CN112910006B - Universal electromagnetic transient modeling method for direct-drive wind turbine generator - Google Patents
Universal electromagnetic transient modeling method for direct-drive wind turbine generator Download PDFInfo
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Abstract
A general electromagnetic transient modeling method for a direct-drive wind turbine generator relates to the technical field of power system simulation modeling. According to the method, the voltage, the current, the active power and the reactive power response of the actual direct-drive wind turbine generator are obtained by testing the low-voltage ride through capability of a plurality of direct-drive wind turbine generators, a universal electromagnetic transient response curve of the whole fault ride through process of the direct-drive wind turbine generators is obtained according to the response, the dynamic behaviors of the active power and the reactive power are analyzed according to the curve, and the behavior is described; analyzing a reference value of the active component and a reference value of the reactive component of the current, and inputting the obtained reference values into a current controller of a grid-side converter of a universal electromagnetic transient simulation model of the direct-drive wind turbine generator; and identifying the fault ride-through control parameters and the grid-side converter parameters of the direct-drive wind turbine generator set by adopting step-by-step identification. The method is mainly used for general electromagnetic transient modeling of the direct-drive wind turbine generator.
Description
Technical Field
The invention relates to a general electromagnetic transient modeling method for a direct-drive wind turbine generator, and belongs to the technical field of power system simulation modeling.
Background
The growing energy demand and the ever-increasing environmental concerns have greatly facilitated the development of wind power generation. The direct-drive wind turbine generator set has the advantages of high energy density, simple control method and the like, and is more and more commonly applied to onshore and offshore wind power plants. However, as the permeability of the wind turbine generator is continuously improved, the wind power integration brings serious challenges to the safe operation of a power system, and an electromagnetic transient model capable of accurately reflecting the fault ride-through characteristic of the actual direct-drive wind turbine generator under the condition of voltage drop is established, so that the method has important significance for correctly evaluating the influence of the large-scale wind power integration on the power grid.
However, because confidential information is involved, the electromagnetic transient model established by the fan manufacturer is generally in a 'black box' form, and the internal control strategy and control parameters cannot be obtained, which seriously hinders the development of related researches. Therefore, it is highly desirable to build a general electromagnetic transient model. The general electromagnetic transient model of the direct-drive wind turbine generator set established in the existing research mostly focuses on modeling the fault duration, but fails to completely and specifically model the recovery process after fault clearing and the switching transient state between different fault stages (including the steady-state stage before fault occurrence, the fault duration stage, the recovery stage after fault clearing to the steady-state value of active power and reactive power and the steady-state stage after the recovery stage). Meanwhile, control parameters (including fault ride-through control parameters and converter control parameters) of the direct-drive wind turbine generator electromagnetic transient model in the whole fault ride-through process are not accurately identified, so that obvious deviation exists between the model output and measured data, and engineering use has large limitation.
Disclosure of Invention
The method aims to solve the problem that the conventional method for performing universal electromagnetic transient modeling on the whole fault ride-through process of the direct-drive wind turbine generator system is lacked. A general electromagnetic transient modeling method for a direct-drive wind turbine generator is provided.
A general electromagnetic transient modeling method for a direct-drive wind turbine generator comprises the following steps:
step 1: carrying out low voltage ride through test on the plurality of direct-drive wind turbine generators to obtain voltage, current, active power and reactive power responses of the plurality of direct-drive wind turbine generators under different voltage drop conditions, and obtaining a universal electromagnetic transient response curve of the whole fault ride through process of the direct-drive wind turbine generators according to the responses of the voltage, the current, the active power and the reactive power;
and 2, step: analyzing the dynamic behaviors of the active power and the reactive power in the whole fault ride-through process according to the universal electromagnetic transient response curve of the whole fault ride-through process of the direct-drive wind turbine generator system obtained in the step 1, and describing the dynamic behaviors of the active power and the reactive power in the whole fault ride-through process;
and step 3: analyzing a reference value of a current active component and a reference value of a current reactive component according to the dynamic behavior formulas of the active power and the reactive power in the whole fault ride-through process obtained in the step 2, inputting the obtained reference values into a current controller of a grid-side converter of the universal electromagnetic transient simulation model of the direct-drive wind turbine generator, and automatically adjusting the dynamic behavior of the universal electromagnetic transient simulation model of the direct-drive wind turbine generator by utilizing the tracking action of the current controller of the grid-side converter;
and 4, step 4: and identifying fault ride-through control parameters and grid-side converter parameters of the direct-drive wind turbine generator system by adopting step-by-step identification.
Further, the fault ride-through overall process in the step 1 includes a steady-state stage before the fault occurs, a fault continuation stage, a recovery stage from the fault clearing to the state where both the active power and the reactive power are recovered to the steady-state values, and a steady-state stage after the recovery stage is completed; and obtaining a general electromagnetic transient response curve of the direct-drive wind turbine generator in the whole fault ride-through process, wherein the general electromagnetic transient response curve comprises a response curve of voltage, instantaneous active power and instantaneous reactive power.
Further, in step 2, the dynamic behavior of the active power in the fault ride-through overall process is described as follows:
in the formula, P normal The active power representing the normal working state, and the corresponding time range is [ -, t [ ] 1 ]And [ t 7 ,～]，P fault Representing the active power during the fault duration, corresponding to a time range t 1 ,t 3 ]，P re The active power representing the fault recovery process corresponds to the time ranges of t 3 ,t 7 ]T represents the current simulation run time; u. of g Representing the port voltage, i, of the direct-drive wind turbine P_normal Representing the active component of the current in the normal operating state, i P_fault Representing the current active component during the fault duration, I max Represents the maximum current, i Q_fault Representing the reactive component of the current during the fault duration; p (t) 3 ) Represents t 3 Active power at time P (t) 4 ) Represents t 4 Active power at a moment r P Representing the rate of restoration of active power after the fault has cleared, P 0 Representing steady state active power before the fault;
the dynamic behavior of reactive power throughout the fault ride-through is described as follows:
in the formula, Q normal Representing the reactive power in normal working state, and the corresponding time range is [ -, t [ ] 1 ]And [ t 6 ,～]，Q fault Representing reactive power during the fault duration, corresponding to a time range t 1 ,t 3 ]，Q re The reactive power representing the fault recovery process corresponds to time ranges of t 3 ,t 6 ]；i Q_normal Is a reactive component of current under normal working condition, i Q_fault For the reactive component of the current during the duration of the fault, i lim_Q Representing the limit value of reactive component of current in fault period, k is reactive power support coefficient, and according to grid-connected standard k is greater than or equal to 1.5 set Representing a set voltage threshold, which is constant according to a grid-connection standard u set Is 0.9p.u., I n Representing rated current, i Q0 Representing a steady state current reactive component before a fault; q (t) 3 ) Represents t 3 Reactive power at time, Q (t) 5 ) Represents t 5 Reactive power at time, r Q Representing the rate of recovery of reactive power after fault clearing, Q 0 Representing steady state reactive power prior to the fault.
Further, the specific process of analyzing the reference value of the current active component and the reference value of the current reactive component according to the dynamic behavior formula of the active power and the reactive power obtained in the step 2 in the whole fault ride-through process, inputting the obtained reference values into a current controller of a grid-side converter of the universal electromagnetic transient simulation model of the direct-drive wind turbine generator, and automatically adjusting the dynamic behavior of the universal electromagnetic transient simulation model of the direct-drive wind turbine generator by utilizing the tracking function of the current controller of the grid-side converter comprises the following steps:
when the direct-drive wind turbine generator system adopts the vector control of grid voltage orientation and the grid voltage is oriented to the d axis of the dq synchronous rotation reference coordinate system, the reference value of the current active component corresponds to the reference value i of the d axis component of the current controller dref Reference value of reactive component of current corresponds to reference value i of q-axis component of current controller qref (ii) a Reference value i of current active component dref Expressed as:
in the formula i dref_normal Reference value, i, representing the active component of the current in normal operation dref_fault Reference value, i, representing the current active component during the fault duration dref_re A reference value representing the active component of the current during the fault recovery process; k is a radical of formula P_udc And k I_udc Respectively representing the proportional and integral coefficients, u, of the external loop PI controller for DC voltage dcref Reference value, u, representing a DC voltage dc Representing a direct voltage, i qref_fault Reference value, r, representing the reactive component of the current during the duration of the fault id Representing the recovery rate of the current active component after the fault is cleared;
reference value i of the reactive component of the current qref Expressed as:
in the formula i qref_normal Reference value, i, representing the reactive component of the current in normal operation qref_re A reference value representing a reactive component of current during fault recovery; k is a radical of P_Q And k I_Q Respectively representing the proportional and integral coefficients, Q, of the reactive power outer loop PI controller ref Representing a reference value of reactive power, Q representing reactive power, r iq A recovery rate representing a reactive component of the current after the fault is cleared;
and (3) assigning values to d-axis and q-axis current reference values of a current controller in a grid-side converter of the direct-drive wind turbine generator set general electromagnetic transient simulation model according to a formula (3) and a formula (4), and automatically adjusting the dynamic behavior of the direct-drive wind turbine generator set general electromagnetic transient simulation model by using the current controller.
Further, the specific process of identifying the fault ride-through control parameters and the grid-side converter parameters of the direct-drive wind turbine generator system by step-by-step identification in step 4 includes the following steps:
step 4.1: analyzing and calculating fault ride-through control parameters of the direct-drive wind turbine generator according to voltage, current, active power and reactive power data of a low-voltage ride-through test of the direct-drive wind turbine generator;
step 4.2: and identifying and obtaining the parameters of the grid-side converter by adopting an optimization algorithm according to the voltage, current, active power and reactive power data of the low voltage ride through test of the direct-drive wind turbine generator.
Further, the direct-drive wind turbine generator fault ride-through control parameters in the step 4.1 include a reactive power support coefficient k and a recovery rate r of an active component of current after fault clearing id Rate of recovery r of reactive component of current after fault clearance iq Active power recovery delay t after fault clearance dealy_P And reactive power support delay t after fault clearing dealy_Q 。
Further, the specific process of calculating the fault ride-through control parameter of the direct-drive wind turbine generator according to the voltage, current, active power and reactive power data analysis of the low voltage ride-through test of the direct-drive wind turbine generator, which is described in the step 4.1, includes the following steps:
decomposing three-phase instantaneous voltage and three-phase instantaneous current of low voltage ride through test of an actual direct-drive wind turbine generator into a dq synchronous rotation reference coordinate system, wherein d-axis components and q-axis components of the three-phase instantaneous voltage are respectively u dM And u qM The d-axis component and the q-axis component of the three-phase instantaneous current are i respectively dM And i qM ；
And calculating a reactive power support coefficient k according to test data of slight voltage drop:
k＝(i qM0 -i qM )/[I n (u set -u g )] (5)
in the formula i qM0 Test value, i, representing reactive component of current in normal operating condition qM A test value representing a reactive component of current during a fault duration; u. of gM A measurement value representing a voltage during a fault duration;
recovery rate r of active component of current after fault clearance id And the active power recovery delay t after the fault is cleared dealy_P And calculating according to the test data of the direct-drive wind turbine generator running at high wind speed under the condition of deep voltage drop:
in the formula i dM (t 7 ) Represents t 7 Test value of the active component of the current at that moment, i dM (t 4 ) Represents t 4 Testing the active component of the current at the moment;
recovery rate r of reactive component of current after fault clearance iq And reactive power recovery delay t after fault clearance dealy_Q Calculating according to the test data after the direct-drive wind turbine generator fault is cleared; when the direct-drive wind turbine generator set continues to provide reactive support after the fault is cleared, t dealy_Q The calculation is as follows:
t delay_Q ＝t 5 -t 3 (7)
when the fault is cleared, the reactive power of the direct-drive wind turbine generator has the slope recovery characteristic, and t is the same 5 When the reactive power at the moment is not recovered to the steady-state reactive power before the fault, r iq The calculation is as follows:
r iq ＝[i qM (t 6 )-i qM (t 5 )]/(t 6 -t 5 ) (8)
in the formula i qM (t 6 ) Represents t 6 Test value of the reactive component of the current at that moment, i qM (t 5 ) Represents t 5 Testing the reactive component of the current at the moment;
further, the parameters of the grid-side converter of the direct-drive wind turbine generator set in the step 4.2 include a current inner loop PI controller parameter k P_c And k I_c Outer loop PI controller parameter k of DC voltage P_udc And k I_udc And a reactive power outer loop PI controller parameter k P_Q And k I_Q 。
Further, in step 4.2, the specific process of identifying and obtaining the grid-side converter parameters by using an optimization algorithm according to the voltage, current, active power and reactive power data of the low voltage ride through test of the direct-drive wind turbine generator set comprises the following steps:
step 4.2.1: carrying out a deep voltage drop test on a direct-drive wind turbine generator set running at a high wind speed to obtain active power test data P M And reactive power test data Q M Setting the input wind speed, the voltage drop depth and the voltage drop time which are the same as those of a low voltage ride through test in a universal electromagnetic transient simulation model of the direct-drive wind turbine generator; using optimisationMethod for identifying bandwidth f of current inner loop PI controller by algorithm c ；
Step 4.2.1 the bandwidth f of the current inner loop PI controller is identified by adopting an optimization algorithm c In the process of (3), identifying the objective function as:
in the formula, P S And Q S Respectively representing the active power and the reactive power output by the general electromagnetic transient simulation model, N s And N e The numbers of the first simulation data and the last simulation data and the test data of the parameter identification are respectively represented, and i represents the numbers of the simulation data and the test data.
Identifying the bandwidth f of the obtained current inner loop PI controller c Substituting formula (10) to calculate current inner loop PI controller parameter k P_c And k I_c ：
In the formula, L f And R f Respectively representing the inductance and resistance of the net side filter, and can be obtained from a fan manufacturer.
Step 4.2.2: carrying out mild voltage drop test on a direct-drive wind turbine generator set running at low wind speed to obtain active power test data P M Setting the input wind speed, the voltage drop depth and the voltage drop time which are the same as those of a low voltage ride through test in a universal electromagnetic transient simulation model of the direct-drive wind turbine generator; method for identifying bandwidth f of direct-current voltage outer-loop PI controller by adopting optimization algorithm udc ；
Step 4.2.2 the bandwidth f of the direct-current voltage outer loop PI controller is identified by adopting an optimization algorithm udc In the process of (3), the identified objective function is:
identifying the obtained bandwidth f of the DC voltage outer loop PI controller udc Substituting formula (12) to calculate the parameter k of the outer loop PI controller of the DC voltage P_udc And k I_udc ；
In the formula, C represents a direct current capacitor of the direct-drive wind turbine generator and can be obtained from a fan manufacturer.
Step 4.2.3: according to the low voltage ride through test of the direct-drive wind turbine generator in the steps 4.2.1 and 4.2.2, reactive power test data Q are obtained M Setting the input wind speed, the voltage drop depth and the voltage drop time which are the same as those of the low voltage ride through test in a general electromagnetic transient simulation model; method for identifying reactive power outer loop parameter k by adopting optimization algorithm P_Q And k I_Q ；
Step 4.2.3 identifying the outer loop parameter k of the reactive power by adopting an optimization algorithm P_Q And k I_Q In the process of (2), the identified objective function is:
the invention has the beneficial effects that:
the method comprises the steps of carrying out low voltage ride through capability test on a plurality of actual direct-drive wind turbine generators, and providing a universal electromagnetic transient response curve of the whole fault ride through process of the direct-drive wind turbine generators according to a test result; and then analyzing the dynamic behaviors of the active power and the reactive power in the whole fault ride-through process, performing formulaic description on the dynamic behaviors of the active power and the reactive power in the whole fault ride-through process, then providing a current reference value calculation method of the whole fault ride-through process of the direct-drive wind turbine generator, inputting the current reference value into a current controller of a grid-side converter, automatically updating the reference value of the current controller of the grid-side converter according to the working state of the direct-drive wind turbine generator, and realizing the simulation of the whole fault ride-through process of the actual direct-drive wind turbine generator. In order to improve the accuracy of the model, a step-by-step identification method is designed to identify the fault ride-through control parameters and the grid-side converter parameters. According to the method, a certain actual direct-drive wind turbine generator is selected, under the conditions of the same parameters and the same voltage drop, the response characteristics of the voltage, the current, the active power and the reactive power of the universal electromagnetic transient simulation model of the direct-drive wind turbine generator are compared with the response characteristics of the voltage, the current, the active power and the reactive power of the actual direct-drive wind turbine generator, and the result shows that the universal electromagnetic transient simulation model of the direct-drive wind turbine generator has high precision and can simulate the transient response of the whole fault ride-through process of the actual direct-drive wind turbine generator.
Drawings
FIG. 1 is a schematic diagram of the wiring principle of an actual test system;
FIG. 2 is a transient response characteristic curve diagram of 5 groups of actual direct-drive wind turbine generators under the condition of voltage drop;
FIG. 3 is a general electromagnetic transient response curve diagram of the overall process of fault ride-through of the direct-drive wind turbine generator;
FIG. 4 is a control schematic diagram of a grid-side converter of the direct-drive wind turbine generator designed by the invention;
FIG. 5 is a general electromagnetic transient simulation model of a direct-drive wind turbine generator set, which is established by the invention;
FIG. 6 is a graph comparing simulation results and measured data for set 1 test data;
FIG. 7 is a graph comparing simulation results and measured data for set 2 test data;
FIG. 8 is a schematic time phase diagram defined in the "wind turbine generator electrical simulation model modeling guide rule" of the Chinese standard.
Detailed Description
The first specific implementation way is as follows:
the general electromagnetic transient modeling method for the direct-drive wind turbine generator set comprises the following steps:
step 1: according to the Chinese grid-connected standard technical provisions of accessing wind power plants to a power system, a plurality of direct-driven wind power generation sets are subjected to low voltage ride through capability test, the schematic structure diagram of the test system is shown in figure 1, and the transient response curves of voltage, current, active power and reactive power of a plurality of groups of actual direct-driven wind power generation sets are obtained. In order to show the fault ride-through response characteristic of the actual direct-drive wind turbine generator, 5 groups of test results are provided in this embodiment, as shown in fig. 2, where fig. 2 (a), fig. 2 (b), fig. 2 (c), and fig. 2 (d) correspond to voltage, current, active power, and reactive power, respectively.
According to the instantaneous active power and the instantaneous reactive power response of the direct-drive wind turbine generator shown in fig. 2, it can be seen that the active power of the direct-drive wind turbine generator is reduced and the reactive power is increased after the voltage drops. After the fault is cleared, the voltage begins to rise, the active power is increased, and the reactive power is reduced. When the voltage is recovered to a normal range (namely the voltage is greater than a threshold value of low voltage ride through and is 0.9p.u. In the Chinese grid-connected standard), the active power of the direct-drive wind turbine generator set running at the low wind speed is rapidly recovered to a steady-state value P before the fault 0 No recovery procedure is required (as in tests 2 and 3 in fig. 2); the active power of the direct-drive wind turbine generator operated at high wind speed is subjected to short time delay t dealy_P Then, with a slope r p Restore to the pre-fault steady state value P 0 . Wherein, t dealy_P And r p Are parameters that can be dynamically adjusted. For example when t dealy_P =0, active power with slope r p Return to the pre-failure steady state value without delay (test 5 in fig. 2); when r is p When set to a large value, the active power is quickly restored to P 0 (test 5 in figure 2). Thus, by adjusting t dealy_P And r p The established model can simulate the active power recovery characteristics of direct-drive wind turbine generators designed by different manufacturers.
After the fault is cleared, the direct-drive wind turbine generator continues to provide reactive power Q for the power grid supp At a short delay t dealy_Q Then, the reactive power is in slope r Q Restore to the steady state value Q before failure 0 . Wherein, t dealy_Q 、Q supp And r Q Are parameters that can be dynamically adjusted. For example when t dealy_Q When =0, the reactive power is in slope r Q The steady state value before the fault is recovered without time delay; when Q is supp When =0, t of the direct-drive wind turbine generator set after fault clearing dealy_Q No reactive power is provided for the power grid within the time; when r is Q Is provided withAt a large value, the reactive power is quickly restored to Q 0 . Thus, by adjusting t dealy_Q ，Q supp And r Q The established model can simulate the reactive power recovery characteristics of direct-drive wind turbine generators designed by different manufacturers.
Based on the analysis, the invention provides a universal electromagnetic transient response curve of the whole fault ride-through process of the direct-drive wind turbine generator to represent possible fault behaviors of the direct-drive wind turbine generators of different manufacturers, as shown in fig. 3. In FIG. 3, [ -, t [ - ] 1 ]And [ t 7 ,～]The period represents a steady state stage before the direct-drive wind turbine generator fault occurs and a steady state stage after the recovery stage is completed, and is called stage 1 in the invention; [ t ] of 1 ，t 3 ]The period represents the fault duration period from the fault occurrence to the fault clearing period, referred to as period 2 in the present invention; [ t ] of 3 ，t 7 ]The period represents the fault clearing to a recovery phase where both active and reactive power are restored to steady state values, referred to herein as phase 3. In order to represent the recovery characteristics of direct-drive wind turbine generators of different manufacturers, 2 sub-stages are respectively adopted in the recovery stage to describe the recovery behaviors of active power and reactive power. The control principle and the main parameters of the direct-drive wind turbine generator in the whole fault ride-through process are shown in the table 1.
TABLE 1 control principle and main parameters of direct-drive wind turbine generator in the whole fault ride-through process
It is to be noted that the stages in table 1 are not necessarily all included in the general electromagnetic transient simulation model of the direct-drive wind turbine, and when the fault behaviors of the direct-drive wind turbines designed by different manufacturers are simulated, only the main parameters of each stage need to be adjusted, so that the general electromagnetic transient response curve of the overall fault ride-through process of the direct-drive wind turbine shown in fig. 3 can flexibly represent the fault behaviors of different direct-drive wind turbines.
Step 2: analyzing the dynamic behaviors of active power and reactive power in the whole fault ride-through process according to a general electromagnetic transient response curve of the whole fault ride-through process of the direct-drive wind turbine generator as shown in FIG. 3;
1) Stage 1: steady state phase before fault occurrence and after recovery phase completion
According to the control principles of table 1, the dynamic behavior of active power and reactive power of phase 1 can be represented by equation (1):
in the formula, P normal The active power representing the normal working state, and the corresponding time range is [ -, t [ ] 1 ]And [ t 7 ,～]，Q normal The reactive power represents the normal working state, and the corresponding time range is [ -, t [ ] 1 ]And [ t 6 ,～]T represents the current simulation run time; u. u g Representing the port voltage of the direct-drive wind turbine generator; i all right angle P_normal Representing the active component of the current in the normal operating state, i Q_normal Is the reactive component of the current under the normal working state.
2) And (2) stage: failure continuation process
According to the control principle of the table 1, the direct-drive wind turbine generator set adjusts the output power according to the grid-connected standard requirement during the fault duration. In order to support the grid voltage, direct-drive wind turbines usually preferentially provide reactive power. Thus, the dynamic behavior of active and reactive power of phase 2 can be represented by equation (2):
in the formula, P fault Representing the active power during the fault duration, corresponding to a time range t 1 ,t 3 ]，Q fault Representing reactive power during the fault duration, corresponding to a time range t 1 ,t 3 ]；i P_fault Representing the current active component during the fault duration, i Q_fault Is the reactive component of the current during the fault duration; i is max Represents the maximumCurrent, i lim_Q Representing the limit value of reactive component of current in fault period, k is reactive power support coefficient, and according to grid-connected standard k is greater than or equal to 1.5 set Representing a set voltage threshold, constant, according to a grid-connection standard u set Is 0.9p.u., I n Representing rated current, i Q0 Representing the steady state reactive component of current before the fault.
3) And (3) stage: recovery procedure
The active power recovery process comprises the following steps: according to the control principle of the table 1, the direct-drive wind turbine generator is driven at t in the stage 3-1 dealy_P The active power at the end of phase 2 is maintained for the time. Then, in the stage 3-2, the active power of the direct-drive wind turbine generator is driven by the slope r P Is restored to the steady state value P before the fault 0 . Thus, the dynamic behavior of active power of stage 3 can be represented by equation (3):
in the formula, P re The active power representing the fault recovery process corresponds to the time ranges of t 3 ,t 7 ]；P(t 3 ) Represents t 3 Active power at time, P (t) 4 ) Represents t 4 Active power at a moment r P Representing the rate of restoration of active power after fault clearance, P 0 Representing steady state active power before the fault.
And (3) a reactive power recovery process: according to the control principle in the table 1, the direct-drive wind turbine generator continues to provide the power for a period of time t at the stage 3-1 dealy_Q Of the reactive power of (c). Different manufacturers may adopt different control strategies to meet the requirement, and in order to ensure the universality, the invention provides two reactive power support strategies:
strategy 1: the direct-driven wind turbine generator continues to operate in a reactive support mode, and dynamic reactive support is provided according to the voltage condition of a power grid;
strategy 2: the reactive power output by the direct-drive wind turbine generator is kept at the reactive power at the end moment of the stage 2, and a fixed reactive support is provided;
in stage 3-2, the reactive power control of the direct-drive wind turbine generator is switched back to the normal operation mode. If the reactive power Q (t) is present at this time 5 ) Restore to the steady state value Q before failure 0 If so, ending the recovery process; otherwise, in order to avoid the impact of the reactive power switching control strategy on the voltage, the reactive power of some types of direct-drive wind turbine generators has a slope recovery characteristic. Thus, the dynamic behavior of the reactive power of phase 3 can be represented by equation (4):
in the formula, Q re The reactive power representing the fault recovery process corresponds to time ranges of t 3 ,t 6 ]；Q(t 3 ) Represents t 3 Reactive power at time, Q (t) 5 ) Represents t 5 Reactive power at time, r Q Representing the rate of recovery of reactive power after fault clearing, Q 0 Representing steady state reactive power before the fault.
And 3, step 3: analyzing a reference value of a current active component and a reference value of a current reactive component according to the dynamic behavior formulas of the active power and the reactive power in the whole fault ride-through process obtained in the step 2, inputting the obtained reference values into a current controller of a grid-side converter of the universal electromagnetic transient simulation model of the direct-drive wind turbine generator, and automatically adjusting the dynamic behavior of the universal electromagnetic transient simulation model of the direct-drive wind turbine generator by utilizing the tracking function of the current controller of the grid-side converter, wherein the specific details are as follows:
according to the operation principle of the direct-drive wind turbine generator, the adjustment of the response characteristics of the active power and the reactive power is realized by adjusting the reference value of the current active component and the reference value of the current reactive component of the current controller of the grid-side converter respectively. Therefore, the key point of modeling the whole fault ride-through process of the direct-drive wind turbine generator system is that the reference value of the active component and the reference value of the reactive component of the current in the current controller of the grid-side converter of the direct-drive wind turbine generator system are analyzed according to the dynamic behavior formulas of the active power and the reactive power in the whole fault ride-through process. When directly driving wind powerWhen the unit adopts vector control of grid voltage orientation and the grid voltage is oriented to the d axis of the dq synchronous rotation reference coordinate system, the reference value of the current active component corresponds to the reference value i of the d axis component of the current controller dref Reference value of reactive component of current corresponds to reference value i of q-axis component of current controller qref 。
Therefore, the invention provides a reference value i of the active component of the current in the whole process of fault ride-through of the direct-drive wind turbine generator in the step dref And a reference value i of the reactive component of the current dref The method of (3). Reference value i of current active component dref Expressed as:
in the formula i dref_normal Reference value, i, representing the active component of the current in normal operation dref_fault Reference value, i, representing the current active component during the fault duration dref_re A reference value representing the active component of the current during the fault recovery process; k is a radical of formula P_udc And k I_udc Respectively representing the proportional and integral coefficients, u, of the external loop PI controller for DC voltage dcref Reference value, u, representing a DC voltage dc Represents a direct voltage i qref_fault Reference value, r, representing the reactive component of the current during the duration of the fault id Representing the rate of recovery of the real component of the current after the fault has cleared.
Reference value i of the reactive component of the current qref Expressed as:
in the formula i qref_normal Reference value, i, representing the reactive component of the current in normal operation qref_re Reference value, i, representing the reactive component of the current during fault recovery qref0 Representing a steady state reactive current component prior to a fault; k is a radical of formula P_Q And k I_Q Respectively representing the proportional and integral coefficients of the reactive power PI controller,Q ref representing a reference value of reactive power, Q representing reactive power, r iq Representing the recovery rate of the reactive component of the current after the fault has cleared.
Assigning reference values of d-axis current and q-axis current of a current controller of a grid-side converter of a direct-drive wind turbine generator universal electromagnetic transient simulation model according to formulas (5) and (6), and simultaneously assigning a grid-side current active component i of the direct-drive wind turbine generator universal electromagnetic transient simulation model d And a current reactive component i q D-axis and q-axis current actual values input to the current controller, and a voltage reference value e of the grid-side converter is generated through the current PI controller dref And e qref ：
Where ω is the angular frequency of the mains voltage, R f And L f Respectively the resistance and inductance of the network side filter, k P_c And k I_c Respectively representing the proportional and integral coefficients of the current inner loop PI controller.
E is to be dref And e qref Transformation from dq synchronous rotation reference coordinate system to abc three-phase stationary coordinate system under e abcref And generating a trigger signal of a direct-drive wind turbine generator switch device IGBT by using a pulse width modulation technology. A control block diagram of a grid converter of the direct-drive wind turbine generator in the whole fault crossing process is shown in fig. 4, and the grid-side converter automatically updates a reference value of a current controller of the grid-side converter according to the current working state of the direct-drive wind turbine generator, so that the dynamic behavior of a universal electromagnetic transient simulation model of the direct-drive wind turbine generator is adjusted, and the simulation of the transient response of the whole fault crossing process of the actual direct-drive wind turbine generator is realized.
And 4, step 4: in order to ensure the accuracy of the established universal electromagnetic transient model of the direct-drive wind turbine generator, the step of identifying the fault ride-through control parameters and the grid-side converter parameters of the direct-drive wind turbine generator specifically comprises the following steps:
fault ride-through control parameters: coefficient of reactive power support k, rate of recovery of current active component r id Recovery of reactive component of currentRate r iq Active power recovery delay t after fault clearance dealy_P And the reactive power support delay t after fault clearing dealy_Q ；
Grid-side converter parameters: current inner loop PI controller parameter k P_c And k I_c Outer loop PI controller parameter k of DC voltage P_udc And k I_udc And a reactive outer loop PI controller parameter k P_Q And k I_Q 。
During the fault duration, the active power and the reactive power injected into the power grid by the direct-drive wind turbine generator mainly depend on fault ride-through control parameters, and the transient tracking performance of the controller is mainly influenced by the parameters of the grid-side converter. Thus, the present invention employs two-step identification to determine these parameters.
In step 4.1, analyzing and calculating the fault ride-through control parameters of the direct-drive wind turbine generator according to the voltage, current, active power and reactive power data of the low-voltage ride-through test of the direct-drive wind turbine generator, and the specific process is as follows:
decomposing three-phase instantaneous voltage and three-phase instantaneous current of low voltage ride through test of an actual direct-drive wind turbine generator into a dq synchronous rotation reference coordinate system, wherein d-axis components and q-axis components of the three-phase instantaneous voltage are respectively u dM And u qM The d-axis component and the q-axis component of the three-phase instantaneous current are i respectively dM And i qM 。
1) Coefficient of reactive power support k
The reactive component of the current injected into the power grid by the direct-drive wind turbine generator is in direct proportion to the voltage deviation during the voltage drop period, and is limited to the maximum reactive component of the current. When slight voltage sag, the current reactive component is less than the maximum current reactive component, so k can be calculated according to the test data of slight voltage sag:
k＝(i qM0 -i qM )/[I n (u set -u g )] (8)
in the formula i qM0 Test value u representing reactive component of current in normal operating condition gM Representing a measure of the voltage during the fault.
2) Recovery rate r of active component of current after fault clearance id And thereforeActive power recovery delay t after clearing of the fault dealy_P
Under the condition of deep voltage drop, when the voltage is recovered to the normal operation range, the current active component of the direct-drive wind turbine generator operated at high wind speed is delayed by t dealy_P Then with a slope r id And (6) recovering. Therefore, r can be calculated according to the test data of the direct-drive wind turbine generator operated at high wind speed with the depth voltage drop id And t dealy_P ：
In the formula i dM (t 7 ) Represents t 7 Test value of the active component of the current at a time i dM (t 4 ) Represents t 4 And (4) testing the active component of the current at the moment.
3) Recovery rate r of reactive component of current after fault clearance iq And reactive power recovery delay t after fault clearance dealy_Q
r iq And t dealy_Q The calculation can be carried out according to the test data after the fault is cleared, and when the direct-drive wind turbine generator continues to provide reactive power after the fault is cleared, t dealy_Q The calculation is as follows:
t delay_Q ＝t 5 -t 3 (10)
when the fault is cleared, the reactive power of the direct-drive wind turbine generator has the slope recovery characteristic, and t is the same 5 When the reactive power at the moment is not recovered to the steady-state reactive power before the fault, r iq The calculation is as follows:
r iq ＝[i qM (t 6 )-i qM (t 5 )]/(t 6 -t 5 ) (11)
in the formula i qM (t 6 ) Represents t 6 Test value of the reactive component of the current at the moment i qM (t 5 ) Represents t 5 Testing the reactive component of the current at the moment;
in step 4.2, according to the voltage, current, active power and reactive power data of the low voltage ride through test of the direct-drive wind turbine generator, the specific process of identifying and obtaining the parameters of the PI controller of the grid-side converter by adopting an optimization algorithm is as follows:
firstly, determining parameters to be identified, wherein the parameters of the PI controllers of the grid-side converter comprise three groups:
current inner loop PI controller parameters: k is a radical of formula P_c And k I_c ；
Parameters of a direct-current voltage outer ring PI controller: k is a radical of P_udc And k I_udc ；
Parameters of a reactive power outer loop PI controller: k is a radical of P_Q And k I_Q ；
Wherein, the current inner loop PI controller parameter k P_c And k I_c Can be expressed as:
in the formula (f) c Is the bandwidth of the current inner loop, R f And L f The circuit parameters can be obtained from a fan manufacturer. Thus, it is possible to identify f c To determine k P_c And k I_c 。
Parameter k of direct-current voltage outer loop PI controller P_udc And k I_udc Can be expressed as:
in the formula (f) udc Is the bandwidth of the outer loop of the DC voltage u n The rated voltage of the power grid is a known quantity, and the C is a circuit parameter and can be obtained from a fan manufacturer. Thus, it is possible to identify f udc To determine k P_udc And k I_udc 。
In summary, the grid-side converter PI controller has 4 to-be-identified parameters: bandwidth f of current inner loop PI controller c Bandwidth f of outer loop PI controller for DC voltage udc Outer loop PI controller parameter k of reactive power P_Q And k I_Q 。
Because the inner ring PI controller and the outer ring PI controller are in a cascade relation, the PI controllers cannot be identified at the same time under the same disturbance. Thus, the present invention utilizes different perturbations to identify these parameters. For a direct-drive wind turbine generator set running at a high wind speed, when a deep voltage dip occurs, a reference value of a current active component and a reference value of a current reactive component can be expressed as follows:
at this time, the d-axis and q-axis voltage reference values of the grid-side converter can be expressed as:
according to the formula (15), the d-axis and q-axis voltage reference values of the grid-side converter only depend on the bandwidth f of the current inner loop PI controller c And with the outer loop parameter (f) udc ，k P_Q And k I_Q ) Is irrelevant. Therefore, to identify f more efficiently c And test data of the direct-drive wind turbine generator set running at high wind speed under deep voltage drop can be utilized.
For a direct-drive wind turbine generator set running at a low wind speed, when a light voltage drop occurs, a reference value of a current active component and a reference value of a current reactive component can be expressed as follows:
at this time, the reference values of the d and q axes of the grid-side converter are as follows:
wherein,
according to the formulas (17) and (18), the d-axis and q-axis voltage reference values of the grid-side converter depend on the bandwidth f of the current inner loop PI controller c And bandwidth f of direct-current voltage outer-loop PI controller udc And with the parameter k of the reactive power outer loop PI controller P_Q And k I_Q Is irrelevant. At the determination of f c After, only f udc Identification is required. Therefore, to identify f more efficiently udc And test data of the direct-drive wind turbine generator set running at low wind speed under slight voltage drop can be utilized.
At the determination of f c And f udc The test data pairs k can then be utilized P_Q And k I_Q And (5) performing identification.
To sum up, first identify the bandwidth f of the current inner loop PI controller c And secondly the bandwidth f of the DC voltage outer loop PI controller udc Finally, identifying the parameter k of the reactive power outer loop PI controller P_Q And k I_Q By adopting the sequence, the decoupling identification of the inner ring cascade controller and the outer ring cascade controller can be realized. In this embodiment, taking a 1.5MW direct-drive wind turbine as an example, identifying parameters of a PI controller of a grid-side converter of the direct-drive wind turbine, the specific process is as follows:
step 4.2.1: firstly, a general electromagnetic transient simulation model of the 1.5MW direct-drive wind turbine is established, and as shown in fig. 5, the parameters of the simulation model which are the same as those of the actual 1.5MW direct-drive wind turbine in table 2 are set. Carrying out a deep voltage drop test on a direct-drive wind turbine generator set running at a high wind speed to obtain active power test data P M And reactive power test data Q M . The input wind speed, the voltage drop depth and the voltage drop time which are the same as those of the actual direct-drive wind turbine generator low-voltage ride through test are set in the universal electromagnetic transient simulation model of the direct-drive wind turbine generator. In the embodiment, the bandwidth f of the current inner loop PI controller is identified by taking a genetic algorithm as an example c The population number of the genetic algorithm is 100, the cross probability is 0.8, and the mutation probability is 0.05. The identified objective function is:
in the formula, P S And Q S Respectively representing active and reactive power output by the simulation model, N s And N e The numbers of the first simulation data and the last simulation data and the test data of the parameter identification are respectively represented, and i represents the numbers of the simulation data and the test data.
Making the target function L in the identification process 1 Minimum, obtaining the bandwidth f of the current inner loop PI controller c And will identify the obtained f c Substituting formula (12) to calculate current inner loop PI controller parameter k P_c And k I_c 。
TABLE 2 main parameters of 1.5MW direct-drive wind turbine generator
Step 4.2.2: carrying out mild voltage drop test on a direct-drive wind turbine generator set running at low wind speed to obtain active power test data P M . The input wind speed, the voltage drop depth and the voltage drop time which are the same as those of the actual direct-drive wind turbine generator low-voltage ride through test are set in the universal electromagnetic transient simulation model of the direct-drive wind turbine generator. Method for identifying bandwidth f of direct-current voltage outer-loop PI controller by adopting genetic algorithm udc The identified objective function is:
making the target function L in the identification process 2 Minimum, obtain the bandwidth f of the external ring PI controller of the direct current voltage udc And will identify the obtained f udc Substituting formula (13) to calculate parameter k of external loop PI controller for DC voltage P_udc And k I_udc 。
Step 4.2.3: direct drive wind turbine generator set according to the steps 4.2.1 and 4.2.2Obtaining reactive power test data Q by low voltage ride through test M . The input wind speed, the voltage drop depth and the voltage drop time which are the same as those of the actual direct-drive wind turbine generator low-voltage ride through test are set in the universal electromagnetic transient simulation model of the direct-drive wind turbine generator. Method for identifying parameter k of reactive power outer loop PI controller by adopting genetic algorithm P_Q And k I_Q The identified objective function is:
making the target function L in the identification process 3 Obtaining the parameter k of the outer loop PI controller of the reactive power at minimum P_Q And k I_Q 。
After the steps 4.2.1, 4.2.2 and 4.2.3, the identification result of the parameter of the PI controller of the direct-drive wind turbine grid-side converter is obtained, as shown in table 3.
TABLE 3 identification values of PI controller parameters of grid-side converter of 1.5MW direct-drive wind turbine generator
Finally, verifying the accuracy of the universal electromagnetic transient simulation model of the direct-drive wind turbine generator:
the established universal electromagnetic transient simulation model of the direct-drive wind turbine generator and the parameter identification result are verified by taking test data of two groups of actual direct-drive wind turbine generators as an example, and the process is as follows: firstly, setting input wind speed, voltage drop depth and voltage drop time which are the same as those of an actual direct-drive wind turbine generator low-voltage ride-through test to obtain a voltage, current, active power and reactive power response curve of a general electromagnetic transient simulation model of the direct-drive wind turbine generator, and comparing an actual test result with a voltage, current, active power instantaneous value and reactive power instantaneous value of the general electromagnetic transient simulation model of the direct-drive wind turbine generator, wherein the actual test result and the voltage, current, active power and reactive power instantaneous value are respectively shown in fig. 6 (example 1) and fig. 7 (example 2), wherein fig. 6 (a), fig. 6 (b), fig. 6 (c) and fig. 6 (d) respectively correspond to voltage, current, active power and reactive power, and fig. 7 (a), fig. 7 (b), fig. 7 (c) and fig. 7 (d) respectively correspond to voltage, current, active power and reactive power. As can be seen from fig. 6 and 7, the established general electromagnetic transient simulation model of the direct-drive wind turbine generator is consistent with the transient response of the actual direct-drive wind turbine generator.
Further, the error between the output of the simulation model and the test data under the voltage drop is calculated according to the Chinese standard 'wind turbine generator electrical simulation model modeling guide rule'. The calculated electrical quantities comprise active power, reactive power and reactive component of current. The time range of the error calculation includes 5 intervals: a, B 1 ，B 2 ，C 1 And C 2 . Taking active power as an example, the division of 5 intervals is shown in fig. 8, wherein the division point t of the intervals B and C B1 And t C1 The last 20ms when the fluctuation in power or current comes within ± 10% of the mean value of the period is taken.
The error calculation formula is:
in the formula, X represents active power P, reactive power Q and current reactive component i q ，N Start And N End The numbers of the first simulation data and the last simulation data and the test data of the calculation interval are respectively represented, and i represents the numbers of the simulation data and the test data.
According to the Chinese standard 'guide rule for modeling electrical simulation model of wind turbine generator', if each parameter (P, Q and i) q ) The errors at the respective stages are all below the maximum allowable error shown in table 4, and the model is valid.
TABLE 4 maximum allowable error value (%)
| Parameter(s) | F 1max | F 2max | F 3max | F 4max | F 5max | F Gmax |
| P | 7 | 20 | 10 | 25 | 15 | 15 |
| Q | 5 | 20 | 7 | 25 | 10 | 15 |
| |
7 | 20 | 10 | 30 | 15 | 15 |
P, Q and i of the calculation example 1 corresponding to FIG. 6 and the calculation example 2 corresponding to FIG. 7 were calculated from the formula (21) q The results are shown in Table 5, with errors at the corresponding stages. As can be seen from Table 5, P, Q and i q The error at each stage is less than the maximum allowable error shown in table 4. Therefore, the universal electromagnetic transient simulation model of the direct-drive wind turbine generator, which is obtained by the method, can accurately represent the dynamic behaviors of different actual direct-drive wind turbine generator fault ride-through overall processes.
TABLE 5 error calculation results (%)
The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof, and it is therefore intended that all such changes and modifications be considered as within the spirit and scope of the appended claims.
Claims (9)
1. A general electromagnetic transient modeling method for a direct-drive wind turbine is characterized by comprising the following steps:
step 1: carrying out low voltage ride through test on the plurality of direct-drive wind turbine generators to obtain voltage, current, active power and reactive power responses of the plurality of direct-drive wind turbine generators under different voltage drop conditions, and obtaining a universal electromagnetic transient response curve of the whole fault ride through process of the direct-drive wind turbine generators according to the responses of the voltage, the current, the active power and the reactive power;
step 2: analyzing the dynamic behaviors of the active power and the reactive power in the whole fault ride-through process according to the universal electromagnetic transient response curve of the whole fault ride-through process of the direct-drive wind turbine generator system obtained in the step 1, and describing the dynamic behaviors of the active power and the reactive power in the whole fault ride-through process;
the dynamic behavior of the active power in the whole fault ride-through process is described as follows:
in the formula, P normal The active power representing the normal working state, and the corresponding time range is [ -, t [ ] 1 ]And [ t 7 ,～]，P fault Representing the active power during the duration of the fault, corresponding to a time interval t 1 ,t 3 ]，P re The active power representing the fault recovery process corresponds to the time ranges of t 3 ,t 7 ]T represents the current simulation run time; u. u g Representing the port voltage i of the direct-drive wind turbine P_normal Representing the active component of the current in the normal operating state, i P_fault Representing the current active component during the fault duration, I max Represents the maximum current, i Q_fault Representing the reactive component of the current during the fault duration; p (t) 3 ) Represents t 3 Active power at time P (t) 4 ) Represents t 4 Active power at a moment, r P Representing the rate of restoration of active power after fault clearance, P 0 Representing steady state active power before the fault;
the dynamic behavior of reactive power throughout the fault ride-through is described as follows:
in the formula, Q normal Representing the reactive power in normal working state, and the corresponding time range is [ -, t [ ] 1 ]And [ t 6 ,～]，Q fault Representing reactive power during the fault duration, corresponding to a time range t 1 ,t 3 ]，Q re The reactive power representing the fault recovery process corresponds to time ranges of t 3 ,t 6 ]；i Q_normal Is a reactive component of current under normal working condition, i Q_fault For the reactive component of the current during the fault duration, i lim_Q Limit value representing reactive component of current during fault, k being reactive power support coefficient, rootAccording to the grid-connected standard k is more than or equal to 1.5 set Representing a set voltage threshold, which is constant according to a grid-connection standard u set Is 0.9p.u., I n Representing rated current, i Q0 Representing the steady state current reactive component before the fault; q (t) 3 ) Represents t 3 Reactive power at time, Q (t) 5 ) Represents t 5 Reactive power at time, r Q Representing the rate of recovery of reactive power after fault clearing, Q 0 Representing steady state reactive power before a fault;
and 3, step 3: analyzing a reference value of a current active component and a reference value of a current reactive component according to the dynamic behavior formulas of the active power and the reactive power in the whole fault ride-through process obtained in the step 2, inputting the obtained reference values into a current controller of a grid-side converter of the universal electromagnetic transient simulation model of the direct-drive wind turbine generator, and automatically adjusting the dynamic behavior of the universal electromagnetic transient simulation model of the direct-drive wind turbine generator by utilizing the tracking action of the current controller of the grid-side converter;
and 4, step 4: and identifying fault ride-through control parameters and grid-side converter parameters of the direct-drive wind turbine generator system by adopting step-by-step identification.
2. The general electromagnetic transient modeling method for the direct-drive wind turbine generator set according to claim 1, characterized in that the fault ride-through overall process in the step 1 comprises a steady-state stage before a fault occurs, a fault continuation stage, a recovery stage after the fault is cleared until both active power and reactive power are recovered to a steady-state value, and a steady-state stage after the recovery stage is completed; and obtaining a general electromagnetic transient response curve of the direct-drive wind turbine generator in the whole fault ride-through process, wherein the general electromagnetic transient response curve comprises a response curve of voltage, instantaneous active power and instantaneous reactive power.
3. The direct-drive wind turbine generator universal electromagnetic transient modeling method according to claim 2, characterized in that the step 3 of resolving a reference value of a current active component and a reference value of a current reactive component according to the active power and reactive power obtained in the step 2 in a dynamic behavior formula of the fault ride-through overall process, inputting the obtained reference values into a current controller of a grid-side converter of the direct-drive wind turbine generator universal electromagnetic transient simulation model, and automatically adjusting a specific process of the dynamic behavior of the direct-drive wind turbine generator universal electromagnetic transient simulation model by using a tracking function of the current controller of the grid-side converter comprises the following steps:
when the direct-drive wind turbine generator system adopts the vector control of grid voltage orientation and the grid voltage is oriented to the d axis of the dq synchronous rotation reference coordinate system, the reference value of the current active component corresponds to the reference value i of the d axis component of the current controller dref Reference value of reactive component of current corresponds to reference value i of q-axis component of current controller qref (ii) a Reference value i of current active component dref Expressed as:
in the formula i dref_normal Reference value, i, representing the active component of the current in normal operation dref_fault Reference value, i, representing the current active component during the fault duration dref_re A reference value representing the active component of the current during the fault recovery process; k is a radical of formula P_udc And k I_udc Respectively representing the proportional and integral coefficients, u, of the external loop PI controller for DC voltage dcref Reference value, u, representing a DC voltage dc Representing a direct voltage, i qref_fault Reference value, r, representing the reactive component of the current during the fault duration id Representing the recovery rate of the active component of the current after the fault is cleared;
reference value i of the reactive component of the current qref Expressed as:
in the formula i qref_normal Reference value, i, representing the reactive component of the current in normal operation qref_re A reference value representing a reactive component of current during fault recovery; k is a radical of formula P_Q And k I_Q Respectively representing reactive powerProportional and integral coefficients, Q, of a rate outer loop PI controller ref Representing a reference value of reactive power, Q representing reactive power, r iq Representing the recovery rate of the reactive component of the current after the fault is cleared;
and (3) assigning values to d-axis and q-axis current reference values of a current controller in a grid-side converter of the direct-drive wind turbine generator set general electromagnetic transient simulation model according to a formula (3) and a formula (4), and automatically adjusting the dynamic behavior of the direct-drive wind turbine generator set general electromagnetic transient simulation model by using the current controller.
4. The general electromagnetic transient modeling method for the direct-drive wind turbine generator set according to claim 3, wherein the specific process of identifying the fault ride-through control parameters and grid-side converter parameters of the direct-drive wind turbine generator set by step-by-step identification in step 4 comprises the following steps:
step 4.1: analyzing and calculating fault ride-through control parameters of the direct-drive wind turbine generator according to voltage, current, active power and reactive power data of a low-voltage ride-through test of the direct-drive wind turbine generator;
step 4.2: and identifying and obtaining the parameters of the grid-side converter by adopting an optimization algorithm according to the voltage, current, active power and reactive power data of the low voltage ride through test of the direct-drive wind turbine generator.
5. The method for modeling direct-drive wind turbine generator set general electromagnetic transient state as defined in claim 4, wherein the fault ride-through control parameters of the direct-drive wind turbine generator set in the step 4.1 include a reactive power support coefficient k, and a recovery rate r of a current active component after fault clearing id Rate of recovery r of reactive component of current after fault clearance iq Active power recovery delay t after fault clearing dealy_P And reactive power support delay t after fault clearing dealy_Q 。
6. The general electromagnetic transient modeling method for the direct-drive wind turbine generator set according to claim 5, wherein the specific process of calculating the fault ride-through control parameters of the direct-drive wind turbine generator set according to the voltage, current, active power and reactive power data analysis of the low voltage ride-through test of the direct-drive wind turbine generator set in the step 4.1 comprises the following steps:
decomposing three-phase instantaneous voltage and three-phase instantaneous current of low voltage ride through test of an actual direct-drive wind turbine generator into a dq synchronous rotation reference coordinate system, wherein d-axis components and q-axis components of the three-phase instantaneous voltage are respectively u dM And u qM The d-axis component and the q-axis component of the three-phase instantaneous current are i respectively dM And i qM ；
And calculating a reactive power support coefficient k according to the test data of the light voltage drop:
k＝(i qM0 -i qM )/[I n (u set -u g )] (5)
in the formula i qM0 Test value, i, representing reactive component of current in normal operating condition qM A test value representing a reactive component of current during a fault duration; u. of gM A measurement value representing a voltage during a fault duration;
recovery rate r of active component of current after fault clearance id And the active power recovery delay t after the fault is cleared dealy_P And calculating according to the test data of the direct-drive wind turbine generator running at high wind speed under the condition of deep voltage drop:
in the formula i dM (t 7 ) Represents t 7 Test value of the active component of the current at a time i dM (t 4 ) Represents t 4 Testing the active component of the current at the moment;
recovery rate r of reactive component of current after fault clearance iq And reactive power recovery delay t after fault clearing dealy_Q Calculating according to the test data after the direct-drive wind turbine generator fault is cleared; when the direct-drive wind turbine generator continues to provide reactive support after the fault is cleared, t dealy_Q The calculation is as follows:
t delay_Q ＝t 5 -t 3 (7)
when the fault is cleared, the reactive power of the direct-drive wind turbine generator has the slope recovery characteristic, and t is the same 5 When the reactive power at the moment is not recovered to the steady-state reactive power before the fault, r iq The calculation is as follows:
r iq ＝[i qM (t 6 )-i qM (t 5 )]/(t 6 -t 5 ) (8)
in the formula i qM (t 6 ) Represents t 6 Test value of the reactive component of the current at that moment, i qM (t 5 ) Represents t 5 And (4) testing the reactive component of the current at the moment.
7. The method for modeling direct-drive wind turbine generator system general electromagnetic transient state as claimed in claim 4, 5 or 6, wherein in step 4.2, the grid-side converter parameters corresponding to the direct-drive wind turbine generator system include current inner loop PI controller parameter k P_c And k I_c Outer loop PI controller parameter k of DC voltage P_udc And k I_udc And a reactive power outer loop PI controller parameter k P_Q And k I_Q 。
8. The general electromagnetic transient modeling method for the direct-drive wind turbine generator set according to claim 7, wherein in step 4.2, the specific process of identifying and obtaining grid-side converter parameters by using an optimization algorithm according to voltage, current, active power and reactive power data of a low voltage ride through test of the direct-drive wind turbine generator set comprises the following steps:
step 4.2.1: carrying out deep voltage drop test on a direct-drive wind turbine generator set running at high wind speed to obtain active power test data P M And reactive power test data Q M Setting the input wind speed, the voltage drop depth and the voltage drop time which are the same as those of a low voltage ride through test in a universal electromagnetic transient simulation model of the direct-drive wind turbine generator; identification of bandwidth f of current inner loop PI controller by optimization algorithm c ；
Identifying the obtained bandwidth f of the current inner loop PI controller c Substituting formula (10) to calculate current inner loop PI controller parameter k P_c And k I_c ：
In the formula, L f And R f Respectively representing the inductance and the resistance of the network side filter, and obtaining the inductance and the resistance from a fan manufacturer;
step 4.2.2: carrying out mild voltage drop test on a direct-drive wind turbine generator set running at low wind speed to obtain active power test data P M Setting the input wind speed, the voltage drop depth and the voltage drop time which are the same as those of a low voltage ride through test in a universal electromagnetic transient simulation model of the direct-drive wind turbine generator; method for identifying bandwidth f of direct-current voltage outer-loop PI controller by adopting optimization algorithm udc ；
Identifying the obtained bandwidth f of the DC voltage outer loop PI controller udc Substituting formula (12) to calculate the parameter k of the external loop PI controller of the DC voltage P_udc And k I_udc ；
In the formula, C represents a direct current capacitor of a direct-drive wind turbine generator and is obtained from a fan manufacturer; u. of n Is the rated voltage of the grid;
step 4.2.3: according to the low voltage ride through test of the direct-drive wind turbine generator in the steps 4.2.1 and 4.2.2, reactive power test data Q are obtained M Setting the input wind speed, the voltage drop depth and the voltage drop time which are the same as those of the low voltage ride through test in a general electromagnetic transient simulation model; identification of reactive power outer loop parameter k by optimization algorithm P_Q And k I_Q 。
9. The general electromagnetic transient modeling method for the direct-drive wind turbine generator set according to claim 8, wherein in step 4.2.1, the bandwidth f of the current inner loop PI controller is identified by adopting an optimization algorithm c In the process of (3), identifying the objective function as:
in the formula, P S And Q S Respectively representing the active power and the reactive power output by the universal electromagnetic transient simulation model, N s And N e Respectively representing the serial numbers of the first simulation data and the last simulation data and test data of the parameter identification, wherein i represents the serial numbers of the simulation data and the test data;
step 4.2.2 the bandwidth f of the direct-current voltage outer loop PI controller is identified by adopting an optimization algorithm udc In the process of (2), the identified objective function is:
step 4.2.3 identifying the outer loop parameter k of the reactive power by adopting an optimization algorithm P_Q And k I_Q In the process of (2), the identified objective function is:
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