Z-source Breaker Research Articles

Detailed Analysis of Classic Z-source Topology for Protection in DC Power Systems

This paper presents an in-depth analysis of the classic Z-source topology for DC power system protection, an area previously unexplored in such detail. Using OpenModelica simulations, the study offers valuable insights into the Z-source topology’s behavior, protection mechanisms, and energy dissipation processes. It includes detailed diagrams, switching states, and explanations of operating principles, supported by waveforms illustrating energy flow through the Z-source components. The findings demonstrate that the Z-source breaker effectively handles fault conditions by disconnecting the source from the load almost instantaneously, within tens of microseconds. The simulations confirm the theoretical models, showing that the Z-source topology efficiently dissipates fault energy through inductors, capacitors, and resistors, thereby protecting sensitive equipment. This thorough analysis enhances understanding of the Z-source topology in DC power systems and establishes a solid foundation for future research and practical applications.

Implementation and impact of graph theory algorithm in Z-source breaker for the protection of DC microgrid

Integrating renewable energy resources is the solution for the power demand crisis in the power energy market, reducing carbon emissions and energy loss. Autonomous acting grids, like DC microgrids, can provide power to rural areas, which neglects grid congestion. However, a proper protection scheme still needs to be determined, as the bidirectional power flow in microgrids exists. Initially, the status of the buses in the network needs to be monitored and addressed continuously so inactive buses are identified and faulted lines are noted easily. Also, the occurrence of a fault may provide a great cause to the nearest renewable generation. So, the distance from a faulted point to the closest operating source are determined to avoid protection blinding. In this study, the active buses are identified using the Kruskal algorithm, the shortest distance from a faulted point to the nearest renewable generation for fault detection is demonstrated, and the run time is compared using Bellman Ford and Dijkstra’s algorithm. The traditional protection scheme can only do fixed relay settings, but the adaptive network works on different relay settings. The proposed system detects the fault and works based on voltage and current data at line ends. Also, the adaptive algorithm is analyzed using a bidirectional Z source breaker when implemented in nine bus DC microgrid system. Result analysis is carried out in MATLAB Simulink interfaced Python scripts for various faults, and the results prove the system’s efficiency, adaptability, and robustness.

Novel bidirectional symmetrical Z-source breaker with adjustable turns ratio of coupled inductor

Novel bidirectional symmetrical Z-source breaker with adjustable turns ratio of coupled inductor

A New Method of Detecting and Interrupting High Impedance Faults by Specifying the Z-Source Breaker in DC Power Networks

High impedance faults (HIFs) that cause a relatively smaller current magnitude compared to the traditional low impedance faults are not easily detectable but can cause an extreme threat to electric apparatus and system operation. This paper introduces a new method of detecting and interrupting HIFs in DC power networks by specifying Z-source circuit breakers (ZCBs). The ZCB is a protective device for high power DC branches, with the capabilities of protecting bidirectional power flow and automatic/controllable turnoff function. In this new method, the operational mode of ZCB (i.e., either the detection mode or interruption mode) can be specified. Beyond previous research, the theoretical analysis has been performed on this method and the mathematical relationship between the maximum HIF resistance and required Z-source capacitance has been derived and verified. It has been found that the ZCB can respond to a HIF accordingly when its capacitances are properly adjusted in the ZCB circuit. With the adjustment of these Z-source capacitances, the ZCB can be specified to detect and report a HIF status to power system operators, or cut off the HIF branch and protect the rest of the DC system directly. The new method can detect/interrupt a HIF that is as small as 2 times of its nominal rated current and the effectiveness and general usage of the derived equation have been verified by both low power experiments in lab and high power simulation tests.

Performance Evaluation of a Modified Bidirectional Z-Source Breaker

An optimized configuration of bidirectional Z-source circuit breaker using a coupled inductor is introduced for the fault isolation in low-voltage dc microgrid. The proposed circuit breaker is designed to operate with a single coupled inductor for bidirectional power flow. Use of the single coupled inductor for the power flow in both the directions reduces the component count. In this article, the operating principle of the breaker is explained for a short-circuit fault condition and breaker design criteria are derived. The performance of the circuit breaker is evaluated by carrying out a MATLAB simulation study. The functional prototype is developed to validate the breaker capabilities. Experimental results show that the fault is cleared within few microseconds. Additionally, the breaker is tested under the step load change condition for a current five times the steady-state rated current of the breaker and results are satisfactory.

DC Fault Protection Strategy for Medium Voltage Integrated Power System: Development and Assessment

In medium voltage direct current (MVDC)-based power distribution scheme DC faults can cause instant disruption in service continuity to various connected loads. Many integrated power systems (IPS) found MVDC as a better replacement of MVAC for detection, isolation as well as protection against DC faults. DC fault protection strategy for developed MVDC-IPS system (which is accompanied by LVDC subsystem), is proposed here by introducing a modified series Z-source breaker circuitry which minimize fault or transient current that reflects back at the DC source by keeping its common ground return path and to re-energize the DC load after fault clearance. The versatility of the proposed idea also include to energize the loads after the fault clearance. The main problem is that a large value of fault/transient current 0 that reflects back at the source and SCR (when it stops commutation). This large reflective current value is much greater than the value of the SCR peak cycle surge value and can damage the SCR permanently. To overcome this problem in the developed technique, an addition of series resistance is made with capacitors which minimize the effect of transient level on SCR and source. Furthermore, due to this resistance the other component size or value is decreased which helps in minimizing the effect of transient current at SCR and source. Another aim is to build the breaker structure in such an optimize way so that to minimize dissipation and weight as compared to its classic structure along with enhancement of efficiency. The proposed strategy of DC fault for IPS is validated through two case studies done in PSCAD simulations.

Integration of Z-Source Breakers Into Zonal DC Ship Power System Microgrids

The next-generation electric ships will feature a medium-voltage dc architecture for distribution of electric power. For higher reliability and flexibility, this dc microgrid is divided into zones each zone having its own protection and load center. The research presented in this paper explores how Z-source dc breakers can be integrated into zonal-based distribution microgrids. Specifically, this paper looks into the practical problems and solutions for running two Z-source breakers in parallel to supply current to the same load center. It is shown that the basic structure of two breakers in parallel can be replicated over a system with multiple zones to protect the entire grid. This paper presents a detailed look into the gate control of the SCRs in Z-source dc breakers. The path of the fault current for shunt faults created at various locations is traced. Using that information, a fault detection algorithm is presented and applied. The measured currents collected during faults and steady state operation will determine the gate signals for the SCRs. The postfault operation might include reclosing of a Z-source breaker if deemed necessary by the control. The simulation and hardware results verify the concepts proposed in this paper.

Analysis and Design of DC System Protection Using Z-Source Circuit Breaker

A modified Z-source breaker topology is introduced to minimize the reflected fault current drawn from a source while retaining a common return ground path. Conventional Z-source breaker topologies do not provide steady-state overload protection and can only guard against extremely large transient faults. The Z-source breaker can be designed for considerations affecting both rate of fault current rise and absolute fault current level, analogous in some respects to a thermal-magnetic breaker. Detailed analysis and design equations are presented to provide a framework for sizing components in the Z-source breaker topology. In addition, the proposed manual tripping mechanism enables protection against both instantaneous current surges and longer-term overcurrent conditions. The fault operation intervals of the proposed Z-source breaker topologies are both demonstrated in SPICE simulation and validated in experimental characterization.

Modified Z-Source Dc Circuit Breaker Topologies

The Z-source dc circuit breaker has been introduced as a new circuit for quickly and automatically switching off in response to faults. A modified Z-source breaker design is introduced for the operation at medium-voltage dc with future applications in naval ship power systems. Compared to existing designs, the respective design will allow for greater control of step changes in load. This new design also limits capacitor current in the circuit and can be easily modified for fault detection. Analysis of the breaker operation is presented during both the fault and step changes in load. Low-voltage laboratory validation of the breaker was carried out on two different versions of the proposed circuit.

A New Z-Source DC Circuit Breaker

A novel type of circuit breaker is introduced for operation at medium-voltage dc with future naval ship power systems as a targeted application. The breaker utilizes a z-source LC circuit in order to automatically commutate a main-path SCR during a fault. Compared to existing dc circuit breakers, the z-source breaker features fast turn-off, simple control, and the source does not experience the fault current. The operation and analysis of the new breaker is presented. Component sizing is carried out for three medium-voltage power levels. Incorporation of the new breaker within a drive system is also explored. Laboratory validation is carried out on a low-voltage prototype.