270 results about "Reactive power control" patented technology

The invention discloses a system and a method for analyzing stability and oscillation transmission of a network-forming converter system, and belongs to the technical field of virtual synchronous generator control, and the system comprises an active power control loop which takes an active power deviation value as input, and outputs a power angle of a VSG system through an active integration part and a feedback part; the reactive power control loop takes the reactive power deviation ratio as input, and outputs the voltage amplitude of the VSG system through an active integration part and a feedback part; according to the analysis method, whether each state variable is stable or not is judged firstly, and then the intensity of oscillation transmission between the state variables is judged. According to the method, the stability of the system can be evaluated more accurately, and the accuracy of system stability analysis under dynamic disturbance is ensured; an oscillation transfer effect function is introduced, and the mutual influence between different state variables is quantitatively analyzed; and the dynamic fluctuation range of each state variable in the system can be accurately evaluated.

The invention relates to the technical field of new energy power system control, and relates to a power decoupling method for cooperative control of voltage feed-forward compensation and adaptive virtual impedance. The method comprises the following steps: acquiring a power grid current and a power grid voltage, and calculating a reactive power measured value and an active power measured value of a power grid; virtual synchronous machine control is carried out, and a voltage feed-forward pre-compensation item is introduced into a reactive power control loop; calculating a reactive power control loop after VSG compensation, and obtaining VSG output side voltage and instantaneous angular frequency; self-adaptive virtual impedance control is adopted, a self-adaptive virtual impedance reference value is calculated, line impedance is dynamically adjusted, and a voltage loop input instruction voltage is calculated according to the line impedance; and adjusting the output performance of the inverter according to the instruction voltage. According to the invention, the problem of power fluctuation caused by VSG output voltage amplitude variation is effectively solved, and the dynamic influence of a power coupling item is weakened.

The invention discloses a virtual power plant voltage-reactive power coordination control method based on fusion of a graph neural network and deep reinforcement learning, and the method comprises the steps: explicitly introducing a topological structure of a power distribution network into the state representation of deep reinforcement learning in the form of graph data, and extracting and processing the graph structure data through the graph neural network; topological correlation and dynamic interaction among nodes in a power grid are accurately captured; and the extracted graph features and the traditional system state quantity are fused and input to the deep Q network for learning and decision making, so that the optimal coordination control of the distributed resources in the virtual power plant and the power distribution network equipment is output. The virtual power plant voltage-reactive power control method and device aim at solving the problem that in the prior art, perception on a power grid structure is insufficient, and the decision-making precision and robustness of virtual power plant voltage-reactive power control and the adaptability in a large-scale complex power distribution network are remarkably improved.

The invention relates to the technical field of power grid energy storage control, and particularly discloses a network construction type energy storage system and a control method thereof, and the system comprises a parameter collection module which obtains the voltage, frequency, short-circuit capacity ratio, phase angle and other power grid operation parameters of a grid-connected point in real time; the scene recognition module judges the power grid scene of the energy storage system according to the acquired parameters, wherein the power grid scene comprises a weak power grid scene, a fault scene, an oscillation scene, a phase angle jump scene and a power loss scene; the strategy library module stores control strategies for each scene, including active / reactive control, active / reactive decoupling, overload support, low-frequency oscillation suppression, phase angle stabilization and black start strategies; and the adaptive control module retrieves and calls a corresponding strategy from a strategy library according to an identification result, performs adaptive control on the energy storage system, and realizes intelligent response and stable support for a complex power grid environment. According to the invention, intelligent response and stable support of the energy storage system to a complex power grid environment are effectively realized.

Systems and methods for supplying power (both active and reactive) at a medium voltage from a DCSTATCOM to an IT load without using a transformer are disclosed. The DCSTATCOM includes an energy storage device, a two-stage DC-DC converter, and a multi-level inverter, each of which are electrically coupled to a common negative bus. The DC-DC converter may include two stages in a bidirectional configuration. One stage of the DC-DC converter uses a flying capacitor topology. The voltages across the capacitors of the flying capacitor topology are balanced and switching losses are minimized by fixed duty cycle operation. The DC-DC converter generates a high DC voltage from a low or high voltage energy storage device such as batteries and / or ultra-capacitors. The multi-level, neutral point, diode-clamped inverter converts the high DC voltage into a medium AC voltage using a space vector pulse width modulation (SVPWM) technique.

The invention discloses an energy storage type SOP black-start method, system and device based on improved VSG network construction control and a medium, and relates to the field of power grid black-start, and the method comprises the steps: an energy storage type converter MMC carries out the active and reactive control based on an improved VSG network construction control strategy; a non-fault side MMC is controlled to firstly close an isolation circuit breaker and slowly charge a direct-current capacitor, and when the voltage reaches a set threshold value, a current-limiting resistor is quitted; the fault side MMC is started by the same step as the non-fault side MMC; after synchronization is completed, AC circuit breakers between the non-fault side MMC and the feeder load and between the fault side MMC and the feeder load are closed respectively; based on the collected power grid power data, MMC output parameters are adjusted to meet the power grid connection condition, the control mode is switched according to the grid connection state, and the black start process is ended. And by arranging the black start resistor for current-limiting charging and sub-module voltage balance control, the phenomena of overcurrent and voltage unbalance in the black start process are avoided.

The invention discloses a variable frequency phase shift control DAB type single-stage inverter reactive power control method, system and device and a medium, and belongs to the technical field of power electronic converter control, and the method comprises the steps: setting a reactive power instruction as zero; when the reactive power instruction changes, the active power instruction and the reactive power instruction at the current moment are decomposed into a direct-axis current reference value and a quadrature-axis current reference value respectively; comparing the reference value with an actual sampling value, calculating an error compensation amount by using a PI controller, and determining the amplitude and phase of the AC side current according to the compensation amount; according to the amplitude and the phase of the voltage and the current, a DAB frequency conversion phase shift control curve is calculated; and generating a PWM (Pulse Width Modulation) signal according to the frequency conversion phase shift control curve obtained by calculation, wherein the PWM signal is used for driving a DAB inverter to carry out power transmission. According to the invention, on the premise that no extra hardware circuit is introduced, dynamic adjustment and accurate control of the instantaneous reactive power of the AC output side can be realized.

The invention discloses a time sequence fault current-limiting control method and system compatible with a grid-connected guide rule for a network construction type doubly-fed wind turbine generator, and the method comprises the following steps: freezing external power control when a low-voltage ride-through event of a power grid is detected at the initial stage of a fault, and suppressing transient overcurrent through dynamically adjusting the resistance component of virtual impedance; in the fault stable stage, an electromotive force compensation increment is calculated on the basis of grid-connected guide rule requirements at the moment 4 tau after the fault occurs; in the fault clearing stage, after it is detected that the fault is cleared, electromotive force compensation is stopped; gradually recovering the virtual impedance to a rated value through the dynamic coefficient A; in the fault recovery stage, active control and reactive control are recovered in sequence, power output is recovered to the level before the fault within one second, and meanwhile the virtual impedance amplitude is gradually recovered to the rated value along with the voltage phase difference; the voltage phase jump amplitude and the voltage drop amplitude determined by the method have high robustness.

The invention discloses a network construction type energy storage transient stability optimization control method and system considering reactive power degradation, and belongs to the field of power system transient stability control. According to the method, a network construction type energy storage grid-connected system model is constructed, a reactive power degradation effect dynamically triggered by a reactive power control loop is analyzed, and an active power loop optimization control equation is established according to the reactive power degradation effect. On the basis, a self-adaptive torque adjusting module is embedded in an active control module, and when it is monitored that the internal voltage of the inverter is reduced to 50% of a rated value, the reference torque is automatically and dynamically corrected so as to improve the power angle transient stability margin of the system. Simulation results show that the method can effectively restrain the instability of the network construction type energy storage power angle, obviously enhance the transient stability of the system, and guarantee the safe and reliable operation of the power grid.

The invention discloses a distributed power supply-based control method, system, equipment and medium, and relates to the technical field of distributed power supply control, and the method comprises the steps: collecting and preprocessing the real-time data of a distributed power supply, training a prediction model to optimize parameters, obtaining a load demand and power generation capability estimation, and adjusting the power based on a prediction result. Distributing active power according to a total load and a power contribution factor; setting a target power factor to calculate reactive power; monitoring voltage and load changes of a power grid in real time; dynamically selecting and adjusting a reactive power control strategy; and visualizing the running state and backing up the data to a database. Through closed-loop cooperation of data prediction, dynamic power control, value-oriented intelligent operation and maintenance and visual management, the stability, electric energy quality, operation and maintenance economy and management efficiency of the distributed power supply system are comprehensively improved.

The invention relates to the field of power grid voltage reactive power control, and discloses a three-level collaborative power grid voltage reactive power control architecture and control method.The architecture comprises an edge layer, a region layer and a master station layer, the edge layer is deployed at a key node of a power distribution network, and the region layer is deployed at a key node of the power distribution network; quick sensing and response to voltage fluctuation are realized by adopting thousand-time / second-level sampling and millisecond-level local calculation; the regional layer realizes cross-node reactive collaborative optimization based on a digital twinborn model and a federated learning framework; the master station layer constructs a voltage-reactive sensitivity matrix and dynamically adjusts the control weight of the edge layer. According to the control architecture and the control method, the advantages of centralized and distributed control are considered, the problems of response delay, collaborative conflict and data safety of traditional control are solved, the safety, the stability and the economical efficiency of the power grid in a high-proportion new energy access scene are effectively improved, and the control architecture and the control method are suitable for voltage reactive power control of the power grid in a complex region.

The invention provides a DRU-MMC sending end AC fault ride-through method and system, and the method comprises the steps: enabling a receiving end MMC to maintain the DC voltage to be constant in an outer loop fixed DC bus voltage / reactive power control mode during normal operation; sampling a sending-end AC power grid voltage effective value in real time, and calculating a deviation between the effective value and a nominal value; if the deviation shows that the voltage is lower than 90% of the nominal value (determining a fault), calculating a receiving end MMC direct current bus preset voltage instruction value according to the relation between the alternating current voltage and the direct current voltage; and the outer loop voltage control module is switched to a direct current bus preset voltage / reactive power control mode, and the direct current voltage is adjusted to a preset value by adjusting the input number of the sub-modules, so that closed-loop control is formed. According to the invention, continuous power transmission during a fault period can be realized, and the problem of off-network of new energy equipment caused by power congestion in a traditional scheme is avoided.

The invention discloses a short-time voltage fluctuation suppression method, device and equipment based on partition fluctuation evaluation, and relates to the technical field of power system control. The method comprises the following steps: under a minute-level time scale, taking the comprehensive minimization of active power loss, voltage fluctuation in adjacent time periods and reactive power regulation cost as a target, constructing a multi-period reactive power voltage optimization control model, and obtaining a reference voltage and a reference reactive power control quantity; a power system is partitioned through a modularity-based reactive voltage control robust partitioning algorithm, and influence areas which are mainly influenced by new energy fluctuation are identified on the basis of partitioning. And constructing a partition fluctuation evaluation index and setting a partition optimization event triggering mechanism. And under a short-time scale, constructing a subarea reactive voltage optimization control model based on quadratic programming by utilizing a subarea space decoupling technology, and executing subarea coordination optimization. And correcting the partition reactive voltage optimization control model through a model correction method based on multiple linear regression.

The invention provides a distributed power supply and energy storage reactive power control method considering interval coordination, and relates to the technical field of energy storage, and the method comprises the steps: dividing a power distribution network into a plurality of power distribution network regions according to the power loss, the power utilization demand mode, the load characteristics, and the power grid adjustment capability; collecting power loss data of branches in each power distribution network region; constructing a target power optimization model according to the power loss data and the power distribution coefficient corresponding to each power distribution network region; performing iterative solution on the target power optimization model by taking the total loss of the minimized current at each intersection as a target and taking branch node voltage constraint, reactive current stability constraint and equipment capacity constraint as constraint conditions to obtain a reactive power control strategy of the distributed power supply and energy storage; and according to the reactive power control strategy, controlling operation equipment in each power distribution network area. According to the scheme, control over the distributed power supply and the energy storage reactive power can be achieved through line monitoring, and then the voltage quality of the transformer area is improved.

The provided is a reactive power optimization method for a power system based on distributed interval optimization, including following steps: S1. constructing a first model, where the first model includes an interval reactive power optimization model of a power system with a high renewable energy penetration rate, and the interval reactive power optimization model includes an objective function, a first constraint, and a constraint of an interval power flow equation; S2. obtaining a first state variable interval based on the constraint of interval power flow equation and a distributed interval power flow algorithm; S3. Converting the first model based on the first state variable interval and a security limit definition method, and obtaining a second model, where the second model includes a deterministic optimization model; and S4. obtaining a voltage and reactive power control strategy based on the second model and a primal-dual interior point method.

This invention discloses a series-parallel hybrid power flow control method and system, applied in the field of power grid power flow control. The method includes: determining power grid demand information based on key operating data of the transmission network; determining the equivalent active power control quantity of UPFC, the equivalent power flow regulation quantity of SSSC, and the equivalent reactive power control quantity of STATCOM based on the quantification results of the demand information, the first constraint data of the series-parallel hybrid power flow control device, and the second constraint data of the transmission network; and injecting equivalent voltage and equivalent current into the transmission network through the series-parallel connection of UPFC, SSSC, and STATCOM to regulate the key operating data of the transmission network. When power flow control is required in the transmission network, this invention injects controllable voltage and current into the transmission network through UPFC, SSSC, and STATCOM to achieve adaptive control of power flow on transmission network lines.

The present application relates to the technical field of phase modifier control, in particular to a dynamic reactive power control method and system based on a phase modifier, comprising: acquiring real-time voltage deviation of the phase modifier during operation, and calling corresponding pole phase group rearrangement scheme; calculating magnetic density increment of end structure according to phase advance operation depth of the phase modifier, and activating end magnetic circuit optimization control logic when exceeding temperature rise intervention threshold, adjusting the magnetic circuit by simulating magnetic shielding, setting the material properties of the anti-magnetic steel, and introducing equivalent slot impedance; calculating end potential gradient according to the magnetic density increment, and activating end circuit blocking control logic when exceeding circulating current blocking threshold, blocking the circuit anomaly by inserting equivalent insulation sleeve, short-circuiting positioning rib, and laying equivalent insulation sheet; and coupling the output parameters of the two control logics with the pole phase group rearrangement scheme to generate dynamic reactive power distribution instructions. The method can solve the end temperature rise and circulating current discharge problems during the phase advance operation of the phase modifier, and improve the operation stability.

The invention relates to the technical field of power system application, and discloses a unified control method, system, equipment and medium for a flexible interconnection device based on a multi-voltage-level direct-current power distribution network, and the method comprises the steps that the flexible interconnection device is composed of two alternating-current / direct-current converters which are connected back to back, one side adopts direct-current voltage and reactive power control, and the other side adopts direct-current voltage and reactive power control; and the other side adopts active power and reactive power control. Decoupling control is carried out on d-axis current and q-axis current under a synchronous rotating coordinate system, a d-axis current reference value of a PQ side is superposed to a voltage outer ring output of a UdcQ side, and a unified current inner ring reference instruction is generated. According to the method, a feed-forward compensation item is introduced into a current inner loop to offset inter-axis coupling, continuous smooth adjustment of bidirectional power flow can be achieved without switching a control mode, voltage fluctuation of a direct-current bus is effectively restrained, and the dynamic response and global stability of a system are improved.

Embodiments of the application disclose a direct-drive wind turbine low-voltage ride-through control method and related equipment. The method comprises: generating a ride-through high-level signal to activate a low-voltage ride-through mode when a low-voltage ride-through trigger module detects that a current voltage value of a target power grid where a target direct-drive wind turbine is located is lower than a preset reference value; calculating a voltage drop depth according to the current voltage value and the preset reference value; a low-voltage period reactive power control module of a grid-side control system controls the target direct-drive wind turbine to output reactive power to the target power grid to support the power grid according to the voltage drop depth; and an active power control module of a machine-side control system controls output power of the target direct-drive wind turbine according to the voltage drop depth. The direct-drive wind turbine low-voltage ride-through control method overcomes the direct-current voltage overvoltage oscillation defect of the prior art and limits the machine-side electromagnetic power during the wind turbine low-voltage ride-through period from the source.

The invention discloses a power recovery control method and system after a fault of a DRU network-forming type fan, and the method comprises a voltage reference value control link which is used for obtaining a network-side voltage reference value; in the active power control link, based on the obtained grid-side voltage reference value, a d-axis voltage reference value of the output voltage of the converter of the DRU grid-forming type fan is obtained; the reactive power control link is used for obtaining a frequency control reference value; in the frequency control link, a q-axis voltage reference value of the output voltage of the converter is obtained based on the obtained frequency control reference value; and an inner loop voltage and current control link: based on the obtained d-axis voltage reference value and q-axis voltage reference value of the output voltage of the converter, obtaining a converter control voltage reference value. According to the method, the purpose of limiting the active power change rate in the fault recovery stage is achieved in a mode of voltage climbing after the fault.

The application provides a micro-grid group operation mode seamless switching control method based on hybrid active disturbance rejection, first, the differential of the output frequency / voltage of the non-restraint distributed power is introduced and synchronously tracked to the differential of the frequency / voltage of the restraint distributed power of the micro-grid group layer, the frequency / voltage disturbance rejection secondary control compensation of the non-restraint distributed power of the micro-grid layer is calculated, the frequency / voltage disturbance rejection recovery controller of each restraint distributed power of the micro-grid group layer is designed to ensure the reliable and stable operation of each region in the new operation mode; then, through the active / reactive power control of the micro-grid layer and the micro-grid group layer, the pre-synchronization controller is designed by combining the hybrid active disturbance rejection, so that the voltage and phase angle of the two sides of the interconnected switch are matched, the hybrid active disturbance rejection is introduced into each control layer of the micro-grid group, the frequency / voltage autonomous control and pre-synchronization compensation are realized based on the system disturbance estimation compensation, and the seamless transition between multiple operation modes is coped with.

The invention discloses an AC-DC integrated coupling operation control method for a medium-voltage power distribution system, and relates to the technical field of power distribution networks, and the method comprises the steps: carrying out the power flow analysis of an AC-DC system according to a system operation target, and obtaining a plurality of AC-DC coupling coefficients; obtaining a VSC direct current side voltage reference value by using the alternating current and direct current coupling coefficient and the VSC alternating current side grid connection point voltage effective value; obtaining an AC voltage reference value based on the VSC DC side voltage reference value in combination with AC side reactive power control; and obtaining an AC-DC integrated coupling operation control result by adopting park inverse transformation and a VSC modulation strategy according to the AC voltage reference value. According to the method, the problems of complex converter cooperative control and high system design, analysis and operation difficulty under traditional control are solved, meanwhile, the control of the VSC is unified by the control method, control modes do not need to be allocated to different VSCs under complex working conditions, and dynamic regulation and control of the system are realized while the control complexity is greatly reduced.

This invention discloses a coordinated control strategy for LCC and MMC in DC distribution networks. The strategy employs parallel operation of the LCC and MMC, with their DC sides connected to the same DC bus and simultaneously supplying power to the DC distribution network. When the transmission power is low or power flows in reverse, the LCC is deactivated, and the MMC assumes all the transmission power. When the transmission power is high, the LCC is activated and assumes most of the power. Considering the characteristics of LCC and MMC converter stations, the MMC uses constant DC voltage control and constant reactive power control, while the LCC uses constant DC current or constant DC power control. This invention utilizes the LCC to replace the MMC in assuming part of the transmission power, reducing the number and capacity of MMC devices in the DC distribution network. The coordinated control strategy for steady-state operation of LCC and MMC in the DC distribution network employs parallel operation of the LCC and MMC, with their DC sides connected to the same DC bus and simultaneously supplying power to the DC distribution network.

The invention discloses a reactive power dynamic regulation and control method and system for a transformer substation, and the method comprises the steps: collecting key parameters through a power grid sensor, and generating time series data; and then analyzing the response relationship of each node voltage to reactive power by using a voltage-controlled quantity sensitivity model S (U, Q) = U / Q, and further calculating the optimal reactive output target value of the SVG and the capacitor bank by using a dynamic programming algorithm. According to the reactive power dynamic regulation and control method and system for the transformer substation provided by the invention, the voltage-reactive power dynamic response characteristics are accurately grasped, so that the voltage and the power factor of the power distribution network are accurately regulated, the voltage fluctuation is effectively inhibited, and the operation stability and the economical efficiency of the power distribution network are improved; an intelligent and adaptive solution is provided for reactive power optimization of the power distribution network, and the method has important engineering application value.

The invention discloses a virtual synchronous machine control method for improving transient voltage inertia of a grid-connected inverter. The virtual synchronous machine control method comprises an active power control loop and a reactive power control loop with transient voltage inertia. On the basis of a traditional virtual synchronous machine control method, an inertia link is introduced into a reactive power control loop, and a reactive voltage loop is transformed into a second-order system from a first-order system so as to improve the dynamic response of an inverter when the voltage of a power grid drops. According to the invention, the change rate of the output voltage of the grid-connected inverter in the transient process can be effectively reduced, the power angle characteristic, the frequency characteristic and the voltage characteristic of the grid-connected inverter are improved, the negative influence caused by the voltage drop of the power grid is reduced, and the transient stability of the inverter is improved.

The application provides a control method of a direct current transmission system and the direct current transmission system. The control method comprises the following steps: obtaining a direct current voltage difference between a direct current voltage reference value of a sending end and a direct current voltage measurement value of the sending end; determining a direct current power reference value based on the direct current voltage difference, and taking the direct current power reference value as an active power limit of a converter of the sending end connected to the direct current transmission system; determining a smaller value between the direct current power reference value and a direct current power real-time value as a system power instruction value, and performing auxiliary valve control of the sending end based on the system power instruction value to perform reactive power control and harmonic elimination. The reactive power control comprises auxiliary valve outlet voltage control and angle control, the harmonic elimination comprises harmonic current elimination and harmonic voltage elimination, and the angle is a phase difference between the auxiliary valve outlet voltage and an alternating current voltage connected to the sending end. The control effect of the scheme is good, the control logic is simple, and the cost is low without adding an additional coordination control system.

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.

This invention belongs to the field of power grid voltage fault technology, specifically relating to a method and related apparatus for cascading fault ride-through control of a virtual synchronous generator. The control method includes the following processes: first, low-voltage fault ride-through control is performed, followed by high-voltage fault ride-through control; the low-voltage fault ride-through control is active power control, specifically employing a virtual damping adaptive control method to dynamically adjust the virtual damping coefficient, suppressing the power angle divergence of the virtual synchronous generator during low-voltage grid faults; the high-voltage fault ride-through control is reactive power control, specifically employing a reactive power droop coefficient adaptive adjustment control method to adjust the reactive power droop coefficient of the virtual synchronous generator, improving reactive power and output voltage during cascading faults. This solves the problem of fault ride-through of virtual synchronous generators during low grid voltage and high-voltage cascading faults.

The invention discloses a voltage control target adaptive generation method and system for high-proportion new energy power, and relates to the technical field of new energy voltage regulation and control, and the method comprises the steps: dividing operation modes based on a multi-dimensional operation characteristic database of a new energy station; introducing a piecewise linearization function to convert the ideal voltage control range; calculating and issuing a reactive power control reference quantity of the new energy station; and analyzing the reactive power control reference quantity limit. According to the method, typical working conditions such as a photovoltaic duck curve are accurately sensed, the precision, response speed and robustness of high-proportion new energy power grid voltage control are improved, the prominent problems of midday voltage rise, sudden drop at dusk and the like are inhibited, waste of adjustment resources and voltage out-of-limit risks are avoided, and the method is suitable for large-scale popularization and application. The method improves the new energy consumption capability and the power grid operation safety, and has a good application prospect and popularization value.

The invention discloses a double-M3C converter parallel control method for a flexible low-frequency power transmission system, the flexible low-frequency power transmission system comprises two parallel M3C converter stations, the two converters adopt master-slave control, one M3C converter is set as a master converter, the other M3C converter is set as a slave converter, the power frequency side is connected with a three-phase power supply, and the two M3C converter stations are connected in parallel. A low-frequency side receives new energy equivalent to a controlled current source. The method comprises the following steps: determining a master-slave control strategy according to parallel interaction characteristics of the two M3Cs; a grid-connected control method is adopted at the power frequency side of each M3C converter, an inner ring is controlled by alternating current, and an outer ring is controlled by stator module average capacitance voltage and fixed reactive power; the M3C low-frequency side of the master station adopts an alternating-current voltage control strategy; and the M3C low-frequency side of the slave station adopts a current tracking control strategy. According to the invention, high-precision and fast-dynamic-response current-sharing control can be effectively realized, and the parallel operation performance and reliability of the flexible low-frequency power transmission system in scenes of new energy collection and transmission and the like can be remarkably improved.