CN106655205A - Wind power plant medium voltage bus voltage closed-loop control method based on reactive power adjustment difference technology - Google Patents

Abstract

The reactive power capacity of a doubly-fed wind turbine set is represented by using the form of reactive current for aiming at the distributed wind power characteristics, and the reactive current limit of the doubly-fed wind turbine set is calculated according to the restrictions of stator and rotor winding heat, the current transformer capacity and DC link voltage withstanding so as to be directly used for the design of current amplitude limiting of current transformer control. A turbine terminal voltage closed-loop control strategy having the droop characteristic is put forward based on current transformer vector control so as to have the the advantages that spontaneous reactive power dynamic compensation of the distributed wind turbine sets without communication between current transformer modules and reasonable distribution of turbine network side reactive current can be maintained. Appropriate adjustment difference is set for the whole voltage control of the wind power plant so as to avoid field level reactive loop current. The method plays an important role in participation of the new energy grid-connected wind turbine set in the power system voltage adjustment function on the basis of adopting the control strategy so that absorption and utilization of the new energy and the stability of the power system can be facilitated.

Description

Busbar voltage closed loop control method is pressed in wind energy turbine set based on reactive difference adjustment technology

Technical field

The present invention relates to wind power generation field, and in particular to realize being adopted during voltage regulation function in wind energy turbine set based on idle tune The middle pressure busbar voltage closed loop control method of difference technology.

Background technology

During " 12 ", national policy starts to encourage development distributing Wind Power Project, by number typhoon group of motors or tens of Miniature wind electric field within megawatt is directly accessed near distribution load centre, realizes wind power output on-site elimination.Under the pattern Wind power integration point is normally at remote districts, and the pressure drop of power distribution network tail end line and loss are larger, and idle deficiency, Wind turbines are usual Do not possess the Inertia Characteristics of synchronous generator to participate in the primary frequency modulation pressure regulation ability of power system, if Wind turbines provide spirit yet Reactive-load compensation and voltage support living is acted on, and the idle burden that can mitigate power distribution network lifts economy, is also beneficial to wind turbine The stable operation of group.

Current the control of reactive power compensating is studied based on Large Scale Wind Farm Integration application, generally using automatism voltage control (AVC) system System distributing application, is related to the idle coordination of dispatching of power netwoks, wind energy turbine set and Wind turbines unit control hierarchical, eventually through regulation Realize that grid entry point determines power factor controlling or reactive power scheduling refers in wind energy turbine set per the reactive power of typhoon group of motors output Order tracking.It is normal with control time by communication delay due to there is idle command communication between Wind turbines and field level centralized control system About, Wind turbines are at least second level to numeral system to the response time of the idle instruction of dispatching of power netwoks.And distributing Wind turbines and load Electrical distance it is near, be voltage constant when maintaining load variations, the dynamic passive compensation of ms levels need to be realized.It can be seen that, will be above-mentioned The powerless control system of collection control form is applied to small-sized distributing wind energy turbine set, in voltage responsive speed, economy and flexibility etc. Aspect has been short of.

To realize distributing double-fed fan motor unit flexibly and quick reactive-load compensation effect, in the form of reactive current come Reactive power capability is characterized, the reactive power energy of double-fed fan motor unit is obtained according to the real-time watt current of Wind turbines and rotary speed information Power, can be directly used in the amplitude limit design of current transformer control.On specific powerless control method, the generator terminal with droop characteristic is adopted Voltage close loop control strategy, contrasts with the method for pressing machine net side reactive power capability pro rate, and two methods are capable of achieving double-fed wind Reasonable distribution that group of motors machine net side is idle and auto-reactive compensation are controlled, but droop characteristic does not require leading between converter module News, it is not necessary to consider that communication delay affects on reactive response speed, stator side and net side current transformer are capable of achieving Quick reactive-load compensation, It is more suitable for current engineering use demand.

The content of the invention

To solve the deficiency in prior art, it is an object of the invention to provide when realizing voltage regulation function in a kind of wind energy turbine set Using the middle pressure busbar voltage closed loop control method based on reactive difference adjustment technology so that realizing that Wind turbines realize pressure regulation work( Faster, precision is higher for speed during energy, it is ensured that the validity of follow-up idle output.

The present invention employs the following technical solutions to realize：

1. busbar voltage closed loop control method is pressed in a kind of wind energy turbine set based on reactive difference adjustment technology, it is characterised in that：

(1) limit to calculate according to Stator and Rotor Windings heating, the condition that Converter Capacity and DC link are pressure and obtain double The feedback Wind turbines reactive current limit, is directly used in the current limit of current transformer control；Sub- rated maximum current is set as I_{s max}, I_sFor the current effective value under three phase coordinates, i_sd、i_sqStator current d axles and q axle components are represented, is had：

(2) the maximum current virtual value of rotor windings longtime running permission is set as I_{r max}, by rotor-side current actual value folding Calculate to stator side, and with stator current d axles and q axle component i_sd、i_sqRepresent, obtain：

In formula, k_srIt is that rotor-side current actual value is converted the winding conversion factor removed to stator side, k_srEqual to motor The ratio of rotor openings voltage and stator voltage, u_sdRefer to stator voltage d axle component, X_m、X_sExcitatory reactance and stator are represented respectively Reactance；

(3) rotor voltage sinusoidal phase voltage amplitude is less thanBy rotor voltage stator current and voltmeter Show：

Wherein, U_dcRepresent the DC voltage on electric capacity, X between pusher side module and net side module_m、X_s、X_rRepresent respectively excitatory Reactance and stator, rotor reactance；

(4) reactive power capability of net side current transformer is limited when watt current determines by current transformer maximum running current, is obtained In real time active and revolutional slip relation is the reactive power capability of net side current transformer with stator：

Wherein, i_sdRepresent stator watt current, i_gqRepresent the q axle components of current on line side, I_gmaxFor net side rated current Maximum；

In practice Wind turbines are run by the torque of master control setting with speed curves, stator watt current i_sdWith revolutional slip s Not completely self-contained two variables；

(5) on the basis of current transformer set end voltage PI controls, voltage droop characteristic is introduced, realizes pusher side and net side unsteady flow Device reactive current compensation automatically respectively, if K_iqFor sagging coefficient, represent that reactive current increases from zero to set end voltage during rated value Relative change, be mathematically represented as：

When reactive current changes delta i_qWhen, set end voltage is by changes delta V.

In the step (5), a virtual reactance is introduced equivalent in voltage output terminal with sagging Characteristics Control, changed The condition of the direct paired runnings of two voltage sources；If distributing reactive load by the reactive power capability of each voltage source, sagging coefficient takes Value should be inversely proportional to real-time exportable maximum reactive current：i_{qmax_1}Ki_{q_1}=i_{qmax_2}K_{iq_2}, wherein, i_{qmax_1}、i_{qmax_2}Correspondence Different sagging COEFFICIENT Ks_{iq_1}、K_{iq_2}Idle maximum.

The present invention has the beneficial effect that：It is pressure etc. in analysis Stator and Rotor Windings heating, Converter Capacity and DC link Calculate on the basis of the restriction of condition and obtain double-fed fan motor unit reactive current limit numerical procedure, it is ensured that subsequently idle output has Effect property；The idle independent control strategy of machine net side based on droop characteristic eliminates the control of the distribution based on machine net side reactive power capability The communication of machine net side and its time delay that brings needed for strategy so that when realizing that Wind turbines realize voltage regulation function speed faster, Precision is higher；

There is provided a kind of wind field voltage control configuration the appropriate control strategy for adjusting difference to avoid field level reactive circular power flow, level wind-powered electricity generation on the scene Unit realizes synchronism and same tone.

Description of the drawings

Fig. 1 is double-fed fan motor unit structure of the present invention；

Fig. 2 is the relation curve of double-fed fan motor unit watt current of the present invention and revolutional slip；

Fig. 3 (a) is 1.5MW double-fed wind turbines side reactive current scope of the present invention；

Fig. 3 (b) is 1.5MW double-fed fan motor units net side current transformer reactive current scope of the present invention；

Fig. 3 (c) is the total idle limit of 1.5MW double-fed fan motor units double-fed fan motor unit of the present invention；

Fig. 4 is the present invention control of the double-fed set end voltage with droop characteristic；

Fig. 5 is voltage source of the present invention parallel connection schematic diagram；

Fig. 6 is droop characteristic schematic diagram；

Fig. 7 is the simulation model topology signal that double-fed fan motor unit of the present invention accesses power distribution network；

Fig. 8 is the low-pressure side voltage oscillogram of fan outlet transformer of the present invention；

Fig. 9 (a) is stator current waveforms figure of the present invention；

Fig. 9 (b) is network side current waveform figure of the present invention；

Figure 10 (a) is stator reactive power oscillogram of the present invention；

Figure 10 (b) is net side reactive power oscillogram of the present invention；

Figure 10 (c) is the stator active power oscillogram of the present invention；

Figure 10 (d) is the net side active power oscillogram of the present invention.

Specific embodiment

Technological means, creation characteristic, reached purpose and the effect realized for the present invention is easy to understand, with reference to It is specifically illustrating, the present invention is expanded on further.

The present invention characterizes double-fed fan motor unit ability in the form of reactive current, according to Stator and Rotor Windings heating, unsteady flow Device capacity and DC link is pressure etc. that condition limits to calculate obtains the double-fed fan motor unit reactive current limit, can be directly used for becoming The current limit design of stream device control；On the basis of current transformer vector controlled, the set end voltage closed loop with droop characteristic is proposed Control strategy, with without the need for the communication between converter module, realizing the spontaneous reactive-load dynamic compensation of distributing Wind turbines and protect Hold the advantage of machine net side reactive current reasonable distribution.

It is described that according to Stator and Rotor Windings heating, Converter Capacity and DC link be pressure etc., condition limits to calculate obtains The double-fed fan motor unit reactive current limit, the reactive current limit is subject to following several restrictions, set sub- rated maximum current as I_smax, the quadratic sum of stator current d axles and q axle components has virtual value square less than or equal to rated maximum current；Similar to fixed The restriction of electron current, if the maximum current virtual value that rotor windings longtime running is allowed is I_rmax, by rotor-side current actual value Convert to stator side, and use stator current I_sd、I_sqRepresent, quadratic sum of its quadratic sum less than rotor maximum virtual value；While pole Limit needs to consider that current transformer output voltage under SVPWM modulation systems does not occur ovennodulation.

Ignore active loss, the reactive power capability of net side current transformer is mainly transported when watt current determines by current transformer maximum Row current limit, obtains the reactive power capability and real-time active and revolutional slip the relation of stator, si of net side current transformer_sdWith i_gqIt is flat Just and less than or equal to net side reactive current I_gmaxVirtual value square.

Set end voltage Closed-loop Control Strategy with droop characteristic, when load change causes system voltage to change, sagging coefficient Little unit undertakes larger idle increment, arranges sagging coefficient and is inversely proportional to unit reactive capability, then droop characteristic can ensure Power reasonable distribution between each generator during load change.

A virtual reactance is introduced equivalent in voltage output terminal with sagging Characteristics Control, two voltage sources is changed direct The condition of paired running.If distributing reactive load by the reactive power capability of each voltage source, sagging coefficient value should can be defeated with real time Go out maximum reactive current to be inversely proportional to：i_{qmax_1}K_{iq_1}=i_{qmax_2}K_{iq_2}。

Referring to Fig. 1-Fig. 2, according to Stator and Rotor Windings heating, Converter Capacity and DC link be pressure etc., condition limits meter Calculate and obtain double-fed fan motor unit reactive current limit numerical procedure；It is an object of the invention to provide a kind of machine with droop characteristic Net side is idle independent control strategy.

Appropriate tune difference is set in the control of wind energy turbine set whole audience voltage and avoids field level reactive circular power flow, by wind power station control system It is middle to add appropriate tune poor, can effectively avoid wind field multiple stage current transformer from reactive circular power flow directly occur.One kind is based on reactive difference adjustment The middle pressure busbar voltage closed loop control method of technology, its method is as follows：

(1) limit to calculate according to Stator and Rotor Windings heating, the condition that Converter Capacity and DC link are pressure and obtain double The feedback Wind turbines reactive current limit, referring to Fig. 3 (a)-(c), its 1.5MW double-fed fan motor unit reactive current limit；Setting Rated maximum current is I_smax, have：

(2) the maximum current virtual value of rotor windings longtime running permission is set as I_rmax, by rotor-side current actual value folding Calculate to stator side, and use stator current i_sd、i_sqRepresent, obtain：

In formula, k_srIt is that rotor-side current actual value is converted the winding conversion factor removed to stator side, k_srEqual to motor The ratio of rotor openings voltage and stator voltage.

(3) to make current transformer output voltage under SVPWM modulation systems that ovennodulation, rotor voltage sinusoidal phase voltage not occur Amplitude is less thanRotor voltage stator current and voltage are represented：

(4) active loss is ignored, the reactive power capability of net side current transformer is mainly maximum by current transformer when watt current determines Running current is limited, and the reactive power capability and real-time active and revolutional slip the relation of stator for obtaining net side current transformer is：

In practice Wind turbines are run by the torque of master control setting with speed curves, stator watt current i_sdWith revolutional slip s Not completely self-contained two variables.

(5) standalone module is typically adopted in view of existing double-feed current transformer, may not between rotor-side and net side current transformer Possess the condition for communicating with one another, then do not apply to by the method for machine net side reactive power capability pro rate.For this purpose, sending out with reference to conventional synchronization Motor excitation adjusts difference design, the present invention to introduce voltage droop characteristic on the basis of current transformer set end voltage PI controls, realize machine The compensation automatically respectively of side and net side current transformer reactive current, control block diagram as shown in figure 4, wherein, K_iqFor sagging coefficient, indicate without Work(electric current increases from zero to the relative change of set end voltage during rated value, is mathematically represented as：

Below with the voltage-regulation principle of oolemma droop characteristic for 2 voltage sources example in parallel.In Fig. 5, V_k∠δ_kFor The output voltage of k power supply, k=1,2；Z_kFor the grid-connected impedance of k-th power supply, including voltage source equivalent output impedance and circuit Impedance；V ∠ 0 are point voltage in parallel,For the output current of k-th power supply,For load current.

Voltage source k output active power and reactive power be：

When the grid-connected impedance of voltage source is mainly perception, i.e. X_k>>R_k,, can be by R_kIgnore, and power angle δ_kVery little, approximate To sin δ_k≈δ_k, cos δ_k≈ 1, then formula (6) can be with abbreviation：

Reactive current is with the relation of voltage：

It can be seen that the reactive power of voltage source output is mainly determined by the pressure reduction on inductance, it means that change the defeated of voltage source Go out the i.e. achievable regulation to reactive power of voltage magnitude.

When load change causes system voltage to change, the little unit of sagging coefficient undertakes larger idle increment, in such as Fig. 6 There is Δ i_q2＞ Δ i_q1, sagging coefficient is set and is inversely proportional to unit reactive capability, then droop characteristic can proof load change when each Power reasonable distribution between motor.

The sagging Characteristics Control of band shown in Fig. 5 introduces a virtual reactance equivalent in voltage output terminal, changes two The condition of the direct paired running of voltage source.If distributing reactive load by the reactive power capability of each voltage source, sagging coefficient value should It is inversely proportional to real-time exportable maximum reactive current：

i_{qmax_1}K_{iq_1}=i_{qmax_2}K_{iq_2} (9)

It should be noted that droop control can cause voltage actual magnitude to produce deviation with setting value, deviation is steady Unit reactive current i under the conditions of state_qIt is multiplied by K_iq.During practical application, set end voltage reference value can be set and omited than load voltage value It is high.

The multi-machine parallel connection of this enforcement row accesses the model such as Fig. 7 run in power distribution network, " double-fed fan motor unit " Jing long transmission lines In accessing weak electrical network, load is directly hung with circuit.Nothing of the net side current transformer and stator side of double-fed fan motor unit to electrical network Work(compensation is considered two independent reactive sources, is simulated by the direct parallel connection of 2 current transformers.

For simplify control, ignore wind speed change in idle controlling cycle, then the watt current of double-fed fan motor unit and idle Ability keeps constant.Stator maximum current is taken as 2000A, and watt current is set to 1000A；Net side current transformer maximum current is taken as 500A, the watt current of net side current transformer is set to 200A by maximum slip operating mode.In view of the specified of actual net side current transformer Capacity is about taken as the 1/3 of stator capacity, therefore idle sagging coefficient is direct in stator side and the control of net side current transformer voltage close loop By 1:3 give, and K is taken as respectively_{iq_s}=-0.01, K_{iq_g}=-0.03.

Emulation initial setting up current transformer does not provide reactive-load compensation, 0.35s input set end voltage closed-loop controls, wind during 0.65s The high-pressure side load incision that group of motors outlet becomes.As a result as shown in Fig. 9 (a) to Figure 10 (d), mark 1 is represented and adopts under band in figure The machine net side independent control of vertical characteristic, mark 2 to be represented and coordinate control using the machine net side for pressing reactive power capability pro rate.

Simulation result shows that after input voltage close loop control, current transformer output reactive current increases sharply, and makes set end voltage Rapid lifting, when load variations cause voltage pulsation in electrical network, two kinds of distribution methods can play auto-reactive compensation, but machine net In proportion net side communication delay causes reactive response slower in the method for coordinated allocation for side, and with droop characteristic without distribution of work side Pusher side and the idle control of net side in method can be rapidly reached stable state.

Table 1 lists the partial data for coordinating control by droop control and in proportion.Under identical voltage reference value, Stable state is entered by sagging Characteristics Control Wind turbines during 0.6s, and leaves certain Reactive Power Margin, but it is inclined due to there is steady state voltage Difference, reality output reactive current is controlled less than reactive power capability pro rate is pressed；But control by reactive power capability pro rate off line Side converter is slower due to time-lag action reactive response, not yet up to stable state.During 0.8s, load or burden without work is bigger than during 0.6s in electrical network, Now Wind turbines are compensated by the idle limit under two methods.

Table 1 is pressed droop control and is contrasted by the operation of reactive power capability eurythmy

To realize distributing double-fed fan motor unit flexibly and quick reactive-load compensation effect, in the form of reactive current come Reactive power capability is characterized, the reactive power energy of double-fed fan motor unit is obtained according to the real-time watt current of Wind turbines and rotary speed information Power, can be directly used in the amplitude limit design of current transformer control.On specific powerless control method, the generator terminal with droop characteristic is adopted Voltage close loop control strategy, contrasts with the method for pressing machine net side reactive power capability pro rate, and two methods are capable of achieving double-fed wind Reasonable distribution that group of motors machine net side is idle and auto-reactive compensation are controlled, but droop characteristic does not require leading between converter module News, it is not necessary to consider that communication delay affects on reactive response speed, stator side and net side current transformer are capable of achieving Quick reactive-load compensation, It is more suitable for current engineering use demand.

The general principle and principal character and advantages of the present invention of the present invention has been shown and described above.The technology of the industry Personnel it should be appreciated that the present invention is not limited by method used above, simply say by above-mentioned using method and specification description The principle of the bright present invention, under the premise without departing from the spirit and scope of the present invention, the present invention also has various changes and modifications, These changes and improvements are both fallen within scope of the claimed invention.The claimed scope of the invention is by appended claim Book and its equivalent thereof.

Claims (2)

1. busbar voltage closed loop control method is pressed in a kind of wind energy turbine set based on reactive difference adjustment technology, it is characterised in that：

(1) limit to calculate according to Stator and Rotor Windings heating, the condition that Converter Capacity and DC link are pressure and obtain double-fed wind The group of motors reactive current limit, is directly used in the current limit of current transformer control；Sub- rated maximum current is set as I_smax, I_sFor Current effective value under three phase coordinates, i_sd、i_sqStator current d axles and q axle components are represented, is had：

$i_{sd}^2+i_{sq}^2={\left(\sqrt{2}{I}_s\right)}^2\≤{\left(\sqrt{2}{I}_{smax}\right)}^2---\left(1\right)$

(2) the maximum current virtual value of rotor windings longtime running permission is set as I_rmax, rotor-side current actual value is converted to calmly Sub- side, and with stator current d axles and q axle component i_sd、i_sqRepresent, obtain：

${\left(i_{sd}\right)}^2+{(\frac{u_{sd}}{X_s}+i_{sq})}^2\≤{\left(\frac{\sqrt{2}{X}_m}{k_{sr}{X}_s}{I}_{rmax}\right)}^2---\left(2\right)$

In formula, k_srIt is that rotor-side current actual value is converted the winding conversion factor removed to stator side, k_srEqual to rotor The ratio of opening voltage and stator voltage, u_sdRefer to stator voltage d axle component, X_m、X_sExcitatory reactance and stator reactance are represented respectively；

(3) rotor voltage sinusoidal phase voltage amplitude is less thanRotor voltage stator current and voltage are represented：

${\left(i_{sd}\right)}^2+{(\frac{X_r{u}_{sd}}{{X_m}^2-X_r{X}_s}-i_{sq})}^2\≤{\left(\frac{X_m}{{X_m}^2-X_r{X}_s}\frac{k_{sr}}{s}\frac{U_{dc}}{\sqrt{3}}\right)}^2---\left(3\right)$

Wherein, U_dcRepresent the DC voltage on electric capacity, X between pusher side module and net side module_m、X_s、X_rExcitatory reactance is represented respectively With stator, rotor reactance；

(4) reactive power capability of net side current transformer is limited when watt current determines by current transformer maximum running current, obtains net side In real time active and revolutional slip relation is the reactive power capability of current transformer with stator：

${\left({\mathrm{si}}_{sd}\right)}^2+i_{gq}^2\≤{\left(\sqrt{2}{I}_{gmax}\right)}^2---\left(4\right)$

Wherein, i_sdRepresent stator watt current, i_gqRepresent the q axle components of current on line side, I_gmaxFor the maximum of net side rated current Value；

In practice Wind turbines are run by the torque of master control setting with speed curves, stator watt current i_sdWith revolutional slip s not Completely self-contained two variables；

(5) current transformer set end voltage PI control on the basis of, introduce voltage droop characteristic, realize pusher side and net side current transformer without Work(electric current compensation automatically respectively, if K_iqFor sagging coefficient, represent that reactive current increases from zero to the phase of set end voltage during rated value To change, it is mathematically represented as：

$K_{iq}=-\frac{\mathrm{\Δ}V}{{\mathrm{\Δi}}_q}---\left(5\right)$

When reactive current changes delta i_qWhen, set end voltage is by changes delta V.

2. required to press busbar voltage closed loop control method in described wind energy turbine set according to right 1, it is characterised in that：The step (5) in, a virtual reactance is introduced equivalent in voltage output terminal with sagging Characteristics Control, changes two voltage sources directly simultaneously The condition of row operation；If distributing reactive load by the reactive power capability of each voltage source, sagging coefficient value should be exportable with real-time Maximum reactive current is inversely proportional to：i_{qmax_1}K_{iq_1}=i_{qmax_2}K_{iq_2}, wherein, i_{qmax_1}、i_{qmax_2}The different sagging coefficient of correspondence K_{iq_1}、K_{iq_2}Idle maximum.