639 results about "Neutral line" patented technology

The present invention relates to the technical field of secondary device monitoring. Disclosed are an online monitoring method for an operating state of a secondary current loop neutral line, and a system. The method comprises: by using a high-precision sensor for collection and a composite filtering algorithm for processing, obtaining a secondary current fundamental component of each neutral line of a transformer substation which is not influenced by harmonic waves and transient states, and uploading the secondary current fundamental component to a protection information master station; retrieving originally configured access protection information master station information to obtain three-phase secondary current loop information of each bay of the transformer substation, summarizing secondary current information of all monitoring ranges, and performing grouping and classification marking on said information by transformer substation, bay and winding; and using the collection information for operation analysis, automatically identifying and confirming an operating state of the line, and on the basis of the operating state, calculating the outlier deviation linearity and the continuous dynamic trend deviation degree of each winding of each bay. The present invention solves the problem that intermittent faults in secondary current loop neutral lines are concealed and are not easily found, realizes comprehensive monitoring for the whole system, and can quickly and accurately position a specific winding and issue an abnormal early warning.

The invention discloses an electric energy metering method under power grid waveform distortion, and particularly relates to the technical field of electric energy metering. The problems of false triggering of an energy compensation mechanism, metering deviation and electricity price settlement risks caused by zero-sequence current or false phase drift easily generated in a multipoint grounding or grounding fault power system in the prior art are solved. According to the anomaly identification and control method integrating zero-sequence current frequency domain characteristic analysis and three-phase phase deviation trend consistency judgment, the false phase deviation state is accurately identified through synchronous sampling, frequency domain analysis and trend consistency evaluation of three-phase voltage, three-phase current and neutral line current, and the false phase deviation state is accurately identified. The error compensation behavior is shielded in real time, the fundamental wave power metering mode is switched to, the electric energy metering accuracy is guaranteed through an error backtracking correction mechanism after recovery, and the anti-interference capability and metering reliability of the electric meter under complex working conditions are effectively improved.

Embodiments of this invention discloses a split-phase output power adjustment system, adjustment method, and storage medium in a low voltage transformer area. The system includes adjustment power supplies, split-phase power adjustment modules, sub-controllers, a main controller. The adjustment power supplies connected to the split-phase power adjustment modules, and total power P of the adjustment power supplies complying with a relationship as follows: P=Pt=PG1+PG2+ . . . . PGn; wherein Pt is power required to comply with three-phase current unbalance adjustment of a distribution transformer, PG1, PG2, . . . PGn is power generated by each of the adjustment power supplies to compensate three-phase current unbalance in a transformer area; wherein the split-phase power adjustment modules are connected to lines of three phases A, B, and C and a neutral line N in the transformer area; wherein the sub-controllers are connected to the adjustment power supplies, and the sub-controllers communicate with the main controller to control power generated by each of the adjustment power supplies, so as to compensate the unbalanced three-phase current in the transformer area. Coordinated adjustment of multiple distributed power supplies realizes precise control of three-phase imbalance in the transformer area, which reduces line loss and improves power quality.

A multi-phase LLC resonant converter circuit (10) includes: first to third LLC resonant converters each including a series circuit (S1 to S3) of a first switch and a second switch that are connected in parallel to a DC power supply, a high-frequency transformer (T1 to T3) including a primary-side winding and a secondary-side winding, a resonant circuit including a resonant reactor (Lr1 to Lr3) connected between a connection point of the first switch and the second switch and one end of the primary-side winding, a resonant capacitor (Cr1 to Cr3) in which one end is connected to the other end of the primary-side winding, and a divided resonant capacitor (Cn1 to Cn3) in which one end is connected to a connection point of the primary-side winding and the resonant capacitor; a first neutral line (N1) that connects the other end of the resonant capacitor; a neutral line reactor (Ln) connected between the first neutral line and a power supply line of the DC power supply; and a second neutral line (N2) that connects the other end of the divided resonant capacitor.

The invention belongs to the technical field of power electronics of power supply or power distribution, and provides a control method of a three-phase four-wire inverter, a controller and an inversion control system. A first control component is generated by using a phase angle, an inversion side three-phase current sampling value and a proportional integral compensator; a second control component and a third control component are generated by using a power grid voltage angular frequency, a neutral line current sampling value, a repetitive controller and a proportional resonance controller, the three control components are combined to control an inverter power switch tube, a proportional integral compensator is still adopted, the algorithm is simple, parameters are easy to design, and the reliability is high. And meanwhile, a repetitive-proportional resonance (RC-PR) composite controller is utilized to realize suppression of neutral line fundamental wave and harmonic current, and the method has faster dynamic response to load abrupt change, so that optimization of dynamic performance and steady-state performance is realized.

A smart load control system includes: a neutral forming auto-transformer (NFT) structured to form a neutral line; a plurality of smart circuit breakers (SCBs) including an islanding and grid-connecting device (IGD) coupled to the electric grid and an EV SCB coupled to the bidirectional EV charger, the IGD structured to sense grid voltage and switch ON and OFF the electric grid, the EV smart circuit breaker structured to sense EV voltage and switch ON and OFF the bidirectional EV charger; and a building energy system manager communicatively coupled to the plurality of SCBs and structured to collect data from each SCB, the data including at least the grid voltage and the EV voltage, select one of grid-connected mode or islanded mode based on the grid voltage and the EV voltage, perform a safe transition to the selected mode, and monitor the grid voltage and the EV voltage.

The invention discloses an electricity stealing behavior detection method and system based on an intelligent electric energy meter, and the method comprises the following steps: constructing a phase locking reference frame at the end of the intelligent electric energy meter, synchronously collecting a voltage phase and a current phase through high-precision time, generating a direction discrimination baseline, setting a zero-power crossing point and a direction overturning threshold value, and carrying out the detection of an electricity stealing behavior. Outputting a direction baseline consistency index as a direction identification reference; according to the invention, through phase locking, high-precision synchronization, neutral line drift analysis, multi-table data alignment and phase disturbance verification, accurate identification and causal confirmation of a current backward flow behavior are realized, a disturbance user is reversely positioned in combination with a disturbance fingerprint, an intervention instruction is output, and an identification-verification-positioning-control closed loop mechanism is constructed. And the anti-electricity-stealing capability and the metering accuracy of the intelligent electric energy meter in a complex power supply environment are obviously improved.

The invention discloses a power supply circuit and electrical equipment. The power supply circuit comprises a three-phase power supply and three rectification and inversion modules, wherein each rectification and inversion module comprises a first input end, a second input end and an output end; the first input ends of the three rectification inversion modules are respectively connected to three phase lines in a three-phase power supply in a one-to-one correspondence manner; second input ends of the three rectification inversion modules are connected to a neutral line in the three-phase power supply; the output ends of the three rectification inversion modules are respectively connected to three loads in a one-to-one correspondence manner; and the rectifying and inverting module is used for sequentially rectifying and inverting the input voltage and then supplying power to corresponding loads. According to the invention, the three-phase power supply is divided into three independent single-phase power supply paths for three loads, single-phase rectification is carried out on each phase independently, the voltage level is reduced, a low-voltage-level device can be selected, and the cost is reduced; the three-phase load is balanced, the harmonic dispersion is realized, and the harmonic pollution is reduced; fault area isolation is realized, and maintenance difficulty and maintenance cost are reduced.

The invention discloses a two-stage multi-mode bidirectional inverter circuit, which comprises a direct-current power supply DC, an alternating-current power supply AC, a DC / DC circuit, a direct-current voltage-dividing capacitor Cb1, a direct-current voltage-dividing capacitor Cb2, a DC / AC circuit and a controller, and is characterized in that a negative electrode of a second port of the DC / DC circuit is connected with a negative electrode of the direct-current voltage-dividing capacitor Cb1 and a negative electrode of a direct-current port of the DC / AC circuit; a middle point of a second port of the DC / DC circuit is connected with a negative electrode of a direct-current voltage-dividing capacitor Cb1 and a positive electrode of a direct-current voltage-dividing capacitor Cb2, and is connected to an alternating-current neutral line N; the AC port of the DC / AC circuit is connected with an AC live wire L1 and an AC live wire L2. The controller stably outputs voltage or current by controlling the DC / DC circuit and the DC / AC circuit, and bidirectional electric energy conversion is achieved. According to the invention, direct-current capacitance and additional circuits do not need to be increased, the size of the device is reduced, the system cost is reduced, the conversion efficiency is improved, and the device can be widely applied to new energy power generation and energy storage and other industrial and civil bidirectional power conversion systems so as to meet the global power supply and consumption requirements.

The utility model discloses an integrated AC charging module used for a charging pile system, comprising a driving mechanism and a coupling linkage mechanism which are installed in a main cavity of a housing structure, and a main controller which is detachably arranged in a side cavity, and the main controller is used for controlling an action instruction of the driving mechanism. The coupling linkage mechanism is provided with a plurality of groups of moving contacts and a plurality of groups of static contacts which share one set of driving mechanism, so that on-off of all phase lines and zero lines is controlled, multi-loop on-off control is realized, and the coupling linkage mechanism is simple in structure and convenient to operate. The alternating current charging module adopting the technical scheme realizes integrated installation of the driving mechanism, the coupling linkage mechanism and the main controller, has the characteristics of small size, large contact opening distance, low temperature rise, improved load capacity and convenience in maintenance, simplifies the installation process, enables the product structure to be more compact, reduces the cost, conforms to the miniaturization and integration trend of the product, and is suitable for popularization and application. The method is suitable for new energy charging piles.

A power conversion device includes a DC / DC conversion circuit and a DC / AC conversion circuit, the DC / DC conversion circuit is configured to connect to an energy storage unit and the DC / AC conversion circuit, the DC / AC conversion circuit includes a positive bus, a negative bus, and a neutral line, the DC / AC conversion circuit is configured to connect to an grid. An input voltage of the DC / DC conversion circuit is a voltage between the positive bus and a positive end of the energy storage unit, or a voltage between a positive end of the energy storage unit and the neutral line, or a voltage between the neutral line and a negative end of the energy storage unit, or a voltage between a negative end of the energy storage unit and the negative bus. An output voltage of the DC / DC conversion circuit is half of a direct current bus voltage.

The invention discloses a waveform classification optimization method and system for hidden danger early warning of a power secondary circuit. The method comprises the following steps: obtaining three-phase current recording file window data; classifying and labeling the three-phase current recording file window data based on a preset numerical value judgment principle to obtain labeled target three-phase current recording file window data; converting window data of the target three-phase current recording file into two-dimensional images through a GASF (Geometric Amplitude Shift Function) and a GASF (Geometric Amplitude Shift Function), and combining the two-dimensional images into at least one image unit; inputting the at least one image unit into a preset VGG16 convolutional neural network for iterative training to obtain a current secondary circuit neutral line fault diagnosis model; and inputting the real-time fault recording time sequence data into the current secondary circuit neutral line fault diagnosis model, and outputting to obtain a waveform classification result at a three-phase current circuit neutral line. The problem that efficient and accurate online detection and judgment are difficult to realize at present when the neutral line of the current secondary circuit is virtually connected or broken is solved.

The embodiment of the invention provides a battery charging and discharging device and a new energy automobile, and the device comprises a charging interface which is used for accessing an external DC power supply, and comprises a positive electrode access end and a negative electrode access end; the electric drive assembly comprises a motor, a first bridge arm and a second bridge arm; each phase line of the motor is respectively connected with the first end of the first bridge arm and the first end of the second bridge arm, and a neutral line of the motor is connected with the positive pole access end or the negative pole access end; the second end of the first bridge arm is connected with the anode access end, and / or the second end of the second bridge arm is connected with the cathode access end; and the battery pack interface is used for connecting a first access end of a positive electrode of a power battery pack to be connected with a neutral line of the motor, and connecting a second access end of a negative electrode of the power battery pack to be connected with a second end of the second bridge arm. The battery charging requirement can still be met under the condition that the output voltage of the charging pile is smaller than the battery charging voltage.

A ground fault circuit interrupter (GFCI) device includes a ground fault detection module for detecting a ground fault in a neutral line of a plurality of current carrying lines and generating a ground fault signal in response thereto, including a neutral line detection coil having a magnetic core made of a silicon steel and through which the current carrying lines pass; a leakage current detection module for detecting the ground fault signal and detecting a leakage current signal on the current carrying lines, and generating a zero sequence current fault signal in response to either signal; and a drive module for receiving the zero sequence current fault signal and driving a switch module to disconnect the electrical connection of the current carrying lines in response thereto. The GFCI device can avoid false tripping when high frequency currents flow through the current carrying lines, improving user experience and enhancing safety.

Disclosed in the present invention is a ground fault device end-of-life self-test system. An induction coil and a neutral coil are used for sensing and acquiring a ground fault leakage current signal of a live wire or a neutral wire. A trip device is used for cutting off the power supply to a load in the event of a ground fault by driving a solenoid by means of a thyristor which is triggered by an IC1 to turn on. A manual test button is used for manually testing the function of a ground fault device. A rectifying circuit is used for rectifying an alternating current (AC) and outputting same to a direct current, and providing the direct current to IC1 and IC2 direct current power supplies. A ground fault detection circuit is used for completing ground fault detection, and controlling the drive to trigger the thyristor to turn on or off. A ground fault self-test control circuit is used for controlling the testing of a ground fault detection function without affecting normal ground fault detection and protection functions.

The invention discloses a common-mode electromagnetic interference modeling and suppression method for a matrix converter, and the method comprehensively considers high-frequency parameters and topological characteristics, builds a conduction CM EMI equivalent circuit model of the matrix converter, completes the impedance network fitting of key elements and the extraction of high-frequency parasitic parameters, and achieves the modeling and suppression of the common-mode electromagnetic interference of the matrix converter. The precision of the CM EMI model of the matrix converter is improved, and the analysis of the CM EMI characteristics of the matrix converter is simplified. According to the common-mode electromagnetic interference suppression method for the matrix converter, CM EMI characteristics of the matrix converter are analyzed, a low-attenuation loop in the converter is constructed by adopting a method of combining a neutral line leading-back type structure and increasing output filter capacitor neutral-point-to-ground parasitic capacitance, the propagation proportion of noise in a linear impedance stabilization network measurement branch is reduced, and the measurement accuracy of the common-mode electromagnetic interference suppression method for the matrix converter is improved. And effective suppression of low-cost CM EMI noise is realized on the premise of not depending on an input EMI filter.

An energy conversion device is provided. The device includes: a reversible pulse width modulation (PWM) rectifier (11) and a motor coil (12), where the motor coil (12) includes at least a first winding unit and a second winding unit, and the first winding unit and the second winding unit are both connected with the reversible PWM rectifier (11). The first winding unit is connected with at least one of neutral lines in the second winding unit, where at least one neutral line of at least one of the winding units is connected with a first end of a first direct current (DC) charging and discharging port (3), the reversible PWM rectifier (11) is connected with a first end of a external battery (2) and a second end of the external battery (2) respectively, and a second end of the first DC charging and discharging port (3) is connected with the second end of the external battery (2).

The invention discloses a neutral line breakage detection and positioning method and system based on third harmonic energy characteristics, and the method comprises the steps: firstly, extracting the current and voltage of a load, calculating the third harmonic component through Fourier decomposition, obtaining the third harmonic energy through calculation, sequentially calculating the third harmonic energy ratio of two adjacent regions, and calculating the third harmonic energy ratio of the two adjacent regions; and comparing the calculated third harmonic energy ratio of each position with a set threshold value, and judging whether a neutral line breaking fault occurs or not and judging a line breaking position according to a result. According to the method, the neutral line breakage fault can be correctly distinguished and positioned, and the neutral line breakage detection capability is effectively improved.

The embodiment of the invention discloses a photovoltaic system and a parallel operation circulating current suppression method thereof, the photovoltaic system comprises a plurality of power converters connected in parallel, each power converter comprises an inversion module, an output filter, a detection circuit and a controller, and the output filter comprises a variable inductor and / or a variable capacitor. The variable inductor comprises a first winding connected with the first switching circuit in series, and the controller can control the first switching circuit to be switched on or switched off according to the current value, detected by the detection circuit, flowing through the output filter so as to change the inductance value of the variable inductor. The variable capacitor is connected in series with the second switching circuit between the neutral line and the alternating current bus, and the controller can control the second switching circuit to be switched on or switched off according to the current value which is detected by the detection circuit and flows through the output filter so as to change the state that the variable capacitor is connected to the alternating current bus. By changing the inductance value and / or the capacitance value, the position of the resonant frequency point of the output filter can be changed, so that the parallel operation circulating current is inhibited.

The present application discloses a control method, apparatus, device, and system for a charging and discharging circuit, and a storage medium. A neutral wire of a motor in the charging and discharging circuit is connected to a charging and discharging switching bridge arm group, the method including: acquiring a first current value in the neutral wire in real time during charging and discharging of a power battery by the charging and discharging circuit; and regulating the magnitude of the first current value according to the first current value, first peak current, and second peak current, where the first peak current is known peak current of the charging and discharging switching bridge arm group, and the second peak current is known peak current in the neutral wire. The control method for a charging and discharging circuit of the present application regulates the magnitude of the first current value according to the first current value in the neutral wire, the known peak current of the charging and discharging switching bridge arm group, and the known peak current of the neutral wire, and can thus timely adjust the current when an abnormality in the current value occurs during charging and discharging of the power battery, thereby avoiding damage to the circuit.

The embodiment of the invention discloses a line loss calculation method for a low-voltage transformer area containing distributed photovoltaic. The line loss calculation method comprises the following steps: acquiring typical daily data of the low-voltage transformer area, access phase data and output data of the distributed photovoltaic, electricity consumption and connected phases of users, line impedance of each phase and a network topology structure of the low-voltage transformer area; establishing a line loss theoretical calculation model according to the typical day data of the low-voltage transformer area, the access phase data and output data of the distributed photovoltaic, the electricity consumption and the connected phases of the user, the line impedance of each phase and the network topology structure of the low-voltage transformer area; based on the line loss theoretical calculation model, calculating a user node voltage value of each phase through an improved forward-backward sweep method, taking the voltage value as an initial value of a Newton-Rafson method, and performing load flow calculation on each phase to obtain power loss on each phase line; and adding the total neutral line loss and the loss power consumption of each phase line to obtain the typical daily three-phase bus loss of the transformer area, so that the accuracy and the processing speed of theoretical calculation of the line loss can be improved.

The invention provides an inverter and a grid-connected and off-grid switching device and method thereof, and the device comprises a grid-connected switch which is disposed between an AC side grid-connected port of the inverter and a power grid; the off-grid switch is arranged between the alternating current side off-grid port of the inverter and the load; the grounding switch is configured to be used for controlling connection and disconnection between a neutral line of the inverter and a protective ground line; the control module is configured to control the grid-connected switch and the off-grid switch to be switched on and control the grounding switch to be switched off when the inverter is in a grid-connected state; and when the inverter is in the off-grid state, the grid-connected switch is controlled to be switched off, and the off-grid switch and the grounding switch are controlled to be switched on. The device ensures that the grounding switch and the grid-connected switch are not in a conducting state at the same time, and the safety of the inverter is ensured.

The embodiment of the invention discloses a distribution transformer electrical parameter complex field on-line synchronous vector monitoring device and method, and the device comprises a high-precision synchronous vector measurement and collection module and a controller, and the high-precision synchronous vector measurement and collection module is connected with the controller. The high-precision synchronous vector measurement and acquisition module is used for being connected with a neutral line at the low-voltage side of the distribution transformer to be measured and a three-phase line at an outlet, and is used for measuring and synchronously acquiring a zero-sequence voltage vector and a neutral line current vector at the low-voltage side of the distribution transformer to be measured. The controller is used for determining the short-circuit complex impedance of the distribution transformer to be measured according to the zero-sequence voltage vector and the neutral current vector, so as to determine the load loss and the short-circuit voltage of the distribution transformer to be measured according to the short-circuit complex impedance, namely, the zero-sequence voltage vector and the neutral current vector are simply and synchronously measured on the low-voltage side of the distribution transformer. Therefore, on-line monitoring of short-circuit complex impedance and electrical parameters can be realized, and problems in the prior art are solved.

One aspect of the invention relates to a bidirectional on-board charger 2 for a vehicle 1, comprising:a bidirectional AC-to-DC converter 8 designed to supply power to an electrical power supply socket 6 for an external electrical device;means for detecting an electrical insulation fault 9, connected to a phase line 12 and to a neutral line 13 of said electrical power supply socket 6; a switch 16 arranged on said phase line 12; a switching means 18 designed to control the switch 16 between a first position P1 in which the means 9 are connected to the socket 6 and a second position P2; a resistor 20 which, when the switch 16 is in the second position P2, is electrically connected to the switch 16 and to a ground 10 of the vehicle.

An offline voice-controlled Christmas light power controller includes: a power supply module, and an input end of the power supply module is electrically connected with an alternating current live line and an alternating current neutral line; a master control module, and a power supply end of the master control module is electrically connected with an output end of the power supply module; a voice recognition module; and a driving module. The master control module controls the driving module to start up to turn on or off the light strip based on whether the startup signal is received. The voice recognition module recognizes a voice collected by the microphone and starts up or shuts down the driving module based on the voice, without manual operation, bringing much convenience.

The invention relates to the field of three-level inversion twin-trawling systems, and particularly discloses a harmonic current suppression method, system and product of a three-phase three-level inversion twin-trawling system, and the method specifically comprises the following steps: S1, a bus voltage balance control step; s101, acquiring a bus voltage error value; s102, acquiring a bus voltage error correction value; s2, a neutral current harmonic suppression step; s201, acquiring a common-mode current flowing through a node connected with the power side and the load side; s202, acquiring a higher harmonic component in the common-mode current; s203, obtaining a higher harmonic component suppression correction value; and S3, superposing the corrected value and a three-phase voltage output modulation wave to obtain a three-phase inverter circuit modulation signal of a power side in the three-phase three-level inverter twin trawling system. The harmonic suppression algorithm of the output current can be provided based on the single-power three-phase dragging system, the cost can be reduced, and the current distortion can be reduced, so that the real current output condition can be simulated.

The utility model provides a film capacitor glue pouring shaping and pin positioning work fixture, which is characterized by comprising a base, a filler strip and a tooth-shaped positioning clamping plate, the tooth-shaped positioning clamping plate, the filler strip and the base are sequentially arranged from top to bottom, the base is provided with a plurality of cavities, the sizes of the cavities are matched with the sizes of product shells, and the tooth-shaped positioning clamping plate and the filler strip are matched with each other. The product shell is loaded with a product and then is arranged in the base cavity; the appearance size of the tooth-shaped positioning clamping plate is consistent with that of the base, the middle of the tooth-shaped positioning clamping plate is an empty slot, a plurality of convex teeth are vertically symmetrical in the empty slot and are provided with cavities matched with sheet pins to insert, and the neutral lines of the convex teeth are consistent with the neutral line of the cavity of the base; the base cavity is through up and down, so that the product is easy to demould after the glue pouring material is cured; the hollowed-out parts of the tooth-shaped positioning clamping plate are more, so that the glue filling operation is easy to complete; a cavity of a base of the product shell is matched, so that deformation of the shell in the high-temperature drying process is prevented; the tooth-shaped positioning clamping plate fixes the sheet pins, so that the pin positioning problem of the capacitor is solved, and deviation of the pins in the transfer process after glue pouring is prevented.

Disclosed in the present invention is a grounding fault detection apparatus having a self-checking function. The grounding fault detection apparatus comprises: an induction coil, a neutral coil, a trip unit, a manual test unit, a rectifier circuit unit, a power supply management unit, a grounding fault detection unit and a grounding fault self-checking test unit. The grounding fault detection unit receives grounding fault leakage current signals acquired by means of the induction coil and the neutral coil, then processes, amplifies, filters, converts, performs determination, etc. on effective leakage current signals, and performs control to generate silicon-controlled rectifier / trip unit driving signals; the grounding fault self-checking test unit detects a phase voltage signal, periodically generates a simulated grounding fault leakage current signal, detects whether the response of a system electric leakage detection loop and a tripping loop to a simulated grounding fault is correct, and performs determination and can output corresponding acoustic, optical and electrical alarm signals.

The invention relates to the technical field of energy storage converters, in particular to a three-level inverter DPWM and SVPWM smooth switching method and system, a medium and equipment, and the method comprises the steps: determining a current modulation mode which comprises the SVPWM and the DPWM; a first modulation coefficient and a second modulation coefficient are set, the first modulation coefficient corresponds to the weight of the SVPWM common-mode voltage, the second modulation coefficient corresponds to the weight of the DPWM common-mode voltage, and the sum of the first modulation coefficient and the second modulation coefficient is constantly 1; determining values of a first modulation coefficient and a second modulation coefficient based on the current modulation mode in response to a switching instruction of switching from the current modulation mode to a target modulation mode; and combining the three-phase SPWM modulation wave, the first modulation coefficient, the SVPWM common-mode voltage, the second modulation coefficient and the DPWM common-mode voltage to generate a total modulation wave. According to the invention, non-stop switching of SVPWM and DPWM is realized, fast and stable neutral-point voltage and smooth transition of neutral-line current and three-phase current are ensured when two modulation modes are switched, and the smooth transition requirement of mode switching is met.