232 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 invention provides a battery energy storage parallel equalization converter topology and a control method therefor. The battery energy storage parallel equalization converter topology comprises a series-connected battery energy storage parallel equalization converter, a main converter, and a plurality of groups of filter inductors; in the main converter, the input side of a DC / DC or DC / AC converter is connected in parallel to a parallel voltage-stabilizing capacitor, and the output side of the DC / AC or DC / AC converter is correspondingly connected to an AC or DC source load; the series-connected battery energy storage parallel equalization converter comprises a plurality of groups of small-capacity DC / DC converters and a common DC bus capacitor; the output sides of all the small-capacity DC / DC converters are connected in parallel by means of the common DC bus capacitor to form a common DC bus; the input side of one group of small-capacity DC / DC converters is connected in series to the input side of the main converter, and the input sides of other groups of small-capacity DC / DC converters are connected in series to a battery pack by means of the filter inductors, respectively. According to the present invention, in a battery charging and discharging process, only a small amount of power flows through the converter, reducing the capacity requirements of the converter, and reducing the transmission efficiency.

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 discloses a general network-side converter network construction control method and system, and relates to the technical field of grid-connected inverter control, and the method comprises the steps: collecting the data of a network-side converter, and carrying out the preprocessing; calculating the power angle of the output internal potential based on the preprocessed data; calculating the amplitude of the output internal potential based on the preprocessed data; and obtaining an internal potential vector based on the power angle and amplitude of the internal potential. According to the invention, the DC bus capacitor is directly used as an energy buffer element in the power grid synchronization process, and a simpler and more direct mathematical relation between DC voltage change and internal potential is established, so that the complexity of a control system is reduced, and the stability is easier to control. According to the converter self-synchronization control, when transient power imbalance disturbance occurs in the system, the angle, the frequency and the amplitude of the internal potential can be maintained not to suddenly change, so that the system is transited to a stable state as soon as possible, and the power grid range influenced by faults is narrowed.

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 belongs to the technical field of power electronic converter control, and discloses a control method of a grid-forming type doubly-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, and is characterized in that the rotor-side converter forms a grid-forming type characteristic at a motor stator winding port, and the grid-side converter forms a grid-forming type characteristic at a motor stator winding port; the energy injected into the direct current bus capacitor is controlled; the grid-side converter maintains the input and output energy balance of the DC bus capacitor so as to control the voltage of the DC bus capacitor 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 direct current voltage control loop, a reactive power control loop, an alternating current control loop and pulse width modulation control. According to the invention, the capability of controlling the output power can be provided while the network construction type power dynamic index is realized.

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 belongs to the field of power electronics, relates to the technical field of inverter design, and provides a silicon carbide MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor)-based high-switching-frequency inverter which comprises a parallel S C inverter, a direct-current bus capacitor and a DSP (Digital Signal Processor) controller. The parallel Si C inverter comprises a plurality of parallel bidirectional bridge arm inverters, and the output end of each bidirectional bridge arm inverter is connected with a Hall sensor CT. And one end of the direct current bus capacitor is connected with the positive terminal of the parallel Si C inverter, and the other end of the direct current bus capacitor is connected with the negative terminal of the parallel Si C inverter. The DSP controller comprises a plurality of driving circuits, a current sampling circuit and a PWM control signal conversion circuit. According to the inverter, under the condition that the power frequency of the inverter is ensured and the quality of the output waveform is not influenced, the volume and the weight of the filter inductor and the filter capacitor are greatly reduced, and the requirement of product weight limitation is met.

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 invention discloses a photovoltaic power generation system, and belongs to the technical field of power generation. The system comprises an inverter circuit, an alternating-current starting circuit and a control unit, the alternating-current starting circuit comprises an alternating-current starting switch, an isolation module and a charging module which are sequentially connected from a power grid side, and the control unit is connected with the inverter circuit and the alternating-current starting switch. The control unit is used for controlling the alternating-current starting switch to be closed and transmitting electric energy of a power grid through the isolation module when the direct-current voltage of the input end of the inverter circuit is lower than the sum of the power grid line voltage peak-to-peak value and a threshold value and an alternating-current starting instruction is received, and the charging module carries out current limiting and rectifying processing on alternating-current electric energy output by the isolation module. The direct-current bus capacitor is charged by alternating positive and negative half waves of alternating current; and the control unit is also used for controlling the alternating current starting switch to be switched off and starting the inverter circuit under the condition that the direct current bus capacitor is charged to the target voltage required by grid connection. The system can be safely and reliably started when no sunlight exists at night.

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 invention discloses an overvoltage protection method and device, electronic equipment and a medium, and relates to the field of new energy, and the method comprises the steps: determining a PWM (Pulse Width Modulation) wave sealing value of any IGBT (Insulated Gate Bipolar Translator) in a rotor side converter and a power grid side converter in a wind turbine generator, and determining a first overvoltage fault protection value of a DC bus capacitor corresponding to the converter according to the PWM wave sealing value; the first overvoltage fault protection value must be larger than the PWM wave sealing value, when the current voltage value of the direct current bus capacitor is larger than the PWM wave sealing value, all IGBTs need to be controlled to be turned off, whether the current voltage value is larger than the first overvoltage fault protection value or not is judged, and if the current voltage value is larger than the first overvoltage fault protection value, it is judged that the direct current bus capacitor has an overvoltage fault; and controlling the wind turbine generator to break away from the power grid. According to the scheme, the wind turbine generator is controlled to be separated from the power grid only when the DC bus voltage is greater than the first overvoltage fault protection value, the probability that the wind turbine generator is separated from the power grid is greatly reduced, and the stability of the power grid is improved.

The invention discloses a seven-level inverter topology and a control method thereof, and relates to the technical field of multi-level structures, the topology comprises an upper bridge arm and a lower bridge arm which are mutually symmetrical except the diode direction, and a plurality of switch tubes, a direct current bus capacitor and a flying capacitor of the topology 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.

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.

The utility model relates to a three-power three-phase efficient elevator energy recovery multi-level converter, which comprises a first direct-current voltage source, a second direct-current voltage source, a third direct-current voltage source, a first direct-current bus capacitor, a second direct-current bus capacitor and a third direct-current bus capacitor, the first DC voltage source is connected in parallel with a first DC bus capacitor, the second DC voltage source is connected in parallel with a second DC bus capacitor, the third DC voltage source is connected in parallel with a third DC bus capacitor, the anode end of the first DC voltage source is connected with the DC bus anode P end, and the cathode end of the third DC voltage source is connected with the DC bus cathode N end; the direct-current bus positive pole P end and the direct-current bus negative pole N end are connected with the input ends of the A-phase converter, the B-phase converter and the C-phase converter respectively, and the output ends of the A-phase converter, the B-phase converter and the C-phase converter are connected with the traction motor. The efficiency of the elevator energy recovery converter can be effectively improved, and consumption reduction and energy conservation are achieved.

The present application provides a pre-charge circuit, which relates to the field of power electronics technology. The pre-charge circuit includes: a pre-charge control circuit, an electromagnetic interference module, a three-phase power supply module, and a bus capacitor module; when pre-charging the bus capacitor module, the first main relay, the second main relay, the first AC pre-charge module, and the second AC pre-charge module are disconnected, and the first DC pre-charge module is turned on; or, the first main relay is disconnected, the second main relay is disconnected, and the second DC pre-charge module is turned on; when pre-charging the electromagnetic interference module, the first AC pre-charge module is turned on, and the first DC pre-charge module is disconnected; or the second DC pre-charge module is disconnected. After the electromagnetic interference module is pre-charged, the first main relay and the second main relay are turned on. The present application effectively decouples the pre-charging of the AC capacitor and the pre-charging of the DC bus capacitor from the circuit by separating the pre-charge paths and controlling the on / off of different relays to connect the corresponding pre-charge circuits.

The present invention relates to a method for analyzing resonance in a wind power grid-connected system. By establishing an impedance model of a direct-drive wind turbine, the resonance problem of the wind power grid-connected system is analyzed, considering the influence law of the DC bus capacitor on the impedance model of the direct-drive wind turbine under the condition of power disturbance on the AC side. In addition, in the process of establishing the impedance model of the direct-drive wind turbine, the harmonic state space theory is used to perform a steady-state processing on the linearized single-phase analytical model. The harmonic state space method can represent multiple frequency responses in each variable at the same time, so as to establish an impedance model of the direct-drive wind turbine with a multi-dimensional harmonic transfer function, which can accurately reflect the influence of the DC bus capacitor or asymmetric control on the impedance characteristics of the direct-drive wind turbine; using this impedance model of the direct-drive wind turbine to analyze the resonance problem of the wind power grid-connected system, since it comprehensively reflects the influence mechanism of the DC bus capacitor on the frequency coupling characteristics of the system, the accuracy of resonance analysis of the wind power grid-connected system can be improved.

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 invention discloses power supply equipment, and belongs to the technical field of power supply equipment. According to the power supply equipment, one end of a first charging circuit is connected with a direct-current bus capacitor, the other end of the first charging circuit is used for being connected with a power grid, and a control unit is used for controlling the first charging circuit to charge voltage of the direct-current bus capacitor to first target voltage in a first pre-charging stage. The first charging circuit is controlled to charge the voltage of the direct current bus capacitor to a second target voltage in a second pre-charging stage, the first pre-charging stage is before the second pre-charging stage, the first target voltage is smaller than the second target voltage, and the second target voltage is larger than the voltage of the power grid; and the control unit is also used for controlling the power conversion circuit to perform inversion output under the condition that the voltage of the direct current bus capacitor reaches the second target voltage so as to start the power supply equipment. According to the power supply equipment, the bus capacitor voltage can be effectively increased, the risk of insufficient inverter voltage in the inverter phase-locked grid connection process is effectively reduced, and safe and reliable alternating current pre-charging starting of the power supply equipment is achieved.

The invention discloses an NPC type converter common-mode voltage suppression method with active midpoint potential control, which adopts an improved virtual space vector pulse width modulation method to redefine a small vector and a middle vector, so that the maximum value of common-mode voltage generated by an obtained virtual voltage vector is Vdc / 6, and the maximum value of the common-mode voltage generated by the virtual voltage vector is Vdc / 6. Compared with a traditional virtual vector pulse width modulation method, the common-mode voltage value of Vdc / 3 is reduced by half, and therefore the suppression effect on the common-mode voltage is achieved. On the basis, the value of a virtual vector distribution coefficient k is reasonably selected, the problem of neutral-point potential imbalance caused by accumulation of neutral-point potential offset due to the initial voltage difference of upper and lower capacitors of the direct-current bus and the active current component effect is solved, the fluctuation of the neutral-point voltage is actively inhibited, and the neutral-point voltage balancing effect is improved. And the correctness and the effectiveness of the method are verified through an MATLAB / Simulink simulation test.

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.

A bipolar discharge circuit (1) for an induction cooking zone (Z) to heat and detect cookware (W), comprising a line mains terminal (T1) for connection to a mains line (L) of a mains AC source (2) and a neutral mains terminal (T2) for connection to a mains neutral (N) of the mains AC source (2); a rectifier (3) connected to the line mains terminal (T1) and the neutral mains terminal (T2); and a DC bus capacitor (6) connected to the rectifier (3). The DC bus capacitor (6) comprises a positive capacitor terminal (H1) and the negative capacitor terminal (H2) for connection to the induction cooking zone (Z). A switching circuit (9) is provided and configured to discharge the DC bus capacitor (6) via the line mains terminal (T1) and the neutral mains terminal (T2).

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.