CN105006828A - Grid-connected converter negative sequence current compensation method - Google Patents

Abstract

The invention discloses a grid-connected converter negative sequence current compensation method. The voltage of a direct current bus of a grid-connected converter is sampled. Square calculation, notch filtering and square root calculation are carried out on the sample value. Voltage fluctuation component of the direct current bus is filtered out. Through decoupling of alternating current-direct current active power of the direct current bus, closed-loop control is carried out on the voltage of the direct current bus of the grid-connected converter. According to the invention, the problem of disturbance of fluctuations of alternating current active power of the direct current bus on the voltage of the direct current bus and grid-connected current control is solved when the grid-connected converter carries out negative sequence current compensation; the control accuracy of the voltage of the direct current bus and the power quality of grid-connected current are effectively improved; and through decoupling of alternating current-direct current active power of the direct current bus of the grid-connected converter, the maximum fluctuation amplitude of the voltage of the direct current bus is accurately calculated in a negative sequence current compensation process.

Description

The compensation method of a kind of grid-connected converter negative-sequence current

Technical field

The present invention relates to the grid-connected converter negative-sequence current compensation policy of decoupling zero of gaining merit based on DC bus alternating current-direct current, belong to applied power electronics technical field.

Background technology

Due to the existence of electric network fault, asymmetrical three-phase load or power supply three-phase grid electric current asymmetry, load or power supply inject negative-sequence current by electrical network access point to electric power system, the hree-phase symmetry of appreciable impact line voltage, even causes the intensification further of electric network fault.The negative-sequence current of specific electrical network access point can be detected by grid-connected converter, and realize negative-sequence current compensation.But because the output of negative sequence compensation electric current, the instantaneous power of grid-connected converter output exist AC ripple, make grid-connected converter DC bus-bar voltage there is pulsation, cause the closed-loop current control hydraulic performance decline of grid-connected converter even to control failure.

The negative-sequence current of current grid-connected converter compensates, and consider the filter effect of dc-link capacitance, the DC bus-bar voltage of many Direct Sampling grid-connected converter carries out closed loop feedback control.On the one hand, these class methods cause there is close coupling between direct current power and AC power control ring, cause grid-connected converter output current aberration rate high; On the other hand, grid-connected converter is difficult to retrain DC bus-bar voltage fluctuation amplitude, and easy generation system is out of control.

Putting before this, by the AC and DC power decoupled of grid-connected converter in negative-sequence current compensation process and the k-factor correction of voltage modulated, realize controlled to the model-following control of command quantity and DC bus-bar voltage fluctuation amplitude of DC bus-bar voltage DC component, for promoting the quality of power supply of grid-connected converter output current, negative-sequence current compensation effect, DC bus-bar voltage control precision, grid-connected converter control stability and grid stability, equal significance.

Summary of the invention

The present invention is directed to above-mentioned technical barrier, sampling grid-connected converter DC bus-bar voltage instantaneous value, extract the feedback quantity of DC bus-bar voltage DC component as direct current power control ring, carry out k-factor correction by the voltage output of DC bus-bar voltage coefficient of variation to Current Control closed loop; And under DC bus-bar voltage pulsation allows given, the negative sequence compensation current amplitude of amplitude and the given condition of phase place, provide the constraint computational methods of positive sequence referenced reactive current.One aspect of the present invention achieves the decoupling zero that direct current power and AC power control, and solves DC bus-bar voltage in negative-sequence current compensation process and controls the problem that difficulty is large, output current of converter aberration rate is high; Breach the technical barrier that the reasonable given range of negative sequence compensation current-order amount is difficult to determine on the other hand.

For solving the problems of the technologies described above, the invention provides the compensation method of a kind of grid-connected converter negative-sequence current, it is characterized in that:

Sampling grid-connected converter DC bus-bar voltage, carry out a square calculating, notch filter and square root to this sampled value to calculate, filtering DC bus-bar voltage wave component, by the decoupling zero of DC bus alternating current-direct current active power, carries out closed-loop control to grid-connected converter DC bus-bar voltage.

Comprise the following steps:

1) sampling grid-connected converter DC bus-bar voltage warp square calculates this signal is inputted as notch filter, filtering DC bus-bar voltage alternating component, square root is carried out in notch filter output and calculates dC component

2) with U _dc ^*as DC bus-bar voltage command quantity, with as DC bus active-power P I conditioning controller G _pIs the feedback of (), obtains DC bus active power DC quantity instruction P by controller _dc ^*;

3) electrical network negative sequence voltage and negative sequence compensation instruction current phase difference is calculated given negative sequence compensation current-order amplitude obtain synchronous rotating frame negative phase-sequence d axle, the instruction of q axle offset current calculate synchronous rotating frame positive sequence d shaft current command quantity

4) angle between positive sequence d axle and three phase static A axle is made to be θ ^p, between negative phase-sequence d axle and three phase static A axle, angle is θ ⁿ, calculated by space vector, obtain instantaneous active power alternating current component P _ac:

P _ac＝P _c2cos(θ ⁿ-θ ^p)+P _s2sin(θ ⁿ-θ ^p) (1)

If $P_{c2}=u_{gdn}^n\left(i_{gdp}^{p*}\right)+u_{gdp}^p\left(i_{gdn}^{n*}\right),P_{s2}=u_{gdn}^n\left(i_{gqp}^{p*}\right)-u_{gdp}^p\left(i_{gqn}^{n*}\right);$ Wherein, with be respectively the instruction of synchronous rotating frame positive sequence d shaft current, the instruction of positive sequence q shaft current, the instruction of negative phase-sequence d shaft current and the instruction of negative phase-sequence q shaft current; with be respectively the instruction of synchronous rotating frame positive sequence d shaft voltage, the instruction of positive sequence q shaft voltage, the instruction of negative phase-sequence d shaft voltage and the instruction of negative phase-sequence q shaft voltage;

According to the permission fluctuation maximum amplitude of given current transformer DC bus-bar voltage and formula (1):

${\mathrm{\ΔU}}_{dc}\≤U_{dc}^{*}-\sqrt{-\frac{\sqrt{{P_{c2}}^2+{P_{s2}}^2}}{{\mathrm{\ω}}_{1}C}+U_{dc}^{*2}}---\left(2\right);$

Will $P_{c2}=u_{gdn}^n\left(i_{gdp}^{p*}\right)+u_{gdp}^p\left(i_{gdn}^{n*}\right)$ With $P_{s2}=u_{gdn}^n\left(i_{gqp}^{p*}\right)-u_{gdp}^p\left(i_{gqn}^{n*}\right)$ Bring formula (2) into, the constraints obtaining positive sequence reactive-current compensation is:

5) current transformer grid-connected current maximum amplitude in synchronous dq rotating coordinate system is made to be I _{n_dq}, solve inequation according to capacity limit $\sqrt{i_{gdp}^{p*2}+i_{gqp}^{p*2}}+\sqrt{i_{gdn}^{n*2}+i_{gqn}^{n*2}}\≤I_{N\_dq},$ Obtain numerical intervals be $i_{\mathrm{gqp}}^{p*}\∈[-N,N],$ Wherein N is positive rational number or irrational number;

6) according to formula (3), positive sequence q shaft current command quantity in synchronous rotating frame is asked for numerical intervals, determine this command quantity by output maximum inductive idle or that minimum perception of dissolving is idle principle;

7) under synchronous rotating frame, positive-negative sequence current governing equation is provided by formula (4), formula (5):

$\left\{\begin{array}{c}{v}_{con\_dp}^p=(-u_{con\_dp}^{p^{\′}}+{\mathrm{\Δu}}_{con\_dp}^p)K\\ v_{con\_qp}^p=(-u_{con\_qp}^{p^{\′}}+{\mathrm{\Δu}}_{con\_qp}^p)K\end{array}\right.---\left(4\right)$

$\left\{\begin{array}{c}{v}_{con\_dn}^n=(-u_{con\_dn}^{n^{\′}}+{\mathrm{\Δu}}_{con\_dn}^n)K\\ v_{con\_qn}^n=(-u_{con\_qn}^{n^{\′}}+{\mathrm{\Δu}}_{con\_qn}^n)K\end{array}\right.---\left(5\right)$

In formula:

$u_{con\_dp}^{p^{\′}}={\mathrm{Ri}}_{gdp}^p+L\frac{{\mathrm{di}}_{gdp}^p}{dt},$

$u_{con\_qp}^{p^{\′}}={\mathrm{Ri}}_{gqp}^p+L\frac{{\mathrm{di}}_{gqp}^p}{dt},$

${\mathrm{\Δu}}_{con\_dp}^p={\mathrm{\ω}}_1{\mathrm{Li}}_{gqp}^p+u_{gqp}^p,$

${\mathrm{\Δu}}_{con\_qp}^p=-{\mathrm{\ω}}_1{\mathrm{Li}}_{gdp}^p+u_{gdp}^p,$

$u_{con\_dn}^{n^{\′}}={\mathrm{Ri}}_{gdn}^n+L\frac{{\mathrm{di}}_{gdn}^n}{dt},$

$u_{con\_qn}^{n^{\′}}={\mathrm{Ri}}_{gqn}^n+L\frac{{\mathrm{di}}_{gqn}^n}{dt},$

${\mathrm{\Δu}}_{con\_dn}^n=-{\mathrm{\ω}}_1{\mathrm{Li}}_{gqn}^n+u_{gqn}^n,$

${\mathrm{\Δu}}_{con\_qn}^n={\mathrm{\ω}}_1{\mathrm{Li}}_{gdn}^n+u_{gdn}^n.$

In formula, u represents voltage, Δ u represents electric voltage feed forward item, in its subscript " ' " represent that this voltage is voltage control item, in its subscript, " con " represents current transformer output valve, d, q in its subscript represent synchronous rotating frame d axle, synchronous rotating frame q axle respectively, and p, n in subscript represent positive sequence component, negative sequence component respectively, and p, n in subscript represent that this component is positioned at positive sequence synchronous rotating frame, negative phase-sequence synchronous rotating frame respectively; r represents grid-connected line resistance, and L represents grid-connected line inductance;

8) according to formula (4), formula (5) analytical expression, by the pi regulator G of each dq axle of positive-negative sequence _pIs () carries out closed-loop control, obtain the control voltage of each dq axle of positive-negative sequence with

By the calculating of positive-negative sequence each dq axle control voltage and feedforward term, and be multiplied by DC bus-bar voltage coefficient of variation K and correct, obtain the current transformer output voltage of each dq axle of positive-negative sequence with

By two-phase rotating coordinate system-two-phase rest frame coordinate transform, obtain the component of current transformer positive-negative sequence output voltage in α, β rest frame respectively with wherein, subscript α, β represents that this component is positioned at α, β rest frame respectively;

By the synthesis of α, β axle positive-negative sequence output voltage, obtain grid-connected converter output voltage space vector, and carry out pulse-width modulation.

The transfer function of notch filter is wherein Q is quality factor, ω ₁for line voltage synchronously uses frequency.

Step 3) in,

Pass through formula calculate synchronous rotating frame positive sequence d shaft current command quantity

Step 6) in, if obtain according to formula (3) numerical intervals expression formula is then set positive sequence q shaft current command quantity

If obtain according to formula (3) numerical intervals expression formula is a, B are positive rational number or irrational number, then set positive sequence q shaft current command quantity $i_{gqp}^{p*}=max\{\[-N,N\]\∩\[-\mathrm{\∞},A\]\∪\[B,+\mathrm{\∞}\]\}\},$ And [-N, N] ∩ { [-∞, A] ∪ [B ,+∞] } for nonvoid set and.

The beneficial effect that the present invention reaches:

The present invention is by sampling grid-connected converter DC bus-bar voltage, carry out a square calculating, notch filter and square root to this measured value to calculate, the DC bus-bar voltage wave component that the AC power that filtering produces due to positive-negative sequence electric current and voltage causes, by the decoupling zero of DC bus alternating current-direct current active power, achieve the grid-connected converter DC bus-bar voltage closed-loop control based on DC bus DC component feedback.Because negative-sequence current compensation can cause DC bus-bar voltage to fluctuate, the present invention passes through the ratio of DC bus-bar voltage actual observation amount and DC component, obtain DC bus-bar voltage coefficient of variation K, and connect in grid-connected current controller, this series connection coefficient significantly reduces the disturbance that DC bus-bar voltage fluctuation controls grid-connected converter.

On the one hand, when the invention solves grid-connected converter enforcement negative-sequence current compensation, DC bus exchanges the problem of active power fluctuation to DC bus-bar voltage, grid-connected current control generation disturbance, effectively improves the control precision of DC bus-bar voltage and the quality of power supply of grid-connected current.On the other hand, the present invention, by the decoupling zero of grid-connected converter DC bus alternating current-direct current active power, achieves the accurate Calculation of DC bus-bar voltage maximum fluctuation amplitude in negative-sequence current compensation process.Under the condition that the present invention is given in negative sequence compensation current amplitude phase place, calculate the instruction of synchronous rotating frame positive sequence d shaft current, for the determination of synchronous rotating frame positive sequence reactive current (positive sequence q shaft current) command quantity provides analytic method.

Accompanying drawing explanation

Fig. 1 grid-connected converter hardware topology;

Fig. 2 synchronous rotating frame positive-negative sequence instruction current computational methods;

Fig. 3 is based on the voltage oriented grid-connected converter Current Control schematic diagram of positive-negative sequence.

Embodiment

Below in conjunction with accompanying drawing, the invention will be further described.Following examples only for technical scheme of the present invention is clearly described, and can not limit the scope of the invention with this.

1) grid-connected converter hardware topology as shown in Figure 1.Make positive sequence q shaft voltage in synchronous rotating frame make negative phase-sequence q shaft voltage in synchronous rotating frame in formula, subscript " g " represents grid side physical quantity, and " d " represents synchronous rotating frame d axle, and " q " represents synchronous rotating frame q axle, and " p " represents positive sequence component, and " n " represents negative sequence component; Subscript " p " represents that this component is positioned at positive sequence synchronous rotating frame, and subscript " n " represents that this component is positioned at negative phase-sequence synchronous rotating frame.

2) current transformer DC bus-bar voltage of as shown in Figure 2, sampling obtains warp square calculates this signal is inputted as notch filter, the DC bus-bar voltage alternating component that filtering causes due to DC bus interchange active power, square root is carried out in notch filter output and calculates dC component wherein, notch filter transfer function is wherein Q is quality factor, ω ₁for line voltage synchro angle frequency and ω ₁=100 π.With U _dc ^*as DC bus-bar voltage command quantity, with as DC bus active-power P I conditioning controller G _pIs the feedback of (), obtains DC bus active power DC quantity instruction P by controller _dc ^*.

3) by measuring and anti-phase calculating, electrical network negative sequence voltage and negative sequence compensation instruction current phase difference is obtained given negative sequence compensation current-order amplitude obtain synchronous rotating frame negative phase-sequence d, the instruction of q axle offset current pass through formula calculate synchronous rotating frame positive sequence d shaft current command quantity

4) angle between positive sequence d axle and three phase static A axle (the static α axle of two-phase) is made to be θ ^p, between negative phase-sequence d axle and three phase static A axle (the static α axle of two-phase), angle is θ ⁿ, calculated by space vector, can obtain instantaneous active power alternating current component expression formula is:

P _ac＝P _c2cos(θ ⁿ-θ ^p)+P _s2sin(θ ⁿ-θ ^p) (1)

In formula: P _c2, P _s2be respectively the cosine and sinusoidal component amplitude that exchange active power, $P_{s2}=u_{\mathrm{gdn}}^n\left(i_{\mathrm{gqp}}^{*}\right)-u_{\mathrm{gdp}}^p\left(i_{\mathrm{gqn}}^{n*}\right),$ Wherein, with be respectively the instruction of synchronous rotating frame positive sequence d shaft current, the instruction of positive sequence q shaft current, the instruction of negative phase-sequence d shaft current and the instruction of negative phase-sequence q shaft current; with be respectively the instruction of synchronous rotating frame positive sequence d shaft voltage, the instruction of positive sequence q shaft voltage, the instruction of negative phase-sequence d shaft voltage and the instruction of negative phase-sequence q shaft voltage; .If U _dc, U _{dc_average}be respectively current transformer DC bus-bar voltage and DC component, under the condition that DC bus active power DC component is controlled, according to the permission fluctuation maximum amplitude of given current transformer DC bus-bar voltage and formula (1) can obtain:

${\mathrm{\ΔU}}_{dc}\≤U_{dc}^{*}-\sqrt{-\frac{\sqrt{{P_{c2}}^2+{P_{s2}}^2}}{{\mathrm{\ω}}_{1}C}{U}_{dc}^{*2}}---\left(2\right)$

Will $P_{c2}=u_{gdn}^n\left(i_{gdp}^{p*}\right)+u_{gdp}^p\left(i_{gdn}^{n*}\right)$ With $P_{s2}=u_{gdn}^n\left(i_{gqp}^{p*}\right)-u_{gdp}^p\left(i_{gqn}^{n*}\right)$ Bring formula (2) into, the constraints that can obtain positive sequence reactive-current compensation is:

5) according to step 3) known with, current transformer grid-connected current maximum amplitude in synchronous dq rotating coordinate system is made to be I _{n_dq}, solve inequation according to capacity limit $\sqrt{i_{gdp}^{p*2}+i_{gqp}^{p*2}}+\sqrt{i_{gdn}^{n*2}+i_{gqn}^{n*2}}\≤I_{N\_dq},$ Obtain numerical intervals be $i_{\mathrm{gqp}}^{p*}\∈[-N,N],$ Wherein N is positive rational number or irrational number.

6) according to formula (3), positive sequence q shaft current command quantity in synchronous rotating frame is asked for numerical intervals, determine this command quantity by output maximum inductive idle or that minimum perception of dissolving is idle principle.According to linear equation in two unknowns disaggregation characteristic, if obtain according to formula (3) numerical intervals expression formula is then set positive sequence q shaft current command quantity if obtain according to formula (3) numerical intervals expression formula is a, B are positive rational number or irrational number, then set positive sequence q shaft current command quantity $i_{gqp}^{p*}=max\{\[-N,N\]\∩\[-\mathrm{\∞},A\]\∪\[B,+\mathrm{\∞}\]\}\},$ And [-N, N] ∩ { [-∞, A] ∪ [B ,+∞] } for nonvoid set and.

7) under synchronous rotating frame, positive-negative sequence current governing equation is provided by formula (4), formula (5):

$\left\{\begin{array}{c}{v}_{con\_dp}^p=(-u_{con\_dp}^{p^{\′}}+{\mathrm{\Δu}}_{con\_dp}^p)K\\ v_{con\_qp}^p=(-u_{con\_qp}^{p^{\′}}+{\mathrm{\Δu}}_{con\_qp}^p)K\end{array}\right.---\left(4\right)$

$\left\{\begin{array}{c}{v}_{con\_dn}^n=(-u_{con\_dn}^{n^{\′}}+{\mathrm{\Δu}}_{con\_dn}^n)K\\ v_{con\_qn}^n=(-u_{con\_qn}^{n^{\′}}+{\mathrm{\Δu}}_{con\_qn}^n)K\end{array}\right.---\left(5\right)$

In formula:

$u_{con\_dp}^{p^{\′}}={\mathrm{Ri}}_{gdp}^p+L\frac{{\mathrm{di}}_{gdp}^p}{dt},$

$u_{con\_qp}^{p^{\′}}={\mathrm{Ri}}_{gqp}^p+L\frac{{\mathrm{di}}_{gqp}^p}{dt},$

${\mathrm{\Δu}}_{con\_dp}^p={\mathrm{\ω}}_1{\mathrm{Li}}_{gqp}^p+u_{gqp}^p,$

${\mathrm{\Δu}}_{con\_qp}^p=-{\mathrm{\ω}}_1{\mathrm{Li}}_{gdp}^p+u_{gdp}^p,$

$u_{con\_dn}^{n^{\′}}={\mathrm{Ri}}_{gdn}^n+L\frac{{\mathrm{di}}_{gdn}^n}{dt},$

$u_{con\_qn}^{n^{\′}}={\mathrm{Ri}}_{gqn}^n+L\frac{{\mathrm{di}}_{gqn}^n}{dt},$

${\mathrm{\Δu}}_{con\_dn}^n=-{\mathrm{\ω}}_1{\mathrm{Li}}_{gqn}^n+u_{gqn}^n,$

${\mathrm{\Δu}}_{con\_qn}^n={\mathrm{\ω}}_1{\mathrm{Li}}_{gdn}^n+u_{gdn}^n.$

In formula, u represents voltage, subscript " ' " representing that this voltage is voltage control item (as shown in Figure 3 pi regulator output item), Δ u represents electric voltage feed forward item, and subscript " con " wherein represents current transformer output valve, r represents the grid-connected line resistance (R=R shown in Fig. 1 _a=R _b=R _c), L represents the grid-connected line inductance (L=L shown in Fig. 1 _a=L _b=L _c).

8) according to formula (4), formula (5) analytical expression, the grid-connected converter Current Control principle voltage oriented based on positive-negative sequence is as shown in Figure 3 obtained.In figure, with be respectively the instruction of synchronous rotating frame positive sequence d shaft current, the instruction of positive sequence q shaft current, the instruction of negative phase-sequence d shaft current and the instruction of negative phase-sequence q shaft current; with be respectively synchronous rotating frame positive sequence d shaft current measured value, positive sequence q shaft current measured value, negative phase-sequence d shaft current measured value and negative phase-sequence q shaft current measured value.By the pi regulator G of each dq axle of positive-negative sequence _pIs () carries out closed-loop control, obtain the control voltage of each dq axle of positive-negative sequence with by the algorithm calculations of positive-negative sequence each dq axle control voltage and feedforward term, and be multiplied by DC bus-bar voltage coefficient of variation K and correct, obtain the current transformer output voltage of each dq axle of positive-negative sequence with by two-phase rotating coordinate system-two-phase rest frame coordinate transform, obtain the component of current transformer positive-negative sequence output voltage in α, β rest frame respectively with wherein, subscript " α ", " β " represent that this component is positioned at α, β rest frame respectively.By the synthesis of α, β axle positive-negative sequence output voltage, obtain grid-connected converter output voltage space vector, and carry out pulse-width modulation.

The above is only the preferred embodiment of the present invention; it should be pointed out that for those skilled in the art, under the prerequisite not departing from the technology of the present invention principle; can also make some improvement and distortion, these improve and distortion also should be considered as protection scope of the present invention.

Claims (5)

1. a grid-connected converter negative-sequence current compensation method, is characterized in that:

Sampling grid-connected converter DC bus-bar voltage, carry out a square calculating, notch filter and square root to this sampled value to calculate, filtering DC bus-bar voltage wave component, by the decoupling zero of DC bus alternating current-direct current active power, carries out closed-loop control to grid-connected converter DC bus-bar voltage.

2. grid-connected converter negative-sequence current according to claim 1 compensation method, is characterized in that, comprise the following steps:

1) sampling grid-connected converter DC bus-bar voltage warp square calculates this signal is inputted as notch filter, filtering DC bus-bar voltage alternating component, square root is carried out in notch filter output and calculates dC component

2) with U _dc ^*as DC bus-bar voltage command quantity, with as DC bus active-power P I conditioning controller G _pIs the feedback of (), obtains DC bus active power DC quantity instruction P by controller _dc ^*;

3) electrical network negative sequence voltage and negative sequence compensation instruction current phase difference is calculated given negative sequence compensation current-order amplitude obtain synchronous rotating frame negative phase-sequence d axle, the instruction of q axle offset current calculate synchronous rotating frame positive sequence d shaft current command quantity

4) angle between positive sequence d axle and three phase static A axle is made to be θ _p, between negative phase-sequence d axle and three phase static A axle, angle is θ ⁿ, calculated by space vector, obtain instantaneous active power alternating current component P _ac:

P _ac＝P _c2cos(θ _n-θ _p)+P _s2sin(θ _n-θ _p) (1)

In formula $P_{c2}=u_{gdn}^n\left(i_{gdp}^{p*}\right)+u_{gdp}^p\left(i_{gdn}^{n*}\right),P_{s2}=u_{gdn}^n\left(i_{gqp}^{p*}\right)-u_{gdp}^p\left(i_{gqn}^{n*}\right);$ Wherein, P _c2, P _s2be respectively the cosine and sinusoidal component amplitude that exchange active power, with be respectively the instruction of synchronous rotating frame positive sequence d shaft current, the instruction of positive sequence q shaft current, the instruction of negative phase-sequence d shaft current and the instruction of negative phase-sequence q shaft current; with be respectively the instruction of synchronous rotating frame positive sequence d shaft voltage, the instruction of positive sequence q shaft voltage, the instruction of negative phase-sequence d shaft voltage and the instruction of negative phase-sequence q shaft voltage;

According to the permission fluctuation maximum amplitude of given current transformer DC bus-bar voltage and formula (1):

${\mathrm{\ΔU}}_{dc}\≤U_{dc}^{*}-\sqrt{-\frac{\sqrt{{P_{c2}}^2+{P_{s2}}^2}}{{\mathrm{\ω}}_{1}C}+U_{dc}^{*2}}---\left(2\right);$

Will $P_{c2}=u_{gdn}^n\left(i_{gdp}^{p*}\right)+u_{gdp}^p\left(i_{gdn}^{n*}\right)$ With $P_{s2}=u_{gdn}^n\left(i_{gqp}^{p*}\right)-u_{gdp}^p\left(i_{gqn}^{n*}\right)$ Bring formula (2) into, the constraints obtaining positive sequence reactive-current compensation is:

5) current transformer grid-connected current maximum amplitude in synchronous dq rotating coordinate system is made to be I _{n_dq}, solve inequation according to capacity limit obtain numerical intervals be wherein N is positive rational number or irrational number;

6) according to formula (3), positive sequence q shaft current command quantity in synchronous rotating frame is asked for numerical intervals, determine this command quantity by output maximum inductive idle or that minimum perception of dissolving is idle principle;

7) under synchronous rotating frame, positive-negative sequence current governing equation is provided by formula (4), formula (5):

$\left\{\begin{array}{c}{v}_{con\_dp}^p=(-u_{con\_dp}^{p^{\′}}+{\mathrm{\Δu}}_{con\_dp}^p)K\\ v_{con\_qp}^p=(-u_{con\_qp}^{p^{\′}}+{\mathrm{\Δu}}_{con\_qp}^p)K\end{array}\right.---\left(4\right)$

$\left\{\begin{array}{c}{v}_{con\_dn}^n=(-u_{con\_dn}^{n^{\′}}+{\mathrm{\Δu}}_{con\_dn}^n)K\\ v_{con\_qn}^n=(-u_{con\_qn}^{n^{\′}}+{\mathrm{\Δu}}_{con\_qn}^n)K\end{array}\right.---\left(5\right)$

In formula:

$u_{con\_dp}^{p^{\′}}={\mathrm{Ri}}_{gdp}^p+L\frac{{\mathrm{di}}_{gdp}^p}{dt},$

$u_{con\_qp}^{p^{\′}}={\mathrm{Ri}}_{gqp}^p+L\frac{{\mathrm{di}}_{gqp}^p}{dt},$

${\mathrm{\Δu}}_{con\_dp}^p={\mathrm{\ω}}_1{\mathrm{Li}}_{gqp}^p+u_{gqp}^p,$

${\mathrm{\Δu}}_{con\_qp}^p=-{\mathrm{\ω}}_1{\mathrm{Li}}_{gdp}^p+u_{gdp}^p,$

$u_{con\_dn}^{n^{\′}}={\mathrm{Ri}}_{gdn}^n+L\frac{{\mathrm{di}}_{gdn}^n}{dt},$

$u_{con\_qn}^{n^{\′}}={\mathrm{Ri}}_{gqn}^n+L\frac{{\mathrm{di}}_{gqn}^n}{dt},$

${\mathrm{\Δu}}_{con\_dn}^n=-{\mathrm{\ω}}_1{\mathrm{Li}}_{gqn}^n+u_{gqn}^n,$

${\mathrm{\Δu}}_{con\_qn}^n={\mathrm{\ω}}_1{\mathrm{Li}}_{gdn}^n+u_{gdn}^n.$

In formula, u represents voltage, Δ u represents electric voltage feed forward item, in its subscript " ' " represent that this voltage is voltage control item, in its subscript, " con " represents current transformer output valve, d, q in its subscript represent synchronous rotating frame d axle, synchronous rotating frame q axle respectively, and p, n in subscript represent positive sequence component, negative sequence component respectively, and p, n in subscript represent that this component is positioned at positive sequence synchronous rotating frame, negative phase-sequence synchronous rotating frame respectively; r represents grid-connected line resistance, and L represents grid-connected line inductance;

8) according to formula (4), formula (5) analytical expression, by the pi regulator G of each dq axle of positive-negative sequence _pIs () carries out closed-loop control, obtain the control voltage of each d, q axle of positive-negative sequence with

By the calculating of positive-negative sequence each dq axle control voltage and feedforward term, and be multiplied by DC bus-bar voltage coefficient of variation K and correct, obtain the current transformer output voltage of each dq axle of positive-negative sequence with

By two-phase rotating coordinate system-two-phase rest frame coordinate transform, obtain the component of current transformer positive-negative sequence output voltage in α, β rest frame respectively with wherein, subscript α, β represents that this component is positioned at α, β rest frame respectively;

By the synthesis of α, β axle positive-negative sequence output voltage, obtain grid-connected converter output voltage space vector, and carry out pulse-width modulation.

3. grid-connected converter negative-sequence current according to claim 2 compensation method, is characterized in that, the transfer function of notch filter is wherein Q is quality factor, ω ₁for line voltage synchro angle frequency.

4. grid-connected converter negative-sequence current according to claim 2 compensation method, is characterized in that, step 3) in,

Pass through formula calculate synchronous rotating frame positive sequence d shaft current command quantity

5. grid-connected converter negative-sequence current according to claim 2 compensation method, is characterized in that, step 6) in, if obtain according to formula (3) numerical intervals expression formula is then set positive sequence q shaft current command quantity

If obtain according to formula (3) numerical intervals expression formula is a, B are positive rational number or irrational number, then set positive sequence q shaft current command quantity and [-N, N] ∩ { [-∞, A] ∪ [B ,+∞] } for nonvoid set and.