CN110417055A - A Direct Power Control Method for Suppressing DC-side Bus Voltage Fluctuation of Photovoltaic Grid-connected Inverters - Google Patents

Abstract

The invention discloses a direct power control method for suppressing the voltage fluctuation of the DC side busbar of a photovoltaic grid-connected inverter, which belongs to the technical field of converter control; the method includes the following steps: establishing a photovoltaic power generation system, and determining the instantaneous active power component v _α of the power grid , i _α and instantaneous reactive components v _β , i _β , use the fixed-step disturbance observation method to realize the maximum power point tracking of the photovoltaic array, and determine the disturbance power through the disturbance observer and the correction link The output signals of the two PI controllers The feedforward decoupling model is constructed as the input of the feedforward decoupling controller, based on the grid voltage v _α , v _β , combined with the output u _P , u _Q of the feedforward decoupling system, the voltage control signals e _α and e are obtained _β , carry out αβ/abc transformation on the voltage control signals e _α and e _β , and obtain the SPWM control signals e _a,b,c of the inverter. It can ensure the zero-steady-state error tracking of the DC bus voltage; it does not need to obtain the phase information of the grid voltage, and does not need to perform synchronous rotation coordinate transformation, thus avoiding the stability problem caused by the use of a phase-locked loop (PLL). .

Description

A direct power control method for suppressing the voltage fluctuation of the DC side bus of photovoltaic grid-connected inverter method

technical field

The invention belongs to the technical field of converter control, and in particular relates to a direct power control method for suppressing voltage fluctuations of a DC side busbar of a photovoltaic grid-connected inverter.

Background technique

With the rapid development of renewable energy technologies such as wind power and solar power generation, the control of photovoltaic grid-connected inverters has become a research hotspot. As an interface device between renewable energy and the grid, the control performance of the inverter directly affects the grid-connected power quality and grid-connected efficiency.

The photovoltaic inverter is in the state of grid-connected operation, and the DC side bus voltage is easily affected by active power fluctuations. In order to realize sinusoidal inverter, the DC bus voltage must be controlled within a reasonable range and kept relatively stable. If the DC bus voltage is too high, it will trigger the action of the protection device; if it is too low, the power will flow from the grid side to the DC side, and the sinusoidal inverter cannot be realized. It can be seen that the DC bus voltage control technology plays an important role in ensuring the power quality and the safe and stable operation of the power grid. At present, for the control of photovoltaic grid-connected inverters, a double closed-loop structure of voltage outer loop and current inner loop is generally adopted. In the double closed-loop structure, the outer loop controls the bus voltage through the PI regulator, and the inner loop is used to track the output current command of the outer loop. According to the theory of instantaneous power, there is only a voltage coefficient difference between current and power. In essence, the control of grid-connected current is equivalent to the control of output power. Based on this, some scholars have used the basic idea of direct torque control in motor drive theory to propose a method of direct power control for inverters or rectifiers. This method uses the power inner loop instead of the current inner loop, which has high power factor and simple structure. Etc.

When there are disturbances in the photovoltaic inverter system, such as changes in light intensity, in order to improve the control performance of the bus voltage and suppress its fluctuations, scholars have proposed a method of applying feedforward correction in the voltage outer loop. This method requires additional sensors to obtain The related information of DC power supply and load increases the cost of system design and use. Subsequently, some scholars proposed a control method based on the extended state observer. Compared with the traditional method, this method does not need to directly measure the disturbance current, and can suppress the influence of external disturbances on the system. It has strong robustness. However, this method uses a proportional resonant controller in the inner loop, which needs to convert the power reference into a corresponding current reference, and then control the current, which increases the computational burden of the system. In addition, some scholars have proposed a control strategy based on a nonlinear disturbance observer for the AC-DC hybrid microgrid. It has been proved by practice that the observer has good dynamic quality.

Contents of the invention

According to the problems existing in the prior art, the present invention discloses a direct power control method for suppressing fluctuations in busbar voltage on the DC side of a photovoltaic grid-connected inverter, including the following steps:

S1: Establish a photovoltaic power generation system, the photovoltaic power generation system includes a photovoltaic array, a boost boost circuit, an inverter, a filter inductor, an MPPT controller, a control system, and a power grid, and between the photovoltaic array and the boost boost circuit and the boost The voltage circuit and the inverter are connected through a capacitor; the input end of the MPPT controller is connected with the photovoltaic array, and the output end of the MPPT controller is connected with the boost boost circuit; the input end of the control system is connected with the The grid is connected, and the output terminal of the control system is connected with the inverter;

S2: use the voltage sensor to detect the voltage U _pv of the photovoltaic array, the DC bus voltage U _dc and the grid voltage v _a,b,c , use the current sensor to detect the output current I _pv of the photovoltaic array and the grid side current i _a,b,c , Perform abc/αβ transformation on the three-phase voltage and three-phase current respectively to obtain the instantaneous active components v _α , i _α and instantaneous reactive components v _β , i _β on the αβ axis;

S3: Using the fixed-step perturbation observation method, changing the output voltage of the photovoltaic array by changing the duty cycle of the switching tube, and performing maximum power point tracking of the photovoltaic array;

S4: Calculate the grid-connected active power P _g and grid-connected reactive power Q _g according to the instantaneous active components v _α , i _α and instantaneous reactive components v _β , i _β , based on the square of the DC bus voltage and the grid-connected active power P _g , the disturbance power is obtained through the nonlinear disturbance observer After multiplying it with the correction link G _ch (s), the corrected disturbance power is obtained

S5: the square of the DC bus voltage detection value and the square of the given value of the DC bus voltage After making a difference, get the error control signal The error signal e _dc is closed-loop processed by the voltage outer loop P regulator, and the output of the voltage outer loop P regulator and the disturbance power Add up to get the inverter active power given value

S6: Set the given active power The difference from the subtraction of the output active power _Pg , the given reactive power The difference signal subtracted from the output reactive power _Qg is respectively used as the input of the inner loop active PI controller and the inner loop reactive PI controller to obtain the output signal Among them, set the instantaneous reactive power reference output by the grid-connected inverter

S7: the output signal of above-mentioned inner loop active PI controller and inner loop reactive PI controller The feedforward decoupling model is constructed as the input signal of the feedforward decoupling controller, based on the grid voltage v _α , v _β , combined with the output u _P , u _Q of the feedforward decoupling system, the voltage control signals e _α and _eβ ;

S8: Perform αβ/abc transformation on the voltage control signals e _α and e _β to obtain the SPWM control signals e _a , e _b , and e _c of the inverter.

Further, the disturbance power is obtained by the nonlinear disturbance observer process, including the following steps:

S4-1: The dynamic equation of the active power consumed by the DC bus capacitors C and R _l and the grid-connected active power P _g is:

Among them: C is the DC bus capacitance, U _dc is the DC bus voltage, R _l is the loss of the subsequent inverter, P _s is the DC power flowing through the boost circuit, P _g is the grid-connected active power, and Q _g is the grid-connected active power. Grid reactive power;

S4-2: the above formula (1) is rewritten into the following form:

Among them: x ₁ and x ₂ are state variables, the control input is u _P =v _α e _α +v _β e _β , P _s is defined as the disturbance variable;

S4-3: The nonlinear disturbance observer for estimating the external disturbance d(t) can be described by the following equation:

Among them: z is the intermediate state quantity of the nonlinear disturbance observer, is the estimated value of the disturbance variable, the gain of the nonlinear disturbance observer is l(x)=[l ₁ l ₂ ], where l ₁ and l ₂ represent the gain of the nonlinear disturbance observer, and p(x) is the observation to be designed Function, can be expressed as: p(x)=l ₁ x ₁ +l ₂ x ₂ ;

S4-4: Taking observer gain l ₁ >0, l ₂ =0, the above formula (3) can be written as:

in: is the estimated value of the disturbance variable P _s .

Further, the disturbance observer observed value There is the following relationship with the real value P _s :

Among them: To _b is the time constant of the nonlinear disturbance observer, and its value is equal to C/2l ₁ .

Furthermore, the given value of active power Calculated by the following formula (6):

Among them: K _p is the gain of the voltage outer loop P regulator, e _dc is the error control signal, and its value is equal to G _ch (s) is the transfer function of the observation error correction link;

Among them: T _ch is the differential time constant.

Further, the input of the feed-forward decoupling controller Calculated by the following formula (8):

Among them: K _P,p is the proportional gain of the active power inner loop PI regulator, K _P,i is the integral gain of the active power inner loop PI regulator, K _Q,p is the proportional gain of the reactive power inner loop PI regulator , K _Q,i is the integral gain of the reactive power inner-loop PI regulator, e _P is the active power regulation error, and e _Q is the reactive power regulation error, calculated by the following formula (9):

in: It is the given value of reactive power, its value is 0.

Further, the output signals u _P and u _Q of the feedforward decoupling controller are calculated by the following formula (10):

or expressed as:

Among them: ed and _{e q} are the components of the inverter output voltage on the dq axis.

Further, the control signals e _α and e _β are calculated by the following formula (12):

Among them: u _P , u _Q are the output signals of the feedforward decoupling controller, v _α , v _β are the components of the grid voltage on the αβ axis, and V _g is the amplitude of the three-phase balanced grid voltage.

Further, the SPWM control signals e _a , e _b , e _c are calculated by the following formula (13):

The direct power control method provided by the present invention for suppressing the voltage fluctuation of the DC side busbar of the photovoltaic grid-connected inverter obtains the DC busbar voltage and grid side power through sampling, and uses a nonlinear disturbance observer to realize fast tracking of the disturbance quantity; The invention introduces the feed-forward disturbance in the voltage outer loop and adopts a simple proportional controller to ensure zero steady-state error tracking of the DC bus voltage; the invention adopts a direct power control method based on grid voltage modulation, which can control the grid side Perform real-time control, realize the rapid balance of DC source input power and AC output power, and reduce the amplitude of bus voltage fluctuations; the invention does not need to obtain phase information of grid voltage, and does not need to perform synchronous rotation coordinate transformation, thereby avoiding the Stability issues caused by the use of phase-locked loops (PLLs).

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application or in the prior art, the accompanying drawings that need to be used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the accompanying drawings in the following description are only These are some embodiments described in this application. Those skilled in the art can also obtain other drawings based on these drawings without creative work.

Figure 1 is a schematic diagram of the traditional photovoltaic grid-connected inverter control scheme;

Fig. 2 is a structural representation of the present invention;

Fig. 3 is a schematic diagram of the control scheme of the photovoltaic grid-connected inverter of the present invention;

Figure 4(a) is the waveform diagram of the output power of the photovoltaic panel when the light intensity changes in 4s;

Figure 4(b) is the waveform diagram of the output voltage of the photovoltaic panel when the light intensity changes in 4s;

Figure 4(c) is the output current waveform diagram of the photovoltaic panel when the light intensity changes in 4s;

Figure 5(a) is the simulated waveform diagram of the DC side bus voltage of the photovoltaic grid-connected inverter using the traditional control method when the light intensity changes in 4s;

Figure 5(b) is the simulated waveform diagram of the grid-connected voltage and current of the photovoltaic grid-connected inverter using the traditional control method when the light intensity changes in 4s;

Figure 5(c) is the simulated waveform diagram of the grid-connected power of the photovoltaic grid-connected inverter using the traditional control method when the light intensity changes in 4s;

Fig. 6 (a) is 4s, when the illumination intensity changes, the simulation waveform diagram of the DC side bus voltage of the photovoltaic grid-connected inverter adopting the control method of the present invention;

Fig. 6(b) is 4s, when the illumination intensity changes, the grid-connected voltage and current simulation waveform diagram of the photovoltaic grid-connected inverter adopting the control method of the present invention;

Fig. 6 (c) is 4s, when the illumination intensity changes, the grid-connected power simulation waveform diagram of the photovoltaic grid-connected inverter adopting the control method of the present invention;

Figure 7(a) is 4s, when the light intensity changes, and when the filter inductance changes from 23mH to 18mH, other parameters remain unchanged, the simulated waveform diagram of the DC side bus voltage of the photovoltaic grid-connected inverter using the traditional control method;

Figure 7(b) shows that when the light intensity changes at 4s and the filter inductance changes from 23mH to 18mH, other parameters remain unchanged, and the grid-connected voltage and current simulation waveform diagram of the photovoltaic grid-connected inverter adopts the traditional control method;

Figure 7(c) is 4s, when the light intensity changes, and when the filter inductance changes from 23mH to 18mH, other parameters remain unchanged, and the grid-connected power simulation waveform diagram of the photovoltaic grid-connected inverter adopts the traditional control method;

Fig. 8 (a) is that the output power of the photovoltaic panel is constant, and in 10s, the grid voltage suddenly rises by 10%, and other parameters remain unchanged, and the simulation waveform diagram of the DC side bus voltage of the photovoltaic grid-connected inverter adopting the control method of the present invention;

Fig. 8 (b) is the photovoltaic panel output power constant, 10s time, grid voltage rises 10% sharply, other parameters remain unchanged, the grid-connected voltage and current simulation waveform diagram of the photovoltaic grid-connected inverter adopting the control method of the present invention;

Fig. 8(c) is a simulation waveform diagram of the photovoltaic grid-connected inverter grid-connected power using the control method of the present invention when the output power of the photovoltaic panel is constant.

Detailed ways

In order to describe the present invention more specifically, the direct power control method of the present invention for suppressing the voltage fluctuation of the DC-side bus of the photovoltaic grid-connected inverter will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

Fig. 1 is a schematic diagram of a control scheme of a traditional photovoltaic grid-connected inverter, Fig. 2 is a schematic structural diagram of the present invention, and Fig. 3 is a schematic diagram of a control scheme of a photovoltaic grid-connected inverter of the present invention; A direct power control method for side bus voltage fluctuations, comprising the following steps:

S1: Establish a photovoltaic power generation system, the photovoltaic power generation system includes a photovoltaic array, a boost boost circuit, a 17kW grid-connected inverter, a filter inductor, an MPPT controller, a control system and a power grid, the photovoltaic array and a boost boost circuit and between the boost circuit and the inverter are connected through a capacitor; the input end of the MPPT controller is connected with the photovoltaic array, and the output end of the MPPT controller is connected with the boost boost circuit; the control The input end of the system is connected to the grid, and the output end of the control system is connected to the inverter; the photovoltaic array parameters are set to V _oc =450V, I _sc =60A, V _mpp =350V at the maximum power point, I _mpp = 45A.

S2: Use the Hall voltage sensor to collect the output voltage U _pv of the photovoltaic array, the DC bus voltage U _dc and the voltage v _a,b,c of the grid, and use the Hall current sensor to collect the output current I _pv of the photovoltaic array and the grid side current i _a,b,c , carry out abc/αβ transformation on the three-phase balanced grid voltage and three phases, and obtain the instantaneous active components v _α , i _α and instantaneous reactive components v _β , i _β on the αβ axis; the αβ coordinate transformation matrix is as follows :

The expression of the three-phase balanced grid voltage in the αβ coordinate system is:

Where: V _g is the amplitude of the three-phase balanced grid voltage, ω is the angular frequency of the grid voltage; in this embodiment, the effective value of the three-phase balanced grid voltage is 220V, ω=2πf, f=50Hz, and V _g is 179.6V .

S3: Use the perturbation and observation method with a fixed step to track the maximum power point of the photovoltaic array, and the sampling period T _a of the MPPT algorithm is calculated by the following formula (3):

Among them: L ₀ is the boost inductance value, C ₀ is the filter capacitance value of the boost circuit, R _L is the parasitic resistance on the inductor, k is the ratio of the current change rate to the voltage change rate, it can be assumed that in the constant voltage source area, k <<-1, in the constant current source region, k≈0; in this embodiment, L ₀ is 5mH, C ₀ is 550μF, R _L is 300Ω, k is 0, the disturbance step is 5×10 ^-4 , and the sampling The period is 1.67×10 ^-4 s.

S4: Calculate the instantaneous active power P and instantaneous reactive power Q by the following formula:

Among them: i _α and i _β are grid side current after coordinate transformation.

Neglecting the resistance value of the filter inductor, it can be expressed as:

Among them: L is the filter inductance value, e _α , e _β are the αβ components of the inverter output voltage.

Based on the square of the DC bus voltage and the grid-connected active power P _g , the disturbance power is obtained through the disturbance observer After multiplying it with the correction link G _ch (s), the corrected disturbance power is obtained Calculated by a disturbance observer The following steps:

S4-1: First, the dynamic equation of the active power consumed by the bus capacitors C and _Rl and the grid-connected active power is:

S4-2: where: C is the DC bus capacitor, U _dc is the DC bus voltage, R _l is the loss of the subsequent inverter, P _s is the DC power flowing through the boost circuit, and P _g is the grid-connected active power; In this embodiment, C is 3300 μF, and R ₁ is 1000 Ω;

Furthermore, the above formula (6) can be written as follows:

Where: x ₁ and x ₂ are state variables, u _P is the control input, and P _s is the disturbance; in this embodiment, L is 23mH.

S4-3: The nonlinear disturbance observer for estimating the external disturbance d(t) can be described by the following equation:

Among them: z is the intermediate state quantity of the observer, is the estimated value of the disturbance variable, the observer gain is l(x)=[l ₁ l ₂ ], p(x) is the observation function to be designed, which can be expressed as: p(x)=l ₁ x ₁ +l _{2 x2} ;

S4-4: Taking the observer gain l ₁ >0, l ₂ =0, the expression (9) of the nonlinear disturbance observer is:

in: is the estimated value of the disturbance variable P _s .

Further, the disturbance observer observed value There is the following relationship with the real value P _s :

Among them: T _ob is the time constant of the nonlinear disturbance observer, and its value is equal to C/2l ₁ .

S5: the square of the DC bus voltage detection value and the square of the given value of the DC bus voltage After making a difference, get the error control signal The error signal e _dc is closed-loop processed by the P regulator, and the output of the P regulator and the disturbance power Add up to get the inverter active power given value The given value of active power P ^* is calculated by the following formula (11):

Among them: K _p is the gain of the voltage outer loop P regulator, e _dc is the error control signal, and its value is equal to _Gch (s) is the transfer function of the observation error correction link; in the present embodiment, _Kp is taken as 0.5, The transfer function of the correction link G _ch (s)=0.05s+1.

The G _ch (s) is calculated by the following formula (12):

Among them: K _P,p , K _P,i are the proportional and differential gains of the active power inner loop PI regulator, respectively.

Described G _ch (s) expression can be simplified as:

Among them: T _ch is the differential time constant.

S6: Set the given active power The difference from the subtraction of the output active power _Pg , the given reactive power The difference signal subtracted from the output reactive power _Qg is used as the input of the inner loop active PI controller and the inner loop reactive PI controller respectively, and the output signal is obtained Among them, set the instantaneous reactive power reference output by the grid-connected inverter

S7: the output signal of above-mentioned inner loop active PI controller and inner loop reactive PI controller As the input signal of the feedforward decoupling controller to construct the feedforward decoupling model, the input of the feedforward decoupling controller Calculated by the following formula (14):

Among them: e _P and e _Q are power adjustment errors, calculated by the following formula (15):

Where: K _P,p , K _P,i , K _Q,p , K _Q,i and The values of are 40, 19893, 40, 19893 and 0 respectively.

S7: Based on the grid voltage v _α , v _β , combined with the output u _P , u _Q of the feedforward decoupling system, the voltage control signals e _α and e _β are obtained; the outputs u _P , u _Q of the feedforward decoupling controller pass through The following formula (16) calculates:

in: Input for the feed-forward decoupling controller.

Further: the outputs u _P and u _Q of the feedforward decoupling controller can also be expressed as:

Among them: ed and _{e q} are the components of the inverter output voltage on the dq axis.

The control signals e _α and e _β are calculated by the following formula (18):

Among them: u _P , u _Q are the outputs of the feedforward decoupling controller, v _α , v _β are the components of the grid voltage on the αβ axis.

S8: Perform αβ/abc transformation on the voltage control signals u _α and u _β to obtain the SPWM signal of the inverter, and then control the switching devices in the grid-connected inverter. The αβ/abc transformation matrix is T _abc/αβ inverse matrix.

In the following, we simulate the photovoltaic grid-connected inverter adopting this embodiment.

Figure 4(a) is the waveform diagram of the output power of the photovoltaic panel when the light intensity changes in 4s; Figure 4(b) is the waveform diagram of the output voltage of the photovoltaic panel when the light intensity changes in 4s; Figure 4(c) is the waveform diagram of the photovoltaic panel output voltage in 4s , the light intensity changes, and the output current waveform of the photovoltaic panel; at 4s, the light intensity changes, and the output power of the photovoltaic panel changes from 8kW to 16kW;

Fig. 5(a) is 4s, when the light intensity changes, the simulation waveform diagram of the DC side bus voltage of the photovoltaic grid-connected inverter using the traditional control method; Fig. 5(b) is 4s, the light intensity changes, using the traditional control method The grid-connected photovoltaic inverter grid-connected voltage and current simulation waveform diagram of the method; Fig. 5(c) is the simulation waveform diagram of the photovoltaic grid-connected inverter grid-connected power using the traditional control method when the light intensity changes in 4s;

When Fig. 6 (a) is 4s, the light intensity changes, and the simulation waveform diagram of the DC side bus voltage of the photovoltaic grid-connected inverter adopting the control method of the present invention; when Fig. 6 (b) is 4s, the light intensity changes, and this The grid-connected photovoltaic inverter grid-connected voltage and current simulation waveform diagram of the control method of the invention; Figure 6 (c) is 4s, when the light intensity changes, the grid-connected photovoltaic inverter grid-connected power simulation waveform using the control method of the present invention picture;

When the light intensity changes and there is a step disturbance in the system, the traditional voltage and current double closed-loop control strategy is adopted, and the bus voltage fluctuates in a large range. Compared with this embodiment, there is a serious overshoot and the convergence speed is slow; In the control method proposed by the invention, there is about 110V overshoot in the bus voltage, and the steady state can be reached after only 0.8s.

Figure 7(a) is 4s, when the light intensity changes, and when the filter inductance changes from 23mH to 18mH, other parameters remain unchanged, and the simulation waveform diagram of the DC side bus voltage of the photovoltaic grid-connected inverter using the traditional control method; Figure 7( b) When it is 4s, the light intensity changes, and when the filter inductance changes from 23mH to 18mH, other parameters remain unchanged, and the grid-connected voltage and current simulation waveform of the photovoltaic grid-connected inverter using the traditional control method; Figure 7(c) When the light intensity is 4s, the light intensity changes, and when the filter inductance changes from 23mH to 18mH, other parameters remain unchanged. The grid-connected power simulation waveform of the photovoltaic grid-connected inverter using the traditional control method; it can be seen that changing the filter inductance value, other The parameters remain unchanged, the response speed of the system becomes slower and the time required to reach a steady state becomes longer when the control method proposed by the present invention is adopted, but the overall performance does not change significantly.

Fig. 8 (a) is the output power of photovoltaic panel is constant, when 10s, grid voltage rises 10% suddenly, other parameters remain unchanged, adopts the photovoltaic grid-connected inverter DC side bus voltage simulation wave form of the control method of the present invention; Fig. 8 ( b) The output power of the photovoltaic panel is constant. In 10s, the grid voltage suddenly rises by 10%, and other parameters remain unchanged. The grid-connected voltage and current simulation waveform diagram of the photovoltaic grid-connected inverter adopting the control method of the present invention; FIG. 8(c) The output power of the photovoltaic panel is constant. In 10s, the grid voltage rises sharply by 10%, and other parameters remain unchanged. The simulation waveform diagram of the grid-connected power of the photovoltaic grid-connected inverter adopting the control method of the present invention shows that the output power of the photovoltaic panel is constant. In 10s, the grid voltage suddenly rises by 10%, and other parameters remain unchanged. With the control method proposed in the present invention, there is a slight overshoot in the bus voltage and active power. After the grid voltage stabilizes, the system can quickly reach a stable state.

To sum up, this embodiment does not need to obtain the phase information of the power grid, nor does it need to perform synchronous rotation coordinate transformation. It can realize the fast tracking of the interference quantity, and has strong robustness to uncertain disturbance and parameter changes; the direct power control method based on the grid voltage modulation can be used to control the power of the grid side in real time, and realize the input power of the DC source. The rapid balance of AC and AC output power effectively suppresses the fluctuation of DC bus voltage.

Claims (8)

1. a kind of direct Power Control method for inhibiting the fluctuation of photovoltaic combining inverter DC side busbar voltage, it is characterised in that: Include the following steps:

S1: establishing photovoltaic generating system, and the photovoltaic generating system includes photovoltaic array, boosting boost circuit, inverter, filter Wave inductance, MPPT controller, control system and power grid, the photovoltaic array and boosting boost circuit between and booster circuit Pass through capacitance connection between inverter；The input terminal of the MPPT controller is connected with photovoltaic array, the MPPT control The output end of device is connected with boosting boost circuit；The input terminal of the control system is connected with power grid, the control system Output end be connected with inverter；

S2: the voltage U of voltage sensor detection photovoltaic array is utilized_pv, DC bus-bar voltage U_dcWith network voltage v_a,b,c, utilize The output electric current I of current sensor detection photovoltaic array_pvWith current on line side i_a,b,c, respectively to three-phase voltage and three-phase current into Row abc/ α β transformation, obtains the instantaneous active component v on α β axis_α、i_αWith instantaneous reactive component v_β、i_β；

S3: change the output electricity of photovoltaic array using fixed step size perturbation observation method, by changing the duty ratio of switching tube Pressure, and carry out the MPPT maximum power point tracking of photovoltaic array；

S4: according to instantaneous active component v_α、i_αWith instantaneous reactive component v_β、i_β, calculate grid-connected active-power P_gWith grid-connected idle function Rate Q_g, square based on DC bus-bar voltageWith grid-connected active-power P_g, disturbance function is obtained by nonlinear disturbance observer RateBy itself and amendment link G_ch(s) after being multiplied, revised power of disturbance is obtained

S5: by square of DC bus-bar voltage detected valueWith square of DC bus-bar voltage given valueAfter making difference, obtain Error controling signalBy outer voltage P adjuster to error signal e_dcClosed-loop process is carried out, by voltage Outer ring P adjuster output quantity and power of disturbanceIt is added, obtains inverter active power given value

S6: by given active powerWith active power of output P_gDifference, the given reactive power subtracted each otherWith the idle function of output Rate Q_gThe difference signal subtracted each other obtains output letter respectively as the input of the active PI controller of inner ring and the idle PI controller of inner ring NumberWherein, the instantaneous reactive power reference that setting gird-connected inverter exports

S7: by the output signal of the active PI controller of above-mentioned inner ring and the idle PI controller of inner ringIt is solved respectively as feedforward The input signal of coupling controller constructs Feedforward Decoupling model, is based on network voltage v_α、v_β, in conjunction with the output of Feedforward Decoupling system u_P、u_Q, obtain voltage control signal e_αAnd e_β；

S8: to voltage control signal e_αAnd e_βα β/abc transformation is carried out, the SPWM control signal e of inverter is obtained_a、e_b、e_c。

2. the method according to claim 1, wherein obtaining power of disturbance by nonlinear disturbance observerIt crosses Journey, comprising the following steps:

S4-1: dc-link capacitance C and R_lThe active power of consumption and grid-connected active-power P_gDynamical equation are as follows:

Wherein: C is dc-link capacitance, U_dcFor DC bus-bar voltage, R_lIndicate the loss of rear class inverter, P_sTo flow through boosting The dc power of circuit, P_gFor grid-connected active power, Q_gFor simultaneously network reactive power；

S4-2: above formula (1) is rewritten into following form:

Wherein: x₁And x₂For state variable, control input quantity is u_P=v_αe_α+v_βe_β, P_sIt is defined as disturbance variable；

S4-3: the nonlinear disturbance observer of estimation external disturbance d (t) can be used following equation to describe:

Wherein: z is nonlinear disturbance observer intermediate state amount,For the estimated value of disturbance variable, nonlinear disturbance observer Gain is l (x)=[l₁ l₂], wherein l₁、l₂Indicate the gain of nonlinear disturbance observer, p (x) is the observation letter for needing to design Number, may be expressed as: p (x)=l₁x₁+l₂x₂；

S4-4: observer gain l is taken₁> 0, l₂=0, above formula (3) is writeable are as follows:

Wherein:For disturbance variable P_sEstimated value.

3. the method according to claim 1, wherein the disturbance observer observationWith true value P_sBetween There are following relationships:

Wherein: To_bFor the time constant of nonlinear disturbance observer, value is equal to C/2l₁。

4. the method according to claim 1, wherein active power given valueIt is calculated by following formula (6):

Wherein: K_pFor the gain of outer voltage P adjuster, e_dcFor error controling signal, value is equal toG_ch (s) transmission function of link is corrected for observation error；

Wherein: T_chFor derivative time constant.

5. the method according to claim 1, wherein the input of feedforward decoupling controller Pass through following formula (8) It calculates:

Wherein: K_P,pFor the proportional gain of active power inner ring pi regulator, K_P,iFor the integral of active power inner ring pi regulator Gain, K_Q,pFor the proportional gain of reactive power inner ring pi regulator, K_Q,_iFor the integral gain of reactive power inner ring pi regulator, e_PFor active power regulation error, e_QError is adjusted for reactive power, is calculated by following formula (9):

Wherein:For reactive power given value, value 0.

6. the method according to claim 1, wherein the output signal u of the feedforward decoupling controller_P、u_QPass through Following formula (10) calculates:

Or it indicates are as follows:

Wherein: e_d、e_qFor component of the inverter output voltage on dq axis.

7. the method according to claim 1, wherein control signal e_α、e_βIt is calculated by following formula (12):

Wherein: u_P、u_QFor the output signal of feedforward decoupling controller, v_α、v_βFor component of the network voltage on α β axis, V_gFor three-phase Balance the amplitude of network voltage.

8. the method according to claim 1, wherein SPWM controls signal e_a, e_b, e_cIt is calculated by following formula (13):