Optimization system and method for grid-forming wind turbine with uncontrolled rectification output scenario

Abstract

The application discloses an optimization system and method for a grid-connection type wind turbine connected with non-controlled rectification sending-out scene, and relates to the fields of new energy sending-out and power electronics technology. Compared with previous converter stations, the application solves the problems that the existing scheme adopts non-controlled rectification sending-out, needs to be configured with an additional reactive power compensation device, has a large volume, and makes it difficult to play the construction cost advantage of the sending end platform; the application also solves the problems that non-controlled rectification bridge sending-out exists a large proportion of harmonics, and influences the power quality of the sending end power grid; by combining the PV control algorithm and the Qf control algorithm of the grid-connection type wind turbine connected with non-controlled rectification power transmission with the optimization system, the capacity value of the compensation capacitor is reduced, the cost is saved, the land occupation area of the reactive power compensation facility is reduced, and the construction cost of the compensation device is saved; and the harmonic voltage and the harmonic capacitance on the valve side line of the converter transformer can be significantly reduced, which has application value for actual projects.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of new energy sending and power electronic technology, and in particular to an optimization system and method for a grid-connected wind turbine with uncontrolled rectification sending scenario. BACKGROUND

[0002] In order to achieve the goal of "double carbon" as soon as possible, China will vigorously develop renewable energy, but the existing converter stations have certain disadvantages: the MMC (Modular Multilevel Converter) converter station has a large occupation area, complex control and high construction cost; the LCC (Line Commutated Converter) converter station relies on grid commutation and has the risk of commutation failure, which will cause great economic loss; the two-level and three-level converter stations are not easy to realize in high-voltage direct current transmission because of high switching frequency and high requirements for power electronic devices.

[0003] Although the wind power through DRU (Diode Rectifier Unit) sending can greatly reduce the volume and weight of the sending end converter station, the existing scheme still has the following disadvantages: 1. Uncontrolled rectification sending needs to configure additional reactive power compensation devices, which are large in size, making it difficult to take advantage of the construction cost of the sending end converter platform. 2. Uncontrolled rectification bridge sending has a large proportion of harmonics, which affects the power quality of the sending end grid.

[0004] In order to solve the above problems, the present application proposes an optimization system and method for a grid-connected wind turbine with uncontrolled rectification sending scenario. SUMMARY

[0005] The purpose of the present application is to propose an optimization system and method for a grid-connected wind turbine with uncontrolled rectification sending scenario to solve the problems raised in the background art:

[0006] The existing scheme uses uncontrolled rectification sending, which needs to configure additional reactive power compensation devices, which are large in size, making it difficult to take advantage of the construction cost of the sending end converter platform; it also uses uncontrolled rectification bridge sending, which has a large proportion of harmonics, which affects the power quality of the sending end grid.

[0007] In order to achieve the above purpose, the present application adopts the following technical scheme:

[0008] The optimization system for a grid-connected wind turbine with uncontrolled rectification sending scenario comprises an improved parallel capacitor commutation converter and a system applied to the grid-connected wind turbine with uncontrolled rectification sending scenario, the improved parallel capacitor commutation converter comprises a converter transformer, a filter inductor, a parallel capacitor and a converter; the system applied to the grid-connected wind turbine with uncontrolled rectification sending scenario comprises a collection system for collecting wind turbine generators of each wind farm.

[0009] The improved parallel capacitor commutation converter is applied to a diode rectifier converter station (DRU), and the DRU converter station is connected with a topology of a system applied to a non-controlled rectification sending-out scene of a grid-constructed wind turbine.

[0010] Each wind farm wind turbine is connected with a nearest sending-end DRU converter station through a short-distance cable after being boosted by a booster transformer, and is transmitted to a receiving-end modular multi-level converter through a long-distance DC cable after being rectified by a converter, and is inverted into a power frequency AC receiving-end power grid; wherein, the sending-end DRU converter stations are connected through short-distance DC connection cables; the collected AC bus is connected to the AC inlet of the converter after being boosted by a converter transformer and then being connected in series with a filter inductor and in parallel with a capacitor, and a smoothing reactor is connected in series on the DC side; the sending-end DRU converter station is composed of m 12-pulse DRUs in cascade, wherein each bridge arm of the DRU is composed of a plurality of diodes connected in series.

[0011] Preferably, the operation frequency of the collected system is 50Hz power frequency.

[0012] The grid-constructed wind turbine adopts process control, i.e. PV control and Qf control.

[0013] The optimization method for the grid-constructed wind turbine non-controlled rectification sending-out scene includes the following steps:

[0014] The power operation characteristic analysis is performed on the system applied to the grid-constructed wind turbine non-controlled rectification sending-out scene, to obtain the correlation between the active power and the sending-end system voltage, the correlation between the reactive power and the frequency, and the gap in the reactive power, and the optimization system is used to fill the gap in the reactive power under the grid-constructed wind turbine non-controlled rectification sending-out scene; the circuit analysis is performed on the optimization system to obtain the reactive power compensation expression of the optimization system, and the parameters of the series filter inductor and the parallel capacitor are set according to the reactive power compensation expression; and the performance of the optimization system after parameter setting is evaluated.

[0015] Preferably, in the system applied to the grid-constructed wind turbine non-controlled rectification sending-out scene, an equivalent circuit model of a wind turbine grid-side converter outlet is built to obtain the active power and voltage expression of the wind turbine outlet as follows:

[0016]

[0017] Wherein: P is the active power generated by the wind turbine; Vdc is the DC side outlet voltage of the non-controlled rectification valve; N is the number of series 12-pulse non-controlled rectification bridges; Vac is the AC side voltage of the non-controlled rectification valve. is the impedance of the converter transformer;

[0018] The expression of the reactive power and the frequency at the outlet of the wind turbine is obtained as follows:

[0019]

[0020] wherein: is the reactive power emitted by the wind turbine; is the voltage of the sending end power grid; is the commutation overlap angle of the uncontrolled rectifier bridge; is the capacitance size of the equivalent reactive power compensation device;

[0021] The expression of the sending end power grid voltage is obtained by analyzing the sending end power grid voltage as follows:

[0022]

[0023] wherein: is the DC side voltage of the receiving end converter; is the transformer ratio of the uncontrolled rectifier valve converter transformer; is the equivalent resistance of the DC transmission line;

[0024] It is analyzed that the active power emitted by the wind turbine is related to the sending end power grid voltage; and the receiving end DC voltage has a clamping effect on the sending end power grid voltage, limiting the change range of the sending end power grid voltage; when the voltage amplitude is fixed, the frequency at the outlet of the wind turbine is related to the reactive power, so the wind turbine realizes frequency synchronization through reactive power synchronization control, and realizes the output voltage stability of the sending end wind farm through active power control.

[0025] Preferably, the following analysis is performed based on the outlet equivalent model of the grid-side converter of the optimization system:

[0026]

[0027] wherein, is the current output by the optimization system; is the current input into the optimization system; is the imaginary unit; is the harmonic number; is the angular frequency; is the bus voltage of the sending end power grid; is the transformer ratio of the uncontrolled rectifier valve converter transformer; is the series filter inductance of the optimization system; is the filter capacitance of the optimization system; represents the phase angle of the offset;

[0028] Neglecting the harmonic content of the bus voltage, the complex frequency of the above formula is transformed as follows:

[0029]

[0030] in, For transfer functions; For Laplace complex variables;

[0031] Define Indicators :

[0032]

[0033] The combined results are:

[0034]

[0035] in, Indicates the result after capacitor filtering Subharmonic current conversion rate.

[0036] Preferably, during the application of the optimized system, the control strategies for AC voltage, active power, reactive power, and frequency at the sending end during the wind power stable transmission phase are as follows:

[0037] The voltage of the sending-end power grid is controlled by the wind turbine units. Through active power control, the voltage of each wind turbine is generated. Shaft voltage reference value Phase generation of each wind turbine unit is achieved through reactive power synchronization control. , combined Reactive current reference value generated by the control loop To change The size ensures the reactive power balance of the system.

[0038] Preferably, the parameter tuning of the series filter inductor and the parallel capacitor is specifically as follows:

[0039] The active and reactive power in an AC system are calculated as follows:

[0040]

[0041] in, , These are the active power and reactive power of the AC system, respectively. This refers to the amplitude of the AC bus voltage. It is direct current;

[0042] Based on actual engineering needs, set =m% and the active power to be adjusted With reactive power The value of , where, To set parameters; and simultaneously set The optimal range of variation.

[0043] Optimization devices for grid-type wind turbines connected to uncontrolled rectified power output include:

[0044] Scenario Analysis Module: Used to analyze the power operation characteristics of grid-connected wind turbines connected to uncontrolled rectifier power transmission, and to find that there is a correlation between active power and the voltage of the sending-end system, a correlation between reactive power and frequency, and a reactive power gap.

[0045] Topology optimization module: used to perform topology optimization through the optimization system to fill the reactive power gap in the scenario of uncontrolled rectifier power transmission of the grid-type wind turbines; also to perform circuit analysis on the optimization system to obtain the reactive power compensation expression of the optimization system.

[0046] Parameter tuning module: used to tune the parameters of the series filter inductor and parallel capacitor in the system according to the reactive power compensation expression;

[0047] Performance evaluation module: Used to evaluate the performance of the optimized system after parameter tuning.

[0048] Preferably, in the scenario analysis module, an equivalent circuit model of the grid-side converter outlet of the wind turbine is built for the system applied in the scenario of grid-connected uncontrolled rectifier power transmission, and the expressions for the active power and voltage at the wind turbine outlet are obtained as follows:

[0049]

[0050] in: The active power generated by the wind turbine; To avoid controlling the DC-side output voltage of the rectifier valve; The number of twelve pulsating uncontrolled rectifier bridges connected in series; To avoid controlling the AC side voltage of the rectifier valve; The impedance of the converter transformer;

[0051] The expression for the reactive power and frequency at the wind turbine outlet is:

[0052]

[0053] in: The reactive power generated by the wind turbine; The voltage of the sending-end power grid; To control the commutation overlap angle of the uncontrolled rectifier bridge; The capacitance of the equivalent reactive power compensation device;

[0054] Analyzing the voltage of the sending-end grid, the expression is as follows:

[0055]

[0056] wherein: is the DC side voltage of the receiving converter; is the transformer ratio of the uncontrolled rectifier valve converter; is the equivalent resistance of the DC transmission line;

[0057] It is found by analysis that the active power generated by the wind turbine generator is related to the sending end grid voltage; and the receiving end DC voltage has a clamping effect on the sending end grid voltage, limiting the change range of the sending end grid voltage; when the voltage amplitude is fixed, the frequency at the outlet of the wind turbine generator is related to the reactive power, so the wind turbine generator realizes frequency synchronization through reactive power synchronization control and realizes the output voltage stability of the sending end wind farm through active power control;

[0058] In the topology optimization module, the following analysis is performed based on the equivalent model of the grid-side converter outlet of the optimization system:

[0059]

[0060] wherein, is the current output by the optimization system; is the current input to the optimization system; is the imaginary unit; is the harmonic order; is the angular frequency; is the sending end grid bus voltage; is the transformer ratio of the uncontrolled rectifier valve converter; is the series filter inductance of the optimization system; is the filter capacitance of the optimization system; represents the phase angle of the offset;

[0061] Neglecting the harmonic content of the bus voltage, the complex frequency of the above formula is transformed as follows:

[0062]

[0063] wherein, is the transfer function; is the Laplace complex variable;

[0064] The index is defined as :

[0065]

[0066] The following is obtained:

[0067]

[0068] wherein, represents the transformation rate of the 2nd harmonic current after capacitive filtering; ​

[0069] In the application process of the optimization system, the control strategy of the sending end AC voltage and active power, reactive power and frequency in the wind power stable sending stage is as follows:

[0070] The voltage of the sending end power grid is controlled by the wind turbine, and through active power control, the shaft voltage reference value of each wind turbine is generated. Through synchronous control of reactive power, the phase of each wind turbine is generated, and the reactive current reference value generated by the control link is combined to change the size, so that the system reactive power is balanced.

[0071] The parameter setting module sets the parameters of the series filter inductance and the parallel capacitor as follows:

[0072] The active power and the reactive power in the AC system are calculated as follows:

[0073]

[0074] Among them, , are the active power and the reactive power of the AC system respectively; is the AC bus voltage amplitude; is the DC current;

[0075] According to the actual engineering requirements, set =m% and the values of the active power and the reactive power to be set, wherein is the set parameter; at the same time, the best change range of is set.

[0076] A computer readable medium having computer program instructions stored thereon, the computer program instructions being executable by a processor to implement the method as described above.

[0077] Compared with the prior art, the present application provides an optimization system and method for a grid-connected wind turbine connected to a non-controlled rectification sending scene, which has the following beneficial effects:

[0078] The present application combines the PV control algorithm and the Qf control algorithm of the grid-connected wind turbine connected to the non-controlled rectification power transmission with the optimization system, reduces the capacitance value of the compensation capacitor, saves the cost, reduces the land occupation area of the reactive power compensation facility, and saves the construction cost of the compensation device; and can significantly reduce the harmonic voltage and the harmonic capacitance on the valve side line of the converter transformer, which has great application value in actual engineering. BRIEF DESCRIPTION OF DRAWINGS

[0079] Figure 1 Optimized system structure schematic diagram mentioned in embodiment 1 of the present application;

[0080] Figure 2 Equivalent circuit model diagram of fan grid-side converter outlet mentioned in embodiment 1 of the present application;

[0081] Figure 3 Control block diagram of fan grid-side converter mentioned in embodiment 1 of the present application;

[0082] Figure 4 System AC side voltage waveform simulation comparison diagram mentioned in embodiment 1 of the present application;

[0083] Figure 5 System required reactive power simulation comparison diagram mentioned in embodiment 1 of the present application;

[0084] Figure 6 Device schematic diagram mentioned in embodiment 2 of the present application. DETAILED DESCRIPTION

[0085] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments.

[0086] The present application combines the PV control algorithm and Qf control algorithm of the non-controlled rectification power transmission of the network-constructed fan with the optimized system, reduces the capacitance value of the compensation capacitor, saves the cost, reduces the land occupation area of the reactive power compensation facility, saves the construction cost of the compensation device, can significantly reduce the harmonic voltage and harmonic capacitance on the valve side line of the converter transformer, and has great application value for the actual engineering. Specifically, the following contents are included.

[0087] Embodiment 1:

[0088] Please refer to Figures 1-5The application is used for an optimization system and method in a grid-constructed wind turbine with non-controlled rectification sending-out scene, and an improved parallel capacitor commutation converter is applied to the optimization system in the grid-constructed wind turbine with non-controlled rectification sending-out scene, the optimization system comprising: power frequency alternating current energy output by a large-scale wind farm is collected to each field area boosting platform, each wind farm wind turbine is boosted by a boosting transformer and connected with a nearby DRU through a short-distance power frequency cable, and the electric energy is sent out by a sending-end converter, i.e. a sending-end DRU after rectification, and is transmitted to a receiving-end modular multi-level converter, i.e. a receiving-end MMC through a long-distance direct current cable, and is inverted into a receiving-end power frequency alternating current power grid. The sending-end distributed converter platform 1 and 2 are connected through a short-distance direct current connecting cable. The sending-end DRU adopts a 12-pulse DRU, which is formed by cascading two 6-pulse DRUs, and is phase-shifted through a converter transformer. The AC side inlet of each DRU converter valve is connected with an AC bus after being connected with a converter transformer T and a series filter inductor , and a filter capacitor is connected in parallel C , and a smoothing reactor is connected in series on the DC side .

[0089] Referring to Figure 2 the equivalent circuit model of the wind turbine grid-side converter outlet built, the active power expression of the wind turbine outlet is as follows:

[0090]

[0091] Among them: is the active power emitted by the wind turbine; is the DC side outlet voltage of the non-controlled rectification valve; is the number of series twelve-pulse non-controlled rectification bridges; is the AC side voltage of the non-controlled rectification valve; is the impedance of the converter transformer.

[0092] The expression of the reactive power and the frequency in this scene is:

[0093]

[0094] Among them: is the reactive power emitted by the wind turbine; is the sending-end power grid voltage; is the commutation overlap angle of the non-controlled rectification bridge; is the size of the equivalent reactive power compensation device capacitor;

[0095] The sending-end power grid voltage is analyzed, and the expression is:

[0096]

[0097] Among them: is the DC side voltage of the receiving-end converter; The ratio of the uncontrolled rectifier valve converter transformer; The equivalent resistance of the DC transmission line;

[0098] From the above analysis, it can be obtained that the active power of the wind turbine is greatly related to the sending end grid voltage. The sending end DC voltage has a clamping effect on the sending end grid voltage, so that the amplitude of the sending end grid voltage changes little. When the voltage amplitude is fixed, the frequency at the outlet of the wind turbine is related to the reactive power, so the reactive power can be used for frequency regulation.

[0099] Reference Figure 3 , the sending end AC voltage and active power, reactive power and frequency control strategy as follows:

[0100] The voltage of the sending end grid is controlled by the wind turbine, which can generate the shaft voltage reference value of each wind turbine through active power control, and the phase of each wind turbine through reactive power synchronous control, combined with the reactive current reference value generated by the control link to change size, so that the system reactive power balance, so as to maintain the sending end AC voltage frequency stability.

[0101] Further introduce the influence of the optimization system on the system, can refer to the equivalent model of the grid side converter outlet Figure 2 , corresponding analysis:

[0102]

[0103] Among them, is the current output by the optimization system; is the current input to the optimization system; is the imaginary unit; is the harmonic number; is the angular frequency; is the sending end grid bus voltage; is the ratio of the uncontrolled rectifier valve converter transformer; is the series filter inductance of the optimization system; is the filter capacitance of the optimization system; denotes the offset phase angle;

[0104] Neglecting the harmonic content of the bus voltage, the complex frequency of the above formula is transformed as follows:

[0105]

[0106] Among them, is the transfer function; For Laplace complex variables; refer to Figure 4 The voltage waveform before the optimization system was applied in the figure is relatively coarse. The voltage waveform after the optimization system was applied is similar to that of the business area and is smoother. It can be seen that the optimization system has a significant effect on filtering out the corresponding harmonics.

[0107] Define Indicators The transformation rate of the nth harmonic current after capacitor filtering is defined as:

[0108]

[0109] By combining the two equations, we can obtain:

[0110]

[0111] As mentioned above, harmonic phasors Since it is approximately zero, it can be ignored, therefore:

[0112]

[0113] The smaller the value, the smaller the amplitude of the nth harmonic. Since a 12-pulse uncontrolled rectifier is used for power transmission in this scenario, the harmonic order in the AC system is 12k ± 1, with the lowest order being 11th. Therefore... It is an important indicator for evaluating the harmonic content of a system.

[0114] To tune and optimize the filter inductor and filter capacitor of the system, we need to obtain the formulas for calculating the active and reactive power in the AC system:

[0115]

[0116] in, , These are the active power and reactive power of the AC system, respectively. This refers to the amplitude of the AC bus voltage. It is direct current.

[0117] The specific parameter design method is as follows: (1) In order to ensure good AC and DC harmonic characteristics, let =m%, can be set according to actual project needs. For example, in this scenario, n can be set to 11 and m can be 1. (2) According to the actual needs of the project, design the active power P and reactive power Q that need to be set, for example, P is 1000MW and Q is 0MVar. (3) Considering the volume and cost, LC should not be too large. Among them, (1) and (2) are the main constraints, and (3) is the secondary constraint. The main constraints need to be met first, and the secondary constraints should be met as much as possible under this premise to improve the system performance.

[0118] The size of the parallel capacitor after setting and the size of the direct parallel capacitor are compared, and the system parameters are taken as P = 1000 MW, Q = 0 MVar, the DC voltage is taken as 500 kV, and the DC current is taken as 2 kA. The calculated required capacitor value in the optimized system is 13.344 If the direct parallel capacitor is used, referring to the active power and reactive power relationship of the uncontrolled rectifier, the calculated size of the parallel capacitor required at this time is 25.272 It can be seen that the capacitor in the system is smaller than the direct parallel capacitor, which can save costs.

[0119] Finally, the power operation characteristics of the optimized system applied to the grid-connected wind turbine connected to the uncontrolled rectifier sending-out scenario are analyzed, which can be referred to Figure 5 As can be seen from the figure, after the application of the optimized system, the power operation characteristics are greatly improved, which is conducive to the stable operation of the system.

[0120] Therefore, a grid-connected control technology for new energy connected to an uncontrolled rectifier is proposed. The topology structure is that multiple groups of grid-connected wind turbines are collected on an AC bus and sent out through an uncontrolled rectifier bridge, and the receiving end adopts an MMC inverter for grid connection. Compared with existing projects, the volume and weight of the sending end converter station can be significantly reduced, the land area is small, a large amount of cost can be saved, and it is expected to become a better choice for new energy sending out.

[0121] Embodiment 2:

[0122] In addition, the embodiment of the present application also provides an optimization device for a grid-connected wind turbine connected to an uncontrolled rectifier sending-out scenario, the structure of the device is as shown in Figure 6 The device includes a scene analysis module 1, a topology optimization module 2, a parameter setting module 3, and a performance evaluation module 4. The device executes the method of embodiment 1.

[0123] Embodiment 3:

[0124] The method and / or embodiments in the embodiments of the present application can be implemented as a computer software program. For example, the embodiments of the present disclosure include a computer program product comprising a computer program carried on a computer readable medium, the computer program comprising program code for executing the method shown in the flowchart. When the computer program is executed by a processing unit, the above-mentioned functions defined in the method of the present application are executed.

[0125] The above merely describes preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art, according to the technical solution and inventive concept of the present application, makes equivalent replacement or change within the technical range disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. A method for optimization in a grid integrated wind energy generator with uncontrolled rectifier fed scenario, characterized in that, The method is based on an optimization system applied to a grid-connected wind turbine with uncontrolled rectification sending-out scenario, the optimization system comprising: an improved parallel capacitor commutation converter and a system applied to the grid-connected wind turbine with uncontrolled rectification sending-out scenario, the improved parallel capacitor commutation converter comprising a converter transformer, a filter inductor, a parallel capacitor and a converter; the system applied to the grid-connected wind turbine with uncontrolled rectification sending-out scenario comprising a collection system for collecting wind turbines of each wind farm; The improved parallel capacitor commutation converter is applied to a diode rectifier converter station (DRU), and the DRU is connected to the topology of the system applied to the grid-connected wind turbine with uncontrolled rectification sending-out scenario as follows: The wind turbines of each wind farm are collected to a sending-end collection system through respective converters and short-distance AC cables, the wind turbines of each wind farm are connected to the nearest sending-end DRU converter station through short-distance cables after being boosted by respective booster transformers, and are transmitted to a receiving-end modular multi-level converter through long-distance DC cables after being rectified by the converter, and are inverted into a power frequency AC receiving-end power grid; wherein the sending-end DRU converter stations are connected through short-distance DC connection cables; the collection AC bus is connected to the AC inlet of the converter through the converter transformer, the series filter inductor and the parallel capacitor, and the DC side is also connected to a smoothing reactor in series; the sending-end DRU converter station is composed of m 12-pulse DRUs in cascade, wherein each bridge arm of the DRU is composed of a plurality of diodes in series. The optimization method comprises the following steps: The power operation characteristic analysis of the system applied to the grid-connected wind turbine with uncontrolled rectification sending-out scenario is performed to obtain the correlation between the active power and the sending-end system voltage, the correlation between the reactive power and the frequency, and the gap in the reactive power, and the gap in the reactive power under the grid-connected wind turbine with uncontrolled rectification sending-out scenario is filled by the optimization system; the circuit analysis of the optimization system is performed to obtain the reactive power compensation expression of the optimization system, and the parameters of the series filter inductor and the parallel capacitor are set according to the reactive power compensation expression; and the performance of the optimization system after parameter setting is evaluated; The active power and voltage expression of the wind turbine outlet in the system applied to the grid-connected wind turbine with uncontrolled rectification sending-out scenario is obtained by building an equivalent circuit model of the wind turbine grid-side converter outlet as follows: wherein: is the active power emitted by the fan; is the DC side outlet voltage of the uncontrolled rectifier valve; is the number of series-connected twelve-pulse uncontrolled rectifier bridges; is the AC side voltage of the uncontrolled rectifier valve; is the impedance of the converter transformer; The reactive power and frequency expression of the wind turbine outlet is obtained as follows: wherein: is the reactive power emitted by the fan; is the sending end grid voltage; is the commutation overlap angle of the uncontrolled rectifier bridge; is the size of the equivalent reactive power compensation device; The voltage analysis of the sending-end power grid is performed to obtain the expression as follows: wherein: is the DC side voltage of the receiving converter; is the transformer ratio of the uncontrolled rectifier transformer; is the equivalent resistance of the DC transmission line; The analysis shows that the active power of the wind turbine is correlated with the sending-end power grid voltage; and the receiving-end DC voltage has a clamping effect on the sending-end power grid voltage, limiting the change range of the sending-end power grid voltage; when the voltage amplitude is fixed, the frequency and the reactive power at the outlet of the wind turbine are correlated, so that the wind turbine realizes frequency synchronization through reactive power synchronization control, and realizes the output voltage stability of the sending-end wind farm through active power control.

2. The optimization method implemented in the grid integration type wind turbine with non-controlled rectifier fed scenario based on the system of claim 1, characterized in that, The operation frequency of the collection system is 50 Hz of power frequency; The grid-connected wind turbine adopts process control, i.e. PV control and Qf control.

3. The optimization method for grid formation type wind turbine interface non-controlled rectification sending-out scene according to claim 2, characterized in that, The following analysis is performed based on the equivalent model of the grid-side converter outlet of the optimization system: wherein, is the current output by the optimization system; is the current input to the optimization system; is the imaginary unit; is the harmonic number; is the angular frequency; is the sending-end grid bus voltage; is the uncontrolled rectifier transformer ratio; is the series filter inductance of the optimization system; is the filter capacitance of the optimization system; denotes the phase angle of the offset; Neglecting the bus voltage harmonic content, the complex frequency is transformed as follows: wherein is a transfer function; is a Laplace complex variable; Definition of indicators : The following is obtained by simultaneous equations: wherein, represents the second harmonic current conversion ratio after the capacitive filtering the second harmonic current conversion ratio.

4. The optimization method for grid formation type wind turbine interface non-controlled rectification sending-out scene according to claim 3, characterized in that, In the application process of the optimization system, the control strategies of the active power, the reactive power and the frequency of the sending end alternating current voltage in the wind power stable sending stage are as follows: The voltage of the sending-end power grid is controlled by the wind turbine units. Through active power control, the voltage of each wind turbine is generated. Shaft voltage reference value Phase generation of each wind turbine unit is achieved through reactive power synchronization control. , combined Reactive current reference value generated by the control loop To change The size ensures the system's reactive power balance.

5. The optimization method for grid formation type wind turbine interface non-controlled rectification sending-out scene according to claim 4, characterized in that, The parameter setting of the series filter inductance and the parallel capacitor is as follows: The active power and the reactive power in the alternating current system are calculated as follows: wherein, , P and Q are the active and reactive power of the AC system, respectively; V is the AC bus voltage magnitude; I is the DC current; According to the actual engineering requirements, set = m and the active power to be regulated and the value of the reactive power , wherein is a set parameter; at the same time, the optimal change range of is set.

6. An optimization device for a grid-forming wind turbine connected to a non-controlled rectified grid according to the method of any of claims 1 to 5, characterized in that It comprises: The scene analysis module (1) is used for analyzing the power operation characteristics of the grid-connected wind turbine with non-controlled rectification sending out, obtaining the correlation between the active power and the sending end system voltage, the correlation between the reactive power and the frequency, and the gap of the reactive power; The topology optimization module (2) is used for topology optimization by the optimization system, filling the gap of the reactive power in the grid-connected wind turbine with non-controlled rectification sending out, and performing circuit analysis on the optimization system to obtain the reactive power compensation expression of the system; The parameter setting module (3) is used for setting the parameters of the series filter inductance and the parallel capacitor in the system according to the reactive power compensation expression; The performance evaluation module (4) is used for evaluating the performance of the optimized system after parameter setting.

7. The optimization apparatus for grid-type wind turbine interface with uncontrolled rectifier-fed scenarios according to claim 6, characterized in that, In the scene analysis module (1), the equivalent circuit model of the grid-connected wind turbine with non-controlled rectification sending out is built, and the active power and voltage expression of the wind turbine outlet are as follows: wherein: P is the active power emitted by the fan; Vdc is the DC side outlet voltage of the uncontrolled rectifier; N is the number of series-connected twelve-pulse uncontrolled rectifier bridges; Vac is the AC side voltage of the uncontrolled rectifier; Z is the impedance of the converter transformer; The expression of the reactive power and the frequency of the wind turbine outlet is as follows: wherein: is the reactive power emitted by the fan; is the sending end grid voltage; is the commutation overlap angle of the uncontrolled rectifier bridge; is the size of the equivalent reactive power compensation device; The expression of the sending end grid voltage is as follows: wherein: is the DC side voltage of the receiving converter; is the transformer ratio of the uncontrolled rectifier transformer; is the equivalent resistance of the DC transmission line; The analysis shows that the active power of the wind turbine is correlated with the sending end grid voltage, and the receiving end DC voltage has a clamping effect on the sending end grid voltage, limiting the change range of the sending end grid voltage; when the voltage amplitude is fixed, the frequency and the reactive power at the outlet of the wind turbine are correlated, so the wind turbine realizes frequency synchronization through reactive power synchronization control and realizes the output voltage stability of the sending end wind farm through active power control; In the topology optimization module (2), the following analysis is performed based on the equivalent model of the grid-side converter outlet of the optimization system: wherein, is the current output by the optimization system; is the current input to the optimization system; is the imaginary unit; is the harmonic number; is the angular frequency; is the sending-end grid bus voltage; is the uncontrolled rectifier transformer ratio; is the series filter inductance of the optimization system; is the filter capacitance of the optimization system; denotes the phase angle of the offset; Neglecting the bus voltage harmonic content, the complex frequency is transformed as follows: wherein is a transfer function; is a Laplace complex variable; Definition of metrics : The following is obtained by simultaneous equations: wherein, represents the capacitor filtered sub-harmonic current conversion ratio; In the application process of the optimization system, the control strategies of the active power, the reactive power and the frequency of the sending end alternating current voltage in the wind power stable sending stage are as follows: The voltage of the sending-end power grid is controlled by the wind turbine units. Through active power control, the voltage of each wind turbine is generated. Shaft voltage reference value Phase generation of each wind turbine unit is achieved through reactive power synchronization control. , combined Reactive current reference value generated by the control loop To change The size ensures the reactive power balance of the system; The parameter setting of the series filter inductance and the parallel capacitor is as follows: The active power and the reactive power in the alternating current system are calculated as follows: wherein, , P and Q are active power and reactive power of the AC system, respectively; V is the AC bus voltage magnitude; I is the DC current; According to the actual engineering requirements, set = m and the active power to be regulated and the value of the reactive power , wherein, is a set parameter; at the same time, the optimal change range of is set.

8. A computer readable medium having computer program instructions stored thereon, the computer program instructions being executable by a processor to implement the method of claims 1-5.

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