CN106655247A - LCCL-type photovoltaic grid-connected inverter d-q axis decoupling control design method - Google Patents

Abstract

The invention discloses a LCCL-type photovoltaic grid-connected inverter d-q axis decoupling control design method. The method comprises the following steps: d-q axis current reference quantity is subtracted by d-q axis current components; after being subjected to a PI regulator, d-axis controller output is subtracted by the product of a q-axis component and total filter inductance, while q-axis controller output is added by the product of a d-axis component and the total filter inductance; and when a power grid voltage has harmonics, pulsation can be caused in a power grid current, and furthermore, dynamic response of the system is influenced. For the defects in the grid-connected current decoupling control method above, the method adopts the d-q axis current reference quantity instead of d-q axis current detection components; the decoupling control method is improved based on an LCCL-type photovoltaic grid-connected inverter, and thus grid-connected power quality is improved; control basis is simplified and system efficiency is improved; fast power grid current dynamic response speed and high waveform quality and the like are realized; and influence of the passive damping control method of the LCCL-type inverter on grid-connected power loss can be further analyzed.

Description

A kind of LCCL types photovoltaic combining inverter dq decoupler shaft control design case methods

Technical field

The present invention relates to control technology field, specifically a kind of LCCL types photovoltaic combining inverter dq decoupler shaft control design cases Method.

Background technology

The energy is the power resources in human being's production life.The energy that mankind nowadays are used based on primary energy, such as The non-renewable fossil energy such as oil, coal, natural gas.Due to environmental pollution increasingly sharpen it is continuous tight with fossil energy Lack, wind energy, solar energy, tide energy etc. have become with new forms of energy the features such as renewable, pollution-free, environmental protection and grind now The emphasis studied carefully.During generation of electricity by new energy, because line voltage is constant alternating current, and wind-driven generator is output as frequency The alternating current that rate changes with wind speed, solaode output is unidirectional current, so, combining inverter just becomes new forms of energy and sends out An important component part in electric system.

In photovoltaic power generation grid-connecting, the transient characterisitics of photovoltaic parallel in system just play guiding function by inverter.In power train Analysis of the accuracy that simulation parameters are calculated in system to system is most important.But the effective ways that parameter is chosen are to imitative True measurement data is obtained by the identification of inverter model.Preferable model parameter is obtained by modeling and simulating, based on LCCL Using SVPWM controls, its LCCL wave filter has higher harmonic inhibition capability to type photovoltaic combining inverter, reduces damping and damages Consumption, improves power network current quality.In photovoltaic combining inverter, realized using the vector control method of inverter output current The control of net side real component, idle component.In actual control, when output current and the grid side voltage phase of combining inverter When position is identical, then the operation of unity power factor is realized；Otherwise when the current phase that combining inverter controls its output is ahead of Grid side voltage-phase, its combining inverter is output as real component and idle component.Have during Current Vector Control Work(component and idle component have coupling, and using the dq axles Decoupled identification control method based on PI controllers decoupling is completed Control.The present invention is proposed based on the passive damping control mode of LCCL mode filters, and the wave filter filters the harmonic wave in electric current Component, improves waveform quality, and so as to obtain more preferably current reference amount, the current reference amount is provided for improved uneoupled control Basis.And decoupling control method is improved, the decoupling control method after improvement replaces dq decoupler shafts point using dq axles reference quantity Amount.The method increase the dynamic responding speed of grid-connected system.

The content of the invention

It is an object of the invention to provide a kind of LCCL types photovoltaic combining inverter dq decoupler shaft control design case methods, to solve The problem proposed in certainly above-mentioned background technology；For achieving the above object, the present invention provides following technical scheme：A kind of LCCL types light Volt combining inverter dq decoupler shaft control design case methods, comprise the following steps：Conventional decoupling control method is introduced first, and three-phase is quiet Only in coordinate system, vector X is defined_abc=(x_a,x_b,x_c)^T, E_abc,U_abc,I_abcRespectively line voltage vector, inverter bridge side are electric Pressure vector and grid-connected current vector, due to LCCL types it is basically identical in low-frequency range output characteristics with L-type wave filter, then inverter Voltage equation can be expressed as：

R is the equivalent series resistance of inductance in formula.

When three-phase balanced system is only considered, three-phase system can be simplified to binary system, by under three-phase abc coordinate systems Model conversion into the model under α β coordinate systems, i.e.,：

X_αβ=TX_abc (2)

In formula, transformation matrix T is：

X_αβ- vector, X_αβ=(x_α, x_β)^T。

Then the equation under α β coordinate systems is：

Again by under the model conversion under α β coordinate systems to dq coordinate systems, i.e.,：

X_dq=T (θ) X_αβ (5)

In formula, transformation matrix T (θ) is：

X_dq- vector, X_dq=(x_d, x_q)^T。

Convolution (5), formula (6) simultaneously carry out changing the equation being obtained under dq coordinate systems accordingly and are：

ω in formula₀For synchronous rotary angular velocity, and ω₀=d θ/dt.

Can be obtained by formula (7)：

From formula (8), coupling is there is between d, q axle, one regulation measured of any of which would necessarily affect another Individual amount, for d, q decoupler shaft control realized, it is necessary to eliminate the coupling terms between them.Frequently with feedforward in PI current controls Coupling terms are fed forward to control signal end above by decoupling control policy；Line voltage regards external disturbance as, can pass through voltage The feedforward of component eliminating or weaken impact of the grid voltage change to grid-connected current as far as possible, while the feedforward of component of voltage Also the burden of PI controllers is mitigated.The Setting signal of PI controllers of SVPWM modulation is：

Grid-connected current decoupling control method before improvement is that electrical network electricity is separately added in output after dq axle PI controllers Stream quadrature axis component i_dWith direct-axis component i_qWith total filter inductance induction reactance w₀The product of L, in this method there is harmonic wave in power network current When, power network current dq axles component can be made to produce pulsation, i_dAnd i_qIn pulsations affect decoupling component so that-w₀Li_qAnd w₀Li_d Will there is pulsation, and then have influence on u_dAnd u *_q* the generation of middle pulsation, significantly reduces the waveform matter of power network current Amount, in Uncoupled procedure, reference voltage u_dAnd u *_q* value is by decoupling component-w₀Li_qAnd w₀Li_d, reference current i_dAnd i *_q* it is common Affect, only by reference current i_dAnd i *_q* change can not completely reflect voltage u_dAnd u *_q* change, so have impact on ginseng Examine voltage u_dAnd u *_q* rate of change, the dynamic characteristic for causing system is deteriorated.

As further scheme of the invention：Introduce based on the improvement uneoupled control of LCCL,

The voltage x current of inverter output, through the passive damping filter of LCCL types harmonic wave is filtered, and realizes wave filter humorous Shake the passive damping of spike；Because capacitive branch presents high-impedance state to fundamental current, mainly high-frequency current component passes through, institute It is relatively small to flow through capacitance current, then because LCCL mode filters are that electric capacity is in parallel, by current distributing, make the electricity for flowing through resistance Stream is less, and the loss that resistance is produced is also relatively small a lot, and LCCL mode filters filter the harmonic wave in electric current, improves electrical network electricity Stream waveform quality, weakens i_dAnd i_qMiddle pulsation of current.

System is current inner loop closed loop control, and its internal ring is based on watt current i of PI controllers_dWith reactive current i_q's Closed loop system, in current inner loop, makes given value of current amount i of q axles_q*=0, voltage vector is realized by the effect of PI controllers Coincide with current phasor, the control signal that PI controllers are produced under α β coordinate systems, through SVPWM modulation control inverters Output, it is achieved thereby that closed loop control.

System has faster dynamic responding speed and more stable after improving relative to traditional control method Waveform.Wherein parameter is defined as above.

The method is that power network current is decoupled the i in component_dAnd i_qReplace with i_dAnd i *_q*, can be derived by above-mentioned formula Go out u_dAnd u *_q* formula is as follows：

Grid-connected current decoupling control method after improvement is that electric current ginseng is separately added in output after dq axle PI controllers Consider i_dAnd i *_q* with total filter inductance induction reactance w₀The product of L, when there is harmonic wave in power network current, makes dq decoupler shaft component i_d And i_qPulsation is produced, impact of the decoupling component pulsation to network wave quality is this method avoid, reference voltage u is improve_d* and u_q* response speed, improves the dynamic characteristic of system.

Description of the drawings

Fig. 1 is a kind of LCCL types photovoltaic combining inverter Double Loop Control System figure.

Fig. 2 is Current Decoupling figure before improving

Fig. 3 is Current Decoupling figure after improving

Specific embodiment

Below in conjunction with the accompanying drawing in the embodiment of the present invention, the technical scheme in the embodiment of the present invention is carried out clear, complete Site preparation is described, it is clear that described embodiment is only a part of embodiment of the invention, rather than the embodiment of whole；It is based on Embodiment in the present invention, it is every other that those of ordinary skill in the art are obtained under the premise of creative work is not made Embodiment, belongs to the scope of protection of the invention；

Fig. 1 is a kind of LCCL types photovoltaic combining inverter Double Loop Control System figure in the present invention, as shown in figure 1, detection The net side that is connected to the grid three-phase voltage instantaneous effective values e_a, e_b, e_c, Jing rest frames transform to the component under α β coordinate systems, pass through Anglec of rotation θ of phase-locked loop pll latch voltage vector, thus can be obtained by anglec of rotation θ of synchronous rotating frame.To electricity Net electric current detected, obtains current value i_a、i_b、i_c, carrying out coordinate transform based on anglec of rotation θ can obtain under dq coordinate systems Current component be respectively i_d、i_q, then by i_d、i_qWith reference quantity i of electric current_d*、i_q* it is compared, finally in the base of PI controllers Reach on plinth to current detection value zero steady state error control.

The closed loop control of wherein PI controllers has reliability high, easily realizes, is normal in engineering the features such as easy to control A kind of control mode.The control system principle of the vector controlled of current inner loop control and grid voltage orientation based on PI Figure.

In the present invention, a kind of LCCL types photovoltaic combining inverter d q decoupler shaft control design case methods are comprised the following steps：

Conventional decoupling control method is introduced first, in three-phase static coordinate system, defines vector X_abc=(x_a,x_b,x_c)^T, E_abc,U_abc,I_abcRespectively line voltage vector, inverter bridge side voltage vector and grid-connected current vector, due to LCCL types and L Mode filter is basically identical in low-frequency range output characteristics, then the voltage equation of inverter can be expressed as：

R is the equivalent series resistance of inductance in formula.

When three-phase balanced system is only considered, three-phase system can be simplified to binary system, by under three-phase abc coordinate systems Model conversion into the model under α β coordinate systems, i.e.,：

X_αβ=TX_abc (2)

In formula, transformation matrix T is：

X_αβ- vector, X_αβ=(x_α, x_β)^T。

Then the equation under α β coordinate systems is：

Again by under the model conversion under α β coordinate systems to dq coordinate systems, i.e.,：

X_dq=T (θ) X_αβ (5)

In formula, transformation matrix T (θ) is：

X_dq- vector, X_dq=(x_d, x_q)^T。

Convolution (5), formula (6) simultaneously carry out changing the equation being obtained under dq coordinate systems accordingly and are：

ω in formula₀For synchronous rotary angular velocity, and ω₀=d θ/dt.

Can be obtained by formula (7)：

From formula (8), coupling is there is between d, q axle, one regulation measured of any of which would necessarily affect another Individual amount, for d, q decoupler shaft control realized, it is necessary to eliminate the coupling terms between them.Frequently with feedforward in PI current controls Coupling terms are fed forward to control signal end above by decoupling control policy；Line voltage regards external disturbance as, can pass through voltage The feedforward of component eliminating or weaken impact of the grid voltage change to grid-connected current as far as possible, while the feedforward of component of voltage Also the burden of PI controllers is mitigated.The Setting signal of PI controllers of SVPWM modulation is：

As shown in Figure 2, the grid-connected current decoupling control method before improvement is distinguished in the output after dq axle PI controllers Add power network current quadrature axis component i_dWith direct-axis component i_qWith total filter inductance induction reactance w₀The product of L, power network current in this method When there is harmonic wave, power network current dq axles component can be made to produce pulsation, i_dAnd i_qIn pulsations affect decoupling component so that-w₀Li_q And w₀Li_dAlso will there is pulsation, and then have influence on u_dAnd u *_q* the generation of middle pulsation, significantly reduces power network current Waveform quality.In Uncoupled procedure, reference voltage u_dAnd u *_q* value is by decoupling component-w₀Li_qAnd w₀Li_d, reference current i_d* And i_q* joint effect, only by reference current i_dAnd i *_q* change can not completely reflect voltage u_dAnd u *_q* change, so Have impact on reference voltage u_dAnd u *_q* rate of change, the dynamic characteristic for causing system is deteriorated.

As further scheme of the invention：Introduce based on the improvement uneoupled control of LCCL,

The voltage x current of inverter output, through the passive damping filter of LCCL types harmonic wave is filtered, and realizes wave filter humorous Shake the passive damping of spike.Because capacitive branch presents high-impedance state to fundamental current, mainly high-frequency current component passes through, institute It is relatively small to flow through capacitance current, then because LCCL mode filters are that electric capacity is in parallel, by current distributing, make the electricity for flowing through resistance Stream is less, and the loss that resistance is produced is also relatively small a lot.LCCL mode filters filter the harmonic wave in electric current, improve electrical network electricity Stream waveform quality, weakens i_dAnd i_qMiddle pulsation of current.

System is current inner loop closed loop control, and its internal ring is based on watt current i of PI controllers_dWith reactive current i_q's Closed loop system.In current inner loop, given value of current amount i of q axles is made_q*=0, voltage vector is realized by the effect of PI controllers Coincide with current phasor, the control signal that PI controllers are produced under α β coordinate systems, through SVPWM modulation control inverters Output, it is achieved thereby that closed loop control.

System has faster dynamic responding speed and more stable after improving relative to traditional control method Waveform.Wherein parameter is defined as above.

The method is that power network current is decoupled the i in component_dAnd i_qReplace with i_dAnd i *_q*, can be derived by above-mentioned formula Go out u_dAnd u *_q* formula is as follows：

Grid-connected current decoupling control method after improvement is that electric current ginseng is separately added in output after dq axle PI controllers Consider i_dAnd i *_q* with total filter inductance induction reactance w₀The product of L, when there is harmonic wave in power network current, makes dq decoupler shaft component i_d And i_qPulsation is produced, impact of the decoupling component pulsation to network wave quality is this method avoid, reference voltage u is improve_d* and u_q* response speed, improves the dynamic characteristic of system.

It is obvious to a person skilled in the art that the invention is not restricted to the details of above-mentioned one exemplary embodiment, Er Qie In the case of spirit or essential attributes without departing substantially from the present invention, the present invention can be in other specific forms realized；Therefore, no matter From the point of view of which point, embodiment all should be regarded as exemplary, and be nonrestrictive, the scope of the present invention is by appended power Profit is required rather than described above is limited, it is intended that all in the implication and scope of the equivalency of claim by falling Change is included in the present invention, should not be considered as any reference in claim and be limited involved claim；

Moreover, it will be appreciated that although this specification is been described by according to embodiment, not each embodiment is only wrapped Containing an independent technical scheme, this narrating mode of description is only that for clarity those skilled in the art should Using description as an entirety, the technical scheme in each embodiment can also Jing it is appropriately combined, form those skilled in the art Understandable other embodiment.

Claims (2)

1. a kind of LCCL types photovoltaic combining inverter d q decoupler shaft control design case methods, it is characterised in that comprise the following steps：

Conventional decoupling control is introduced first, in three-phase static coordinate system, defines vector X_abc=(x_a,x_b,x_c)^T, E_abc,U_abc,I_abc Respectively line voltage vector, inverter bridge side voltage vector and grid-connected current vector, due to LCCL types with L-type wave filter low Frequency range output characteristics is basically identical, then the voltage equation of inverter can be expressed as：

$U_{abc}=E_{abc}+I_{abc}R+L\frac{I_{abc}}{dt}---\left(1\right)$

R is the equivalent series resistance of inductance in formula,

When three-phase balanced system is only considered, three-phase system can be simplified to binary system, by the model under three-phase abc coordinate systems The model being converted under α β coordinate systems, i.e.,：

X_αβ=TX_abc (2)

In formula, transformation matrix T is：

$T=\left[\begin{array}{ccc}1& -\frac{1}{2}& -\frac{1}{2}\\ 0& \frac{\sqrt{3}}{2}& -\frac{\sqrt{3}}{2}\end{array}\right]---\left(3\right)$

X_αβ- vector, X_αβ=(x_α, x_β)^T,

Then the equation under α β coordinate systems is：

$U_{\mathrm{\α}\mathrm{\β}}=E_{\mathrm{\α}\mathrm{\β}}+I_{\mathrm{\α}\mathrm{\β}}R+L\frac{I_{\mathrm{\α}\mathrm{\β}}}{dt}---\left(4\right)$

Again by under the model conversion under α β coordinate systems to dq coordinate systems, i.e.,：

X_dq=T (θ) X_αβ (5)

In formula, transformation matrix T (θ) is：

$T\left(\mathrm{\θ}\right)=\left[\begin{array}{cc}cos\mathrm{\θ}& sin\mathrm{\θ}\\ -\sin \mathrm{\θ}& \cos \mathrm{\θ}\end{array}\right]---\left(6\right)$

X_dq- vector, X_dq=(x_d, x_q)^T,

Convolution (5), formula (6) simultaneously carry out changing the equation being obtained under dq coordinate systems accordingly and are：

$U_{dq}=E_{dq}+I_{dq}R+L\frac{{\mathrm{dI}}_{dq}}{dt}+\left[\begin{array}{cc}0& -{\mathrm{\ω}}_{0}L\\ {\mathrm{\ω}}_{0}L& 0\end{array}\right]I_{dq}---\left(7\right)$

ω in formula₀For synchronous rotary angular velocity, and ω₀=d θ/dt,

Can be obtained by formula (7)：

$\left\{\begin{array}{c}{u}_d=L\frac{{\mathrm{di}}_d}{dt}+e_d+{\mathrm{Ri}}_d-{\mathrm{\ω}}_0{\mathrm{Li}}_q\\ u_q=L\frac{{\mathrm{di}}_q}{dt}+e_q+{\mathrm{Ri}}_q+{\mathrm{\ω}}_0{\mathrm{Li}}_d\end{array}\right.---\left(8\right)$

From formula (8), coupling is there is between d, q axle, the regulation of one amount of any of which would necessarily affect another amount, For d, q decoupler shaft control realized, it is necessary to the coupling terms between them are eliminated, frequently with Feedforward Decoupling control in PI current controls Coupling terms are fed forward to control signal end above by system strategy；Line voltage regards external disturbance as, can pass through component of voltage Feedover to eliminate or weaken impact of the grid voltage change to grid-connected current as far as possible, while the feedforward of component of voltage also mitigates The burden of PI controllers, the Setting signal of PI controllers of SVPWM modulation is：

$\left\{\begin{array}{c}{u^{*}}_d=K_{iP}\left(\frac{{\mathrm{\τ}}_{i}s+1}{{\mathrm{\τ}}_{i}s}\right)({i_d}^{*}-i_d)+e_d-{\mathrm{\ω}}_0{\mathrm{Li}}_q\\ {u^{*}}_q=K_{iP}\left(\frac{{\mathrm{\τ}}_{i}s+1}{{\mathrm{\τ}}_{i}s}\right)({i_q}^{*}-i_q)+e_q+{\mathrm{\ω}}_0{\mathrm{Li}}_d\end{array}\right.---\left(9\right)$

Grid-connected current decoupling control method before improvement is that power network current friendship is separately added in output after dq axle PI controllers Axle component i_dWith direct-axis component i_qWith total filter inductance induction reactance w₀The product of L, when in this method there is harmonic wave in power network current, meeting Power network current dq axles component is set to produce pulsation, i_dAnd i_qIn pulsations affect decoupling component so that-w₀Li_qAnd w₀Li_dAlso will deposit In pulsation, and then have influence on u_dAnd u *_q* the generation of middle pulsation, significantly reduces the waveform quality of power network current, in solution During coupling, reference voltage u_dAnd u *_q* value is by decoupling component-w₀Li_qAnd w₀Li_d, reference current i_dAnd i *_q* joint effect, only By reference current i_dAnd i *_q* change can not completely reflect voltage u_dAnd u *_q* change, so have impact on reference voltage u_dAnd u *_q* rate of change, the dynamic characteristic for causing system is deteriorated.

2. a kind of LCCL types photovoltaic combining inverter d q decoupler shaft control design case methods according to claim 1, its feature It is：

The improvement uneoupled control of LCCL is introduced, the voltage x current of inverter output is filtered through the passive damping filter of LCCL types Harmonic wave, realizes the passive damping of filter resonance spike；Because capacitive branch presents high-impedance state to fundamental current, mainly High-frequency current component passes through, so it is relatively small to flow through capacitance current, then because LCCL mode filters are that electric capacity is in parallel, by electric current Shunting, makes the electric current for flowing through resistance less, and the loss that resistance is produced is also relatively small a lot, and LCCL mode filters are filtered in electric current Harmonic wave, improve power network current waveform quality, weaken i_dAnd i_qMiddle pulsation of current；System is current inner loop closed loop control, its Internal ring is based on watt current i of PI controllers_dWith reactive current i_qClosed loop system, in current inner loop, make the electric current of q axles Specified rate i_q*=0, realize that voltage vector coincides with current phasor by the effect of PI controllers, PI controllers are in α β coordinates The lower control signal for producing of system, through the output of SVPWM modulation control inverters, it is achieved thereby that closed loop control, system process After improvement, there is faster dynamic responding speed and more stable waveform relative to traditional control method；The method be by I in power network current decoupling component_dAnd i_qReplace with i_dAnd i *_q*, u can be derived by above-mentioned formula_dAnd u *_q* formula is as follows：

$\left\{\begin{array}{c}{u^{*}}_d=K_{iP}\left(\frac{{\mathrm{\τ}}_{i}s+1}{{\mathrm{\τ}}_{i}s}\right)({i_d}^{*}-i_d)+e_d-{\mathrm{\ω}}_0{{\mathrm{Li}}_q}^{*}\\ {u^{*}}_q=K_{iP}\left(\frac{{\mathrm{\τ}}_{i}s+1}{{\mathrm{\τ}}_{i}s}\right)({i_q}^{*}-i_q)+e_q+{\mathrm{\ω}}_0{{\mathrm{Li}}_d}^{*}\end{array}\right.---\left(10\right)$

Grid-connected current decoupling control method after improvement is to be separately added into current reference amount in output after dq axle PI controllers i_dAnd i *_q* with total filter inductance induction reactance w₀The product of L, when there is harmonic wave in power network current, makes dq decoupler shaft component i_dAnd i_qProduce Raw pulsation, this method avoid impact of the decoupling component pulsation to network wave quality, improve reference voltage u_dAnd u *_q* anti- Speed is answered, the dynamic characteristic of system is improved.