controllable transmission system such as a high-voltage direct current (HVDC) system. However, the reliability and stability constraints of a power system has to be performed according to the HVDC system implementation. In this paper, the method for calculation of maximum wind power penetration in an island supplied by a HVDC power system is presented, and the operational strategy of a HVDC system is proposed to secure the power system reliability and stability. The case study is performed for the Jeju Island power system in the Korean smart grid demonstration area.

Improving power system dynamic performance using wide-area high-voltage direct current damping control

A systematic methodology for placement and integration of wide-area measurements in high-voltage direct current (HVDC) damping modulation is developed for large-scale AC/DC power system. A concept observed centre of inertia (OCOI) of power grid is described. For an interconnected AC/DC power network, the frequency difference between the OCOI of the sub-grids can be used as the input signal for HVDC modulation control when the DC link connects two regional power grids. This input contains more useful information of the interarea oscillation modes than the conventionally used signals. In addition, it takes into account the realistic situation of a large-scale power grid. Simulation results for the wide-area control based on the China Southern Power Grid data justify the feasibility and advantage of the phasor measurement unit application in HVDC modulation and power system stability control.

A fuzzy self-tuning PI controller for HVDC links

This paper introduces a fuzzy logic-based tuning of the controller parameters for the rectifier side current regulator and inverter side gamma controller in a high voltage direct current (HVDC) power system. A typical point-to-point system has been taken with the detailed representation of converters, transmission links transformers and filters. The current error (and its derivative) and the gamma error (and its derivative) are used as the principal signals to adjust the proportional and integral gains of the rectifier pole controller and the inverter gamma controller, respectively, for optimum HVDC power system performance under various normal and abnormal conditions. Finally, a comparative study has been performed with and without tuning, to prove the superiority of the proposed control scheme.