CN102340259A - Novel instantaneous-current-direct-control-based pulse width modulation current tracking control method - Google Patents
Novel instantaneous-current-direct-control-based pulse width modulation current tracking control method Download PDFInfo
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Abstract
The invention discloses a novel instantaneous-current-direct-control-based pulse width modulation current tracking control method, which relates to the field of current tracking control methods for grid-connected inverter equipment in the field of power electronics. When output current regulation is performed in each cycle, an instantaneous voltage value of a direct current side and an instantaneous voltage value of a power grid are sampled, the action of effective instantaneous current vectors of an inverter in different on/off states is analyzed to obtain a control formula for instantaneous current shift factors, the action time of each effective instantaneous current shift factor at a corresponding moment is calculated, and control over the action time of different instantaneous current shift factors is realized in the next regulation cycle in a pulse width modulation way by utilizing functions of a pulse width modulation (PWM) peripheral of a digital signal processor (DSP) chip to finish the shift of a current instantaneous current vector to an instantaneous reference current vector of the next moment, thereby fulfilling the aim of controlling the reference current tracking of output current. The method is convenient to use, simple in operation, quick in current tracking response and low in deviation, and compared with the conventional methods, is highly advanced.
Description
Technical field
The present invention relates to the curren tracing control method technical field of grid type contravariant equipment in the modern power electronic field, particularly based on the directly actuated novel pulse width modulation electrical current tracking and controlling method of transient current.
Background technology
For inverter such as types such as generation of electricity by new energy inversion grid connection equipment such as APF (active power filter), SVG (silent oscillation reacance generator), photovoltaic and wind-force; Its output directly inserts electrical network through series reactor; Output end voltage supports through line voltage, and the function of this type device mainly realizes through controlling output current trace command electric current accurately and fast.The production method of dissimilar grid type inverter instruction currents is different; But after instruction current produces, all have the problem of how effectively controlling actual output current trace command electric current, this link is from directly affect the final performance index of a whole set of parallel network reverse device to a great extent.Traditional curren tracing control method comprises the method for the stagnant ring control of typical current, space vector of voltage control and some distortion; This all conventional method in fact all needs master control system that the output current of reality is carried out real-time detection and relatively confirms the inverter circuit on off state through the and instruction electric current; This has just proposed very high requirement to inverter master control system data processing speed; Switching frequency with 20KHZ is an example; Require the master control system current ratio to be at least 40KHZ than control frequency; Promptly every separated 25us carries out output current regulation and control; Add instruction current computing and other necessary data processing that device need carry out; Even so fast rate request uses the high-speed dsp chip also to be difficult to satisfy, the output current deviation increases, output current wave degenerates and low excessively switching speed can cause, and out put reactor increases, equipment cost increases, the output current response speed reduces; So the equipment that adopts the conventional current tracking and controlling method from promoting current response speed, improve the output current wave quality, reduce aspects such as shunt reactor volume, weight and consider, mostly has to increase specialized circuitry or chip satisfies the requirement of electric current being regulated and control speed.
Summary of the invention
The present invention seeks to provides a kind of based on the directly actuated novel pulse width modulation electrical current tracking and controlling method of transient current to above weak point.
1), sampling dc voltage instantaneous value, common frequency power network instantaneous voltage for solving the problems of the technologies described above, technical scheme of the present invention is: based on the directly actuated novel pulse width modulation electrical current tracking and controlling method of transient current, may further comprise the steps:; 2), the different operating state of inverter circuit is analyzed, draw the controllable current vector under the corresponding different inverter circuit operating state; 3), to step 2) the controllable current vector that draws handles, and correspondingly draws the transient current shift factor; 4), the transient current shift factor that draws according to step 3), the action time that calculating needs, actual current is carried out pulse-width modulation; 5), start the PWM peripheral functionality that carries on the dsp chip; The cycle parameter of PWM is set according to predetermined current regulation and control cycle ts; The numerical value that draws according to the described pulse duration modulation method of step 4) is provided with the pwm pulse width; In the next one regulation and control cycle, do not need DSP to intervene like this, the PWM peripheral hardware will be realized the transfer control of output transient current vector is made output current trace command change in current through the control to the inverter circuit on off state according to setup parameter automatically.
As further improvement, the described controlled step that also comprises frequency multiplication PWM based on the directly actuated novel pulse width modulation electrical current tracking and controlling method of transient current.The controlled step of said frequency multiplication PWM is at two current displacement factors of one-period inner control alternating action twice respectively, and be original 1/2 each action time.
As further improvement; Step 2) method that draws of described controllable current vector is: the operating state 1 of inverter circuit: output current is that forward, T1 manage conducting; It is Ve1 that this moment E1 terminal voltage the time is established in the E1 discharge, and grid side voltage is Us, and the current numerical value of output current is ic; T1 pipe ON time is Trp, can draw Δ ic_rp=((Ve1-Us)/Lc) * Trp; The operating state 2 of inverter circuit: output current is that forward, T1 manage shutoff, and establishing this moment E2 terminal voltage is Ve2, and grid side voltage is Us, and the initial numerical value of output current is ic, and T1 manages not that ON time is Tdp, can draw Δ ic_dp=-((Ve2+Us)/Lc) * Tdp; The operating state 3 of inverter circuit: output current is that negative sense, T2 manage conducting, the E2 discharge, and establishing at this moment, the E2 terminal voltage is Ve2; Grid side voltage is Us; The initial numerical value of output current is ic, and T2 pipe ON time is Trn, can draw Δ ic_rn=-((Ve2+Us)/Lc) * Trn; The operating state 4 of inverter circuit: output current is that negative sense, T2 manage shutoff, and establishing this moment E1 terminal voltage is Ve1, and grid side voltage is Us, and the initial numerical value of output current is ic, and T2 manages not that ON time is Tdn, can draw Δ ic_dn=((Ve1-Us)/Lc) * Tdn.
As further improvement; The method that draws of the described transient current shift factor of step 3) is the transient current shift factor for the displacement of current phasor in the definition unit interval; Being designated as δ ic, according to step 2) expression formula of the controllable current vector that draws correspondingly draws one group of definition about the transient current shift factor:
δ ic_rp=(Ve1-Us)/Lc selects for use when just, still needing forward to increase at output current;
δ ic_dp=-(Ve2+Us)/Lc at output current for just, select for use when needing forward to reduce;
δ ic_rn=-(Ve2+Us)/Lc select for use when oppositely increasing for bearing, still needing at output current;
δ ic_dn=(Ve1-Us)/Lc is to bear, select for use in the time of need oppositely reducing at output current.
As further improvement, the described pulse duration modulation method of step 4) is that k moment actual current can obtain through real-time sampling, be designated as i (k); The k+1 of expectation constantly current value is designated as i (k+1), and the definition of the transient current shift factor that draws according to step 3) can be known:
When output current is correct time, suppose that the service time of T1 pipe is t1, the shutoff of T1 pipe is t2, row are able to next prescription formula
δic_rp*t1+δic_dp*t2＝i(k+1)-i(k)
t1+t2＝ts
Consider to open driving time-delay t0, the driving time of actual T1 pipe should be
T1_on＝t1+t0＝(i(k+1)-i(k)-δic_dp*ts)/(δic_rp-δic_dp)+t0；
When output current when negative, suppose that the service time of T2 pipe is t1, the turn-off time of T2 pipe is t2, is listed as and is able to next prescription formula
δic_rn*t1+δic_dn*t2＝i(k+1)-i(k)
t1+t2＝ts
For the convenient PWM of realization controls, consideration T1, T2 in inverter circuit adopt the driving method of complementary conducting, and counting the influence of opening time-delay t0 can draw
T1_on＝t2-t0＝(i(k+1)-i(k)-δic_rn*ts)/(δic_dn-δic_rn)-t0；
Because of making primary current, moves: δ ic_rp=δ ic_dn=δ ic_r=(Ve1-Us)/Lc again to the positive axis top;
δ ic_dp=δ ic_rn=δ ic_d=-(Ve2+Us)/Lc makes primary current move to negative axle below;
Can draw:
t1_on＝(i(k+1)-i(k)-δic_d*ts)/(δic_r-δic_d)+λ*t0
Wherein
λ＝1 i(k)＞＝0
λ＝-1 i(k)＜0
δic_r＝(Ve1-Us)/Lc
δic_d＝-(Ve2+Us)/Lc。
Beneficial effect of the present invention is: of the present invention based on the directly actuated novel pulse width modulation electrical current tracking and controlling method of transient current; When the phase is carried out the output current regulation and control weekly; Through sampling dc voltage instantaneous value, common frequency power network instantaneous voltage; Utilize the control formula of the transient current shift factor that the present invention provides to draw each significant instant current displacement factor of this moment; Utilize dsp chip PWM peripheral functionality; In next regulation and control cycle, realize the control of action time of different transient current shift factor through the pulse-width modulation means, accomplish current transient current vector downward and instruct the transfer of transient current vector constantly, thereby realize the controlled target of output current trace command electric current.On this basis, the present invention proposes further that frequency multiplication PWM current tracking control improves formula and the practical applications method improves switching frequency, improves the current tracking precision.
The data of two level APF emulation experiments are following:
Experiment one:
If regulation and control cycle ts=100us
Adopt the conventional current tracking and controlling method: the switching frequency with 10KHZ is an example; Require the master control system current ratio to be at least 20KHZ than control frequency; Promptly every separated 50us carries out output current regulation and control, and actual available pulse duration has only (0,0.5,1) these three points;
Adopt that the present invention proposes based on the directly actuated novel pulse width modulation electrical current tracking and controlling method of transient current: the switching frequency with 10KHZ is an example; Master control system only needs the every 100us of DSP (10KHZ) to carry out the regulation and control of an output current; Can obtain the switching frequency of 10KHZ by the PWM peripheral functionality of DSP; Pulse duration can according to the control needs interval (0, ts) go up value.
Experiment two:
Adopt the conventional current tracking and controlling method: the switching frequency with 20KHZ is an example, requires the master control system current ratio to be at least 40KHZ than control frequency, and promptly every separated 25us carries out output current regulation and control;
Adopt that the present invention proposes based on the directly actuated novel pulse width modulation electrical current tracking and controlling method of transient current: the switching frequency with 20KHZ is an example; Master control system only needs every 100us (10KHZ) to carry out the regulation and control of an output current; Adopt the frequency multiplication PWM control method of the present invention's proposition, can obtain the switching frequency of 20KHZ by the PWM peripheral functionality of DSP.
Experiment through above proves; This invention propose based on the directly actuated novel pulse width modulation electrical current tracking and controlling method convenient in application of transient current, computing is simple, the current tracking response speed is fast, deviation is little, on the difficulty of Project Realization and control precision, all have an enormous advantage than conventional method.
Description of drawings
Fig. 1 is that the three-phase power active filter is used sketch map;
Fig. 2 is the single-phase brachium pontis sketch map of three-phase power active filter;
Fig. 3 is the transient current polar plot;
Fig. 4 is a PWM curren tracing control method sketch map of the present invention;
Fig. 5 is a frequency multiplication PWM curren tracing control method sketch map of the present invention.
Embodiment
In the grid type inverter; The output current of inverter be the most directly, the most important control target; The new type of control method that the present invention proposes can directly realize the effective control to real-time current, makes corresponding inversion system have very fast output current response speed and control accuracy.Be the technical thought of this invention of example explanation below with typical two level, 3 brachium pontis active power filtering devices; Method proposed by the invention can be easy to promote the use of in the grid type inverter of other pattern.
As shown in Figure 1, provide the three-phase power active filter and use sketch map, be easy analysis, provide the definition of some conventional signs among this paper below:
The us--point voltage that is incorporated into the power networks;
Is--mains side electric current;
If--load-side electric current;
Ic--APF exports offset current;
Vdc--APF DC side total voltage;
Ve1--capacitor E1 terminal voltage;
Ve2--capacitor E2 terminal voltage;
Lc--APF exports series reactance.
The summary of APF basic functional principle:
If respectively holding electric current is positive direction to point to load-side all, there is is+ic=if to set up, i.e. is=if-ic;
Because nonlinear load comprises the humorous idle component that involves in load current, can load current be decomposed into:
if＝if1p+if1q+∑ifh
If1p is the first-harmonic real component in the load current in the formula,
If1q is the fundamental reactive component in the load current,
∑ ifh is the stack of each harmonic electric current.
According to different compensation rules, when control APF output current ic=∑ ifh, can obtain:
is＝if-ic＝if1p+if1q+∑ifh-∑ifh＝if1p+if1q
Can find out that through following formula under this control law, the mains side electric current after overcompensation only comprises the meritorious and idle component of first-harmonic, has not had the harmonic wave composition.
When the adjustment control law, during control APF output current ic=∑ ifh+if1q, can obtain:
is＝if-ic＝if1p+if1q+∑ifh-∑ifh-if1q＝if1p
Can find out that this moment, the mains side electric current only comprised the first-harmonic real component, had not had fundamental wave reactive power and harmonic wave composition.
As shown in Figure 2, adopt the electric current variation characteristic under the single-phase simplification circuit labor different conditions.Consider that electric current regulation and control cycle T s is very little, be generally 100us and following, be set in regulation and control cycle inner capacitor terminal voltage Ve1, Ve2 and a mains side power-frequency voltage instantaneous value and remain unchanged, series reactor is unsaturated in the work engineering.In fact, this hypothesis at E1, that the E2 capacity is chosen is suitable, the reactor capacity is chosen under the correct situation is fully reasonably.
Be the variation situation of example labor output current under inverter circuit different operating state below with single-phase brachium pontis.
State 1: output current is that forward, T1 manage conducting, the E1 discharge, and the output current forward increases; The variation of the service time decision output current of T1 pipe; If this moment, the E1 terminal voltage was Ve1 (k), grid side voltage is Us (k), and the current numerical value of output current is ic (k); T1 pipe ON time is Trp, can draw:
ic(k+1)＝((Ve1(k)-Us(k))/Lc)*Trp+ic(k)
That is: ic (k+1)-ic (k)=((Ve1 (k)-Us (k))/Lc) * Trp
Be designated as: Δ ic_rp (k+1)=((Ve1 (k)-Us (k))/Lc) * Trp
State 2: output current is that forward, T1 manage shutoff, and output current forward amplitude reduces, and D2 charges to E2 through continued flow tube; Under this state, whether T2 pipe is opened does not have influence to the variation of output current, and establishing this moment E2 terminal voltage is Ve2 (k), and grid side voltage is Us (k), and the initial numerical value of output current is ic (k), and T1 manages not that ON time is Tdp, can draw:
ic(k+1)＝-((Ve2(k)+Us(k))/Lc)*Tdp+ic(k)
That is: ic (k+1)-ic (k)=-((Ve2 (k)+Us (k))/Lc) * Tdp
Be designated as: Δ ic_dp (k+1)=-((Ve2 (k)+Us (k))/Lc) * Tdp
State 3: output current is that negative sense, T2 manage conducting, the E2 discharge, and the reverse amplitude of output current increases, the variation of the ON time decision output current of T2 pipe.If this moment, the E2 terminal voltage was Ve2 (k), grid side voltage is Us (k), and the initial numerical value of output current is ic (k), and T2 pipe ON time is Trn, can draw:
ic(k+1)＝-((Ve2(k)+Us(k))/Lc)*Trn+ic(k)
That is: ic (k+1)-ic (k)=-((Ve2 (k)+Us (k))/Lc) * Trn
Be designated as: Δ ic_rn (k+1)=-((Ve2 (k)+Us (k))/Lc) * Trn
State 4: output current is that negative sense, T2 manage shutoff, and the reverse amplitude of output current reduces, and charges to E1 through the parallelly connected continued flow tube D1 of T1, and at this moment, T1 manages whether conducting is to the output current did not influence.If this moment, the E1 terminal voltage was Ve1 (k), grid side voltage is Us (k), and the initial numerical value of output current is ic (k), and T2 manages not that ON time is Tdn, can draw:
ic(k+1)＝((Ve1(k)-Us(k))/Lc)*Tdn+ic(k)
That is: ic (k+1)-ic (k)=((Ve1 (k)-Us (k))/Lc) * Tdn
Be designated as: Δ ic_dn (k+1)=((Ve1 (k)-Us (k))/Lc) * Tdn
As shown in Figure 3, i (k+1) is a k+1 transient current vector constantly, and i (k) is a k transient current vector constantly, and Δ i (k+1) is the extra current vector that control transient current vector i (k) arrives i (k+1).Draw the controllable current vectorial combination formula under the corresponding different inverter circuit operating state through above analysis:
((Ve1-Us)/Lc) * Trp output current is effective for T1 pipe conducting in correct time, and the output current forward increases for Δ ic_rp=;
Δ ic_dp=-((Ve2+Us)/Lc) * Tdp output current for correct time T1 pipe close effectively, the output current forward reduces;
(it is effective that T2 managed conducting when (Ve2+Us)/Lc) * Trn output current was negative, and output current oppositely increases for Δ ic_rn=-;
Δ ic_dn=(closed effectively when (Ve1-Us)/Lc) * Tdn output current was negative, and output current oppositely reduces by the T2 pipe;
Regulation and control cycle T s enough weak point, dc bus capacitor device E1, E2 capacity rationally reach out put reactor Lc and do not take place under the saturated situation, more than the effect of four transient current vectors determined the variation of output current fully.In fact in above four transient current vectors; It is effective when output current is in opposed polarity, having only two current phasors wherein; And each transient current vector is corresponding with switching states, and this has fully shown the controllability of above transient current vector.
For making things convenient for practical applications, with four controllable current vector expressions that can be used for the transient current vector control
Δic_rp＝((Ve1-Us)/Lc)*Trp
Δic_dp＝-((Ve2+Us)/Lc)*Tdp
Δic_rn＝-((Ve2+Us)/Lc)*Trn
Δic_dn＝((Ve1-Us)/Lc)*Tdn
Further handle, the displacement of current phasor is the transient current shift factor in the definition unit interval, is designated as δ ic, correspondingly draws one group of definition about the transient current shift factor, respectively the effect of each transient current shift factor is described below.
δ ic_rp=(Ve1-Us)/Lc selects for use when just, still needing forward to increase at output current, and promptly effectively, electric current forward increase depends on and this vector action time is designated as tpr after the conducting of T1 pipe;
For just, select for use when needing forward to reduce, the T1 pipe is closed the back promptly effectively to δ ic_dp=-(Ve2+Us)/Lc at output current, and electric current forward decrease depends on and this vector action time is designated as tpd;
δ ic_rn=-(Ve2+Us)/Lc output current for negative, select for use when still needing reverse the increase, promptly effectively, the current reversal increase depends on and this vector action time is designated as tnr after the conducting of T2 pipe;
δ ic_dn=(Ve1-Us)/Lc output current for negative, select for use in the time of need oppositely reducing, the T2 pipe is closed the back promptly effectively, the current reversal decrease depends on and this vector action time is designated as tnd;
More than four formulas be labeled as 2-2-1 combination formula
Find out from above four formula:
δic_rp＝δic_dn，δic_dp＝δic_rn
2-2-1 combination formula can be noted by abridging and is:
δ ic_r=(Ve1-Us)/Lc makes primary current move to the positive axis top;
δ ic_d=-(Ve2+Us)/Lc makes primary current move to negative axle below;
More than two formulas be labeled as 2-2-2 combination formula
In fact when inverter circuit being adopted complementary conducting control method; Have only two independently transient current shift factors; Separately be to consider when complementary conducting is controlled, to drive time-delay t0 for each pipe has increased to open, and the influence of t0 is different under different state for preventing that upper and lower pipe is straight-through here.Analysis from behind can be found out, does analysis by four shift factors here the compensation deals to t0 are more readily understood.
From 2-2-1 combination formula; Four parameters of the instantaneous value of Ve1, Ve2, Us and Lc have determined the transient current shift factor uniquely; Current change quantity depends on the action time of shift factor fully in arbitrary specific modulation period, can be designated as: and Δ ic=δ ic*t t ∈ (0, ts).In practical application, be that galvanic current is pressed always through effective means control Ve1 and Ve2; And amplitude is higher than the peak value of Us; Lc can be considered constant, and the instantaneous value of Ve1-Us and Ve2+Us just is always in the therefore top row formula, and numerical values recited is followed the variation of Us and is cyclic variation.
In the grid type inverter circuit; As long as modulation period is enough short, the storage capacitor capacity is enough big, out put reactor is unsaturated; Can be similar to and think that the current displacement factor under the different on off states remains unchanged in this cycle in a regulation and control cycle, the variable quantity of transient current depends on the action time of the current displacement factor fully; In a certain specific modulation period,, there are and only have two kinds of current displacement factors effective when output current is correct time.When the conducting of control T1 pipe, the output current forward increases, and current displacement factor ic_rp has characterized the electric current rate of climb; Have no progeny when control T1 pipe closes, no matter whether the T2 pipe is open-minded, output current all will be forward and reduce trend, and current displacement factor ic_dp has characterized the electric current decrease speed; In a certain specific modulation period, when output current when negative, have and only have two kinds of current displacement factors effective.When the conducting of control T2 pipe, output current oppositely increases, and current displacement factor ic_rn has characterized the reverse rate of climb of output current; Have no progeny when control T2 pipe closes, no matter whether the T1 pipe is open-minded, output current all will be and oppositely reduce trend, and current displacement factor ic_dn has characterized the electric current decrease speed.
Shown in Figure 4 like the right side, at k constantly, the k+1 moment current value that obtains expectation through the instruction current operation program is designated as i (k+1), and k actual current constantly can obtain through real-time sampling, is designated as i (k); The target of current tracking control is exactly in next modulation period, to make i (k) be transferred to i (k+1) through the effective control to the inverter circuit on off state.
Can draw according to above-mentioned 2-2-1 combination formula:
When output current is correct time, have only two current displacement factors of δ ic_rp and δ ic_dp to work, be that the service time of T1 pipe is t1 the action time of supposing δ ic_rp, and be that the shutoff of T1 pipe is t2 the action time of δ ic_dp, and row are able to next prescription formula:
δic_rp*t1+δic_dp*t2＝i(k+1)-i(k)
t1+t2＝ts
Can be in the hope of t1=(i (k+1)-i (k)-δ ic_dp*ts)/(δ ic_rp-δ ic_dp)
Consider to open driving time-delay t0, the driving time of actual T1 pipe should be:
T1_on=t1+t0=(i (k+1)-i (k)-δ ic_dp*ts)/(δ ic_rp-δ ic_dp)+t0 (formula 3-1-1)
When output current when negative; Have only two current displacement factors of δ ic_rn and δ ic_dn to work; Suppose that the action time of δ ic_rn and the service time of T2 pipe are t1, the turn-off time of the action time of δ ic_dn and T2 pipe is t2, and row are able to next prescription formula:
δic_rn*t1+δic_dn*t2＝i(k+1)-i(k)
t1+t2＝ts
Can be in the hope of t2=(i (k+1)-i (k)-δ ic_rn*ts)/(δ ic_dn-δ ic_rn)
For the convenient PWM of realization controls, consideration T1, T2 in inverter circuit adopt the driving method of complementary conducting, and counting the influence of opening time-delay t0 can release:
T1_on=t2-t0=(i (k+1)-i (k)-δ ic_rn*ts)/(δ ic_dn-δ ic_rn)-t0 (formula 3-1-2)
Because of making primary current, moves: δ ic_rp=δ ic_dn=δ ic_r=(Ve1-Us)/Lc again to the positive axis top;
δ ic_dp=δ ic_rn=δ ic_d=-(Ve2+Us)/Lc makes primary current move to negative axle below;
Above 3-1-1 and 3-1-2 formula can be merged into:
t1_on＝(i(k+1)-i(k)-δic_d*ts)/(δic_r-δic_d)+λ*t0
(formula 3-1-3)
Wherein
λ＝1 i(k)＞＝0
λ＝-1 i(k)＜0
δic_r＝(Ve1-Us)/Lc
δic_d＝-(Ve2+Us)/Lc
Formula 3-1-3 provides one group of complete pulse-width modulation formula that is used for the real-time current tracking Control.When carrying out practical engineering application; Selecting DSP for use is CPU; Start the PWM peripheral functionality that carries on the dsp chip; Regulate and control the cycle parameter that cycle ts is provided with PWM according to predetermined current, the numerical value that calculates by the 3-1-3 formula is provided with the pwm pulse width, in the next one regulation and control cycle, does not need DSP to intervene like this; The PWM peripheral hardware will be realized the transfer control of output transient current vector is made output current trace command change in current through the control to the inverter circuit on off state according to setup parameter automatically.
As shown in Figure 5, the algorithm of employing formula 3-1-3 can realize that k moment current phasor i (k) is through the transfer to i (k+1) in the k+1 moment of the path of A-D-F.AF is the minimum transfer path of tracing process deviation among the figure, also is optimal transfer path.The area of triangle Δ ADF can be used to characterize the transfer process deviation, follows effect for improving better certainly, reduces deviation, should reduce the area of triangle Δ ADF as far as possible.Theoretical explanation through former joints can be found out; After modulation period, ts was fixing; The area of triangle Δ ADF is that current tracking process deviation is decided by dc voltage (Ve1, Ve2), mains side voltage U s and output series reactor Lc; Suitably reduce dc voltage in some cases or increase reactor Lc and can improve the current tracking error to a certain extent, but can cause the reduction of current following ability thus.
The present invention further proposes the control thought of frequency multiplication PWM on above basis; As shown in Figure 5; Through distinguishing twice of alternating action in two current displacement factors of a ts cycle inner control; Be original 1/2 each action time, and output current will be transferred to k+1 F point constantly by k A point constantly according to the A-B-C-E-F path, completion current tracking controlled target.The tracing process deviation is the area sum of Δ ABC and Δ CEF, and obviously the area than Δ ADF is little a lot, and the current tracking precision is able to further raising.After adopting frequency multiplication PWM control method; It is constant that the computing cycle that master control system is carried out instruction current, the significant instant current displacement factor and action time still remains ts; Just when carrying out the parameter configuration of PWM peripheral hardware, carrying out simple modification can realize; Certainly this is a cost to improve the inverter circuit switching frequency, and because the switch number of times of inverter circuit switch element increases, opens the compensation of delay amount accordingly and need adjust.If the frequency multiplication number of times that needs is n, formula 3-1-3 respective change is more general formula:
T1_on=(i (k+1)-i (k)-δ ic_d*ts)/(δ ic_r-δ ic_d)+λ * n*t0 (formula 3-2-1)
Wherein
λ＝1 i(k)＞＝0
λ＝-1 i(k)＜0
δic_r＝(Ve1-Us)/Lc
δic_d＝-(Ve2+Us)/Lc
After in practical engineering application, selecting n frequency multiplication controlling schemes for use; When the PWM peripheral hardware of DSP is provided with; The PWM cycle changes the configuration by ts/n, and after pulse duration was provided with by t1_on/n, need not the extra intervention of DSP can be achieved easily; So after adopting the algorithm of the present invention's proposition, do not increasing the switching frequency that can promote inverter circuit under the main control unit operand situation at an easy rate according to actual needs.
Claims (6)
1. based on the directly actuated novel pulse width modulation electrical current tracking and controlling method of transient current, it is characterized in that: may further comprise the steps
1), sampling dc voltage instantaneous value, common frequency power network instantaneous voltage;
2), the different operating state of inverter circuit is analyzed, draw the controllable current vector under the corresponding different inverter circuit operating state;
3), to step 2) the controllable current vector that draws handles, and correspondingly draws the transient current shift factor;
4), the transient current shift factor that draws according to step 3), the action time that calculating needs, actual current is carried out pulse-width modulation;
5), start the PWM peripheral functionality that carries on the dsp chip; The cycle parameter of PWM is set according to predetermined current regulation and control cycle ts; The numerical value that draws according to the described pulse duration modulation method of step 4) is provided with the pwm pulse width; In the next one regulation and control cycle, do not need DSP to intervene like this, the PWM peripheral hardware will be realized the transfer control of output transient current vector is made output current trace command change in current through the control to the inverter circuit on off state according to setup parameter automatically.
2. according to claim 1 based on the directly actuated novel pulse width modulation electrical current tracking and controlling method of transient current, it is characterized in that: the described controlled step that also comprises frequency multiplication PWM based on the directly actuated novel pulse width modulation electrical current tracking and controlling method of transient current.
3. according to claim 2 based on the directly actuated novel pulse width modulation electrical current tracking and controlling method of transient current; It is characterized in that: the controlled step of said frequency multiplication PWM is at two current displacement factors of one-period inner control alternating action twice respectively, and be original 1/2 each action time.
4. according to claim 1 based on the directly actuated novel pulse width modulation electrical current tracking and controlling method of transient current, it is characterized in that: step 2) method that draws of described controllable current vector does
The operating state 1 of inverter circuit: output current is that forward, T1 manage conducting, and it is Ve1 that this moment E1 terminal voltage the time is established in the E1 discharge, and grid side voltage is Us, and the current numerical value of output current is ic, and T1 pipe ON time is Trp, can draw
Δic_rp＝((Ve1-Us)/Lc)*Trp
The operating state 2 of inverter circuit: output current is that forward, T1 manage shutoff, and establishing this moment E2 terminal voltage is Ve2, and grid side voltage is Us, and the initial numerical value of output current is ic, and T1 manages not that ON time is Tdp, can draw
Δic_dp＝-((Ve2+Us)/Lc)*Tdp
The operating state 3 of inverter circuit: output current is that negative sense, T2 manage conducting, E2 discharge, and establishing this moment E2 terminal voltage is Ve2, and grid side voltage is Us, and the initial numerical value of output current is ic, and T2 pipe ON time is Trn, can draw
Δic_rn＝-((Ve2+Us)/Lc)*Trn
The operating state 4 of inverter circuit: output current is that negative sense, T2 manage shutoff, and establishing this moment E1 terminal voltage is Ve1, and grid side voltage is Us, and the initial numerical value of output current is ic, and T2 manages not that ON time is Tdn, can draw
Δic_dn＝((Ve1-Us)/Lc)*Tdn。
5. according to claim 4 based on the directly actuated novel pulse width modulation electrical current tracking and controlling method of transient current, it is characterized in that: the method that draws of the described transient current shift factor of step 3) does
The displacement of current phasor is the transient current shift factor in the definition unit interval, is designated as δ ic, according to step 2) the controllable current vector that draws correspondingly draws one group of definition about the transient current shift factor
δ ic_rp=(Ve1-Us)/Lc selects for use when just, still needing forward to increase at output current;
δ ic_dp=-(Ve2+Us)/Lc at output current for just, select for use when needing forward to reduce;
δ ic_rn=-(Ve2+Us)/Lc select for use when oppositely increasing for bearing, still needing at output current;
δ ic_dn=(Ve1-Us)/Lc is to bear, select for use in the time of need oppositely reducing at output current.
6. according to claim 5 based on the directly actuated novel pulse width modulation electrical current tracking and controlling method of transient current, it is characterized in that: the described pulse duration modulation method of step 4) does
K actual current constantly can obtain through real-time sampling, is designated as i (k); The k+1 of expectation constantly current value is designated as i (k+1), and the definition of the transient current shift factor that draws according to step 3) can be known:
When output current is correct time, suppose that the service time of T1 pipe is t1, the shutoff of T1 pipe is t2, row are able to next prescription formula
δic_rp*t1+δic_dp*t2＝i(k+1)-i(k)
t1+t2＝ts
Consider to open driving time-delay t0, the driving time of actual T1 pipe should be
T1_on＝t1+t0＝(i(k+1)-i(k)-δic_dp*ts)/(δic_rp-δic_dp)+t0；
When output current when negative, suppose that the service time of T2 pipe is t1, the turn-off time of T2 pipe is t2, is listed as and is able to next prescription formula
δic_rn*t1+δic_dn*t2＝i(k+1)-i(k)
t1+t2＝ts
For the convenient PWM of realization controls, consideration T1, T2 in inverter circuit adopt the driving method of complementary conducting, and counting the influence of opening time-delay t0 can draw
T1_on＝t2-t0＝(i(k+1)-i(k)-δic_rn*ts)/(δic_dn-δic_rn)-t0；
Because of making primary current, moves: δ ic_rp=δ ic_dn=δ ic_r=(Ve1-Us)/Lc again to the positive axis top;
δ ic_dp=δ ic_rn=δ ic_d=-(Ve2+Us)/Lc makes primary current move to negative axle below;
Can draw:
t1_on＝(i(k+1)-i(k)-δic_d*ts)/(δic_r-δic_d)+λ*t0
Wherein
λ＝1 i(k)＞＝0
λ＝-1 i(k)＜0
δic_r＝(Ve1-Us)/Lc
δic_d＝-(Ve2+Us)/Lc。
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103929083A (en) * | 2014-04-17 | 2014-07-16 | 中国矿业大学 | Pulse alternation control method suitable for five-level H-bridge cascade type STATCOM |
| CN104505838A (en) * | 2015-01-15 | 2015-04-08 | 信元瑞电气有限公司 | Pulse-width modulation (PWM) method with electric current rapid tracking and stabilizing |
| CN105929720A (en) * | 2016-06-17 | 2016-09-07 | 山东理工大学 | Current tracking control method and device |
| CN108880309A (en) * | 2018-08-02 | 2018-11-23 | 山东建筑大学 | A kind of three direct tracking and controlling method of level grid-connected converter transient current of I type |
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| CN1658485A (en) * | 2005-03-10 | 2005-08-24 | 上海交通大学 | Counter control current tracking control method based on average current compensation |
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Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103929083A (en) * | 2014-04-17 | 2014-07-16 | 中国矿业大学 | Pulse alternation control method suitable for five-level H-bridge cascade type STATCOM |
| CN103929083B (en) * | 2014-04-17 | 2016-08-24 | 中国矿业大学 | A kind of pulse rotation control method being applicable to five level H-bridge cascade connection types STATCOM |
| CN104505838A (en) * | 2015-01-15 | 2015-04-08 | 信元瑞电气有限公司 | Pulse-width modulation (PWM) method with electric current rapid tracking and stabilizing |
| CN105929720A (en) * | 2016-06-17 | 2016-09-07 | 山东理工大学 | Current tracking control method and device |
| CN105929720B (en) * | 2016-06-17 | 2017-06-30 | 山东理工大学 | A kind of curren tracing control method and device |
| CN108880309A (en) * | 2018-08-02 | 2018-11-23 | 山东建筑大学 | A kind of three direct tracking and controlling method of level grid-connected converter transient current of I type |
| CN108880309B (en) * | 2018-08-02 | 2019-08-23 | 山东建筑大学 | A kind of three direct tracking and controlling method of level grid-connected converter transient current of I type |
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