33 results about "Three phase system" patented technology

The invention discloses an electric energy quality disturbance positioning identification method based on phase perception and multi-mode fusion, and relates to the technical field of electric power system monitoring and fault diagnosis. The electric energy quality disturbance positioning identification method based on phase perception and multi-modal fusion comprises the following steps: acquiring an original voltage signal of a three-phase electric power system; extracting a sample embedding vector of each phase based on the original voltage signal, comparing the sample embedding vector with a normal sample vector, and determining a disturbance phase with power quality disturbance in combination with an adaptive threshold value; performing time sequence feature vector extraction and bispectrum image feature extraction on the disturbance phase, and performing alignment and collaborative fusion to obtain fusion features; the electric energy quality disturbance type is identified based on fusion features, phase-level positioning of the three-phase PQD is achieved, through an innovative phase perception embedding and prototype comparison mechanism, accurate and rapid positioning of abnormal phases in a three-phase system is achieved for the first time under the condition of not depending on disturbance phase labels, and the core pain point of a traditional method is solved.

The embodiment of the invention discloses a power distribution network intelligent grounding inrush current suppression method and device, and the method comprises the steps: collecting the state data of a power distribution network, and generating a line state data set, the state data comprising real-time load characteristics and impedance parameters; analyzing the line state data set based on an edge calculation model, and predicting an inrush current peak value and a waveform characteristic of the inrush current peak value at the grounding moment in combination with a nonlinear load fluctuation characteristic caused by the access of a distributed power supply; a particle swarm optimization model is constructed according to the predicted inrush current peak value, waveform characteristics and load characteristics, a search space is constrained through a local heuristic rule, capacitance and resistance parameters of an RC damping loop are dynamically adjusted, and an optimal damping scheme is generated; on the basis of inter-phase cooperative control logic of a three-phase system, dynamically determining grounding trigger time sequences of all phases in combination with the predicted inrush current waveform characteristics; and a grounding instruction is sent to the three-station integrated mechanism, and the three-station integrated mechanism executes an inrush current suppression operation. According to the invention, efficient inrush current suppression is realized.

The invention relates to the technical field of three-phase systems, and provides a three-phase voltage state estimation method and system based on virtual coordinates, and the method comprises the steps: calculating the voltage peak value of each phase for three-phase voltages, and determining that a phase is open if the peak voltage of a certain phase is lower than a threshold value in the three peak voltages; for three-phase voltage, virtual beta-axis voltage is generated through an all-pass filter, actual beta-axis voltage is obtained through Clark transformation, the product of the virtual beta-axis voltage and the actual beta-axis voltage serves as an evaluation function, and a positive sequence and a negative sequence are distinguished according to the positive and negative of the evaluation function. The system state can be accurately and effectively judged under the conditions of three-phase imbalance and voltage distortion, the anti-noise capability and the anti-harmonic interference capability are high, and safe and stable operation of equipment under the abnormal condition is ensured.

The present disclosure relates to a grid-connected inverter and a control method and device thereof, and a phase-coherent power supply system. The grid-connected inverter comprises a power supply circuit and an inductive auxiliary voltage dividing circuit, wherein the power supply circuit and the inductive auxiliary voltage dividing circuit are connected; the grid-connected inverter is configured to boost the output voltage of an alternating current power supply; the power supply circuit comprises at least one single-phase power supply circuit, wherein each single-phase power supply circuit is connected with the inductive auxiliary voltage dividing circuit. The present disclosure provides a common-ground inverter with reduced switch quantity, the inverter of the present disclosure has a boosting characteristic, and can be extended to a three-phase system while maintaining the common-ground characteristic of the inverter.

A three-phase UPS system (1) comprises a rectifier (100) and a battery (200). The rectifier (100) has an input side (101) being connectable to an AC power system (2) to provide first input power and to the battery (200) to provide second input power to the rectifier (100). The rectifier (100) has an output side (102) to provide a DC output power in response to a power share of the first input power and the second input power. The rectifier (100) is configured to be controlled such that the power share is adjustable.

This disclosure relates to an AC-to-ACMC (2) configured to connect between a three-phase AC system (10a) and a single-phase AC system (10b). The MMC includes at least four converter arms (5) connected in a ring to allow a circulating current (I0) to circulate within the ring through each of the at least four converter arms. Each arm includes a plurality of converter units (4) connected in series. The MMC also includes phase terminals (x, y) arranged in a ring between the at least four converter arms, such that each of the at least four converter arms is separated from an adjacent converter arm on either side of the ring by at least one of the phase terminals. The phase terminals include corresponding terminals (x1, x2, x3) for each of the three phases of the three-phase AC system and corresponding terminals (y1, y2) for each of the positive and negative conductors of the single-phase AC system.

The application belongs to the technical field of electric power, and relates to a constant-voltage three-phase capacitor wireless power transmission circuit and a parameter design method. The three-phase capacitor wireless power transmission circuit comprises a high-frequency three-phase inverter, three LCL input resonance compensation networks, three compensation inductance and capacitor plates, three CLC output resonance compensation networks and a three-phase uncontrolled rectifier. In the parameter design method, firstly, actual requirements and circuit structure parameters are determined; secondly, compensation network constraints and gains are determined; and finally, considering parameter robustness and operation efficiency, the parameters are designed. Compared with a traditional single-phase CPT structure, the three-phase CPT structure has higher power transmission capacity, and the parameter design method effectively improves the robustness of the three-phase CPT system to parameter deviation, ensures constant voltage output in the entire load power range, and controls the output voltage deviation within ±5%.

An apparatus configured for use with an energy management system is provided and comprises a three-phase system connection comprising three power production wires and a neutral wire, the three-phase system connection configured to transpose the three power production wires so that multiple single-phase microinverters are equally distributed over the three-phase system connection and a power line communication (PLC) filter connected to the three-phase system connection and PLC signal wires which are transposed via the three-phase system connection and connected to the multiple single-phase microinverters, the PLC filter is configured to couple / decouple the PLC signal wires to / from the three power production wires to prevent shorting of the PLC signal wires during operation.

The invention discloses a contactor-based two-way power supply automatic switching device and a control method thereof, the contactor-based two-way power supply automatic switching device comprises a main circuit, a main power supply (L1) and a standby power supply (L2) in the main circuit are respectively connected to a modified contactor KM1 and a modified contactor KM2, the main power supply (L1) is connected to an L1 / L2 / L3 input terminal (a three-phase system) or an NC (normally closed) main contact of the contactor KM1, and the standby power supply (L2) is connected to an NC (normally closed) main contact of the contactor KM2. The standby power supply (L2) is connected to a corresponding input terminal of the contactor KM2, and the output ends T1 / T2 / T3 of the two contactors are connected in parallel and then are connected to a load air switch; normally closed contacts of the contactors KM1 and KM2 are interlocked to ensure that only one contactor can be closed at any time so as to avoid short circuit of a power supply. The voltage states of the main power supply (L1) and the standby power supply (L2) are monitored in real time, when the main power supply is abnormal, the standby power supply is automatically switched, it is ensured that the load continuously obtains stable power supply, and the reliability of the power supply system is improved.

The invention discloses a phase sequence identification method, device and equipment for a group three-phase system and a medium, and belongs to the technical field of energy storage, and the method comprises the steps: pulling up an IOBus when the phase locking of a power grid succeeds; when the host carries out successful phase locking on the power grid, the IOBus is pulled up, and when the host judges that the IOBus outputs a high level, a low-level pulse signal is sent to the IOBus when the zero crossing point of the power grid is detected; judging the time when the IOBus outputs the low-level pulse signal as the time when the host crosses the zero point, and judging the time when the power grid crosses the zero point as the time when the target slave crosses the zero point by taking the time when the host crosses the zero point as a reference; and determining phase sequences corresponding to the host and the two slaves according to the time of the target slave and the host at the zero crossing point. By means of the method, the problems that in an existing three-phase system, the phase sequence recognition result of each single-phase inverter is not high in precision, and the phase sequence recognition result is prone to interference can be solved.

The invention discloses a low-voltage three-phase metering balancing method and system, and relates to the technical field of power systems, and the method comprises the following steps: collecting current and voltage signals of a low-voltage three-phase power system in real time; calculating power, power factor and load current electrical parameters of each phase; calculating the power difference of each phase, and judging the balance condition of each phase; if it is found that power imbalance exists between the phases, a balance adjustment process is entered; adjusting load distribution or voltage compensation to enable the three-phase system to reach a balanced state; and if the balance adjustment succeeds, the normal monitoring mode is recovered. By adjusting load distribution and voltage compensation, it is ensured that the system is always kept in a balanced state, the use efficiency of electric power resources is optimized, the equipment fault risk is reduced, manual intervention and maintenance cost are reduced, the stability, reliability and energy efficiency of the electric power system are improved, and the method is suitable for popularization and application. And a more intelligent and efficient solution is provided for power management.

The invention discloses an optical storage three-phase system grid-connected circuit and method based on VSG control, and relates to the technical field of optical storage micro-grid control. The running characteristics of the synchronous generator are simulated through the VSG technology, necessary rotational inertia and damping are provided for the power grid, and the stability of the power grid is improved under the condition that the new energy power generation permeability is increased by simulating the damping and rotational inertia of the synchronous generator; meanwhile, automatic power distribution can be achieved, the self-adaptive capacity of the power grid is enhanced, synchronous operation with the power grid can be achieved, and when the power grid breaks down or disturbs, the VSG technology can provide inertial support and reduce power oscillation of the power grid, so that the reliability of power supply is improved. According to the method, large-scale access of new energy is facilitated through application of the VSG technology, negative effects caused by low inertia and no damping characteristics of power electronic equipment can be solved, the adaptability of a power grid to the new energy is improved, and a new stable operation mechanism is provided for the power grid in the aspects of new energy grid connection and power grid modernization.

To suppress fluctuation of neutral point potential in a wide operation region.SOLUTION: A power conversion device according to an embodiment of the present invention includes two power converters and a control unit. In each of the two power converters, a DC-side terminal is connected to a connection point between the first DC capacitor and the second DC capacitor connected in series, and an AC-side terminal is connectable to a three phase system. The control unit superimposes a predetermined first zero phase voltage value in one power converter of the two power converters on a voltage command value of each phase of the one power converter, imposes a limitation on a superimposition amount of the zero phase voltage value, and superimposes an exceeding first zero phase voltage value based on a first voltage value that cannot be superimposed due to the limitation on a voltage command value of each phase of the other power converter of the two power converters to obtain a voltage command value of each phase of the other power converter.SELECTED DRAWING: Figure 2

The embodiment of the invention provides a component phase state determination method and a component phase state determination system of a three-phase system, and belongs to the field of component numerical simulation. The method comprises the following steps: determining a gas-water initial phase equilibrium constant of each component according to a gas-oil initial phase equilibrium constant of each component in a three-phase system and a Henry law constant of a water phase; according to the physical property parameters of the three-phase system, the gas-oil phase equilibrium constant of each component and the gas-water phase equilibrium constant of each component, the phase equilibrium state of the three-phase system is determined; and under the condition that the three-phase system reaches phase equilibrium, according to the gas-oil phase equilibrium constant of each component and the gas-water phase equilibrium constant of each component, determining the molar percentage content of each component in the oil phase, the gas phase and the water phase. The component phase state determination method not only can calculate the molar percentage content of each component in an oil phase, a gas phase and a water phase, but also can simulate the influence of NaCl on the phase state and the disappearance process of the water phase.

The invention discloses a transformer area line loss line positioning device and a use method thereof, and belongs to the field of power detection equipment. The upper end of the clip-on ammeter main body is connected with two shafts through bearings; each shaft is in key connection with a jaw; wherein the side surface of one jaw is provided with a button for controlling opening and closing of the jaw, and an elastic part for resetting the button is arranged between the button and the clip-on ammeter main body. Each shaft is in key connection with a gear, an arc-shaped groove is formed in the outer circle face of each shaft, and the outer side of each shaft is sleeved with a sleeve. The inner wall of the sleeve is fixedly connected with a limiting block in sliding fit with the arc-shaped groove. According to the utility model, not only can workers be prevented from electric shock, but also wires or a plurality of wires in a three-phase system can be fixed through the arc-shaped rod during use, and the direction and distance of the undetected wires can be changed through the gap between the arc-shaped plate and the limiting plate, so that the influence of a magnetic field generated by current in the undetected wires on a detection result is reduced; and more accurate reading is ensured.

The application provides a real-time calculation SVPWM method capable of eliminating PWM one-beat delay. According to the characteristics of SVPWM vector output, a vector with long enough duration is selected to be output at the starting moment of each beat, so as to ensure that no vector switching occurs within the calculation time, and to ensure that the system can complete calculation and update PWM instruction within the calculation time, so that the delay update of the PWM instruction is equivalent to the update at the sampling point. The application also provides a proper vector switching sequence and a duty cycle calculation method, so that the PWM strategy can reliably operate, and according to the voltage output law of the controller, a hysteresis loop and a lookup table are designed to determine the output vector at the starting moment of each beat. The application can ensure that the one-beat delay of the system is eliminated, and the modulation range is not lost, so that ideal three-phase system non-delay PWM is achieved.

The invention discloses a neutral point potential balance and common-mode voltage suppression method and device of a three-level dual three-phase system, and belongs to the technical field of motor control. The method comprises the following steps: acquiring a target modulation wave, sorting reference voltages according to the magnitude, and dividing the reference voltages into six sectors; zero-sequence voltage is calculated according to the sorted reference voltage; according to the zero-sequence voltage, duty ratios of a high level, a zero level and a low level in a carrier period are calculated; obtaining a zero level duty ratio adjustment amount d0 through a PI controller, and subtracting the zero level duty ratio adjustment amount d0 from the zero level duty ratio of the non-clamping phase to obtain a PWM sequence of each phase; performing phase shifting on the PWM sequence of each phase according to a preset phase shifting strategy to obtain a target modulation wave; and comparing the target modulation wave with the carrier wave to generate a target PWM signal, and controlling the three-level inverter. The unbalance of the neutral point potential at the inverter side is suppressed, and the influence of the common-mode voltage is suppressed.

The invention relates to an electrical energy transmission arrangement (1) and to a method for coupling two asynchronous three-phase systems (2, 3, 12, 13, 14). The electrical energy transmission arrangement (1) comprises a converter (4), which is designed to generate a second three-phase AC voltage with an adjustable frequency from a first three-phase AC voltage, and has three converter units (15), which each have a three-phase coupling transformer (16) and a modular multilevel converter (17). The multilevel converter (17) of each converter unit (15) is connected on the input side to the three phases (A, B, C) of the first three-phase AC voltage via the three-phase coupling transformer (16) of the converter unit (15), has two output connections (U, V) on the output side, and is designed to generate a single-phase AC voltage between the output connections (U, V). The output connections (U, V) of the three multilevel converters (17) are connected to one another to form output-side phase connections (L1, L2, L3) of the converter (4) for the three phases of the second three-phase AC voltage.

The invention discloses a photovoltaic power generation area electric energy quality optimization method based on a three-phase HDT system, and relates to the technical field of power distribution network electric energy quality optimization, and the method comprises the steps: constructing a three-phase hybrid distribution transformer system composed of a standard transformer, a power electronic converter, a bypass switch and an LC filter; based on the operation characteristics of the three-phase hybrid distribution transformer system, simulation testing is carried out on the voltage amplitude adjusting capability and the harmonic compensation capability of a power supply side of the three-phase hybrid distribution transformer system by using a simulation technology so as to verify the voltage adjusting capability of the three-phase hybrid distribution transformer system; and in combination with the voltage regulation capability of the three-phase hybrid distribution transformer system, the electric energy quality of the photovoltaic power generation area is optimized through the three-phase hybrid distribution transformer system. According to the invention, it is verified that the three-phase HDT system has good voltage amplitude and phase compensation capability and harmonic compensation capability, and a good foundation is laid for electric energy quality optimization application of the three-phase HDT system in a photovoltaic power generation area.

The application provides a driving circuit for a three-phase system power switch device, the three-phase system comprises a power switch group corresponding to each phase, the power switch group comprises an upper bridge arm power switch and a lower bridge arm power switch, the driving circuit corresponds to the upper bridge arm power switch, the driving circuit comprises a capacitor voltage division circuit, a voltage stabilizing circuit and a push-pull driving circuit, the capacitor voltage division circuit is connected with two phases except the corresponding phase, the output end of the capacitor voltage division circuit is connected with the corresponding voltage stabilizing circuit, the push-pull driving circuit and the upper bridge arm power switch of the corresponding phase in sequence, direct power is taken from the three-phase power supply, and a stable direct current voltage is generated to reliably drive the power switch device. The application realizes efficient and reliable driving of the power switch device, and overcomes the limitations of the traditional driving circuit which depends on a heavy isolation transformer or a complex switch power supply.

The invention provides a driving circuit for a three-phase system power switch device, the three-phase system comprises power switch groups in one-to-one correspondence with each phase, each power switch group comprises an upper bridge arm power switch and a lower bridge arm power switch, the driving circuit corresponds to the upper bridge arm power switch, and the lower bridge arm power switch corresponds to the lower bridge arm power switch. The drive circuit comprises a capacitance voltage division circuit, a voltage stabilizing circuit and a push-pull drive circuit, the capacitance voltage division circuit is connected with two phases except the corresponding phase, and the output end of the capacitance voltage division circuit is connected with the upper bridge arm power switch of the corresponding phase through the corresponding voltage stabilizing circuit and the push-pull drive circuit in sequence. Power is directly taken from a three-phase power supply, and stable direct-current voltage is generated to reliably drive a power switch device. According to the invention, efficient and reliable driving of a power switching device is realized, and the limitation of dependence on a heavy isolation transformer or a complex switching power supply in a traditional driving circuit is overcome.

The application discloses a zero sequence injection modulation method of a modular multilevel matrix converter and relates to the technical field of power electronic control. The modular multilevel matrix converter is connected with two AC systems with different frequencies; the method comprises the following steps: obtaining modulation wave components of three-phase systems on input and output sides respectively through capacitor voltage outer loop control and input current inner loop control of a sub-converter and overall output current control; for each bridge arm, corresponding modulation waves are calculated based on the two modulation wave components; a zero sequence modulation voltage is calculated based on the modulation wave components of the three-phase system on the input side; the zero sequence modulation voltage is injected into each modulation wave to obtain a zero sequence modulation wave; all the zero sequence modulation waves are modulated by using a carrier wave to generate trigger pulses which are distributed to switch devices of corresponding bridge arms. The method can expand the linear modulation range and operation range of the modular multilevel matrix converter and improve the utilization rate of capacitor voltages of sub-modules by injecting zero sequence components into modulation waves.

The application relates to the technical field of power switches, and discloses a three-phase synchronous drop type fuse device and method, which comprises a top shell, the lower surface of the top shell is fixedly connected with a resistance assembly, the bottom end of the resistance assembly is fixedly connected with a base, the lower side of the resistance assembly is fixedly connected with a supporting shell, the outer side of the supporting shell is fixedly connected with an insulating support, the inner side of the supporting shell is rotationally connected with a fuse tube, the outer side of the fuse tube is slidably connected with a sliding sleeve, the lower surface of the top shell is fixedly connected with an adjusting assembly, the lower side of the adjusting assembly is rotationally connected with a sliding rod, the top end of the resistance assembly is externally provided with a fixing assembly, and the rotationally connected position of the fuse tube and the supporting shell is provided with a protection assembly. Through the cooperation of the sliding sleeve, the sliding rod and the adjusting assembly, when the fuse tube drops due to abnormal current, the action of the single fuse tube can be synchronously transmitted to the other two phases of the three-phase system, so that the reliability and stability of circuit protection are improved.

A three-phase system and a distributed control method thereof. The three-phase system comprises: three-phase circuits, each phase circuit comprising at least one power conversion unit; at least three phase controllers corresponding to the control of each phase circuit respectively, each of the phase controllers comprising a communication interface, and the at least three phase controllers being communicatively connected to each other through the communication interface; wherein the phase controller of each phase circuit receives information sent by the phase controllers of the other two phase circuits through the communication interface, and adjusts the bridge arm voltage of the at least one power conversion unit in the phase circuit. The three-phase system and the distributed control method thereof solve the problems of three-phase current balance and three-phase direct current voltage stability through the coordination among the three phases. Through the present application, the three phases can be independently controlled, and the control flexibility is improved.

The present invention relates to a heating panel which allows the state of each heating element to be easily monitored in order to quickly recognize faults and take actions by replacing the panel inside the heating module. The heating panel is reliable in height and easy to maintain. The heating panel (P) comprises at least one heating element (T) formed by resistors (R1, R2, R3) of a triple interconnected in a star pattern wherein each free end of each resistor (R1, R2, R3) of said triple receives electrical energy from a different phase of the three-phase system and is connected to the first bus (3) by at least one controlled switch (SCR, 4). A first control switch (2A) is interposed between the controlled switch (SCR, 4) and the first bus bar (3). Furthermore, the first bus (3) is connected to the at least one transformer (1) via at least one second control switch (2B). The star center (CS) of the triad (R1, R2, R3) is in turn connected to a second busbar (8). Furthermore, a current measurement device (6) is provided between or along the star center (CS) of the triad (R1, R2, R3) and the second busbar (8) in order to detect the intensity of a possible current passing through the star center (CS) of the triad, and wherein a control unit (PLC) is provided which is adapted to receive measurement data from the current measurement device (6), in this way, the state of the heating panel (P) is monitored.

The invention discloses an automatic commutation adjustment method and system based on three-phase load imbalance, and relates to the technical field of electric data analysis, and the method comprises the steps: obtaining the balance degree data of a three-phase load, carrying out the comparative analysis of the balance degree data of the three-phase load based on a data analysis terminal, and determining the to-be-verified risk data of the balance degree of the three-phase load. According to the method, the historical operation data of the three-phase load is subjected to data calculation and analysis processing to determine the balance degree risk data of the three-phase load, then the balance degree risk data of the three-phase load is subjected to feature analysis to determine the risk data of the same feature and the risk data of the single feature, and finally, the risk data of the three-phase load is determined. The three-phase system is monitored by training the intelligent monitoring model through the risk data with the same characteristic and the risk data with the single characteristic, and when the three-phase system is unbalanced, the three-phase system is subjected to commutation processing in time, so that the three-phase system is ensured to be always in a balanced state, and the problem of local power failure is avoided.

The invention relates to a method for operating a drive unit (1000) comprising an electric machine (1) and a power converter arrangement (100) for supplying the electric machine with electrical power. The power converter arrangement comprises a first DC voltage terminal (101) and a second DC voltage terminal (102) and at least two half-bridges (110, 120, 130). In each half-bridge, a first and a second semiconductor switch (111, 121, 131, 112, 122, 132) are arranged between the first or second DC voltage terminal (101) and a center terminal (113, 123, 133) of the half-bridge (110, 120, 130). Furthermore, at least two half-bridges comprise a current sensor (114, 124) configured to measure the current flowing through the center terminal.In this method, a symmetrical three-phase system is produced, and the current intensity profile of the flowing current is recorded by each current sensor for a first time interval. Subsequently, a correction factor for the current intensity is determined for at least one of the at least two half-bridges as a function of a characteristic parameter of the recorded current intensity profiles, and the drive unit is operated using the determined correction factor. The invention further relates to a drive unit.

Power transformer (2) for three phase systems including three galvanically separated windings of which two windings are the Y-connected main windings and the third winding is connected as open delta for connection of an earthfault current compensation equipment (4, 6), and the method of grounding the neutral on either of the main windings decides on which side of the transformer the earth fault current compensation works.

The invention relates to the technical field of unit converters, in particular to a full-power converter system for a variable-speed pumped storage unit and a control method. The M3C circuit topological structure adopts a modular matrix type converter framework and comprises a plurality of sub-converter units; the operation control strategy module is integrated with a double-closed-loop decoupling control framework, comprises an outer-loop control unit and an inner-loop control unit, and coordinates regulation and control of current, voltage and power. Three sub-converters in star connection are adopted to form a nine-bridge-arm matrix structure, each bridge arm is formed by cascading H-bridge sub-modules and connecting the H-bridge sub-modules with inductors in series, and flexible interconnection of a primary-side three-phase system and a secondary-side three-phase system is achieved; a double-closed-loop decoupling framework is integrated in control, and power, direct-current capacitor voltage and alternating-current voltage amplitude are accurately regulated and controlled through combination of outer-loop fuzzy PI online setting and inner-loop model predictive control.

The invention discloses a modular multilevel converter electromagnetic transient order reduction system and method based on sub-module aggregation. The interior of a modular multilevel converter comprises hundreds of sub-modules, and the electromagnetic transient simulation solving speed of the modular multilevel converter is difficult to meet the real-time requirement due to a complex topological structure. The system can be applied to different types of sub-modules, such as half-bridge type and full-bridge type sub-modules. And for a three-phase system, the order of the alternating current side can be simplified into three orders by aggregating the internal sub-modules, so that the simulation speed is greatly improved. Meanwhile, the internal switching state and the capacitor voltage of each sub-module are also considered. In addition, simulation of the locking mode can be realized without modifying the equivalent circuit.