CN102340259B - 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 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 the inverter of the types such as generation of electricity by new energy inversion grid connection equipment such as such as APF (active power filter), SVG (silent oscillation reacance generator), photovoltaic and wind-force, its output directly accesses electrical network through series reactor, output end voltage supports by line voltage, and the function of this class device mainly realizes by controlling accurately and fast output current trace command electric current.The production method difference of dissimilar grid type inverter instruction current, 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 affecting to a great extent the final performance index of a whole set of parallel network reverse device.Traditional curren tracing control method comprises typical Hysteresis Current control, the method of space vector of voltage control and some distortion, this all conventional method in fact all need master control system to actual output current carry out real-time detection and by and instruction electric current relatively determine inverter circuit on off state, this has just proposed very high requirement to inverter master control system data processing speed, taking the switching frequency of 20KHZ as example, require master control system current ratio to be at least 40KHZ compared with control frequency, carry out output current regulation and control every 25us, add instruction current computing and other necessary data processings that device need to carry out, even if so fast rate request uses high-speed dsp chip to be also difficult to meet, and too low switching speed can cause output current deviation to increase, output current wave degenerates, out put reactor increases, equipment cost increases, output current response speed reduces, so adopt the equipment of conventional current tracking and controlling method from motor current response speed, improve output current wave quality, reduce shunt reactor volume, the aspects such as weight are considered, mostly have to increase specialized circuitry or chip and meet the requirement to electric current regulation and control speed.
Summary of the invention
The present invention seeks to for above weak point, provide a kind of based on the directly actuated novel pulse width modulation electrical current tracking and controlling method of transient current.
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, comprise the following steps:; 2), the different operating state of inverter circuit is analyzed, draw the controllable current vector under corresponding different inverter circuit operating state; 3), to step 2) the controllable current vector processing that draws, correspondingly draw transient current shift factor; 4), according to step 3) the transient current shift factor that draws, calculate the action time needing, actual current is carried out to pulse-width modulation; 5), start the PWM peripheral functionality carrying on dsp chip, the cycle parameter of PWM is set according to predetermined electric current regulation and control cycle ts, according to step 4) numerical value that draws of described pulse duration modulation method arranges pwm pulse width, within the next one regulation and control cycle, do not need like this DSP to intervene, PWM peripheral hardware, by passing through that according to setup parameter the control of inverter circuit on off state is realized to the transfer control to output transient current vector automatically, makes the variation of output current trace command electric current.
As further improvement, the described control 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 control step of described frequency multiplication PWM is in one-period, to control two current displacement factors alternating actions 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 forward, the conducting of T1 pipe, when E1 electric discharge, establishing now E1 terminal voltage is Ve1, grid side voltage is Us, output current current value 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, if now E2 terminal voltage is Ve2, grid side voltage is Us, and the initial numerical value of output current is ic, it is Tdp that T1 manages not ON time, can draw Δ ic_dp=-((Ve2+Us)/Lc) * Tdp; The operating state 3 of inverter circuit: output current is negative sense, the conducting of T2 pipe, E2 electric discharge, if now E2 terminal voltage is Ve2, grid side voltage is Us, the initial numerical value of output current is ic, 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, if now E1 terminal voltage is Ve1, grid side voltage is Us, and the initial numerical value of output current is ic, it is Tdn that T2 manages not ON time, can draw Δ ic_dn=((Ve1-Us)/Lc) * Tdn.
As further improvement, step 3) method that draws of described transient current shift factor is that the displacement of current phasor in the definition unit interval is transient current shift factor, 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 transient current shift factor:
δ ic_rp=(Ve1-Us)/Lc output current for just, still need forward increase time select;
δ ic_dp=-(Ve2+Us)/Lc at output current for just, select while needing forward to reduce;
δ ic_rn=-(Ve2+Us)/Lc is to bear, still need while oppositely increase to select at output current;
δ ic_dn=(Ve1-Us)/Lc output current for negative, select need oppositely reduce time.
As further improvement, step 4) described pulse duration modulation method is that k moment actual current can obtain by real-time sampling, is designated as i (k); The k+1 moment current value of expecting is designated as i (k+1), according to step 3) definition of the transient current shift factor that draws is known:
When output current is timing, the service time of supposing T1 pipe is t1, and the shutoff of T1 pipe is t2, and 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 is when negative, the service time of suppose T2 pipe is t1, and 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
Realize for convenience PWM and control, consider that T1, T2 adopt the driving method of complementary conducting in inverter circuit, counting the impact of opening time delay t0 can draw
T1_on＝t2-t0＝(i(k+1)-i(k)-δic_rn*ts)/(δic_dn-δic_rn)-t0；
Again because: δ ic_rp=δ ic_dn=δ ic_r=(Ve1-Us)/Lc makes primary current mobile to positive axis top;
δ ic_dp=δ ic_rn=δ ic_d=-(Ve2+Us)/Lc makes primary current mobile 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, in the time that each cycle is carried out output current regulation and control, by sampling DC voltage instantaneous value, common frequency power network instantaneous voltage, utilize the dominated formulate of the transient current shift factor that the present invention provides to draw this moment each significant instant current displacement factor, utilize dsp chip PWM peripheral functionality, realize within next regulation and control cycle by pulse-width modulation means the control of action time of different transient current shift factor, complete the transfer of the downward time instructions transient current vector of current transient current vector, thereby realize the control target of output current trace command electric current.On this basis, the present invention further proposes the control of frequency multiplication PWM current tracking and improves formula and engineering application process and improve switching frequency, improve current tracking precision.
The data of two level APF emulation experiments are as follows:
Experiment one:
If regulation and control cycle ts=100us
Adopt conventional current tracking and controlling method: taking the switching frequency of 10KHZ as example, require master control system current ratio to be at least 20KHZ compared with control frequency, carry out output current regulation and control every 50us, actual available pulse duration only has (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: taking the switching frequency of 10KHZ as 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 need to go up value at interval (0, ts) according to controlling.
Experiment two:
Adopt conventional current tracking and controlling method: taking the switching frequency of 20KHZ as example, require master control system current ratio to be at least 40KHZ compared with control frequency, carry out output current regulation and control every 25us;
Adopt that the present invention proposes based on the directly actuated novel pulse width modulation electrical current tracking and controlling method of transient current: taking the switching frequency of 20KHZ as 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.
By above experimental results show that, that this invention proposes is convenient based on the directly actuated novel pulse width modulation electrical current tracking and controlling method application of transient current, computing is simple, current tracking fast response time, deviation are little, in the difficulty of Project Realization and control precision, all has an enormous advantage than conventional method.
Brief description of the drawings
Fig. 1 is three-phase power active filter application schematic diagram;
Fig. 2 is the single-phase brachium pontis schematic diagram of three-phase power active filter;
Fig. 3 is transient current polar plot;
Fig. 4 is PWM curren tracing control method schematic diagram of the present invention;
Fig. 5 is frequency multiplication PWM curren tracing control method schematic diagram of the present invention.
Embodiment
In grid type inverter, the output current of inverter is the most direct, 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.The technical thought of this invention is described as an example of typical two level 3 brachium pontis active power filters example below; 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, providing three-phase power active filter application schematic diagram, is easy analysis, provides the definition of some conventional signs herein below:
The grid-connected point voltage of us--;
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 hold electric current all to point to load-side as positive direction, have is+ic=if to set up, i.e. is=if-ic;
Due to nonlinear load, in load current, comprise the humorous idle component that involves, load current can be decomposed into:
if＝if1p+if1q+∑ifh
In formula, if1p is the first-harmonic real component in load current,
If1q is the fundamental reactive component in load current,
∑ ifh is the stack of individual harmonic current.
According to different offset rules, in the time controlling APF output current ic=∑ ifh, can obtain:
is＝if-ic＝if1p+if1q+∑ifh-∑ifh＝if1p+if1q
Can find out by above formula, under this control law, the mains side electric current after overcompensation only comprises first-harmonic gains merit and idle component, without Resonance Wave Composition.
When adjusting control law, while controlling APF output current ic=∑ ifh+if1q, can obtain:
is＝if-ic＝if1p+if1q+∑ifh-∑ifh-if1q＝if1p
Can find out, now mains side electric current only comprises first-harmonic real component, without fundamental wave reactive power and Resonance Wave Composition.
As shown in Figure 2, adopt the curent change feature under 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, a Ve2 and mains side power-frequency voltage instantaneous value and remain unchanged, series reactor is unsaturated in work engineering.In fact, this hypothesis at E1, that E2 capacity is chosen is suitable, reactor capacity is chosen correct in the situation that is completely reasonably.
Below taking single-phase brachium pontis as example labor under inverter circuit different operating state the variation situation of output current.
State 1: output current is forward, the conducting of T1 pipe, E1 electric discharge, output current forward increases, the service time of T1 pipe determines the variation of output current, if now E1 terminal voltage is Ve1 (k), grid side voltage is Us (k), and output current current value 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 by continued flow tube; Under this state, whether T2 pipe is opened the variation of output current without impact, and establishing now E2 terminal voltage is Ve2 (k), grid side voltage is Us (k), the initial numerical value of output current is ic (k), and it is Tdp that T1 manages not ON time, 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 negative sense, the conducting of T2 pipe, E2 electric discharge, the reverse amplitude of output current increases, and the ON time of T2 pipe determines the variation of output current.If now E2 terminal voltage is 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, charges to E1 through the continued flow tube D1 in parallel of T1, and now, T1 manages whether conducting there is no impact to output current.If now E1 terminal voltage is Ve1 (k), grid side voltage is Us (k), and the initial numerical value of output current is ic (k), and it is Tdn that T2 manages not ON time, 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 k+1 moment transient current vector, i (k) is k moment transient current vector, and Δ i (k+1) is the extra current vector of controlling transient current vector i (k) arrival i (k+1).Draw the controllable current vectorial combination formula under corresponding different inverter circuit operating state by above analysis:
Δ ic_rp=((Ve1-Us)/Lc) * Trp output current is that the conducting of timing T1 pipe is effective, and output current forward increases;
Δ ic_dp=-((Ve2+Us)/Lc) * Tdp output current is that timing T1 pipe is closed effectively, and output current forward reduces;
The T2 pipe conducting when negative of Δ ic_rn=-((Ve2+Us)/Lc) * Trn output current is effective, and output current oppositely increases;
When Δ ic_dn=((Ve1-Us)/Lc) * Tdn output current is negative, T2 pipe is closed effectively, and output current oppositely reduces;
Regulation and control cycle T s enough short, DC bus capacitor device E1, E2 capacity rationally and out put reactor Lc do not occur saturated in the situation that, the effect of above four transient current vectors has determined the variation of output current completely.In fact in above four transient current vectors, effective when output current only has two current phasors wherein during in opposed polarity, and each transient current vector is corresponding with the on off state of inverter, this has fully shown the controllability of above transient current vector.
For convenience of engineering application, by four controllable current vector expressions that can be used for 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 process, in the definition unit interval, the displacement of current phasor is transient current shift factor, is designated as δ ic, correspondingly draws one group of definition about transient current shift factor, respectively the effect of each transient current shift factor is described below.
Effectively δ ic_rp=(Ve1-Us)/Lc selects when just, still needing forward to increase at output current, and after the conducting of T1 pipe,, electric current forward increase depends on and this vector action time is designated as tpr;
δ ic_dp=-(Ve2+Us)/Lc is at output current for just, select while needing forward to reduce, and after closing effectively, electric current forward decrease depends on and this vector action time is designated as tpd T1 pipe;
δ ic_rn=-(Ve2+Us)/Lc output current for negative, still need while oppositely increase to select, after the conducting of T2 pipe, effectively, the reverse increase of electric current depends on and this vector action time is designated as tnr;
δ ic_dn=(Ve1-Us)/Lc output current for negative, select need oppositely reduce time, after closing effectively, the reverse decrease of electric current depends on and this vector action time is designated as tnd T2 pipe;
Above four formulas are 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 mobile to positive axis top;
δ ic_d=-(Ve2+Us)/Lc makes primary current mobile to negative axle below;
Above two formulas are labeled as 2-2-2 combination formula
In fact in the time that inverter circuit is adopted to complementary conducting control method, only have two independently transient current shift factors, be separately to consider to drive time delay t0 for preventing that upper, lower tube from leading directly to as each pipe has increased to open in the time of complementary conducting control, and the impact of t0 is different under different states herein.Analysis from behind can be found out, does analysis herein can make the compensation deals of t0 be easier to understand by four shift factors.
From 2-2-1 combination formula, tetra-parameters of the instantaneous value of Ve1, Ve2, Us and Lc have determined transient current shift factor uniquely, within arbitrary specific modulation period, current change quantity depends on the action time of shift factor completely, can be designated as: Δ ic=δ ic*t t ∈ (0, ts).Be always that galvanic current is pressed by effective means control Ve1 and Ve2 in actual applications, and amplitude is higher than the peak value of Us, Lc can be considered constant, and therefore above the instantaneous value of Ve1-Us and Ve2+Us is just always in row formula, and numerical values recited is followed the variation of Us and is cyclic variation.
In grid type inverter circuit, as long as enough short, storage capacitor capacity enough greatly, out put reactor is unsaturated modulation period, can be similar to the current displacement factor of thinking under interior different on off states of this cycle and remain unchanged within a regulation and control cycle, the variable quantity of transient current depends on the action time of the current displacement factor completely; Within a certain specific modulation period, when output current is timing, there are and only have two kinds of current displacement factors effective.In the time controlling the conducting of T1 pipe, output current forward increases, and current displacement factor ic_rp has characterized Current rise speed; Have no progeny when controlling T1 pipe pass, no matter whether T2 pipe is open-minded, output current all will be forward and reduce trend, and current displacement factor ic_dp has characterized electric current decrease speed; Within a certain specific modulation period, when output current is when negative, there are and only have two kinds of current displacement factors effective.In the time controlling the conducting of T2 pipe, output current oppositely increases, and current displacement factor ic_rn has characterized the reverse rate of climb of output current; Close and have no progeny when controlling T2 pipe, no matter whether T1 pipe is open-minded, output current all will be and oppositely reduce trend, and current displacement factor ic_dn has characterized electric current decrease speed.
As shown in right Fig. 4, in the k moment, obtain by instruction current operation program the k+1 moment current value of expecting and be designated as i (k+1), k moment actual current can obtain by real-time sampling, is designated as i (k); The target of current tracking control is exactly by making i (k) be transferred to i (k+1) to effective control of inverter circuit on off state within next modulation period.
Can draw according to above-mentioned 2-2-1 combination formula:
When output current is timing, only have 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 is when negative, only have 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)
Realize for convenience PWM and control, consider that T1, T2 adopt the driving method of complementary conducting in inverter circuit, counting the impact 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)
Again because: δ ic_rp=δ ic_dn=δ ic_r=(Ve1-Us)/Lc makes primary current mobile to positive axis top;
δ ic_dp=δ ic_rn=δ ic_d=-(Ve2+Us)/Lc makes primary current mobile 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 of following the tracks of to control for real-time current.While carrying out practical engineering application, selecting DSP is CPU, start the PWM peripheral functionality carrying on dsp chip, the cycle parameter of PWM is set according to predetermined electric current regulation and control cycle ts, the numerical value calculating by 3-1-3 formula arranges pwm pulse width, within the next one regulation and control cycle, do not need like this DSP to intervene, PWM peripheral hardware, by passing through that according to setup parameter the control of inverter circuit on off state is realized to the transfer control to output transient current vector automatically, makes the variation of output current trace command electric current.
As shown in Figure 5, adopt the algorithm of formula 3-1-3, can realize k moment current phasor i (k) through the transfer to i (k+1) in the k+1 moment of the path of A-D-F.In figure, AF is the transfer path of tracing process deviation minimum, is also optimal transfer path.The area of triangle Δ ADF can be used to characterize transfer process deviation, certainly follows effect for improving better, reduces deviation, should reduce the area of triangle Δ ADF as far as possible.Theoretical explanation by 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 in some cases DC voltage or increase reactor Lc and can improve to a certain extent current tracking error, but can cause thus the reduction of current following ability.
The present invention further proposes the control thought of frequency multiplication PWM on above basis, as shown in Figure 5, by control twice of two current displacement factors difference alternating action within a ts cycle, be original 1/2 each action time, output current, by be transferred to the F point in k+1 moment by the A point in k moment according to A-B-C-E-F path, completes current tracking control target.Tracing process deviation is the area sum of Δ ABC and Δ CEF, and obviously little a lot of than the area of Δ ADF, current tracking precision is able to further raising.Adopt after 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 in the time carrying out the parameter configuration of PWM peripheral hardware, carrying out simple modification can realize, certainly this is to improve inverter circuit switching frequency as cost, and because the on-off times of inverter circuit switch element increases, open accordingly compensation of delay amount and need adjust.If the frequency multiplication number of times needing 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
In practical engineering application, select after n frequency multiplication control program, when the PWM peripheral hardware of DSP is arranged, the PWM cycle changes by ts/n and configures, after pulse duration arranges by t1_on/n, the intervention extra without DSP can be achieved easily, so adopt after the algorithm of the present invention's proposition, do not increasing the switching frequency that can promote according to actual needs easily inverter circuit in main control unit operand situation.
Claims (5)
1. based on the directly actuated novel pulse width modulation electrical current tracking and controlling method of transient current, it is characterized in that: comprise the following 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 corresponding different inverter circuit operating state;
3), to step 2) the controllable current vector processing that draws, correspondingly draw transient current shift factor;
4), the transient current shift factor that draws according to step 3), calculate the action time needing, actual current is carried out to pulse-width modulation;
5), start the PWM peripheral functionality carrying on dsp chip, the cycle parameter of PWM is set according to predetermined electric current regulation and control cycle ts, the numerical value drawing according to the pulse duration modulation method described in step 4) arranges pwm pulse width, within the next one regulation and control cycle, do not need like this DSP to intervene, PWM peripheral hardware, by passing through that according to setup parameter the control of inverter circuit on off state is realized to the transfer control to output transient current vector automatically, makes the variation of output current trace command electric current;
The method that draws of the transient current shift factor described in step 3) is
In the definition unit interval, the displacement of current phasor is transient current shift factor, is designated as δ ic, according to step 2) the controllable current vector that draws correspondingly draws one group of definition about transient current shift factor
δ ic_rp=(Ve1-Us)/Lc output current for just, still need forward increase time select;
δ ic_dp=-(Ve2+Us)/Lc at output current for just, select while needing forward to reduce;
δ ic_rn=-(Ve2+Us)/Lc is to bear, still need while oppositely increase to select at output current;
δ ic_dn=(Ve1-Us)/Lc output current for negative, select need oppositely reduce time;
Wherein:
Ve1=capacitor E1 terminal voltage
Ve2=capacitor E2 terminal voltage
The grid-connected point voltage of Us=
Lc=APF exports series reactance.
2. according to claim 1 based on the directly actuated novel pulse width modulation electrical current tracking and controlling method of transient current, characterized by further comprising the control step of frequency multiplication PWM.
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 control step of described frequency multiplication PWM is in one-period, to control two described transient current shift factors alternating actions twice respectively, 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 is
The operating state 1 of inverter circuit: output current is forward, field effect transistor T1 conducting, when capacitor E1 electric discharge, establishing now capacitor E1 terminal voltage is Ve1, and grid side voltage is Us, and output current current value is ic, field effect transistor T1 ON time is Trp, can draw
Δic_rp=((Ve1-Us)/Lc)*Trp
The operating state 2 of inverter circuit: output current is that forward, field effect transistor T1 turn-off, and establishing now capacitor E2 terminal voltage is Ve2, and grid side voltage is Us, and the initial numerical value of output current is ic, and field effect transistor T1 not ON time is Tdp, can draw
Δic_dp=-((Ve2+Us)/Lc)*Tdp
The operating state 3 of inverter circuit: output current is negative sense, field effect transistor T2 conducting, capacitor E2 electric discharge, establishing now capacitor E2 terminal voltage is Ve2, and grid side voltage is Us, and the initial numerical value of output current is ic, and field effect transistor T2 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, field effect transistor T2 turn-off, and establishing now capacitor E1 terminal voltage is Ve1, and grid side voltage is Us, and the initial numerical value of output current is ic, and field effect transistor T2 not 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 pulse duration modulation method described in step 4) is
K moment actual current can obtain by real-time sampling, is designated as i (k); The k+1 moment current value of expecting is designated as i (k+1), and the definition of the transient current shift factor drawing according to step 3) is known:
When output current is timing, the service time of supposing field effect transistor T1 is t1, and the shutoff of field effect transistor T1 is t2, and 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 is when negative, the service time of suppose field effect transistor T2 is t1, and the turn-off time of field effect transistor T2 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
Realize for convenience PWM and control, consider that field effect transistor T1, field effect transistor T2 adopt the driving method of complementary conducting in inverter circuit, counting the impact of opening time delay t0 can draw
T1_on=t2-t0=(i(k+1)-i(k)-δic_rn*ts)/(δic_dn-δic_rn)-t0；
Again because: δ ic_rp=δ ic_dn=δ ic_r=(Ve1-Us)/Lc makes primary current mobile to positive axis top;
δ ic_dp=δ ic_rn=δ ic_d=-(Ve2+Us)/Lc makes primary current mobile 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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| 有源电力滤波器的一种新滞环控制方法;何易桓等;《电力电子技术》;20091031;第43卷(第10期);27-28 * |
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