A coaxial double-machine-based wind power frequency conversion fault-tolerant system and starting control method

Abstract

The present application relates to offshore wind power low-frequency power transmission technical field, especially to a kind of wind power frequency conversion fault-tolerant system and starting control method based on coaxial double machine, system includes: coaxial direct connection synchronous motor and synchronous generator, synchronous motor and synchronous generator are realized frequency conversion by pole pair number ratio;Three-phase transformer, including one three-phase input and two three-phase output, wherein three-phase input adopts delta connection, and three-phase output adopts star connection and delta connection respectively;Excitation module, including three input, four IGBT modules, two capacitor modules and two output;Starting module, including six input, four thyristor units, eighteen switch units, one inductance and three output;State switching switch module, including eight physical switches.Effectively solve the problem of large charging reactive power and high loss of wind power through sea cable transmission, fill the short board of power frequency ac transmission and flexible dc transmission.

Description

TECHNICAL FIELD

[0001] The present application relates to the offshore wind power low-frequency power transmission technical field, and particularly relates to a wind power variable frequency fault-tolerant system based on coaxial double machines and a starting control method. BACKGROUND

[0002] Building a new power system dominated by new energy is an important measure to achieve the "double carbon" strategy. China's offshore wind power resources are good and close to the load center. In recent years, it has developed rapidly and the added scale has ranked first in the world.

[0003] At present, offshore wind power transmission technologies include power frequency alternating current transmission, flexible DC transmission and low-frequency alternating current transmission technologies. In order to deal with the huge reactive power generated by the capacitive effect, the power frequency alternating current transmission technology usually adopts the method of configuring reactive compensation equipment to improve the transmission capacity. However, with the increase of transmission distance, the reactive compensation method has certain limitations. In comparison, the flexible DC transmission technology has greater transmission capacity because the DC submarine cable has no any alternating electromagnetic field to cause conductor, metal sleeve and armor loss. However, it needs to build a converter station platform on the sea, which is limited by investment and operation and maintenance costs, and is usually more suitable for power transmission in the offshore wind power scene. The low-frequency alternating current transmission technology can help reduce the reactive power consumption in the system and improve the transmission distance of the system. Moreover, only a frequency conversion station needs to be built on the shore, which greatly reduces the investment and construction cost compared with the offshore converter station platform of the flexible DC transmission technology.

[0004] Therefore, for the offshore wind power scene, the low-frequency alternating current transmission technology can improve the problems of large charging reactive power and high loss in the offshore wind power transmission, and fill the short board of the power frequency alternating current transmission and the flexible DC transmission.

[0005] The information disclosed in this BACKGROUND section is only intended to enhance the understanding of the general background of the present disclosure and is not intended to be a recognition or any form of suggestion that this information constitutes prior art. SUMMARY

[0006] The present application provides a wind power variable frequency fault-tolerant system based on coaxial double machines and a starting control method, which can effectively solve the problems in the background art.

[0007] In order to achieve the above purpose, the technical solution adopted by the present application is:

[0008] A wind power variable frequency fault-tolerant system based on coaxial double machines, the system comprises:

[0009] A coaxially connected synchronous motor and a synchronous generator, the synchronous motor and the synchronous generator realize frequency conversion through the pole pair number ratio;

[0010] Three-phase transformers, each of the three-phase transformers comprises one three-phase input end and two three-phase output ends, wherein the three-phase input end adopts delta connection, and the three-phase output ends respectively adopt star connection and delta connection;

[0011] Excitation modules, each of the excitation modules comprises three input ends, four IGBT modules, two capacitor modules and two output ends;

[0012] Starting modules, each of the starting modules comprises six input ends, four thyristor units, eighteen switch units, one inductor and three output ends;

[0013] State switching switch modules, the state switching switch modules comprise eight physical switches.

[0014] Further, the excitation modules adopt two-bridge-arm structure mode of the IGBT modules, and the IGBT modules comprise full-controlled power devices IGBTs;

[0015] The excitation modules are based on the principle that the average value of the full-controlled power devices IGBTs in a single control cycle is equal to a control reference value, wherein a control equation of the full-controlled power devices IGBTs is as follows:

[0016] ;

[0017] In the formula, R s represents an equivalent resistance of a system, i a represents a current of a first excitation input end A11, i b represents a current of a second excitation input end A12, d ap , d an respectively represent duty ratios corresponding to first and second IGBT modules B1 and B2, d bp , d bn respectively represent duty ratios corresponding to third and fourth IGBT modules B3 and B4, u ac represents a voltage between the first excitation input end A11 and a third excitation input end A13, u bc represents a voltage between the second excitation input end A12 and the third excitation input end A13, E m represents a difference between a target voltage and an actual voltage of first and second capacitors C1 and C2, △E m represents a difference between a target voltage and an actual voltage of the first capacitor C1.

[0018] Further, the excitation module realizes input and output voltage and current control through the drive signal of the IGBT module; the drive signal of the IGBT module can be generated through a clock generator, an adder, a subtractor, an integrator, a comparator, a data selector and an RS flip-flop;

[0019] The excitation module realizes in-phase and non-harmonic control of the input end AC voltage and current through the full-controlled power device IGBT control, thereby improving the power quality;

[0020] The excitation module realizes stable control of the output end DC voltage through the full-controlled power device IGBT control, thereby providing the synchronous generator or the synchronous motor with continuously adjustable excitation current.

[0021] Further, the four thyristor units of the starting module include:

[0022] The first thyristor unit, the second thyristor unit and the third thyristor unit each include six thyristor devices, and the six thyristor devices constitute a three-phase bridge-controlled rectification topology structure.

[0023] The fourth thyristor unit includes two thyristor devices, which are used for on-off control of a single-phase branch required in the starting process, thereby realizing redundant configuration of the starting module.

[0024] Further, the eighteen switch units of the starting module include:

[0025] Double-contact switch, each of the double-contact switches includes two synchronously-acting contacts, which are used for simultaneously changing the connection state of two electrical paths in one switching action;

[0026] Single-contact switch, each of the single-contact switches is used for independent on-off control of one electrical path;

[0027] The double-contact switches and the single-contact switches work cooperatively, and are used for, when the wind power frequency conversion fault-tolerant system based on the coaxial double machines is started, reconstructing the electrical connection relationship among the three-phase transformer output end, the thyristor unit and the stator winding of the synchronous generator or the synchronous motor according to the fault state of the four thyristor units of the starting module, wherein the number of the double-contact switches is greater than the number of the single-contact switches.

[0028] Further, the starting module is realized by a fourth thyristor unit in a thyristor redundant configuration, when any phase thyristor device in the first to third thyristor units is detected to be faulty, the switching unit is controlled to change the electrical connection relationship between the thyristor unit and the three-phase transformer output end, the synchronous generator or the synchronous motor stator winding input end, and selectively put the fourth thyristor unit into work to equivalently replace the faulty phase branch or bypass the faulty thyristor unit, and reconfigure the controllable rectification path of the starting module;

[0029] The starting module has at least one normal operation mode, nine single-phase fault tolerance operation modes when any of the first to third thyristor units has a single-phase fault, a bypass operation mode and a composite fault tolerance operation mode when any of the first to second thyristor units has at least two-phase faults, and 24 operation modes generated by combination of the operation modes.

[0030] A wind power starting control method based on coaxial double machines, the method comprising:

[0031] When the starting conditions are met, selecting a grid-side starting path or a fan-side starting path to execute, wherein the grid-side starting path is a starting path taking the synchronous generator as the main body of motor operation and the synchronous motor as the main body of power generation operation, and the fan-side starting path is a starting path taking the synchronous motor as the main body of motor operation and the synchronous generator as the main body of power generation operation;

[0032] Under the selected starting path, the motor operation main body works in motor mode, and the corresponding excitation module and starting module are excited and controlled in speed respectively to raise the speed to near the rated synchronous speed and establish the terminal voltage;

[0033] When the terminal voltage of the motor operation main body reaches the grid connection condition, the grid connection is completed, and the corresponding starting module of the motor operation main body is exited;

[0034] After the motor operation main body is connected to the grid, the power generation operation main body is driven by the motor operation main body to reach the rated synchronous speed, and the terminal voltage is established by the corresponding excitation module of the power generation operation main body to complete the grid connection;

[0035] After the two sides are connected to the grid, the working modes of the synchronous motor and the synchronous generator are adjusted to make the system enter the variable frequency power transmission operation state.

[0036] Further, when the grid-side starting path is selected, the motor running body is the synchronous motor, the power generation running body is the synchronous generator, and the synchronous motor is first connected to the grid-side power grid, and then the synchronous generator is connected to the wind turbine-side low-frequency power grid.

[0037] Further, when the grid-side starting path is selected, the motor running body is the synchronous motor, the power generation running body is the synchronous generator, and the synchronous motor is first connected to the grid-side power grid, and then the synchronous generator is connected to the wind turbine-side low-frequency power grid.

[0038] Further, in the excitation control process of the motor running body, the excitation control first adopts a constant magnetic voltage regulation control mode to establish the terminal voltage, and then switches to a constant voltage magnetic control mode; and after the motor running body meets the grid connection condition, the corresponding starting module is exited;

[0039] In the excitation control process of the motor running body, the excitation control first adopts a constant magnetic voltage regulation control mode to establish the terminal voltage, and then switches to a constant voltage magnetic control mode; and after the motor running body meets the grid connection condition, the corresponding starting module is exited;

[0040] After the two sides complete grid connection, the synchronous motor is adjusted to the motor running mode and the synchronous generator is adjusted to the power generation running mode.

[0041] Through the technical scheme of the application, the following technical effects can be achieved:

[0042] By setting the coaxial direct connection synchronous motor and synchronous generator, the excitation module and the starting module matched therewith, and the reconfigurable switch network, two selectable starting processes of the grid-side starting path and the wind turbine-side starting path are provided, and the excitation control mode switching and grid connection timing control are adopted in the starting process, so that when the power supply condition of any side meets, the terminal voltage can be first established and the grid connection is completed, then the other synchronous motor is driven to reach the rated synchronous speed and the grid connection of the other side is completed, finally the system is started quickly and reliably and enters the variable frequency power transmission running state, thereby effectively solving the problems of large charging reactive power and high loss in the wind power transmission through the submarine cable, and filling the short board of the power frequency alternating current power transmission and the flexible direct current power transmission.

[0043] The above description is only a summary of the technical scheme of the application, in order to more clearly understand the technical means of the application, the specific embodiments of the application can be implemented according to the content of the specification, and in order to make the above and other purposes, features and advantages of the application more obvious and easy to understand, the following specific embodiments of the application are described. BRIEF DESCRIPTION OF DRAWINGS

[0044] In order to make the technical solutions of the embodiments of the present application or the prior art clearer, the accompanying drawings needed in the embodiments or prior art description will be briefly introduced. Obviously, the accompanying drawings in the following description only represent some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without any creative effort.

[0045] Figure 1 It is a system topology diagram of a wind power frequency conversion fault-tolerant system based on coaxial double machines;

[0046] Figure 2 It is a structural schematic diagram of an excitation module;

[0047] Figure 3 It is a drive signal of an IGBT B1 and B2 of the excitation module;

[0048] Figure 4 It is a drive signal of an IGBT B3 and B4 of the excitation module;

[0049] Figure 5 It is a structural schematic diagram of a starting module;

[0050] The accompanying drawings: QS11-14, QS21-24 are state switching switch modules; A21-33 is an input end of the starting module; KA1-3, KB1-3, KC1-3, KD1-9 are switch units of the starting module; L is an inductor of the starting module; D21-23 is an output end of the starting module; G11-16 is a first thyristor unit; G21-26 is a second thyristor unit; G31-36 is a third thyristor unit; G41-42 is a fourth thyristor unit; B1-4 is an IGBT module. DETAILED DESCRIPTION

[0051] The technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments only represent some embodiments of the present application, rather than all the embodiments.

[0052] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in this description, the singular forms "a", "an" and "the" include plural references unless the context clearly dictates otherwise.

[0053] Embodiment one;

[0054] As Figure 1As shown, the application provides a wind power frequency conversion fault-tolerant system based on coaxial double machines, which comprises:

[0055] The coaxially connected synchronous motor and the synchronous generator realize frequency conversion through the ratio of the number of pole pairs;

[0056] The three-phase transformer comprises one three-phase input end and two three-phase output ends, wherein the three-phase input end is connected in a delta connection, and the three-phase output ends are respectively connected in a star connection and a delta connection;

[0057] The excitation module comprises three input ends, four IGBT modules, two capacitor modules and two output ends;

[0058] The starting module comprises six input ends, four thyristor units, eighteen switch units, one inductor and three output ends;

[0059] The state switching switch module comprises eight physical switches.

[0060] Specifically, the system is arranged between the offshore booster station and the low-frequency power grid of the wind turbine, and the core thereof is composed of a coaxial direct-connection synchronous motor and a synchronous generator; the synchronous motor and the synchronous generator are respectively configured with different pole pairs, so that they correspond to different electrical synchronous frequencies at the same mechanical speed, thereby realizing the required frequency conversion power transmission effect through the difference in pole pairs during system operation; specifically, one end close to the low-frequency side of the wind turbine is taken as the low-frequency electrical side, and one end close to the power grid side is taken as the power-frequency electrical side, and the energy conversion and transmission between different frequency power grids are completed through the electrical frequency difference between the two machines; in order to realize electrical isolation, phase adaptation and multi-path power supply, the three-phase transformer adopts a delta connection three-phase input end connected to the corresponding three-phase AC bus on the side, and two independent three-phase output ends are led out under the same core and winding system; the two three-phase output ends are respectively star-connected and delta-connected, and the star output end is preferably used to provide a three-phase power supply with a neutral point reference to facilitate voltage establishment and detection, and the delta output end is used to provide a three-phase power supply with stronger anti-unbalance capability and more robust harmonic circulation to adapt to starting and fault-tolerant conditions, thereby providing two sets of three-phase power supplies with complementary wiring forms for subsequent excitation and starting; in the excitation part, a three-terminal input and two-terminal output excitation unit structure is preferably adopted, wherein the three-terminal input is electrically connected with the three-phase output end of the transformer, a two-phase bridge full-control circuit composed of four IGBT power devices is used inside and cooperated with two capacitor energy storage branches to form direct current support and pulsation suppression, so that the excitation unit can realize rapid voltage building and stable voltage in the starting stage, and then switch to stable excitation and dynamic regulation in the grid-connected stage; specifically, the smooth lifting and fluctuation suppression of the terminal voltage of the synchronous motor can be realized through the control logic of establishing the terminal voltage first and then stabilizing the excitation by controlling the conduction strategy of the IGBT; in the starting part, a starting structure with six input ends and three output ends is preferably adopted, the six input ends are respectively connected to the three-phase power supplies provided by the two output wiring forms of the transformer and the necessary bypass or loop ends, four groups of thyristor device units, eighteen switch contacts and an inductor are arranged inside, wherein the first to third thyristor device units preferably each include six thyristor devices and form three groups of controllable rectification or commutation channels in a three-phase bridge controllable rectification connection mode, so as to provide controllable current and voltage support to the corresponding synchronous motor during starting and switching, and the fourth thyristor device unit preferably includes two thyristor devices and participates in on-off or phase control as an auxiliary branch, so as to perform equivalent position compensation or realize bypass reconstruction for the key phase branch when single-phase device abnormality occurs or the channel needs to be switched, thereby improving the availability and continuity of the starting channel.The eighteen switch contacts are preferably divided into two types of double-contact structure and single-contact structure, wherein the double-contact structure is preferably eleven, which is used for synchronously switching two electrical paths at one time to ensure the synchronization reconstruction of the multi-phase path, and the single-contact structure is preferably seven, which is used for independently turning on and off a single path to realize fine topology configuration, and the two structures cooperate to complete the connection relationship reconstruction between the transformer output end, the thyristor rectification channel, the synchronous motor stator loop and the inductor branch in different working states such as starting, grid connection, switching and fault tolerance; the inductor element is preferably connected in series in the starting current path, which is used for limiting the impact current, suppressing the commutation current ripple and reducing the current jump at the grid connection moment, so as to improve the starting stability and power quality; in addition, a state switching switch structure is also provided, which is preferably composed of eight physical switches, which are respectively used for selecting between the grid side starting path and the fan side starting path, switching between the starting state and the running state, and realizing the hard isolation and interlocking of the key loop during fault tolerance reconstruction; for example, when the grid side is selected as the first starting side, the synchronous generator can be first controlled to speed up in the electric mode and establish the terminal voltage to meet the grid connection condition, and then the grid connection is completed, and then the synchronous motor is driven to reach the rated synchronous speed and complete the grid connection on the other side; when the fan side is selected as the first starting side, the synchronous motor can be first controlled to speed up in the electric mode and establish the terminal voltage to complete the grid connection, and then drive the synchronous generator to complete the grid connection, and finally enter the stable variable frequency power transmission state through the adjustment of the working mode of the two machines; through the above differences in the pole pair number of the coaxial double machines, the delta input and star or delta double output of the three-phase transformer are realized to adapt the power supply, the IGBT controllable commutation excitation is realized to realize the fast voltage build-up and stable excitation, and the starting path containing the multi-thyristor channel and the multi-contact switch network realizes the controllable rectification or commutation and topology reconstruction, so that reliable starting and smooth grid connection can be realized under different starting side conditions, and in the preferred case, the continuous availability and operation reliability of the starting loop are improved through the auxiliary thyristor branch and switch reconstruction.

[0061] Through the technical scheme of the application, the coaxial and directly connected synchronous motor and synchronous generator, the excitation module and starting module matched therewith, and the reconfigurable switch switching network are provided, two selectable starting processes of the grid side starting path and the fan side starting path are provided, and the excitation control mode is adopted to switch and control the grid connection time sequence in the starting process, so that when the power supply condition of any side meets the requirement, the terminal voltage can be first established and the grid connection is completed, then the other synchronous motor is driven to reach the rated synchronous speed and the grid connection on the other side is completed, finally the system is started quickly and reliably and enters the variable frequency power transmission running state, thereby effectively solving the problems of large charging reactive power and high loss in the wind power transmission through the submarine cable, and filling the short board of the power frequency alternating current transmission and the flexible direct current transmission.

[0062] Further, as Figure 2As shown, the excitation module is a two-bridge-arm structure using IGBT modules, and the IGBT module includes full-controlled power devices IGBT;

[0063] The excitation module is based on the principle that the variable average value of the full-controlled power device IGBT in a single control cycle is equal to the control reference value, and the control equation of the full-controlled power device IGBT is:

[0064] ;

[0065] In the formula, R s represents the equivalent resistance of the system, i a represents the current of the first excitation input end A11, i b represents the current of the second excitation input end A12, d ap , d an respectively represent the duty ratios corresponding to the first IGBT module B1 and the second IGBT module B2, d bp , d bn respectively represent the duty ratios corresponding to the third IGBT module B3 and the fourth IGBT module B4, u ac represents the voltage between the first excitation input end A11 and the third excitation input end A13, u bc represents the voltage between the second excitation input end A12 and the third excitation input end A13, E m represents the difference between the target voltage and the actual voltage of the first capacitor C1 and the second capacitor C2, and △E m represents the difference between the target voltage and the actual voltage of the first capacitor C1.

[0066] As a preferred embodiment of the above, in order to enable the coaxial double-machine wind power frequency conversion fault-tolerant system to maintain a stable magnetic field and controllable excitation current within the grid-connected, switching and fault window, the excitation device adopts a circuit structure of two bridge arms and four full-controlled power devices IGBT: the three-phase input ends correspond to the first excitation input end A11, the second excitation input end A12 and the third excitation input end A13, respectively, A13 is preferably used as a common reference end or a backflow end, the first capacitor C1 and the second capacitor C2 are arranged on the DC side to form a voltage division and energy storage unit, and two output ends provide adjustable DC excitation to the synchronous motor rotor and the synchronous generator rotor; the four IGBTs are arranged in a two-bridge-arm manner, the first bridge arm is composed of a complementary switching pair of the first IGBT and the second IGBT, the second bridge arm is composed of a complementary switching pair of the third IGBT and the fourth IGBT, a hardware interlock and a dead time are arranged between each complementary switching pair to avoid short circuit, and in each control cycle, modulation is performed according to the idea that the equivalent average action of the IGBT in the control cycle is equal to the control reference value: the controller synchronously samples the A11 branch current i a , the A12 branch current i bThe voltage u between A11 and A13 ac The voltage u between A12 and A13 bc And sample the actual voltage of C1 and C2; then calculate the capacitor voltage deviation E m The preferred comprehensive quantity of the target voltage and actual voltage deviation of C1 and C2 is used to maintain the total voltage of the DC side and the energy margin, and the capacitor voltage deviation ΔE m The preferred target and actual deviation of C1 is used to suppress the imbalance of the two capacitor voltages and achieve voltage division balance, and the above deviation is equivalent to the resistance Rs and the sampled i a i b Commonly used to generate the duty cycle command of the current period; the key is the selection of the duty cycle and the linkage with the voltage polarity: when u ac is non-negative, the first bridge arm is preferably operated in the forward modulation state, i.e. with the duty cycle d ap as the main control quantity, the second IGBT is complementarily turned on to form a current channel, so that the equivalent driving effect of the A11 branch and E m and ΔE m are superimposed in a predetermined direction, thereby achieving synchronous regulation of the excitation energy injection of the A11 branch and the capacitor voltage deviation correction without changing the hardware topology; when u ac is negative, the first bridge arm is preferably switched to the reverse modulation state, i.e. with the duty cycle d an as the main control quantity, the opposite equivalent action direction is used to offset the control flip caused by the change of the voltage polarity, so that the regulation direction of the current and the capacitor deviation remains consistent, thereby avoiding the loss of control of the current or the further deviation of the capacitor voltage caused by the voltage commutation; similarly, when u bc is non-negative, the third IGBT is preferably used with the duty cycle d bp The second bridge arm is forward modulated to achieve the excitation energy injection of the A12 branch and the cooperative correction of E m , ΔE m ; when u bc is negative, the fourth IGBT is preferably used with the duty cycle d bn The second bridge arm is reverse modulated to ensure the continuity of the same control target when u bc commutes; in terms of implementation, the controller preferably limits the above duty cycle command to a safe range, such as setting a minimum pulse width, a maximum duty cycle, an overcurrent derating threshold, and sets a current rise rate limit and saturation protection for i a , i b .

[0067] Further, as Figure 3 and Figure 4As shown, the excitation module realizes input and output voltage and current control through the drive signal of the IGBT module; the drive signal of the IGBT module can be generated through a clock generator, an adder, a subtractor, an integrator, a comparator, a data selector and an RS flip-flop;

[0068] The excitation module realizes in-phase and non-harmonic control of the input AC voltage and current through the control of the full-controlled power device IGBT, thereby improving the power quality.

[0069] The excitation module realizes stable control of the output DC voltage through the control of the full-controlled power device IGBT, thereby providing continuous and adjustable excitation current for the synchronous generator or the synchronous motor.

[0070] As a preferred embodiment of the above embodiment, first, the AC voltage and AC current at the input end of the excitation device are synchronously sampled, and the DC side voltage and the excitation output current are sampled, and the sampled values enter the drive signal generation link after isolation and filtering. The drive signal generation link takes the fixed period provided by the clock generator as the common modulation beat of the whole link, so that the subsequent integral accumulation, comparison and decision, and trigger shaping are strictly aligned in time, thereby ensuring the repeatability and predictability of the switching action of the power device. Under this time base, the subtracter is used to construct two types of key deviation signals. One is the input current deviation, and the reference quantity is generated by the phase information of the input voltage, that is, the controller extracts the phase of the input voltage and forms the input current target waveform consistent with the phase, and then the actual input current is subtracted to obtain the deviation, which ensures that the input current is in phase with the input voltage from the control target level. The other is the DC voltage deviation, which is obtained by subtracting the DC voltage feedback value from the DC voltage set value, and is used to reflect whether the DC side energy is insufficient or excessive. The above-mentioned deviation signals are respectively sent to the integrator for accumulation adjustment. The integral of the input current deviation is preferably set to respond faster, so that the instantaneous waveform of the input current can be quickly corrected when the power grid is disturbed, the parameters drift or the load changes, so that it is as close to sinusoidal as possible and the harmonic components are suppressed. The integral of the DC voltage deviation is preferably set to respond more smoothly, so that the DC side energy balance is maintained when the excitation current is regulated or switched, and the DC voltage does not drop or overshoot. Subsequently, the adder superimposes the regulation quantity obtained by current shaping and the correction quantity obtained by DC voltage stabilization to form a unified modulation control quantity, so that the same set of drive pulses not only bears the task of input side current shaping, but also bears the task of DC side energy compensation. The superimposed weight is preferably self-adaptive to the running state, so as to ensure that when the DC side voltage is close to the lower limit, the DC voltage stability is preferentially maintained to ensure the continuity of excitation, and when the DC side is in the stable interval, the input current waveform quality is preferentially improved to reduce harmonic and reactive power exchange. The comparator compares the modulation control quantity with the reference waveform output by the clock generator, and outputs a high-low level sequence as the original decision result of the gate pulse. The data selector is used to select the corresponding decision channel under different input voltage polarity or different operating state, so that the control direction remains consistent when the voltage commutates, avoiding current out of control or further deviation of the DC voltage caused by the reversal of the adjustment direction. At the same time, it is also used for quick switching between DC stability priority and power quality priority to adapt to the fault tolerance switching window. Finally, the RS flip-flop shapes the set and reset of the comparator output, so that the gate drive pulse has clear boundaries and meets the mutual exclusion conduction requirement. Combined with the hardware interlocking and dead zone constraint of the power device, the risk of DC side short circuit caused by the simultaneous conduction of the upper and lower devices on the same bridge arm is prevented, and further constraints such as minimum pulse width, maximum duty cycle, input overcurrent fast limiting, DC overvoltage suppression, and excitation current rise rate limitation are applied at the pulse output end, so that the drive signal has both control performance and device safety in engineering implementation.By the above preferred control mode, the excitation device can make the fundamental component of the alternating current at the input end in-phase with the alternating voltage and the waveform distortion controlled, thereby reducing the reactive power exchange and harmonic injection and improving the power quality, while at the output end, the direct current voltage can be maintained stable and the continuously adjustable excitation current can be provided to the synchronous generator or synchronous motor, thereby realizing the continuity of the magnetic field stability and excitation supply in the working conditions such as grid connection, starting and fault-tolerant switching.

[0071] Further, as shown in Figure 5 The four thyristor units of the starting module include:

[0072] The first thyristor unit, the second thyristor unit and the third thyristor unit each include six thyristor devices, and the six thyristor devices constitute a three-phase bridge controllable rectification topology structure.

[0073] The fourth thyristor unit includes two thyristor devices, which are used for on-off control of a single-phase branch required in the starting process, so as to realize the redundant configuration of the starting module.

[0074] As a preferred embodiment of the above-mentioned embodiment, the AC input end of the three-phase bridge controllable rectifier topology is preferably connected to the three-phase power supply end of the six input ends of the starting device via multiple groups of physical switches, the DC output end of the three-phase bridge controllable rectifier topology is preferably merged into the starting DC bus or the pulsating DC power supply channel, and is matched with a series inductance to form a current limiting loop. The controller samples the three-phase voltage, the three-phase current, the DC side voltage, and the starting current, and implements a trigger strategy according to the starting stage division: in the initial stage of starting, the first thyristor unit is preferably only put into operation, the controller establishes a small current under weak conduction conditions, the inductance suppresses the current rising rate and reduces the shaft electromagnetic shock, and the DC side voltage is slowly lifted; when the synchronous motor speed rises and the starting torque needs to be increased, the second thyristor unit is preferably put into operation as a parallel power supply or segmented capacity increasing channel on the basis of maintaining the continuous output of the first thyristor unit, the controller coordinates the trigger time of the two groups of three-phase bridge controllable rectifier topologies, so that the equivalent output presents a smooth increase rather than a step change, thereby avoiding the current surge caused by power level switching; the third thyristor unit is preferably used as a backup rectifier channel or a transition channel, when it is detected that the first or second thyristor unit has abnormal conditions such as trigger failure, overheating, input imbalance leading to output distortion, etc., the controller can instruct to cut off the abnormal channel and put into the third thyristor unit to maintain uninterrupted starting, or provide a short-time transition between the main channel and the bypass to maintain the continuity of the DC side voltage and the starting current; unlike the above-mentioned three-phase bridge controllable rectifier topology, the two thyristor devices of the fourth thyristor unit are preferably set as a bidirectional controllable conduction structure for a single-phase channel, or as a controllable on-off structure for a DC branch, for completing pre-charging, pre-magnetization or DC side pre-establishment before starting, specifically, under the starting instruction, the related physical switches are first closed to connect the branch where the fourth thyristor unit is located, the DC side voltage is gradually lifted to a safety threshold through phase control, and then the first to third thyristor units are put into operation for main starting energy injection, thereby avoiding the impact on the inductance, bus and motor side at the power-on moment; further, in order to enhance the engineering implementability and fault tolerance, a unified synchronous reference and isolated drive are preferably used on the trigger drive side of the four thyristor units, and a pulse loss detection, redundant trigger and fast locking strategy is set, when the starting current exceeds the preset upper limit or the device temperature approaches the upper limit, the controller preferably reduces the output strength of the three-phase bridge controllable rectifier topology and maintains the inductance current limiting, and then according to the need, the fourth thyristor unit is used to implement delayed conduction or segmented bypass for the single-phase or DC key branch, so that the starting current is restored to the controllable interval.

[0075] Further, as shown in Figure 5 the eighteen switch units of the starting module include:

[0076] Double contact switches, each double contact switch includes two synchronously acting contacts for simultaneously changing the connection state of two electrical paths in one switching action.

[0077] Single-contact switches, each single-contact switch is only used for independent on-off control of one electrical path;

[0078] Double-contact switches work with single-contact switches to reconstruct the electrical connection relationship between the output end of the three-phase transformer, the thyristor unit and the stator winding of the synchronous generator or synchronous motor according to the fault state of the four thyristor units of the start module when the wind power frequency conversion fault-tolerant system based on coaxial double machines starts, wherein the number of double-contact switches is more than the number of single-contact switches.

[0079] As a preferred embodiment of the above, each double-contact switch preferably uses two groups of main contacts driven by the same operating mechanism, and the two-contact action timing is consistent or set as a controlled linkage of first breaking and then closing, for simultaneously changing the connection relationship between, for example, a certain output terminal of a three-phase transformer and a thyristor rectifier channel and the connection relationship between the output terminal and the motor winding terminal in one action, so that the energy injection path and the motor terminal are connected in the same switching window to complete the migration synchronously, avoiding abnormal voltage superposition or unexpected circulating current caused by switching one path first; each single-contact switch is preferably used for independent on-off control of a single path, typically arranged on the bypass branch, current-limiting inductor branch, pre-charging or pre-establishing branch, and fault isolation branch, so that the system can be individually put into or taken out of a certain branch as needed, and quickly cut off the local fault path when an anomaly is detected without having to exit the starting circuit as a whole; in terms of electrical connection organization, the eighteen switch units are preferably reorganized around three types of connection objects, one of which is the star output terminal and the delta output terminal of a three-phase transformer, the second is the three-phase controllable rectifier channel formed by the first to third thyristor units and the single-phase or direct-current branch controlled by the fourth thyristor unit, and the third is the lead-out terminal of the synchronous motor stator winding and the necessary auxiliary winding terminal or equivalent power receiving terminal. The switch units realize connection relationship switching in three working modes through different combination states; in the starting mode, a number of double-contact switches are preferably used to connect the specified output terminal of the three-phase transformer to the thyristor rectifier channel and simultaneously connect the controlled energy path after rectification to the motor winding, and single-contact switches are used to put in the current-limiting inductor path and control the timing of putting in the bypass branch according to the needs of the starting stage, thereby realizing the gradual establishment and suppression of the starting current; in the running mode, a number of double-contact switches are preferably used to decouple the starting energy injection path from the motor winding and simultaneously restore the main running connection relationship, so that the thyristor rectifier channel exits the main energy path, and single-contact switches are used to disconnect the current-limiting inductor branch and put in the necessary straight-through or bypass path, so that the system enters a low-loss stable running connection state; in the fault-tolerant mode, the linkage advantage of double-contact switches is preferably used to simultaneously complete the disconnection of the fault path and the connection of the standby path within one action, such as disconnecting the commonly used output terminal of the three-phase transformer from the motor power receiving terminal or starting rectification terminal and simultaneously switching to the standby output terminal, or disconnecting a certain thyristor channel from the main starting path and simultaneously connecting to the standby channel to maintain energy injection continuity, and single-contact switches are used to complete fine actions such as fault isolation, bypass establishment, and current-limiting recovery to reduce voltage drop and current surge at the switching instant.To ensure switching safety, the eighteen switch units are preferably provided with electrical interlocking and mechanical interlocking constraints, at least to ensure that at any time, the two output ends are not unexpectedly parallel, the rectifier output ends are not reversely connected, or the starting rectifier path and the running straight-through path are mis-parallel, while the control sequence preferably follows the principle of first disconnecting the path that may form a circulating current or short circuit and then closing the target path, and when necessary, a single-contact switch is first put into a current limiting path to form a buffer window, and then a double-contact switch completes the main connection migration when the current enters the controllable interval; Through the above preferred embodiments, the double-contact switch undertakes synchronous replacement of the key path to reduce the switching steps and improve the determinacy of topology reconstruction, the single-contact switch undertakes independent control of the local branch to improve the fine adjustment and fault isolation capability, and the number of double-contact switches is more than that of single-contact switches, so that the system can complete a larger range of connection reconstruction with fewer actions during mode switching.

[0080] Further, the starting module realizes a thyristor redundant configuration through the fourth thyristor unit. When any phase thyristor device in the first to third thyristor units is detected to have a fault, the electrical connection relationship between the thyristor unit and the three-phase transformer output end, the alternator or synchronous motor stator winding input end is changed by controlling the switch unit, and the fourth thyristor unit is selectively put into work to equivalently replace the faulty phase branch or bypass the faulty thyristor unit, thereby reconstructing the controllable rectifier path of the starting module.

[0081] The starting module has at least one normal operation mode; nine single-phase fault tolerance operation modes when any one of the first to third thyristor units has a single-phase fault; a bypass operation mode and a composite fault tolerance operation mode when any one of the first to second thyristor units has at least two-phase faults; and 24 operation modes generated by the combination of the operation modes.

[0082] As a preferred embodiment of the above embodiment, in a preferred embodiment, the thyristor fault tolerance operation in the starting stage realizes the rapid reconstruction of the connection relationship between the thyristor unit and the three-phase power supply through the on-off and contact position selection of the switches KA1, KB1, KC1, KA2, KB2, KC2, KA3, KB3, KC3, KD1 to KD9, and the available thyristor devices are controlled and triggered in a preset conduction sequence, so that when any phase branch of the first to third thyristor units has a fault, the fourth thyristor unit is selectively put into work to equivalently replace the faulty phase branch, or when two-phase and above faults occur, the bypass degradation operation is performed, and finally, twenty-four operation modes are formed by the combination of a normal operation mode, nine single-phase fault tolerance operation modes, and a bypass and composite fault tolerance mode for two-phase and above faults.

[0083] In the mode 1, the thyristor units 1, 2 and 3 are in normal operation, at this time, KA1, KB1, KC1, KA2, KB2, KC2, KA3, KB3, KC3, KD8 and KD9 are set to 1 contact, KD1, KD2, KD4, KD5, KD6 and KD7 are disconnected, KD3 is connected, the thyristor units 1, 2 and 3 are put into operation and the thyristor unit 4 is locked, the conduction sequence of the thyristor unit 1 is G11, G12, G13, G14, G15 and G16, the conduction sequence of the thyristor unit 2 is G21, G22, G23, G24, G25 and G26, and the conduction sequence of the thyristor unit 3 is G31, G32, G33, G34, G35 and G36;

[0084] The modes 2 to 4 are the fault-tolerant operation modes when the thyristor unit 1 has single-phase fault, when A-phase fault occurs, KA1 is set to 2 contact and KB1, KC1, KA2, KB2, KC2, KA3, KB3, KC3, KD8 and KD9 are set to 1 contact, KD1, KD5 and KD3 are connected and KD2, KD4, KD6 and KD7 are disconnected, G12, G13, G15 and G16 in the thyristor unit 1 and the thyristor units 2, 3 and 4 are kept in normal operation and G11 and G14 in the thyristor unit 1 are locked, the conduction sequence is adjusted to G41, G12, G13, G42, G15 and G16 of the thyristor unit 1 and the thyristor unit 4 alternately participating, the conduction sequence of the thyristor unit 2 is still G21, G22, G23, G24, G25 and G26, and the conduction sequence of the thyristor unit 3 is still G31, G32, G33, G34, G35 and G36; when B-phase fault occurs, KB1 is set to 2 contact, the rest of KA1, KC1, KA2, KB2, KC2, KA3, KB3, KC3, KD8 and KD9 are set to 1 contact, KD1, KD5 and KD3 are connected and KD2, KD4, KD6 and KD7 are disconnected, G11, G12, G14 and G15 in the thyristor unit 1 and the thyristor units 2, 3 and 4 are kept in normal operation and G13 and G16 in the thyristor unit 1 are locked, the conduction sequence is adjusted to G11, G12, G41, G14, G15 and G42, and the conduction sequence of the thyristor unit 2 and the thyristor unit 3 is unchanged; when C-phase fault occurs, KC1 is set to 2 contact, the rest of KA1, KB1, KA2, KB2, KC2, KA3, KB3, KC3, KD8 and KD9 are set to 1 contact, KD1, KD5 and KD3 are connected and KD2, KD4, KD6 and KD7 are disconnected, G11, G13, G14 and G16 in the thyristor unit 1 and the thyristor units 2, 3 and 4 are kept in normal operation and G12 and G15 in the thyristor unit 1 are locked, the conduction sequence is adjusted to G11, G42, G13, G14, G41 and G16, and the conduction sequence of the thyristor unit 2 and the thyristor unit 3 is unchanged;

[0085] The mode 5 to mode 7 are the fault-tolerant operation modes of the thyristor unit 2 when single-phase fault occurs, when A-phase fault occurs, KA2 is set to 2-contact and KA1, KB1, KC1, KB2, KC2, KA3, KB3, KC3, KD8, KD9 are set to 1-contact, KD4, KD6, KD3 are kept closed and KD1, KD2, KD5, KD7 are kept open, G22, G23, G25, G26 in the thyristor unit 2 and the thyristor units 1, 3, 4 are kept normal operation and G21, G24 in the thyristor unit 2 are blocked, the conduction sequence is adjusted to G41, G22, G23, G42, G25, G26 of the thyristor unit 2 and the thyristor unit 4 alternately participating, the thyristor unit 1 is G11, G12, G13, G14, G15, G16, and the thyristor unit 3 is G31, G32, G33, G34, G35, G36; when B-phase fault occurs, KB2 is set to 2-contact, the rest of KA1, KB1, KC1, KA2, KC2, KA3, KB3, KC3, KD8, KD9 are set to 1-contact and KD4, KD6, KD3 are kept closed and KD1, KD2, KD5, KD7 are kept open, G21, G22, G24, G25 in the thyristor unit 2 and the thyristor units 1, 3, 4 are kept normal operation and G23, G26 in the thyristor unit 2 are blocked, the conduction sequence is adjusted to G21, G22, G41, G24, G25, G42, the conduction sequence of the thyristor unit 1 and the thyristor unit 3 is unchanged; when C-phase fault occurs, KC2 is set to 2-contact, the rest of KA1, KB1, KC1, KA2, KB2, KA3, KB3, KC3, KD8, KD9 are set to 1-contact and KD4, KD6, KD3 are kept closed and KD1, KD2, KD5, KD7 are kept open, G21, G23, G24, G26 in the thyristor unit 2 and the thyristor units 1, 3, 4 are kept normal operation and G22, G25 in the thyristor unit 2 are blocked, the conduction sequence is adjusted to G21, G42, G23, G24, G41, G26, the conduction sequence of the thyristor unit 1 and the thyristor unit 3 is unchanged;

[0086] The mode 8 to mode 10 are the fault-tolerant operation modes of the thyristor unit 3 when single-phase fault occurs, when A-phase fault occurs, KA3 is set to 2-contact and KA1, KB1, KC1, KA2, KB2, KC2, KA3, KB3, KC3, KD8, KD9 are set to 1-contact, KD2, KD7, KD3 are closed and KD1, KD4, KD5, KD6 are opened, G32, G33, G35, G36 in the thyristor unit 3 and the thyristor units 1, 2, 4 are kept normal operation and G31, G34 in the thyristor unit 3 are blocked, the conduction sequence is adjusted to G41, G32, G33, G42, G35, G36 of the thyristor unit 3 and the thyristor unit 4 alternately participating, the thyristor unit 1 is G11, G12, G13, G14, G15, G16, the thyristor unit 2 is G21, G22, G23, G24, G25, G26; when B-phase fault occurs, KB3 is set to 2-contact, the rest of KA1, KB1, KC1, KA2, KB2, KC2, KA3, KC3, KD8, KD9 are set to 1-contact and KD2, KD7, KD3 are kept closed and KD1, KD4, KD5, KD6 are opened, G31, G32, G34, G35 in the thyristor unit 3 and the thyristor units 1, 2, 4 are kept normal operation and G33, G36 in the thyristor unit 3 are blocked, the conduction sequence is adjusted to G31, G32, G41, G34, G35, G42, the conduction sequence of the thyristor unit 1 and the thyristor unit 2 is unchanged; when C-phase fault occurs, KC3 is set to 2-contact, the rest of KA1, KB1, KC1, KA2, KB2, KC2, KA3, KB3, KD8, KD9 are set to 1-contact and KD2, KD7, KD3 are kept closed and KD1, KD4, KD5, KD6 are opened, G31, G33, G34, G36 in the thyristor unit 3 and the thyristor units 1, 2, 4 are kept normal operation and G32, G35 in the thyristor unit 3 are blocked, the conduction sequence is adjusted to G31, G42, G33, G34, G41, G36, the conduction sequence of the thyristor unit 1 and the thyristor unit 2 is unchanged;

[0087] The mode 11 and 12 are bypass operation modes of two-phase or three-phase fault, when two-phase or three-phase of thyristor unit 1 is fault, make KD8 put in 2 contact and make KA1, KB1, KC1, KA2, KB2, KC2, KA3, KB3, KC3, KD9 put in 1 contact, at the same time KD1 to KD7 are disconnected, make thyristor unit 2 and 3 normal operation and thyristor unit 1 and 4 are locked, the conduction sequence is G21, G22, G23, G24, G25, G26 of thyristor unit 2 and G31, G32, G33, G34, G35, G36 of thyristor unit 3; when two-phase or three-phase of thyristor unit 2 is fault, make KD9 put in 2 contact and make KA1, KB1, KC1, KA2, KB2, KC2, KA3, KB3, KC3, KD8 put in 1 contact, at the same time KD1 to KD7 are disconnected, make thyristor unit 1 and 3 normal operation and thyristor unit 2 and 4 are locked, the conduction sequence is G11, G12, G13, G14, G15, G16 of thyristor unit 1 and G31, G32, G33, G34, G35, G36 of thyristor unit 3;

[0088] The modes 13 to 24 are composite fault tolerant operation modes. When two-phase or three-phase faults occur in the thyristor unit 1, if a single-phase fault occurs in the thyristor unit 2, the KD8 is set to the 2-contact and the corresponding phase switch KA2 or KB2 or KC2 is set to the 2-contact according to which phase fault occurs, while the KD4 and KD6 are closed and the KD1, KD2, KD3, KD5, KD7 are opened, the thyristor unit 3 conducts in the sequence of G31, G32, G33, G34, G35, G36, so that the thyristor unit 2 retains healthy devices and forms an alternative conduction sequence with the thyristor unit 4. When the A-phase fault occurs in the thyristor unit 2, the switches KA1, KB1, KC1, KB2, KC2, KA3, KB3, KC3, KD9 are all closed to the 1-contact, the G22, G23, G25 and G26 in the thyristor unit 2 and the thyristor units 3 and 4 operate normally, the G21 and G24 in the thyristor unit 1 and the thyristor unit 2 are locked, and the conduction sequence of the thyristor units 2 and 4 is G41, G22, G23, G42, G25, G26. When the B-phase fault occurs, the switches KA1, KB1, KC1, KA2, KC2, KA3, KB3, KC3, KD9 are all closed to the 1-contact, the G21, G22, G24 and G25 in the thyristor unit 2 and the thyristor units 3 and 4 operate normally, the G23 and G26 in the thyristor unit 1 and the thyristor unit 2 are locked, and the conduction sequence of the thyristor units 2 and 4 is G21, G22, G41, G24, G25, G42. When the C-phase fault occurs, the switches KA1, KB1, KC1, KA2, KB2, KA3, KB3, KC3, KD9 are all closed to the 1-contact, the G21, G23, G24 and G26 in the thyristor unit 2 and the thyristor units 3 and 4 operate normally, the G22 and G25 in the thyristor unit 1 and the thyristor unit 2 are locked, and the conduction sequence of the thyristor units 2 and 4 is G21, G42, G23, G24, G41, G26.

[0089] In the case of two-phase or three-phase failure of the thyristor unit 1, if a single-phase failure occurs in the thyristor unit 3, the KD8 is placed at the 2-contact and the corresponding phase switch KA3 or KB3 or KC3 is placed at the 2-contact according to which phase failure occurs, while the KD2 and KD7 are closed and the KD1, KD3, KD4, KD5, KD6 are opened, so that the thyristor unit 3 retains healthy devices and forms a replacement conduction sequence with the thyristor unit 4, the thyristor unit 2 keeps G21, G22, G23, G24, G25, G26, if the A-phase failure occurs in the thyristor unit 3, the switches KA1, KB1, KC1, KA2, KB2, KC2, KB3, KC3, KD9 are all closed at the 1-contact, the G32, G33, G35 and G36 in the thyristor unit 3 and the thyristor units 2, 4 are normally operated, the G31, G34 in the thyristor unit 1 and the thyristor unit 3 are locked, and the conduction sequence of the thyristor units 3 and 4 is G41, G32, G33, G42, G35, G36; if the B-phase failure occurs, the switches KA1, KB1, KC1, KA2, KB2, KC2, KA3, KC3, KD9 are all closed at the 1-contact, the G31, G32, G34 and G35 in the thyristor unit 3 and the thyristor units 2, 4 are normally operated, the G33, G36 in the thyristor unit 1 and the thyristor unit 3 are locked, and the conduction sequence of the thyristor units 3 and 4 is G31, G32, G41, G34, G35, G42; if the C-phase failure occurs, the switches KA1, KB1, KC1, KA2, KB2, KC2, KA3, KB3, KD9 are all closed at the 1-contact, the G31, G33, G34 and G36 in the thyristor unit 3 and the thyristor units 2, 4 are normally operated, the G32, G35 in the thyristor unit 1 and the thyristor unit 3 are locked, and the conduction sequence of the thyristor units 3 and 4 is G31, G42, G33, G34, G41, G36;

[0090] In the case of two-phase or three-phase failure of thyristor unit 2, if a single-phase failure occurs in thyristor unit 3, by setting KD9 to 2 contact and according to which phase failure occurs, respectively setting corresponding phase switch KA3 or KB3 or KC3 to 2 contact, at the same time closing KD2, KD7 and opening KD1, KD3, KD4, KD5, KD6, the healthy devices of thyristor unit 3 are retained and form a replacement conduction sequence with thyristor unit 4, keeping the normal conduction sequence of thyristor unit 1 as G11, G12, G13, G14, G15, G16. If A-phase failure occurs in thyristor unit 3, switches KA1, KB1, KC1, KA2, KB2, KC2, KB3, KC3, KD8 are all closed to 1 contact, G32, G33, G35 and G36 in thyristor unit 3 and thyristor units 1 and 4 are normally operated, G31, G34 in thyristor units 2 and 3 are locked, and the conduction sequence of thyristor units 3 and 4 is G41, G32, G33, G42, G35, G36; if B-phase failure occurs, switches KA1, KB1, KC1, KA2, KB2, KC2, KA3, KC3, KD8 are all closed to 1 contact, G31, G32, G34 and G35 in thyristor unit 3 and thyristor units 1 and 4 are normally operated, G33, G36 in thyristor units 2 and 3 are locked, and the conduction sequence of thyristor units 3 and 4 is G31, G32, G41, G34, G35, G42; if C-phase failure occurs, switches KA1, KB1, KC1, KA2, KB2, KC2, KA3, KB3, KD8 are all closed to 1 contact, G31, G33, G34 and G36 in thyristor unit 3 and thyristor units 1 and 4 are normally operated, G32, G35 in thyristor units 2 and 3 are locked, and the conduction sequence of thyristor units 3 and 4 is G31, G42, G33, G34, G41, G36;

[0091] In the premise of two-phase or three-phase fault of thyristor unit 2, if single-phase fault occurs in thyristor unit 1, the healthy devices of thyristor unit 1 are reserved and the replacement conduction sequence is formed with thyristor unit 4 by setting KD9 to 2 contact and setting corresponding phase switch KA1 or KB1 or KC1 to 2 contact according to which phase fault occurs, and the conduction sequence of thyristor unit 3 is G31, G32, G33, G34, G35, G36, if A phase fault occurs in thyristor unit 1, switches KB1, KC1, KA2, KB2, KC2, KA3, KB3, KC3 and KD8 are all closed to 1 contact, G12, G13, G15 and G16 in thyristor unit 1 and thyristor units 3 and 4 are normally operated, G11 and G14 in thyristor unit 1 are locked, and the conduction sequence of thyristor units 1 and 4 is G41, G12, G13, G42, G15, G16; if B phase fault occurs, switches KA1, KC1, KA2, KB2, KC2, KA3, KB3, KC3 and KD8 are all closed to 1 contact, G11, G12, G14 and G15 in thyristor unit 1 and thyristor units 3 and 4 are normally operated, G13 and G16 in thyristor unit 1 are locked, and the conduction sequence of thyristor units 1 and 4 is G11, G12, G41, G14, G15, G42; if C phase fault occurs, switches KA1, KB1, KA2, KB2, KC2, KA3, KB3, KC3 and KD8 are all closed to 1 contact, G11, G13, G14 and G16 in thyristor unit 1 and thyristor units 3 and 4 are normally operated, G12 and G15 in thyristor unit 1 are locked, and the conduction sequence of thyristor units 1 and 4 is G11, G42, G13, G14, G41, G16.

[0092] The above-mentioned thyristor units 1, 2, 3 and 4 correspond to first to fourth thyristor units respectively.

[0093] Embodiment two;

[0094] Based on the same inventive concept as the wind power variable frequency fault-tolerant system based on coaxial double machines in the foregoing embodiment, the application further provides a wind power variable frequency fault-tolerant method based on coaxial double machines, which comprises the following steps:

[0095] When the starting condition is met, a grid-side starting path or a fan-side starting path is selected to execute, wherein the grid-side starting path is a starting path taking the synchronous generator as the main body of electric operation and the synchronous motor as the main body of power generation operation, and the fan-side starting path is a starting path taking the synchronous motor as the main body of electric operation and the synchronous generator as the main body of power generation operation;

[0096] Under the selected starting path, the electric operation body works in the electric mode, the corresponding excitation module and starting module are excited and controlled in speed respectively, the speed is raised to close to the rated synchronous speed, and the terminal voltage is established;

[0097] When the terminal voltage of the electric operation body reaches the grid-connected condition, the grid connection is completed, and the corresponding starting module of the electric operation body is taken out of operation;

[0098] After the electric operation body is connected to the grid, the generator operation body is driven by the electric operation body to reach the rated synchronous speed, and the terminal voltage is established by the corresponding excitation module of the generator operation body to complete the grid connection;

[0099] After the two sides complete the grid connection, the working mode of the synchronous motor and the synchronous generator is adjusted, and the system enters the variable frequency power transmission running state.

[0100] Specifically, the invention point of the starting control is focused on the optional execution of the dual starting path and the coordinated control of the two-side step-by-step grid connection and mode switching, that is, after the starting condition is met, a single path is not fixedly adopted, but the control device selects the grid-side starting path or the fan-side starting path for execution according to the information such as the availability of the grid-side voltage, the state of the auxiliary power supply on the fan side, the bus voltage level, the unit shutdown reason, and the starting allowed power, wherein the grid-side starting path preferably takes the synchronous generator as the electric operation main body, establishes a controlled magnetic field through its excitation supply, and performs current limiting and speed climbing control on the electric operation thereof through the starting loop, and the fan-side starting path preferably takes the synchronous motor as the electric operation main body, establishes a controlled magnetic field through its excitation supply, and performs current limiting and speed climbing control on the electric operation thereof through the starting loop, so that the grid is preferentially utilized to quickly establish the terminal voltage when the grid side is available, and the fan side is preferentially utilized to realize low-disturbance starting when the grid side is limited or needs to reduce external impact; under the selected path, the control device preferably organizes the starting process of the electric operation main body in stages, first enters the pre-excitation and pre-establishment stage, in which the magnetic field of the electric operation main body is established in a safe and controllable range through excitation supply, and the motor terminal voltage, motor current, DC side voltage, and key branch state of the starting loop are continuously monitored, at the same time, the starting loop is allowed to inject energy to the electric operation main body under weak conduction conditions, so that the motor current is gradually established at a limited slope and the torque jump is suppressed, and then enters the acceleration climbing stage, in which the control device preferably takes the speed closed loop as the main line, gradually increases the speed of the electric operation main body to approach the rated synchronous speed by adjusting the controlled conduction strength of the starting loop, and smoothly establishes the terminal voltage with the speed by dynamic adjustment of the excitation supply, and further refines the control of the frequency deviation and the phase deviation when approaching the synchronous interval to meet the synchronization condition before grid connection; when it is detected that the terminal voltage of the electric operation main body reaches the grid connection condition, the control device preferably performs pre-grid connection confirmation first, including that the terminal voltage amplitude is in the allowed interval, the frequency deviation is in the allowed interval, the phase difference is in the allowed interval, the grid connection point voltage is stable and the protection is not locked, etc., then issues a grid connection instruction to complete the grid connection, and after the grid connection is completed, the corresponding starting loop is exited in the order of first steady state and then exit, that is, the current and voltage are first maintained for a short time to smoothly transition and limit the current impact at the grid connection moment, and then the controlled path of the starting loop is gradually released and switched to the normal energy supply connection relationship after the grid connection, so as to reduce the loss and device thermal burden brought by the long-term load of the starting loop.After the electric operation main body is connected to the grid, the mechanical coupling characteristics of the coaxial direct connection are further utilized, the other synchronous motor is driven to the rated synchronous speed by the side which has been connected to the grid, and the control device preferably implements the grid connection preparation control on the other synchronous motor, including establishing the terminal voltage of the motor by the corresponding excitation supply after the speed of the other synchronous motor enters the synchronization interval, and performing voltage amplitude setting, at the same time, phase tracking and fine adjustment are performed according to the voltage phase of the grid connection point, so that the terminal voltage of the motor meets the grid connection condition, and the grid connection is completed, thereby realizing the step-by-step strategy of forming a stable electrical reference on the side of the grid connection first, and then driving the other side to be connected to the grid, avoiding the synchronization difficulty and impact risk caused by the simultaneous grid connection of the two sides; after the grid connection of the two sides is completed, the control device preferably enters the operation mode adjustment stage, the working mode of the synchronous motor and the synchronous generator is reconstructed, so that the system is switched from the starting and grid connection state to the variable frequency power transmission operation state, the reconstruction preferably includes determining the target power direction and excitation level of the two synchronous motors according to the wind wheel side power and the grid side power instructions, gradually adjusting the synchronous motor from the electric traction state to the controlled state matched with the system power flow, and adjusting the synchronous generator from the grid connection establishment state to the voltage support and power output state required for variable frequency power transmission, while maintaining the continuity of the terminal voltage and current and limiting the torque fluctuation during the switching process, so that the overall control effect of optional starting, smooth grid connection and rapid variable frequency power transmission operation after grid connection can be realized under different power supply conditions; wherein the speed close to the rated synchronous speed can be preferably set to 105% of the rated synchronous speed.

[0101] The above operation method in the application can effectively realize a wind power variable frequency fault-tolerant system based on coaxial double machines, and the technical effects are as described in the above embodiments, which will not be repeated here.

[0102] Further, when the grid side starting path is selected, the electric operation main body is a synchronous generator, the power generation operation main body is a synchronous motor, and the synchronous generator is connected to the grid side power frequency grid first, and then the synchronous motor is connected to the wind turbine side low frequency grid.

[0103] Further, when the wind turbine side starting path is selected, the electric operation main body is a synchronous motor, the power generation operation main body is a synchronous generator, and the synchronous motor is connected to the wind turbine side low frequency grid first, and then the synchronous generator is connected to the grid side power frequency grid.

[0104] Further, in the excitation control process of the electric operation main body, the excitation control first adopts the constant magnetic voltage regulation control mode to establish the terminal voltage of the motor, and then switches to the constant voltage magnetic control mode; and after the electric operation main body meets the grid connection condition, the corresponding starting module is exited.

[0105] In the excitation control process of the power generation operation main body, the excitation control first adopts the constant magnetic voltage regulation control mode to establish the terminal voltage of the motor, and then switches to the constant voltage magnetic control mode, without calling the corresponding starting module in the process.

[0106] After the completion of the grid connection on both sides, the synchronous motor is adjusted to the motoring mode and the synchronous generator is adjusted to the generating mode.

[0107] Similarly, the above optimization scheme of the system can also be respectively implemented to achieve the optimization effect corresponding to the method in Embodiment 1, which will not be described here again.

[0108] Although the present application has been described in connection with specific embodiments thereof, it will be evident for those skilled in the art that various modifications and combinations can be made without departing from the spirit and scope of the application. Accordingly, it is intended to cover all such modifications and variations of the application within the scope of the appended claims and their equivalents. Obviously, various modifications and changes can be made thereto without departing from the scope of the present application. It is intended that the application encompass all such modifications and changes as fall within the scope of the appended claims.

Claims

1. A wind power frequency conversion fault-tolerant system based on coaxial dual-machine, characterized in that, The system includes: A synchronous motor and a synchronous generator are directly connected on the same axis, and the synchronous motor and the synchronous generator achieve frequency conversion through the ratio of the number of pole pairs; Three-phase transformers, each of the three-phase transformers includes one three-phase input terminal and two three-phase output terminals, wherein the three-phase input terminal adopts a delta connection, and the three-phase output terminals adopt a star connection and a delta connection respectively; Each excitation module includes three input terminals, four IGBT modules, two capacitor modules, and two output terminals. Each of the startup modules includes six input terminals, four thyristor units, eighteen switching units, one inductor, and three output terminals; A state switching switch module, comprising eight physical switches; The startup module comprises eighteen switching units, including: A dual-contact switch, each of the dual-contact switches comprising two synchronously acting contacts for simultaneously changing the connection state of two electrical paths in a single switching action; Each of the single-contact switches is used to independently control the on / off state of only one electrical path; The dual-contact switch works in conjunction with the single-contact switch to reconstruct the electrical connection between the three-phase transformer output terminal, the thyristor unit, and the stator winding of the synchronous generator or the synchronous motor according to the fault status of the four thyristor units of the starting module when the wind power frequency conversion fault-tolerant system based on coaxial dual-machine is started. The number of dual-contact switches is greater than the number of single-contact switches. The starting module implements thyristor redundancy configuration through the fourth thyristor unit. When a fault is detected in any phase thyristor device in the first to third thyristor units, the switching unit is controlled to change the electrical connection between the thyristor unit and the output terminal of the three-phase transformer, the input terminal of the synchronous generator or the stator winding of the synchronous motor, and the fourth thyristor unit is selectively put into operation to provide equivalent replacement for the faulty phase branch or to bypass the faulty thyristor unit, thereby reconstructing the controllable rectification path of the starting module. The startup module has at least one normal operating mode; nine single-phase fault-tolerant operating modes when any of the first to third thyristor units experiences a single-phase fault; a bypass operating mode and a composite fault-tolerant operating mode when any of the first to second thyristor units experiences at least a two-phase fault; and 24 operating modes are generated by combining the operating modes.

2. The wind power frequency conversion fault-tolerant system based on coaxial dual-machine as described in claim 1, characterized in that: The excitation module adopts a two-bridge arm structure using the IGBT module, and the IGBT module includes a fully controlled power device IGBT. The excitation module is based on the principle that the average value of the fully controlled power device IGBT variables within a single control cycle equals the control reference value, wherein the control equation of the fully controlled power device IGBT is: ； In the formula, R s i represents the system's equivalent resistance. a i represents the current at the first excitation input terminal A11. b d represents the current at the second excitation input terminal A12. ap d an d represents the duty cycle of the first IGBT module B1 and the second IGBT module B2, respectively. bp d bn These represent the duty cycles of the third IGBT module B3 and the fourth IGBT module B4, respectively. ac This represents the voltage between the first excitation input terminal A11 and the third excitation input terminal A13, u bc E represents the voltage between the second excitation input terminal A12 and the third excitation input terminal A13. m ΔE represents the difference between the target voltage and the actual voltage of the first capacitor C1 and the second capacitor C2. m This represents the difference between the target voltage and the actual voltage of the first capacitor C1.

3. The wind power frequency conversion fault-tolerant system based on coaxial dual-machine according to claim 2, characterized in that, The excitation module controls the input and output voltage and current through the drive signal of the IGBT module; the drive signal of the IGBT module can be generated by a clock generator, adder, subtractor, integrator, comparator, data selector and RS flip-flop. The excitation module achieves in-phase and harmonic-free control of the input AC voltage and current through the fully controllable power device IGBT, thereby improving power quality. The excitation module achieves stable control of the output DC voltage through the fully controlled power device IGBT, providing a continuously adjustable excitation current for the synchronous generator or the synchronous motor.

4. The wind power frequency conversion fault-tolerant system based on coaxial dual-machine as described in claim 1, characterized in that, The four thyristor units of the startup module include: The first thyristor unit, the second thyristor unit, and the third thyristor unit each include six thyristor devices, and the six thyristor devices constitute a three-phase bridge controllable rectifier topology. The fourth thyristor unit includes two thyristor devices used to control the on / off state of the single-phase branch required during startup, thereby achieving redundant configuration of the startup module.

5. A wind power start-up control method based on coaxial dual-unit system, characterized in that, The method of using the wind power frequency converter fault-tolerant system based on coaxial dual-machine as described in claim 1 includes: When the startup conditions are met, either the grid-side startup path or the wind turbine-side startup path is selected for execution. The grid-side startup path is a startup path that uses a synchronous generator as the main motor for electric operation and a synchronous motor as the main generator for power generation operation. The wind turbine-side startup path is a startup path that uses a synchronous motor as the main motor for electric operation and a synchronous generator as the main generator for power generation operation. Under the selected start-up path, the electric operating body is put into electric mode, and excitation and speed control are performed by the corresponding excitation module and start-up module respectively, so that the speed is increased to close to the rated synchronous speed and the terminal voltage is established. When the terminal voltage of the electric operating unit reaches the grid connection condition, grid connection is completed, and the starting module corresponding to the electric operating unit is taken out of operation; After the electric operating unit is connected to the grid, the power generation operating unit reaches the rated synchronous speed under the drive of the electric operating unit, and the generator terminal voltage is established through the excitation module corresponding to the power generation operating unit to complete the grid connection. After grid connection is completed on both sides, the operating modes of the synchronous motor and the synchronous generator are adjusted to enable the system to enter the variable frequency power transmission operation state.

6. The wind power start-up control method based on coaxial dual-unit according to claim 5, characterized in that, When the grid-side start-up path is selected, the electric operating entity is the synchronous generator, the power generation operating entity is the synchronous motor, and the synchronous generator is first connected to the grid-side power frequency grid, and then the synchronous motor is connected to the wind turbine-side low-frequency grid.

7. The wind power start-up control method based on coaxial dual-unit according to claim 5, characterized in that, When the wind turbine-side start-up path is selected, the electric operating entity is the synchronous motor, the power generation operating entity is the synchronous generator, and the synchronous motor is first connected to the wind turbine-side low-frequency grid, and then the synchronous generator is connected to the grid-side power frequency grid.

8. The wind power start-up control method based on coaxial dual-unit according to claim 5, characterized in that, During the excitation control process of the electric operating unit, the excitation control first establishes the generator terminal voltage using a constant magnet voltage regulation control method, and then switches to a constant voltage magnet regulation control method; and exits the corresponding start-up module after the electric operating unit meets the grid connection conditions; During the excitation control process of the main power generation unit, the excitation control first uses constant magnetic voltage regulation control to establish the generator terminal voltage, and then switches to constant voltage magnetic regulation control. During the process, the corresponding start-up module is not called. After grid connection is completed on both sides, the synchronous motor is adjusted to electric operation mode and the synchronous generator is adjusted to power generation operation mode.

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