CN103972921B - A kind of permanent-magnet synchronous wind energy turbine set low voltage crossing control method for coordinating based on power-balance - Google Patents

Abstract

The invention discloses a kind of permanent-magnet synchronous wind energy turbine set low voltage crossing control method for coordinating based on power-balance, belong to technical field of wind power generation.The present invention is according to the wind farm grid-connected point voltage of detection, and utilize the active reactive distribution capability of total power converter in permanent-magnet synchronous Wind turbine, each permanent-magnet synchronous Wind turbine controlled in low voltage crossing process in wind energy turbine set sends reactive power to electrical network.The present invention makes full use of the idle conveying capacity of permanent-magnet synchronous Wind turbine full power convertor; can meet without the need to installing SVC additional the requirement that dynamic reactive electric current is provided to electrical network during wind energy turbine set low voltage crossing; stablizing of current transformer direct voltage and stablizing of generator speed can be realized without the need to crow bar protective circuit simultaneously, the basis reducing unit cost adds the reliability of wind power system wind energy turbine set low voltage crossing.

Description

A kind of permanent-magnet synchronous wind energy turbine set low voltage crossing control method for coordinating based on power-balance

Technical field

The invention belongs to technical field of wind power generation, the present invention relates to a kind of permanent-magnet synchronous wind energy turbine set low voltage crossing control method for coordinating based on power-balance more precisely.

Background technology

Large-scale wind power field concentrates access to bring many new problems to electric power system, wherein the focus paid close attention to the most by Chinese scholars and manufacturer of reactive voltage problem.Load variations, electric power system fault all can cause the fluctuation of line voltage, and this just requires that the wind-driven generator of grid-connected access has certain low voltage ride-through capability.According in GB " wind energy turbine set access power system technology regulation " (GB/T19963-2011) to reactive voltage aspect latest requirement: when (1) wind farm grid-connected point voltage drops to 20% nominal voltage, the Wind turbines in wind energy turbine set should ensure that off-grid does not run 625ms continuously; (2) total installation of generating capacity is at million kilowatt scale and above wind farm group, when electric power system generation three phase short circuit fault causes Voltage Drop, each wind energy turbine set should have corresponding reactive power support ability in low voltage crossing process, and wind energy turbine set injects the dynamic reactive electric current I of electric power system _t>=1.5 × (0.9-V _pu) I _n(0.2≤V _pu≤ 0.9), wherein: V _pufor wind farm grid-connected point voltage perunit value; I _nfor wind energy turbine set rated current.

Permanent magnet synchronous wind generator (PMSG) due to adopt full power convertor and eliminate speed-changing gear box by generator and electrical network completely isolated, compare traditional wind system reliability greatly to improve, in recent years along with its occupation rate of market of development of Large Copacity current transformer significantly promotes.The control of existing PMSG wind energy turbine set low voltage crossing (LVRT) is mainly divided into two aspects: one is utilize crowbar circuit attrition voltage to fall the energy difference at indirect AC convertor two ends in period PMSG unit to maintain DC-side Voltage Stabilization; Two be at wind energy turbine set feeder line and site install additional reactive power compensation (SVC) device solve the wind farm grid-connected reactive voltage stable problem caused.Owing to adding hardware device, these two kinds of methods bring a lot of hidden danger in actual wind energy turbine set puts into operation: (1) makes complex system, and the hardware cost of increase is high, and model performance disunity; (2) immature to the timing input algorithm of crowbar circuit and SVC equipment, switching regulating time is long.These problems all can cause whole wind generator system reliability to reduce, thus likely cause system low-voltage to pass through unsuccessfully.

In recent years China with all strength development large-scale wind power concentrated grid-connected, along with installed capacity is constantly risen, existing PMSG wind energy turbine set LVRT method will can not meet GB gradually to system economy and the increasingly strict requirement of reliability.Therefore, be badly in need of proposing a kind of permanent magnet direct-drive wind energy turbine set low voltage crossing control method for coordinating based on power-balance.

Summary of the invention

The object of the invention is: in order to overcome the deficiencies in the prior art, providing a kind of permanent-magnet synchronous wind energy turbine set low voltage crossing control method for coordinating based on power-balance.The method is according to the wind farm grid-connected point voltage of detection, and utilize the active reactive distribution capability of total power converter in PMSG unit, each PMSG unit controlled in low voltage crossing process in wind energy turbine set sends reactive power to electrical network.

Specifically, the present invention adopts following technical scheme to realize, and comprises the following steps:

1) the wind farm grid-connected point voltage value V of Real-Time Monitoring _out, calculate wind farm grid-connected point voltage perunit value wherein V _out-reffor and site reference voltage base value;

2) as 0.9≤V _puwhen≤1.1, adopt normality control strategy to make each permanent-magnet synchronous Wind turbine in wind energy turbine set be operated in unit power factor pattern, return step 1) carry out next round control, otherwise enter step 3);

3) V is worked as _pu<0.2 or V _puduring >1.1, cut off wind farm grid-connected outlet, make each permanent-magnet synchronous Wind turbine off-grid in wind energy turbine set, method ends; Otherwise enter step 4);

4) power coordination control strategy is adopted to each permanent-magnet synchronous Wind turbine in wind energy turbine set, then enter step 5);

5) monitor wind farm grid-connected point voltage in step 1) institute monitor V _puvalue on the T that holds time, when T exceedes national standard " wind energy turbine set access power system technology regulation " corresponding requirements, cut off wind farm grid-connected outlet, make each permanent-magnet synchronous Wind turbine off-grid in wind energy turbine set, method ends; Otherwise enter step 6);

6) carry out meritorious recovery to control, return step 1) carry out next round control.

Technique scheme is further characterized in that, described step 2) in, normality control strategy refers to and adopts maximal power tracing to control to each permanent-magnet synchronous Wind turbine in wind energy turbine set.

Technique scheme is further characterized in that, described step 4) in, power coordination control strategy comprises current transformer power distribution strategies and variable pitch and to gain merit suppression strategy.

Technique scheme is further characterized in that, described step 6) in, meritorious recover to control to refer to the dynamic reactive given value of current value i net side converter of the permanent-magnet synchronous Wind turbine of i-th in wind energy turbine set being calculated to each permanent-magnet synchronous Wind turbine according to following formula _q-refwith active current set-point i _d-ref:

i _q-ref＝0

$\frac{P_i}{P_N}\&le;i_{d-ref}\&le;K_1$

Wherein, subscript i is the sequence number of each permanent-magnet synchronous Wind turbine, P _ifor the active power that front i-th the permanent-magnet synchronous Wind turbine of fault exports to electrical network, P _nbe the rated power of i-th permanent-magnet synchronous Wind turbine, K ₁be the power limit of the net side converter of i-th permanent-magnet synchronous Wind turbine, 1≤K ₁≤ 1.2.

Technique scheme is further characterized in that, described current transformer power distribution strategies comprises pusher side current transformer meritorious consumption control strategy and net side converter reactive power support control strategy, and concrete control strategy is as follows:

I, pusher side current transformer are meritorious consumes control strategy:

I-1) in control procedure, i-th permanent-magnet synchronous Wind turbine set end voltage u in wind energy turbine set is calculated _i, calculate the set end voltage perunit value of i-th permanent-magnet synchronous Wind turbine u _nit is the rated voltage of i-th permanent-magnet synchronous Wind turbine;

I-2) the power given value of the pusher side current transformer of i-th permanent-magnet synchronous Wind turbine is changed according to following formula:

$p_{i-ref}=K_2\&CenterDot;u_{i-pu}\&CenterDot;\frac{P_i}{P_N}$

q _i-ref＝0

Wherein, p _i-ref, q _i-refbe respectively meritorious, the idle set-point of i-th permanent-magnet synchronous unit pusher side current transformer, K ₂for power control ratio, 0≤K ₂≤ 1;

II, net side converter reactive power support control strategy: for the dynamic reactive electric current making wind farm grid-connected point inject electrical network during low voltage crossing reaches the GB requirement grid-connected to Large Scale Wind Farm Integration, during low voltage crossing, the net side converter of the permanent-magnet synchronous Wind turbine of i-th in wind energy turbine set is calculated to the dynamic reactive given value of current value i of each permanent-magnet synchronous Wind turbine according to following formula _q-refwith active current set-point i _d-ref:

i _q-ref≥1.5×(0.9-u _i-pu)i _N

$i_{d-ref}\&le;\sqrt{i_N^2-i_{q-ref}^2}$

Wherein, i _nfor the load current value of separate unit permanent-magnet synchronous Wind turbine.

Technique scheme is further characterized in that, described variable pitch suppression strategy of gaining merit is: utilize PI controller according to the propeller pitch angle set-point θ of bias adjustment i-th permanent-magnet synchronous Wind turbine wind wheel blade of generator speed to i-th permanent-magnet synchronous Wind turbine _i-ref, make wind wheel be transported to the active-power P of pusher side current transformer _i-wtwith the power given p of pusher side current transformer _i-refequal, thus suppress to gain merit due to pusher side current transformer to consume the permanent-magnet synchronous Wind turbine fluctuation of speed that causes of control strategy, impact to reduce the DC tache voltage caused due to line voltage rapid drawdown.

Technique scheme is further characterized in that, described i-th permanent-magnet synchronous Wind turbine set end voltage u _ibe calculated as follows:

$u_i=V_{out}+\frac{P_i{R}_i+Q_i{X}_i}{V_{out}}$

Wherein, R _ibe i-th grid-connected equivalent impedance Z of permanent-magnet synchronous Wind turbine _iactive component, X _ibe i-th grid-connected equivalent impedance Z of permanent-magnet synchronous Wind turbine _ireaction component, Z _i=R _i+ jX _i; P _i, Q _ibe respectively the power S that front i-th the permanent-magnet synchronous Wind turbine of fault exports to electrical network _iactive power and reactance capacity, S _i=P _i+ jQ _i.

Beneficial effect of the present invention is as follows: the present invention makes full use of the idle conveying capacity of PMSG unit full power convertor; can meet without the need to installing SVC additional the requirement that dynamic reactive electric current is provided to electrical network during LVRT; stablizing of current transformer direct voltage and stablizing of generator speed can be realized without the need to crow bar protective circuit simultaneously, the basis reducing unit cost adds the reliability of wind power system LVRT.

Accompanying drawing explanation

Fig. 1 is extensive permanent magnet synchronous wind generator access electrical network schematic diagram.

Fig. 2 is the schematic flow sheet of the inventive method.

To be the inventive method to gain merit the simulation comparison oscillogram of power output with utilizing traditional crowbar circuit unit when realizing low voltage crossing Fig. 3.

Fig. 4 is the inventive method and the simulation comparison oscillogram utilizing the idle power output of traditional crowbar circuit unit when realizing low voltage crossing.

Fig. 5 is the inventive method and the simulation comparison oscillogram utilizing traditional crowbar circuit unit generating unit speed when realizing low voltage crossing.

Fig. 6 is the inventive method and the simulation comparison oscillogram utilizing traditional crowbar circuit unit propeller pitch angle when realizing low voltage crossing.

Fig. 7 is the inventive method and the simulation comparison oscillogram utilizing traditional crowbar circuit unit power coefficient when realizing low voltage crossing.

Fig. 8 is the inventive method and the simulation comparison oscillogram utilizing traditional crowbar circuit unit current transformer DC voltage when realizing low voltage crossing.

Embodiment

With reference to the accompanying drawings and in conjunction with example, the present invention is described in further detail.

The wind energy turbine set structure that the inventive method is used as shown in Figure 1.Wind energy turbine set is made up of numerous PMSG, is connected to external electrical network by main transformer.And the flow process of the inventive method is as shown in Figure 2, specifically comprise the following steps:

Step 1), the wind farm grid-connected point voltage value V of Real-Time Monitoring _out, calculate wind farm grid-connected point voltage perunit value wherein V _out-reffor and site reference voltage base value.

Step 2), as 0.9≤V _puwhen≤1.1, adopt normality control strategy to make each permanent-magnet synchronous Wind turbine in wind energy turbine set be operated in unit power factor pattern, return step 1) carry out next round control, otherwise enter step 3).Normality control strategy refers to and adopts maximal power tracing (MPPT) to control to each permanent-magnet synchronous Wind turbine in wind energy turbine set, and this control strategy has ripe algorithm and engineering uses software, therefore does not describe at this.

Step 3), work as V _pu<0.2 or V _puduring >1.1, cut off wind farm grid-connected outlet, make each permanent-magnet synchronous Wind turbine off-grid in wind energy turbine set, method ends; Otherwise enter step 4).

Step 4), power coordination control strategy is adopted to each permanent-magnet synchronous Wind turbine in wind energy turbine set, then enters step 5).

Step 5), monitor wind farm grid-connected point voltage in step 1) institute monitor V _puvalue on the T that holds time, when T exceedes national standard " wind energy turbine set access power system technology regulation " corresponding requirements, cut off wind farm grid-connected outlet, make each permanent-magnet synchronous Wind turbine off-grid in wind energy turbine set, method ends; Otherwise enter step 6);

Step 6), carry out meritorious recovery and control, return step 1) carry out next round control.Meritorious recover to control to refer to the dynamic reactive given value of current value i net side converter of the permanent-magnet synchronous Wind turbine of i-th in wind energy turbine set being calculated to each permanent-magnet synchronous Wind turbine according to following formula _q-refwith active current set-point i _d-ref:

i _q-ref＝0

$\frac{P_i}{P_N}\&le;i_{d-ref}\&le;K_1$

Wherein, subscript i is the sequence number of each permanent-magnet synchronous Wind turbine, P _ifor the active power that front i-th the permanent-magnet synchronous Wind turbine of fault exports to electrical network, P _nbe the rated power of i-th permanent-magnet synchronous Wind turbine, K ₁be the power limit of the net side converter of i-th permanent-magnet synchronous Wind turbine, generally have 1≤K ₁≤ 1.2.

Step 4) in power coordination control strategy comprise current transformer power distribution strategies and variable pitch and to gain merit suppression strategy.Wherein, current transformer power distribution strategies comprises pusher side current transformer meritorious consumption control strategy and net side converter reactive power support control strategy, and concrete control strategy is as follows:

I, pusher side current transformer are meritorious consumes control strategy:

I-1) in control procedure, i-th permanent-magnet synchronous Wind turbine set end voltage u in wind energy turbine set is calculated _i, calculate the set end voltage perunit value of i-th permanent-magnet synchronous Wind turbine u _nit is the rated voltage of i-th permanent-magnet synchronous Wind turbine.

Described i-th permanent-magnet synchronous Wind turbine set end voltage u _ibe calculated as follows:

$u_i=V_{out}+\frac{P_i{R}_i+Q_i{X}_i}{V_{out}}$

Wherein, R _ibe i-th grid-connected equivalent impedance Z of permanent-magnet synchronous Wind turbine _iactive component, X _ibe i-th grid-connected equivalent impedance Z of permanent-magnet synchronous Wind turbine _ireaction component, Z _i=R _i+ jX _i; P _i, Q _ibe respectively the power S that front i-th the permanent-magnet synchronous Wind turbine of fault exports to electrical network _iactive power and reactance capacity, S _i=P _i+ jQ _i.

I-2) the power given value of the pusher side current transformer of i-th permanent-magnet synchronous Wind turbine is changed according to following formula:

$p_{i-ref}=K_2\&CenterDot;u_{i-pu}\&CenterDot;\frac{P_i}{P_N}$

q _i-ref＝0

Wherein, p _i-ref, q _i-refbe respectively meritorious, the idle set-point of i-th permanent-magnet synchronous unit pusher side current transformer, K ₂for power control ratio, 0≤K ₂≤ 1;

II, net side converter reactive power support control strategy: for the dynamic reactive electric current making wind farm grid-connected point inject electrical network during low voltage crossing reaches the GB requirement grid-connected to Large Scale Wind Farm Integration, during low voltage crossing, the net side converter of the permanent-magnet synchronous Wind turbine of i-th in wind energy turbine set is calculated to the dynamic reactive given value of current value i of each permanent-magnet synchronous Wind turbine according to following formula _q-refwith active current set-point i _d-ref:

i _q-ref≥1.5×(0.9-u _i-pu)i _N

$i_{d-ref}\&le;\sqrt{i_N^2-i_{q-ref}^2}$

Wherein, i _nfor the load current value of separate unit permanent-magnet synchronous Wind turbine.

Variable pitch suppression strategy of gaining merit is: utilize PI controller according to the propeller pitch angle set-point θ of bias adjustment i-th permanent-magnet synchronous Wind turbine wind wheel blade of generator speed to i-th permanent-magnet synchronous Wind turbine _i-ref, make wind wheel be transported to the active-power P of pusher side current transformer _i-wtwith the power given p of pusher side current transformer _i-refequal, thus suppress to gain merit due to pusher side current transformer to consume the permanent-magnet synchronous Wind turbine fluctuation of speed that causes of control strategy, impact to reduce the DC tache voltage caused due to line voltage rapid drawdown.

Fig. 3 to Fig. 8 adopts the present invention to propose control method to utilize crowbar circuit unloading method at the simulation comparison waveform realizing each quantity of state of low voltage crossing period PMSG unit with tradition respectively, embodies Wind turbines and adopts during low voltage crossing herein based on the superiority of the control method for coordinating of power-balance.In Fig. 3 to Fig. 8, solid line sets forth and adopts PMSG unit when the present invention is based on the control method for coordinating of power-balance to gain merit power output, idle power output, generating unit speed, propeller pitch angle, power coefficient and current transformer DC voltage simulation curve, and dotted line is then result when adopting traditional crow bar discharging circuit to control.From each figure, when wind energy turbine set leading-out terminal leading-out terminal generation Voltage Drop, when adopting control method of the present invention, unit output of gaining merit has and reduces to ensure that corresponding reactive power support exports a little, the input action of propeller pitch angle brings the rapid reduction of power coefficient, stabilizes PMSG generating unit speed steadily (change is limited in 4%) on the one hand; On the other hand owing to not using crowbar circuit, avoid the voltge surge of the current transformer DC side caused due to crowbar circuit switching during low voltage crossing, add system reliability.After voltage resume, because generating unit speed rises limited, system energy recovers normal operation within a short period of time.Wind turbines can keep being incorporated into the power networks during whole low voltage crossing.

Although the present invention with preferred embodiment openly as above, embodiment is not of the present invention for limiting.Without departing from the spirit and scope of the invention, any equivalence change done or retouching, belong to the protection range of the present invention equally.Therefore the content that protection scope of the present invention should define with the claim of the application is standard.

Claims (2)

1., based on a permanent-magnet synchronous wind energy turbine set low voltage crossing control method for coordinating for power-balance, it is characterized in that, comprise the steps:

1) the wind farm grid-connected point voltage value V of Real-Time Monitoring _out, calculate wind farm grid-connected point voltage perunit value wherein V _out-reffor and site reference voltage base value;

2) as 0.9≤V _puwhen≤1.1, adopt normality control strategy to make each permanent-magnet synchronous Wind turbine in wind energy turbine set be operated in unit power factor pattern, return step 1) carry out next round control, otherwise enter step 3);

Described normality control strategy refers to and adopts maximal power tracing to control to each permanent-magnet synchronous Wind turbine in wind energy turbine set;

3) V is worked as _pu< 0.2 or V _puduring > 1.1, cut off wind farm grid-connected outlet, make each permanent-magnet synchronous Wind turbine off-grid in wind energy turbine set, method ends; Otherwise enter step 4);

4) power coordination control strategy is adopted to each permanent-magnet synchronous Wind turbine in wind energy turbine set, then enter step 5);

Described power coordination control strategy comprises current transformer power distribution strategies and variable pitch and to gain merit suppression strategy;

Described current transformer power distribution strategies comprises pusher side current transformer meritorious consumption control strategy and net side converter reactive power support control strategy, and concrete control strategy is as follows:

I, pusher side current transformer are meritorious consumes control strategy:

I-1) in control procedure, i-th permanent-magnet synchronous Wind turbine set end voltage u in wind energy turbine set is calculated _i, calculate the set end voltage perunit value of i-th permanent-magnet synchronous Wind turbine u _nit is the rated voltage of i-th permanent-magnet synchronous Wind turbine;

I-2) the power given value of the pusher side current transformer of i-th permanent-magnet synchronous Wind turbine is changed according to following formula:

$p_{i-ref}=K_2\&CenterDot;u_{i-pu}\&CenterDot;\frac{P_i}{P_N}$

q _i-ref＝0

Wherein, p _i-ref, q _i-refbe respectively meritorious, the idle set-point of i-th permanent-magnet synchronous unit pusher side current transformer, K ₂for power control ratio, 0≤K ₂≤ 1;

II, net side converter reactive power support control strategy: for the dynamic reactive electric current making wind farm grid-connected point inject electrical network during low voltage crossing is up to state standards " wind energy turbine set access power system technology specify " requirement grid-connected to Large Scale Wind Farm Integration, during low voltage crossing, the net side converter of the permanent-magnet synchronous Wind turbine of i-th in wind energy turbine set is calculated to the dynamic reactive given value of current value i of each permanent-magnet synchronous Wind turbine according to following formula _q-refwith active current set-point i _d-ref:

i _q-ref≥1.5×(0.9-u _i-pu)i _N

$i_{d-ref}\&le;\sqrt{i_N^2-i_{q-ref}^2}$

Wherein, i _nfor the load current value of separate unit permanent-magnet synchronous Wind turbine;

Described variable pitch suppression strategy of gaining merit is: utilize PI controller according to the propeller pitch angle set-point θ of bias adjustment i-th permanent-magnet synchronous Wind turbine wind wheel blade of generator speed to i-th permanent-magnet synchronous Wind turbine _i-ref, make wind wheel be transported to the active-power P of pusher side current transformer _i-wtwith the power given p of pusher side current transformer _i-refequal, thus suppress to gain merit due to pusher side current transformer to consume the permanent-magnet synchronous Wind turbine fluctuation of speed that causes of control strategy, impact to reduce the DC tache voltage caused due to line voltage rapid drawdown

5) monitor wind farm grid-connected point voltage in step 1) institute monitor V _puvalue on the T that holds time, when T exceedes national standard " wind energy turbine set access power system technology regulation " corresponding requirements, cut off wind farm grid-connected outlet, make each permanent-magnet synchronous Wind turbine off-grid in wind energy turbine set, method ends; Otherwise enter step 6);

6) carry out meritorious recovery to control, return step 1) carry out next round control;

Described meritorious recovery controls to refer to the dynamic reactive given value of current value i net side converter of the permanent-magnet synchronous Wind turbine of i-th in wind energy turbine set being calculated to each permanent-magnet synchronous Wind turbine according to following formula _q-refwith active current set-point i _d-ref:

i _q-ref＝0

$\frac{P_i}{P_N}\&le;i_{d-ref}\&le;K_1$

Wherein, subscript i is the sequence number of each permanent-magnet synchronous Wind turbine, P _ifor the active power that front i-th the permanent-magnet synchronous Wind turbine of fault exports to electrical network, P _nbe the rated power of i-th permanent-magnet synchronous Wind turbine, K ₁be the power limit of the net side converter of i-th permanent-magnet synchronous Wind turbine, 1≤K ₁≤ 1.2.

2. the permanent-magnet synchronous wind energy turbine set low voltage crossing control method for coordinating based on power-balance according to claim 1, is characterized in that, described step 4) in i-th permanent-magnet synchronous Wind turbine set end voltage u _ibe calculated as follows:

$u_i=V_{out}+\frac{P_i{R}_i+Q_i{X}_i}{V_{out}}$

Wherein, R _ibe i-th grid-connected equivalent impedance Z of permanent-magnet synchronous Wind turbine _iactive component, X _ibe i-th grid-connected equivalent impedance Z of permanent-magnet synchronous Wind turbine _ireaction component, Z _i=R _i+ jX _i; P _i, Q _ibe respectively the power S that front i-th the permanent-magnet synchronous Wind turbine of fault exports to electrical network _iactive power and reactance capacity, S _i=P _i+ jQ _i.