156 results about "Dc bus capacitor" patented technology

The invention discloses an intelligent charging pile core module based on a VIENNA structure, an electric energy quality management method, system and equipment and a storage medium, and belongs to the field of electric power system energy storage equipment.The intelligent charging pile core module based on the VIENNA structure comprises the steps that an integrated power conversion unit is constructed, the power conversion unit adopts a VIENNA rectifier topology, three-phase alternating current is converted into direct current, and the direct current is converted into direct current; a harmonic suppression structure linked with the control interface is arranged; state information in the operation process is collected and serves as input of the control strategy module; based on the state information, a modulation control instruction is generated in the control strategy module to drive the switching action of the power conversion unit; on the basis of the modulation control instruction, the switch control is executed, meanwhile, the direct-current side midpoint potential of the power conversion unit is synchronously adjusted, and the distribution of direct-current bus capacitor voltage is controlled; and identifying the current operation condition according to the state information, switching to a control template corresponding to the operation condition in the control strategy module, and generating a modulation control instruction.

The present application provides a power converter, comprising: a power conversion circuit and a control circuit. The power conversion circuit comprises an inverter circuit, a DC bus capacitor and a detection circuit, and the DC bus capacitor is connected in parallel with the inverter circuit. The DC bus capacitor comprises a positive bus capacitor and a negative bus capacitor connected in series. The inverter circuit comprises a bridge arm. The detection circuit is used to detect the voltage on both sides of the positive bus capacitor, the voltage on both sides of the negative bus capacitor and the output current of the bridge arm. The control circuit is used to control the bridge arm to switch from outputting two levels to outputting three levels within one switching cycle in response to preset conditions. The preset conditions are conditions based on the voltage of the positive bus capacitor, the voltage of the negative bus capacitor and the output current of the bridge arm. The present application uses a hybrid modulation of three levels and two levels, so that the power converter can achieve a balance between the quality of power output and power consumption, thereby improving the performance of the power converter.

The invention provides a wind power converter DC support capacitor health state real-time detection method, and belongs to the technical field of wind power converter DC support capacitor health state detection. Comprising the following steps: collecting a ripple voltage signal and a temperature signal of a DC bus capacitor in real time; variational mode decomposition is carried out on the ripple voltage signals, and time domain features, frequency domain features and nonlinear features of multi-mode components are extracted; meanwhile, mean value features and dynamic change rate features are extracted from the temperature signals; on the basis of robust principal component analysis, dimension reduction and feature enhancement are carried out on the extracted features, and a state feature matrix is generated; inputting the state feature matrix into a pre-trained intelligent learning model, and outputting a health state classification result of the DC support capacitor; according to the method, the health state of the capacitor is accurately reflected in real time, degradation and faults are found in time, and the method can be widely applied to real-time monitoring of the wind power converter.

The invention, which belongs to the technical field of the energy storage converter, discloses an electrical parameter sensing-based service life monitoring system for a capacitor of a network-forming type energy storage converter, comprising the following steps of: synchronously acquiring a direct-current voltage signal and a three-phase alternating-current signal of a direct-current bus capacitor through an electrical parameter acquisition module to form a multi-dimensional feature vector; a state observer built in the ESR estimation module is used for analyzing the signal, a target capacitor ESR value is obtained, and a capacitor core temperature value is obtained through back-stepping through an electric-thermal coupling field analysis model of a core temperature back-stepping module in combination with preset capacitor surface temperature data; based on the ESR value and the capacitor core temperature value, a life prediction module calculates the residual life and health degree index of the capacitor; and the power scheduling module executes capacitor health degree-power output joint scheduling according to the health degree index, adjusts the power fluctuation range of the converter, and feeds back real-time working condition data to the electrical parameter acquisition module, thereby realizing accurate monitoring of the capacitor state and intelligent scheduling of the converter power.

The invention relates to a composite function converter suitable for a multi-phase high-speed permanent magnet direct-current generator. An uncontrolled rectifier bridge arm is formed by connecting two high-frequency rectifier diodes in series; the controllable rectifier bridge arm is formed by connecting two IGBTs (Insulated Gate Bipolar Translator) with antiparallel diodes in series; an upper tube IGBT collector of the controllable rectifier bridge arm and a cathode of an upper tube diode of the uncontrolled rectifier bridge arm are connected in parallel with an anode of the intermediate bus capacitor; the emitting electrode of the lower tube IGBT and the anode of the lower tube diode of the uncontrolled rectifier bridge arm are connected in parallel with the cathode of the intermediate bus capacitor; the emitting electrodes of the upper tubes IGBT of the controllable rectifier bridge arms are respectively connected to the output end of the generator; the anodes of the upper diodes of the uncontrolled rectifier bridge arms are respectively connected to the other output ends of the generator; the interleaved BUCK module is connected between the intermediate DC bus capacitor and the load, and the BUCK control unit is used for controlling the interleaved BUCK module to operate; and the barring control unit is used for controlling the controllable rectifier bridge arm to realize a generator barring function.

The invention provides a three-phase low-voltage MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor) packaging integrated power module. A driving assembly, a direct-current bus capacitor and other modules are integrated in an aluminum shell package. The three DBC substrates respectively bear U-phase bridge arms, V-phase bridge arms and W-phase bridge arms, an upper bridge arm and a lower bridge arm of each phase are formed by a plurality of parallel MOSFET chips, drain electrodes of the chips are directly welded to a DBC upper copper layer, grid electrodes of the chips are connected with an upper-layer driving circuit board through copper columns, source electrodes of the chips are led out to a direct-current input terminal or an alternating-current output terminal through bonding wires, and a double-layer conductive structure is formed. A plurality of direct-current bus capacitors which are arranged above the aluminum shell in parallel are adjacently coupled with the DBC substrate, so that low-impedance energy buffering is realized; the alternating current output terminal is sleeved on the current sensor, detects the phase current and outputs the phase current through the signal terminal; and a thermistor is mounted on a copper layer on each DBC to monitor the junction temperature of the chip and provide over-temperature protection. The direct-current input terminal, the alternating-current output terminal, the power terminal and the signal terminal are integrally embedded in the aluminum shell and are directly butted with an external busbar and a controller, and additional sampling and driving boards are not needed.

The invention discloses an improved hybrid clamping three-level structure and a loss suppression method, and aims to suppress surge current and reduce switching loss by introducing a buffer inductor between a DC bus capacitor and the midpoint of a clamping diode, and maintain the inherent voltage self-balancing capability of the topology at the same time. Experimental verification shows that the surge current can be reduced to the level close to the load current, the turn-on loss is averagely reduced by 23%, and the reliability and efficiency of the series-connected SiC MOSFETs in medium-voltage direct-current application are remarkably improved.

The embodiment of the invention provides a wind power converter DC bus capacitor state monitoring system and method, and the method comprises the steps: firstly introducing a physical model of a capacitor temperature, and carrying out the decoupling compensation of a preliminarily estimated equivalent series resistor, so as to effectively strip the measurement disturbance caused by the fluctuation of an operation temperature; on the basis, working condition data such as active power of the converter are further fused, and a health baseline capable of being dynamically and adaptively adjusted along with the operation working condition is established as a judgment standard. And finally, comparing the equivalent series resistor subjected to multiple correction with the self-adaptive healthy baseline in real time, so as to accurately identify inherent performance degradation caused by self aging of the capacitor. In this way, interference of complex and changeable working conditions on monitoring results can be overcome, and therefore the accuracy and reliability of state evaluation are remarkably improved.

The present application provides a double-pulse test method, circuit and system. The double-pulse test method controls the inductance of the load inductor connected to the module to be tested to be less than the first threshold value during the first pulse of controlling the conduction of the switch tube to be tested. That is, even if the module to be tested adopts a load inductor with a smaller inductance during the first pulse, the energy transmitted from the DC bus capacitor to the load inductor can be reduced, and the degree of bus voltage drop of the high-power module when performing double-pulse testing can be reduced; no external capacitor pool is required, thereby avoiding the problem of low accuracy of test results caused by the external capacitor pool in the prior art. In addition, after the end of the first pulse, the present application can adopt a load inductor with a larger inductance. Therefore, during the double-pulse interval, the energy consumption of the load inductor is slow, and the current difference between the load inductor at the beginning of the second pulse and the end of the first pulse is small, thereby ensuring the accuracy of the test results.

The invention relates to a double-fed asynchronous motor debugging method and system based on a back-to-back converter, and belongs to the technical field of motor control. Comprising the following steps: supplying power to a three-phase alternating-current voltage regulator, and charging a direct-current bus capacitor by connecting a grid-side alternating-current contactor with a buffer resistor in parallel; when the DC bus capacitor is charged to a preset amplitude, the digital signal processor sends a closing signal to the AC contactor; after the alternating current contactor is switched on, pure open-loop debugging, current closed-loop debugging and rotating speed closed-loop debugging are respectively carried out on the rotor side; the upper computer controls the pulse width modulator to work, carries out excitation on the rotor, and monitors the voltage and phase of the stator end; when the voltage rises to a preset value and the phase is synchronized with the power grid, a closing signal is sent to the AC contactor at the stator side, and the motor stator is connected to the power grid. The problems that a traditional doubly-fed asynchronous motor is too large in starting current and complex in control link decoupling are solved, and the debugging reliability and efficiency are improved. In addition, debugging does not depend on additional prime mover dragging.

An economic photovoltaic inverter group control method, comprising calculating photovoltaic inverter group loss sources, photovoltaic inverter group losses including: IGBT power devices, filter inductance, DC bus capacitor and the like; reactive power setting through droop control; photovoltaic inverter group comprehensive operation loss minimum model; constraint condition of objective function; solving proportional coefficient through adaptive simulated annealing particle swarm optimization algorithm; obtaining photovoltaic inverter group reactive power proportional coefficient of photovoltaic inverter group at current applicable environment and operation loss minimum according to above results, through setting reactive power proportional coefficient, making photovoltaic inverter transmit and receive reactive power according to proportional coefficient in the process of droop control according to total reactive power requirement, achieving loss minimum result under the condition of guaranteeing normal grid-connected point voltage. The application realizes reasonable control of photovoltaic inverter to meet the demand of grid-connected point voltage regulation under the premise of photovoltaic inverter operation loss minimum.

The utility model discloses a seven-level inverter topology, which relates to the technical field of multi-level structures and comprises an upper bridge arm and a lower bridge arm, the upper bridge arm and the lower bridge arm are mutually symmetrical except for the direction of a diode, and a plurality of switch tubes, direct current bus capacitors and flying capacitors in the upper bridge arm and the lower bridge arm are connected according to a specific rule. Working modes with seven different output voltages are realized by controlling the conduction state of the switch tube; the topology realizes voltage division through the DC bus capacitor, realizes intermediate level transition through the flying capacitor, combines an optimized circuit structure and a control strategy, has the advantages of simple circuit design, high efficiency, stable output voltage and the like, and is widely applicable to high-voltage and high-power inverter systems.

This invention discloses a transient control method for a wind turbine grid-connected system that utilizes a reverse energy absorption branch, relating to the field of new energy technology. The energy-consuming branch is connected in parallel to the DC bus capacitor. The grid connection point voltage and DC bus voltage of the wind turbine grid-connected system are acquired. When the grid connection point voltage reaches a preset condition, a reference value for the d-axis current of the grid-side converter is calculated based on the grid connection point voltage and the voltage of the DC bus capacitor. Based on the reference value, the active power state of the grid-side converter is switched to an active power absorption state, allowing the DC bus capacitor to store electrical energy and raise the voltage. When the voltage of the DC bus capacitor is greater than the threshold voltage of the transistor, the transistor is controlled to be in the conducting state. Through this technical solution, the direction of energy flow on the DC bus between the turbine-side converter and the grid-side converter can be changed. Furthermore, by consuming excess energy through resistance, wind turbine output oscillations and DC-side overvoltage can be suppressed, and the synchronous stability of the wind turbine grid-connected system can be improved.

The invention discloses a low-speed electric vehicle battery off-line protection method and an off-line protection circuit thereof. A system battery is controlled through a normal state mode of the system battery to be connected with a direct-current bus capacitor where a three-phase half-bridge is located through closing of a normally open contact and a conversion contact of a relay for charging; in the battery offline state protection control mode, the reference voltage of a battery offline protection circuit is compared with the direct current bus voltage collected in real time, if the reference voltage exceeds the set reference voltage, braking current is generated in a vehicle motor, the vehicle is subjected to braking deceleration protection, and after the vehicle decelerates to be stable, a driver can conduct manual braking. And safe parking is realized. Braking current is generated in a vehicle motor under the condition that the vehicle is shut down without mechanical braking, the vehicle is braked, and inertial rolling control of the vehicle is restrained. And after the battery is offline, controllable braking torque can be provided, inertial sliding is prevented, and the offline safe parking reliability of the vehicle battery is improved.

The invention discloses an intelligent soft start protection method and circuit for a direct current bus capacitor, and the method comprises the control process: pre-charging the direct current bus capacitor: building a pre-charging loop through the connection of a pre-charging current-limiting resistor and the direct current bus capacitor, controlling the charging current of the direct current bus capacitor, and starting the pre-charging; after pre-charging is started, when the voltage drop at the two ends of the pre-charging current-limiting resistor is smaller than a set threshold value and the voltage at the two ends of the direct-current bus capacitor reaches the set threshold value, it is judged that pre-charging is completed; establishing a low-impedance loop between the power grid and the direct-current bus capacitor to finish soft start; monitoring over-current protection; according to the invention, closed-loop operation of soft start and protection of the direct-current bus capacitor is realized, and the risk that a power grid is directly connected to the direct-current bus capacitor to generate large impact current and further damage a loop device or cause tripping of a loop protection device is avoided; and meanwhile, rapid protection action can be realized under the condition that the DC bus capacitor-power grid connection loop is abnormal, and the safety and reliability of product and system application are improved.

The present application relates to the field of power electronics technology, and in particular to an inverter, an energy storage system, and a soft start method. The inverter includes an inverter circuit, a pre-charging circuit, and a control circuit. The inverter circuit includes a bus capacitor, a plurality of inverter bridge arms, and a plurality of first relays. The inverter bridge arms are respectively connected to an AC power grid through the first relays. The pre-charging circuit is connected between the AC power grid and the bus capacitor. When the voltage of the bus capacitor is less than a target threshold, the pre-charging circuit is turned on to allow the AC power grid to charge the bus capacitor. When the voltage of the bus capacitor is greater than or equal to the target threshold, the pre-charging circuit is disconnected and the first relay is closed. The bus capacitor is powered by the AC power grid to complete the soft start of the bus capacitor and wake up the DC power supply. The present application completes the charging of the DC bus capacitor of the inverter by the AC power grid through the pre-charging circuit, simplifies the circuit structure, reduces the circuit cost, and improves the reliability of the DC bus soft start.

The application provides a power converter, a controller, a power supply system and a midpoint voltage deviation control method, which are applied to the technical field of power electronics, and the power converter comprises a power conversion module, a main control module and at least two DC bus capacitors, each DC bus capacitor is connected in series between the positive electrode of a DC bus and the negative electrode of the DC bus, and since the midpoint voltage deviation suppression strategy in the related art can only achieve good midpoint deviation suppression effect when the bus voltage is high, the main control module increases the bus voltage when the voltage deviation between the capacitance voltage of at least one DC bus capacitor and the target capacitance voltage is greater than the first preset deviation threshold, thereby providing guarantee for the midpoint voltage deviation suppression strategy to achieve better midpoint deviation suppression effect, improving the midpoint deviation suppression effect and significantly improving the stability of the power supply system.

This invention discloses a control method for a cascaded photovoltaic inverter under phase-to-phase short-circuit fault conditions in the power grid, belonging to photovoltaic power generation technology in the field of electrical engineering. The steps are as follows: First, determine the fault type of the three-phase power grid and detect the ratio of the line voltage amplitude of the two faulty phases after the voltage drop to that of the two faulty phases before the voltage drop. Then, use a proportional resonant controller to control the grid-connected current. Second, adopt an adaptive zero-sequence voltage compensation control strategy based on active current injection to adaptively compensate the zero-sequence voltage according to the maximum positive-sequence active current actually output by the inverter. Third, control the average value of the DC bus capacitor voltage of the H-bridge converter by controlling a two-level full-bridge LLC converter with one input and m outputs. When a phase-to-phase short-circuit fault occurs in the power grid, this control method improves the adaptability of the cascaded photovoltaic grid-connected inverter to different output power and different grid voltage drop depths, and improves the system's low-voltage ride-through capability.

This invention provides a three-phase isolated bidirectional AC-DC converter and a component monitoring method, relating to the field of AC-DC converter technology. It includes a three-phase full-bridge circuit, a resonant network circuit, an output rectifier circuit, a status monitoring circuit, and a controller. The three-phase full-bridge circuit includes an A-phase bridge arm unit, a B-phase bridge arm unit, and a C-phase bridge arm unit, with the three-phase output power supply connected to each unit respectively. The resonant network circuit is connected to the three-phase full-bridge circuit, and the output rectifier circuit is also connected to the resonant network circuit. The controller is communicatively connected to the switching transistors in the three-phase full-bridge circuit. A temperature monitoring unit is connected to the switching transistors in the three-phase full-bridge circuit. This invention reduces the number of switching transistors in the converter, reduces the adjustment pressure on the DC side, and decreases the size of the DC bus capacitor, thereby reducing the complexity of the converter and decreasing the possibility of prolonged operation under fault conditions.

This invention discloses a system for reducing the ripple current of a DC bus capacitor, comprising a DC bus capacitor C1, an inverter circuit, a current sampling circuit, an energy storage inductor L1, and a control circuit. This invention also discloses a method for reducing the ripple current of a DC bus capacitor. In this invention, an energy storage inductor L1 is placed between the positive terminal of the battery and the positive terminal of the DC bus capacitor C1. The control circuit controls the energy storage inductor L1 to charge or discharge to the motor according to the direction and magnitude of the current flowing through the DC bus capacitor C1, thereby reducing the charging or discharging current of the DC bus capacitor C1, and consequently reducing the ripple current of the DC bus capacitor C1. This reduces the temperature rise of the DC bus capacitor during operation, thereby extending the service life of the DC bus capacitor C1. This invention also features a simple structure, low cost, and high reliability.

The invention relates to an MMC-based multi-terminal interlaced direct current power flow controller, which comprises an MMC circuit and a control module which are connected with each other, the MMC circuit is a multi-port network and comprises a direct current bus capacitor and a converter which are connected with each other, the converter comprises converter branches of which the number is the same as that of ports, and the converter branches are connected with the control module. Each converter branch comprises an upper arm and a lower arm which are connected to the midpoint of the converter branch, the midpoint of each converter branch provides the port outwards, and each arm comprises N submodules which are in cascade connection, the control module obtains PWM pulse signals of the sub-modules through external power flow control, internal power flow control and module capacitance balance control. Compared with the prior art, power distribution control among multiple power transmission lines in the high-voltage direct-current power transmission network is realized, and the method has the advantages of higher output voltage level, stronger robustness, less alternating-current component injection in the power transmission lines and the like.

Embodiments of the present disclosure disclose Variable-frequency Drive (VFD) and motor drive system. The VFD comprising a three-level rectifier, coupled with a three-phase power supply; an even number of direct-current (DC) bus capacitors, coupled with the three-level rectifier; and a H-bridge inverter, coupled with the even number of DC bus capacitors; wherein the H-bridge inverter comprises a first bridge arm and a second bridge arm, an output midpoint of the three-level rectifier is coupled with a midpoint of the even number of DC bus capacitors, the midpoint of the even number of DC bus capacitors is coupled with a first input terminal of a three-phase motor, a midpoint of the first bridge arm is coupled with a second input terminal of the three-phase motor, and a midpoint of the second bridge arm is coupled with a third input terminal of the three-phase motor. H-bridge inverter containing two bridge arms is used to drive three-phase motor, reducing the number of power switches and saving component costs..

The invention provides a multi-level hybrid clamping type converter and a control method, the multi-level hybrid clamping type converter comprises a direct current input source, a first direct current bus capacitor, a second direct current bus capacitor and a three-phase circuit, the positive electrode of the direct current input source is electrically connected with the positive electrode of the first direct current bus capacitor, and the negative electrode of the second direct current bus capacitor is electrically connected with the three-phase circuit; the cathode of the DC input source is electrically connected with the cathode of the second DC bus capacitor. The cathode of the first direct current bus capacitor is grounded; the anode of the second DC bus capacitor is grounded; the first end of the three-phase circuit is electrically connected with the anode of the first direct-current bus capacitor, and the second end of the three-phase circuit is electrically connected with the cathode of the second direct-current bus capacitor; each phase circuit in the three-phase circuit comprises a first switch module, a second switch module, a third switch module and flying capacitors, and the flying capacitors comprise a first flying capacitor, a second flying capacitor and a third flying capacitor. The stability of the converter is improved.

The embodiment of the invention provides a DC micro-grid stability control method considering a constant power load, and relates to the technical field of power electronic equipment, and the method comprises the steps: building a state space model of a Boost DC-DC converter; constructing a linear active disturbance rejection controller; dC bus capacitor voltage is collected as a capacitor voltage measurement value; estimating the total disturbance of the system, and outputting a total disturbance observation value; the state feedback control unit executes duty ratio signal generation and output; discretization reconstruction is carried out on the linear active disturbance rejection controller, and a discretization control algorithm adaptive to the digital control chip is generated; capacitor voltage acquisition, disturbance observation value updating and duty ratio signal output are circularly completed according to a set sampling period. The technical problems that in the prior art, control parameters are generally designed and optimized based on a small signal model, large-range disturbance cannot be dealt with, the system is unstable under the large disturbance condition, and the reliability and safety of the micro-grid are seriously affected are solved.

The invention provides a string photovoltaic inverter bus capacitor on-line monitoring and life warning method and device, and the method comprises the steps: 1, controlling a discharge loop of a photovoltaic inverter system to discharge a DC bus capacitor after an inverter is shut down at night; step 2, acquiring attenuation data of bus voltage in a discharging process, and calculating an actual capacitance value of a direct-current bus capacitor through a preset fault prediction and health management algorithm according to the attenuation data; 3, comparing the actual capacitance value with a preset reference capacitance value to calculate the health degree of the direct current bus capacitor; and when the health degree is lower than a preset alarm threshold value, generating and sending out a life alarm signal. According to the method, existing hardware and night working conditions of the inverter are fully utilized, additional detection equipment does not need to be added, online and automatic monitoring and accurate service life evaluation of the bus capacitor capacitance value are achieved, and the problem that an effective online monitoring means is lacked in traditional operation and maintenance is effectively solved.

The application discloses a control method and device of a vehicle-mounted charger, a vehicle-mounted charging system and a vehicle, and relates to the technical field of vehicle-mounted charging. The control method comprises the following steps: through controlling the action of the secondary side power switch tube of the isolation type DC / DC circuit in the vehicle-mounted charger, the pre-charging process of the DC bus capacitor is realized by using the electric energy of the power battery to charge the DC bus capacitor; the soft start of the isolation type DC / DC circuit is realized by gradually increasing the duty cycle at the start time, the oscillation of the resonance current is avoided, and the smoothness of the charging voltage output to the DC bus capacitor is improved; meanwhile, the loss in the isolation type DC / DC circuit is reduced by reducing the switching frequency after the duty cycle is stable, so that the gain of the output charging voltage is improved, and the fast charging of the DC bus capacitor is realized. The whole pre-charging process is realized by reusing the isolation type DC / DC circuit in the vehicle-mounted charger, no additional hardware is needed, and the application cost of the vehicle-mounted charger is effectively saved.

The invention provides a three-level neutral-point-clamped bridge arm switch unit integrated structure, and relates to the technical field of multi-level bridge arm circuits. The circuit comprises a bottom copper-clad ceramic substrate, a top copper-clad ceramic substrate and a printed circuit board, the bottom copper-clad ceramic substrate bears half of the three-level bridge arm circuit, and the top copper-clad ceramic substrate bears the other half of the three-level bridge arm circuit; the printed circuit board bears a direct current bus capacitor and is electrically connected with the bottom copper-clad ceramic substrate and the top copper-clad ceramic substrate. Compared with a discrete component or a single-sided power module, the integrated structure provided by the invention has the advantages that the lead area is shortened, the occupied total area is smaller, and the magnetic field / inductance parameter induced by the circuit is lower, so that the parasitic inductance of the commutation loop is reduced by virtue of the extremely small integrated area and the commutation loop structure, and the safety of the three-level converter is further improved.

The present invention discloses an internal loop balancing control method suitable for a modular energy storage system. The control method implements balancing based on the DC part of the energy storage system composed of multiple half-bridge converter sub-modules connected in series. By leveraging the characteristic that the DC bus voltage of the energy storage system can be arbitrarily adjusted when idle, the balancing energy is alternately transferred between the battery group to be discharged and the DC bus capacitor, and between the DC bus capacitor and the battery group to be charged, thereby achieving indirect balancing between the battery group to be discharged and the battery group to be charged. The balancing method proposed in the present invention can also be used in other modular energy storage systems, and balancing can be achieved without the help of additional balancing circuit hardware.

The application belongs to the technical field of power electronic converter control, and discloses a control method of a grid-connected double-fed asynchronous wind power generation system with power control capability, which comprises a control process of a rotor-side converter and a control process of a grid-side converter, wherein the rotor-side converter forms a grid-connected characteristic at the motor stator winding port and controls the energy injected into the DC bus capacitor; the grid-side converter maintains the input and output energy balance of the DC bus capacitor, thereby controlling the DC bus capacitor voltage to be constant; the control process of the rotor-side converter comprises a frequency support control loop, a power control loop, a voltage and current inner loop and pulse width modulation control, and the control process of the grid-side converter comprises a DC voltage control loop, a reactive power control loop, an AC current control loop and pulse width modulation control. The application can realize the grid-connected power dynamic index and provide the output power control capability.

The application provides a DC voltage transient stability control method of a network-constructed photovoltaic inverter, comprising the following steps: calculating surplus energy of a DC bus capacitor according to a real-time detection value and a set value of the DC voltage, dividing the surplus energy of the capacitor by a time of expected regulation of the capacitor voltage to obtain compensation power of a grid-connected converter, and updating an instruction value of active power of the grid-connected converter by using the compensation power, so as to realize power control of the grid-connected converter and control of the capacitor voltage; during a transient fault, a deviation between an actual value and an instruction value of the DC voltage is controlled by a non-linear gain regulator and superimposed on a phase angle of a modulation voltage of the grid-connected converter, so that the DC side voltage of the grid-connected converter is always controlled within a set boundary range, and transient stability control of the DC voltage is realized. When the inverter works in a maximum power tracking mode or a limited power control mode, the application can realize stable control of the DC side voltage.