43 results about "Matrix converters" patented technology

The single-phase bidirectional single-stage isolation matrix converter comprises a pre-stage circuit and a post-stage circuit, and the pre-stage circuit comprises an LC filter on the power grid side, a pre-stage single-phase matrix conversion circuit and an LLC resonance circuit with a high-frequency transformer; the post-stage circuit comprises a post-stage conversion circuit and an output filter capacitor; the front-stage single-phase matrix conversion circuit comprises four bidirectional switch assemblies of a full-bridge structure. Each bidirectional switch assembly comprises two unidirectional controllable MOS tubes which are reversely connected in series, one end of each bidirectional switch assembly is connected to an L line or an N line of a power grid, and the other end of each bidirectional switch assembly is connected to the LLC resonance circuit. The rear-stage conversion circuit comprises a bidirectional MOS (Metal Oxide Semiconductor) tube bridge circuit and three high-frequency transformer secondary windings which are in triangular connection or star connection; and two end points of each secondary winding are respectively connected to the upper MOS tube and the lower MOS tube of the corresponding bridge arm and then are connected to output positive and negative ends. The converter has the advantages of high power density, low current harmonic, high power factor and the like, and is small in size, strong in anti-interference capability, wide in buck-boost range, and safe and reliable in commutation.

The present application relates to the technical field of power system relay protection, and particularly relates to a kind of offshore wind power through flexible low-frequency transmission system sending out line protection method, offshore wind farm is connected with modular multi-level matrix converter after being sent out by low-frequency through booster transformer, and is incorporated into large power grid after being frequency converted by M3C. When M3C of offshore wind farm fails, negative sequence current suppression and positive sequence current limiting strategy are adopted for fault ride-through, and relay protection devices are installed at both ends of low-frequency sending out line and communicate. The current sampling values before and after the fault on both sides of the line are reconstructed in phase space, and the difference between the permutation entropies is used to construct a protection scheme, which overcomes the problem of sensitivity reduction of traditional current differential protection for sending out line, reduces the amount of data interaction, and reduces the pressure of protection communication and the requirement of data synchronization. It is not affected by the control strategy of wind turbine and modular multi-level matrix converter at both ends of the line, fault ride-through mode, transition resistance and fault location, and has high reliability and good speed.

The application belongs to the technical field of power electronics, and discloses a double-vector model-free predictive control method for a reduced matrix converter and a related device, the method comprising: obtaining the AC side voltage, DC side voltage and DC side reference voltage data of the reduced matrix converter at a target moment, and calculating the inner loop reference current; obtaining the AC side current and switch input side current of the reduced matrix converter at an adjacent moment, calculating the system gain and system concentrated disturbance of the reduced matrix converter at the target moment, and combining the DC side current of the reduced matrix converter at the target moment to calculate the AC side current at the next moment corresponding to each switch state; and according to the inner loop reference current and the AC side current at the next moment, calculating the action time corresponding to the optimal vector and the suboptimal vector and determining the wave emission mode. The application realizes the model-free predictive control of the RMC, improves the anti-interference of the RMC, and reduces the AC side current ripple through the double-vector fixed-frequency control.

The invention provides a matrix converter low-frequency side outer ring reactive power control method and a related device, and the method comprises the steps: carrying out the matching processing based on the obtained operation scene data of the low-frequency side of a matrix converter, determining whether a reactive power control strategy is matched, and if the reactive power control strategy is matched, outputting a reactive power control strategy; if yes, performing coordinate conversion processing on three-phase voltage data and three-phase current data in the operation scene data to obtain voltage conversion data and current conversion data; calculating actual reactive power data based on the voltage conversion data and the current conversion data; performing deviation correction based on the actual reactive power and the obtained reactive power control target data to obtain a deviation correction signal, and performing feed-forward compensation on the reactive power control target data to obtain a feed-forward compensation signal; and performing fusion conversion processing on the feed-forward compensation signal and the deviation correction signal to obtain a control instruction signal, and adjusting the outer loop reactive power of the low-frequency side of the matrix converter based on the control instruction signal. The method improves the operation energy efficiency of the power system.

The invention discloses a unilateral matrix converter system for PMSM (permanent magnet synchronous motor) driving application. The unilateral matrix converter system comprises a three-phase input end, a unilateral matrix conversion module, a control module and an output end, the matrix transformation module is composed of a plurality of one-way IGBT power switches, switching is carried out between input phases through a time multiplexing strategy, and direct alternating current to alternating current energy transmission without an intermediate direct current link is achieved. The system adopts a most positive and negative phase selection algorithm and a V / f control strategy, and the output voltage and frequency are adjustable. Compared with a traditional AC-DC-AC system, the AC-DC-AC system does not need a high-capacity capacitor, is simple in structure and low in control complexity, has the energy conversion efficiency as high as 85-90%, has high reliability, light weight and modular expansion capability, and is suitable for aerospace and high-performance motor driving application.

An energy efficiency optimization control method for a single-stage isolation matrix converter is proposed. This method calculates the input current vector magnitude of a three-phase single-stage isolation matrix AC-DC converter, derives the duty cycle expression, minimizes the current stress in the three-phase single-stage isolation matrix AC-DC converter, achieves soft switching, derives the full-bridge phase shift angle expression based on the per-unit value of the input current, designs a single-loop voltage control circuit, does not sample the input current, achieves unity power factor, and keeps the input current sinusoidal.

The invention discloses a method for controlling a controlled impedance source of a modular multi-level matrix converter for low-frequency power transmission. According to the control method, on the basis of the idea of a controlled impedance source, the sub-module is equivalently designed to be a frequency division controlled impedance source, energy transfer between impedances is achieved, namely, a power frequency impedance source obtains energy from a power grid, a low frequency impedance source transmits power to a low frequency power transmission system, and therefore stable control over the capacitor voltage of the converter sub-module is guaranteed. And meanwhile, non-communication power frequency / low frequency grid-connected synchronization of the M3C system and self-synchronization among the sub-modules are realized by utilizing the passive synchronization characteristic of the controlled impedance source. The control structure is simple, the information flow of controller interaction and centralized communication can be obviously reduced, and expansion to more quantum modules is easy. According to the control method provided by the invention, the efficiency and safety of the flexible low-frequency power transmission system can be improved, and large-scale grid connection and frequency division power transmission of offshore wind power are realized.

The application discloses a kind of offshore low-frequency wind power transmission line longitudinal protection method and system, after fault occurs, the control strategy of permanent magnet direct drive wind generator net side converter and modular multilevel matrix converter is switched, protection device is collected negative sequence current on line two sides;Wavelet transform denoising is carried out to the negative sequence current collected on line two sides, and mode component is extracted in combination with variable mode decomposition;The energy of each mode component obtained is calculated, and the largest energy characteristic mode is selected;The Hilbert transform is carried out to the selected characteristic mode, and the negative sequence current envelope line is extracted;The slope of negative sequence current envelope line is fitted using least square method;The protection direction identification value of line two sides is determined according to the positive and negative of slope;The protection direction identification value of line two sides is transmitted to the opposite side, when logic criterion F =1 is judged as internal fault, otherwise as external fault, the application meets power grid specification, and the noise resistance is strong, internal fault is sensitive action, and the safety of system is guaranteed.

The application provides a matrix converter system and a control method thereof. The matrix converter system comprises a first output port and a second output port, at least two phases, N converter valve bridge arms, Q first magnetic elements, the i-th first magnetic element comprises N first ports, M second ports, the N first ports of the i-th first magnetic element are connected in series with one end of the N converter valve bridge arms respectively, the other end of the N converter valve bridge arms is connected with any one phase of the first output port respectively, and the other end of at least one converter valve bridge arm is connected with a phase of the first output port which is different from the phase of the first output port connected with the other end of the remaining converter valve bridge arms, and the M second ports of the i-th first magnetic element are connected with any one phase of the second output port respectively, and at least one second port is connected with a phase of the second output port which is different from the phase of the second output port connected with the remaining second ports. i i i i i i ​​​​​​

The application discloses a C-shaped iron core combined rotary loose coupling transformer, which comprises a fixed assembly and a rotary assembly. The fixed assembly comprises a fixed iron core, first and second fixed windings and a fixed side circuit; the longitudinal section of the fixed iron core is in the shape of a C letter, and the fixed iron core comprises a first fixed iron core, a second fixed iron core and a third fixed iron core; the rotary assembly comprises a rotary magnetic core, a rotary shaft, a rotary bearing, a rotary clamping groove, first and second radial rotary rings, first and second rotary windings and a rotating side circuit; the fixed iron core surrounds the outer periphery of the rotary shaft in the radial direction, and the fixed iron core and the rotary shaft are fixed by the rotary bearing; the first fixed winding and the second fixed winding are connected in series, and the first rotary winding and the second rotary winding are also connected in series. The C-shaped iron core combined rotary loose coupling transformer designed by the application reduces the axial size and weight, improves the power transmission capacity, and first connects the rotating side circuit with a matrix converter.

This application discloses a method and device for locating faults inside and outside the converter zone of a modular multilevel matrix converter, relating to the field of power electronics. The method includes: acquiring electrical quantity data of the converter zone; calculating the average capacitor voltage of each sub-converter on the power frequency side and low frequency side based on the sub-module capacitor voltage; determining whether a short-circuit ground fault has occurred inside / outside the converter zone based on the zero-sequence components of the power frequency AC voltage and the low frequency AC voltage; if not, determining whether a bridge arm short-circuit fault has occurred based on the sub-module capacitor voltage; if no bridge arm short-circuit fault has occurred, determining whether a phase-to-phase short-circuit fault has occurred inside / outside the converter zone based on the average capacitor voltage of each sub-converter on the power frequency side and low frequency side and the direction of the bridge arm current; if no fault has occurred, determining whether an open-circuit fault has occurred or whether the system is in normal operation based on the sub-module capacitor voltage. This application can distinguish between faults inside and outside the converter zone of a modular multilevel matrix converter, saving fault repair time.

The invention provides a bridge arm capacitor voltage control method, a bridge arm capacitor voltage control system and a storage medium. The bridge arm capacitor voltage control method comprises the following steps of performing coordinate conversion processing on an acquired bridge arm capacitor voltage instantaneous value of a matrix converter to obtain a voltage unbalance initial component; classifying the voltage unbalance initial components according to frequency characteristics, and configuring wave filtering parameters based on the voltage unbalance initial components with different frequency characteristics to perform ripple suppression processing to obtain voltage unbalance first components; inputting the voltage imbalance first component into a PI controller to generate a branch bridge arm power reference value; adjusting a branch bridge arm power reference value based on a phase transformation matrix of the matrix converter to generate a basic circulating current component and a ripple compensation circulating current component; performing fusion correction on the basic circulating current component and the ripple compensation circulating current component based on actual operation data to obtain a circulating current control instruction; and controlling the bridge arm capacitor voltage of the matrix converter based on the annular control instruction signal. According to the method, ripple accumulation is effectively avoided, and power switch tube loss is reduced.

The invention provides a method and a device for acquiring harmonic equivalent impedance of a modular multilevel matrix converter. The method comprises the following steps: defining positive sequence impedance and negative sequence impedance of an M3C in a three-phase symmetric operation state; applying a voltage disturbance in a set range of an M3C steady-state working point, and calculating a bridge arm reference voltage disturbance harmonic wave caused by the voltage disturbance in a dq coordinate system; obtaining a phasor form of a bridge arm reference voltage disturbance harmonic wave under an abc coordinate system through coordinate transformation; establishing a KCL equation for a bridge arm connecting the power frequency side and the low frequency side and carrying out linearization processing to obtain a disturbance voltage generated after the disturbance current is responded by the controller; simplifying a bridge arm voltage and current relation based on the disturbance voltage to obtain a unified disturbance voltage vector and disturbance current expression; and on the basis of the disturbance voltage vector, the current expression, the positive sequence impedance and the negative sequence impedance, the M3C positive sequence impedance seen from the power frequency side and the low frequency side is obtained through derivation by adopting per unit values.

The invention relates to the technical field of rectifiers, and provides an active clamping three-phase high-frequency link matrix rectifier and a pulse width modulation method thereof.The active clamping three-phase high-frequency link matrix rectifier comprises a three-phase alternating-current power supply, an LC input filter, a matrix converter, a high-frequency transformer, an uncontrolled rectifier bridge, an output filter and a load which are connected in sequence; an active clamping circuit is connected in parallel between the uncontrolled rectifier bridge and the output filter; each of the upper and lower bridge arms of each phase of the matrix converter comprises two switching tubes which are reversely connected in series. Based on the topology, the resonance process characteristics of the parasitic capacitance of the secondary side diode and the leakage inductance of the transformer are combined, and the high voltage stress generated by the leakage inductance of the transformer and the oscillation of the parasitic capacitance of the secondary side diode is suppressed by driving the auxiliary switch Saux on the premise of ensuring the output quality.

The invention discloses an M3C bridge arm voltage output capability determination method, system and device and a medium, and belongs to the technical field of power electronics, a single bridge arm loop model of a modular multi-level matrix converter M3C is established, a single bridge arm loop voltage expression is deduced, and a single bridge arm is formed by connecting a plurality of cascaded full bridge sub-modules and a bridge arm inductor in series; the method comprises the following steps: splitting a single-bridge arm loop voltage into a power frequency component and a low frequency component by neglecting a circulating current influence, and respectively establishing a power frequency side three-phase simplified loop and a low frequency side three-phase simplified loop; determining a power frequency side no-load modulation degree based on the voltage transmission characteristics of the power frequency side three-phase simplified loop; determining a low-frequency side no-load modulation degree based on the voltage transmission characteristics of the low-frequency side three-phase simplified loop; and obtaining a power frequency side phase voltage peak value and a low frequency side phase voltage peak value, and calculating the voltage output capability of the M3C bridge arm according to the power frequency side no-load modulation degree and the low frequency side no-load modulation degree.

The invention discloses a neural network prediction control method for a modular multilevel matrix converter, and belongs to the field of power electronics. The M3C is a power electronic topology for realizing direct alternating current-alternating current electric energy conversion, and has the advantages of modularization, flexible control, high electric energy quality and the like. A traditional FCS-MPC needs to traverse all possible switch state combinations in a control period, huge calculation burden is caused, meanwhile, the control precision of the FCS-MPC depends on the accuracy of a mathematical model, and robustness is poor. The invention provides a neural network predictive control method for M3C, and the method comprises the steps: collecting the input and output data of an FCS-MPC controller under different working conditions, carrying out the offline training of a neural network through the collected data, replacing the FCS-MPC with the trained network, and carrying out the real-time control, and also provides a delay compensation scheme of the method. According to the method, the online calculation burden of the digital controller is greatly reduced, and disturbance of M3C system parameters is introduced in the training process of the neural network, so that the neural network prediction controller has higher adaptability to parameter changes, and the robustness of the control system is further improved.

The invention belongs to the technical field of power electronics, and discloses a double-vector model-free predictive control method and related device for a simplified matrix converter, and the method comprises the steps: obtaining the AC side voltage, DC side voltage and DC side reference voltage data of the simplified matrix converter at a target moment, and calculating an inner ring reference current; obtaining the alternating current side current and the switch input side current of the simplified matrix converter at adjacent moments, calculating the system gain and the system concentrated disturbance of the simplified matrix converter at the target moment, and calculating the alternating current side current of the next moment corresponding to each switch state in combination with the obtained direct current side current of the simplified matrix converter at the target moment; according to the inner ring reference current and the alternating current side current at the next moment, action time corresponding to the optimal vector and the suboptimal vector is calculated, and a wave sending mode is determined. According to the method, RMC model-free predictive control is realized, the anti-interference performance of the RMC is improved, and the alternating current side current ripples are reduced through double-vector fixed-frequency control.

The invention relates to an active AC / DC converter (1) which is designed to generate a variably specifiable DC voltage and to output same at a DC voltage output (5). The AC / DC converter (1) is equipped with: an AC input (4) for the connection of a plurality of AC phases (usually three AC phases); a transformer (7); a matrix converter (6) connected downstream of the AC input (4); and a rectifier output stage (8). The matrix converter (6) is connected or connectable to each AC phase of the plurality of AC phases via a plurality of converter inputs (21) and is designed to generate, from an AC voltage having a first frequency applied to the AC input (4), an alternating current having a second frequency different from the first frequency and to output same via a plurality of converter outputs (9) to a plurality of primary-side connections of the transformer (7). The rectifier output stage (8) is connected on the input side to a secondary-side connection of the transformer (7) and on the output side to the DC voltage output (5) and is designed to convert an output AC voltage of the transformer (7) into the variably specifiable DC voltage.

The application discloses a kind of offshore wind power sending-out scene parameter optimization design method and equipment, belong to flexible low-frequency power transmission technical field, by constructing "initial parameter determination-preliminary electrical design-bridge arm reactance and submodule capacitance calculation-simulation check-closed loop iteration optimization" annular verification process, traditional static parameter calculation is combined with the depth of system dynamic electromagnetic transient simulation.This method can systematically verify and optimize the key parameters such as bridge arm voltage, inductance, submodule capacitance of modular multilevel matrix converter (M3C), ensure that the electrical stress of IGBT, capacitor and other core devices under rated and transient operating conditions is within the safety margin, while avoiding the increase in cost due to excessive reserve margin. Through iterative adjustment, the optimal balance between reliability, economy and performance is finally achieved in parameter design, which significantly improves the scientificity and engineering practicability of offshore wind power low-frequency sending-out system design.

The invention relates to a high-frequency link matrix rectifier and method based on a reverse blocking type IGBT, and belongs to the technical field of power electronic converters. The rectifier comprises an input LC filter, a reverse blocking type IGBT matrix converter, a high-frequency transformer, a diode rectifier bridge and an output LC filter. The reverse blocking type IGBT matrix converter is composed of nine reverse blocking type IGBT switch tubes which are divided into a positive electrode switch group, a negative electrode switch group and a middle switch group, and the primary side of the high-frequency transformer is of a double-winding structure with a center tap. The reverse blocking type IGBT matrix converter is controlled to be switched on and switched off through a three-wire SPWM modulation strategy, a corresponding switch combination is controlled according to an input voltage sector, positive and negative alternating high-frequency pulse voltage is synthesized on a primary winding of a transformer, and direct current is obtained after the high-frequency pulse voltage is isolated and rectified through the transformer. According to the invention, the commutation process is simplified through switch multiplexing, and the converter has the advantages of few switching devices, simple commutation, high reliability and high efficiency.

The utility model provides a matrix converter and AC-DC converter, and the matrix converter comprises a plurality of bridge arms, each bridge arm comprises a first active switch device, a second active switch device, a third active switch device and a fourth active switch device which are connected in series, the first end of the first active switch device is used for being electrically connected with an external load, and the first end of the fourth active switch device is used for being electrically connected with the load; the first ends of the second active switch device and the third active switch device are connected with each other and are used for being electrically connected with an external alternating current power grid, the plurality of first active switch devices share one isolation power supply, the plurality of fourth active switch devices share one isolation power supply, and the second active switch device and the third active switch device of each bridge arm share one isolation power supply. For the N-phase matrix converter, N + 2 paths of power supplies are needed, and compared with 2N paths of power supplies needed in the related technology, the design cost of the converter can be effectively saved, the design complexity is reduced, the size of the converter is reduced, and the integrated design of the system is facilitated.

The invention provides a relay protection method and device for a converter of a low-frequency power transmission system, and relates to the field of power equipment operation and maintenance, and the method comprises the steps: determining a current setting value corresponding to each relay protection function according to a topological structure and operation parameters of the low-frequency power transmission system; controlling a power frequency converter transformer valve side alternating-current circuit breaker and a low-frequency bus side alternating-current circuit breaker to carry out valve side connecting line protection according to the obtained valve side electrical parameters and the current setting value; and controlling a power frequency side alternating current circuit breaker and a low frequency side alternating current circuit breaker to perform converter valve protection according to the obtained electrical parameters of the valve body and the current setting value. The complete relay protection configuration method for the modular multilevel matrix converter in the low-frequency power transmission system can be provided, and the safety and stability of the low-frequency power transmission system are improved.

The invention discloses an M3C bridge arm reactance optimization method, system and device and a medium, and belongs to the technical field of power electronics, a mathematical model of a modular matrix converter M3C single bridge arm loop is established, a bridge arm voltage expression is deduced, and bridge arm voltage and bridge arm current are respectively split into a power frequency component and a low frequency component; setting a first proportion of the reactance voltage drop of the power frequency side bridge arm to the bridge arm voltage and a second proportion of the reactance voltage drop of the low frequency side bridge arm to the bridge arm voltage, wherein the first proportion is greater than the second proportion; determining a proportion relation between a power frequency component and a low frequency component in the bridge arm current; deducing the upper limit value of the reactance voltage drop of the bridge arm according to the first proportion, the second proportion and the ratio of the power frequency component to the low frequency component; and based on the upper limit value of the reactance voltage drop, combining the power frequency angular frequency, the low frequency angular frequency and the corresponding bridge arm current component, and calculating to obtain an optimized bridge arm reactance value.

To provide a power system for operating a motor in a thruster by using the output of another power supply or its converted output for the output of an AC power supply for outputting an AC insufficient for operating the motor in the thruster.SOLUTION: The switchboard 102 and the power storage system 101 are connected to each other so as to be capable of bidirectional AC output. The power storage system 101 can not only convert an AC output of the switchboard 102 into a DC output and output the DC output to the secondary battery 103, but also convert a DC output of the secondary battery 103 into an AC output and output the AC output to the switchboard 102. An AC power supply 104 is also connected to the switchboard 102. The switch board 102 synchronizes and combines the outputs of the AC power source 104 and the AC outputs sent from the power storage system 101, and outputs the combined outputs to either of the matrix converters 111a and 111b. The matrix converters convert the signals into signals having a cycle or the like suitable for the operation of the thrusters 112a and the motors in the 112b and then output the signals to the thrusters.SELECTED DRAWING: Figure 1

The invention provides a protection circuit of a matrix converter and a converter system. The protection circuit comprises a detection circuit, an OR gate, an AND gate, a first driving circuit and a second driving circuit, the input ends of the OR gate and the AND gate are respectively connected with the output end of the detection circuit, the output end of the OR gate is connected with the first driving circuit, and the output end of the AND gate is connected with the second driving circuit; the detection circuit is used for outputting a level jump signal when detecting that the state of the matrix converter is abnormal; the first driving circuit is used for determining a first control signal of the matrix converter based on a first logic operation result output by the OR gate so as to control conduction of the follow current switch tube; and the second driving circuit is used for determining a second control signal of the matrix converter based on a second logic operation result output by the AND gate so as to control other switching tubes except the follow current switching tube to be switched off. The protection circuit provided by the invention can be used for protecting the matrix converter in time under the condition of not damaging the device.

The invention introduces an active AC / DC converter (1) configured to generate a variably preset DC voltage and output it at a DC voltage output (5). The AC / DC converter (1) is equipped with an AC input (4) for connecting a plurality of AC phases (usually three AC phases), a transformer (7), a matrix converter (6) connected downstream of the AC input (4), and a rectifier output stage (8).The matrix converter (6) is connected or connectable to each AC phase of the plurality of AC phases via a plurality of converter inputs (21) and is configured to generate an AC current with a second frequency different from the first frequency from an AC voltage with a first frequency applied to the AC input (4) and to output it via a plurality of converter outputs (9) to a plurality of primary-side terminals of the transformer (7). The rectifier output stage (8) is connected on its input side to a secondary-side terminal of the transformer (7) and on its output side to the DC voltage output (5) and is configured to convert an output AC voltage of the transformer (7) into the variably preset DC voltage.

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.

This invention discloses a hybrid modulation method for a three-phase high-frequency isolated DC-AC matrix converter. The method first divides the power frequency cycle into 12 operating intervals based on the overlap and zero-crossing points of the three-phase AC voltages, and sorts the line voltages within each interval according to their absolute values. The maximum power factor angle is determined based on the amplitudes of the DC-side and AC-side voltages, and the AC-side current reference value and the limited reference power factor angle are obtained through power closed-loop control. In the modulation stage, dual-line voltage modulation is first attempted. Two line voltages are selected based on the instantaneous product of the voltage and current reference values, and the outward phase shift angle and the duty cycle of the second-largest line voltage are calculated. If the results meet the constraints, the drive signal is updated; otherwise, the mode switches to three-line voltage modulation. In this mode, three line voltages are selected, and the optimal ratio of the minimum and second-largest line voltage duty cycles is obtained by looking up a table based on the DC voltage and the reference power factor angle. The control parameters are then recalculated, and the drive signal is updated accordingly.

The invention discloses a single-stage matrix converter parallel current sharing control method based on virtual impedance decoupling, which comprises the following steps: firstly, embedding a virtual impedance control law with droop characteristics in a direct current voltage control loop of each single-stage matrix converter, and then generating an outer loop direct current voltage reference instruction through a direct current side droop control loop; then, based on voltage closed-loop control of the single-stage matrix converter, obtaining an addressing index for a three-dimensional lookup table, and further querying in the three-dimensional lookup table pre-stored in a digital controller to obtain a corresponding optimal basic switching moment parameter; and finally, zero sequence correction is generated through an alternating current side virtual impedance loop, the zero sequence correction is fused with the optimal basic switching time parameter, and a fused switching time sequence is used to generate a modulation signal.