560 results about "Dc circuit" patented technology

The invention discloses a charging and discharging control method and device for an elevator energy storage system, a medium and a product, and relates to the field of data processing. The method comprises the steps that real-time operation data such as the position and the load capacity of an elevator car are obtained, and the instantaneous power generation power and the power change rate of a traction machine are determined accordingly; determining a power change predicted value in a future preset time period based on the parameters, and obtaining the total amount of power generation energy required to be stored by the energy storage system through zero setting of a positive value, integral operation and efficiency compensation; according to the power change rate, the state of the energy storage unit and the power grid electricity price time period, the charging and discharging priorities fed back by the super capacitor, the lithium battery and the power grid are determined; controlling the bidirectional DC / DC circuit to switch charging and discharging modes according to the priority, and adjusting the PWM duty ratio of the brake resistor; and based on the charging and discharging mode and the duty ratio, charging and discharging control over the elevator energy storage system is achieved. According to the method, the problem of inaccurate real-time matching of the dynamic load and the energy fluctuation of the current elevator energy storage system can be relieved.

The invention relates to the technical field of power electronic devices, in particular to a low-voltage direct-current circuit breaker, a fault protection method and a related device.The low-voltage direct-current circuit breaker comprises a through-flow branch, a transfer branch and an energy consumption branch which are connected in sequence; the through-current branch comprises an isolating switch and an MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor) commutation switch which are connected in series; the transfer branch comprises a first power electronic switch group and a buffer branch which are connected in parallel; the energy consumption branch comprises a first metal oxide MOV, a second metal oxide MOV and a second power electronic switch group; the first metal oxide MOV is connected in parallel with the second power electronic switch group; and the second metal oxide MOV is respectively connected with the first metal oxide MOV and the second power electronic switch group. The technical problems that an existing hybrid direct current circuit breaker is not suitable for a low-voltage direct current system and the loss is high in the turn-off process are solved.

The invention discloses a two-stage multi-mode bidirectional inverter circuit, which comprises a direct-current power supply DC, an alternating-current power supply AC, a DC / DC circuit, a direct-current voltage-dividing capacitor Cb1, a direct-current voltage-dividing capacitor Cb2, a DC / AC circuit and a controller, and is characterized in that a negative electrode of a second port of the DC / DC circuit is connected with a negative electrode of the direct-current voltage-dividing capacitor Cb1 and a negative electrode of a direct-current port of the DC / AC circuit; a middle point of a second port of the DC / DC circuit is connected with a negative electrode of a direct-current voltage-dividing capacitor Cb1 and a positive electrode of a direct-current voltage-dividing capacitor Cb2, and is connected to an alternating-current neutral line N; the AC port of the DC / AC circuit is connected with an AC live wire L1 and an AC live wire L2. The controller stably outputs voltage or current by controlling the DC / DC circuit and the DC / AC circuit, and bidirectional electric energy conversion is achieved. According to the invention, direct-current capacitance and additional circuits do not need to be increased, the size of the device is reduced, the system cost is reduced, the conversion efficiency is improved, and the device can be widely applied to new energy power generation and energy storage and other industrial and civil bidirectional power conversion systems so as to meet the global power supply and consumption requirements.

The invention discloses a parameter control method for a bidirectional power conversion circuit with alternating current and direct current electric energy interchange, which relates to the technical field of circuit parameter control, and comprises the following steps: respectively carrying out electric energy conversion on an alternating current side and electric energy adjustment on a direct current side by adopting a topological structure in which a three-phase voltage source type converter and a direct current circuit bidirectional converter are connected in series; collecting parameters of the AC-DC bidirectional power converter in real time; switching among three working modes of rectification, inversion and shutdown is realized; the DC bus voltage is kept at a rated value when supply and demand in the DC subnet are balanced, and bidirectional flow of power is realized when supply and demand are unbalanced; performing coordinate transformation on the acquired voltage and current; and separating positive and negative sequence components of the voltage by using a second-order generalized integrator algorithm. By adopting a specific topological structure and utilizing the droop characteristic to realize working mode switching, the adaptability and the control precision of the bidirectional power converter in the alternating current and direct current hybrid micro-grid are improved.

The utility model provides an electric energy meter calibrating device comprising a calibrating box body, the calibrating box body comprises a first plate and a second plate which are arranged at intervals along a first direction, and at least one of the first plate and the second plate is provided with at least one first air port; the second air opening is formed in the plate body for connecting the first plate and the second plate; the supporting partition plate is arranged in the verification box body in the first direction, and the space in the verification box body is divided into a first cavity and a second cavity by the supporting partition plate; the plurality of direct-current circuit boards are connected with the supporting partition plate, the direct-current circuit boards are arranged in the first cavity, and at least one direct-current circuit board is provided with a first heating piece; the at least one first fan is arranged on the supporting partition plate, and the first fan and the first heating piece are oppositely arranged; and the plurality of alternating-current circuit boards are connected with the supporting partition plate and are arranged in the second cavity. According to the technical scheme, the direct current circuit board and the alternating current circuit board are arranged in a layered mode, the heat dissipation capacity of the device is remarkably improved, and the temperature of the whole system is kept stable.

The invention discloses a fault current analysis method and system for a multi-terminal flexible DC circuit, and the method comprises the steps: analyzing fault current data when the DC side of a modular multilevel converter is short-circuited, and obtaining time sequence segmentation rule data; performing equivalent processing on the modular multilevel converter based on the segmentation rule data to obtain an equivalent circuit model comprising an RLC series circuit and a time-varying current source; constructing a second-order differential equation for describing the fault current according to the equivalent circuit model, and solving the second-order differential equation to obtain a fault current expression containing dynamic alternating current feed-in; constructing a fault equivalent network of the multi-terminal flexible DC circuit; and constructing a state-space equation of the fault equivalent network based on a branch current method and the fault current expression, and solving the state-space equation to obtain fault current data of the multi-terminal flexible DC circuit. According to the method, the accuracy of fault analysis is improved.

The invention relates to a ripple suppression PI loop control method, a storage medium and a device, and the method comprises the steps: extracting a frequency doubling component in an inversion power flow based on the filtering and Park transformation of a secondary second-order generalized integrator, determining the reverse compensation amount at each moment based on the frequency doubling component and a battery connected with a DC circuit, and carrying out the control of the ripple suppression PI loop. And finally, based on the sum of the reverse compensation amount at each moment and an original reference current value output by a voltage outer ring on each bridge arm of the DC circuit, determining a current reference instantaneous value after reverse compensation of a current inner ring input to each bridge arm at each moment. According to the method, a pure frequency doubling component with very high dynamic performance and related to ripple information is obtained, then according to the extracted frequency doubling component and battery parameters, the reverse compensation amount used for suppressing ripple in loop control is obtained, and then the reverse compensation amount is accumulated to a voltage outer loop, so that the ripple information is suppressed. Therefore, ripple suppression with good dynamic performance and good suppression effect in loop control is realized.

A charging apparatus is applied to a new energy vehicle. The new energy vehicle includes a first battery and a second battery. The first battery provides driving power for the new energy vehicle, and the second battery supplies power to a vehicle-mounted load device. The apparatus includes a charging unit and a general-purpose unit. The charging unit includes a DC-DC circuit and a BMS. The general-purpose unit includes a control module, a communication module, and an auxiliary power supply module. The auxiliary power supply module supplies power to the charging unit and the control module. The control module is configured to control the charging unit to provide electric energy of the first battery to the second battery. According to the apparatus provided in this application, a volume and a weight of the charging apparatus can be reduced, a service life of a battery can be prolonged.

This invention relates to the field of energy storage technology and discloses a synchronous testing platform for multiple energy storage converters and its control method. The testing platform of this invention includes: an incoming line switch, a pre-charge circuit, a transformer, an auxiliary power supply switch, an AC circuit breaker, a DC circuit breaker, and a unit controller. The power grid is connected to the high-voltage side of the transformer sequentially through the incoming line switch and the pre-charge circuit. One side of the AC circuit breaker is connected to the windings on the low-voltage side of the transformer, and the other side is connected to the AC side of the energy storage converter. The DC side of the first group of energy storage converters is connected to the DC side of the second group of energy storage converters through DC circuit breakers. The first group of energy storage converters is connected to the auxiliary power supply. In this invention, after the first group of PCS (Power Storage Converters) is pre-charged, the pre-charge circuit is bypassed. Then, the first group of PCS is unlocked and controlled in DC voltage mode, and the second group of PCS is started sequentially, thereby achieving synchronous charging and discharging testing of 2N PCS, greatly improving the charging and discharging testing efficiency of the energy storage converter.

The invention belongs to the technical field of direct-current power transmission, and discloses an IGCT assembly structure for a converter valve, and the structure comprises a valve assembly and a press-fitting part which is used for carrying out the press-fitting and fixing of the valve assembly. The valve assembly comprises n IGCT devices, n + 1 water-cooled radiators, 2n static voltage-sharing resistors, n lightning arresters and 4n damping resistors. The n IGCT devices and the (n + 1) water-cooled radiators are arranged in a stacked manner; the 2n static voltage-sharing resistors and the 4n damping resistors are arranged on the water-cooling radiator; and each lightning arrester is connected with the water-cooled radiator through the first connecting busbar. According to the valve assembly, the IGCT device is used, the problem of commutation failure of the direct-current power transmission technology is solved, meanwhile, the IGCT device is a full-control device, control over switching-on and switching-off is achieved, when a direct-current system breaks down, the valve assembly can also be used as a direct-current circuit breaker, and controllability is high; devices of the valve assembly are distributed on the water-cooling radiator, and the heat dissipation function of the water-cooling radiator is fully utilized.

The invention relates to the technical field of vehicle charging sockets, in particular to a charging socket signal switching mode. According to the charging socket signal switching mode, a socket shell is included, an inner cavity of the socket shell is divided into a DC cavity and an AC cavity, a DC circuit board and an AC circuit board are connected with SMD thermistors respectively so as to measure the temperature of DC and AC power terminals, the DC circuit board and the AC circuit board are connected with multi-PIN connectors respectively, and multi-PIN contact pins are integrated in the socket shell. The two ends of the multi-PIN pin extend into the DC cavity and the AC cavity respectively and are connected with the multi-PIN connector of the DC circuit board and the multi-PIN connector of the AC circuit board in an inserted mode, so that a DC power terminal temperature signal is transmitted to the AC circuit board through the multi-PIN connector of the DC circuit board, the multi-PIN pin and the multi-PIN connector of the AC circuit board in sequence and led out through the low-voltage connector of the AC circuit board. Through a signal switching mode of integrating the PINs in the socket shell, the split type design of the AC cavity and the DC cavity can be realized, so that the assembling performance and the sealing reliability of the product are improved.

The intrinsically safe power supply comprises a safety isolation transformer, a fuse, a rectification filtering and reverse connection prevention circuit, a lightning protection circuit, a surge and overvoltage protection circuit, a DC / DC conversion circuit and a two-stage overcurrent and overvoltage protection circuit. An R-type safety isolation transformer is matched with a primary side fuse and a secondary side fuse to provide a reliable SELV power supply, a DC / DC circuit is formed based on an LM2676-ADJ chip, a two-stage over-current and over-voltage rapid turn-off protection circuit is formed through a surge protection chip ADM1270, and the nonlinear rectangular power supply output characteristic is provided. The two-stage TVS is arranged at the input end of the DC / DC circuit and the input end of the ADM1270 chip and matched with the fuse for protection, the fuse is fused under the condition that the input voltage is abnormal or the DC / DC fails, the overvoltage protection effect is achieved, and the safety of the chip and the reliability of the power supply are ensured.

The invention provides a vehicle-mounted charger control method and system and a vehicle controller, and is used for providing sweep frequency current required by electrochemical impedance spectroscopy detection for a power battery under the condition that a vehicle-mounted charger is not connected with an alternating current power grid. Acquiring target sweep frequency current information; and an isolation DC / DC circuit is driven according to the target sweep frequency current information, so that the sweep frequency current can flow bidirectionally between the intermediate bus capacitor and the power battery. According to the invention, the starting scene of the EIS detection function can be effectively expanded, and the EIS detection function is allowed to be started in the scene of not inserting a charging gun and a discharging gun or not connecting an in-vehicle alternating current load.

The invention provides a method and system for detecting the health state of a storage battery for a transformer substation direct current system, and the method comprises the steps: obtaining first state data which comprises an access switch state of a battery pack, a closed-loop switch state between direct current buses, a voltage increment state of the battery pack, and a current increment state of the battery pack; determining the operation condition of the storage battery according to the first state data; according to the operation condition, collecting operation data including the boost rate, the charge increment, the charging duration and the discharging duration of the storage battery, calculating a health characteristic value HF of the storage battery under the corresponding condition according to the operation data, and obtaining second state data including the voltage V, the internal resistance R, the temperature T and the health characteristic value HF of the storage battery, and the SOH value diagnosis model generates an SOH value for determining the health state of the storage battery according to the second state data. The health state of the storage battery can be judged from multiple angles by combining the operation condition of the storage battery in the direct-current circuit, and the detection accuracy of the health state of the storage battery is improved.

A power stage circuit with multiple bidirectional AC to DC circuits for bidirectional charging is modified to connect the power stage converters in series for DC to AC applications. The power stage circuit can covert a DC input from a DC power source of a vehicle to an AC output for a power outlet of the vehicle. The power stage circuit uses two lines with a 120 VAC at the power outlet. Using a common neutral line, the AC to DC circuits are connected together to form a split phase power output, and the 120 VAC lines are 180 degrees out of phase to create a 240 VAC source at the power outlet.

The embodiment of the invention discloses a primary and secondary fusion pole-mounted switch self-adaptive energy supply system and method, and relates to the technical field of intelligent power distribution network equipment. The system comprises a capacitor electricity taking module located on the primary side of the primary and secondary fusion pole-mounted switch, and a super capacitor, a power management module, a storage battery, an energy management control unit and a DC-DC circuit which are located on the secondary side of the primary and secondary fusion pole-mounted switch. Dynamic coordination of two energy storage elements, namely a super capacitor and a storage battery, in a steady-state low-power-consumption monitoring and transient-state high-power driving scene is realized, energy distribution optimization, closed-loop charging guarantee and abnormal fault-tolerant design are combined, and the problems of high steady-state power consumption and insufficient transient-state driving capability existing in a traditional primary and secondary fusion pole-mounted switch power supply scheme are solved.

This invention relates to the field of DC circuit breakers, and discloses a thyristor-type DC circuit breaker and its control method. The DC circuit breaker structure is a thyristor T... m1 Anode-connected thyristor T m2 The cathode forms the A terminal of the circuit breaker, T m1 Cathode connection T m2 The anode of the thyristor forms the B terminal of the circuit breaker; the thyristor T p1 anode, thyristor T p2 The cathode is connected to terminal A; T p1 Cathode connection T p2 After anode, it passes through resistor R in sequence. g Switch RCB g Grounding; T p1 Cathode connection T p2 After the anode, it also passes through inductor L p Capacitor C is connected to terminal B; one end of the surge arrester MOV is connected to terminal T. p1 The cathode is connected to the first terminal, and the other end is connected to the B terminal. This invention has a simple structure and significant cost advantages; under normal operating conditions, only a single thyristor is conducting, resulting in extremely low losses and extremely high circuit breaker efficiency. Combined with control methods, it can actively and reliably connect or disconnect bidirectional operating current or bidirectional fault current; it can also achieve fast reclosing functionality.

The application discloses a fault current analysis method and system of a multi-terminal flexible DC circuit, wherein the method comprises the following steps: analyzing fault current data when a modular multilevel converter DC side is short-circuited to obtain time sequence segmentation rule data; performing equivalent processing on the modular multilevel converter based on the segmentation rule data to obtain an equivalent circuit model comprising an RLC series circuit and a time-varying current source; constructing a second-order differential equation describing the fault current according to the equivalent circuit model, and solving the second-order differential equation to obtain a fault current expression containing dynamic AC feed-in; constructing a fault equivalent network of the multi-terminal flexible DC circuit; constructing a state space equation of the fault equivalent network based on a branch current method and the fault current expression, and solving the state space equation to obtain fault current data of the multi-terminal flexible DC circuit. The method improves the accuracy of fault analysis.

The present application discloses a variable frequency power supply device with dual-circuit electric energy balance, which includes a rectifier unit, two inverter units, two DC circuits, two voltage collection units, an energy transmission unit, and an energy balance control unit. The input end of the rectifier unit is connected to the AC power grid; the output ends of the two inverter units are used to be connected to two loads respectively; the two ends of the two DC circuits are respectively connected to the output end of the rectifier circuit and the input end of the two inverter units; the two voltage collection units are respectively connected to the two DC circuits; the two ends of the energy transmission unit are respectively connected to the two DC circuits; and the energy balance control unit is connected to the two voltage collection units, the energy transmission unit, and the two inverter units. The variable frequency power supply device with dual-circuit electric energy balance makes the voltages of the two DC circuits tend to a balanced voltage, thereby achieving a complementary state of electric energy for the two loads, reducing power consumption, and preventing power accumulation and impact on the AC power grid.

The application discloses a bidirectional DCDC circuit and a photovoltaic energy storage inverter. The photovoltaic energy storage inverter is used for connecting a photovoltaic module, a battery and an alternating current end. The bidirectional DCDC circuit comprises a first direct current end, a second direct current end, a transformer, a first full-bridge circuit connected between the first direct current end and a primary side of the transformer, a second full-bridge circuit connected between a secondary side of the transformer and the second direct current end and a first capacitor. The first full-bridge circuit is directly connected with the primary side of the transformer and / or the second full-bridge circuit is directly connected with the secondary side of the transformer. The first capacitor is located between the second full-bridge circuit and the second direct current end and is connected with positive and negative poles of the second direct current end. The bidirectional DCDC circuit provided in the application uses leakage inductance of the primary side of the transformer and the first capacitor to form an LC resonant circuit instead of an LC resonant circuit arranged at two ends of the transformer, so that the function of the resonant circuit is realized while the number and volume of electrical elements of a topological structure are reduced, thereby reducing the cost.

This utility model discloses a substation emergency backup power supply system and a substation power outage control system. The substation emergency backup power supply system includes: a main control circuit, an AC-to-DC circuit, an auxiliary power supply, a battery module, a constant current charging circuit, a battery voltage acquisition circuit, a battery switching circuit, and a motor control circuit. The output terminal of the main control circuit is connected to the input terminal of the motor control circuit, enabling it to send control signals to the motor control circuit. The motor control circuit is connected to a drive mechanism, which is connected to the substation high-voltage switch, enabling it to control the switching action of the substation high-voltage switch. The substation emergency backup power supply system and substation power outage control system proposed in this utility model can improve the safety and intelligence of substation power outage shutdown.

The invention discloses an alternating current and direct current excitation device for a pumped storage unit excitation system, which comprises a direct current excitation loop, an alternating current excitation loop, a field suppression switch and a rotor loop, and is characterized in that the direct current excitation loop and the alternating current excitation loop are connected in parallel, the output end after parallel connection is connected with one end of the field suppression switch, and the other end of the field suppression switch is connected with the rotor loop; a connection path of the alternating current excitation loop comprises an alternating current power supply, an alternating current switch, a fuse F1, a transformer and a rectifier bridge, and a connection path of the direct current excitation loop comprises a direct current power supply, a direct current switch, a fuse F2, a divider resistor R1 and a diode. Isolation and mutual crossing prevention of an alternating current circuit and a direct current circuit are achieved through a rectifier bridge of the alternating current excitation loop and a diode of the direct current excitation loop, automatic mode switching is achieved in cooperation with an excitation regulator, seamless switching to the alternating current excitation loop can be achieved when the direct current excitation loop breaks down, and it is guaranteed that the pumped storage unit is reliably started when a power grid is dispatched emergently.

This invention provides a switching power supply, an AC-DC circuit, an input voltage detection circuit, and a method. The first end of the secondary coil of a transformer is connected to the anode of a rectifier diode, and the cathode of the rectifier diode is connected to the positive terminal of a filter capacitor. The second end of the secondary coil of the transformer, the negative terminal of the filter capacitor, and the positive terminal of the sampling capacitor are all grounded. The cathode of the diode is connected to the first end of the secondary coil of the transformer, and the anode is connected to the negative terminal of the sampling capacitor. The negative terminal of the sampling capacitor is grounded sequentially through a third sampling resistor and a second sampling resistor. The common terminal of the third and second sampling resistors is connected to a voltage detection terminal and, through a first sampling resistor, to a reference voltage input terminal. A reference voltage is input to the reference voltage input terminal. The control unit detects the voltage at the voltage detection terminal and calculates the magnitude of the input AC voltage based on the relationship between the AC voltage and the voltage at the voltage detection terminal.

The utility model discloses a universal conversion device for converting an LVDS (Low Voltage Differential Signaling) input signal into a V-By-One output signal, which comprises an LVDS input interface, a master control conversion chip, a V-By-One output interface, an NS / JEIDA configuration, a partition selection configuration, a direct current-direct current circuit, a nonvolatile memory chip and an expansion power supply head, the main control conversion chip is electrically connected with the LVDS input interface and receives a 2-port LVDS signal, the main control conversion chip outputs an 8-Lane V-By-One signal, the V-By-One output interface is electrically connected with the main control conversion chip and receives the 8-Lane V-By-One signal, and the NS / JEIDA configuration is electrically connected to the main control conversion chip.

The invention discloses a power transmission line induction power taking system and a self-adaptive variable step size maximum power tracking method. The power taking system comprises a CT type induction power taking unit, the CT type induction power taking unit is connected with a rectification circuit, the rectification circuit is connected with a filter circuit, and the filter circuit is connected with a DC-DC circuit. The power taking system further comprises an MOS tube arranged on the rectification side, the MOS tube serves as a bypass switch and is connected with the controller, and the controller is connected with the voltage and current sampling circuit and the load. When the output power needs to be reduced, the MOS is conducted. The controller controls the work of each module and monitors sampling signals of voltage and current in real time. If the output voltage exceeds the discharge voltage, the bypass switch MOS tube needs to be controlled to be conducted, and when the current of the power transmission line is low, power can be taken at the maximum power. The maximum power tracking algorithm realizes dynamic stability of the power under the condition that the voltage and the current are stable. The automatic adjustment step length is designed based on the self-adaptive variable step length perturbation and observation method, and the maximum power point can be tracked at a high speed and with high precision.

An embodiment of the present invention relates to a method for designing parameters of a capacitive-resistive absorption circuit for the front-stage DC-DC of an in-vehicle auxiliary power supply. The method includes: creating first time-domain and S-domain models of the front-stage DC-DC circuit; determining first voltage and current S-domain expressions of the capacitive-resistive absorption circuit; substituting preset system parameters into the first voltage and current S-domain expressions to generate corresponding second voltage and current S-domain expressions; determining the capacitance parameter C according to the second voltage S-domain expression S ; performing time-domain expression conversion on the second voltage and current S-domain expressions to generate corresponding first voltage and current time-domain expressions; determining the resistance parameter R according to the capacitance parameter C S , the first voltage, and the first current time-domain expressions S . Through the present invention, the design accuracy is ensured.

This application provides an uninterruptible power supply (UPS), an uninterruptible power supply control method, a related apparatus, and a system. In one example, the UPS determines a target value of a SOC of a battery of the UPS; and controls, based on the determined target value, a rectifier circuit and a direct current-to-direct current circuit in the UPS to charge the battery to make the SOC of the battery equal to the target value, or controls, based on the determined target value, an inverter circuit and a direct current-to-direct current circuit in the UPS to discharge the battery to make the SOC of the battery equal to the target value.

Some embodiments provide a DC solid state protection device that includes a capacitor configured such that in the event of a short-circuit condition, the capacitor provides all the short-circuit current required for the solid state protection device to detect a current indicative of a short-circuit condition and to cause a solid state switch to be opened, thereby tripping the solid state protection device.

The present invention claims protection for a modeling method based on a high turns ratio coupled inductor DC-DC. This method includes considerations of the influence of leakage inductance and right half-plane zeros in the precise analysis of high turns ratio coupled inductor DC-DC circuits. The coupled inductor boost converter can achieve high gain, or small input current ripple, and a high recovery rate of the energy of the leakage magnetic inductance. Three states of the circuit are selected for analysis under the dual criteria of accuracy and complexity. In the dynamic analysis of the mutual inductance coupled high turns ratio circuit, a model considering the leakage inductance in the primary of the high turns ratio coupled inductor circuit is used for modeling, and the analytical expressions of the DC turns ratio and the small-signal transfer function are obtained to simplify the design of the control part.

The positive and negative current overcurrent protection self-locking circuit comprises a power supply circuit, a positive and negative current detection circuit, a positive current comparison circuit, a negative current comparison circuit, a level self-locking circuit, an overcurrent reset circuit and a control output circuit, one end of the positive current comparison circuit and one end of the negative current comparison circuit are respectively connected with the positive and negative current detection circuit, the other end of the positive current comparison circuit and the other end of the negative current comparison circuit are respectively connected with the level self-locking circuit and the overcurrent reset circuit, and the overcurrent reset circuit is further connected with the level self-locking circuit. The level self-locking circuit is connected with the control output circuit; the power supply circuit is connected with the positive and negative current detection circuit, the positive current comparison circuit, the negative current comparison circuit, the level self-locking circuit, the overcurrent reset circuit and the control output circuit. By adopting the over-current protection circuit, accurate and reliable over-current protection can be provided for a direct-current circuit.