For making object of the present invention, technical scheme and advantage clearly understand, below in conjunction with drawings and Examples, the present invention is described in further detail.Should be appreciated that embodiment described herein only in order to explain the present invention, do not limit protection scope of the present invention.
The structural representation of the dynamic reactive compensation device of the present invention in an embodiment has been shown in Fig. 1.As shown in Figure 1, the dynamic reactive compensation device in the present embodiment comprises:
System-level control unit 101, for obtaining operation of power networks parameter, this operation of power networks parameter comprises: line voltage, power network current and electric network state amount information, and determine to correspond to the control objectives under this present control mode according to present control mode, and according to this control objectives, analyzing and processing is carried out to described operation of power networks parameter, export corresponding idle reference quantity, described present control mode comprises control model and comprises: any one in stable state control model, transient control mode, distant place control model;
Unit Level control unit 102, for carrying out function passes process according to described idle reference quantity, provides corresponding PWM (PulseWidthModulation, pulse width modulation) reference wave;
Component-level control unit 103, for producing the control impuls controlling inverter bridge work according to described PWM reference wave.
According to the scheme of the embodiment of the present invention as above, it is that the mode of employing three layers of classification controls to realize dynamic passive compensation, thus has good fast dynamics, fast response time, the stability of transient voltage can be improved, dynamic reactive power support is provided.
Accordingly, the theory structure schematic diagram of the muti-layer control tactics based on these three layers of grading control modes has been shown in Fig. 2.
Composition graphs 2 is visible, system-level control unit is in the position of top level control, it is mainly based on present control mode, with target to be compensated for control object (control objectives), determine overall Compensation Objectives, provide corresponding idle reference quantity (reference instruction), solve the input signal problem of whole control system.And Unit Level control unit is in the position that middle level controls, mainly determines to need which signal according to the target of top level control, how to utilize these signals, and provide PWM reference wave, and what solve is the problem of implementation of whole control system transfer function.Component-level control unit is in the position that lower floor controls, and mainly according to PWM reference wave, produces the control impuls controlling inverter bridge work, the output problem of whole control system that what it solved is.
Wherein, above-mentioned electric network state amount information can comprise bus connection switch state, can know two female paired runnings or two mother stock open shop by bus connection switch state, when System Reactive Power, can also know and get the idle of the idle of two-way or single channel.
In a concrete example, said elements level control unit 103 also regulates described control impuls, to control the Dead Time of power device switch, minimum service time and minimum turn-off time.
Below in conjunction with concrete example, that yuan 102 of said system level control unit 101, Unit Level control and component-level control unit 103 are illustrated respectively.
For system-level control unit 101, as mentioned above, the position of top level control is in, it is mainly based on present control mode, with target to be compensated for control object (control objectives), determine overall Compensation Objectives, provide corresponding idle reference quantity (reference instruction).
As mentioned above, in the scheme of inventive embodiments, present control mode comprises control model and comprises: stable state control model, transient control mode, distant place control model, wherein, this stable state control model specifically can comprise System Reactive Power control model, perseverance is idle/constant current controlling pattern, constant voltage control model three kinds.Below now be illustrated for each control model.
Under System Reactive Power control model, be mainly used in the idle of control system side, its control objectives is target or the scope of the idle of system side or power factor.
Perseverance is idle/constant current controlling pattern, and be mainly used in control device and export idle, its control objectives is the idle or electric current that device exports constant size.Idle accuracy and step response speed can be followed the tracks of by measurement mechanism in this way.
Constant voltage control model, is mainly used in control PCC point voltage level.Device makes the voltage stabilization of system in user's setting voltage desired value or setting range by regulating its idle output.When the Voltage Reference that system voltage sets lower than user, device exports capacitive reactive power with elevator system voltage; When system voltage is higher than this value, it is idle to reduce system voltage that device exports perception.
Transient control mode, mainly in order to the transient disturbance of answering system voltage, jump or fall control temporarily for answering system voltage or PCC voltage, when transient disturbance appears in system voltage, device detects this disturbance and adjusts output at once, to support rapidly or to reduce system voltage in several ms.Select to determine whether to enable this control mode by control model, if enable, this control mode priority is higher than stable state control model.
As mentioned above, the control objectives of transient control mode mainly suppresses transient voltage to change, and the possible cause that transient voltage changes comprise break down and load significantly uprush, feature is that voltage declines very soon, be likely monotonic decreasing, result will be transient voltage unstability and cause low pressure to discharge load.In order to maintain Transient Voltage Stability and reduce low pressure release load, under this transient control mode, require that on the one hand dynamic reactive compensation device can the larger capacity of dynamic compensation, require that dynamic reactive compensation device has response speed faster on the other hand.The fast dynamics of dynamic reactive compensation device has significant effect to minimizing release load, support voltage levvl, the response time of device is shorter, action effect is better, found by actual tests, the benefit when device response time is 30ms (millisecond) improves 58% than during 80ms.
Distant place control model is the transient disturbance of tackling electrical network, and when applying this pattern, dynamic reactive compensation device should carry out sufficient idle deposit when meeting operation of power networks condition, and therefore, this pattern also can be referred to as idle deposit control model.The control objectives of this distant place control model, is under systematic steady state runs, retains capacitive reactive power as much as possible for subsequent use, supports with the dynamic reactive strengthening electrical network
The logical construction schematic diagram of the system-level control unit in an embodiment has been shown in Fig. 3, and in shown in Fig. 3, U represents line voltage, and I represents power network current, U
pCCrepresent access point information of voltage, coordination between each control model and switch and can select module management by a unified control model, the information such as required line voltage, power network current and electric network state amount, can be provided by voltage and current measurement-data preprocessing module.In addition, choosing logic and can being adjusted by man-machine interface of control model, in addition, can also set the controling parameters in various control model by man-machine interface.According to selected control model and running situation (line voltage, power network current and electric network state amount information etc.), corresponding idle reference quantity Q can be obtained
This is idle reference quantity Q
refcan be input to Unit Level control unit 102, Unit Level reference unit 102 is in conjunction with this idle reference quantity Q
refwith access point information of voltage U
pcc, calculate the current reference value I that 3-phase power converter need export
ref_ca, and then exporting corresponding PWM reference wave, component-level control unit produces control impuls, with the work of control inverter based on this PWM reference wave.
Unit Level control unit 102 is carrying out function passes process to idle reference quantity, and when determining corresponding PWM reference wave, mainly comprise two processes, one is the generation of reference current, and another is the tracking of transient current.The generation of reference current, namely according to idle reference quantity and access point information of voltage, calculate the current reference value that 3-phase power converter need export, and the tracking of transient current can be undertaken by phase-splitting Instantaneous Control strategy.Phase-splitting transient current tracing controls the feature with quick follow load curent change, and its fast response time, to the strong adaptability of system voltage.Adopt phase-splitting transient current tracing algorithm to carry out function passes process to idle reference quantity, greatly can improve the ability that device withstands shocks, reduce the sensitiveness to system voltage sudden change, thus improve the reliability of device.The process of concrete generating reference electric current and the function passes process of transient current tracing, can adopt current existing routine to transmit processing mode and carry out, repeat no longer in detail at this.
When component-level control unit 103 produces based on the reference wave that Unit Level control unit 102 exports the control impuls controlling inverter bridge work, can carry out based on PWM method., can also regulate control impuls meanwhile, control with the Dead Time to power device switch, minimum service time and minimum turn-off time.
In PWM method, the most basic one is two level SPWM methods, and its principle as shown in Figure 4.The output of two level SPWM methods has two level :+E ,-E, and wherein, E represents direct voltage.Sinusoidal modulation wave and triangular carrier are compared, when sinusoidal modulation wave is greater than triangular carrier, current transformer exports+E level, otherwise then exports-E level.In shown in Fig. 4, (a) represents modulating wave and carrier wave, and (b) represents inverter output voltage).
When carrying out condition to control impuls, can carry out based on dead-time compensation control mode.It is the additional harmonic brought to reduce dead time effect that dead-time compensation controls, and compensates Dead Time, makes inverter obtain that expect or better output performance.The principle of dead-time compensation as shown in Figure 5.
In shown in Fig. 5, (a) is the compensation principle schematic diagram to positive voltage pulse, and (b) is the compensation principle schematic diagram to negative voltage pulse, wherein i
lfor load current, t
cmfor the dead time compensation time of power cell, be also the Dead Time of setting, P
a3the pipe up and down (namely to pipe) of a power model brachium pontis respectively, P
a4for the pipe up and down (namely to pipe) of another brachium pontis of power model.Compensation method be Dead Time is arranged to the pwm pulse of complementation while compensate.
For the pwm pulse of complementation, according to the not same-action to output voltage pulse, may be defined as main pulse and auxiliary pulse, the width of wherein main pulse determines the pulse duration of output voltage.The definition of main pulse, auxiliary pulse is followed the change in load current direction and changes, at load current i
lwhen being greater than zero, P
a1main pulse, P
a3it is auxiliary pulse; Load current i
lwhen being less than zero, P
a3main pulse, P
a1it is auxiliary pulse.
The concrete grammar of dead-time compensation can be: first Real-time Collection load current i
ldirection, and determine main pulse and auxiliary pulse, then respectively arranging size to the rising edge of main pulse and trailing edge is t
cmtime delay, at the rising edge of auxiliary pulse, 2t is set
Comprehensive foregoing can be learnt, embodiment of the present invention scheme can possess following characteristics and advantage:
1) improve Enhancement of Transient Voltage Stability, prevent voltage collapse accident;
2) provide dynamic reactive to support, voltage resume after acceleration disturbance, reduce low pressure release load;
3) according to the needs of dispatching of power netwoks and control, the stable state pressure regulation of day-to-day operation can also be participated in part reactive capability; There is provided damping to control, suppress electric network power oscillation; As the subelement of AVC system, participate in the whole network REACTIVE POWER/VOLTAGE CONTROL.
Each technical characteristic of the above embodiment can combine arbitrarily, for making description succinct, the all possible combination of each technical characteristic in above-described embodiment is not all described, but, as long as the combination of these technical characteristics does not exist contradiction, be all considered to be the scope that this specification is recorded.
The above embodiment only have expressed several execution mode of the present invention, and it describes comparatively concrete and detailed, but can not therefore be construed as limiting the scope of the patent.It should be pointed out that for the person of ordinary skill of the art, without departing from the inventive concept of the premise, can also make some distortion and improvement, these all belong to protection scope of the present invention.Therefore, the protection range of patent of the present invention should be as the criterion with claims.