Research On DC Solid-State Rapid Breaking Device For Low-Voltage Ship

The development of marine DC power systems has put forward new requirements for low-voltage DC interruption.The typical characteristic of DC system interruption is that it does not generate natural zero crossings like AC systems.In the traditional DC system,when the fault is removed,it is disconnected by mechanical contact points.Because of the inductance in the line,an arc will be generated when the current is interrupted,which will cause large losses to the contacts in the mechanical switch.If the load has a serious failure,the mechanical circuit breaker will turn off relatively slowly,which may affect the stable operation of the DC system.In view of the slow breaking speed of traditional circuit breakers and the problem of arcing during the breaking process,solid state circuit breakers using power semiconductor devices are more suitable for fault protection of DC systems.According to the structural characteristics of the low-voltage marine DC power distribution system,the technical requirements of the DC power system for switching off are summarized.The basic structure of DC solid-state circuit breakers is introduced.The working principles of DC solid-state circuit breakers with two different control strategies,semi-controlled and full-controlled,are analyzed.The performance of the two types of circuit-breakers is compared.The comprehensive performance of the DC solid-state circuit breaker is more prominent,which will be the focus of this paper.First,the thyristor device structure and forward and reverse characteristics are introduced,and the Z source DC solid state circuit breaker parameter design theory is derived by combining the Z source network circuit,including: the relationship between the minimum fault current that triggers the breaker to switch off and the device parameters;Minimum rise rate of fault current;theoretical basis for parameter design of related components in the Z-source network;change law of thyristor reverse recovery time.The simulation software was used to model and simulate the Z-source circuit breakers of three topologies.Through the simulation results,it can be seen that the off-time and current peak value of the thyristor-based semi-controlled DC solid-state circuit breaker are determined by the parameters of the Z-source network device The shutdown characteristic is stable,which is consistent with the theoretically derived results.According to the voltage transfer function and the Bode diagram,the amplitude-frequency characteristics of the three topologies are analyzed.Compared with the other two topologies,the series Z-source DC solid-state circuit breaker has the best breaking performance and low-pass filter characteristics.Based on the series Z-source DC solid-state circuit breaker,a bidirectional Z-source DC solid-state circuit breaker topology is proposed.The working principle of bidirectional normal operation is analyzed,and the bidirectional fault interruption design is mainly studied,including the minimum current that triggers the circuit breaker to be turned off during the load side fault and the power side fault,the minimum rise rate of the fault current,the peak voltage and current of the internal components.Finally,the derived theoretical formula was verified by the simulation software PLECS and an experimental platform.The experimental results prove that the proposed bidirectional Z-source DC solid-state circuit breaker can be quickly turned off when a short-circuit fault occurs,effectively protecting the power supply and the load.When the relevant parameter settings in the Z source network do not meet the theoretical derivation value,the circuit breaker cannot remove the fault,which proves that the relevant theoretical derivation is valid.In addition,the series bidirectional Z-source DC solid-state circuit breaker not only has a fast switching speed,but also has the advantages of small size and low manufacturing cost,which is conducive to being put into practical application as soon as possible.