CN106777624A - A kind of loop current peak value evaluation method of energy feedback unit - Google Patents

Abstract

The invention discloses a kind of loop current peak value evaluation method of energy feedback unit, the conduction mode of circuit topological structure analysis inverter current and loop current first according to energy feedback system；Using SVPWM modulation strategies, to loop current and the conduction mode deployment analysis of inverter current by taking half switch periods in the first sector as an example；The loop equation of inverter current and loop current is respectively obtained according to Kirchhoff's law；The loop equation drawn according to loop current and the analysis of inverter current commutation mode is estimated switching vector selector ON time；The last evaluation method for deriving loop current peak value with the relation of loop current commutation mode and the estimation expression formula of switching vector selector ON time according to inverter current.The present invention by providing specific energy feedback system circuit parameter, according to loop current peak value evaluation method estimation loop current peak value, then according to loop current peak value estimation result, it is considered to which appropriate loop current suppressing method obtains more preferable control performance.

Description

A kind of loop current peak value evaluation method of energy feedback unit

Technical field

The present invention relates to power electronics control technology field, more particularly to a kind of energy feedback unit loop current peak value Evaluation method.

Background technology

Increasingly highlighted as traditional fossil energy is in short supply, the problems such as environmental pollution is serious.Energy efficiency is improved, the energy is reduced Consumption has become subject under discussion more and more important on various countries' sustainable economic development road.The conventional AC frequency conversion speed-adjusting system energy Yet there is very big room for promotion in utilization rate, the consumption of motor load braking energy is to a certain degree caused by energy one way flow On constrain its development.Energy feedback system is improved by the topology to conventional AC frequency conversion speed-adjusting system, is capable of achieving energy The two-way flow of amount and unity power factor, are that frequency conversion speed-adjusting system saves energy, improve performance, carry efficient important way Footpath.

Parallel connection type energy feedback system is the improvement to traditional frequency conversion governing system, and its topological structure is at dc bus end Access energy feedback unit in parallel with AC network end.This controllable energy feedback unit in motor load consumed energy, It is typically in off position；When motor load slows down, inverter mode is operated in, by energy feedback to power network.Parallel connection type energy Amount feedback system only needs suitably to change connection access energy feedback unit, so improvement cost is relatively low.Design is in parallel During the energy feedback unit of type topological structure, the relation of feedback energy and system total power can also be considered, reduce energy The further reduces cost of capacity of feedback unit.

In parallel connection type energy feedback system, when energy feedback unit inversion regenerative electric power, energy feedback unit and frequency conversion Loop current loop can be also formed between the diode uncontrollable rectifier bridge front end of device.Loop current component can be superimposed upon energy feedback Grid-connected current harmonic wave is shown as in the inverter current of unit, therefore the presence of loop current can increase grid-connected current harmonic wave, reduce System control performance, increase switching loss, adverse effect is brought to energy feedback system.It is existing on parallel connection type energy feedback In the method for designing of system, ac filter inductance and DC flat-wave reactor value are commonly designed larger, and this to a certain extent can Suppress loop current, thus it is less for the document that loop current carries out specific research.And it is larger in energy feedback system power Occasion, inductance value designed conference influence dynamic performance, while can also bring the lifting of cost, limit energy feedback Systematic difference.

The content of the invention

In view of this, technical problem solved by the invention is the loop current peak value for providing a kind of energy feedback unit Evaluation method, on the basis of concrete analysis loop current commutation mode and current loop equation, using inverter current and circulation Relation between current commutation mode, estimates loop current peak value from the angle of switching vector selector ON time.

The present invention solves above-mentioned technical problem by the following technical programs：

A kind of loop current peak value evaluation method of energy feedback unit, comprises the following steps：

S1. circuit topological structure analysis inverter current first according to energy feedback system and the conducting side of loop current Formula；

S2. SVPWM modulation strategies are used, to loop current and inverter current by taking half switch periods in the first sector as an example Conduction mode deployment analysis, the switching vector selector state change of half switch periods is defined as 111-110-100；

S3. the loop equation of inverter current and loop current is respectively obtained according to Kirchhoff's law：

S4. and then according to the loop equation that loop current and the analysis of inverter current commutation mode draw switching vector selector is turned on Time is estimated；

S5. finally according to inverter current and the relation and the estimation table of switching vector selector ON time of loop current commutation mode The evaluation method of loop current peak value is derived up to formula.

Further, in step s 2,

When switching vector selector is 111 state, switching tube state is T₁、T₃、T₅Conducting, T₂、T₄、T₆Shut-off, in the first sector, Three-phase power grid voltage relation meets e_ga＞ e_gb＞ e_gc, A₁Point current potential is high compared with 2 points of B, C, and loop current flows through uncontrollable rectifier bridge a phases Upper pipe D_a1, respectively from the switch transistor T of b, c two-phase₃And switch transistor T₅Flow back into power network.

Further, in step s3,

In the loop of inverter current and loop current, current relationship meets：

When switching vector selector state is 111, bridge arm side voltage meets V_aN=V_bN=V_cN=u_dc, by above-mentioned current relationship point The loop equation for not bringing inverter current and loop current into can be obtained：

Inverter current and loop current conduction mode when can be similarly 110 and 100 to switching vector selector be analyzed, switch Inverter current and loop current loop equation difference when vector is 110 and 100 is as follows：

Analyzed by loop current and inverter current commutation mode, under the influence of dead-time voltage factor is not considered, circulation Electric current is identical with inverter current phase：When inverter current flows into energy feedback unit side a phases, loop current is accordingly flowed into and not controlled Diode rectifier bridge a phases；When the inverter current direction that single PWM switch periods self-energy feedback unit side flows into switches, do not control Rectifier bridge side flow into loop current direction also accordingly switch, under unit inverter mode, a phase inverter currents reach negative peak value When, a phase circulations electric current can reach positive maximum.

Further, in step s 4,

Loop equation of the inverter current when switching vector selector is 111 and 100 is shown below：

When power factor is approximately 1, a phase voltage peak points are also the peak point of a phase inverter currents, now inversion electricity It is zero that the change within 111-110-100 vector action times of stream can be approximately considered, inverter current variation delta i₁With Δ i₂It is full The following relation of foot：

Δi₁=Δ i₂

Define T_PWMIt is switch periods, then 111 vectors and 100 vector ON times meet：

Summary relational expression, can derive at voltage peak, and the ON time estimation expression formula of 100 switching vector selectors is such as Under：

Further, in step s 5,

Analyzed by the commutation mode of inverter current and loop current, when inverter current amplitude reaches peak point, circulation electricity Stream amplitude also mutually should be maximum, and at a phase line voltage peak points in the first sector, vector state change turns to 111-110- In 100 half PWM cycle, a phase circulations electric current is kept to zero in 100 switching vector selector state from maximum, according to electricity now Road equation is estimated loop current peak value；

The rate of change Δ i of loop current in 100 vector state action times₃Represent, it is contemplated that 100 vector states are acted on In time, it is linear that loop current change can be approximately considered, and ignores loop resistance effect, ring when 100 switching vector selectors are acted on Stream current loop equation is expressed as follows：

Bringing 100 vector action times estimation expression formula into above-mentioned equation can obtain：

In a phase voltages e_gaDuring for peak value, loop current also reaches peak value, and three phase network phase voltage peak value is e_peak, circulation Current peak is i_peak, PWM switching frequencies are f_pwm, loop current peak value estimation expression formula it is as follows：

Compared with prior art, technical scheme at least has the advantages that：

The loop current peak value evaluation method of energy feedback unit of the invention passes through between inverter current and loop current The relation of commutation mode, gives the evaluation method of the factor relevant with loop current peak value and loop current peak value, to reducing Energy feedback unit grid-connected current harmonic wave, design appropriate filter circuit parameter has certain reference significance.The present invention is in concrete analysis On the basis of loop current commutation mode and current loop equation, using the pass between inverter current and loop current commutation mode System, is derived from the angle of switching vector selector ON time to loop current peak value evaluation method, it is indicated that current loop ginseng Several influences to loop current, have certain directive significance to the circuit parameter design of energy feedback system.By to providing The energy feedback system circuit parameter of body, the loop current peak value evaluation method be given according to the present invention just can be evaluated whether circulation electricity Stream peak value, then according to loop current peak value estimation result, it is considered to which appropriate loop current suppressing method is preferably controlled to obtain Performance processed.

Described above is only the general introduction of technical solution of the present invention, in order to better understand technological means of the invention, And can be practiced according to the content of specification, and in order to allow the above and other objects, features and advantages of the invention can Become apparent, below in conjunction with preferred embodiment, and coordinate accompanying drawing, describe in detail as follows.

Brief description of the drawings

Fig. 1 is the circuit topological structure figure of energy feedback system.

Fig. 2 for energy feedback system circuit equivalent analysis topology diagram, represent 111 switching vector selector when loop current and The commutation mode of inverter current.

In Fig. 3 a inverter currents loop, three-phase equivalent circuit diagram during 111 vector.

In Fig. 3 b loop currents loop, three-phase equivalent circuit diagram during 111 vector.

Fig. 4 is the curent change schematic diagram in half PWM switch periods at voltage peak

Specific embodiment

The invention will now be described in detail with reference to the accompanying drawings, its as part of this specification, and this is illustrated by embodiment The principle of invention, other aspects of the present invention, feature and its advantage will be become apparent by the detailed description.Joined According to accompanying drawing in, same or analogous part is represented using identical drawing reference numeral in different figures.

As Figure 1-4, the loop current peak value evaluation method of a kind of energy feedback unit provided in an embodiment of the present invention, Inverter current and loop current conduction mode analysis including energy feedback system, the estimation of switching vector selector ON time and circulation electricity Stream peak value is estimated, comprised the following steps：

S1. circuit topological structure analysis inverter current first according to energy feedback system and the conducting side of loop current Formula, the circuit topological structure of energy feedback system as shown in Figure 1, is analyzing the conduction mode of inverter current and loop current When, motor load and inversion module can be equivalent to DC bus-bar voltage, now system equivalent analysis topology such as accompanying drawing 2.Conduction mode of the inverter current with loop current and switching vector selector state and loop current potential difference correlation, the energy that the present invention is discussed Amount feedback unit uses seven segmentations tradition SVPWM modulation strategies.

S2. SVPWM modulation strategies are used, to loop current and inverter current by taking half switch periods in the first sector as an example Conduction mode deployment analysis, the switching vector selector state change of half switch periods is defined as 111-110-100.Switching vector selector is During 111 state, switching tube state is T₁、T₃、T₅Conducting, T₂、T₄、T₆Shut-off, in the first sector, three-phase power grid voltage relation expires Sufficient e_ga＞ e_gb＞ e_gc, therefore A₁Point current potential is high compared with 2 points of B, C, and loop current flows through pipe D in uncontrollable rectifier bridge a phases_a1, respectively from The switch transistor T of b, c two-phase₃And switch transistor T₅Flow back into power network.A point current potentials are high compared with 2 points of B, C, so inverter current can flow through it is continuous Stream diode D₁, respectively from the switch transistor T of b, c two-phase₃And switch transistor T₅Flow back into the loop of power network loop current and inverter current Respectively as shown in solid line and dotted line in accompanying drawing 2.Ignore the conduction voltage drop of diode, the equivalent circuit diagram in three-phase loop now As shown in accompanying drawing 3a and Fig. 3 b.

S3. the loop equation of inverter current and loop current is respectively obtained according to Kirchhoff's law：

In the loop of inverter current and loop current, current relationship meets：

When switching vector selector state is 111, bridge arm side voltage meets V_aN=V_bN=V_cN=u_dc, by above-mentioned current relationship point The loop equation for not bringing inverter current and loop current into can be obtained：

Inverter current and loop current conduction mode when can be similarly 110 and 100 to switching vector selector be analyzed, switch Inverter current and loop current loop equation difference when vector is 110 and 100 is as follows：

By loop current and the analysis of inverter current commutation mode it can be found that not considering the shadow of the non-linear factors such as dead band Under sound, loop current is identical with inverter current phase.When inverter current flows into energy feedback unit side a phases, loop current phase Should flow into and not control diode rectifier bridge a phases；Cut in the inverter current direction that single PWM switch periods self-energy feedback unit side flows into When changing, the loop current direction that uncontrollable rectifier bridge side flows into also accordingly switches.Under unit inverter mode, a phase inverter currents reach During negative peak value, a phase circulations electric current can reach positive maximum.

S4. and then according to the loop equation that loop current and the analysis of inverter current commutation mode draw switching vector selector is turned on Time is estimated；In the first sector, by taking a phases as an example, a phases phase voltage is in when near peak value, space voltage vector rotation Angle θ is close to zero, and 100 account for leading role in effective voltage vector.Ideally, at line voltage peak value, 110 vectors are led The logical time is zero, now the conducting of the vector two states of only 111 vector 100.It can be assumed that now inverter current only has Two kinds of variable conditions of raising and lowering, inverter current changes as shown in accompanying drawing four.Switching vector selector 111 is from time point t₀Start to make With now inverter current is in ascent stage；t₁Moment, switching vector selector 100 starts effect, and inverter current is in the decline stage, To t₂Moment is switched to next on off state.In 111 vector state action times, the incrementss Δ i of inverter current₁Represent, Duration uses Δ T₁Represent；In 100 vector state action times, the decrement Δ i of inverter current₂Represent, the duration is used ΔT₂Represent.

Such as accompanying drawing 4, loop equation of the inverter current when switching vector selector is 111 and 100 is shown below：

When power factor is approximately 1, a phase voltage peak points are also the peak point of a phase inverter currents, now inversion electricity It is zero that the change within 111-110-100 vector action times of stream can be approximately considered, inverter current variation delta i₁With Δ i₂It is full The following relation of foot：

Δi₁=Δ i₂

Define T_PWMIt is switch periods, then 111 vectors and 100 vector ON times meet：

Summary relational expression, can derive at voltage peak, and the ON time estimation expression formula of 100 switching vector selectors is such as Under：

S5. finally according to inverter current and the relation and the estimation table of switching vector selector ON time of loop current commutation mode The evaluation method of loop current peak value is derived up to formula.Analyzed by the commutation mode of inverter current and loop current, in inverter current When amplitude reaches peak point, loop current amplitude also mutually should be maximum, a phase line voltage peak points in the first sector Place, during vector state becomes and turns to half PWM cycle of 111-110-100, a phase circulations electric current in 100 switching vector selector state from Maximum is kept to zero, and loop current peak value is estimated according to circuit equation now；

The rate of change Δ i of loop current in 100 vector state action times₃Represent, it is contemplated that 100 vector states are acted on In time, it is linear that loop current change can be approximately considered, and ignores loop resistance effect, ring when 100 switching vector selectors are acted on Stream current loop equation is expressed as follows：

Bringing 100 vector action times estimation expression formula into above-mentioned equation can obtain：

In a phase voltages e_gaDuring for peak value, loop current also reaches peak value, and three phase network phase voltage peak value is e_peak, circulation Current peak is i_peak, PWM switching frequencies are f_pwm, loop current peak value estimation expression formula it is as follows：

The loop current peak value evaluation method of energy feedback unit of the invention passes through between inverter current and loop current The relation of commutation mode, gives the evaluation method of the factor relevant with loop current peak value and loop current peak value, to reducing Energy feedback unit grid-connected current harmonic wave, design appropriate filter circuit parameter has certain reference significance.The present invention is in concrete analysis On the basis of loop current commutation mode and current loop equation, using the pass between inverter current and loop current commutation mode System, is derived from the angle of switching vector selector ON time to loop current peak value evaluation method, it is indicated that current loop ginseng Several influences to loop current, have certain directive significance to the circuit parameter design of energy feedback system.By to providing The energy feedback system circuit parameter of body, the loop current peak value evaluation method be given according to the present invention just can be evaluated whether circulation electricity Stream peak value, then according to loop current peak value estimation result, it is considered to which appropriate loop current suppressing method is preferably controlled to obtain Performance processed.

The above is the preferred embodiment of the present invention, it is noted that for those skilled in the art For, under the premise without departing from the principles of the invention, some improvements and modifications can also be made, these improvements and modifications are also considered as Protection scope of the present invention.

Claims (5)

1. the loop current peak value evaluation method of a kind of energy feedback unit, it is characterised in that comprise the following steps：

S1. circuit topological structure analysis inverter current and the conduction mode of loop current first according to energy feedback system；

S2. SVPWM modulation strategies are used, loop current and inverter current are led by taking half switch periods in the first sector as an example Logical mode deployment analysis, the switching vector selector state change of half switch periods is defined as 111-110-100；

S3. the loop equation of inverter current and loop current is respectively obtained according to Kirchhoff's law：

$\left\{\begin{array}{c}{V}_{aN}-V_{bN}=e_{ga}-(e_{gb}+L_m\frac{{\mathrm{di}}_{bloop}^{\′}}{dt}+i_{bloop}^{\′}R)\\ V_{aN}-V_{cN}=e_{ga}-(e_{gc}+L_m\frac{{\mathrm{di}}_{cloop}^{\′}}{dt}+i_{cloop}^{\′}R)\end{array}\right.$

$\left\{\begin{array}{c}{V}_{aN}-V_{bN}=e_{ga}+L_m\frac{{\mathrm{di}}_{ga}}{dt}+i_{ga}R-(e_{gb}+L_m\frac{{\mathrm{di}}_{gb}}{dt}+i_{gb}R)\\ V_{aN}-V_{cN}=e_{ga}+L_m\frac{{\mathrm{di}}_{ga}}{dt}+i_{ga}R-(e_{gc}+L_m\frac{{\mathrm{di}}_{gc}}{dt}+i_{gc}R)\end{array}\right.$

S4. and then according to loop current and inverter current commutation mode the loop equation for drawing is analyzed to switching vector selector ON time Estimated；

S5. finally according to inverter current and the relation and the estimation expression formula of switching vector selector ON time of loop current commutation mode Derive the evaluation method of loop current peak value.

2. the loop current peak value evaluation method of energy feedback unit according to claim 1, it is characterised in that：In step In S2,

When switching vector selector is 111 state, switching tube state is T₁、T₃、T₅Conducting, T₂、T₄、T₆Shut-off, in the first sector, three-phase Line voltage relation meets e_ga＞ e_gb＞ e_gc, A₁Point current potential is high compared with 2 points of B, C, and loop current flows through and managed in uncontrollable rectifier bridge a phases D_a1, respectively from the switch transistor T of b, c two-phase₃And switch transistor T₅Flow back into power network.

3. the loop current peak value evaluation method of energy feedback unit according to claim 1, it is characterised in that：In step In S3,

In the loop of inverter current and loop current, current relationship meets：

$\left\{\begin{array}{c}{i}_{aloop}=i_{bloop}^{\′}+i_{cloop}^{\′}\\ i_{ga}=i_{gb}+i_{gc}\end{array}\right.$

When switching vector selector state is 111, bridge arm side voltage meets V_aN=V_bN=V_cN=u_dc, by above-mentioned current relationship band respectively The loop equation for entering inverter current and loop current can be obtained：

$\left\{\begin{array}{c}3e_{ga}-i_{aloop}R=L_m\frac{{\mathrm{di}}_{aloop}}{dt}\\ e_{ga}-i_{ga}R=L_m\frac{{\mathrm{di}}_{ga}}{dt}\end{array}\right.$

Inverter current and loop current conduction mode when can be similarly 110 and 100 to switching vector selector be analyzed, switching vector selector For 110 and 100 when inverter current and loop current loop equation difference it is as follows：

$\left\{\begin{array}{c}3e_{ga}-u_{dc}-i_{aloop}R=L_m\frac{{\mathrm{di}}_{aloop}}{dt}\\ e_{ga}-\frac{u_{dc}}{3}-i_{ga}R=L_m\frac{{\mathrm{di}}_{ga}}{dt}\end{array}\right.$

$\left\{\begin{array}{c}3e_{ga}-2u_{dc}-i_{aloop}R=L_m\frac{{\mathrm{di}}_{aloop}}{dt}\\ e_{ga}-\frac{2u_{dc}}{3}-i_{ga}R=L_m\frac{{\mathrm{di}}_{ga}}{dt}\end{array}\right.$

Analyzed by loop current and inverter current commutation mode, under the influence of dead-time voltage factor is not considered, loop current It is identical with inverter current phase：When inverter current flows into energy feedback unit side a phases, loop current is accordingly flowed into and does not control two poles Pipe rectifier bridge a phases；When the inverter current direction that single PWM switch periods self-energy feedback unit side flows into switches, uncontrollable rectifier The loop current direction that bridge side flows into also accordingly switches, and under unit inverter mode, a phase inverter currents are when reaching negative peak value, a phases Loop current can reach positive maximum.

4. the loop current peak value evaluation method of the energy feedback unit according to claim, it is characterised in that in step In S4,

Loop equation of the inverter current when switching vector selector is 111 and 100 is shown below：

When power factor is approximately 1, a phase voltage peak points are also the peak point of a phase inverter currents, now inverter current It is zero that change within 111-110-100 vector action times can be approximately considered, inverter current variation delta i₁With Δ i₂Meet such as Lower relation：

Δi₁=Δ i₂

Define T_PWMIt is switch periods, then 111 vectors and 100 vector ON times meet：

${\mathrm{\ΔT}}_1+{\mathrm{\ΔT}}_2=\frac{1}{2}{T}_{PWM}$

Summary relational expression, can derive at voltage peak, and the ON time estimation expression formula of 100 switching vector selectors is as follows：

${\mathrm{\ΔT}}_2=\frac{3e_{ga}}{4v_{dc}}{T}_{PWM}.$

5. the loop current peak value evaluation method of energy feedback unit according to claim 1, it is characterised in that in step In S5,

Analyzed by the commutation mode of inverter current and loop current, when inverter current amplitude reaches peak point, loop current width Value also mutually should be maximum, and at a phase line voltage peak points in the first sector, vector state change turns to 111-110-100 Half PWM cycle in, a phase circulations electric current is kept to zero in 100 switching vector selector state from maximum, according to circuit side now Journey is estimated loop current peak value；

The rate of change Δ i of loop current in 100 vector state action times₃Represent, it is contemplated that 100 vector state action times Interior, it is linear that loop current change can be approximately considered, and ignores loop resistance effect, circulation electricity when 100 switching vector selectors are acted on Stream loop equation is expressed as follows：

$3e_{ga}-2u_{dc}=-L_m\frac{{\mathrm{\Δi}}_3}{{\mathrm{\ΔT}}_2}$

Bringing 100 vector action times estimation expression formula into above-mentioned equation can obtain：

${\mathrm{\Δi}}_3=-3e_{ga}{T}_{PWM}\frac{3e_{ga}-2v_{dc}}{4L_m{v}_{dc}}$

In a phase voltages e_gaDuring for peak value, loop current also reaches peak value, and three phase network phase voltage peak value is e_peak, loop current Peak value is i_peak, PWM switching frequencies are f_pwm, loop current peak value estimation expression formula it is as follows：

$i_{peak}=\frac{3e_{peak}}{2L_m{f}_{pwm}}(1-\frac{3e_{peak}}{2v_{dc}}).$