CN114759575A

CN114759575A - Virtual synchronous double-fed fan subsynchronous oscillation suppression method and system

Info

Publication number: CN114759575A
Application number: CN202110989148.2A
Authority: CN
Inventors: 马静; 杨真缪; 杜汪洋; 周宜晴; 黄韦博; 邵鸿飞
Original assignee: North China Electric Power University
Current assignee: North China Electric Power University
Priority date: 2021-08-26
Filing date: 2021-08-26
Publication date: 2022-07-15

Abstract

The invention relates to a subsynchronous oscillation suppression method and a subsynchronous oscillation suppression system for a virtual synchronous double-fed fan, belongs to the technical field of wind power generation, and solves the problem that the subsynchronous oscillation suppression method in the prior art cannot solve subsynchronous oscillation in the virtual synchronous double-fed fan. The method comprises the following steps: collecting operation data of the virtual synchronous double-fed fan; based on the operation data, obtaining the energy dissipation rate of the virtual synchronous double-fed fan before the additional energy branch is added and the energy dissipation rate variation after the additional energy branch is added, and further obtaining the total energy dissipation rate of the virtual synchronous double-fed fan; and establishing a control parameter optimization model by taking the energy dissipation rate variable quantity after the additional energy branches are added as a target function constraint condition that the energy dissipation rate variable quantity is less than 0 and the total energy dissipation rate takes the minimum value, determining the control parameters of each additional energy branch, starting each additional energy branch after the parameters are determined, and realizing subsynchronous oscillation suppression of the virtual synchronous double-fed fan.

Description

Virtual synchronous double-fed fan subsynchronous oscillation suppression method and system

Technical Field

The invention relates to the technical field of wind power generation, in particular to a virtual synchronous double-fed fan subsynchronous oscillation suppression method and system.

Background

With the continuous improvement of the proportion of high-permeability wind power connected to a power grid, the adjusting capability of a power system is weakened due to the characteristic of weak inertia of a wind turbine generator, and the problem of stable and safe operation of the system is challenged. Due to the introduction of the virtual synchronous control technology, the fan has inertia and frequency response characteristics similar to those of a synchronous generator, the defect of weak inertia of the fan is improved to a certain extent, and the virtual synchronous control technology is a key technology for grid connection of the fan in the future.

The position of the double-fed wind power plant is mostly far away from a load center, electric energy is generally required to be transmitted to the load center through a long-distance power transmission line, and compensation capacitors are often connected in series in the power transmission line for improving the transmission efficiency of the electric energy, so that a sub-synchronous oscillation phenomenon easily occurs to a grid-connected system of the double-fed wind power plant, the stability of an electric power system is seriously threatened, and meanwhile, the safe operation of a double-fed wind power unit connected into the electric power system can also be influenced. At present, a great deal of research is carried out on the problem of subsynchronous oscillation of a doubly-fed fan grid-connected system in a traditional control mode, and subsynchronous oscillation is suppressed mainly through modes of adding damping control, adding a filtering device, changing electrical parameters and the like.

However, because the conventional doubly-fed wind turbine and the virtual synchronous doubly-fed wind turbine have different structures, the subsynchronous oscillation suppression method of the conventional doubly-fed wind turbine is not applicable to the virtual synchronous doubly-fed wind turbine, and currently, a corresponding research is still lacking for the subsynchronous oscillation suppression method of the virtual synchronous doubly-fed wind turbine.

Disclosure of Invention

In view of the foregoing analysis, embodiments of the present invention provide a method and a system for suppressing sub-synchronous oscillation of a virtual synchronous doubly-fed wind turbine, so as to solve the problem that the existing sub-synchronous oscillation suppression method cannot solve the sub-synchronous oscillation in the virtual synchronous doubly-fed wind turbine.

On one hand, the embodiment of the invention provides a virtual synchronous double-fed fan subsynchronous oscillation suppression method, which comprises the following steps:

collecting operation data of the virtual synchronous double-fed fan;

based on the operation data, obtaining the energy dissipation rate of the virtual synchronous double-fed fan before adding the additional energy branch and the energy dissipation rate variation after adding the additional energy branch, and further obtaining the total energy dissipation rate of the virtual synchronous double-fed fan;

and establishing a control parameter optimization model by taking the energy dissipation rate variable quantity after the additional energy branches are added as a target function constraint condition that the energy dissipation rate variable quantity is less than 0 and the total energy dissipation rate takes the minimum value, determining the control parameters of each additional energy branch, starting each additional energy branch after the parameters are determined, and realizing subsynchronous oscillation suppression of the virtual synchronous double-fed fan.

Further, the operation data of the virtual synchronous double-fed wind turbine comprises: the method comprises the steps of rotor current and voltage, inductance of a rotor and a stator, mutual inductance between the stator and the rotor, a stator voltage amplitude instruction value, deviation amount of subsynchronous angular velocity and synchronous angular velocity, a reference value of a named value of angular velocity, slip angular velocity of a doubly-fed fan, amplitude of disturbance current, total resistance of a transmission line, a direct current voltage steady-state value and active power.

Further, the added additional energy branch comprises:

additional energy branch 1: rotor current is introduced into the virtual synchronous control of the rotor, and after low-pass filtering, the rotor current is subjected to virtual resistance gain K_c1Outputting to a rotor voltage;

additional energy branch 2: active power is introduced into the virtual synchronous control of the rotor, and after high-pass filtering, the active power passes through an integral coefficient K_c2And outputting the phase angle to the virtual synchronous phase angle.

Further, the total energy dissipation ratio a 'of the virtual synchronous double-fed fan'_EnergyExpressed as:

a′_Energy＝a_Energy+Δa_Energy；

in the formula, a_EnergyIncreasing the energy dissipation ratio delta a before additional energy branch for the virtual synchronous double-fed fan_EnergyAdding additional energy to virtual synchronous double-fed fanMeasuring the energy dissipation rate variation after the branch.

Further, the energy dissipation ratio of the virtual synchronous doubly-fed wind turbine before adding the additional energy branch is expressed as:

wherein the content of the first and second substances,

in the formula i_rd0、i_rq0Is a steady-state value of the current amplitude of the d-axis and the q-axis of the rotor, u_rd0、u_rq0Is a steady state value of d-axis and q-axis voltage amplitudes of the rotor, L_rIs the rotor inductance, L_sIs a stator inductance, L_mIs a mutual inductance, U, between stator and rotor_sIs a stator voltage amplitude command value, U_r0A steady state value expressed as a rotor voltage amplitude command value, Δ ω is a deviation amount of the subsynchronous angular velocity from the synchronous angular velocity, ω_bIs a reference value, omega, of a nominal value of angular velocity_slipIs the slip angular velocity of the doubly-fed fan, D is the virtual damping coefficient, T_jIn order to be a virtual inertia time constant,

respectively PI control parameter, R of the reactive power control loop_vIs a virtual resistance, I_disFor the amplitude of the disturbance current, R_gIs the total resistance of the transmission line.

Further, the energy dissipation rate variation delta a of the virtual synchronous double-fed fan after the additional energy branch is added_EnergyExpressed as:

in the formula,. DELTA.a_{Energy_i}The method comprises the steps that the i-th type of energy dissipation rate variable quantity is introduced after an additional energy branch is added to the virtual synchronous double-fed fan, and n represents the total type number of the introduced energy dissipation rate variable quantity.

Further, the total number of categories n of the introduced energy dissipation ratio variation is 6; the various types of energy dissipation rate variations are expressed as follows:

virtual resistance and energy dissipation ratio variation Δ a on stator side_{Energy_1}Comprises the following steps:

virtual resistance and energy dissipation rate variation delta a of active power_{Energy_2}Comprises the following steps:

active power energy dissipation ratio variation Δ a_{Energy_3}Comprises the following steps:

active power and stator side energy dissipation ratio variation Δ a_{Energy_4}Comprises the following steps:

reactive power and energy dissipation ratio variation Δ a on the stator side_{Energy_5}Comprises the following steps:

energy dissipation ratio of reactive power and active powerVariation Δ a_{Energy_6}Comprises the following steps:

in the formula, K_c1For the virtual resistance gain of the additional energy branch 1, as a control parameter for the additional energy branch 1, K_c2The integral coefficient of the additional energy branch 2 is used as a control parameter of the additional energy branch 2.

Further, the control parameter optimization model is represented as:

in the formula of U_d0Is the steady-state value of the DC voltage of the virtual synchronous double-fed fan, U_rmin、U_rmaxThe upper limit and the lower limit of the steady state value of the rotor voltage during the steady state operation of the system, U_dmin、U_dmaxThe upper limit and the lower limit, omega, of the steady-state value of the direct-current voltage during the steady-state operation of the system_disFor sub-synchronous disturbance of angular velocity, K_min、K_maxTo control a parameter K_c1And K_c2Upper and lower limits of the value of (1).

Further, the subsynchronous oscillation suppression method further comprises the step of optimizing a function based on the control parameter optimization model and a bacterial population chemotaxis algorithm to obtain the optimal control parameter of the additional energy branch.

On the other hand, an embodiment of the present invention provides a virtual synchronous doubly-fed wind turbine subsynchronous oscillation suppression system, which is characterized by including:

the data acquisition module is used for acquiring the operation data of the virtual synchronous double-fed fan;

the total energy dissipation rate calculation module is used for obtaining the energy dissipation rate of the virtual synchronous double-fed fan before the additional energy branch is added and the energy dissipation rate variable quantity after the additional energy branch is added based on the operation data, and further obtaining the total energy dissipation rate of the virtual synchronous double-fed fan;

and the subsynchronous oscillation suppression processing module is used for establishing a control parameter optimization model by taking the energy dissipation rate variable quantity after the additional energy branches are added as less than 0 and the total energy dissipation rate of the virtual synchronous double-fed fan taking the minimum value as a target function constraint condition, determining the control parameters of each additional energy branch, and starting each additional energy branch after the parameters are determined, so as to realize subsynchronous oscillation suppression of the virtual synchronous double-fed fan.

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

according to the virtual synchronous double-fed fan subsynchronous oscillation suppression method and system, two additional energy branches are added on the basis of the original virtual synchronous double-fed fan structure, the energy dissipation rate of the virtual synchronous double-fed fan before the additional energy branches are added and the energy dissipation rate variation after the additional energy branches are added are obtained by collecting the operation data of the virtual synchronous double-fed fan, the total energy dissipation rate of the virtual synchronous double-fed fan is further obtained, the control parameters of each additional energy branch are determined, and subsynchronous oscillation suppression of the virtual synchronous double-fed fan is realized.

In the invention, the technical schemes can be combined with each other to realize more preferable combination schemes. Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and drawings.

Drawings

The drawings are only for purposes of illustrating particular embodiments and are not to be construed as limiting the invention, wherein like reference numerals are used to designate like parts throughout.

Fig. 1 is a schematic flow chart of a virtual synchronous doubly-fed wind turbine subsynchronous oscillation suppression method in embodiment 1 of the present invention;

fig. 2 is a schematic diagram of a network structure of a doubly-fed wind farm grid connection according to embodiment 1 of the present invention;

FIG. 3 is a schematic diagram of dynamic energy classification according to embodiment 1 of the present invention;

fig. 4 is a schematic diagram of a virtual synchronization control strategy for adding an additional energy branch according to embodiment 1 of the present invention;

FIG. 5 is a schematic diagram of a BCC algorithm-based control parameter optimization process in embodiment 1 of the present invention;

FIG. 6 is a graph showing the energy dissipation ratio of the dynamic energy of each control branch according to embodiment 3 of the present invention;

fig. 7 shows the active power of the virtual synchronous doubly-fed wind turbine in embodiment 3 of the present invention;

fig. 8 shows the instantaneous d-axis voltage at the rotor side according to embodiment 3 of the present invention;

fig. 9(a) shows the FFT analysis result before the additional energy branch is enabled in embodiment 3 of the present invention;

fig. 9(b) is the FFT analysis result after the additional energy branch is enabled according to embodiment 3 of the present invention;

fig. 10(a) shows the active power of the virtual synchronous doubly-fed wind turbine in embodiment 3 when the additional branch 2 is added and the series compensation degree is 20%;

fig. 10(b) shows the active power of the virtual synchronous doubly-fed wind turbine in embodiment 3 when the additional branch 2 is added and the series compensation degree is 40%;

FIG. 11 is a graph showing the effect of additional energy branch control parameters on the energy dissipation ratio of the system in accordance with embodiment 3 of the present invention;

fig. 12 shows the dynamic energy of the port of the virtual synchronous doubly-fed wind turbine in embodiment 3 of the present invention;

fig. 13 shows the energy dissipation ratio of the virtual synchronous doubly-fed wind turbine in embodiment 3 of the present invention;

fig. 14 shows the active power of the virtual synchronous doubly-fed wind turbine in embodiment 3 of the present invention;

fig. 15 shows instantaneous values of d-axis voltage on the rotor side in embodiment 3 of the present invention.

Detailed Description

The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate preferred embodiments of the invention and together with the description, serve to explain the principles of the invention and not to limit the scope of the invention.

Example 1

The invention discloses a method for suppressing subsynchronous oscillation of a virtual synchronous doubly-fed wind turbine, which comprises the following steps of:

and S1, acquiring the operation data of the virtual synchronous double-fed wind turbine.

In implementation, the operation data of the virtual synchronous doubly-fed wind turbine includes: the method comprises the steps of rotor current and voltage, inductance of a rotor and a stator, mutual inductance between the stator and the rotor, a stator voltage amplitude instruction value, deviation amount of subsynchronous angular velocity and synchronous angular velocity, a reference value of a named value of angular velocity, slip angular velocity of a doubly-fed fan, amplitude of disturbance current, total resistance of a transmission line, a direct current voltage steady-state value and active power.

And S2, based on the operation data, obtaining the energy dissipation rate of the virtual synchronous double-fed fan before the additional energy branch is added and the energy dissipation rate variable quantity after the additional energy branch is added, and further obtaining the total energy dissipation rate of the virtual synchronous double-fed fan.

In practice, the added additional energy branch comprises:

additional energy branch 1: rotor current is introduced into the rotor virtual synchronous control, and after low-pass filtering, the rotor current is subjected to virtual resistance gain K_c1And outputting the voltage to the rotor.

Additional energy branch 2: active power is introduced into the virtual synchronous control of the rotor, and after high-pass filtering, the active power is subjected to an integral coefficient K_c2And outputting the phase angle to the virtual synchronous phase angle.

In implementation, the total energy dissipation ratio a 'of the virtual synchronous doubly-fed wind turbine'_EnergyExpressed as:

a′_Energy＝a_Energy+Δa_Energy (1)

in the formula, a_EnergyIncreasing the energy dissipation ratio delta a before adding an additional energy branch for the virtual synchronous double-fed fan_EnergyAnd increasing the energy dissipation rate variable quantity after the additional energy branch is added to the virtual synchronous double-fed fan.

Specifically, the energy dissipation ratio of the virtual synchronous doubly-fed wind turbine before the additional energy branch is added is represented as:

wherein the content of the first and second substances,

in the formula i_rd0、i_rq0Is a steady-state value of the current amplitude of the d-axis and the q-axis of the rotor, u_rd0、u_rq0Is a steady state value of d-axis and q-axis voltage amplitudes of the rotor, L_rIs the rotor inductance, L_sIs a stator inductance, L_mIs a mutual inductance, U, between stator and rotor_sIs a stator voltage amplitude command value, U_r0A steady state value expressed as a rotor voltage amplitude command value, Δ ω is a deviation amount of the subsynchronous angular velocity from the synchronous angular velocity, ω_bIs a reference value, omega, of a nominal value of angular velocity_slipThe slip angular velocity of the doubly-fed wind turbine is D, the virtual damping coefficient is T_jIn order to be a virtual inertia time constant,

respectively PI control parameter, R of the reactive power control loop_vIs a virtual resistance, I_disTo the amplitude of the disturbance current, R_gIs the total resistance of the transmission line.

Specifically, the energy dissipation rate variation Δ a of the virtual synchronous doubly-fed wind turbine after the additional energy branch is added_EnergyExpressed as:

in the formula,. DELTA.a_{Energy_i}The method comprises the steps that the ith type of energy dissipation rate variable quantity is introduced after an additional energy branch is added to the virtual synchronous double-fed fan, and n represents the total type number of the introduced energy dissipation rate variable quantity.

More specifically, the total number of categories n of the introduced energy dissipation ratio variation is 6; the various types of energy dissipation rate variations are expressed as follows:

energy dissipation ratio variation Δ a of active power_{Energy_3}Comprises the following steps:

reactive power and stator-side energy dissipation ratio variation Δ a_{Energy_5}Comprises the following steps:

energy dissipation ratio variation Δ a of reactive power and active power_{Energy_6}Comprises the following steps:

It should be noted that, in step S2, the additional energy branch is designed through the following analysis, so as to obtain the energy dissipation rate of the virtual synchronous double-fed wind turbine before the additional energy branch is added and the energy dissipation rate variation after the additional energy branch is added, and further obtain the total energy dissipation rate of the virtual synchronous double-fed wind turbine:

and S21, establishing a virtual synchronous double-fed fan energy model.

For example, as shown in fig. 2, each doubly-fed wind generating set in the wind farm is connected to a collection bus of the wind farm through a 0.69kV/35kV transformer, and is connected to an infinite power grid through a 500kV series compensation power transmission line after being boosted by a 35kV/500kV transformer.

Therefore, the dynamic energy delta W of the port of the doubly-fed wind turbine is obtained_DFIGComprises the following steps:

ΔW_DFIG＝∫Δi_ddΔu_q-Δi_qdΔu_d+∫ΔPdΔθ (10)

in the formula,. DELTA.i_d、Δi_qThe instantaneous current variation of the d and q axes of the port, delta u_d、Δu_qThe instantaneous voltage variation of the d axis and the q axis of the port are respectively, delta P is the instantaneous active power variation of the port, and delta theta is the instantaneous variation of the phase angle of the port voltage.

The active power of the port of the double-fed fan is composed of the active power of the stator and the active power of the rotor, and because the frequency change of a power grid is very small and can be ignored under the condition of subsynchronous oscillation, and the instantaneous change rate of the voltage phase angle of the stator is almost 0, the integral of delta P to delta theta in the dynamic energy of the port of the double-fed fan can be changed from the instantaneous change quantity delta P of the state quantity of the rotor_rAnd Δ θ_rAnd (4) showing. At the same time, Δ P_rAnd Δ θ_rMainly affected by the rotor side converter control system. Thus, doubly-fedThe fan port dynamic energy can be represented in two parts:

ΔW_{DFIG_1}＝∫Δi_ddΔu_q-Δi_qdΔu_d (11)

ΔW_{DFIG_RSC}＝∫ΔP_rdΔθ_r (12)

in the formula,. DELTA.W_{DFIG_1}Dynamic energy composed of port voltage and current components is mainly related to network parameters; Δ W_{DFIG_RSC}The dynamic energy is composed of active power and a voltage phase angle and is mainly related to a rotor side control system; delta P_r、Δθ_rThe instantaneous variation of the active power of the rotor and the instantaneous variation of the voltage phase angle instruction value are respectively.

The linearized mathematical model of the doubly-fed wind turbine based on the virtual synchronous control strategy is as follows:

in the formula,. DELTA.p_s、Δq_sOutputting instantaneous variation of the measured values of the active power and the reactive power for the stator of the doubly-fed fan; omega_bA reference value for a nominal value of angular velocity; t is a unit of_jIs the virtual inertial time constant; d is a virtual damping coefficient; delta U_rInstantaneous variation of the rotor voltage amplitude instruction value; s represents the slip of the doubly-fed wind turbine; Δ i_rd、Δi_rqInstantaneous variable quantities of d and q axes of the rotor current of the doubly-fed fan are respectively; Δ u_rd、Δu_rqRespectively representing d and q axis instantaneous variation of the rotor voltage of the doubly-fed fan; the electrical quantity with "c" is the electrical quantity in the control coordinate system, and the electrical quantity without "c" is the electrical quantity in the electrical coordinate system. It should be noted that the current transformer has two coordinate systems, one being an electrical coordinate system based on the electrical system and one being a control coordinate system based on the control system.

The incremental equation for rotor current and voltage in a rotating dq axis coordinate system is:

in the formula,. DELTA.i_sd、Δi_sqAnd d and q axis instantaneous variation of the stator current of the doubly-fed fan are respectively.

Substituting a linear mathematical model of the doubly-fed wind turbine based on the virtual synchronous control strategy and an incremental equation of rotor current and voltage in a rotating dq axis coordinate system into port dynamic energy of the doubly-fed wind turbine to obtain:

according to the formula (18), the dynamic energy model includes the state quantity of the system and each parameter of the control system, and corresponding oscillation suppression measures can be provided by evaluating the influence of the dynamic energy of each part in the doubly-fed wind turbine on the stability of the system.

And S22, dividing control branches, and dividing the dynamic energy of the doubly-fed wind turbine based on the control branches.

According to the dynamic energy function of the port, the dynamic energy Δ W is converted into the power_DFIGDerivative with respect to time

Defined as the energy dissipation ratio a_EnergyThe positive and negative properties of the energy dissipation rate are used as the distinguishing indexes of the system stability, and the expression is as follows:

when a is_EnergyWhen the energy dissipation ratio is less than 0, the energy dissipation ratio is negative, the system consumes dynamic energy, and when the dynamic energy of the system reaches the minimum value, the system returns to the steady state again.

When a is_EnergyWhen the energy dissipation ratio is 0, the energy dissipation ratio is zero, the accumulated dynamic energy and the consumed dynamic energy of the system reach relative balance, and the system is in a critical stable state.

When a is_EnergyWhen the energy dissipation rate is more than 0, the energy dissipation rate is positive, the system accumulates dynamic energy, and when the dynamic energy of the system reaches the maximum value, the system is completely unstable.

By a control block diagram (a straight line connection part in fig. 4) and a mathematical model of a virtual synchronous control strategy, virtual synchronous control in a virtual synchronous double-fed fan can be divided into three control branches, namely an active power control branch, a reactive power control branch and a virtual resistance control branch, namely the active power control branch is composed of active power P_sAs the control branch of input quantity, the reactive power branch is formed from reactive power Q_sThe virtual resistance control branch is a control branch with Rv as an input quantity. The subsynchronous component output by the active power control branch circuit is delta theta_rThe subsynchronous component output by the reactive power control branch is delta U_rThe subsynchronous component output by the virtual resistance control branch circuit is an additional rotor voltage I_rabcR_v(ii) a Wherein, I_rabcThe three-phase current of the rotor abc of the doubly-fed fan is obtained. According to the linearized mathematical model of the doubly-fed wind turbine based on the virtual synchronous control strategy, it can be seen that there is a corresponding relationship between the mathematical model output of the virtual synchronous control strategy and each control branch, and the relationship is as follows: the active power control branch influences the q-axis component of the rotor voltage

The reactive power control branch influences the d-axis component of the rotor voltage

The virtual resistance control branch influences the dq-axis component Δ i of the rotor current_rd、Δi_rq。

Based on the above analysis, the dynamic energy model is divided into 6 parts of dynamic energy, and the energy classification is shown in fig. 3, and includes:

dynamic energy delta W jointly determined by reactive power control branch and stator side state quantity_{DFIG_1_Q}；

Dynamic energy delta W determined by reactive power control branch and active power control branch together_{DFIG_RSC_Q}；

Dynamic energy delta W determined by active power control branch and stator side state quantity together_{DFIG_1_P}；

Dynamic energy Δ W determined by active power control branch_{DFIG_RSC_P}；

The dynamic energy jointly determined by the virtual resistance control branch and the state quantity at the stator side is delta W_{DFIG_1_ii}；

The dynamic energy jointly determined by the virtual resistance control branch and the active power control branch is delta W_{DFIG_RSC_ii}。

And S23, solving the energy dissipation rate of each part of dynamic energy, and analyzing the contribution of each part of dynamic energy to the subsynchronous oscillation stability of the system by analyzing the positive and negative of each part of dynamic energy, so as to be used as the design basis of an additional energy branch.

Dynamic energy delta W jointly determined by reactive power control branch and stator side state quantity_{DFIG_1_Q}Its energy dissipation ratio a_{DFIG_1_Q}The expression of (a) is:

in the above formula, when the fan is in the generator state, ω is_slip< 0, so the coefficients are Δ ω and- ω_slipThe polynomial of (2) is a positive value, and the indexes are judged according to the system stability, and the two parts of dynamic energy are not beneficial to the system stability; the polynomial with the coefficient- Δ ω is negative and this portion of energy contributes to system stability. Thus, dynamic energyQuantity Δ W_{DFIG_1_Q}Positive and negative dynamic energy are included.

Dynamic energy delta W determined by reactive power control branch and active power control branch together_{DFIG_RSC_Q}Its energy dissipation ratio a_{DFIG_RSC_Q}The expression of (a) is:

in the above formula, PI control parameters are included

The polynomial of (a) is a negative value, and the part of dynamic energy is beneficial to the stability of the system; containing PI control parameters

And R_vThe polynomial of (a) is positive, and the dynamic energy of the part is not beneficial to the stability of the system. Therefore, the dynamic energy Δ W_{DFIG_RSC_Q}Positive and negative dynamic energy are included.

Dynamic energy delta W jointly determined by active power control branch and stator side state quantity_{DFIG_1_P}Its energy dissipation ratio a_{DFIG_1_P}The expression of (c) is:

in the formula (I), the compound is shown in the specification,

in the above formula, the coefficients are Δ ω and- ω_slipThe polynomial of (a) is a positive value, and the dynamic energy of the two parts is not beneficial to the stability of the system; the polynomial with the coefficient- Δ ω is negative and this portion of energy contributes to system stability. Therefore, the dynamic energy Δ W_{DFIG_1_P}Positive and negative dynamic energy are included.

Dynamic energy Δ W determined only by the active power control branch_{DFIG_RSC_P}Its energy dissipation ratio a_{DFIG_RSC_P}The expression of (c) is:

in the above formula, the partial energy only includes a negative polynomial, which is beneficial to the stability of the system. Therefore, the dynamic energy Δ W_{DFIG_RSC_P}Only negative dynamic energy is contained.

The dynamic energy jointly determined by the virtual resistance control branch and the stator side state quantity is delta W_{DFIG_1_ii}Its energy dissipation ratio a_{DFIG_1_ii}The expression of (c) is:

in the formula (I), the compound is shown in the specification,

in the above formula, the included polynomials are all positive values, and the overall coefficient includes- ω_slipThe overall value is positive, and this part of energy is not good for system stability. Therefore, the dynamic energy Δ W_{DFIG_1_ii}Containing only positive dynamic energy.

The dynamic energy jointly determined by the virtual resistance control branch and the active power control branch is delta W_{DFIG_RSC_ii}Its energy dissipation ratio a_{DFIG_RSC_ii}The expression of (a) is:

in the above formula, the included polynomials are all positive values, and this part of energy is not favorable for the stability of the system. Therefore, the dynamic energy Δ W_{DFIG_RSC_ii}Containing only positive dynamic energy.

From the above analysis, it can be seen that the virtual resistance control branch is directly controlledDynamic energy Δ W_{DFIG_1_ii}For positive dynamic energy, the active power control branch directly controls the dynamic energy Δ W_{DFIG_RSC_P}The energy is negative dynamic energy, and the coupling relationship between the two parts of energy and other control branches is weak.

Dynamic energy Δ W_{DFIG_1_Q}And Δ W_{DFIG_1_P}Energy dissipation ratio of a_{DFIG_1_Q}And a_{DFIG_1_P}Are relatively close in absolute value, therefore, it can be considered that a is_{DFIG_1_Q}≈a_{DFIG_1_P}. At a_{DFIG_RSC_P}Middle, Δ ω_bIs the famous difference between the subsynchronous angular velocity and the synchronous angular velocity, and the magnitude is generally 10²This results in a_{DFIG_RSC_P}Is greater than a_{DFIG_1_P}And a_{DFIG_RSC_Q}The absolute value of the dynamic energy of the two parts determined by the reactive power control branch is much smaller than that of the other dynamic energy, and the influence on the system stability is smaller. In addition, the dynamic energy of the two parts is also influenced by other control branches, so that the reactive power control branch is not suitable for energy compensation as a key control branch.

In summary, the virtual resistance control branch and the active power control branch can be used as key control branches for energy compensation; and the energy dissipation ratio a before the additional energy branch can be obtained_Energy＝a_{DFIG_1_Q}+a_{DFIG_RSC_Q}+a_{DFIG_1_P}+a_{DFIG_RSC_P}+a_{DFIG_1_ii}+a_{DFIG_RSC_ii}I.e. equation (2).

And S24, constructing an additional energy control branch.

The basic idea of the additional energy control branch is to reduce the positive dynamic energy and increase the negative dynamic energy, so that the dynamic energy in the system is minimized, and the stability level of the system is improved. From the analysis of the energy dissipation rates of the respective dynamic energies in step S23, the dynamic energy Δ W can be based_{DFIG_1_ii}、ΔW_{DFIG_RSC_P}Compensating the virtual resistance control branch and the active power control branch, and adding

additional energy branches

1 and 2, wherein the specific analysis is as follows:

(1) additional energy branch 1

As can be seen from the view of figure 3,dynamic energy Δ W_{DFIG_1_ii}The additional energy branch 1 is designed according to the dynamic energy without coupling relation with other control branches, and the dynamic energy delta W is used for passing_{DFIG_RSC_ii}And (6) checking.

From a to a_{DFIG_1_ii}It is understood that the absolute values thereof are mainly related to

Amplitude coefficient A of₁、A₂、A₃、A₄Is related to the size of (A), wherein₂、A₄The value of (1) is reduced by controlling the additional energy branch (1) in the branch through the virtual resistor, thereby reducing the dynamic energy (AW)_{DFIG_1_ii}The expression output by the changed virtual control strategy is as follows:

in the formula, K_c1As a control parameter for the additional energy branch 1.

Dynamic energy delta W after adding additional energy branch 1_{DFIG_1_ii}Energy dissipation ratio of a'_{DFIG_1_ii}Comprises the following steps:

it can be obtained that the dynamic energy delta W is obtained after the additional energy branch 1 is added_{DFIG_1_ii}The energy dissipation ratio variation amount of (a) is:

by increasing the energy dissipation ratio a of the additional energy branch 1_{DFIG_1_ii}And a'_{DFIG_1_ii}By comparison, it can be seen that the dynamic energy Δ W_{DFIG_1_ii}The energy dissipation ratio of (1) is reduced due to the addition of the additional energy branch, and the stability of the subsynchronous oscillation of the system is increased.

In addition, verification is requiredThe influence of the additional branch on other dynamic energy, namely the dynamic energy delta W after the additional energy branch 1 is added_{DFIG_RSC_ii}New dynamic energy will be introduced with a variable amount of energy dissipation ratio deltaa_{DFIG_RSC_ii}The expression is:

from the above formula, it can be seen that the additional energy branch 1 has a dynamic energy Δ W_{DFIG_RSC_ii}The dynamic energy introduced in the process is negative dynamic energy, and the stability of the system can be increased.

(2) Additional energy branch 2

As can be seen from fig. 3, among the dynamic energies affected by the active power control branch, the dynamic energy Δ W_{DFIG_RSC_P}Mutually decoupled with other control branches, designing an additional energy branch 2 according to the dynamic energy, and passing the dynamic energy delta W_{DFIG_RSC_Q}、ΔW_{DFIG_1_P}And Δ W_{DFIG_RSC_ii}And (6) checking.

From a to a_{DFIG_RSC_P}It can be seen that the dynamic energy Δ W_{DFIG_RSC_P}Is negative dynamic energy, an additional energy branch 2 in the active control branch is needed to increase the energy, so that the stability of the system is improved. The output quantity of the active power control branch circuit after the additional energy branch circuit 2 is added is as follows:

in the formula, K_c2As a control parameter for the additional energy branch 2.

Dynamic energy delta W after adding additional energy branch 2_{DFIG_RSC_P}Energy dissipation ratio of a'_{DFIG_RSC_P}Comprises the following steps:

it can be obtained that the dynamic energy Δ W is obtained after adding the additional energy branch 2_{DFIG_RSC_P}The energy dissipation ratio variation amount of (a) is:

from a'_{DFIG_RSC_P}The expression shows that the additional energy branch 2 has dynamic energy delta W_{DFIG_RSC_P}A part of negative dynamic energy is introduced, and the stability level of the system is improved.

Two energy branches are added in the virtual synchronous control system, the influence of the two added branches on other dynamic energy needs to be verified after the two added branches are added together, and the dynamic energy delta W is obtained after the two added energy branches are added_{DFIG_1_P}New dynamic energy will be introduced with a variable amount of energy dissipation ratio deltaa_{DFIG_1_P}The expression is as follows:

Δa_{DFIG_1_P}is determined by the control parameters K of the two additional energy branches_c1、K_c2Jointly, the two control parameters can be reasonably set to be within the range of delta W_{DFIG_1_P}Negative dynamic energy is introduced, and the stability level of the system is improved.

Dynamic energy delta W after adding two additional energy branches_{DFIG_1_Q}New dynamic energy will be introduced with a variable amount of energy dissipation ratio deltaa_{DFIG_1_Q}The expression is as follows:

Δa_{DFIG_1_Q}the positive and negative of (A) are also determined by the control parameters K of the two additional energy branches_c1、K_c2Jointly, it is decided that only a reasonable setting of these two control parameters can be achieved at Δ W_{DFIG_1_Q}Negative dynamic energy is introduced, and the stability level of the system is improved.

Dynamic state after adding two additional energy branchesEnergy Δ W_{DFIG_RSC_Q}New dynamic energy will be introduced with a variable amount of energy dissipation ratio deltaa_{DFIG_RSC_Q}The expression is as follows:

Δa_{DFIG_RSC_Q}the positive and negative of (A) are also determined by the control parameters K of the two additional energy branches_c1、K_c2Jointly, it is decided that the two control parameters can only be set properly at Δ W_{DFIG_RSC_Q}Negative dynamic energy is introduced, and the stability level of the system is improved.

Therefore, after the

additional energy branches

1 and 2 are added, 6 types of energy dissipation rate variable quantities are introduced, namely the energy dissipation rate variable quantities delta a of the virtual resistor and the stator side respectively_{Energy_1}＝Δa_{DFIG_1_ii}(ii) a Virtual resistance and energy dissipation rate variation delta a of active power_{Energy_2}＝Δa_{DFIG_RSC_ii}(ii) a Energy dissipation ratio variation Δ a of active power_{Energy_3}＝Δa_{DFIG_RSC_P}(ii) a Active power and stator side energy dissipation ratio variation Δ a_{Energy_4}＝Δa_{DFIG_1_P}(ii) a Reactive power and energy dissipation ratio variation Δ a on the stator side_{Energy_5}＝Δa_{DFIG_1_Q}(ii) a Energy dissipation ratio variation Δ a of reactive power and active power_{Energy_6}＝Δa_{DFIG_RSC_Q}. The energy dissipation rate variation delta a of the virtual synchronous double-fed fan after the additional energy branch is added can be obtained_EnergyExpressed as:

Therefore, the control block diagram after the two additional energy branches are added is shown in fig. 4. The control equation of the active power branch circuit after the additional energy branch circuit is added is as follows:

in the formula, P_mActive power output for prime mover, P_sActive power is output for the stator of the doubly-fed wind turbine, wherein omega is the virtual stator angular velocity and omega_sRated angular velocity, omega, of the stator_rIs the angular velocity, θ, of the doubly-fed wind turbine rotor_rThe rotor voltage phase angle instruction value is obtained.

It can be known from the above control equation that the introduction of the additional control branch 2 introduces a new additional quantity into the rotor voltage phase angle, which inevitably affects the frequency modulation characteristics of the virtual synchronous doubly-fed wind turbine, and to reduce this effect, a high-pass filter needs to be further introduced to filter out the fundamental frequency component in the active power, and only the component of the subsynchronous frequency band is reserved, and the position of the filter is shown by the dotted line in fig. 4. In addition, the rotor voltage increment introduced by the additional control branch 2 at the rotor side converter is relatively large, which affects the steady-state operation characteristic of the doubly-fed wind turbine, so that a low-pass filter is required to be used, only the sub-synchronous component is allowed to pass, and the influence on the steady-state operation characteristic is reduced, wherein the position of the filter is shown by a dotted line in fig. 4.

From the above analysis, it can be derived that the added energy additional energy branch is:

additional energy branch 1: rotor current is introduced into virtual control of the rotor, and after low-pass filtering, the rotor current is subjected to virtual resistance gain K_c1And outputs to the rotor voltage.

Additional energy branch 2: active power is introduced into the virtual synchronous control of the rotor, and after high-pass filtering, the active power is subjected to integral coefficient K_c2And outputting the phase angle to the virtual synchronous phase angle.

The total energy dissipation rate of the virtual synchronous double-fed fan after the additional energy branch is added is as follows:

a′_Energy＝a_Energy+Δa_Energy。

s3, establishing a control parameter optimization model by taking the energy dissipation rate variable quantity after the additional energy branches are added as a target function constraint condition that the energy dissipation rate variable quantity is smaller than 0 and the total energy dissipation rate minimum value is taken as a target function constraint condition, determining the control parameters of each additional energy branch, starting each additional energy branch after the parameters are determined, and achieving subsynchronous oscillation suppression of the virtual synchronous double-fed fan.

In practice, the control parameter optimization model is expressed as:

in the formula of U_r0Is a steady state value of a virtual synchronous doubly-fed wind turbine rotor voltage command value, U_d0Is the steady-state value of the DC voltage of the virtual synchronous double-fed fan, U_rmin、U_rmaxThe upper limit and the lower limit of the steady state value of the rotor voltage during the steady state operation of the system, U_dmin、U_dmaxThe upper limit and the lower limit, omega, of the steady state value of the direct current voltage during the steady state operation of the system_disFor sub-synchronous disturbance of angular velocity, K_min、K_maxFor controlling a parameter K_c1And K_c2Preferably, U is selected from the upper and lower limits of_rmin、U_rmax、U_dmin、U_dmaxIs set as U_r0And U_d0. + -. 5% of.

It can be understood that the control parameters of the additional energy branch need to satisfy the upper and lower limits thereof, so as to avoid overshoot phenomenon of the control system and cause new oscillation of the system.

Specifically, the additional energy branch may affect the amplitude of the rotor voltage, and a constraint condition needs to be added to reduce the influence on the stable operation characteristic of the fundamental frequency. In addition, the control system directly acts on a rotor side converter of the virtual synchronous double-fed fan, the change of the control structure can affect the direct-current bus voltage, reasonable control parameters need to be configured, the change quantity of the direct-current bus voltage is less than 5%, the steady-state operation characteristic of the additional control on the double-fed fan is reduced as much as possible, and inequality constraint conditions which need to be met are as follows:

in addition, the oscillation frequency of the subsynchronous oscillation is generally mainly from 5Hz to 45Hz, and therefore, the oscillation component angular velocity ω of the system_disUpper and lower limits are also desirable. And in order to accelerate the calculation speed of optimization, the energy introduced by the additional energy branch is negative dynamic energy, namely the variation of the introduced energy dissipation rate of each type is less than 0, and the constraint condition of the objective function is taken as the energy.

In implementation, the subsynchronous oscillation suppression method further comprises the step of optimizing a function based on the control parameter optimization model and the bacterial population chemotaxis algorithm to obtain the optimal control parameter of the additional energy branch.

Specifically, according to the control parameter optimization model, a function optimization method of a Bacterial Colony Chemotaxis (BCC) algorithm is combined to obtain the optimal control parameters of the additional energy branch, and the process is shown in fig. 5 and includes the following steps:

s31, initializing the positions of all bacteria, and establishing a variable space; wherein the bacteria represent the control parameters of the additional energy branch.

Calculating the total energy dissipation rate according to the operation data of the virtual synchronous double-fed fan, and further determining a control parameter K of the additional energy branch according to a control parameter optimization model_c1,K_c2The location of the randomly distributed bacterial population.

S32, determining convergence accuracy epsilon and further determining system parameter T₀、b、τ_cThe following were used:

T₀＝ε^0.3×10^-1.73，

b＝T₀(T₀ ^-1.54×10^0.6)，

τ_c＝(b/T₀)^0.31×10^1.16，

in the formula, T₀Is a parameter related to the accuracy of the calculation, τ_cIs the time related to the size of the turning angle of the moving direction of the bacteria, and b is a parameter which is not related to the dimension;

specifically, the convergence accuracy may be set as needed, and preferably, the convergence accuracy ∈ is 0.136.

S33, starting from the initial position, carrying out individual optimization, specifically:

first, a moving step l is determined, where l constant t is the bacteria moving time.

Wherein the bacteria migration time t satisfies an exponential distribution, i.e.

In the formula, f_prIs the difference in the function value of T of the current point and the previous point,/_prIs the modulus of the vector connecting the current point and the last point in the variable space.

Then, determining an included angle alpha between the new direction and the original trajectory, and deflecting leftwards or rightwards according to the new direction respectively obeying the following two Gaussian probability distributions (normal distributions):

where, it is desired that μ ═ e (x) and variance

Are respectively given as follows:

if it is

μ＝62°(1-cos(θ)),σ＝26°(1-cos(θ)),

In the formula, t_prThe duration of a trajectory movement on the bacteria.

If it is

μ＝62°,σ＝26°。

Finally, the bacteria advance along the step and direction determined above until the initial convergence accuracy ε is satisfied_beginThereby obtaining

The position of (a).

S34, for the bacteria i in the k steps of moving, sensing the positions of other bacteria with smaller energy dissipation rate around the bacteria i (calculating the total energy dissipation rate, obtaining smaller energy dissipation rate through comparison, and further obtaining the bacteria positions), and determining the center points of the bacteria i

And assuming the distance of movement of itself towards this centre point

Determining position

Wherein rand () is a random moving step size,

indicating that it is moving in the direction of the center point (i.e., the forward direction).

S35, determining the position of the bacterium i in the k +1 step according to the moving direction of the bacterium i in the moving step number k

That is, the step S34 is repeated to determine the moving direction and step length of the required forward movement, so as to obtain

S36, calculating the energy dissipation ratio a 'of the system behind the additional energy branch'_EnergyIn position

And position

If a function value of

Then the bacteria migrate at the k +1 step to

Otherwise move to

S37, repeating the steps S33-S36 until the difference value between the energy dissipation rate of the current position and the previous position is smaller than or equal to the convergence accuracy epsilon, and obtaining the additional control parameter K when the total energy dissipation rate of the system is minimum_{c1_min},K_{c2_min}。

The control parameters obtained after parameter optimization are applied to the two additional energy branches, the subsynchronous oscillation cooperative control strategy of the multiple additional energy branches is realized, and the subsynchronous oscillation suppression effect of the virtual synchronous double-fed fan is better.

Compared with the prior art, the virtual synchronous double-fed fan subsynchronous oscillation suppression method provided by the invention has the advantages that two additional energy branches are added on the basis of the original virtual synchronous double-fed fan structure, the energy dissipation rate of the virtual synchronous double-fed fan before the additional energy branches are added and the energy dissipation rate variable quantity after the additional energy branches are added are obtained by collecting the operation data of the virtual synchronous double-fed fan, the total energy dissipation rate of the virtual synchronous double-fed fan is further obtained, the control parameters of each additional energy branch are further determined, and subsynchronous oscillation suppression of the virtual synchronous double-fed fan is realized.

Example 2

The invention discloses a virtual synchronous double-fed fan subsynchronous oscillation suppression system, which comprises the following components:

It should be noted that the embodiment of the system and the embodiment of the method are based on the same principle, and the related points can be referred to each other and achieve the same technical effect.

Example 3

In order to verify the effectiveness of the virtual synchronous doubly-fed wind turbine subsynchronous oscillation suppression method and system provided in

embodiments

1 and 2 of the present invention, a specific embodiment 3 of the present invention builds a virtual synchronous doubly-fed wind turbine as shown in fig. 2. Each double-fed wind generating set in the wind power plant is connected to a wind power plant collecting bus through a 0.69kV/35kV transformer, is boosted through a 35kV/500kV transformer and is connected to an infinite power grid through a 500kV series compensation power transmission line, wherein R, L, C is the total resistance, the inductance and the capacitance of the power transmission line respectively. The main parameters of the virtual synchronous doubly-fed wind turbine are shown in the following table.

In order to verify the effectiveness and the correctness of the subsynchronous oscillation suppression method provided by the method, firstly, the energy dissipation rate of each part of energy in the embodiment 1 is calculated according to the state quantity of the port of the measuring fan, and the influence of each part of dynamic energy on the stability of the system is verified.

In the case of system oscillation divergence, the energy dissipation ratios of the six types of dynamic energy determined by the three control branches are calculated according to embodiment 1, as shown in fig. 6.

As can be seen from FIG. 6, the dynamic energy Δ W_{DFIG_1_ii}、ΔW_{DFIG_RSC_ii}Constant positive energy dissipation ratio, dynamic energy Δ W_{DFIG_RSC_P}Is constantly negative, although the dynamic energy Δ W_{DFIG_1_Q}、ΔW_{DFIG_RSC_Q}、ΔW_{DFIG_1_P}The energy dissipation ratio of (a) is always positive, but its absolute value is much smaller than other dynamic energies. When t is 2s, the energy dissipation ratios of the two parts of dynamic energy determined by the reactive power control branch are respectively 2.45 × 10^-11、3.29×10^-11(ii) a The energy dissipation rates of the two parts of dynamic energy determined by the active power control branch circuits are respectively 5.74 multiplied by 10^-11、-8.27×10^-11(ii) a The energy dissipation rates of the two parts of dynamic energy determined by the virtual resistance control branch circuit are respectively 2.10 multiplied by 10^-10、1.59×10^-10. From the absolute value of the energy dissipation ratio, the dynamic energy Δ W_{DFIG_1_Q}、ΔW_{DFIG_RSC_Q}The influence on the system stability is small, and the system cannot be used as the key dynamic energy of the design basis of the additional energy branch. The results are consistent with the analytical results in example 1.

Then, respectively adding an additional energy branch circuit 1 and an additional energy branch circuit 2 into a control strategy of the virtual synchronous double-fed fan, and verifying the effectiveness of each additional energy branch circuit; and simultaneously adding two additional energy branches to verify the effectiveness of the combined action of the two branches.

(1) Adding additional energy branch 1

Adding subsynchronous oscillation disturbance when t is 1s, adding an additional energy branch 1 after 1s, and controlling a parameter K of the additional energy branch_c10.09. The active power output by the virtual synchronous double-fed wind turbine is shown in fig. 7, the d-axis voltage instantaneous value on the rotor side is shown in fig. 8, and the FFT analysis results before and after the additional energy branch is put into operation are shown in fig. 9.

Subsynchronous oscillation of the system due to additional energyThe input of the measuring branch 1 is changed from oscillation divergence to oscillation convergence, and the system enters a stable state again. Meanwhile, as can be seen from the FFT analysis result of fig. 9, before the additional energy branch 1 is put into use, a subsynchronous oscillation component with 14Hz as a main component and a small amount of supersynchronous oscillation component with 84Hz exist in the system, and after the additional energy branch 1 is put into use, the subsynchronous oscillation component in the system disappears, so that the comparison between the above and the additional energy branch 1 has the energy for suppressing subsynchronous oscillation. However, in fig. 8, the steady-state value of the instantaneous value of the rotor-side d-axis voltage greatly changes due to the input of the additional energy branch 1, and u is before the branch is input_rd0U is-0.221 after branch is put into_rd0The variation was 20.81%, which is well outside the allowable range, 0.175.

In conclusion, the additional energy branch 1 has better subsynchronous oscillation energy suppression, but if the parameter setting is too large, the steady-state operation characteristic of the virtual synchronous doubly-fed wind turbine is affected.

(2) Adding additional energy branch 2

When t is equal to 1s, subsynchronous oscillation disturbance is added, and after 1s, an additional energy branch 2 is added, and the control parameter K of the additional energy branch _c210. And respectively putting into control strategies when the series compensation degree is 20% and 40%, verifying the capability of the additional energy branch 2 for inhibiting subsynchronous oscillation, wherein the active power output by the virtual synchronous double-fed fan is shown in fig. 10.

As can be seen from fig. 10(a), when the series compensation degree is small (20%), the subsynchronous oscillation can be suppressed well by adding the additional energy branch 2. As can be seen in fig. 10(b), when the series compensation degree is large (40%), the additional energy branch 2 is added to suppress the divergence of the subsynchronous oscillation, and the active power output by the doubly-fed wind turbine does not tend to converge, but oscillates at a constant amplitude.

In summary, the additional energy branch 2 has the capability of suppressing subsynchronous oscillation, but cannot effectively suppress oscillation when the oscillation divergence degree is large.

It can be seen that the two additional energy branches are not enough to be used independently, so that the two additional energy branches need to be used simultaneously and parameters need to be optimized, and the optimal oscillation suppression effect is achieved.

(2) Adding

additional energy branches

1 and 2

Adding subsynchronous oscillation disturbance with a large oscillation amplitude into the system when t is 1s, putting the two additional energy branches into the system when t is 2s, taking the energy dissipation rate of the system when t is 2s as an optimization objective function value, and obtaining control parameters of the two additional energy branches through a BCC parameter optimization method, wherein the control parameters comprise: k_{c1_min}＝0.074、K_{c2_min}9.69. The influence of the additional energy branch control parameters on the system energy dissipation ratio is shown in fig. 11, and the minimum point a of the system energy dissipation ratio_{Energy_min}Has the coordinates of [0.074,9.69, -7.328X 10 ]^-10]. By adopting the control parameter, the suppression effect of the control measure is verified through a dynamic energy model and time domain simulation.

And when t is equal to 1s, subsynchronous oscillation disturbance with larger oscillation amplitude is added into the system, and when t is equal to 2s, two additional energy branches with optimized control parameters are added. As shown in fig. 12, the dynamic energy at the port of the virtual synchronous double-fed fan is accumulated at a speed gradually increasing before the energy branch is added, and after the energy branch is added, the accumulated speed of the dynamic energy of the system is gradually decreasing, and finally the dynamic energy is not changed and the system enters a stable state again. The energy dissipation rate of the virtual synchronous double-fed fan is as shown in fig. 13, before the energy branch is added, the energy dissipation rate of the system is always a positive value, the absolute value is gradually increased, after the energy branch is added, the energy dissipation rate of the system is always a negative value, the absolute value is gradually decreased, the system finally converges to 0, and the system enters a stable state again. The energy dissipation ratios of the system before and after the time t is 2s are respectively 1.98 × 10^-10、-7.33×10^-10Therefore, the system energy dissipation rate is reduced by the input of the additional energy branch circuit, and the system energy dissipation rate is changed from a positive value to a negative value, so that the stability level of the system is improved.

The active power output by the virtual synchronous double-fed fan is shown in fig. 14, the oscillation amplitude of the active power is continuously increased in a time period of 1-2 s, the oscillation amplitude is gradually reduced after the time period of 2s, and the system enters a stable state again. The d-axis voltage instantaneous value on the rotor side is shown in FIG. 15, and the d-axis voltage instantaneous values on the rotor side are stabilized before and after the additional energy branch is put into operationValue of state u_rd0Basically, the system has no change, and the influence of control measures on the steady-state operation characteristic of the system is small by calculating the change amount to be less than 5 percent.

In conclusion, the subsynchronous oscillation cooperative control strategy of the multiple additional energy branches can effectively inhibit the subsynchronous oscillation of the system and improve the stability of the system.

Those skilled in the art will appreciate that all or part of the flow of the method implementing the above embodiments may be implemented by a computer program, which is stored in a computer readable storage medium, to instruct related hardware. The computer readable storage medium is a magnetic disk, an optical disk, a read-only memory or a random access memory, etc.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention.

Claims

1. A virtual synchronous doubly-fed fan subsynchronous oscillation suppression method is characterized by comprising the following steps:

collecting operation data of the virtual synchronous double-fed fan;

based on the operation data, obtaining the energy dissipation rate of the virtual synchronous double-fed fan before the additional energy branch is added and the energy dissipation rate variation after the additional energy branch is added, and further obtaining the total energy dissipation rate of the virtual synchronous double-fed fan;

and establishing a control parameter optimization model by taking the energy dissipation ratio variable quantity after the additional energy branches are added as less than 0 and the total energy dissipation ratio minimum value as a target function constraint condition, determining the control parameters of each additional energy branch, and starting each additional energy branch after the parameters are determined to realize the subsynchronous oscillation suppression of the virtual synchronous double-fed fan.

2. The virtual synchronous doubly-fed wind turbine subsynchronous oscillation suppression method for the virtual synchronous doubly-fed wind turbine as recited in claim 1, wherein the operation data of the virtual synchronous doubly-fed wind turbine comprises: the method comprises the steps of rotor current and voltage, inductance of a rotor and a stator, mutual inductance between the stator and the rotor, a stator voltage amplitude instruction value, deviation amount of subsynchronous angular velocity and synchronous angular velocity, a reference value of a named value of angular velocity, slip angular velocity of a doubly-fed fan, amplitude of disturbance current, total resistance of a transmission line, a direct current voltage steady-state value and active power.

3. The virtual synchronous doubly-fed wind turbine subsynchronous oscillation suppression method of claim 1, wherein the added additional energy branch comprises:

additional energy branch 1: rotor current is introduced into the rotor virtual synchronous control, and after low-pass filtering, the rotor current is subjected to virtual resistance gain K_c1Outputting to a rotor voltage;

4. The virtual synchronous doubly-fed wind turbine subsynchronous oscillation suppression method of claim 2, wherein total energy dissipation ratio a 'of the virtual synchronous doubly-fed wind turbine'_EnergyExpressed as:

a′_Energy＝a_Energy+Δa_Energy；

in the formula, a_EnergyIncreasing the energy dissipation ratio delta a before adding an additional energy branch for the virtual synchronous double-fed fan_EnergyAnd increasing the energy dissipation rate variable quantity after an additional energy branch is added to the virtual synchronous double-fed fan.

5. The virtual synchronous doubly-fed wind turbine subsynchronous oscillation suppression method for the virtual synchronous doubly-fed wind turbine as claimed in claim 1, wherein the energy dissipation ratio of the virtual synchronous doubly-fed wind turbine before adding the additional energy branch is expressed as follows:

wherein the content of the first and second substances,

in the formula i_rd0、i_rq0Is a steady-state value of the current amplitude of the d-axis and the q-axis of the rotor, u_rd0、u_rq0Is a steady state value of d-axis and q-axis voltage amplitudes of the rotor, L_rIs the rotor inductance, L_sIs a stator inductance, L_mIs mutual inductance, U, between stator and rotor_sIs a stator voltage amplitude command value, U_r0A steady state value expressed as a rotor voltage amplitude command value, Δ ω is a deviation amount of the subsynchronous angular velocity from the synchronous angular velocity, ω_bIs a reference value, omega, of a nominal value of angular velocity_slipThe slip angular velocity of the doubly-fed wind turbine is D, the virtual damping coefficient is T_jIs a time constant of the virtual inertia,

6. The virtual synchronous doubly-fed wind turbine subsynchronous oscillation suppression method of claim 5, wherein the energy dissipation ratio variation Δ a of the virtual synchronous doubly-fed wind turbine after the virtual synchronous doubly-fed wind turbine adds the additional energy branch is increased_EnergyExpressed as:

7. The virtual synchronous double-fed fan subsynchronous oscillation suppression method of claim 6, wherein the total number n of categories of the introduced energy dissipation ratio variation is 6; the various types of energy dissipation rate variations are expressed as follows:

in the formula, K_c1For the virtual resistance gain of the additional energy branch 1 as a control parameter of the additional energy branch 1, K_c2The integral coefficient of the additional energy branch 2 is used as a control parameter of the additional energy branch 2.

8. The virtual synchronous doubly-fed wind turbine subsynchronous oscillation suppression method of claim 7, wherein the control parameter optimization model is expressed as:

in the formula of U_d0Is the steady-state value of the DC voltage of the virtual synchronous double-fed fan, U_rmin、U_rmaxThe upper limit and the lower limit of the steady state value of the rotor voltage during the steady state operation of the system, U_dmin、U_dmaxThe upper limit and the lower limit, omega, of the steady-state value of the direct-current voltage during the steady-state operation of the system_disFor sub-synchronous disturbance of angular velocity, K_min、K_maxFor controlling a parameter K_c1And K_c2Upper and lower limits of the value of (1).

9. The virtual synchronous double-fed wind turbine subsynchronous oscillation suppression method of claim 8, further comprising the step of obtaining the optimal control parameters of the additional energy branches based on the control parameter optimization model and function optimization of a bacterial population chemotaxis algorithm.

10. The utility model provides a virtual synchronous doubly-fed fan subsynchronous oscillation suppression system which characterized in that includes:

the total energy dissipation ratio calculation module is used for obtaining the energy dissipation ratio of the virtual synchronous double-fed fan before the additional energy branch is added and the energy dissipation ratio variable quantity after the additional energy branch is added based on the operation data, and further obtaining the total energy dissipation ratio of the virtual synchronous double-fed fan;