1434 results about "Capacitance voltage" patented technology

The invention provides a phase jump compensation method and device of a network-forming converter, a terminal and a medium. The method comprises the following steps: calculating an instantaneous power angle compensation amount based on the voltage of a grid-connected point of the grid-forming converter; if the instantaneous power angle compensation amount is greater than a preset threshold value, determining a weighted full feed-forward compensation amount based on a capacitor voltage of the network-constructing converter, and determining a cross decoupling compensation amount based on a bridge arm current of the network-constructing converter; and adding the instantaneous power angle compensation amount, the weighted feed-forward compensation amount and the cross decoupling compensation amount into a voltage control loop of the network-forming converter to obtain a control signal added with phase jump compensation. According to the method, the influence of internal virtual inertia on the output response of the grid-forming converter can be reduced, the change of the power grid is quickly responded, the power grid adaptability of the grid-forming converter is improved, the power grid adaptability comprises the phase angle jump adaptability and the power grid strength SCR adaptability, and an overcurrent fault during phase jump is avoided.

The invention relates to a power electronics and energy storage technology, and aims to provide a medium-voltage uninterruptible power supply system based on cascade super-capacitance energy storage and a control method. According to the system, a cascade super-capacitance energy storage module with a three-phase structure is connected between an isolation reactor and a load side switch through a filter reactor and is used for stabilizing the voltage of a load bus; according to the invention, operations of adaptive power reference calculation, voltage phase control and voltage amplitude stable control are carried out; according to the method, the over-capacitance wide voltage operation characteristic is fully considered, and the control on the over-capacitance charging and discharging process is adaptively adjusted according to the power grid fault state and the over-capacitance voltage deviation, so that the system can provide the required power support when the fault occurs, stable energy supplementation is performed after recovery, the risks of over-capacitance voltage out-of-limit and the like are favorably avoided, and the system reliability is improved. And the effectiveness of energy management and the stability of the system are improved. And during a power grid fault period, the load voltage is recovered to be close to a rated value in a short time, voltage drop and overshoot are reduced, and the response speed and the voltage supporting capability of the system are enhanced.

The invention belongs to the field of power electronic power conversion, and provides a coupling type three-level inverter direct current side capacitance current ripple suppression method and system, and the method comprises the steps: determining a coupling type three-level inverter space vector diagram region division method according to a virtual voltage vector duty ratio distribution factor value range; according to the amplitude, the phase angle and the three-phase output current of the reference voltage vector, the sector and the area where the reference voltage vector is located are judged; according to the sector and the area where the reference voltage vector is located, selecting a virtual voltage vector and two basic voltage vectors which are closest to each other, and respectively calculating duty ratios of the virtual voltage vector and the two basic voltage vectors; designing a controller based on a dead-beat control method according to a sector and an area where a reference voltage vector is located, a direct-current side capacitor voltage deviation given value and a direct-current side capacitor voltage deviation actual value, and updating a small vector duty ratio distribution factor to realize independent control of capacitor voltage; and designing a switch sequence based on the updated small vector duty ratio and the sector and the area where the reference voltage vector is located.

According to the SiC MOSFET global short circuit and overcurrent protection circuit and the control method thereof provided by the invention, when a short circuit fault occurs in the SiC MOSFET, the drain current ID is more than several times of the rated current of the SiC MOSFET. When a short circuit occurs, a transistor QDZ of the short circuit detection circuit is switched on by node voltage Vr of the resistance-capacitance filter circuit, a fault signal VFAULT is converted into a low level, grid voltage VGS output by the grid control unit is gradually converted into zero voltage from negative driving voltage VEE, and soft turn-off is performed on the SiC MOSFET; when an over-current fault occurs in the SiC MOSFET, drain current ID is higher than rated current, node voltage Vo of the resistance-capacitance filter circuit lasts for a long time, the maximum value of capacitor voltage Vch of the over-current detection circuit is higher than reference voltage Vref2, a fault signal VFAULT is converted into low level, grid voltage VGS output by the grid control unit is gradually converted into zero voltage from negative driving voltage VEE, and soft turn-off is performed on the SiC MOSFET. According to the invention, high-speed short circuit and over-current fault protection of the SiC MOSFET in all inductance regions of a commutation loop can be realized.

The invention discloses a cascaded SVG-based grid-connected system high-frequency oscillation suppression method and system in a weak network state. The method comprises the following steps: generating a preliminary modulation current component by using a capacitor voltage signal of an SVG device; enabling a voltage signal of a grid-connected point to pass through a fundamental frequency wave trap, obtaining an oscillation voltage component of a grid side except a fundamental frequency, and generating a high-frequency oscillation suppression current component based on the oscillation voltage component; generating a reactive current component compensation component based on the grid-connected point voltage signal, the cascade SVG device output current signal and the grid-side current signal; adding the preliminary modulation current component, the high-frequency oscillation suppression current component and the reactive current component compensation component to obtain a cascade SVG compensation current reference value, making a difference between the cascade SVG compensation current reference value and an output current signal of the cascade SVG device, enabling the difference to pass through a current regulator, and enabling the output of the current regulator to be subjected to power grid voltage feedforward control to obtain a compensation current signal of the cascade SVG device. And the cascaded SVG bridge arm modulation voltage is obtained. According to the invention, high-efficiency grid-side reactive power control is realized, and grid-side high-frequency oscillation is suppressed at the same time.

The invention relates to the technical field of unit power failure detection, in particular to an AC power supply input power failure detection method and system. The AC power supply input power failure detection method comprises the following steps: comparing a characteristic voltage value with a preset threshold value; triggering a sampling frequency adjustment mechanism according to the preliminary detection signal, increasing the sampling rate according to the voltage fluctuation frequency by adopting an adaptive algorithm, and obtaining high-precision sampling data through real-time calculation; for the optimized power consumption control scheme, acquiring current system state data, coordinating quick response capability and low power consumption optimization through a state machine algorithm, and outputting a multi-stage interaction strategy signal; adjusting a dynamic threshold value of capacitance voltage division design according to the multi-stage interaction strategy signal, and predicting voltage fluctuation by adopting a Kalman filtering algorithm to obtain smoothed detection sensitivity data; and analyzing the misjudgment rate reduction degree through a threshold fine tuning algorithm in combination with the abnormal fluctuation characteristics and the partial pressure state, and outputting a final power failure detection result.

The invention discloses an intelligent self-adaptive suppression method for oscillation of a data-driven SVG (static var generator) grid-connected system. Obtaining the capacitor voltage of the direct current side of the SVG and the actual voltage and the actual current of the grid connection point of the SVG, and respectively calculating the active power output by the SVG and the voltage amplitude output by the SVG according to the actual voltage and the actual current; a current reference value is generated through a voltage outer loop; the active power output by the SVG, the voltage amplitude output by the SVG and the voltage of the direct current side of the SVG are input into a DeePC controller to be processed, and an additional current reference value is obtained; and then the current error is obtained by adding the current reference value output by the voltage outer loop and subtracting the actual current, and then the current error is input to the voltage inner loop for processing to obtain a modulation wave voltage amplitude signal. According to the method, the oscillation of the converter grid-connected system can be suppressed under the condition that the dynamic characteristics of the converter and the conditions of the power grid are changed, and the problems of insufficient fixed structure and parameter sensitivity of the traditional SVG are solved.

The invention relates to the technical field of inverter pulse width modulation, in particular to a neutral-point potential balance and low common-mode voltage modulation method and system based on an SVPWM inverter, and the method comprises the steps: determining a basic voltage vector based on different switching states of an NPC three-level inverter; respectively determining the midpoint current of each fundamental voltage vector, and determining the fundamental voltage vector causing midpoint potential deviation; combining with a large vector and a zero vector, and performing mode division of a single vector space region; determining an expected current according to the DC side capacitor voltage of the inverter, and constructing a target function based on the expected current; and performing region judgment according to the output synthesized voltage vector, determining a corresponding optimal division mode, obtaining each basic voltage vector of the synthesized voltage vector and a corresponding duty ratio, and determining a switching sequence to obtain a PWM wave. While the neutral-point potential balance and common-mode voltage suppression of the NPC three-level inverter are realized, the switching frequency of the inverter is effectively reduced, and the switching loss is reduced.

The invention discloses a current coordinated distribution and voltage optimization control method of a multi-network converter considering nonlinearity and negative sequence load. The method comprises the following steps: carrying out harmonic separation on three-phase load side current and three-phase capacitor voltage through feedforward compensation to obtain a fundamental wave positive sequence component, a fundamental wave negative sequence component and an h-order harmonic component; fundamental wave positive sequence active and reactive power are solved, and angular frequency and output voltage are respectively obtained through an active frequency regulator and a reactive voltage regulator; virtual impedance of a fundamental wave positive sequence, a fundamental wave negative sequence and a harmonic component is set, a multi-frequency-point virtual impedance voltage drop instruction is calculated, and a voltage reference instruction value is obtained by subtracting the multi-frequency-point virtual impedance voltage drop instruction value from the output voltage of the constructed network type converter; calculating a three-phase modulation wave signal based on the voltage reference instruction value, the capacitor voltage, the load side current, the inductor current and the DC voltage; and calculating a pulse signal of the switching device based on the three-phase modulated wave signal. The virtual impedance of the networking converter is set to be a negative value, the harmonic voltage drop on a common coupling point can be reduced, the sum of the virtual impedance and the actual impedance is adjusted to be a certain proportion, and the harmonic current of each order of the multi-networking converter can be distributed according to the proportion.

The present invention provides a method for cooperatively suppressing a common-mode voltage and current harmonics of coupled three-level inverters, comprising: based on amplitude and phase angle of reference voltage vector, determining sector and region in which the reference voltage vector is located; selecting four basic voltage vectors with low common-mode voltage amplitudes to synthesize the reference voltage vector; writing volt-second balance equation based on selected basic voltage vectors, and calculating duty cycles thereof; and based on sector and region in which reference voltage vector is located, set value of voltage difference across capacitors on direct current side, and actual value of voltage difference across capacitors on direct current side, (1) updating duty cycles of basic voltage vectors, to realize separate control of capacitor voltage; and (2) designing and converting switching sequence into PWM drive signal of power switch, to control the coupled three-level inverter to operate.

The invention relates to a power electronic technology, and aims to provide a network construction type SVG control method suitable for multiple power grid strengths. Comprising the following steps: obtaining a power grid angular frequency based on a phase-locked loop principle, and obtaining an internal frequency of SVG equipment based on capacitor voltage-frequency droop control; multiplying the two angular frequency values by respective corresponding power grid intensity adaptation parameters to obtain a phase-locked loop reference angular frequency and a droop reference angular frequency, and performing integral calculation on the phase-locked loop reference angular frequency and the droop reference angular frequency and a power grid nominal angular frequency to obtain a phase angle; and finally, a switching signal is generated in an SVG control link, so that control of SVG equipment is realized. According to the method, a more stable reference power grid phase angle is obtained, the broadband oscillation instability condition possibly occurring under a strong power grid can be suppressed, the network-forming SVG can work under different power grid intensities, and the operation stability is improved; the method can enhance the power grid synchronization stability of the network construction type control under the strong power grid, and is suitable for different system conditions.

The invention discloses an MMC sub-module fault processing method, device and equipment and a storage medium, and the method comprises the steps: obtaining the capacitor voltage value of a sub-module of an MMC and the bridge arm current value of the sub-module, the MMC comprises six bridge arms of three phases, each bridge arm comprises a plurality of sub-modules, the capacitor of each sub-module is connected with an equivalent series resistor in series, and further, the equivalent series resistor is connected with the capacitor voltage value of the sub-module of the MMC; the resistance value of an equivalent series resistor in the sub-module is monitored through the capacitor voltage value and the bridge arm current value, if the resistance value of the equivalent series resistor is higher than a preset resistance value, it is determined that the capacitor of the sub-module fails, fault-tolerant control is carried out on the sub-module through a voltage-sharing and circulating current suppression algorithm, a three-phase switching signal is output, and the three-phase switching signal acts on the MMC. Therefore, the circulating current fundamental frequency component and the double frequency component caused by fault-tolerant control after the fault can be eliminated through the circulating current suppression strategy, the effect of circulating current suppression is achieved, and the stability of system fault operation is improved.

The invention relates to the technical field of MMC sub-module balance control, and discloses a capacitor voltage balance control method and system for an MMC sub-module, and an MMC, and the method comprises the steps: judging whether a bridge arm is in a near-zero current risk region or not according to the direction of the current of the bridge arm in each valve control period; if the bridge arm is not in the near-zero current risk area, judging whether the bridge arm is in a modulating wave extreme value risk area or not according to the bridge arm modulation voltage instruction; if the bridge arm is in a near-zero current risk area or a modulating wave extreme value risk area, a first switching strategy is adopted; and if the bridge arm is not in the modulating wave extreme value risk area, a second switching strategy is adopted. According to the invention, the switching frequency is effectively reduced and the narrow pulse phenomenon of the sub-module is eliminated through the judgment of the frequent switching risk area and the corresponding switching strategy, meanwhile, the module alternation probability is effectively reduced through the sorting switching strategy based on the dynamic additional factor, and the fluctuation range of the module voltage is limited within the required range, so that the switching efficiency is improved. And the operation safety and stability of the MMC are ensured.

An energy self-balancing flexible direct-current converter valve, a control method, and a direct-current system, which relate to the technical field of power transmission and distribution networks. The converter valve comprises three phase units, and each phase unit comprises an upper leg and a lower leg. The upper legs and the lower legs each comprise a plurality of full-bridge energy self-balancing submodules and a plurality of half-bridge energy self-balancing submodules. Each of the full / half-bridge energy self-balancing submodules is an optimized MMC submodule comprising an energy self-balancing circuit. The energy self-balancing circuit is composed of a power electronic switch and an energy dissipation resistor connected in series, and is used for dissipating surplus energy when an overvoltage early warning occurs for the capacitor voltage of the submodule. The present application, without affecting the operational logic of conventional converter valves and at low costs, can solve the technical problem of surplus power not being dissipated promptly due to faults occurring in a direct-current power transmission system in a new energy islanded ultra-long-distance direct-current delivery scenario. Meanwhile, temporary energy stored in the capacitors of the optimized MMC submodules can be fully utilized, reducing the waste generated by surplus power dissipated as heat.

The invention discloses a construction method and a modulation method of a three-port multi-frequency MMC topology based on bridge arm multiplexing, and relates to the technical field of power electronics. The construction method comprises the steps that sub-modules of a traditional double-bridge-arm MMC are integrated and optimized into a three-bridge-arm structure through a current conversion branch, independent energy interaction of three ports is achieved through an auxiliary bridge arm, multi-frequency operation modes of power frequency, frequency division, direct current and the like are supported at the same time, and therefore the utilization rate of the bridge arm sub-modules is increased, and the energy utilization rate of the MMC is increased. And the overall size and the manufacturing cost of the converter are reduced. Based on three-port multi-frequency coordination control and power balance requirements, a modulation method of the topological structure is provided, a multi-frequency coordination modulation strategy is adopted, frequency offset is performed through an auxiliary bridge arm to reduce cross interference of port frequency, and output waveform quality is improved through multi-objective optimized capacitor voltage balance control. And meanwhile, direct-current side faults are effectively eliminated by means of the auxiliary bridge arm.

The invention discloses an ISOP type medium-voltage DC converter LLC module fault diagnosis method and device, a medium-voltage DC power supply system and a storage medium. Comprising the following steps: monitoring an input capacitor voltage, an input current, an output voltage and an output current of each LLC module port; according to the output voltage and the output current, judging whether a fault condition of the ISOP type medium-voltage direct-current converter is met or not; under the condition that it is judged that the fault condition is met, the difference between the input capacitor voltage change rate, the input voltage amplitude and the input current amplitude of each LLC module is calculated; according to the input capacitor voltage change rate, the input voltage amplitude and the input current amplitude, the LLC module with the switch tube open-circuit fault or the input capacitor aging fault in all the LLC modules is judged. According to the scheme of the invention, the online detection and positioning of the fault LLC module are completed by using the difference between the electrical quantity amplitudes and the change rates of the LLC modules, and the phenomenon of misdiagnosis caused by large input voltage fluctuation is avoided.

The invention discloses a particle swarm and non-linear programming hybrid optimization VSG adaptive control method and system, and relates to the technical field of virtual synchronous generator control, and the method comprises the steps: collecting a filter inductor current and capacitor voltage signal, outputting an instantaneous active power and a reactive power, constructing a small signal dynamic model of a VSG, and building a parameter mapping relation; setting a constraint range based on the parameter mapping relation in combination with a second-order oscillation modal stability criterion of the power system; constructing a hybrid optimization algorithm according to the constraint range, and outputting steady-state data; constructing a two-dimensional threshold criterion system, and cooperatively generating a voltage reference value through a speed regulator and a controller; the voltage reference value is compared with the actual output voltage, and the inverter output is driven through PI control and PWM modulation. The method has the beneficial effects that the parameter optimization precision is improved, the stability of the system is guaranteed, and the calculation efficiency of the algorithm is improved.

The invention provides an MMC multi-tube open-circuit fault rapid diagnosis method and system, and relates to the technical field of open-circuit fault diagnosis, and the specific scheme comprises the steps: obtaining the operation data of a to-be-diagnosed MMC, including a capacitor voltage, an MMC DC side voltage, a power grid voltage, a power grid current, a power grid resistance, an MMC bridge arm inductance, a power grid inductance and a control signal; calculating expected values of common-mode and differential-mode voltages of the MMC bridge arm based on the operation data, subtracting the expected values from corresponding actual values to obtain a bridge arm voltage residual error, judging whether the bridge arm has a fault by using the bridge arm voltage residual error, and calculating the number of fault sub-modules in the fault bridge arm; calculating an expected value of the capacitive current of the sub-module in the fault bridge arm, subtracting the expected value from a corresponding actual value to obtain a capacitive current residual error of the sub-module, and positioning the fault sub-module by using the capacitive current residual error; according to the invention, fault diagnosis is carried out by using mismatching between an actual value and an expected value without increasing cost investment; the diagnosis speed and the accuracy are high.

The invention discloses a SiC MMC sub-module capacitor voltage fluctuation suppression method and system, and belongs to the technical field of electronic power. According to the analysis result of the optimal broadband harmonic circulation injection boundary and number of times of the SiC MMC sub-module, a sub-module capacitor voltage fluctuation optimization model for simultaneously injecting second, fourth and eighth harmonic circulation and third harmonic voltage is determined, and the characteristic of higher control bandwidth of the SiC MMC can be fully utilized; by solving a submodule capacitor voltage fluctuation optimization model, the amplitudes and phases of reference values of second, fourth and eighth harmonic circulation needing to be injected and the amplitude and phase of corresponding third harmonic voltage are determined, then the second, fourth and eighth harmonic circulation is injected, and the third harmonic voltage injection is combined to realize broadband harmonic combined injection. The capacitance voltage fluctuation of the sub-module is reduced, the capacitance voltage fluctuation suppression method for the SiC MMC sub-module is realized, and the suppression effect is relatively high.

The invention relates to the technical field of modular multilevel converters, and provides an MMC fault diagnosis method, system and device based on a sorting voltage-sharing algorithm. Comprising the steps that according to measurement data of the modular multilevel converter, a theoretical value and an actual value of bridge arm voltage of the modular multilevel converter are obtained through calculation, the theoretical value and the actual value are compared with a first alarm threshold value, and a corresponding bridge arm fault and a fault type are determined; calculating the number of fault sub-modules according to the bridge arm voltage actual value and the bridge arm voltage theoretical value; judging the switching number of the fault bridge arm sub-modules, and controlling and adjusting the bridge arm sub-modules to be switched on according to the fault type and the number of the fault sub-modules; and calculating a capacitor voltage minimum difference value, comparing the capacitor voltage minimum difference value with a second alarm threshold value, and determining a fault sub-module. According to the multi-tube fault diagnosis method, the problem that the fault positioning performance is poor under the light load working condition is solved, and the sub-module positioning performance in the full power range is improved.

The invention relates to the technical field of energy storage system grid-connected control, and particularly discloses a two-stage coupling type battery energy storage grid-connected converter model prediction control method and device, and the method comprises the following steps: S1, constructing a two-stage coupling type battery energy storage grid-connected converter single-machine two-order composite model; s2, according to the single-machine dual-order composite model, constructing a prediction equation of the output current and the capacitor voltage of the inverter; s3, constructing a unified cost function of the output current and the capacitor voltage of the inverter; s4, predicting the switch state combination of all the switch tubes, and calculating the value of a corresponding unified cost function; and S5, selecting the switch state combination with the minimum uniform cost function value as the optimal switch state of all the switch tubes, and carrying out on-off control on the switch tubes. According to the invention, through unified modeling and control optimization, the dynamic response capability and the voltage stabilization performance of the energy storage grid-connected converter are improved.

Disclosed in the present invention is a state of charge (SOC) balancing method for an energy storage MMC based on capacitor voltage correction, comprising the following steps: acquiring important parameters such as the SOCs of energy storage units and current directions of bridge arms in an energy storage MMC; calculating SOC average values of phase units, of the bridge arms, and of three phases of energy storage units; calculating the inter-phase SOC imbalance degree, the inter-bridge arm SOC imbalance degree, and the inter-submodule SOC imbalance degree, obtaining an inter-phase power deviation, an inter-bridge arm power deviation, and an inter-submodule voltage deviation by means of a proportional controller, and calculating a submodule energy storage power reference value and submodule corrected capacitor voltages; calculating the duty cycle of a switching device in a bidirectional DC / DC converter; and sorting the submodule corrected capacitor voltages, and on the basis of the charging / discharging state of submodule capacitors, determining submodules to be connected. The present invention can realize SOC balancing of energy storage MMCs, and reduces the number of bidirectional DC / DC converter controllers, thereby improving the SOC balancing efficiency and the capacity utilization rate of energy storage units.

This invention discloses a method and system for suppressing capacitor voltage fluctuations in SiC MMC submodules, belonging to the field of electronic power technology. Based on the analysis results of the optimal broadband harmonic circulating current injection boundary and order for SiC MMC submodules, an optimized model for submodule capacitor voltage fluctuations is determined that simultaneously injects 2nd, 4th, and 8th harmonic circulating currents and 3rd harmonic voltages, which can fully utilize the higher control bandwidth characteristic of SiC MMC. By solving the optimized model for submodule capacitor voltage fluctuations, the amplitude and phase of the reference values ​​of the 2nd, 4th, and 8th harmonic circulating currents to be injected, as well as the amplitude and phase of the corresponding 3rd harmonic voltage, are determined. Then, by injecting 2nd, 4th, and 8th harmonic circulating currents and jointly injecting the 3rd harmonic voltage, broadband harmonic joint injection is achieved, reducing the capacitor voltage fluctuations of the submodule and realizing a method for suppressing capacitor voltage fluctuations in SiC MMC submodules with high suppression effect.

The invention is suitable for the technical field of resonant converters, and provides a starting control circuit and a resonant converter. The starting control circuit comprises a feedback module, a comparison selection module and a logical operation module, the comparison selection module is electrically connected with the feedback module and the logical operation module, the feedback module is used for being electrically connected with the output end of a resonant conversion circuit in the resonant converter, and the logical operation module is used for being electrically connected with a driving circuit in the resonant converter. According to the starting control circuit provided by the embodiment of the invention, the resonant capacitor voltage constraint threshold value which is gradually enlarged along with the starting process can be constructed, smooth establishment of resonant capacitor direct current bias is realized, the fluctuation amplitude of the resonant capacitor voltage is limited, the problem that the total bus voltage is applied to the resonant inductor in a traditional scheme is avoided, and the starting control circuit is suitable for a high-voltage power supply. Finally, the resonance current peak value in the starting stage is effectively suppressed, and the impact of current stress on core devices such as a switching tube and a resonance inductor is reduced.

The invention relates to the technical field of power electronic conversion and control, in particular to a control method of a three-level three-phase four-leg inverter and electronic equipment. The method comprises the following steps: acquiring a multi-phase first capacitor voltage and a multi-phase first inductor current; acquiring a second inductive current corresponding to a second bridge arm; determining a plurality of first modulation waves corresponding to the multi-phase first bridge arm according to the multi-phase first capacitor voltage and the multi-phase first inductor current; acquiring a positive half bus voltage and a negative half bus voltage; determining a plurality of first driving signal groups corresponding to the plurality of first modulation waves according to the positive half bus voltage and the negative half bus voltage; determining a second driving signal group according to the multi-phase first capacitor voltage, the second inductor current and the plurality of first modulation waves; and driving the corresponding first bridge arm according to each first driving signal group, and driving the second bridge arm according to the second driving signal group. The operation stability and safety of the distributed micro-grid system can be improved.

The invention provides an input voltage anomaly detection method, a protection method and a control circuit. The control circuit comprises a voltage-current conversion circuit, the input end of which is coupled with the power switch for obtaining the terminal voltage of the power switch; the first capacitor is coupled to the output end of the voltage-current conversion circuit; the comparison circuit is used for comparing the first capacitor voltage with a reference signal and providing an input voltage anomaly detection signal; and a switch control circuit which controls the power switch based on the output of the comparison circuit and starts input voltage abnormality protection when the input voltage abnormality detection signal is valid. The control circuit provided by the invention can realize the anomaly detection of the input voltage based on the terminal voltage of the power switch, can reduce the use of pins, simplifies a peripheral circuit, reduces the system cost, and accelerates the protection response speed.

The invention provides a method and device for discharging residual charges of an air conditioner and the air conditioner. The air conditioner at least comprises a capacitor charging control circuit, a bus capacitor circuit, a fan driving circuit, a main control chip and a fan load. The discharging method comprises the steps that the main control chip responds to a bus capacitor discharging instruction and outputs a control signal used for controlling a capacitor charging control circuit to be disconnected; and obtaining a capacitor voltage value of a bus capacitor in the bus capacitor circuit, and controlling the fan driving circuit to drive the fan load to work through the obtained capacitor voltage value. According to the invention, rapid and efficient discharge of the bus capacitor can be realized, and the hardware cost and the system complexity are reduced on the premise of not influencing the working efficiency of the air conditioner.

The invention discloses a three-level flexible excitation dynamic regulation and control method and system for a large-scale hydroelectric generating set, and relates to the technical field of flexible excitation control of the large-scale hydroelectric generating set, and the method comprises the steps: setting a DC bus voltage, and initializing a mapping relation between a capacitor voltage and an excitation output level; collecting operation parameters of a machine end, constructing a disturbance identification model and outputting a disturbance level; the excitation voltage output gear is set according to the disturbance level, the capacitor voltage difference is controlled, and dynamic voltage sharing is achieved by modulating the midpoint duty ratio. According to the method, through setting a bus target voltage and constructing excitation voltage output mapping, in combination with a disturbance level identification mechanism and a dynamic voltage-sharing strategy, closed-loop linkage of disturbance perception-voltage regulation-voltage difference control is realized. According to the method, the identification precision of the system on light disturbance and strong disturbance is effectively improved, the voltage stability and capacitance symmetry of the excitation system are enhanced, the overshoot risk is reduced, and the control robustness and safety of the system under extreme working conditions are improved.