CN105048442A - Variable-current control strategy for direct-current island wind power delivery - Google Patents
Variable-current control strategy for direct-current island wind power delivery Download PDFInfo
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- CN105048442A CN105048442A CN201510528795.8A CN201510528795A CN105048442A CN 105048442 A CN105048442 A CN 105048442A CN 201510528795 A CN201510528795 A CN 201510528795A CN 105048442 A CN105048442 A CN 105048442A
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Abstract
The invention discloses a variable-current control strategy for direct-current island wind power delivery. According to the strategy, in the running process of a system, a direct-current reference value Idref is continuously changed to meet the control requirements of controllable and variable power in transmission; firstly, the direct-current reference value Idref of a sending-end system is calculated in real time, and control is carried out according to the reference current to meet the requirements of the transmission power of the system; and secondly, in the control process, when power change is overlarge, a current protection module is added to ensure normal operation of the system. According to the variable-current control strategy, the requirements on a conventional power unit caused by direct-current island wind power delivery are reduced; the utilization rate of wind energy is improved; the investment is reduced; and safe and stable operation of a direct-current island system is ensured through the current protection module.
Description
Technical field
The present invention mainly solves wind power direct current isolated island sending when not having enough thermoelectricity proportionings, and the problem of sending conveying wind-powered electricity generation, belongs to technical field of electric power transmission.
Background technology
Wind-powered electricity generation is due to the advantage of its uniqueness in recent years, develops at high speed.But because wind-powered electricity generation has fluctuation by air speed influence, for the wind power system not having enough thermoelectricity proportionings, especially wind-powered electricity generation islanded system, when adopting direct current conveying, i.e. wind power direct current islanded system, cannot adopt constant dc power control conveying wind-powered electricity generation in the past.For this reason, the present invention proposes a kind of time-dependent current control strategy can following the tracks of wind-powered electricity generation change, conveying controllable variable power.This strategy has broad application prospects for marine wind electric field or away from the wind energy turbine set of coal-electricity base, can save the investment of a large amount of conventional power unit, reduce costs.
Summary of the invention
For the marine wind electric field away from the supporting deficiency of thermal power plant near the land wind energy turbine set of coal-electricity base or wind energy turbine set, if adopted, conventional to determine that power wind fire banking arrangement sends outside be infeasible.The object of the invention is to the drawback for above-mentioned technology, reduce the normal power supplies such as the thermoelectricity of proportioning needed for conveying wind-powered electricity generation, to develop wind energy resources better, reduce investment, improve the utilance of wind energy resources.
Problem of the present invention realizes with following technical proposals:
Consider the feature of wind power fluctuation, propose time-dependent current control strategy.This strategy, by system operation, constantly changes direct current reference value I
drefmeet the control overflow of conveying controllable variable wind-powered electricity generation.First by calculating the reference value I of sending direct current in real time
dref, then control according to reference current, meet the requirement of system transmission power; Secondly, in control procedure, when changed power is excessive, in order to ensure that system is normally run, overcurrent protection module is added.
Above-mentioned a kind of direct current isolated island sends the time-dependent current control strategy of wind-powered electricity generation outside, carries out according to following steps:
A. the reference current I of sending Current Control is calculated in real time
dref, then control according to reference current, meet the requirement of system transmission power;
B., in control procedure, when changed power is excessive, increases overcurrent protection module and normally run with guarantee system.
Above-mentioned a kind of direct current isolated island sends the time-dependent current control strategy of wind-powered electricity generation outside, calculates the reference current I of sending Current Control in real time
drefstep as follows:
1. the calculating of the real-time transmission power of direct current system.
Because wind speed has randomness, wind power prediction value and actual blower fan power output have deviation, and wind power prediction value therefore can not be used as wind energy turbine set realtime power value.Therefore make:
P
drefn＝P
dref(n-1)+ΔP(1)
ΔP＝P
run(n-1)-P
run(n-2)(2)
In formula: P
drefnbe the setting value of the n-th period direct current power, the namely real-time transmission power of direct current system; P
dref (n-1)be the setting value of (n-1)th period direct current power, its value can be set to wind power prediction value when initial; P
run (n-1)it is the actual power that (n-1)th period wind energy turbine set sends; P
run (n-2)it is the actual power that the n-th-2 period wind energy turbine set send; Δ P is direct current power adjustment amount.
2. the reference current I of sending Current Control
drefcalculating.
Known direct current transportation transmission power meets:
P
d＝U
dI
d(3)
In formula: P
dfor direct current transmission power, U
dfor direct voltage; I
dfor direct current.
Therefore direct current reference value can be calculated by following formula:
In formula: U
drefnit is the measured value of the n-th period direct voltage; I
drefnit is the n-th period direct current reference value.Known according to formula (4), as long as obtain P
drefnvalue, just can draw electric current I
drefnvalue, thus calculate the n-th period Trigger Angle α
nvalue, according to α
ncarry out the control of thyristor, just can reach the object exporting controllable variable power.
Above-mentioned a kind of direct current isolated island sends the time-dependent current control strategy of wind-powered electricity generation outside, in control procedure, when changed power is excessive, increases overcurrent protection module and normally runs with guarantee system.Its principle and implementation step as follows:
In time-dependent current control procedure, when converter Trigger Angle α changes, voltage and current all can fluctuate.Consider the restriction of equipment withstand voltage level and receiving end voltage definite value, the fluctuation of voltage should have a zone of reasonableness; When the current changes, excessive current fluctuation amplitude or rate of change all can impact system, such as commutation failure fault may occur, and amplitude or the fluctuation speed of therefore current fluctuation also should have a rational scope.Meet the above constraints required as follows:
I
dmin＜I
d＜I
dmax(5)
U
dmin＜U
d＜U
dmax(6)
P
dmin＜P
d＜P
dmax(7)
I
dn＝I
d(n-1)+ΔI
d(n-1)(8)
ΔI
d＜ΔI
drefmax(9)
In formula: under be designated as min, max amount represent the minimum of this variable and maximum respectively; I
dnit is the current setting of the n-th period; Δ I
d (n-1)for the increment of n-1 and n-2 two adjacent time interval current values; Δ I
drefmaxrepresent that adjacent time interval electric current allows the amplitude peak of change.
Formula (5) (6) represent the excursion of electric current and voltage in system cloud gray model region respectively; Formula (7) is the changed power scope in system cloud gray model region, when going beyond the scope, need system to change operational mode, and blower fan needs to make corresponding actions, as abandoned wind, cutting machine; The amplitude that formula (8) is adjacent time interval current fluctuation, if the knots modification of electric current is excessive, likely causes the problem of commutation failure, for avoiding the generation of this problem, adds the curent change limiting element shown in formula (9).
Accompanying drawing explanation
Fig. 1 is that in invented time-dependent current control strategy, voltage-to-current (U-I) runs schematic diagram.As seen from Figure 1, in time-dependent current control strategy, U-I range of operation is no longer some points or a line, but a region.In certain period, reference current is definite value, and guarantee system reaches steady operational status in section at this moment; Can change the reference value of electric current as required in the next period, thus the system that reaches carries the object of a controllable variable power.In Fig. 1: U
dfor direct voltage, I
dfor direct current, α
minfor minimum trigger angle (generally getting 3-5 °), VDCL (VoltageDependentCurrentLimit) are current limiting low-voltage control mode.
Direct current system rectification side each parameter simulation curve when Fig. 2 is wind power random fluctuation.
Direct current system inverter side each parameter simulation curve when Fig. 3 is wind power random fluctuation.
Fig. 4 is overcurrent protection module block diagram.
Embodiment
Above-mentioned a kind of direct current isolated island sends the time-dependent current control strategy of wind-powered electricity generation outside, is for the feature of wind power with fluctuations in wind speed, by direct current system running, constantly changes direct current reference value I
drefmeet a kind of control method of conveying controllable variable wind-powered electricity generation.This implementation of strategies mainly contains two parts content: one is the reference current I by calculating sending Current Control in real time
dref, then control according to reference current, meet the requirement of system transmission power; Two is in control procedure, when wind power change is excessive, in order to ensure that system is normally run, increases overcurrent protection module.
Direct current system run existing control mode have determine voltage control, Given current controller, determine α angle control etc., its feature may be summarized to be controlled variable and is definite value.The time-dependent current control strategy that the present invention carries and the maximum difference part of existing control mode are, its variable of controlling is no longer a definite value, but a range of operation.As shown in Figure 1, the range of operation of direct current system electric current and voltage is no longer a point or a line, but a region.Policy mandates system to control variable be a definite value within the n-th period, and the different periods needs to calculate corresponding control variable value.If the upper limit in voltage Out-of Control Area territory, then system can transfer to and determines α
minangle controls; If voltage is lower than the lower limit of control area, then system can transfer VDCL (VoltageDependentCurrentLimit) current limiting low-voltage pattern to.
The present invention calculates the reference current I of sending Current Control in real time
drefembodiment as follows:
1. the calculating of the real-time transmission power of direct current system.
Because wind speed has randomness, wind power prediction value and actual blower fan power output have deviation, and wind power prediction value therefore can not be used as wind energy turbine set realtime power value.Therefore make:
P
drefn＝P
dref(n-1)+ΔP(10)
ΔP＝P
run(n-1)-P
run(n-2)(11)
In formula: P
drefnbe the setting value of the n-th period direct current power, the namely real-time transmission power of direct current system; P
dref (n-1)be the setting value of (n-1)th period direct current power, its value can be set to wind power prediction value when initial; P
rum (n-1)be the actual power P that (n-1)th period wind energy turbine set sends
run (n-2)it is the actual power that the n-th-2 period wind energy turbine set send; Δ P is direct current power adjustment amount.
2. the reference current I of sending Current Control
drefcalculating.
Direct current reference value can be calculated by following formula:
In formula: U
drefnit is the measured value of the n-th period direct voltage; I
drefnit is the n-th period direct current reference value.As long as therefore obtain P
drefnvalue, just can draw electric current I
drefnvalue, thus calculate the n-th period Trigger Angle α
nvalue, according to α
ncarry out the control of thyristor, just can reach the object exporting controllable variable power.
The present invention, when wind power change is excessive, in order to ensure that system is normally run, increases overcurrent protection module.The embodiment of overcurrent protection module is as follows:
Time-dependent current control strategy requirement system transmission power of carrying can not change too fast, otherwise before likely the power oscillation of generation systems n-1 period is not calmed down, start again the Current adjustment of next period, thus cause Commutation Failure, the safe operation of influential system.Therefore, the increase transmission power of sending and the constraints of direct current are:
P
dmin＜P
d＜P
dmax(13)
I
dn＝I
d(n-1)+ΔI
d(n-1)(14)
ΔI
d＜ΔI
drefmax(15)
The amount being wherein designated as down min, max represents the minimum of this variable and maximum respectively; I
dnit is the current setting of the n-th period; Δ I
dfor the increment of adjacent time interval current value; Δ I
drefmaxrepresent the amplitude peak that adjacent time interval curent change allows.
When the change of direct current system transmission power is excessive, system-computed obtains Δ I
dexceed Δ I
drefmax, now starting current protection module, as shown in Figure 4, current increment reference value is chosen as Δ I
drefmax, now direct current system current reference value I
dn=I
d (n-1)+ Δ I
drefmax.In order to ensure that transmission power balances, now needing wind energy turbine set to make cooperation, changing operational mode, such as, abandon wind or cut machine.
Instance analysis
Build wind power direct current isolated island simulation model, sending adopts the time-dependent current control strategy proposed in invention, when fluctuations in wind speed, transfers out the fluctuating power of wind energy turbine set in real time, carries out Example Verification to invention strategy.
During wind power random fluctuation, each parameter simulation result of rectification side is shown in accompanying drawing 2.As can be seen from accompanying drawing 2 (a): when wind speed random fluctuation, the time-dependent current control strategy proposed is adopted to control, rectification side DC voltage fluctuation amplitude is little, and only when power fluctuation is larger, voltage just there will be of short duration obvious fluctuation, can return to normal operating voltage subsequently; Now, direct voltage, electric current all in change, but do not exceed time-dependent current control area scope.In order to follow wind power change, time-dependent current control strategy constantly changes direct current reference value I
dref, as shown in accompanying drawing 2 (b), and DC current measures I
dfollow I
drefchange.As can be seen from accompanying drawing 2 (c), the I that rectification side Trigger Angle α angle reaches given to control electric current
dref, regulate in change always.Wind speed change at random, wind power follows change, and adopt time-dependent current control strategy of carrying, direct current system outputs the power of this change at random, as shown in accompanying drawing 2 (d).
Inverter side adopts constant DC voltage control mode.As can be seen from accompanying drawing 3: DC voltage keeps constant substantially; Inverter side Trigger Angle α follows at angle DC voltage variation; Direct current I
dchange consistent with the curent change of rectification side; Voltage, electric current are all within controlled range.
Example Verification institute invention direct current isolated island sends the validity of the time-dependent current control strategy of wind-powered electricity generation outside.
Claims (4)
1. direct current isolated island sends a time-dependent current control strategy for wind-powered electricity generation outside, it is characterized in that, for the U-I specificity analysis of direct current system time-dependent current control mode, obtains the time-dependent current range of operation of direct current isolated island delivery system; By calculating the reference value I of sending end direct current system direct current in real time
dfef, then control according to reference current, meet the requirement of system transmission power; In control procedure, when changed power is excessive, in order to ensure that system is normally run, add overcurrent protection module.
2. a kind of direct current isolated island according to claim 1 sends the time-dependent current control strategy of wind-powered electricity generation outside, and it is characterized in that, time-dependent current control strategy carries out according to following steps:
A. the reference current I of sending end direct current system Current Control is calculated in real time
dref, then control according to reference current, meet the requirement of system transmission power;
B., in control procedure, when changed power is excessive, increases overcurrent protection module and normally run with guarantee system.
3. a kind of direct current isolated island according to claim 2 sends the time-dependent current control strategy of wind-powered electricity generation outside, it is characterized in that, calculates the reference current I of sending end direct current system Current Control in real time
drefmethod be:
Direct current reference value is calculated by following formula:
In formula: U
drefnit is the measured value of the n-th period direct voltage; I
drefnit is the n-th period direct current system current control reference.According to above formula, as long as obtain P
drefnvalue, just can draw electric current I
drefnvalue, thus calculate the n-th period Trigger Angle α
nvalue, according to α
ncarry out the control of thyristor, just can reach the object exporting controllable variable power.
P
drefncalculating adopt following solution, order
P
drefn＝P
dref(n-1)+ΔP
ΔP＝P
run(n-1)-P
run(n-2)
In formula: P
drefnit is the setting value of the n-th period direct current power; P
dref (n-1)be the setting value of (n-1)th period direct current power, its value can be set to wind power prediction value when initial; P
run (n-1)it is the actual power that (n-1)th period wind energy turbine set sends; P
run (n-2)it is the actual power that the n-th-2 period wind energy turbine set send; Δ P is direct current power adjustment amount.
4. a kind of direct current isolated island according to claim 2 sends the time-dependent current control strategy of wind-powered electricity generation outside, it is characterized in that, in control procedure, when changed power is excessive, the step increasing overcurrent protection module is:
When the change of direct current system transmission power is excessive, system-computed obtains adjacent time interval current reference value variation delta I
dexceed adjacent time interval curent change allowable value Δ I
drefmax, now starting current protection module, current increment reference value is chosen as Δ I
drefmax, now direct current system current reference value I
dn=I
d (n-1)+ Δ I
drefmax.In order to ensure that transmission power balances, now needing wind energy turbine set to make cooperation, changing operational mode, such as, abandon wind or cut machine.
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|---|---|---|---|
| CN201510528795.8A CN105048442B (en) | 2015-08-26 | 2015-08-26 | A kind of direct current isolated island sends the power transformation flow control policy of wind-powered electricity generation outside |
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Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20100207456A1 (en) * | 2005-03-18 | 2010-08-19 | Wisconsin Alumni Research Foundation | Control of small distributed energy resources |
| CN104037788A (en) * | 2014-06-16 | 2014-09-10 | 东南大学 | Wind fire bundling system control device and method thereof |
-
2015
- 2015-08-26 CN CN201510528795.8A patent/CN105048442B/en active Active
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20100207456A1 (en) * | 2005-03-18 | 2010-08-19 | Wisconsin Alumni Research Foundation | Control of small distributed energy resources |
| CN104037788A (en) * | 2014-06-16 | 2014-09-10 | 东南大学 | Wind fire bundling system control device and method thereof |
Non-Patent Citations (2)
| Title |
|---|
| 姚伟等: "直流输电技术在海上风电场并网中的应用", 《中国电力》 * |
| 陈霞等: "基于多端直流输电的风电并网技术", 《电工技术学报》 * |
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