CN105322768A - Control apparatus for parallel power conversion systems - Google Patents

Abstract

The invention discloses a control apparatus for parallel power conversion systems. The control apparatus comprises a voltage detector, a current detector, a voltage controller, a current controller, a circular current calculator for calculating the circular current value according to the current value of a power converter, a circular current compensation calculation unit for calculating the circular current compensation amount according to an expected current instruction value, a circular current compensator for compensating the circular current value or the circular current instruction value according to the circular current compensation amount, a circular current controller for outputting a circular current inhibiting signal according to the circular current value and the compensated circular current instruction value, or the compensated circular current value and the circular current instruction value, a modulating signal generator for generating a modulation signal according to the control voltage signal and the circular current inhibiting signal, and a PWM unit for generating a switch signal according to the modulating signal. The control apparatus for the parallel power conversion systems can effectively restrain the various circular currents in the parallel power conversion systems on the premise of ensuring the controllable voltage of each power converter.

Description

The control device of parallel power transformation system

Technical field

The present invention relates to power-converting device control field, particularly relating to a kind of control device of the parallel power transformation system for being made up of multiple power converter.

Background technology

Power-converting device parallel technology expands power-converting device power, improves reliability, realizes the important technical that power-converting device power adjusts flexibly.Circulation is the problem that parallel power converting means must solve, and this makes circulation control technology become key and the core of power-converting device parallel technology.

Chinese invention patent CN200710121110.3 (applying date: 2007.08.30) is by regulating the circulation suppressed the action time of the zero vector PPP in space vector modulation (SVPWM) in the shunt circuit of back-to-back converter.But this control method only can play inhibitory action to the zero sequence circulation in back-to-back converter, is then to tackle to the circulation (IEEEPESC2008,1937-1943) of other form in back-to-back converter.

Research shows, when adopting common bus parallel power conversion control method to suppress the circulation in non-common bus parallel power converting means (i.e. back-to-back converter), because the bus in parallel power converting means is not interconnected each other, if each corresponding phase current of each rectifier of parallel power converting means is mutually the same under the control of the controller (now circulation is zero), the inevitable difference existed between the physics actual parameter of then rectifier can cause the difference between each busbar voltage can increase in time and increasing, finally cause busbar voltage out of control.Therefore, how to ensure under the prerequisite that each busbar voltage is controlled that the various circulation existed in non-common bus parallel power converting means carry out effective suppression and just become of parallel power converting means and have important technological problems to be solved.

Summary of the invention

The technical problem to be solved in the present invention is the control device proposing a kind of parallel power transformation system, and this control device can to ensure under the controlled prerequisite of each power converter voltage that the various circulation existed in parallel power transformation system effectively suppress.

For solving the problems of the technologies described above, the control device of parallel power transformation system of the present invention comprises as follows:

Voltage detector: for detecting the DC voltage of described power converter;

Current detector: for detecting the ac-side current of described power converter;

Voltage controller; DC voltage and the command value thereof of the power converter exported according to described voltage detector control, and export the expectation current instruction value corresponding to this power converter;

Current controller: the ac-side current value of power converter exported according to described current detector and the expectation current instruction value of the current controller of voltage controller output control, and export control voltage signal;

Calculation of circulating current device: the circulation value calculating corresponding power converter according to the current value of described power converter;

Modulation signal maker: the loop current suppression signal that the described control voltage signal exported according to described current controller and circulation controller export generates the modulation signal needed for PWM unit;

PWM unit: generate switching signal according to the described modulation signal that described modulation signal maker exports, for realizing opening and turning off control of the power model of the rectifier part to the described parallel power converting means of formation;

Circulation compensation calculation unit: calculate circulation compensation rate according to the described expectation current instruction value that described voltage controller exports;

Circulation compensator: described circulation value or circulation command value are compensated according to the described circulation compensation rate that described circulation compensation calculation unit exports;

Circulation controller: the described circulation value exported according to described calculation of circulating current device and the circulation command value after described circulation compensator compensates, or the described circulation value after described circulation compensator compensates and described circulation command value control, export the described loop current suppression signal needed for described modulation signal maker.

Described calculation of circulating current device calculates the described circulation value of described power converter in the following manner:

Mode 1: the difference between the current average of each phase current phase corresponding to all power converters of calculating power converter;

Mode 2: selected a certain power converter is benchmark power converter, benchmark power converter aspergillus ficuum; The calculation of circulating current mode of all the other power converters is the difference between the current value of each phase current phase corresponding to benchmark power converter of this power converter.

Described circulation compensation calculation unit calculates described circulation compensation rate in the following manner:

Mode 1: when described calculation of circulating current device calculates described circulation value according to mode 1, the expectation current instruction value corresponding to this power converter that described circulation compensation calculation unit utilizes the described voltage controller corresponding with a certain power converter to export deducts the mean value of all expectation current instruction values exported corresponding to all voltage controllers, and using the difference that obtains as the described circulation compensation rate corresponding with this power converter;

Mode 2: when described calculation of circulating current device calculates described circulation value according to mode 2, the expectation current instruction value corresponding to this power converter that described circulation compensation calculation unit utilizes the described voltage controller corresponding with non-referenced power converter to export deducts the expectation current instruction value corresponding to benchmark power converter that the described voltage controller corresponding with non-referenced power converter exports, and using the difference that obtains as the described circulation compensation rate corresponding with this power converter.

Described current value detects by the electric current of current sensing means to described power converter the testing result obtained, or current detecting result is in the result obtained after signal condition and/or coordinate transform.

The beneficial effect that the present invention can reach is:

Can ensure, under the prerequisite that each power converter DC voltage is controlled, effectively to suppress the various circulation be present in parallel power converting means.

Accompanying drawing explanation

Fig. 1 is the control object of the control device of parallel power transformation system of the present invention---a kind of structural representation of parallel power transformation system;

Fig. 2 is a kind of structural representation of the control device of parallel power transformation system of the present invention;

Fig. 3 is the another kind of structural representation of the control device of parallel power transformation system of the present invention;

Fig. 4 is the third structural representation of the control device of parallel power transformation system of the present invention;

Fig. 5 is the 4th kind of structural representation of the control device of parallel power transformation system of the present invention.

Symbol description:

1 be electrical network 2 is motor

#2 is rectification side reactor #3 is rectification side current detector

#4 is rectifier #5 is voltage detector

#6 is DC capacitor #7 is inverter

#8 is inverter side current detector #9 is inverter side reactor

Wherein, # is power converter numbering (as 12 is the rectification side reactor of No. 1 power converter, the rest may be inferred).

Embodiment

Be illustrated in figure 1 the control object of the control device of parallel power transformation system of the present invention---a kind of structural representation of parallel power transformation system, visible, parallel power converting means is formed in parallel by the power converter (being PWM rectifier) that n (n >=2) individual DC side is separate herein, and its DC side is connected with respective load, be be connected with same motor further after out put reactor through respective inverter herein, thus form the back-to-back converter system of a non-common bus on the whole.This system comprise further rectification side reactor #2, rectifier #4, for detect DC bus-bar voltage voltage detector #5, for the smoothing DC capacitor #6 of direct voltage, inverter #7 and inverter side reactor #9 for by DC inverter being alternating current, the power converter one end after parallel connection is connected with electrical network 1, the other end is connected with load (as: motor 2).In addition, for the needs controlled, parallel power converting means also comprises the rectification side current detector #3 of the ac-side current for detecting rectifier #4 and the inverter side current detector #8 for the ac-side current that detects inverter #7.

Embodiment 1

The control device of parallel power transformation system of the present invention exports according to each PWM rectifier DC voltage value and each PWM rectifier current value the switch module be used for forming each PWM rectifier and opens and the switching signal turned off needed for control.

For the PWM rectifier that the sequence number in Fig. 1 is k, its control unit structure as shown in Figure 2, mainly comprises: voltage detector, for detecting the DC voltage of described PWM rectifier; Current detector, for detecting the ac-side current of described PWM rectifier; Voltage controller, DC voltage and the command value thereof of the PWM rectifier exported according to described voltage detector control, the expectation current instruction value of output current controller; Current controller, controls according to the ac-side current value of described PWM rectifier and command value thereof, exports control voltage signal; Calculation of circulating current device, calculates the circulation value of corresponding AC-DC-AC power converter according to the current value of described PWM rectifier; Circulation compensation calculation unit, calculates circulation compensation rate according to the described expectation current instruction value that described voltage controller exports; Circulation compensator, compensates described circulation value or described circulation command value according to the described circulation compensation rate that described circulation compensation calculation unit exports; Circulation controller, controls according to the described circulation value after described circulation compensator compensates and described circulation command value, exports the described loop current suppression signal needed for described modulation signal maker; Modulation signal maker, the loop current suppression signal that the described control voltage signal exported according to described current controller and circulation controller export generates the modulation signal needed for described PWM unit; PWM unit, generates switching signal according to the described modulation signal that described modulation signal maker exports, for realizing opening and turning off control the power model of PWM rectifier.

The course of work is: voltage controller is the DC voltage detected value V of the PWM rectifier of k according to sequence number _dckand command value V _dck ^*carry out voltage control, export the expectation current instruction value i that sequence number is the PWM rectifier of k _reck ^*, current controller is the current value i of the PWM rectifier of k according to sequence number _reckand expect current instruction value i _reck ^*carry out Current Control, export control voltage signal u _recvk; Calculation of circulating current device is according to the current value i of each PWM rectifier _recli _recn(n is PWM rectifier quantity in parallel-current converting means) calculates the circulation value i that sequence number is the PWM rectifier of k _reccrk0; The expectation current instruction value i that circulation compensation calculation unit exports according to the voltage controller of each PWM rectifier _recl ^*i _recn ^*calculate the circulation compensation rate Δ i that sequence number is the PWM rectifier of k _reccrk; The circulation value i that circulation compensator exports according to calculation of circulating current device _reccrk0with the circulation compensation rate Δ i that circulation compensation calculation unit exports _reccrkcalculate the circulation value i after compensating that sequence number is the PWM rectifier of k _reccrk; The circulation value i after compensating that circulation controller exports according to circulation compensator _reccrkwith the circulation command value i that sequence number is the PWM rectifier of k _reccrk ^*(being usually set to zero) controls circulation, exports loop current suppression signal u _reccrk; The loop current suppression signal u that modulation signal maker exports according to circulation controller _reccrkwith the control voltage signal u that current controller exports _recvkgenerate modulation signal u _reck; Sequence number is the modulation signal u that the PWM unit of the PWM rectifier of k exports according to modulation signal maker _reckmodulate, output switching signal, give after the necessary process such as suitable isolation, driving, amplification and form the switch module that sequence number is the PWM rectifier of k, thus realize being opening of the switch module of the PWM rectifier of k to formation sequence number and turning off control.

In the above description, described current value detects by the electric current of current sensing means to described power converter the testing result obtained, or current detecting result is in the result obtained after signal condition and/or coordinate transform.

In above-mentioned explanation, calculation of circulating current device calculates the described circulation value of described power converter (PWM rectifier namely in the present embodiment) in the following manner:

Mode 1: the difference between the current average of each phase current phase corresponding to all power converters of calculating power converter, namely

$i_{\mathrm{rec}\_\mathrm{crk}0}=i_{\mathrm{reck}}-\frac{1}{n}\×\underset{m=1}{\overset{n}{\mathrm{\Σ}}}{i}_{\mathrm{recm}}$

Wherein, i _{rec_crk0}the circulation that to be sequence number be before the compensation of the PWM rectifier of k, i _reckand i _recmthe current value of the PWM rectifier of k and m that to be sequence number be respectively, n is the quantity of power converter in parallel power transformation system.

Mode 2: selected a certain power converter is benchmark power converter, benchmark power converter aspergillus ficuum; The calculation of circulating current mode of all the other non-referenced power converters is the difference between the current value of each phase current phase corresponding to benchmark power converter of this power converter, that is:

Setting sequence number is the power converter at the PWM rectifier place of j is benchmark power converter, and be the PWM rectifier of k for controlling sequence number, its calculation of circulating current method is: as k=j, circulation i _{rec_crk0}=0; As k ≠ j, circulation i _{rec_crk0}=i _reck-i _recj.

In above-mentioned explanation, circulation compensation calculation unit calculates described circulation compensation rate in the following manner:

Mode 1: when described calculation of circulating current device in the manner described above 1 calculate described circulation value time, the mean value deducting all expectation current instruction values exported corresponding to all voltage controllers corresponding to the expectation current instruction value of this power converter that circulation compensation calculation unit utilizes the described voltage controller corresponding with a certain power converter to export, and using the difference that obtains as the described circulation compensation rate corresponding with this power converter;

Mode 2: when described calculation of circulating current device in the manner described above 2 calculate described circulation value time, what circulation compensation calculation unit utilized the described voltage controller corresponding with non-referenced power converter to export deducts corresponding to the expectation current instruction value of this power converter the expectation current instruction value corresponding to benchmark power converter that the described voltage controller corresponding with non-referenced power converter export, and using the difference that obtains as the described circulation compensation rate corresponding with this power converter.

In above-mentioned explanation, circulation compensator is as follows to the circulation value i that calculation of circulating current device exports _reccrk0compensate:

By the circulation value i that calculation of circulating current device exports _reccrk0the sequence number deducting the output of circulation compensation calculation unit is the circulation compensation rate Δ i of the power converter of k _reccrk, the difference obtained is the circulation value i after compensation _reccrk.

In addition, it should be added that:

1, the described current value in above-mentioned explanation detects by the electric current of current sensing means to described power converter the testing result obtained, or current detecting result is in the result obtained after suitably processing (as signal condition, coordinate transform etc.).For the current i in Fig. 1 _k(k=1, n) can be the current detection value i of power converter _kj(j=a, b, c), i.e. the AC three-phase current detection value of PWM rectifier or the current detection value after signal condition also can be i _kj(j=d, q) or i _kj(j=α, β), the current value namely obtained after dq coordinate transform or α β coordinate transform.

2, circulation controller, voltage controller and current controller, can be the simple PI controller, predictive controller etc. in corresponding coordinate system, also can be comparatively complicated controller, as: the vector controller, Direct Torque Controller etc. of motor speed regulation system.Obviously, for PMSM governing system, current controller can be then the PMSM vector control system comprising permanent magnet flux linkage, dq shaft current decoupling compensation item; For PWM rectifier, current controller can be comprise line voltage vector e _dand e _q, dq shaft current decoupling compensation item at interior PWM rectifier vector control system, see the Control System Design of 3.2.1 current inner loop and Fig. 3-30 of PWM rectifier and control (Zhang Chongwei, Zhang Xing, China Machine Press, 2003) thereof.

Embodiment 2

The present embodiment structure as shown in Figure 3 can be found out, the present embodiment is similar to embodiment 1, is only illustrated with regard to the difference of the two below.

In the present embodiment, circulation controller, controls according to described circulation value and the described circulation command value after described circulation compensator compensates, exports the described loop current suppression signal needed for described modulation signal maker.

In the course of work, the expectation current instruction value i that circulation compensation calculation unit exports according to the voltage controller of each PWM rectifier _recl ^*i _recn ^*calculate the expectation circulation compensation rate Δ i that sequence number is the PWM rectifier of k _reccrk ^*; The expectation circulation compensation rate Δ i that circulation compensator exports according to circulation compensation calculation unit _reccrk ^*with the circulation command value i that sequence number is the PWM rectifier of k _reccrk0 ^*(being usually set to zero) calculates the circulation command value i through compensating that sequence number is the PWM rectifier of k _reccrk ^*; Circulation controller is the circulation command value i after compensating of the PWM rectifier of k according to the sequence number that circulation compensator exports _reccrk ^*with the circulation value i that the sequence number of calculation of circulating current device output is the PWM rectifier of k _reccrkcirculation is controlled, exports loop current suppression signal u _reccrk.

In above-mentioned explanation, circulation compensator is the circulation command value i of the PWM rectifier of k as follows to sequence number _reccrk0 ^*compensate:

Be the circulation command value i of the PWM rectifier of k by sequence number _reccrk0 ^*add that sequence number that circulation compensation calculation unit exports is the circulation compensation rate Δ i of the PWM rectifier of k _reccrk, that obtain and after being compensation sequence number is the circulation command value i of the PWM rectifier of k _reccrk ^*.

Embodiment 3

As shown in Figure 4, the present embodiment is similar to embodiment 1, and difference is to add compensation correction unit between circulation compensation calculation unit and circulation compensator.The described circulation compensation rate that compensation correction unit is used for described circulation compensation calculation unit exports corrects, and the circulation compensation rate after output calibration.Circulation compensation rate after the correction that described circulation compensator exports according to described compensation correction unit compensates described circulation value or described circulation command value.The initial circulation compensation rate Δ i that circulation compensation calculation unit exports _reccrk0as compensation correction unit input and be sent to compensation correction unit, the described circulation compensation rate Δ i that described compensation correction unit exports according to described circulation compensation calculation unit _reccrk0, the described expectation current instruction value i that exports of described voltage controller _reck ^*or the current value i of described power pack _reckand the maximum limit flow valuve i that described AC-DC-AC power converter allows _reckmaxto the initial circulation compensation rate Δ i that described circulation compensation calculation unit exports _{rec_crk0}correct, the circulation compensation rate Δ i after output calibration _{rec_crk}.

Compensation correction unit is herein for avoiding power converter to occur overcurrent, needs satisfied following condition for this reason:

$i_{\mathrm{reck}\max }-(i_{\mathrm{reck}}^{*}+i_{\mathrm{rec}\_\mathrm{crk}})\≥\mathrm{\α}$ Formula 1

In formula, α >=0 is threshold value.

Can be obtained by formula 1

$i_{\mathrm{reck}}^{*}+i_{\mathrm{rec}\_\mathrm{crk}}\≤i_{\mathrm{reck}\max }-\mathrm{\α}$ Formula 2

Namely

$i_{\mathrm{rec}\_\mathrm{crk}}\≤i_{\mathrm{reck}\max }-\mathrm{\α}-i_{\mathrm{reck}}^{*}$ Formula 3

Because circulation compensator is the circulation value i exported by calculation of circulating current device _{rec_crk0}deduct the circulation compensation rate Δ i after the correction of described compensation correction unit output _{rec_crk}and using obtained difference as the circulation value after compensation, then have

$i_{\mathrm{rec}\_\mathrm{crk}0}-{\mathrm{\Δi}}_{\mathrm{rec}\_\mathrm{crk}}\≤i_{\mathrm{reck}\max }-\mathrm{\α}-i_{\mathrm{reck}}^{*}$

Can obtain through arranging:

${\mathrm{\Δi}}_{\mathrm{rec}\_\mathrm{crk}}\≥i_{\mathrm{rec}\_\mathrm{crk}0}-i_{\mathrm{reck}\max }+\mathrm{\α}+i_{\mathrm{reck}}^{*}$ Formula 4

Obviously, as long as meet formula 4, power converter can be avoided to occur overcurrent.

Therefore, described compensation correction unit can correct the described circulation compensation rate that described circulation compensation calculation unit exports according to following rule

${\mathrm{\Δi}}_{\mathrm{rec}\_\mathrm{crk}}=i_{\mathrm{rec}\_\mathrm{crk}0}-i_{\mathrm{reck}\max }+\mathrm{\α}+i_{\mathrm{reck}}^{*}$ Formula 5

In fact, the condition of overcurrent can also be changed to avoid power converter to occur:

I _reckmax-(i _reck+ i _{rec_crk})>=α formula 6

Current instruction value by power converter is changed to the current value of power converter.

Copy above-mentioned derivation, can following formula be obtained

Δ i _{rec_crk}>=i _{rec_crk0}-i _reckmax+ α+i _reckformula 7

Visible, described compensation correction unit can also correct the described circulation compensation rate that described circulation compensation calculation unit exports according to following rule:

Δ i _{rec_crk}=i _{rec_crk0}-i _reckmax+ α+i _reckformula 8

Embodiment 4

As shown in Figure 5, the present embodiment is similar to embodiment 2, and difference is to add compensation correction unit between circulation compensation calculation unit and circulation compensator.The described circulation compensation rate that compensation correction unit is used for described circulation compensation calculation unit exports corrects, and the circulation compensation rate after output calibration.Circulation compensation rate after the correction that described circulation compensator exports according to described compensation correction unit compensates described circulation value or described circulation command value.The initial expectation circulation compensation rate Δ i that circulation compensation calculation unit exports _reccrk0 ^*as compensation correction unit input and be sent to compensation correction unit, the initial expectation circulation compensation rate Δ i that described compensation correction unit exports according to described circulation compensation calculation unit _reccrk0 ^*, the described expectation current instruction value i that exports of described voltage controller _reck ^*or the current value i of described power pack _reckand the maximum limit flow valuve i that described AC-DC-AC power converter allows _reckmaxthe described circulation compensation rate that described circulation compensation calculation unit exports is corrected.

Compensation correction unit is herein for avoiding power converter to occur overcurrent equally, need meet the condition of formula 1 equally.

Assuming that under the control action of circulation controller, the circulation value i that calculation of circulating current device exports _reckwith the circulation command value i that the sequence number after circulation compensator compensates is the rectifier of k _reccrk ^*approximately equal, then have

formula 9

Namely

formula 10

Because circulation compensator is by initial circulation command value add the described circulation compensation rate after described compensation correction unit corrects and using obtained and as the circulation command value after compensating therefore

$i_{\mathrm{rec}\_\mathrm{crk}0}^{*}+{\mathrm{\Δi}}_{\mathrm{rec}\_\mathrm{crk}}^{*}\≤i_{\mathrm{reck}\max }-\mathrm{\α}-i_{\mathrm{reck}}^{*}$ Formula 11

Namely

${\mathrm{\Δi}}_{\mathrm{rec}\_\mathrm{crk}}^{*}\≤i_{\mathrm{reck}\max }-\mathrm{\α}-i_{\mathrm{reck}}^{*}-i_{\mathrm{rec}\_\mathrm{crk}0}^{*}$ Formula 12

Obviously, as long as meet formula 12, power converter can be avoided to occur overcurrent.

Therefore, described compensation correction unit can correct the described circulation compensation rate that described circulation compensation calculation unit exports according to following rule:

${\mathrm{\Δi}}_{\mathrm{rec}\_\mathrm{crk}}^{*}=i_{\mathrm{reck}\max }-\mathrm{\α}-i_{\mathrm{reck}}^{*}-i_{\mathrm{rec}\_\mathrm{crk}0}^{*}$ Formula 13

In fact, the condition of overcurrent can also be changed to avoid power converter to occur:

I _reckmax-(i _reck+ i _{rec_crk})>=α formula 14

Current instruction value by power converter is changed to the current value of power converter.

Copy above-mentioned derivation, can following formula be obtained

${\mathrm{\Δi}}_{\mathrm{rec}\_\mathrm{crk}}^{*}\≤i_{\mathrm{reck}\max }-\mathrm{\α}-i_{\mathrm{reck}}-i_{\mathrm{rec}\_\mathrm{crk}0}^{*}$ Formula 15

Visible, described compensation correction unit can also correct the described circulation compensation rate that described circulation compensation calculation unit exports according to following rule:

${\mathrm{\Δi}}_{\mathrm{rec}\_\mathrm{crk}}^{*}=i_{\mathrm{reck}\max }-\mathrm{\α}-i_{\mathrm{reck}}-i_{\mathrm{rec}\_\mathrm{crk}0}^{*}$ Formula 16.

Claims (13)

1. a control device for parallel power transformation system, described parallel power transformation system is formed in parallel by n power converter, wherein n >=2; Described control device comprises:

Voltage detector: for detecting the DC voltage of described power converter;

Current detector: for detecting the ac-side current of described power converter;

Voltage controller: DC voltage and the command value thereof of the power converter exported according to described voltage detector control, the expectation current instruction value of output current controller;

Current controller: the ac-side current value of power converter exported according to described current detector and the expectation current instruction value of the current controller of voltage controller output control, and export control voltage signal;

Calculation of circulating current device: the circulation value calculating corresponding power converter according to the current value of described power converter;

Modulation signal maker: the loop current suppression signal that the described control voltage signal exported according to described current controller and circulation controller export generates the modulation signal needed for PWM unit;

PWM unit: generate switching signal according to the described modulation signal that described modulation signal maker exports, for realizing opening and turning off control the power model forming described parallel power transformation system; It is characterized in that, also comprise:

Circulation compensation calculation unit: calculate circulation compensation rate according to the described expectation current instruction value that described voltage controller exports;

Circulation compensator: described circulation value is compensated according to the described circulation compensation rate that described circulation compensation calculation unit exports;

Circulation controller: control according to the circulation value after described circulation compensator compensates and circulation command value, exports the described loop current suppression signal needed for described modulation signal maker;

Or, circulation compensator: circulation command value is compensated according to the described circulation compensation rate that described circulation compensation calculation unit exports;

Circulation controller: the described circulation value exported according to described calculation of circulating current device and the circulation command value after described circulation compensator compensates control, and export the described loop current suppression signal needed for described modulation signal maker.

2. the control device of parallel power transformation system according to claim 1, is characterized in that: described control device also comprises:

Compensation correction unit: the described circulation compensation rate for exporting described circulation compensation calculation unit corrects, the circulation compensation rate after output calibration;

Circulation compensation rate after the correction that described circulation compensator exports according to described compensation correction unit compensates described circulation value or described circulation command value.

3. the control device of parallel power transformation system according to claim 2, is characterized in that: at least one item in the maximum limit flow valuve that the current value of the described expectation current instruction value that the initial circulation compensation rate that described compensation correction unit exports according to described circulation compensation calculation unit, described voltage controller export or described power pack and described power converter allow corrects the initial circulation compensation rate that described circulation compensation calculation unit exports.

4., according to the control device of the parallel power transformation system in claims 1 to 3 described in any one, it is characterized in that:

Described calculation of circulating current device calculates the difference between the current average of each phase current phase corresponding to all power converters of power converter, and using the described circulation value of result of calculation as described power converter, computing formula is as follows:

$i_{\mathrm{rec}\_\mathrm{crk}0}=i_{\mathrm{reck}}-\frac{1}{n}\×\underset{m=1}{\overset{n}{\mathrm{\Σ}}}{i}_{\mathrm{recm}}$

Wherein, i _{rec_crk0}the circulation value that to be sequence number be before the compensation of the power converter of k,

I _reckand i _recmthe current value of to be sequence number be respectively the power converter of k and m,

N is the quantity of power converter in parallel power transformation system, wherein n >=2.

5. the control device of parallel power transformation system according to claim 4, it is characterized in that: the expectation current instruction value corresponding to this power converter that described circulation compensation calculation unit utilizes the described voltage controller corresponding with a certain power converter to export deducts the mean value of all expectation current instruction values that all voltage controllers export, and using the difference that obtains as the circulation compensation rate corresponding with this power converter or initial circulation compensation rate.

6. the control device of parallel power transformation system according to claim 5, it is characterized in that: described compensation correction unit corrects the described initial circulation compensation rate that described circulation compensation calculation unit exports according to following rule, exports described circulation compensation rate:

${\mathrm{\Δi}}_{\mathrm{rec}\_\mathrm{crk}}=i_{\mathrm{rec}\_\mathrm{crk}0}-i_{\mathrm{reck}\max }+\mathrm{\α}+i_{\mathrm{reck}}^{*}$

Or

Δi _{rec_crk}＝i _{rec_crk0}-i _reckmax+α+i _reck

Wherein, Δ i _reccrkfor the circulation compensation rate that sequence number is the power converter of k;

I _{rec_crk0}for the circulation value that sequence number is before the compensation of the power converter of k;

I _reckmaxfor the maximum limit flow valuve that power converter allows;

I _reck ^*for the expectation current instruction value that sequence number is the power converter of k;

I _reckit is the current value of the power converter of k for sequence number;

α is threshold value, and α >=0.

7. the control device of parallel power transformation system according to claim 5, it is characterized in that: described circulation compensator to the compensation method of circulation value is: the circulation value that described calculation of circulating current device exports is deducted the circulation compensation rate that described circulation compensation calculation unit exports, the difference obtained is the circulation value after compensation.

8. the control device of parallel power transformation system according to claim 6, it is characterized in that: described circulation compensator to the compensation method of circulation value is: the circulation value that described calculation of circulating current device exports is deducted the described circulation compensation rate after described compensation correction unit corrects, and the difference obtained is the circulation value after compensation.

9. according to the control device of the parallel power transformation system in claims 1 to 3 described in any one, it is characterized in that: a certain power converter selected by described calculation of circulating current device is benchmark power converter, then the circulation perseverance of benchmark power converter is zero; The circulation of all the other non-referenced power converters is the difference between the current value of each phase current phase corresponding to benchmark power converter of this power converter.

10. the control device of parallel power transformation system according to claim 9, it is characterized in that: the expectation current instruction value corresponding to this power converter that described circulation compensation calculation unit utilizes the described voltage controller corresponding with non-referenced power converter to export deducts the expectation current instruction value corresponding to benchmark power converter that the described voltage controller corresponding with non-referenced power converter exports, and using the difference that obtains as the described circulation compensation rate corresponding with this power converter or initial circulation compensation rate.

The control device of 11. parallel power transformation systems according to claim 10, is characterized in that: described compensation correction unit corrects the described circulation compensation rate that described circulation compensation calculation unit exports according to following rule:

${\mathrm{\Δi}}_{\mathrm{rec}\_\mathrm{crk}}^{*}=i_{\mathrm{reck}\max }-\mathrm{\α}-i_{\mathrm{reck}}^{*}-i_{\mathrm{rec}\_\mathrm{crk}0}^{*}$

Or

${\mathrm{\Δi}}_{\mathrm{rec}\_\mathrm{crk}}^{*}=i_{\mathrm{reck}\max }-\mathrm{\α}-i_{\mathrm{reck}}-i_{\mathrm{rec}\_\mathrm{crk}0}^{*}$

Wherein, Δ i _reccrk ^*for the expectation circulation compensation rate that sequence number is the power converter of k;

I _reckmaxfor the maximum limit flow valuve that power converter allows;

I _reck ^*for the expectation current instruction value that sequence number is the power converter of k;

I _reckit is the current value of the power converter of k for sequence number;

I _reccrk0 ^*for the circulation command value that sequence number is the power converter of k;

α is threshold value, and α >=0.

12. the control device of parallel power transformation system according to claim 10, it is characterized in that: described circulation compensator to the compensation method of circulation command value is: circulation command value is added the circulation compensation rate that described circulation compensation calculation unit exports, obtain and be the circulation command value after compensation.

The control device of 13. parallel power transformation systems according to claim 11, it is characterized in that: described circulation compensator to the compensation method of circulation command value is: initial circulation command value is added the described circulation compensation rate after described compensation correction unit corrects, obtain and be the circulation command value after compensation.