Hybrid DC circuit breaker with coupled inductor for automatic current commutation

HVDC transmission systems using voltage source converters (VSC-HVDC) have been identified as an attractive solution for bulk power delivery over long distance. However if DC grids are to be built using this technology, fast DC circuit breakers are needed. This work proposes a new hybrid DC circuit breaker utilizing a series connected coupled inductor connected, which enables automatic current commutation from the mechanical switch to the semiconductor switch during a fault. The key advantage of the proposed DC circuit breaker is that the current in the mechanical switch automatically reduces to zero when a fault happens. This paper focuses on comparison of different mechanisms to commutate the current from the mechanical switch to the semiconductor switch and create a zero current for the mechanical switch. Three types of hybrid DC circuit breaker topologies including proactive hybrid DC circuit breaker, hybrid DC circuit breaker with commutation booster, and hybrid DC circuit breaker with coupled inductor for a 500 kV HVDC system are simulated and compared using Matlab/Simulink. A prototype hybrid DC circuit breaker with coupled inductor is designed and built. The prototype is capable of interrupting 200 A direct current within 4 ms. The automatic current commutation compensates for the fault detection and location time in the selective protection scheme, which provides faster fault current interruption

A new direct current circuit breaker with current regeneration capability

Direct current (DC) power systems are becoming very popular due to better control ability and equipment reliability thanks to the continuous development of power electronics. A DC circuit breaker (DCCB) used for current interruption in a DC network is a major part of the system. It plays the vital role of isolating networks during fault clearing as well as during normal load switching. Breaking the DC current is a major challenge as it does not have any natural zero crossing points like the AC current has. In addition, energy stored in the network inductances during normal operation opposes the instantaneous current breaking. Hence, all the conventional DC circuit breaker topologies use lossy elements to dissipate this stored energy as heat during the current breaking operation. However, it is possible to store this energy and reuse it later by developing an improvised topology. In this paper, the prospects of energy recovery and reuse in DC circuit breakers have been studied, and a new topology with regenerative current breaking capability has been proposed. This new topology can feed the stored energy of the network back into the same network after breaking the current and thus can improve the overall system efficiency

Prospects of regenerative current breaking in DC circuit breaker topology

Due to the stunning advancement of power electronics, DC power system is getting immense attention in the field of research. Protection and hereafter the protective devices for the DC power system application are two vital areas that need to be explored and developed further. Designing a protective device such as DC circuit breaker possesses a lot of challenges. The main challenge is to interrupt a current which does not have a natural zero crossing like AC current has. In addition, energy is stored in the network inductances during normal operation. Instantaneous current breaking is opposed by this stored energy during circuit breaker tripping, hence, all the DC circuit breaker topologies proposed in literature use snubber network, nonlinear resistor to dissipate this stored energy as heat during the current breaking operation. However, it is possible to store this energy momentarily and reuse it later by developing an improvised topology. In this paper, the prospects of energy recovery and reuse in a DC circuit breaker was studied and a new topology with regenerative current breaking capability had been proposed. This new topology can feed the stored energy of the network back into the same network after breaking the current and thus can improve the overall system efficiency

Modernisation of a traction system for metro vehicles

Thanks to the arrival of the new metro MPL16 and the obsolescence of the MPL75 traction chain, it was necessary to consider a switch between the current MPL75 traction chain and the new generation of the MPL16 traction chain (asynchronous motor). A comparison between DC Motor and Asynchronous Motor revealed that the second one is more robust, requires low maintenance and is lighter and smaller than the DC Motor for the same output power. To determine if the MPL16 traction chain can work on the MPL75, some simulations of traction performances in different modes, travel time and consumed energy were done. Following the results, with an addition of a boost to cross the maximum slope of the line A, the MPL75/NewGeneration (with the MPL16 traction chain) corresponds to our need. In addition, the difference of the travel time is negligible and the MPL75/NG consumes much less energy than the current MPL75 traction chain. Finally, it was necessary to verify the feasibility of the installation in the MPL75 and to evaluate the benefits of this modification. Financially and mechanically, this modification is possible and benefic. In fact, if we change the MPL75 traction chain, we can have a gain on the consumed energy and on the labor cost. In addition, it allows to have only one equipment for two different metros (more comfortable for the maintenance workshop).Thanks to the arrival of the new metro MPL16 and the obsolescence of the MPL75 traction chain, it was necessary to consider a switch between the current MPL75 traction chain and the new generation of the MPL16 traction chain (asynchronous motor). A comparison between DC Motor and Asynchronous Motor revealed that the second one is more robust, requires low maintenance and is lighter and smaller than the DC Motor for the same output power. To determine if the MPL16 traction chain can work on the MPL75, some simulations of traction performances in different modes, travel time and consumed energy were done. Following the results, with an addition of a boost to cross the maximum slope of the line A, the MPL75/NewGeneration (with the MPL16 traction chain) corresponds to our need. In addition, the difference of the travel time is negligible and the MPL75/NG consumes much less energy than the current MPL75 traction chain. Finally, it was necessary to verify the feasibility of the installation in the MPL75 and to evaluate the benefits of this modification. Financially and mechanically, this modification is possible and benefic. In fact, if we change the MPL75 traction chain, we can have a gain on the consumed energy and on the labor cost. In addition, it allows to have only one equipment for two different metros (more comfortable for the maintenance workshop)

A Coupled Inductor Based SSCB With Reduced Components for DC Microgrid Protection

DC microgrids have gained importance for their high efficiency, no need for synchronization, high power quality, and potential to reduce greenhouse gas emissions. Ensuring reliable and fast protection against over current and shor-circuit faults is considered to be a challenge even to date. Solid-state circuit breakers offer a promising solution, providing rapid and arc-less fault clearing. However, SSCBs employing fully controlled devices lead to higher costs and conduction losses. This paper discusses a cost effective circuit breaker, using a semi-controlled switch based on a coupled inductor. The proposed SSCB has reduced overall components, a discharged capacitor and also allows the option to trip manually for maintenance. A detailed analysis and design methodology for component selection is presented in the later sections. The SSCB is experimentally validated by developing a laboratory prototype for a voltage rating of 400 V and at a nominal current of 15 A & 20 A with a short circuit fault current of 60 A

Evaluation methodology for DC line fault clearance techniques in a point-to-point VSC-HVDC transmission system

This thesis examines and compares various DC fault clearance methods that can be used for the VSC-HVDC transmission system, specifically in the context of a point-to-point VSC HVDC transmission system. The newest conceptual research, prototype development. and real implementations are described in depth through the literature review. An analytical evaluation methodology is developed to compare the performance, capability, losses, and cost of different DC fault clearing techniques. Finally, a comparative analysis is conducted to evaluate the DC fault clearing solution using a full-bridge modular multilevel converter and a half-bridge modular multilevel converter with DC breakers using PSCAD/EMTDC software.February 202

Definition study for photovoltaic residential prototype system

A site evaluation was performed to assess the relative merits of different regions of the country in terms of the suitability for experimental photovoltaic powered residences. Eight sites were selected based on evaluation criteria which included population, photovoltaic systems performance and the cost of electrical energy. A parametric sensitivity analysis was performed for four selected site locations. Analytical models were developed for four different power system implementation approaches. Using the model which represents a direct (or float) charge system implementation the performance sensitivity to the following parameter variations is reported: (1) solar roof slope angle; (2) ratio of the number of series cells in the solar array to the number of series cells in the lead-acid battery; and (3) battery size. For a Cleveland site location, a system with no on site energy storage and with a maximum power tracking inverter which feeds back excess power to the utility was shown to have 19 percent greater net system output than the second place system. The experiment test plan is described. The load control and data acquisition system and the data display panel for the residence are discussed