1536 results about "Single phase" patented technology

The invention provides a single-phase four-quadrant rectifier IGBT open-circuit fault diagnosis method under multiple working conditions, and relates to the technical field of IGBT fault diagnosis. Historical data of alternating current side voltage, alternating current side current and direct current side voltage of the single-phase four-quadrant rectifier are obtained, and a total harmonic distortion rate threshold value, a direct current side voltage threshold value and an alternating current side current first threshold value are obtained. And constructing and training an IGBT open-circuit fault positioning identification model. Detecting the total harmonic distortion rate of the alternating-current side current of the single-phase four-quadrant rectifier in real time, if the total harmonic distortion rate exceeds a threshold value, entering fault positioning, collecting and calculating the average value of the direct-current side voltage and the alternating-current side current in the period, and judging the fault of the single-phase four-quadrant rectifier under the specific working condition according to the comparison of the average value and the threshold value. Or using an IGBT open-circuit fault positioning identification model to diagnose the fault; if the threshold value is not exceeded, the next period is continuously monitored. According to the invention, the IGBT fault diagnosis efficiency and accuracy of the single-phase four-quadrant rectifier are improved.

The invention belongs to the field of stability analysis of a grid-connected system of a grid-building converter, and particularly relates to a grid-building converter grid-connected resonance risk analysis method considering virtual impedance, which comprises the following steps: S1, establishing a three-phase time domain differential equation and simplifying the equation into a single-phase equivalent time domain model; converting into a harmonic state space model of the main circuit; s2, constructing a harmonic state space model of a control system comprising an active power control loop and a reactive power control loop; s3, introducing a virtual impedance control link, and correcting the voltage amplitude reference phasor output by the reactive power control loop; deriving an expression of a modulation signal disturbance phasor; s4, obtaining a complete frequency domain admittance model YGSC of the network construction converter considering the influence of the virtual impedance; an open loop gain TGFM of the grid converter grid-connected system is constructed; and S5, drawing a Nyquist curve based on TGFM, and carrying out resonance risk determination. According to the method, the interaction dynamic characteristics of the network building converter and the power grid under the influence of the virtual impedance can be accurately represented, and the resonance risk of the grid-connected system is evaluated.

The invention discloses a centralized FA broken line positioning criterion anti-interference method considering noise interference, and the method comprises the steps: collecting the data of each node of a power distribution network line in real time, building a sequence component network model under a single-phase broken line ungrounded fault, carrying out the dynamic threshold analysis of an electrical quantity through employing a sliding time window algorithm, and setting an electrical quantity mutation criterion. And constructing an anti-interference criterion, determining whether to trigger fault positioning or not through the anti-interference criterion when sudden change of electrical quantity occurs, determining a fault section in combination with topology analysis when fault positioning is performed, and controlling upstream and downstream switches to isolate the fault and transfer the fault to a non-fault section. According to the scheme, various noise interferences in the power distribution network are effectively suppressed, the accuracy of fault signal judgment is improved, and the conditions of misjudgment and missed judgment are reduced; secondly, considering different conditions of the power distribution network, performing targeted setting and adjustment on a sequence component network model, an anti-interference criterion threshold value and the like, so that the method can adapt to a complex power distribution network operation environment, and the reliability of fault positioning is improved.

The invention discloses a phase change latent heat slow-release single-phase immersion liquid cooling intelligent temperature control adjusting method and system, and relates to the technical field of electronic equipment heat management. The phase change latent heat slow-release single-phase immersion liquid cooling intelligent temperature control adjusting method comprises the following steps: S1, collecting phase change liquid cooling temperature control data, and preprocessing the phase change liquid cooling temperature control data; s2, evaluating the running state of the server, assigning a thermal response level identifier based on an evaluation result, and constructing a thermal response state data set; s3, evaluating the cooling slow release capability in a temperature control early warning state and a thermal shock state, and generating and executing a self-adaptive cooling adjustment strategy in a grading manner; and S4, after the cooling regulation strategy is executed, the response efficiency of the cooling strategy is evaluated, a cooling strategy optimization instruction is generated, and strategy closed-loop regulation is realized on the basis of monitoring the change trend of an evaluation result in a continuous regulation period. The problem that the chip temperature of an existing liquid cooling system fluctuates abnormally due to cooling capacity response lag in an instantaneous high-load scene is solved.

The invention discloses a virtual reactive power plant user single-phase asynchronous motor reactive power regulation method, and relates to the technical field of electrical equipment control, and the method comprises the steps: collecting the real-time state data of a key node of a power distribution network, and building a short-term prediction model based on the state data; setting a judgment condition according to a prediction result of the model, generating a preliminary reactive power regulation instruction, and adjusting the priority and the regulation amplitude of the preliminary reactive power regulation instruction in real time based on dynamic updating of a prediction trend; issuing the adjusted reactive power adjustment instruction to a user terminal, and performing cooperative processing based on distributed coordination control to generate a final cooperative adjustment instruction; executing an action of cutting off the split-phase capacitor of the single-phase asynchronous motor according to the coordinated adjustment instruction; according to the invention, the split-phase capacitance of the single-phase asynchronous motor at the user side is regulated and controlled by using the virtual reactive power plant, so that low-cost, quick-response, continuous and accurate reactive power regulation is realized, and the problems of reactive power excess and high voltage of a power grid are effectively solved.

The invention relates to the technical field of power distribution network fault monitoring and forest fire early warning, and discloses a high-voltage line tree line fault ignition time early warning method and device and a medium, and the method comprises the steps: collecting electrical characteristic data and non-electrical characteristic data in a single-phase tree contact grounding fault process in real time; performing preprocessing and sliding window processing on the electrical characteristic data to screen out a key characteristic set; establishing a thermal-electric coupling model representing the exponential decay relation of the equivalent grounding resistance along with the rise of the tree body temperature; training a plurality of different types of data-driven models based on the key feature set to regressively predict the ignition time countdown; taking prediction results of the plurality of data driving models on the training set as input, and taking real ignition time as a target to train a linear regression model as a fusion device so as to obtain an ignition time countdown early warning model; and according to a final predicted value output by the ignition time countdown early-warning model, determining and outputting an early-warning level and a confidence coefficient. According to the invention, early warning can be realized hundreds of seconds before open fire appears.

An onboard charging system for an electric vehicle includes a charging port configured to receive a single-phase AC power, a power outlet configured to provide the single-phase AC power to one or more external devices, a single-phase inverter connected to the power outlet and configured to provide power splitting functionality, a DC battery selectively coupled to the charging port, a bidirectional inverter configured to convert AC power to DC power and to convert DC power to AC power, the bidirectional inverter is selectively coupled to the battery, an electric motor coupled to the bidirectional inverter and selectively coupled to the charging port, a DC-AC converter selectively coupled to the electric motor and selectively coupled to the power outlet, and a DC-DC converter coupled to the DC-AC converter and selectively coupled to the battery.

The invention is suitable for the technical field of power system high-voltage electrical equipment test, and provides a high-voltage circuit breaker direct test loop parameter setting method based on a particle swarm optimization algorithm, and the method comprises the steps: enabling a three-phase direct test loop to be equivalent to a single-phase loop according to symmetry, and enabling a transformer, an electric reactor, a power grid or an impact generator to be equivalent to an inductor and a voltage source; establishing an equation set according to the KCL, the KVL and element characteristics; performing nondimensionalization by using the voltage and current standard values and the conversion relation between the time domain and the angle domain to obtain a dimensionless equation; sorting to obtain a differential equation of per unit values of voltages at two ends of the circuit breaker and dimensionless parameters; and constructing an optimization search space and value function by taking the dimensionless parameters as decision variables of a particle swarm optimization algorithm, and operating the algorithm for multiple times to obtain the optimal dimensionless parameters so as to complete loop parameter setting. According to the scheme, test loop parameter setting can be automatically completed, manual debugging is reduced, the setting efficiency and precision are improved, and it is guaranteed that a circuit breaker test result meets the standard.

The invention relates to a single-phase intelligent electric energy meter, which relates to the technical field of electric meters, and comprises an electric meter body with a wiring area and a data storage area, a communication module detachably mounted in the data storage area, and a wiring terminal group arranged in the wiring area, the first cover plate and the second cover plate respectively cover the data storage area and the wiring area. And the first cover plate and the second cover plate are detachably connected with the electric meter body through the first fixing piece and the second fixing piece respectively. The linkage relation between the first fixing piece and the second fixing piece is established on the structure, so that the second fixing piece is locked when the first cover plate is in the covering state, and the second fixing piece is unlocked after the first cover plate is taken away and rotated to the maximum opening and closing position. According to the structure, a mechanical linkage principle is utilized to restrain a dismounting sequence, and an operator is guided to dismount the communication module and then dismount the wiring terminal group to a certain extent, so that the risk of adverse effects of misoperation on the stability of communication data can be reduced.

The present disclosure relates to circuits for connecting components of a hydrogen plant to a power grid to power the components in an efficient manner. In one implementation, power-side alternate current (AC) to direct current (DC) converters may be connected to a source power grid without the need for an isolation transformer by providing separate buses between the power-side AC-DC converters and load-side DC-DC converters instead of a shared DC bus between the converters. Other implementations for connecting components of a hydrogen plant to a power grid may include an adjustable transformer, such as a tappable transformer or an autotransformer, to connect any number of auxiliary loads of the plant to the power grid. The adjustable transformer may provide for various types of auxiliary load devices to connect to the power provided by the transformer at the same time, including both three-phase devices and one-phase devices.

The invention provides a three-phase alternating current phase angle measuring device and method, and belongs to the technical field of phase angle measurement. The three-phase alternating current phase angle measuring device comprises a main control chip and two metering chips. The main control chip has a fundamental wave zero-crossing function, the main control chip collects a phase angle A based on a fundamental wave zero-crossing interruption function and linear interpolation, the precision of the phase angle A is high, harmonic interference can be effectively avoided, the two metering chips collect a phase angle B and a phase angle C respectively, a single-phase chip and related peripheral circuits are reduced, the price is lower, and the cost is lower. The cost advantage is obvious.

The invention relates to an open-circuit fault detection method and device, a domain controller, a system and a vehicle, and relates to the technical field of open-circuit fault detection. According to the method, the three-phase current data of the cooling water pump can be firstly obtained, and under the condition that at least one phase of current data in the three-phase current data meets the pre-judged open circuit condition, at least one of the following motor parameters including the three-phase current unbalance degree, rotor data and water pump vibration data is monitored. If it is monitored that any motor parameter in the three-phase current unbalance degree, the rotor data and the water pump vibration data is abnormal, it is determined that the current data meeting the pre-judgment open-circuit condition occurs, and an open-circuit fault occurs to the target phase corresponding to the current data meeting the pre-judgment open-circuit condition. Therefore, under the condition that the suspected open circuit of the corresponding phase is predicted according to the single-phase current, prediction can be performed by fusing at least one motor parameter of the cooling water pump, so that the misjudgment rate of the open-circuit fault of the cooling water pump can be reduced and the open-circuit phase positioning precision can be improved through multi-data cooperative detection.

The invention relates to a single-phase asynchronous capacitor motor, which comprises a stator part, a rotor part and a motor rotating shaft, the capacitor motor further comprises a casing, the casing comprises a front casing wall, a rear casing wall and a ventilation rear cover, the front end part of the motor rotating shaft is coupled in the front casing wall through a front bearing, and the rear end part of the motor rotating shaft is coupled in the rear casing wall through a rear bearing. The rear end part of the motor rotating shaft is coupled in the rear shell wall through a rear bearing, the rear bearing comprises an outer bearing sleeve, an inner bearing sleeve and a bearing roller, the inner bearing sleeve is fixedly sleeved on the rear end part of the motor rotating shaft, the inner bearing sleeve comprises an inner bearing ring pipe and a connecting disc body, and the inner bearing ring pipe is sleeved on the inner bearing ring pipe. The connecting disc body is fixedly connected to the outer end of the inner bearing ring pipe, the coaxial cooling fan is connected to the connecting disc body, when the inner bearing sleeve rotates, the connecting disc body and the motor rotating shaft coaxially and synchronously rotate, and the connecting disc body drives the coaxial cooling fan and the motor rotating shaft to coaxially and synchronously rotate.

The embodiment of the invention discloses a multiplex type three-stage starting power generation controller, and relates to the technical field of aviation three-stage starting power generators. In the starting stage, an H-bridge inverter in the starting power generation controller provides single-phase alternating-current exciting current for a main exciter stator exciting winding through SPWM modulation so as to establish a pulsating magnetic field to provide exciting current for a main motor, and a three-phase full-bridge inverter provides armature current for a main motor stator armature winding through SVPWM modulation. In a power generation stage, an anti-parallel diode of the three-phase full-bridge inverter is used as a rectification circuit of the auxiliary exciter, and the H-bridge inverter adopts a PWM chopping mode to operate as an asymmetric half-bridge circuit. A power generation controller and a starting controller are integrated into a whole, and by changing the modulation mode of a hardware circuit, the control function of the three-stage starting generator at different stages can be realized by only one controller, so that the structure of the starting power generation controller is simplified, the system integration degree of the three-stage starting generator is improved, and the volume and the weight of the system are reduced.

The single-phase bidirectional single-stage isolation matrix converter comprises a pre-stage circuit and a post-stage circuit, and the pre-stage circuit comprises an LC filter on the power grid side, a pre-stage single-phase matrix conversion circuit and an LLC resonance circuit with a high-frequency transformer; the post-stage circuit comprises a post-stage conversion circuit and an output filter capacitor; the front-stage single-phase matrix conversion circuit comprises four bidirectional switch assemblies of a full-bridge structure. Each bidirectional switch assembly comprises two unidirectional controllable MOS tubes which are reversely connected in series, one end of each bidirectional switch assembly is connected to an L line or an N line of a power grid, and the other end of each bidirectional switch assembly is connected to the LLC resonance circuit. The rear-stage conversion circuit comprises a bidirectional MOS (Metal Oxide Semiconductor) tube bridge circuit and three high-frequency transformer secondary windings which are in triangular connection or star connection; and two end points of each secondary winding are respectively connected to the upper MOS tube and the lower MOS tube of the corresponding bridge arm and then are connected to output positive and negative ends. The converter has the advantages of high power density, low current harmonic, high power factor and the like, and is small in size, strong in anti-interference capability, wide in buck-boost range, and safe and reliable in commutation.

The present application relates to the technical field of liquid-cooling heat dissipation. Provided are a single-phase immersion liquid cooling system, a control method, a control device and a storage medium. The system comprises: a liquid cooling chassis, a first cooling circuit and a second cooling circuit, wherein the first cooling circuit comprises a flow restrictor; the flow restrictor is configured to divide a region inside the liquid cooling chassis into a first cooling region and a second cooling region, which are isolated from each other; the first cooling region contains a cooling liquid that enters the flow restrictor through the first cooling circuit, and the second cooling region contains a cooling liquid that enters the liquid cooling chassis through the second cooling circuit; there is a difference in heat dissipation demand between the first cooling region and the second cooling region; cooling liquid inlets and outlets of the first cooling circuit and the second cooling circuit on the liquid cooling chassis are different; and there is a difference between the flow rates of the cooling liquid in the first cooling circuit and the cooling liquid in the second cooling circuit.

The invention provides a charging system with high-voltage protection, which relates to the technical field of elevator emergency power supply and comprises a transformer, a voltage stabilizing circuit, a sampling circuit, an on-off circuit, a surge protection circuit, a constant current and voltage stabilizing circuit and a control circuit. The transformer reduces commercial power high voltage to low voltage; the voltage stabilizing circuit provides a stable direct-current power supply for the sampling and control circuit; the sampling circuit is used for conditioning the AC voltage and outputting a feedback signal; and the control circuit performs mode analysis by utilizing a pre-judgment algorithm according to the feedback signal so as to control the on-off circuit to cut off the mains supply input or switch the output mode of the constant current and voltage stabilizing circuit. Through an intelligent protection mechanism comprising sampling, control and on-off circuits, the device can be suitable for single-phase electric equipment, and quick and accurate response to abnormal high voltage is realized. And the transformer is adopted for voltage conversion and isolation, and the surge protection circuit and the on-off circuit are combined, so that the protection performance is ensured, and the overall cost and size of the system are effectively controlled.

The invention discloses a dual three-phase permanent magnet synchronous motor winding open-circuit fault diagnosis method, belongs to the technical field of motor control and fault diagnosis, and aims to solve the problem that a fault continuously damages a motor during the existing dual three-phase permanent magnet synchronous motor open-circuit fault diagnosis period. The method comprises the following steps: mapping six-phase stator current to a torque plane, a harmonic plane and a zero-sequence plane through vector space decoupling transformation; decomposing the current of the torque plane into two independent torque sub-plane currents; monitoring the harmonic current amplitude of the harmonic plane, and when conditions are met, starting a fault diagnosis process: according to the characteristics of the two torque sub-plane currents in a half fundamental wave period, calculating a primary fault flag bit, and judging the type of an open-circuit fault; calculating a secondary fault flag bit, and positioning a single-phase open-circuit fault and a two-phase open-circuit fault; in the diagnosis process, a phase-locked loop based on a second-order generalized integrator is synchronously utilized to update a harmonic current reference value so as to suppress motor torque fluctuation.

The invention relates to the technical field of communication, in particular to an uplink signal frequency offset processing method and a related device. The method comprises the following steps: network equipment determines a first frequency offset estimation value of a first uplink signal from a terminal; and determining a frequency offset processing mode of the first uplink signal at least based on the first frequency offset threshold value and the first frequency offset estimation value. Thus, frequency offset processing is performed on the first uplink signal by using the frequency offset processing mode corresponding to the first uplink signal, accurate frequency offset processing can be performed on the first uplink signal, large resource overhead of a communication system caused by a single phase-locked loop mode is avoided, the uplink frequency synchronization precision is ensured, and the user experience is improved. And the uplink frequency synchronization complexity is reduced, so that the communication reliability is effectively improved.

The invention provides an on-site calibration device, method and system applied to a single-phase electric energy metering device, and relates to the technical field of metering device calibration, and the device comprises a main body, a display screen and a clamp meter. A crimping panel is arranged on the lower end surface of the main body; a plurality of crimping needles are arranged on the crimping panel, and the crimping needles are matched with crimping holes formed in the single-phase electric energy metering device to realize crimping; a locking nut is arranged on the main body, the locking nut penetrates through the main body from top to bottom, and the main body is fixed on the single-phase electric energy metering device through the configuration of the locking nut and a threaded hole formed in the single-phase electric energy metering device. According to the invention, the device main body and the single-phase electric energy metering device are buckled together, a worker can leave the field only by completing buckling, and returns to the field to be taken back after the device completes automatic inspection, so that the worker efficiency and multi-point inspection are both considered, and the overall performance of the single-phase electric energy meter within the working range of the single-phase electric energy meter is inspected.

The invention relates to the technical field of intelligent operation of a power distribution network, in particular to an intelligent three-phase imbalance treatment method, which comprises the following steps of: firstly, acquiring three-phase current, three-phase voltage and electrical characteristic quantity of each single-phase load, and carrying out commutation adaptability evaluation on the load based on a real-time power factor, a current harmonic distortion rate and a load power flow direction; and calculating the three-phase unbalance degree of each power supply branch, identifying an extreme branch with the unbalance degree exceeding the standard, and screening out loads with optimal commutation adaptability parameters to form a candidate load set. And generating a commutation priority sequence for the candidate load through a historical commutation frequency and real-time contribution degree two-factor model. And triggering zero-millisecond seamless commutation under the conditions of meeting a safe voltage threshold and equal voltage time, verifying a switching result after commutation, limiting the number of commutation times of single treatment, and monitoring the three-phase unbalance degree in real time until the three-phase unbalance degree is recovered to a qualified range. According to the invention, the accuracy and safety of the commutation decision can be improved, and the dynamic balance adjustment of the three-phase load is realized.

The invention provides an active support control method for a single-phase cascaded optical storage grid-connected system, aiming at challenges caused by fluctuation, intermittency and reverse peak regulation of photovoltaic resources in a photovoltaic energy consumption process and the problem of insufficient active support capability of a micro-grid for a large power grid under the access of high power electronic equipment. The low-voltage photovoltaic units are boosted by inverter cascading, and each photovoltaic unit is equipped with stored energy to stabilize photovoltaic fluctuation. A grid-side current source inverter is controlled by a virtual synchronous generator (VSG), so that the active support of the inverter on a large power grid frequency is ensured; other voltage source inverters adopt power factor angle droop control, and an active power compensation item is introduced, so that self-synchronization between the inverters and accurate power equalization between energy storage units are ensured. Compared with a traditional control method, the method can control active power and reactive power at the same time, has frequency supporting capacity, is low in communication cost, and provides a new solution thought for the problem of large-scale photovoltaic grid connection.

The invention relates to an overvoltage risk assessment method, device and equipment for non-full-phase operation of a new energy access weak power grid system. The method comprises the following steps: acquiring electrical quantity data of the new energy access weak power grid system, and a voltage source, grid-connected equivalent impedance, series equivalent impedance and non-full-phase operation line impedance of a power transmission line of the new energy access weak power grid system with a single-phase fault; calculating n positive sequence current vectors and negative sequence current vectors according to each piece of electrical quantity data; calculating n positive sequence port voltage vectors and negative sequence port voltage vectors according to the fault data, each positive sequence current vector and each negative sequence current vector; according to the positive sequence voltage component rated value, each positive sequence port voltage vector and each negative sequence port voltage vector, actual positive sequence voltage and actual negative sequence voltage are obtained through calculation; and according to the actual positive sequence voltage, the actual negative sequence voltage and the positive sequence voltage component rated value, calculating to obtain a single-phase voltage maximum value, and according to the single-phase voltage maximum value, judging whether the system has an overvoltage risk in a non-full-phase operation state.

A transformerless, high efficiency, three-level, high power density, wide input voltage range, single-phase DC / AC inverter is provided. The inverter includes a single DC input power supply, a first semiconductor switch, a second semiconductor switch, a third semiconductor switch, a fourth semiconductor switch, a fifth semiconductor switch, a sixth semiconductor switch, a seventh semiconductor switch, an eighth semiconductor switch, a ninth semiconductor switch, a first inductor, and a second inductor.

The embodiment of the invention provides a method and a system for charging a bootstrap capacitor of an electric compressor controller. The method comprises the following steps: S1, calculating time required for fully charging the bootstrap capacitor according to resistance and capacitance values of a bootstrap charging circuit; s2, the minimum duty ratio is set based on the driving control frequency of the controller, and the single switching charging duration of the bootstrap capacitor is calculated; s3, working time of low-voltage side switch tubes in the three single-phase half-bridge units is calculated; and S4, controlling the bootstrap capacitor of the corresponding single-phase half-bridge unit to be charged to a required voltage value. Relates to the field of new energy automobile electric compressors. The time required for fully charging the bootstrap capacitor is accurately calculated according to the resistance and capacitance values of the bootstrap charging circuit, so that the charging efficiency and the driving stability of the high-voltage side switching tube are improved, and the bootstrap charging circuit is particularly suitable for reliable operation of a new energy truck in frequent start-stop and high-load scenes.

The invention discloses a generator stator grounding fault active arc extinction method based on double-loop quasi-PR control, and the method comprises the following steps: S1, monitoring the fundamental wave zero-sequence voltage and third harmonic voltage of a neutral point and a generator end of a generator, and carrying out the fault phase selection and positioning when a single-phase stator grounding fault occurs; s2, according to a fault positioning result, calculating a fault winding potential Ef, and setting a negative value-Ef of the fault winding potential Ef as a neutral point target compensation voltage; s3, a cascaded H-bridge converter is adopted as a topological structure of the active regulation and control device, and a double-closed-loop control framework composed of a voltage outer loop and a current inner loop is established; s4, setting quasi-PR control units for the fundamental wave component and the third harmonic component in the voltage outer ring and the current inner ring respectively; and S5, controlling the cascaded H-bridge converter to output a compensation voltage consistent with the target compensation voltage-Ef, and injecting the compensation voltage into the neutral point of the generator. The voltage regulation and control precision and the arc suppression speed in the active arc suppression process of the generator can be improved, and the operation safety and reliability of the generator are improved.

The invention provides a UPS (Uninterrupted Power Supply) control method and device, which are used for reducing the power supply cost of a direct current bus. The UPS control method comprises the steps that when it is determined that a bypass module in a UPS works and the UPS has no fault, a first part of power module in the UPS is controlled to work in a harmonic compensation mode, and the UPS comprises the first part of power module and a second part of power module; detecting the bus voltage of each power module in the second part of power modules; an inverter in the target power module is controlled to obtain electric energy from the output end of the bypass module, single-phase rectification processing is conducted on the obtained electric energy, power is supplied to a direct-current bus in the target power module, and the target power module is the power module with the bus voltage smaller than the first set value in the second part of power modules.

The invention discloses a broadband impedance measurement device and a broadband impedance sweep frequency measurement method, and the device comprises a main path input switch, a disturbance control and gain calculation module, a main path output switch, and single-phase measurement units, wherein the number of the single-phase measurement units is equal to the number of electric phases of a power grid. The single-phase measurement unit comprises a broadband disturbance generator, an output filtering unit, a coupling transformer, a disturbance detection unit, a bypass switch and an output voltage and current detection unit. The disturbance control and gain calculation module is connected with the disturbance detection unit, the output voltage and current detection unit and the broadband disturbance generator. The method comprises the steps of injecting disturbance according to a sweep frequency point table; extracting disturbance response voltage according to the voltage of the secondary winding of the coupling transformer; calculating a disturbance gain according to the disturbance injection voltage and the disturbance response voltage; and comparing the disturbance gain with a preset risk gain threshold value and a preset early warning gain threshold value, and performing control according to a comparison result.

The invention relates to a current stress optimization hybrid modulation strategy of a three-phase dual-active bridge converter, which gets rid of a traditional symmetric bridge phase shift modulation strategy, provides a modulation mode of simultaneously switching on and off a b-phase switch tube and a c-phase switch tube in the three-phase dual-active bridge converter, and enables the phase a to be compared with the b-phase switch tube and the c-phase switch tube to have variable bridge internal shift. A modulation strategy of a three-phase dual active bridge converter similar to a DAB triple phase shift modulation mode is formed; meanwhile, mixed modulation is formed with single phase shift modulation of the three-phase dual-active bridge converter, total current stress serves as an optimization target, Pn is obtained through calculation of a PI controller, the voltage transformation ratio M at the moment is calculated, values of respective total current stress under the two kinds of modulation can be obtained, the total current stress under the two kinds of modulation is compared, and the optimal value of the total current stress under the three-phase dual-active bridge converter is obtained. And a modulation mode with the optimal real-time total current stress is selected, so that the total current stress of the converter is optimized under the same transmission power.

An electrical conductor monitoring system for single or multi-phase conductors is described. The monitoring system may be configured to monitor the health of a conduction system based on multi-phase sequences and / or current magnitude and angle vectors of multi-phase or single-phase current. In one example, the monitoring system includes an insulation health monitoring system having an input and output measurement devices, the input measurement device disposed at an input end of the electrical distribution system and structured to measure three-phase input currents, the output measurement device disposed at an output end of the electrical distribution system and structured to measure three-phase output currents; and a monitoring device communicatively coupled to the measurement devices and structured to receive the three-phase input and output currents from the measurement devices and determine a state of the insulation system based on the three-phase input and output currents. Other embodiments are described.