43results about How to "Limit fault current" patented technology

Provided in the invention is a flexible multi-state switch comprising a first isolation transformer (T1), a first controlled voltage source (D11), a direct-current bus voltage-stabilizing capacitor (C1), a second controlled voltage source (D22), a second isolation transformer (T2), and a central controller. A first feeder line (K11) is connected to the first controlled voltage source (D11) throughthe first isolation transformer (T1); a second feeder line (K22) and the second controlled voltage source (D22) ) are connected by the second isolation transformer (T2); and the first controlled voltage source (D11) is connected to the second controlled voltage source (D22) through the direct-current bus capacitor (C1). Various functions including bidirectional circulation of active power betweenfeeder lines, reactive compensation control, short-circuit current suppression, power flow optimization and power quality management and the like are realized by applying different control methods onthe first controlled voltage source (D11) and the second controlled voltage source (D22) of the flexible multi-state switch.

The invention discloses a cascaded converter-based multifunctional high-speed switch device which structurally comprises a main switch module, an auxiliary switch K1, an auxiliary switch K2 and an auxiliary switch K3; the main switch module is connected with a power source by the auxiliary switch K1 and is connected with a load by the auxiliary switch K3, and the main switch module is connected with the auxiliary switch K1 and the auxiliary switch K3 with each other in series and is connected with the auxiliary switch K2 in parallel with each other; and the main switch module comprises a cascaded H bridge converter and a wave filtering link, an output end of the cascaded H bridge converter is connected with the wave filtering link, and the cascaded H bridge converter comprises n H bridge converter cascaded units which are connected with one another in series. The cascaded converter-based multifunctional high-speed switch device is flexibly applicable to various connection modes between the power source and the load, has various functions of superspeed switching, voltage compensating, fault current limiting and the like, and is applicable to the middle and high voltage occasion due to a cascaded structure.

The invention, which relates to the technical field of energy systems, provides an energy router device applied to wind-light energy storage and a control method thereof. The device comprises a bidirectional rectifying unit, a resonant bidirectional DC-DC conversion unit, a photovoltaic Boost transform unit, a bidirectional DC-DC conversion unit, a soft switching single-phase full-bridge inverterunit, a three-phase PWM rectifying unit, a high-voltage direct-current bus, a low-voltage direct-current bus, a DSP controller, a voltage sensor and a current sensor. Meanwhile, on the basis of a hybrid energy storage coordinated control strategy of a stochastic robust optimization method, the device has seven kinds of working modes. In addition, the invention also provides a control method of anenergy router device applied to wind-light energy storage. According to the invention, on the basis of the multi-unit topological structure, the electric energy with various voltage levels can be provided and various load and energy storage device's needs are met; and the photovoltaic-fan complementary power generation is realized by the control method and the hardware structure.

The invention discloses a fault current-limiting control method and system for an MMC type flexible direct-current power grid, which belong to the field of power transmission and distribution of powersystems. By introducing a control variable of the modulation coefficient, the number of submodules actually inputted by a bridge arm unit of a converter is determined by the control signal outputtedby a pole controller and the modulation coefficient together, so that the bus voltage of the direct-current side outlet of the converter is positively correlated with the modulation coefficient. For aflexible direct-current power grid constructed by any type of modular multilevel converter, the number of submodules inputted by the bridge arm unit of the converter is obtained by multiplying the control signal outputted by the converter pole controller by the modulation coefficient. Under a fault condition, the modulation coefficient is reduced, the number of submodules inputted by the bridge arm unit is actively reduced by each converter, so that the DC voltage of the DC side outlet of the converter is reduced when a fault occurs, the fault current of the DC power grid is limited, the on-off capacity of the circuit breaker and the energy absorption of the parallel lightning arrester of the DC circuit breaker are reduced, and the cost is reduced.

The invention relates to power systems and automation, in particular to a system and a method for improving FRT (fault ride-though) capability of a DFIG-WT (doubly fed induction generator based wind turbine) on the basis of an SFCL (superconducting fault current limiter) and an SMES (superconducting magnetic energy storage). The system is characterized in the on the basis of the typical DFIG-WT, aresistor type SFCL is mounted on the stator side of the DFIG-WT, and the SMES is mounted on a direct current link of the DFIG-WT through a bidirectional DC / DC converter; the resistor type SFCL is used for limiting stator fault current of the DFIG-WT, improving generator terminal voltage sag of the DFIG-WT and absorbing partial surplus active power in the DFIG-WT; the SMES is used for stabilizingunbalanced power and electromagnetic torque oscillation. According to an FRT method for the DFIG-WT on the basis of the SFCL and the SMES, fault current can be limited under symmetrical faults and asymmetrical faults, voltage change is inhibited, and unbalanced power and electromagnetic torque oscillation are stabilized. Efficient FRT support can be provided for the DFIG-WT during FRT, and transient performance of the DFIG-WT is improved.

The invention discloses a novel combined DC circuit breaker topology, which adopts only one main breaker switch, one malfunctioning auxiliary switch, one transfer switch TS0 connected in series with the main breaker switch, two groups of diodes in different directions, and a transfer switch TS1 corresponding to m lines on each DC bus bar, wherein, the main breaker switch TS0 is connected with themain breaker switch TS0, and the main breaker switch TS1 is connected with the main breaker switch TS0-TSm. The transfer switch TS0 is connected in parallel with the failed auxiliary switch in serieswith the main disconnect switch, one end of the main disconnect switch is connected with the DC bus bar, the other end is connected with the diode group in the direction of the inflow line through thetransfer switch TS0, and is also connected with the diode group in the direction of the outflow line through the failed auxiliary switch. The transfer switch TS1-TSm is respectively connected to thebus bar and the corresponding line 1-Line m. When the system is in normal operation, the voltage on both ends of the switches of each part of the novel combined DC circuit breaker is zero, which can effectively reduce the breakdown probability of the device, improve the operation reliability of the system as a whole, adopt fewer main devices, and have better economy.

The invention discloses a saturated bridge type short circuit fault current limiter, which comprises a saturated reactor and a rectifier bridge. The connecting point of a first diode (D1) and a second diode (D2) of the rectifier bridge (Br) is a first alternating current end (A); the connecting point of a third diode (D3) and a fourth diode (D4) of the rectifier bridge (Br) is a second alternating current end (B); the connecting point of the first diode (D1) and the third diode (D3) of the rectifier bridge (Br) is a first direct current end (M); the connecting point of the second diode (D2) and the fourth diode (D4) of the rectifier bridge (Br) is a second direct current end (N); the saturated reactor (L) is connected between the first direct current end (M) and the second direct current end (N); one end of an alternating current power supply (Uac) is connected to the first alternating current end (A); the other end of the alternating current power supply (Uac) is grounded; one end of a circuit breaker (SW) is connected to the second alternating current end (B); the other end of the circuit breaker (SW) is connected with a load (RL) in series and is then grounded. The saturated reactor is realized by a permanent magnet and a direct current coil.

The invention discloses a multi-terminal flexible DC power grid fault current limiting method and device. Blocking of a converter station can be avoided so as to ensure high power supply reliability.The method comprises the following steps: constructing a topology structure of a current limiting device; determining the current of the current limiting device in the discharge stage of the energy storage capacitor and the input stage of the current limiting resistor; setting the input criterion of the current limiting device; selecting the key parameters of the current limiting device; and controlling on / off of the thyristor in the current limiting device when the DC side of the flexible DC system fails and serially connecting the current limiting resistor in the fault loop to realize faultcurrent limiting.

The invention relates to a hybrid short-circuit fault current limiter and a current limiting method. The hybrid short-circuit fault current limiter comprises a current transfer branch and a fault current limiting branch, wherein the current transfer branch comprises a rapid mechanical switch and a power electronic switch in series. In a steady state, a current passes through the current transfer branch, and the loss during normal running is reduced; when a fault occurs, a switch on the transfer branch acts, and the current is transferred to the fault current limiting branch; the fault currentlimiting branch comprises a dual-split reactor and a switch, and a first winding of the dual-split reactor is connected in series with the switch and is connected in parallel with a second winding; the switch is switched on in the steady state, and the fault current limiting branch shows low impedance; and the switch is switched off when the fault occurs, and the fault current limiting branch shows high impedance. By matching of the current transfer branch and the fault current limiting branch, the loss of the current limiter during normal running is reduced, meanwhile, fault current limitingis achieved by the dual-split reactor, and running economy and reliability of the current limiter are improved.

The related discharge-form current limiter for short fault is formed by paralleling an auxiliary inductance and a discharge tube on current device. The production can not only automatic limit fault current peak, but also limits the rise rate and stable value at any time without any control circuit. This invention reduces cost and improves power network reliability and security.

The invention discloses a comprehensive protection method and device of a direct current collection cable, and relates to the technical field of fault protection of a direct current collection grid-connected system. The method can inhibit the fault current and accurately position the direct current cable fault position. The method mainly comprises the steps that a direct current capacitor discharging equivalent circuit of the starting end or terminal end of the direct current cable is built, wherein the equivalent circuit comprises series connection current limiting reactors used by the method; according to the capacitor discharging equivalent circuit and protection constraint conditions, the reactance parameter values of the current limiting reactors are calculated; the current limiting reactors with the reactance parameter values are connected in series in the direct current cable; the voltage values on the current limiting reactors connected in series in the direct current cable areobtained; according to the voltage values of the current limiting reactors, the fault types of the direct current cable are judged, wherein the fault types include a positive electrode fault, a negative electrode fault and an interelectrode fault; according to the fault types, the position of fault points is calculated and positioned. The method and the device are mainly applied to fault protection and fault positioning of the direct current cable in new energy source direct current collection networks and other direct current power transmission and power distribution networks.

The invention relates to the technical field of circuit fault current limiting, and specifically relates to a short-circuit fault current-limiting transformer. The current-limiting transformer comprises a transformer and short-circuit protection circuits. The secondary coil of the transformer is composed of three identical secondary coils. A low-voltage tap is led out from each of the three secondary coils. One short-circuit protection circuit is connected between each low-voltage tap and the high-voltage end of the corresponding coil. Each short-circuit protection circuit is a current limiting loop in which one low-voltage tap is sequentially connected in series with an auxiliary reactor, a short-circuit protection switch and a capacitor and then connected with the high-voltage end of the corresponding secondary coil, wherein the capacitor is connected in parallel with a power supply switch, and the common joint of the power supply switch and the short-circuit protection switch is connected to a power supply circuit. At the moment when a line fails, a large impedance is added between the power supply and the fault point, and thus, the fault current is limited.

The invention discloses a cascaded converter-based multifunctional high-speed switch device which structurally comprises a main switch module, an auxiliary switch K1, an auxiliary switch K2 and an auxiliary switch K3; the main switch module is connected with a power source by the auxiliary switch K1 and is connected with a load by the auxiliary switch K3, and the main switch module is connected with the auxiliary switch K1 and the auxiliary switch K3 with each other in series and is connected with the auxiliary switch K2 in parallel with each other; and the main switch module comprises a cascaded H bridge converter and a wave filtering link, an output end of the cascaded H bridge converter is connected with the wave filtering link, and the cascaded H bridge converter comprises n H bridge converter cascaded units which are connected with one another in series. The cascaded converter-based multifunctional high-speed switch device is flexibly applicable to various connection modes between the power source and the load, has various functions of superspeed switching, voltage compensating, fault current limiting and the like, and is applicable to the middle and high voltage occasion due to a cascaded structure.

The invention relates to the technical field of direct-current converters, particularly provides a high-power high-transformation-ratio high-voltage direct-current converter for a space and a photovoltaic power generation system, and aims to solve a problem of how to transmit super-power electric energy output by a space solar power station to a high-voltage direct-current bus and ensure stable operation of the direct-current bus. The high-voltage direct-current converter comprises a plurality of direct-current conversion modules, and each direct-current conversion module comprises one or moredirect-current conversion sub-modules which are connected in parallel. A direct-current input side of each direct-current conversion module forms a plurality of direct-current input side ports of theconverter, and direct-current output sides of the direct-current conversion modules are sequentially connected through redundant switches to form direct-current output side ports of the converter sothat output voltages of the direct-current conversion modules is boosted in series, and transmission requirements of microwave transmitters connected later are met. When each direct-current conversionmodule breaks down, the corresponding redundant switch can be switched on to bypass the direct-current conversion module so that normal transmission of each microwave transmitter is not affected, andnormal operation of the system is guaranteed.

The invention discloses a flexible direct-current short-circuit fault protection method based on a thyristor chain and superconducting current limiters. A converter used in a flexible direct-current power transmission system is a modularized multi-level converter cascaded based on half-bridge sub-modules and is of an A-B-C three-phase structure, and each phase comprises an upper bridge arm and a lower bridge arm; each bridge arm consists of a plurality of half-bridge sub-modules and a bridge arm inductor; an alternating current side output port of the modular multilevel converter is connected in parallel with the thyristor chain; the three-phase lines of the AC side of the modular multilevel converter are each connected in series with a superconducting current limiter; the upper ends of the three-phase upper bridge arms of the modular multilevel converter are connected to a direct current side through a first mechanical switch after being short-circuited, and the lower ends of the three-phase lower bridge arms are connected to the direct current side through a second mechanical switch after being short-circuited. According to the protection method, alternating-current and direct-current side current isolation under a fault condition is achieved by turning on the thyristor chain, the direct-current side fault current is reduced to zero, the alternating-current side fault current is limited through the superconducting current limiters, and therefore direct-current short-circuit fault protection of the flexible direct-current power transmission system is achieved.

The invention relates to a mixed excitation type economical three-phase magnetic saturation fault current limiter comprising a magnetic core, a coil winding, three current limiting inductors and a direct current excitation power source, wherein the magnetic core comprises two pillars with an air gap therebetween, and left A, B and C phase side pillars and right A, B and C phase side pillars positioned on two sides of the central pillars; and the coil winding comprises a first coil and a second coil wound on a left A pillar, a third coil and a fourth coil wound on a left B pillar, a fifth coiland a sixth coil wound on a left C pillar, a seventh coil and an eighth coil wound on a right A pillar, a ninth coil and a tenth coil wound on a left B pillar, and an eleventh coil and a twelfth coilwound on a left C pillar. According to the mixed excitation type economical three-phase magnetic saturation fault current limiter, the three phase current limiter is integrated, the good limiting effect is achieved for a short-circuit current with various fault types, and the magnetic material and installation area are greatly saved. Furthermore, the loss in the iron core is also greatly reduced.

The invention belongs to the technical field of wind power integration, and relates to a parameter optimization method for integrating a wind power plant of a superconducting magnetic energy storage coil into VSC-HVDC. The problem that the effect of the SMES coil is reduced due to the fact that the initial inductance LSMES, the initial current ISMES0 and four PI control parameters (KPi and KIi, i= 1, 2) of the SMES magnetic energy storage coil are not optimized is solved. The method comprises the following steps: taking minimization of a direct current power accumulation error, minimization of a direct current voltage accumulation deviation and minimization of SMES coil initial energy as target functions, enabling a system to show a minimum direct current power fluctuation situation, configuring different weights, and determining an optimal value of a superconducting magnetic energy storage coil parameter according to a particle swarm algorithm. By utilizing the SMES-FCL, DC power fluctuation caused by intermittent wind power generation can be reduced, and the fault current of a DC line is limited.

This application provides a method for determining parameters of DC power grid components. The DC power grid includes at least two converter stations and at least one DC line between the converter stations. The method includes: determining the component parameters of the power grid to be determined; based on the topology of the power grid and the Component parameters determine the state matrix; based on the state matrix and the DC line fault current time domain expression, determine the relationship between the DC line fault current changing with time with one component parameter of the power grid as a variable; based on the DC line fault current The suppression requirements of fault current on the line determine the range of component parameters of the power grid.

The invention discloses a flexible DC short-circuit fault protection method based on a thyristor chain and a superconducting current limiter. The converter used in the flexible DC power transmission system is a modular multi-level converter based on cascaded half-bridge sub-modules: ABC three-phase structure, each phase includes an upper bridge arm and a lower bridge arm, each bridge arm is composed of several half-bridge sub-modules and a bridge arm inductor; the output port of the modular multi-level converter AC side is connected in parallel with a thyristor A superconducting current limiter is connected in series with each of the three-phase lines on the AC side of the modular multilevel converter; the upper ends of the three-phase upper arms of the modular multilevel converter are short-circuited and connected to the DC side through the first mechanical switch , the lower end of the three-phase lower bridge arm is short-circuited and then connected to the DC side through the second mechanical switch. The protection method realizes the current isolation of the AC and DC sides under fault conditions by opening the thyristor chain and reduces the fault current of the DC side to zero, and limits the fault current of the AC side through the superconducting current limiter, thereby realizing the DC short-circuit fault protection of the flexible DC transmission system.

The invention relates to an AC-DC hybrid distribution network based on flexible multi-state switches, the distribution network includes N AC power supply networks, where N is an integer greater than or equal to 2; each AC power supply network includes at least one pivot node , at least one terminal node and at least two branch nodes, the power distribution network further includes at least N flexible multi-state switches, the AC terminals of the flexible multi-state switches are connected to the AC power grid, which can realize AC and DC voltage conversion, and the DC port leads out; The invention also relates to a control test method including the above distribution network, which can realize active power balance, stabilize the system frequency and voltage, and improve the reliability of the distribution network.

The disclosed current limiter for short circuit fault is constituted by adding a cascaded capacitor to positive / negative DC ends of rectification bridge of existed current limiter for short circuit fault respectively; two capacitors and two current limiting inductances are connected in shape of number '8'. The disclosed current limiter can restrict peak value of fault current, restrict ascending velocity of fault current at any time, improves distortion of stable current generated by current limiter. Under condition of canceling bias voltage, size and cost can be reduced. Based on connection method of existed current limiter for short circuit fault, the invention can constitute multiple circuit structures. Advantages are: simple structure, high current limiting capacity, raised quality, stability, safety and reliability of power network.

The invention discloses a comprehensive protection method and device of a direct current collection cable, and relates to the technical field of fault protection of a direct current collection grid-connected system. The method can inhibit the fault current and accurately position the direct current cable fault position. The method mainly comprises the steps that a direct current capacitor discharging equivalent circuit of the starting end or terminal end of the direct current cable is built, wherein the equivalent circuit comprises series connection current limiting reactors used by the method; according to the capacitor discharging equivalent circuit and protection constraint conditions, the reactance parameter values of the current limiting reactors are calculated; the current limiting reactors with the reactance parameter values are connected in series in the direct current cable; the voltage values on the current limiting reactors connected in series in the direct current cable areobtained; according to the voltage values of the current limiting reactors, the fault types of the direct current cable are judged, wherein the fault types include a positive electrode fault, a negative electrode fault and an interelectrode fault; according to the fault types, the position of fault points is calculated and positioned. The method and the device are mainly applied to fault protection and fault positioning of the direct current cable in new energy source direct current collection networks and other direct current power transmission and power distribution networks.

The present application provides a flexible multi-state switch and a control method: the flexible multi-state switch includes two chain converters; the chain converter includes three multi-level commutation chains, and three multi-level commutation chains The head and tail of the chain are connected to each other to form an angle connection, and the ends are drawn out and connected to the AC power grid; the multi-level commutation chain includes N four-port power modules and at least one damping unit, and N is an integer greater than or equal to 1; so The four-port power module is composed of a DC capacitor, a power component, a first switch unit and a second switch unit; the DC capacitor is connected to the power component, and the power component includes four groups of power semiconductor devices to form two bridge arms, that is, a full bridge connection In the form, the midpoint of the two bridge arms is defined as the AC end of the four-port power module; one end of the first switch unit is connected to the positive or negative electrode of the DC capacitor, and the other end is connected to one end of the second switch unit. The first switch unit is connected to The connection point of the second switch unit is defined as the first DC port; the other end of the second switch unit is defined as the second DC port.

The invention relates to a mixed excitation type economical three-phase magnetic saturation fault current limiter comprising a magnetic core, a coil winding, three current limiting inductors and a direct current excitation power source, wherein the magnetic core comprises two pillars with an air gap therebetween, and left A, B and C phase side pillars and right A, B and C phase side pillars positioned on two sides of the central pillars; and the coil winding comprises a first coil and a second coil wound on a left A pillar, a third coil and a fourth coil wound on a left B pillar, a fifth coiland a sixth coil wound on a left C pillar, a seventh coil and an eighth coil wound on a right A pillar, a ninth coil and a tenth coil wound on a left B pillar, and an eleventh coil and a twelfth coilwound on a left C pillar. According to the mixed excitation type economical three-phase magnetic saturation fault current limiter, the three phase current limiter is integrated, the good limiting effect is achieved for a short-circuit current with various fault types, and the magnetic material and installation area are greatly saved. Furthermore, the loss in the iron core is also greatly reduced.

The invention discloses a novel combined DC circuit breaker topology, which adopts only one main breaker switch, one malfunctioning auxiliary switch, one transfer switch TS0 connected in series with the main breaker switch, two groups of diodes in different directions, and a transfer switch TS1 corresponding to m lines on each DC bus bar, wherein, the main breaker switch TS0 is connected with themain breaker switch TS0, and the main breaker switch TS1 is connected with the main breaker switch TS0-TSm. The transfer switch TS0 is connected in parallel with the failed auxiliary switch in serieswith the main disconnect switch, one end of the main disconnect switch is connected with the DC bus bar, the other end is connected with the diode group in the direction of the inflow line through thetransfer switch TS0, and is also connected with the diode group in the direction of the outflow line through the failed auxiliary switch. The transfer switch TS1-TSm is respectively connected to thebus bar and the corresponding line 1-Line m. When the system is in normal operation, the voltage on both ends of the switches of each part of the novel combined DC circuit breaker is zero, which can effectively reduce the breakdown probability of the device, improve the operation reliability of the system as a whole, adopt fewer main devices, and have better economy.

A flexible switching station interconnection structure with comprehensive distribution of multiple electric energies. The interconnection structure of the flexible switch station is composed of several flexible switch stations. The input end of each flexible switch station is connected to the high-voltage AC bus, and the output of the flexible switch station is respectively connected to the low-voltage AC bus and the low-voltage DC bus; the end of the low-voltage AC bus It is connected through a flexible multi-state switch, and the ends of the low-voltage DC bus are connected through a DC-DC converter; both the low-voltage AC bus and the low-voltage DC bus are connected with loads, energy storage components and distributed power sources. The invention interconnects the flexible switching station with functions of AC and DC voltage conversion and power distribution through flexible multi-state switches and DC-DC converters. Compared with traditional substations, the flexible switch station interconnection system has the advantages of active power flow control, flexible topology construction, distributed energy consumption, multi-voltage level interconnection, and unified distribution of AC and DC, which improves the reliability and diversity of power supply.

The invention discloses a short-circuit fault current limiter and relates to a short-circuit fault current limiter for a transmission and distribution power grid. The short-circuit fault current limiter is composed of a first electric reactor, a second electric reactor, a double-splitting electric reactor, a capacitor and a switch, wherein a first winding of the double-splitting electric reactor is connected with a second winding in parallel after being connected with the switch in series and then is connected with the capacitor in parallel, a parallel circuit is connected with the second electric reactor in series, and the whole series-parallel circuit and the first electric reactor are connected in parallel to form the short-circuit fault current limiter. According to the short-circuit fault current limiter, through the cooperation between the double-splitting electric reactor and the switch, impedance change and rapid short circuit of the capacitor are achieved during current limiting, the electric reactors are put into use fast, overcurrent impact and overvoltage impact when the double-splitting electric reactor cooperates with the switch are relieved through the parallel connection of the first electric reactor, and the operating reliability and the current limiting capacity of the limiter are improved.

The invention provides an energy storage optimization control method for an energy router device applied to wind and solar energy storage, and relates to the technical field of energy systems. The device includes a bidirectional rectifier unit, a resonant bidirectional DC-DC conversion unit, a photovoltaic Boost conversion unit, a bidirectional DC-DC conversion unit, a soft-switching single-phase full-bridge inverter unit, a three-phase PWM rectifier unit, a high-voltage DC bus, a low-voltage DC bus, DSP controller, voltage sensor and current sensor; at the same time, the device adopts a hybrid energy storage coordinated control strategy of a stochastic robust optimization method, including 7 working modes; the invention also provides an energy router device applied to wind and solar energy storage A control method for energy storage optimization. The energy router device and control method applied to wind and solar energy storage provided by the present invention, the multi-unit topology adopted by the device determines that it can provide electric energy of various voltage levels, meet the needs of various loads and energy storage equipment, and can control The method and hardware structure realize the effect of photovoltaic and wind turbine complementary power generation.

The invention provides a flexible multi-state switch and a control method. The flexible multi-state switch comprises two chain type current converters. The chain type current converter comprises three multi-level current conversion chains, the three multi-level current conversion chains are mutually connected end to end to form an angle type connection method, and the end parts are led out to be connected with an alternating current power grid; the multi-level current conversion chain comprises N four-port power modules and at least one damping unit, and N is an integer greater than or equal to 1; the four-port power module is composed of a direct current capacitor, a power assembly, a first switch unit and a second switch unit. The direct-current capacitor is connected with the power assembly, the power assembly comprises four groups of power semiconductor devices which form two bridge arms in a full-bridge connection mode, and midpoints of the two bridge arms are led out to be defined as alternating-current ends of the four-port power module; one end of the first switch unit is connected with a positive electrode or a negative electrode of the direct current capacitor, the other end is connected with one end of the second switch unit, and a connection point of the first switch unit and the second switch unit is led out and defined as a first direct current port; and the other end of the second switch unit is defined as a second direct current port.