阅读说明：本技术 基于电压源型双馈风电机组有功振荡的抑制方法 (Voltage source type double-fed wind turbine generator active power oscillation-based suppression method ) 是由 谢震 杨曙昕 高翔 张兴 于 2021-08-31 设计创作，主要内容包括：本发明提供了一种基于电压源型双馈风电机组有功振荡的抑制方法,属于风力发电技术领域。本发明所述抑制方法在有功功率环中加入超前滞后环节,并根据惯性系数和阻尼系数来确定超前环节系数和滞后环节系数的值,该方法不依赖于对功率环参数的复杂设计,可以实现有功功率振荡的有效抑制。本发明在转子电流指令前使用了交叉结构,即定子电压d轴分量经PI调节器到转子电流指令q轴分量,定子电压q轴分量经PI调节器到转子电流指令d轴分量,削弱了交叉耦合对系统的影响。(The invention provides a voltage source type doubly-fed wind turbine generator active power oscillation-based suppression method, and belongs to the technical field of wind power generation. The suppression method adds a lead-lag link in the active power loop, and determines the values of the lead link coefficient and the lag link coefficient according to the inertia coefficient and the damping coefficient. The invention uses a cross structure before the rotor current instruction, namely, the stator voltage d-axis component is transmitted to the rotor current instruction q-axis component through the PI regulator, and the stator voltage q-axis component is transmitted to the rotor current instruction d-axis component through the PI regulator, thereby weakening the influence of cross coupling on the system.)

1. A method for suppressing active oscillation of a voltage source type doubly-fed wind turbine generator is characterized by comprising the following steps:

step 1, data sampling and data conversion

Step 1.1, sampling three-phase voltage u of stator of doubly-fed generator_A，u_B，u_CSampling doubly-fed generator stator three-phase current i_A，i_B，i_CSampling doubly-fed generator rotor three-phase current i_a，i_b，i_cSampling grid connection point three-phase voltage amplitude U_PCCSampling grid point angular frequency omega_pccAnd acquiring the angular speed omega of the rotor of the doubly-fed generator by utilizing a photoelectric encoder_r；

Step 1.2, dividing the three-phase voltage u of the stator of the doubly-fed generator_A，u_B，u_CSynchronous rotation coordinate transformation is carried out to obtain a stator voltage d-axis component u_sdAnd stator voltage q-axis component u_sq(ii) a The three-phase current i of the stator of the doubly-fed generator_A，i_B，i_CSynchronous rotation coordinate transformation is carried out to obtain a stator current d-axis component i_sdAnd stator current q-axis component i_sq(ii) a The three-phase current i of the doubly-fed generator rotor_a，i_b，i_cSynchronous rotation coordinate transformation is carried out to obtain a rotor current d-axis component i_rdAnd rotor current q-axis component i_rq(ii) a For the rotor angular velocity omega_rIntegral operation is carried out to obtain the rotation angle theta of the rotor_r；

Step 2, power calculation and filtering

Calculating power by using the formula (1) to obtain stator output active power P 'and stator output reactive power Q':

obtaining the active power P after passing through the low-pass filter and the reactive power Q after passing through the low-pass filter by using the formula (2):

in the formula (2), ω_fIs the cut-off frequency of the low-pass filter, s is the laplacian operator;

step 3, virtual synchronous lead-lag control

Obtaining angular frequency command omega by using formula (3)^*D-axis voltage command componentAnd q-axis voltage command componentThereby realizing the virtual synchronous lead-lag control:

in formula (3), P_refGiven value of active power, Q_refFor given value of reactive power, omega_nRated angular frequency, U, of the grid-connection point_nRated voltage for grid-connected point, J_dIs a coefficient of inertia, D_dAs damping coefficient, K_QIs the reactive power droop coefficient, K_uFor regulating the coefficient of reactive voltage, K_dFor the leading link coefficient, T_dIs a hysteresis link coefficient;

obtaining the lead link coefficient K by using the formula (4)_dAnd a hysteresis coefficient T_dThe value of (A) is as follows:

the stator rotation angle theta is obtained by the formula (5)₁Sum and slip angle θ₂：

Step 4, voltage and current control loop

Obtaining a rotor current command q-axis component i by using equation (6)_rq ^*And d-axis component i of rotor current command_rd ^*：

In formula (6), K_UpAs a voltage loop PI regulator PI_vProportional control coefficient of (1), K_UiAs a voltage loop PI regulator PI_vThe integral control coefficient of (1);

obtaining a rotor voltage q-axis component u by using the formula (7)_rqAnd d-axis component u of rotor voltage_rd：

In formula (7), K_IpFor current loop PI regulators PI_iProportional control coefficient of (1), K_IiFor current loop PI regulators PI_iThe integral control coefficient of (1);

step 5, generating a switching signal

Converting the d-axis component u of the rotor voltage_rdAnd the rotor voltage q-axis component u_rqGenerating switching signal S of inverter power device through SVPWM modulation_a，S_b，S_cThereby controlling the turn-on and turn-off of the power devices of the rotor-side inverter.

Technical Field

The invention relates to the field of wind power generation, in particular to a method for inhibiting active oscillation of a voltage source type double-fed wind turbine generator.

Technical Field

Wind power generation has been rapidly developed in recent years as a clean renewable energy source. With the increase of the single machine capacity of the wind power plant, the voltage and frequency support capability of the power grid is more and more insufficient, and under the condition of weak power grid, the operation performance of the wind power plant is deteriorated due to the performance deterioration of a phase-locked loop (PLL). Voltage source doubly-fed wind generators (VC-DFIGs) are receiving much attention due to their self-synchronous control characteristics, ability to actively support grid voltage and frequency. The voltage source type double-fed wind driven generator is a multi-loop cascade control system, and when an active power instruction and power grid frequency disturbance occur, improper voltage loop bandwidth parameters can cause serious active power oscillation and overshoot to influence grid-connected working performance.

Aiming at the problem of restraining the active power oscillation of the grid-connected point of the voltage source type doubly-fed wind generator, according to the prior published reference documents, some main research methods comprise:

document 1 "Li, m., Zhang, x., Guo, z., Wang, j., Li, f.: 'The Dual-Mode Combined Control string for Centralized Photovoltaic Grid-Connected Inverters Based on Double-Split transformer-Based Double-Split-transformer transformation', IEEETrans. But frequent handovers can cause interference.

Document 2 "j.alipoor, y.miura, and t.ise: ' Power system stabilization using virtual synchronization generator with alternating movement of inertia ', IEEE J.Emerg.Sel.Top.Power Electron, 2015, 3, (2), pp.451-458 ' (based on the Power system stabilization of virtual AC moment of inertia synchronous generators) proposes a virtual inertia bang-bang control strategy, and in each Power oscillation period, the virtual inertia is adjusted according to the dynamic change of the frequency change rate. The oscillation of active power is reduced while maintaining the power control accuracy. However, there is no general flexibility in design by parameter optimization of the power loop alone. When the power grid strength changes or hardware circuits change, the former parameters are no longer applicable.

Document 3 "l.harnefors, m.hinkkanen, u.riaz, f.m.m.rahman and l.zhang.: 'Robust analytical Design 0f Power-Synchronization Control', IEEE trans. ind. electron, 2019, 66, (8), pp.5810-5819 ″ (Robust analytical Design for Power Synchronization Control) proposes a Robust Design method for droop Control, which adjusts parameters of a Power loop to suppress active oscillation, but the method depends on the setting of the parameters and is sensitive to the change of the parameters.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention provides a voltage source type double-fed wind turbine generator set active oscillation suppression method, and the method is characterized in that the advance-lag control is added in an active power ring to realize the suppression of active power oscillation.

In order to achieve the above object, the present invention provides a method for suppressing active oscillation of a voltage source type doubly-fed wind turbine generator, comprising the following steps:

step 1, data sampling and data conversion

Step 1.1, sampling three-phase voltage u of stator of doubly-fed generator_A，u_B，u_CSampling doubly-fed generator stator three-phase current i_A，i_B，i_CSampling doubly-fed generator rotor three-phase current i_a，i_b，i_cSampling grid connection point three-phase voltage amplitude U_PCCSampling grid point angular frequency omega_pccAcquiring the double feed by using a photoelectric encoderAngular velocity omega of generator rotor_r；

Step 1.2, dividing the three-phase voltage u of the stator of the doubly-fed generator_A，u_B，u_CSynchronous rotation coordinate transformation is carried out to obtain a stator voltage d-axis component u_sdAnd stator voltage q-axis component u_sq(ii) a The three-phase current i of the stator of the doubly-fed generator_A，i_B，i_CSynchronous rotation coordinate transformation is carried out to obtain a stator current d-axis component i_sdAnd stator current q-axis component i_sq(ii) a The three-phase current i of the doubly-fed generator rotor_a，i_b，i_cSynchronous rotation coordinate transformation is carried out to obtain a rotor current d-axis component i_rdAnd rotor current q-axis component i_rq(ii) a For the rotor angular velocity omega_rIntegral operation is carried out to obtain the rotation angle theta of the rotor_r；

Step 2, power calculation and filtering

Calculating power by using the formula (1) to obtain stator output active power P 'and stator output reactive power Q':

obtaining the active power P after passing through the low-pass filter and the reactive power Q after passing through the low-pass filter by using the formula (2):

in the formula (2), ω_fIs the cut-off frequency of the low-pass filter, s is the laplacian operator;

step 3, virtual synchronous lead-lag control

Obtaining angular frequency command omega by using formula (3)^*D-axis voltage command componentAnd q-axis voltage command componentThereby realizing the virtual synchronous lead-lag control:

in formula (3), P_refGiven value of active power, Q_refFor given value of reactive power, omega_nRated angular frequency, U, of the grid-connection point_nRated voltage for grid-connected point, J_dIs a coefficient of inertia, D_dAs damping coefficient, K_QIs the reactive power droop coefficient, K_uFor regulating the coefficient of reactive voltage, K_dFor the leading link coefficient, T_dIs a hysteresis link coefficient;

obtaining the lead link coefficient K by using the formula (4)_dAnd a hysteresis coefficient T_dThe value of (A) is as follows:

the stator rotation angle theta is obtained by the formula (5)₁Sum and slip angle θ₂：

Step 4, voltage and current control loop

Obtaining a rotor current command q-axis component i by using equation (6)_rq ^*And d-axis component i of rotor current command_rd ^*：

In formula (6), K_UpAs a voltage loop PI regulator PI_vProportional control coefficient of (1), K_UiAs a voltage loop PI regulator PI_vThe integral control coefficient of (1);

obtaining a rotor voltage q-axis component u by using the formula (7)_rqAnd d-axis component u of rotor voltage_rd：

In formula (7), K_IpFor current loop PI regulators PI_iProportional control coefficient of (1), K_IiFor current loop PI regulators PI_iThe integral control coefficient of (1);

step 5, generating a switching signal

Converting the d-axis component u of the rotor voltage_rdAnd the rotor voltage q-axis component u_rqGenerating switching signal S of inverter power device through SVPWM modulation_a，S_b，S_cThereby controlling the turn-on and turn-off of the power devices of the rotor-side inverter.

Compared with the prior art, the invention has the beneficial effects that:

1. the invention effectively inhibits the oscillation and overshoot of the active power by utilizing the advance-lag control, reduces the sensitivity of the oscillation of the active power to the parameters of the power loop, improves the robustness of the system, avoids the design complexity of the parameters of the power loop when the condition of the power grid changes, and improves the dynamic performance of the voltage source type double-fed wind driven generator system.

2. The invention adopts the virtual synchronous control of the doubly-fed generator, the inner layer structure is the double closed-loop control of the voltage and current control loops, the stability problem caused by PLL when the power grid intensity is changed is avoided, the stability of the doubly-fed generator is obviously improved, the cross control is used before the rotor current is given, and the inconvenience brought to the system analysis by the coupling between the voltage and the current dq components is solved.

3. According to the invention, only a lead-lag control link is added in an active power loop, so that the suppression of active power oscillation is realized, and the realization mode is simple, convenient and effective.

Drawings

FIG. 1 is a flow chart of the inhibition method of the present invention.

FIG. 2 is a control diagram of the suppression method of the present invention.

FIG. 3 is a simulation of the suppression method of the present invention.

Detailed Description

In this embodiment, the frequency converter for the experimental platform drives a three-phase squirrel-cage asynchronous motor to drag the doubly-fed generator. The voltage source type double-fed wind generating set comprises a wind turbine, an induction motor, a rotor side converter and a direct current side capacitor. The rotor side converter is connected with a generator rotor, and wind energy captured by the wind turbine is converted into electric energy through the induction motor and is injected into a power grid.

The doubly-fed generator in the simulation platform is a wound-rotor induction motor, and the rated parameters are as follows: rated voltage 690V, rated stator current 1400A, rated rotor current 550A, and 2 pole pairs, stator resistance Rs ═ 0.0043 Ω, rotor resistance Rr ═ 0.0041 Ω, stator leakage reactance Ls ═ 0.0125H, rotor leakage reactance Lr ═ 0.0126H, and excitation reactance Lm ═ 0.0123H. The rated parameters of the rotor-side converter are as follows: rated capacity is 2MW, direct current side capacitance Cg is 0.161mf, network side inductance Lg is 0.35mH, direct current side rated voltage 1050V and switching frequency is 2.5 kHz. The power waveform of the platform is collected by an upper computer, and the number of sampling points is 4000/s.

The active power oscillation suppression method is applied to a voltage source type double-fed wind generating set, when the power grid strength fluctuates and the parameters of a power loop and a voltage current loop deviate, the active power oscillates, and the advance-lag control is added into an active power control loop of a rotor side converter, so that the active oscillation suppression method based on the voltage source type double-fed wind generating set is provided.

Fig. 1 is a flowchart of the suppression method of the present invention, fig. 2 is a control diagram of the suppression method of the present invention, and as can be seen from fig. 1 and fig. 2, the suppression method of the present invention based on the active oscillation of the voltage source type doubly-fed wind turbine generator includes the following steps:

step 1, data sampling and data conversion

Step 1.1, sampling three-phase voltage u of stator of doubly-fed generator_A，u_B，u_CSampling doubly-fed generator stator three-phase current i_A，i_B，i_CSampling double-fed generator rotorThree-phase current i_a，i_b，i_cSampling grid connection point three-phase voltage amplitude U_PCCSampling grid point angular frequency omega_pccAnd acquiring the angular speed omega of the rotor of the doubly-fed generator by utilizing a photoelectric encoder_r。

Step 1.2, dividing the three-phase voltage u of the stator of the doubly-fed generator_A，u_B，u_CSynchronous rotation coordinate transformation is carried out to obtain a stator voltage d-axis component u_sdAnd stator voltage q-axis component u_sq(ii) a The three-phase current i of the stator of the doubly-fed generator_A，i_B，i_CSynchronous rotation coordinate transformation is carried out to obtain a stator current d-axis component i_sdAnd stator current q-axis component i_sq(ii) a The three-phase current i of the doubly-fed generator rotor_a，i_b，i_cSynchronous rotation coordinate transformation is carried out to obtain a rotor current d-axis component i_rdAnd rotor current q-axis component i_sq(ii) a For the rotor angular velocity omega_rIntegral operation is carried out to obtain the rotation angle theta of the rotor_r。

In particular, the stator voltage d-axis component u_sdAnd stator voltage q-axis component u_sqThe coordinate conversion formula is as follows:

in formula (II), theta'₁The stator rotation angle is the last period;

the stator current d-axis component i_sdAnd stator current q-axis component i_sq u_sqThe coordinate conversion formula is as follows:

the d-axis component i of the rotor current_rdAnd rotor current q-axis component i_rqThe coordinate conversion formula of (c) is as follows:

in formula (II), theta'₂Is the slip angle of the previous cycle.

Step 2, power calculation and filtering

Calculating power by using the formula (1) to obtain stator output active power P 'and stator output reactive power Q':

obtaining the active power P after passing through the low-pass filter and the reactive power Q after passing through the low-pass filter by using the formula (2):

in the formula (2), ω_fThe cutoff frequency of the low-pass filter is s, the laplacian operator.

In this example, ω_f＝20π。

Step 3, virtual synchronous lead-lag control

Obtaining angular frequency command omega by using formula (3)^*D-axis voltage command componentAnd q-axis voltage command componentThereby realizing the virtual synchronous lead-lag control:

in formula (3), P_refGiven value of active power, Q_refFor given value of reactive power, omega_nRated angular frequency, U, of the grid-connection point_nRated voltage for grid-connected point, J_dIs a system of inertiaNumber, D_dAs damping coefficient, K_QIs the reactive power droop coefficient, K_uFor regulating the coefficient of reactive voltage, K_dFor the leading link coefficient, T_dIs a hysteresis coefficient.

Obtaining the lead link coefficient K by using the formula (4)_dAnd a hysteresis coefficient T_dThe value of (A) is as follows:

the stator rotation angle theta is obtained by the formula (5)₁Sum and slip angle θ₂：

In this example, P_ref＝2000000，Q_ref＝0，ω_n＝100π，U_n＝690，J_d＝2，D_d＝200，K_Q＝0.00001，K_u＝10000。

Step 4, voltage and current control loop

Obtaining a rotor current command q-axis component i by using equation (6)_rq ^*And d-axis component i of rotor current command_rd ^*：

In formula (6), K_UpAs a voltage loop PI regulator PI_vProportional control coefficient of (1), K_UiAs a voltage loop PI regulator PI_vThe integral control coefficient of (1).

Obtaining a rotor voltage q-axis component u by using the formula (7)_rqAnd d-axis component u of rotor voltage_rd：

In formula (7), K_IpFor current loop PI regulators PI_iProportional control coefficient of (1), K_IiFor current loop PI regulators PI_iThe integral control coefficient of (1).

In this example, K_Up＝0.2，K_Ui＝0.05，K_Ip＝0.2，K_Ii＝0.05。

Step 5, generating a switching signal

Converting the d-axis component u of the rotor voltage_rdAnd the rotor voltage q-axis component u_rqGenerating switching signal S of inverter power device through SVPWM modulation_a，S_b，S_cThereby controlling the turn-on and turn-off of the power devices of the rotor-side inverter.

In order to prove the technical effect of the invention, the invention is simulated. Fig. 3 is a simulation diagram of the suppression method of the present invention, Pref is an active power given value, the abscissa is time, and the ordinate is an active power per unit value. As can be seen from fig. 3, the oscillation of the active power is effectively suppressed by the method of the present invention compared to the state without the present invention.