CN104617593B - Inverse direct power control method of grid connection converter - Google Patents

Abstract

The invention discloses an inverse direct power control method of a grid connection converter. According to the method, a reverse algorithm is combined with a DPC (Dynamic Power Control) technology; firstly an active power reference value and a change rate thereof are obtained through a voltage outer loop reverse controller and then input into a power inner ring reverse controller together with a passive power reference value, so a voltage reference value output by the grid connection converter can be calculated, and a switch signal is obtained through modulation of a SVPWM (Space Vector Pulse Width Modulation) module. The entire control process is performed in a static coordinate system without changing a rotary coordinate; only three adjustable parameters are required to be adjusted to realize progressive tracking of voltage of a direct current bus of the converter, meanwhile effective control of active and passive power and quick response of the system are realized, and the control structure is extremely concise. The current harmonic and the power fluctuation can be reduced while the superior dynamic performance of the conventional DPC is inherited, so the voltage of the direct current bus is more stable, constant switching frequency is obtained, and good stable and dynamic performance is realized.

Description

A kind of the counter of grid-connection converter pushes away direct Power Control method

Technical field

The invention belongs to power equipment control technical field, and in particular to a kind of the counter of grid-connection converter pushes away Direct Power control Method processed.

Background technology

With the enhancing increasingly sharpened with people's environmental consciousness of energy crisis, wind-power electricity generation, photovoltaic generation etc. it is renewable Energy exploitation and application and distributed generation technology and high voltage dc transmission technology (HVDC) have obtained unprecedented development.Voltage-type Grid-connection converter has the advantages such as preferable input-output characteristic, active power and reactive power independent regulation because of which, extensive Apply in the field such as regenerative resource distributed power generation and D.C. high voltage transmission, which also has very in intelligent power grid technology Important effect and status.

Vector controlled (VC) and direct Power Control (DPC) are always the control strategy of grid-connection converter main flow.Vector control System is capable of achieving the independent regulation of active power and reactive power, obtains good steady-state behaviour, but needs complex synchronization The phase information of fast rotating coordinate transformation and line voltage, the parameter tuning of pi regulator are complicated, and dynamic property is slightly worse.Traditional base In switch list direct Power Control (LUT-DPC) without the need for synchronous speed rotating coordinate transformation, control structure is simple, dynamic response Hurry up, but stagnant chain rate need to be carried out compared with judging with Stator flux linkage sectors, system power fluctuation is larger, and the steady-state behaviour of the method has much room for improvement. Based on PI controllers and the DPC of space vector modulation (SVM), less power swing and constant switching frequency, but PI can be obtained The introducing of controller makes which there are problems that and VC identicals, in addition, this method is higher to the parameter dependency degree in mathematical model, Thus robustness is not strong.Within a sampling time select the prediction direct Power Control (P-DPC) of three vectors obtain Preferable stable state and dynamic property are obtained, and switching frequency is constant, but need to calculate the action time of three vectors, operand in real time Larger, vector selects more complicated.For problem above, it is further to improve system control performance, the counter of grid-connection converter is pushed away The further investigation that direct Power Control method is carried out has important practical significance.

The content of the invention

For the above-mentioned technical problem existing for prior art, the invention provides a kind of the counter of grid-connection converter pushes away directly Poewr control method, need not increase additional hardware, and control structure very simple, can reach preferable dynamic property and stable state Precision.

A kind of the counter of grid-connection converter pushes away direct Power Control method, comprises the steps：

(1) gather three-phase power grid voltage U_gabc, three phase network electric current I_gabc, grid-connection converter DC bus-bar voltage V_dcWith DC side load current I_load；

(2) three-phase power grid voltage U is detected using phaselocked loop_gabcAngular frequency_g；

(3) respectively to three-phase power grid voltage U_gabcWith three phase network electric current I_gabcClark conversion is carried out, static alpha-beta is obtained and is sat Line voltage vector U under mark system_gαβWith power network current vector I_gαβ；

(4) according to described line voltage vector U_gαβWith power network current vector I_gαβ, calculate grid-connection converter output Active-power P_gAnd reactive power Q_g；

(5) according to described DC bus-bar voltage V_dc, given DC bus-bar voltage reference value V_dc ^ref, direct current lateral load Electric current I_loadAnd active-power P_g, active power reference value P is calculated by the anti-control algolithm that pushes away of outer voltage_g ^refWith it is active Value and power reference rate of change dP_g ^ref/dt；

(6) according to described active power reference value P_g ^ref, given reactive power reference qref Q_g ^ref, active power reference Value changes rate dP_g ^ref/ dt, line voltage vector U_gαβAnd angular frequency_g, to described active-power P_gAnd reactive power Q_gCarry out Internal ring is counter to push away direct Power Control, obtains modulation voltage vector V_αβ；And then according to described modulation voltage vector V_αβPass through SVPWM (space vector pulse width modulation) technical construction obtains one group of pwm signal and grid-connection converter is controlled.

In described step (3), according to following formula to three-phase power grid voltage U_gabcCarry out Clark conversion：

Wherein：U_ga、U_gb、U_gcRespectively three-phase power grid voltage U_gabcPhase voltage on corresponding A, B, C three-phase, U_gαAnd U_gβIt is right Should be line voltage vector U_gαβα axles component and beta -axis component.

In described step (3), according to following formula to three phase network electric current I_gabcCarry out Clark conversion：

Wherein：I_ga、I_gb、I_gcRespectively three phase network electric current I_gabcPhase current on corresponding A, B, C three-phase, I_gαAnd I_gβIt is right Should be power network current vector I_gαβα axles component and beta -axis component.

In described step (4), the active-power P of grid-connection converter output is calculated according to following formula_gAnd reactive power Q_g：

Wherein：U_gαAnd U_gβCorrespond to line voltage vector U_gαβα axles component and beta -axis component, I_gαAnd I_gβCorrespond to electrical network Current phasor I_gαβα axles component and beta -axis component.

In described step (5), active power reference value P is calculated according to following formula_g ^refBecome with active power reference value Rate dP_g ^ref/dt；

Wherein：k_vFor DC bus-bar voltage regulation parameter, dc-link capacitances of the C for grid-connection converter.

In described step (6), according to following formula to active-power P_gAnd reactive power Q_gCarry out that internal ring is counter to push away direct work( Rate is controlled：

Wherein：V_αAnd V_βCorrespond to modulation voltage vector V_αβα axles component and beta -axis component, k_pAnd k_qRespectively active power Regulation parameter and reactive power regulation parameter, dc-link capacitances of the C for grid-connection converter, U_gFor three-phase power grid voltage U_gabc's Phase voltage amplitude,L_gFor the inductance of grid-connection converter reactor, U_gαAnd U_gβCorrespond to line voltage Vector U_gαβα axles component and beta -axis component.

Control method of the present invention is on the basis of the mathematical model of grid-connection converter, by Backstepping and DPC technology phases With reference to, and traditional PI controllers are instead of using anti-push controller, system stability ensure that based on Lyapunov functions；This Invention while traditional DPC technologies excellent dynamic property is inherited can reduce current harmonics and power swing, and obtain constant Switching frequency；Control structure of the present invention is extremely simple, and whole control process is all carried out under rest frame, it is not necessary to passed through Rotating coordinate transformation, and only need to three adjustable parameter k_p、k_q、k_vIt is adjusted just realizing that grid-connection converter direct current is female The progressive tracking of line voltage, while realizing the quick of active grid-connection converter, reactive power independent effective control and system Response.

Description of the drawings

Fig. 1 is the principle schematic of control method of the present invention.

Fig. 2 (a) is the anti-steady-state response oscillogram for pushing away direct Power Control system of grid-connection converter.

Dynamic response oscillogram when Fig. 2 (b) pushes away inverter operation under direct Power Control for grid-connection converter is counter.

Fig. 2 (c) is the anti-dynamic response oscillogram pushed away when rectification under direct Power Control runs of grid-connection converter.

Spectrum analyses figures of the Fig. 3 for grid-connection converter A phase current.

Specific embodiment

In order to more specifically describe the present invention, below in conjunction with the accompanying drawings and specific embodiment is to technical scheme It is described in detail.

The anti-direct Power Control system that pushes away of the grid-connection converter of present embodiment includes voltage-source type grid-connection converter 1, uses In the voltage sensor 2 of detection three-phase power grid voltage and for detecting the current Hall sensor 3 of three-phase current, for detecting directly Flow the voltage sensor 4 of busbar voltage and for detecting the current Hall sensor 5 of DC side load current and realizing grid-connected Changer output is active, the control loop that reactive power is adjusted.Control loop is logical by feedback signal treatment channel and forward direction control Road is constituted, and wherein feedback signal treatment channel includes digital phase-locked loop module 6, for obtaining in stator two-phase rest frame Three-phase/biphase static coordinate the conversion module 7 of stator voltage, stator current vector signal, power computation module 8.Forward direction is controlled Passage includes that outer voltage is counter and pushes away control computing module 9, and power internal ring is counter to push away control computing module 10, SVPWM signal generators 11。

As shown in figure 1, grid-connection converter of the present invention is counter to push away direct Power Control method, comprise the following steps：

(1) 1 three-phase power grid voltage signal U of grid-connection converter is gathered using three voltage hall sensors 2_gabc；Using three Phase current Hall element 3 gathers three phase network current signal I_gabc；DC bus-bar voltage is gathered using voltage hall sensor 4 V_dc；DC side load current I is gathered using current Hall sensor 5_load；

(2) by the three-phase power grid voltage signal U for collecting_gabcThe angular frequency of line voltage is obtained through the detection of phaselocked loop 6 Rate ω_g；

(3) by the three-phase power grid voltage signal U for collecting_gabcWith three phase network current signal I_gabcThe static three-phases of Jing are arrived Two-phase coordinate transformation module 7, obtains the voltage vector U under static two phase coordinate system_gαβWith current phasor I_gαβ；With line voltage it is , the expression formula from static three-phase to two-phase coordinate transform is：

(4) by the voltage vector U for obtaining_gαβ, current phasor I_gαβActive, the nothing of output are calculated by power computation module 8 Work(power signal P_g、Q_g, active, reactive power calculates formula and is：

(5) by DC bus-bar voltage signal V_dcAnd its reference signalActive power signal P_gWith DC side load current I_loadIt is input to the anti-control module 9 that pushes away of outer voltage and obtains active power reference value P_g ^refAnd dP_g ^ref/dt；

Outer voltage is counter, and to push away control module Computing Principle as follows：

The 5.1 module control targes are its reference value of DC bus voltage following, i.e. error is zero, therefore it is female to define direct current Line voltage error is：

To its derivation, can obtain：

5.2 choose active-power P_gThe control of DC bus-bar voltage is realized as virtual controlling state.To miss tracking Difference goes to zero, and can construct following Lyapunov functions：

5.3 couples of V₁Derivation is carried out, is obtained

Order is wherein：

Wherein k_vFor DC bus-bar voltage adjustment factor, and k_v>0。

Formula 5 is brought in formula 4, can be obtained：

From Lyapunov stability analyses, e_vTo go to zero.

Formula 5 is launched by 5.4：

Therefore following virtual master function can be designed as the given reference value of active power：

And virtual error variance is selected as new state variable：

Bring in formula 2 and can obtain：

Formula 8 is brought in formula 10 and can be obtained：

Formula 4 is brought in formula 11 and can be obtained：

Obviously, when new state variable e_p, i.e., virtual error level off to zero when, P_gLevel off to virtual controlling variableCan Realize the control targe of system.

5.5 pairs of 8 derivations of formula, are calculatedConcrete formula it is as follows：

(6) according to described active power reference value P_g ^ref, given reactive power reference qref Q_g ^ref, active power reference Value changes rate dP_g ^refValue U of/dt, voltage signal in rest frame_gαβWith the angular frequency of line voltage_g, described is had Work(power P_gAnd reactive power Q_gCarry out that internal ring is counter to push away direct Power Control, obtain modulation voltage vector V_αβ；

Power internal ring is counter, and to push away control module Computing Principle as follows：

The purpose of 6.1 modules is to realize the global follow control of active power and reactive power, before have been defined for Active power error, defining reactive power error here is：

6.2 by e_v、e_p、e_qAs new state variable, and construct new Lyapunov functions：

6.3 by grid side converter mathematical model available power rate of change：

Wherein R_gValue very little, it is negligible.

6.4 couples of V₂Derivation, obtains：

Following relational expression is made to set up：

Bring formula 17 into formula 16 to obtain：

System stability is understood by Lyapunov stability analyses, and understands e_p、e_qTo go to zero.

6.5 by the expression formula that grid-connection converter output voltage can be released in formula 17：

And then V is calculated according to above formula_αβValue, wherein：u_gFor electrical network phase voltage amplitude.

(7) by V_αβValue as the reference value of SVPWM signal generator modules 11, obtain grid-connection converter switching signal S_a、 S_b、S_c；

(8) by grid-connection converter switching signal S for obtaining_a、S_b、S_cThrough drive module driving switch device, realize being based on The direct Power Control of Backstepping.

Referring to Fig. 2 (a), push away under direct Power Control method counter, present embodiment control system it is active in stable state and Reactive power waveform is steady, pulses little, and three-phase current waveform is sinusoidal, and harmonic content is little, and overall control effect is very good.

Referring to Fig. 2 (b), it can be seen that push away under direct Power Control method counter, present embodiment control system it is active And reactive power dynamic response is very rapid, while ensure that dynamic property, waveform pulsation very little, ten sub-argument of control effect Think.

Referring to Fig. 2 (c), it can be seen that push away under direct Power Control method counter, the direct current of present embodiment control system Busbar voltage dynamic response is very rapid.

Referring to Fig. 3, it can be seen that push away under direct Power Control method counter, the current harmonics of present embodiment control system Content very little.

In sum, the anti-whole control process of direct Power Control method that pushes away of grid-connection converter disclosed by the invention all exists Carry out under rest frame, it is not necessary to through rotating coordinate transformation, and only need to three adjustable parameter k_v、k_p、k_qIt is adjusted Independent, the effective control of the progressive tracking and active, reactive power of grid-connection converter DC bus-bar voltage can be just realized, is controlled Structure is very succinct.The present invention can reduce current harmonics and power waves while traditional DPC excellent dynamic properties are inherited It is dynamic, with good steady-state behaviour so that DC bus-bar voltage is more steady, and constant switching frequency can be obtained.

Claims (4)

1. a kind of the counter of grid-connection converter pushes away direct Power Control method, comprises the steps：

(1) gather three-phase power grid voltage U_gabc, three phase network electric current I_gabc, grid-connection converter DC bus-bar voltage V_dcAnd direct current Lateral load electric current I_load；

(2) three-phase power grid voltage U is detected using phaselocked loop_gabcAngular frequency_g；

(3) respectively to three-phase power grid voltage U_gabcWith three phase network electric current I_gabcClark conversion is carried out, static alpha-beta coordinate system is obtained Under line voltage vector U_gαβWith power network current vector I_gαβ；

(4) according to described line voltage vector U_gαβWith power network current vector I_gαβ, calculate the active of grid-connection converter output Power P_gAnd reactive power Q_g；

(5) according to described DC bus-bar voltage V_dc, given DC bus-bar voltage reference value V_dc ^ref, DC side load current I_loadAnd active-power P_g, active power reference value is calculated according to following formula by the anti-control algolithm that pushes away of outer voltage P_g ^refWith active power reference value rate of change dP_g ^ref/dt；

$P_g^{ref}=\[k_{v}C(V_{dc}^{ref}-V_{dc})+I_{load}\]V_{dc}$

${\mathrm{dP}}_g^{ref}/dt=\frac{1}{C}(k_v{\mathrm{CV}}_{dc}^{ref}+I_{load}-2V_{dc})(\frac{P_g}{V_{dc}}-I_{load})$

Wherein：k_vFor DC bus-bar voltage regulation parameter, dc-link capacitances of the C for grid-connection converter；

(6) according to described active power reference value P_g ^ref, given reactive power reference qref Q_g ^ref, active power reference value become Rate dP_g ^ref/ dt, line voltage vector U_gαβAnd angular frequency_g, according to following formula to described active-power P_gWith idle work( Rate Q_gCarry out that internal ring is counter to push away direct Power Control, obtain modulation voltage vector V_αβ；And then according to described modulation voltage vector V_αβ One group of pwm signal is obtained by SVPWM technical construction to be controlled grid-connection converter；

$\left\{\begin{array}{c}{V}_{\mathrm{\α}}=\frac{2L_g}{3U_g^2}\[-U_{g\mathrm{\α}}\[k_p(P_g^{ref}-P_g)+\frac{e_v}{{\mathrm{CV}}_{dc}}+{\mathrm{dP}}_g^{ref}/dt\]-U_{g\mathrm{\β}}{k}_q(Q_g^{ref}-Q_g)-{\mathrm{\ω}}_g{U}_{g\mathrm{\α}}{Q}_g+{\mathrm{\ω}}_g{U}_{g\mathrm{\β}}{P}_g\]+U_{g\mathrm{\α}}\\ V_{\mathrm{\β}}=\frac{2L_g}{3U_g^2}\[-U_{g\mathrm{\β}}\[k_p(P_g^{ref}-P_g)+\frac{e_v}{{\mathrm{CV}}_{dc}}+{\mathrm{dP}}_g^{ref}/dt\]+U_{g\mathrm{\α}}{k}_q(Q_g^{ref}-Q_g)-{\mathrm{\ω}}_g{U}_{g\mathrm{\β}}{Q}_g-{\mathrm{\ω}}_g{U}_{g\mathrm{\α}}{P}_g\]+U_{g\mathrm{\β}}\end{array}\right.$

Wherein：V_αAnd V_βCorrespond to modulation voltage vector V_αβα axles component and beta -axis component, k_pAnd k_qRespectively active power regulation Parameter and reactive power regulation parameter, U_gFor three-phase power grid voltage U_gabcPhase voltage amplitude,L_gFor grid-connected The inductance of changer reactor, U_gαAnd U_gβCorrespond to line voltage vector U_gαβα axles component and beta -axis component.

2. the counter of grid-connection converter according to claim 1 pushes away direct Power Control method, it is characterised in that：Described step Suddenly in (3), according to following formula to three-phase power grid voltage U_gabcCarry out Clark conversion：

$\left[\begin{array}{c}{U}_{g\mathrm{\α}}\\ U_{g\mathrm{\β}}\end{array}\right]=\frac{2}{3}\left[\begin{array}{ccc}1& -\frac{1}{2}& -\frac{1}{2}\\ 0& \frac{\sqrt{3}}{2}& -\frac{\sqrt{3}}{2}\end{array}\right]\left[\begin{array}{c}{U}_{ga}\\ U_{gb}\\ U_{gc}\end{array}\right]$

Wherein：U_ga、U_gb、U_gcRespectively three-phase power grid voltage U_gabcPhase voltage on corresponding A, B, C three-phase, U_gαAnd U_gβCorrespond to Line voltage vector U_gαβα axles component and beta -axis component.

3. the counter of grid-connection converter according to claim 1 pushes away direct Power Control method, it is characterised in that：Described step Suddenly in (3), according to following formula to three phase network electric current I_gabcCarry out Clark conversion：

$\left[\begin{array}{c}{I}_{g\mathrm{\α}}\\ I_{g\mathrm{\β}}\end{array}\right]=\frac{2}{3}\left[\begin{array}{ccc}1& -\frac{1}{2}& -\frac{1}{2}\\ 0& \frac{\sqrt{3}}{2}& -\frac{\sqrt{3}}{2}\end{array}\right]\left[\begin{array}{c}{I}_{ga}\\ I_{gb}\\ I_{gc}\end{array}\right]$

Wherein：I_ga、I_gb、I_gcRespectively three phase network electric current I_gabcPhase current on corresponding A, B, C three-phase, I_gαAnd I_gβCorrespond to Power network current vector I_gαβα axles component and beta -axis component.

4. the counter of grid-connection converter according to claim 1 pushes away direct Power Control method, it is characterised in that：Described step Suddenly, in (4), the active-power P of grid-connection converter output is calculated according to following formula_gAnd reactive power Q_g：

$P_g=-\frac{3}{2}\[U_{g\mathrm{\α}}{I}_{g\mathrm{\α}}+U_{g\mathrm{\β}}{I}_{g\mathrm{\β}}\]$

$Q_g=-\frac{3}{2}\[-U_{g\mathrm{\α}}{I}_{g\mathrm{\β}}+U_{g\mathrm{\β}}{I}_{g\mathrm{\α}}\]$

Wherein：U_gαAnd U_gβCorrespond to line voltage vector U_gαβα axles component and beta -axis component, I_gαAnd I_gβCorrespond to power network current Vector I_gαβα axles component and beta -axis component.