277 results about "DC distribution system" patented technology

A method for locating phase to ground faults in DC distribution systems. The method includes utilizing wavelet analysis using Multi-Resolution Analysis (MRA) as a signal processing tool for recognition of characteristic features in the voltage signal. The voltage signal contains characteristic information in the high frequency range above the switching frequencies of the PE converters which allows for localization of the fault.

The invention discloses a ship direct current distribution system with conversion of electrical energies. The ship direct current distribution system comprises at least two sets of redundant direct current distribution subsystems and an important load distribution box, wherein power supply is acquired from a generator or a reserve storage battery; each set of direct current distribution subsystem comprises a direct current main distribution box and a distribution unit with conversion of electrical energies; the direct current main distribution box is used for supplying power to different electric loads through the distribution unit with conversion of electrical energies; the important load distribution box is automatically switched between the direct current distribution subsystems and is used for uninterruptedly supplying power to the important load. The ship direct current distribution system provided by the invention can meet the requirements of power supply and control for different electric area loads; direct current electric transmission and distribution electrical energy are applied to the direct current distribution system, so that the power supply contact between the distribution boxes is reduced; the power supplies of the distribution boxes are independent from each other and the distribution network is simplified; the online insulating monitoring for power distribution loop of the whole system is realized; the safe and reliable running of the distribution system is benefited; layered distribution and drawer design are applied to the structures of the distribution boxes; the function integration level is high; the space usage is less; the control is conveniently performed.

The invention relates to an adaptive droop control method applicable to a flexible DC distribution system, which combines adaptive control, predictive control and the traditional droop control mode and proposes a novel droop control strategy applicable to additional DC voltage deviation compensation of the flexible DC distribution system and adaptive adjustment of each droop coefficient accordingto the maximum dynamic power margin. The model predictive current control is introduced to further improve the response speed of the system control. The adaptive droop control not only realizes floating control of the DC voltage, but also can automatically optimize the droop coefficients, thereby enabling the droop curve of each converter station to adaptively shift according to the dynamic powermargin principle, reasonably distributing the unbalanced power, and being well applicable to the flexible DC distribution system.

The invention relates to a DC distribution system energy storage device adaptive virtual impedance droop control method, which is applied to multi-converter parallel control in a DC distribution system. The method comprises the steps of 1) acquiring electric power parameters of the DC distribution system, establishing a double closed-loop controller which consists a voltage outer loop and a capacitive current inner loop, and establishing a DC distribution system droop control model; 2) introducing virtual impedance ZD(s) into a part between converter output current and converter reference voltage signals of the double closed-loop controller in the DC distribution system droop control model so as to act as negative feedback, and acquiring equivalent output impedance Zov(s); and 3) enabling the equivalent output impedances Zov(s) corresponding to a plurality of lines to be equal through setting values of different virtual impedances ZD(s), and thus averaging output power and power distribution of the plurality of lines in the DC distribution system. Compared with the prior art, the method provided by the invention has the advantages of shock suppression, simple algorithm, low cost and the like.

The invention provides a single-phase power electronic transformer. The single-phase power electronic transformer comprises an input-stage circuit, a middle isolating-stage circuit and a DC-AC (direct current-alternating current) inverter, wherein the input-stage circuit comprises a first bridge arm and a second bridge arm; the first bridge arm and the second bridge arm are connected between a positive input end and a negative input end of a high-voltage direct-current bus; the first bridge arm comprises two capacitors which are connected with each other; a connecting line between the two capacitors is connected with an input end of a high-voltage alternating-current bus; an upper half bridge arm and a lower half bridge arm of the second bridge arm comprise a plurality of modular multi-level SM (signal modules); and a connecting line between the upper half bridge arm and the lower half bridge arm is connected with another input end of the high-voltage alternating-current bus. A single-phase half-bridge rectifying circuit is formed by the whole input-stage circuit. The single-phase power electronic transformer is suitable for a high-voltage single-phase rectifier system. Moreover, the power electronic transformer is provided with an alternating-current and direct-current mixed input interface, not only is suitable for an independent alternating-current or direct-current power distribution system, but also is suitable for an alternating-current and direct-current mixed power distribution system. Functions of transformation isolation and power transmission between power grids with different types and voltage classes can be fulfilled.

The invention discloses an intelligent DC power distribution center-based urban distribution network grid structure, which comprises more than two groups of 10KV back-to-back multi-terminal DC power distribution systems, wherein each 10KV back-to-back multi-terminal DC power distribution system comprises an AC/DC converter and a DC/AC converter; four shutdown switches are connected between the AC/DC converter and the DC/AC converter in series; adjacent 10KV back-to-back multi-terminal DC power distribution systems are connected with each other through a sixth shutdown switch and a seventh shutdown switch; the sixth shutdown switch is connected between output ends of the first shutdown switches of the adjacent 10KV back-to-back multi-terminal DC power distribution systems; the seventh shutdown switch is connected between the output ends of the third shutdown switches of the adjacent 10KV back-to-back multi-terminal DC power distribution systems; and the input ends of the converters are connected through four groups of feeders connected with interconnection switches to form the grid structure. The technical problem that the prior art cannot adapt to a complicated power system, and especially the technical problems in the aspects of reliability improvement, control power flow adjustment, distributed power supply connection and the like are solved.

The invention relates to the field of power system relay protection, in particular to a protection scheme for a direct current distribution system short-circuit fault. The scheme includes the steps that firstly, if the sudden-change amount of the direct voltage exceeds a setting value, bus and circuit protection is started; secondly, after the bus protection is started, if the differential current is larger than the differential protection current setting value, bus protection actions are carried out, and direct current breakers at all power supply sides are tripped off; thirdly, after circuit protection is started, if the circuit currents are larger than the instantaneous quick-break protection current setting value or after protection is started for a period of time and the circuit currents are still larger than the time limit quick-break protection current setting value, a circuit is judged to break down, and the direct current breakers on the faulty circuit is disconnected immediately. The protection scheme has the advantages of being simple in protection principle, good in rapidity when faults occur and high in reliability.

A direct current (DC) power distribution system includes a first electrical distribution and power management (EDPM) unit including a first DC power source connected to a first high voltage DC bus connected to a first DC load, and a first bus-tie solid state power controller (SSPC) connected to the first HVDC bus; a second EDPM unit including a second DC power source connected to a second high voltage DC bus connected to a second DC load, and a second bus-tie SSPC being connected to the second HVDC bus; and a bus-tie connected between the first bus-tie SSPC and the second bus-tie SSPC, wherein in the event a power source failure occurs in the first EDPM unit, power flows from the second DC power source to the first HVDC bus via the second bus-tie SSPC, the bus-tie, and the first bus-tie SSPC.

A high voltage DC power distribution system that eliminates static switches and batteries. Flywheel energy storage devices and extremely reliable, high power DC/DC converters provide at a lower cost, more reliable, noise and harmonic free, critical electrical power directly at equipment racks at 48 VDC, 24 VDC, 6 VDC, 2 VDC, or any other desired DC voltage level.

The invention discloses a protection configuration method for a typical multi-terminal flexible direct current power distribution system. The typical multi-terminal flexible direct current power distribution system is divided into an alternating current system protection region, a main converter protection region, a direct current line protection region and an access converter protection region; and a protection scheme is configured for each protection sub-region by combining the operating requirements of the direct current power distribution system and the factors of fault and electrical characteristics and the like on the basis of division of the protection regions. The scheme can comprise different protection algorithms, which can protect the safety of equipment in the region, and simultaneously can be used as backup protections of other regions. Configuration of protection devices is to determine the installation positions and the number of the protection devices, employing simplicity, convenience and reliability as principles. According to the method, the fault position in the direct current power distribution system can be quickly and reliably judged; fault removal and isolation are achieved; stable operation of the multi-terminal flexible direct current power distribution system can be ensured; and the protection configuration method has certain guiding significance in follow-up study of the protection system.

A power management system for distributed power management from a power source to a plurality of power units, using a monitor bus to monitor total power usage on a branch to which the power unit is assigned, allowing power to be delivered if it won't result in a maximum current draw from the power source being exceeded, and denying access if it would. Each power unit adds a signal to the monitor bus proportional to the current it is drawing from the power source.

A direct current power system according to one non-limiting embodiment includes a direct current power source operable to distribute a direct current voltage throughout at least one structure, and at least one controller operable to selectively couple a direct current load to the direct current voltage in response to a wireless signal from an energy-harvesting switch.

The invention discloses an insulative matching method for an intelligent power distribution system based on a flexible direct current. The topological structure, the mode of operation and the mode of malfunctions of the intelligent power distribution system based on the flexible direct current are comprehensively analyzed by the following steps: carrying out system analysis; configuring a lightning arrestor; carrying out simulating calculation of an overvoltage; setting insulative match. On the basis, the lightning arrestor is initially configured for the system and simulating calculation of overvoltage is conducted by establishing an inner overvoltage calculation model and a lightning overvoltage calculation model of the system so as to adjust the configuration of the lightning arrestor and the accomplish insulative match of equipment of the system, so that the system cost is the minimum while the system safely and stably operates. The scheme can be used for guiding related technical staff to efficiently carrying out insulative match analysis of a flexible direct current power distribution system.

The invention discloses a flexible direct current distribution system fault positioning method based on a traveling wave, and belongs to the technical field of the distribution system fault positioning method. The invention presents a multi-port looped network type flexible direct current system fault positioning method based on the minimum fault time of the travelling wave specific to a complex structure of a multi-port flexible direct current system and the transmission characteristics of the travelling wave. The network topology of the complex multi-port flexible direct current system is expressed by a picture. And then it can be judged if the fault happens on a radiation line or the inner part of the looped network. For the fault at the inner part of the looped network, the fault starting moment when every line goes wrong is calculated and compared, thus the fault branch is found, and the fault point is calculated. The flexible direct current distribution system improves the calculation speed of the algorithm on the basis of guaranteeing the calculation precision; it is very important to the direct current network of which response time is much more than that of the alternating current system.

The invention provides a protection method for a DC power distribution system with a resistance type superconducting current limiter. DC voltage and DC current information acquired from the installing part of head end protection of all feed-out lines is utilized, the voltage sudden variable principle is applied to act as fault starting elements of DC buses and DC lines, the transient peak over-current protection principle is applied to act as I-phase protection of the DC lines, and transient over-current started time-limited undervoltage protection is applied to act as II-phase protection of the DC lines based on DC circuit breakers so that the overall length of the lines is protected. Influence on protection of the DC power distribution system caused by accessing of the current limiter can be effectively avoided, and fault lines can be rapidly cut.

The invention provides a power flow calculation method for a flexible interconnecting alternating current-direct current hybrid power distribution network. The power flow calculation method comprises the steps of A, establishing an alternating current power distribution system model and a direct current power distribution system model; B, disassembling the alternating current and direct current hybrid power distribution system; C, establishing a mathematical model for a power exchange interface between an alternating current sub network and a direct current sub network; D, carrying out power flow calculation on the alternating current sub network; E, carrying out power flow calculation on the direct current sub network; and F outputting the power flow calculation result. According to the technical scheme provided by the invention, the alternating current and direct current hybrid power distribution system is disassembled into the alternating current system and the direct current system; different power flow calculation methods are carried out on the alternating current system and the direct current system separately; and in addition, power exchange is only implemented on certain calculation nodes, so that the calculation speed is greatly enhanced.

A system and method to interconnect several conventional or alternative power generators, loads, and/or energy storage elements physically separated from each other in a DC distribution system. The method includes the steps of providing a common DC bus to interconnect all of the elements in the DC distributed system using power converters. A first group of one or more of the elements (main element) is used to automatically maintain the voltage of the DC link following a set a set point to provide for the load matching. The average DC link voltage (set point) maintained by the main element is intentionally changed in order to indicate all of the other elements connected to the DC bus how they need to modify their power generation or consumption.

The invention proposes a pilot protection method for a short-circuit fault of a DC power distribution system. The pilot protection method comprises the following steps of: 1, calculating DC current change rate di/dt according to acquired DC current information of a head end and a tail end of a DC circuit, judging whether the current change rate is beyond a set value, if yes, starting a fault distinguishing procedure to enter step 2, or protecting the fault distinguishing procedure from being started; and 2, determining the short-circuit fault of the DC circuit and tripping a DC circuit breaker of the DC circuit if the current jump value of the head end of the circuit is greater than the protected set value of the head end of the circuit and the current jump value of the tail end of the circuit is greater than the protected set value of the tail end of the circuit. In the protection method, the used protection principle is simple, and favorable rapidness and high reliability during the fault are achieved; and meanwhile, the protection method is prevented from being affected by a transition resistor and a system running mode, and a technical support is provided for safe and reliable running of the DC power distribution system.

The invention provides an alternating-current and direct-current power distribution network system load flow computing method based on droop control. The method includes the following steps that firstly, initialization computing of a sagging curve is carried out; secondly, direct-current power of a direct-current power distribution system is updated through the Newton algorithm; thirdly, according to the updated direct-current power, a middle node voltage equation of an alternating-current power distribution system is solved, and droop characteristics are led into the alternating-current power distribution system; fourthly, whether alternating-current power flow and direct-current power flow converge or not is judged, if no, the second step continues for iterative computation till the alternating-current power flow and the direct-current power flow converge at the same time, and meanwhile a result is output. The invention provides the power flow mixing computing method suitable for a multi-terminal interconnection alternating-current and direct-current power distribution system adopting droop control, the gauss algorithm is adopted in the alternating-current power distribution system, and the Newton algorithm is adopted in the direct-current power distribution system. Meanwhile, the advantage that the gauss algorithm is little in calculation quantity and the advantage that the Newton algorithm is good in convergence are both taken into consideration, the problem that power flow does not converge is avoided, and the practicality level of power flow computing is improved.

A method includes the steps of providing a common DC bus to interconnect power elements to a DC distribution system using power converters. A first group of one or more of the elements (main element) is used to execute the primary function by automatically maintaining the DC bus voltage following a set point. The DC bus voltage set point is intentionally changed with slow dynamics according to a secondary function executed by the main element such that the average DC bus voltage regulated by the main element changes. A local logic is used on each of the power elements connected to the DC bus but different from the main element to modify their power generation or consumption as a result of changes in the measured average DC bus voltage such that they contribute to the fulfillment of the secondary level of control.

The invention discloses a direct-current power distribution system of a fully-flexible structure. A voltage converter of the direct-current power distribution system is a solid-state transformer and comprises an alternating current/direct current solid-state transformer, a direct current/direct current solid-state transformer and a direct current/direct current/alternating-direct current solid-state transformer, an alternating current side of the alternating current/direct current solid-state transformer is connected with different alternating current power distribution lines or an alternating-current distributed-type power source while a direct current side of the same is connected with a direct current power distribution line, a low voltage side of the direct current/direct current solid-state transformer is connected with a direct-current distributed-type power source while a high voltage side of the same is connected with the direct current power distribution line, a high voltage direct current side of the direct current/direct current/alternating current solid-state transformer is connected with the direct current power distribution line while an alternating current side of the same is connected with an alternating current power consumption line to provide alternating current power, and a low voltage direct current side of the direct current/direct current/alternating current solid-state transformer is connected with a direct current power consumption line to provide direct current power. By the direct-current power distribution system, flexible conversion of alternating current and direct current for constructing the direct-current power distribution system is realized, convenience can be brought to connection-in of the distributed-type power source and stored energy in a direct-current manner, high quality alternating and direct current power is provided, and direct-current power distribution networks with various structures can be formed flexibly.

The invention discloses a flexible DC distribution line protection method based on transient current similarity, and belongs to the DC distribution system protection technical field; the method aims at the flexible DC distribution system, and derives a mathematics expression of a fault current after a DC line fails according to current change physics nature and direction characteristics at the DCline failing moment in the system; aiming at the conditions that a conventional protection cannot fast move after the DC line fails, the invention proposes the protection determination method that uses a cosine similarity; the method is simple, reliable, fast in power swing, can accurately determine DC line zone internal and external faults, thus selecting the fault line; the method is applied toDC line fault determination in a multi-terminal flexible DC distribution system; the method is not affected by line length, communication non-synchronization and transit resistance factors, thus improving the whole system operation reliability, and providing good selectivity and adaptability; the method is easy for promotion and application.