CN110417055B - Direct power control method for inhibiting voltage fluctuation of direct-current side bus of photovoltaic grid-connected inverter - Google Patents
Direct power control method for inhibiting voltage fluctuation of direct-current side bus of photovoltaic grid-connected inverter Download PDFInfo
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- CN110417055B CN110417055B CN201910701707.8A CN201910701707A CN110417055B CN 110417055 B CN110417055 B CN 110417055B CN 201910701707 A CN201910701707 A CN 201910701707A CN 110417055 B CN110417055 B CN 110417055B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
- H02J3/48—Controlling the sharing of the in-phase component
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
- H02J3/50—Controlling the sharing of the out-of-phase component
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/50—Photovoltaic [PV] energy
- Y02E10/56—Power conversion systems, e.g. maximum power point trackers
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Abstract
The invention discloses a direct power control method for inhibiting voltage fluctuation of a bus on the direct current side of a photovoltaic grid-connected inverter, belonging to the technical field of converter control; the method comprises the following steps: establishing a photovoltaic power generation system and determining the instantaneous active component v of the power grid α 、i α And a transient reactive component v β 、i β The maximum power point tracking of the photovoltaic array is realized by adopting a fixed step length disturbance observation method, and the disturbance power is determined through a disturbance observer and a correction link
Output signals of two PI controllers
Respectively used as the input of a feedforward decoupling controller to construct a feedforward decoupling model based on the voltage v of the power grid α 、v β Combined with the output u of the feedforward decoupling system P 、u Q To obtain a voltage control signal e α And e β For voltage control signal e α And e β Carrying out alpha beta/abc conversion to obtain SPWM control signal e of the inverter a,b,c The feedforward disturbance quantity is introduced into the voltage outer ring, and the zero steady-state error tracking of the direct-current bus voltage can be ensured by adopting a simple proportional controller; the phase information of the power grid voltage does not need to be acquired, and synchronous rotating coordinate transformation does not need to be carried out, so that the stability problem caused by using a phase-locked loop (PLL) is avoided.
Description
Technical Field
The invention belongs to the technical field of converter control, and particularly relates to a direct power control method for inhibiting voltage fluctuation of a direct-current side bus of a photovoltaic grid-connected inverter.
Background
With the rapid development of renewable energy technologies such as wind power, solar power generation and the like, the control of the photovoltaic grid-connected inverter becomes a research hotspot. The inverter is used as an interface device between renewable energy and a power grid, and the control performance of the inverter directly influences the grid-connected electric energy quality and the grid-connected efficiency.
The photovoltaic inverter is in a grid-connected operation state, and the direct-current side bus voltage is easily influenced by active power fluctuation. In order to achieve sinusoidal inversion, the dc bus voltage must be controlled within a reasonable range and remain relatively stable. When the voltage of the direct current bus is too high, the protection device can be triggered to act; too low will result in power flowing from the grid side to the dc side and no sinusoidal inversion can be achieved. Therefore, the direct current bus voltage control technology plays an important role in ensuring the electric energy quality and the safe and stable operation of the power grid. At present, for the control of a photovoltaic grid-connected inverter, a double closed-loop structure of a voltage outer loop and a current inner loop is generally adopted. In the double closed loop structure, the outer loop controls the bus voltage through a PI regulator, and the inner loop is used for tracking an output current instruction of the outer loop. According to the instantaneous power theory, only one voltage coefficient is different between current and power, and the control on grid-connected current is basically equal to the control on output power. Based on this, the students use the basic idea of direct torque control in the motor driving theory for reference, and propose a method for directly controlling the power of the inverter or the rectifier.
When disturbance exists in the photovoltaic inverter system, for example, the illumination intensity changes, in order to improve the control performance of the bus voltage and inhibit fluctuation of the bus voltage, a method for applying feed-forward correction in the voltage outer loop is provided by a scholars, an additional sensor is required to be added to obtain related information of a direct-current power supply and a load, and the system design and use cost is increased. Subsequently, some researchers propose a control method based on an extended state observer, and compared with the traditional method, the method can inhibit the influence of external disturbance on the system without directly measuring the disturbance current, and has stronger robustness on uncertain disturbance and parameter change. However, the method uses a proportional resonant controller in the inner loop, and needs to convert the power reference into a corresponding current reference and then control the amount of current, which increases the operation burden of the system. In addition, a student provides a control strategy based on a nonlinear disturbance observer aiming at the alternating current-direct current hybrid microgrid, and the observer has good dynamic quality through practice verification.
Disclosure of Invention
According to the problems in the prior art, the invention discloses a direct power control method for inhibiting voltage fluctuation of a direct-current side bus of a photovoltaic grid-connected inverter, which comprises the following steps:
s1, establishing a photovoltaic power generation system, wherein the photovoltaic power generation system comprises a photovoltaic array, a boost circuit, an inverter, a filter inductor, an MPPT controller, a control system and a power grid, and the photovoltaic array is connected with the boost circuit and the boost circuit is connected with the inverter through capacitors; 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 circuit; the input end of the control system is connected with a power grid, and the output end of the control system is connected with an inverter;
s2, detecting the voltage U of the photovoltaic array by using a voltage sensor pv DC bus voltage U dc And the network voltage v a,b,c Detecting the output current I of the photovoltaic array by means of a current sensor pv And net side current i a,b,c Performing abc/alpha on three-phase voltage and three-phase current respectivelyBeta conversion to obtain instantaneous active component v on alpha-beta axis α 、i α And a transient reactive component v β 、i β ；
S3, changing the output voltage of the photovoltaic array by adopting a fixed step disturbance observation method and changing the duty ratio of a switching tube, and carrying out maximum power point tracking on the photovoltaic array;
s4, according to the instantaneous active component v α 、i α And a transient reactive component v β 、i β Calculating the grid-connected active power P g And grid-connected reactive power Q g Based on the square of the DC bus voltage
And grid-connected active power P g Obtaining the disturbance power by a nonlinear disturbance observer
It is combined with a correction link G ch (s) multiplying to obtain the corrected disturbance power
S5, squaring the voltage detection value of the direct current bus
Square of given value of DC bus voltage
After the difference is made, an error control signal is obtained
Error signal e by voltage outer loop P regulator dc Performing closed-loop processing to output quantity and disturbance power of the voltage outer-loop P regulator
Adding to obtain the given value of the active power of the inverter
S6, giving active power
And output active power P g Difference by subtraction, given reactive power
And output reactive power Q g The subtracted difference signals are respectively used as the input of an inner-loop active PI controller and an inner-loop reactive PI controller to obtain output signals
Wherein an instantaneous reactive power reference for the grid-connected inverter output is set
S7, outputting signals of the inner ring active PI controller and the inner ring reactive PI controller
Respectively used as input signals of a feedforward decoupling controller to construct a feedforward decoupling model based on the voltage v of the power grid α 、v β Combined with the output u of the feedforward decoupling system P 、u Q To obtain a voltage control signal e α And e β ；
S8, for the voltage control signal e α And e β Carrying out alpha beta/abc conversion to obtain SPWM control signal e of the inverter a 、e b 、e c 。
Further, obtaining disturbance power through a nonlinear disturbance observer
The process comprises the following steps:
s4-1 direct current bus capacitors C and R l Consumed active power and grid-connected active power P g Dynamic equation ofComprises the following steps:
wherein: c is DC bus capacitor, U dc Is a DC bus voltage, R l Representing losses, P, of the subsequent inverter s For the direct current power flowing through the booster circuit, P g For grid-connected active power, Q g Is the grid-connected reactive power;
s4-2, rewriting the above formula (1) into the following form:
wherein: x is the number of 1 And x 2 As a state variable, the control input is u P ＝v α e α +v β e β ，P s Defining as a disturbance variable;
s4-3. The non-linear disturbance observer for estimating the external disturbance d (t) can be described by the following equation:
wherein: z is the intermediate state quantity of the nonlinear disturbance observer,
for the estimation of the disturbance variable, the nonlinear disturbance observer gain is l (x) = [ l 1 l 2 ]Wherein l is 1 、l 2 The gain of the nonlinear disturbance observer is represented, p (x) is an observation function needing to be designed, and can be represented as: p (x) = l 1 x 1 +l 2 x 2 ；
S4-4, obtaining observer gain l 1 ＞0，l 2 =0, the above formula (3) can be written as:
wherein:
as a disturbance variable P s An estimate of (d).
Further, the disturbance observer observed value
With true value P s There is the following relationship between:
wherein: to b Is the time constant of a non-linear disturbance observer with a value equal to C/2l 1 。
Further, the active power given value
Calculated by the following formula (6):
wherein: k p Is the gain of the voltage outer loop P regulator, e dc Is an error control signal having a value equal to
G ch (s) is a transfer function of an observation error correction link;
wherein: t is ch Is the differential time constant.
Further, the input of the feedforward decoupling controller
Calculated by the following formula (8):
wherein: k P,p Proportional gain, K, for an active power inner loop PI regulator P,i Is the integral gain, K, of an active power inner loop PI regulator Q,p Proportional gain, K, for a reactive power inner loop PI regulator Q,i Integral gain, e, of the reactive power inner loop PI regulator P Adjusting the error for active power, e Q For the reactive power regulation error, it is calculated by the following equation (9):
wherein:
is a given value of reactive power, which is 0.
Further, the output signal u of the feedforward decoupling controller P 、u Q Calculated by the following formula (10):
or is represented as:
wherein: e.g. of the type d 、e q The component of the inverter output voltage on the dq axis.
Further, the control signal e α 、e β Calculated by the following formula (12):
wherein: u. of P 、u Q For feedforward decoupling of the output signal of the controller, v α 、v β For the component of the grid voltage on the α β axis, V g The amplitude of the three-phase balanced grid voltage.
Further, SPWM control signal e a ，e b ，e c Calculated by the following formula (13):
according to the direct power control method for inhibiting the voltage fluctuation of the direct-current side bus of the photovoltaic grid-connected inverter, the direct-current bus voltage and the network side power are obtained through sampling, and the fast tracking of the interference amount is realized by utilizing the nonlinear disturbance observer; the feedforward disturbance quantity is introduced into the voltage outer ring, and the zero steady-state error tracking of the direct-current bus voltage can be ensured by adopting a simple proportional controller; the direct power control method based on power grid voltage modulation is adopted, the power at the power grid side can be controlled in real time, the rapid balance of the input power and the alternating current output power of a direct current source is realized, and the fluctuation amplitude of the bus voltage is reduced; the invention does not need to acquire the phase information of the power grid voltage and does not need to carry out synchronous rotation coordinate transformation, thereby avoiding the stability problem caused by using a phase-locked loop (PLL).
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments described in the present application, and other drawings can be obtained by those skilled in the art without creative efforts.
Fig. 1 is a schematic diagram of a control scheme of a conventional photovoltaic grid-connected inverter;
FIG. 2 is a schematic structural view of the present invention;
FIG. 3 is a schematic diagram of a control scheme of the photovoltaic grid-connected inverter of the invention;
FIG. 4 (a) is a waveform diagram of output power of the photovoltaic panel when the illumination intensity changes for 4 s;
FIG. 4 (b) is a graph of the output voltage waveform of the photovoltaic panel when the illumination intensity changes for 4 s;
FIG. 4 (c) is a waveform diagram of the output current of the photovoltaic panel when the illumination intensity changes for 4 s;
fig. 5 (a) is a simulation waveform diagram of the dc side bus voltage of the photovoltaic grid-connected inverter, in which the illumination intensity changes and a conventional control method is adopted, when 4s occurs;
fig. 5 (b) is a simulated waveform diagram of grid-connected voltage and current of the photovoltaic grid-connected inverter, in which the illumination intensity changes and a traditional control method is adopted, when 4s occurs;
fig. 5 (c) is a simulation waveform diagram of the grid-connected power of the photovoltaic grid-connected inverter, in which the illumination intensity changes and a conventional control method is adopted, when 4s occurs;
FIG. 6 (a) is a simulation waveform diagram of the DC side bus voltage of the photovoltaic grid-connected inverter, in which the control method of the present invention is adopted, when the illumination intensity changes for 4 s;
FIG. 6 (b) is a simulated waveform diagram of grid-connected voltage and current of the photovoltaic grid-connected inverter, in which the control method of the present invention is adopted, when the illumination intensity changes for 4 s;
FIG. 6 (c) is a simulation waveform diagram of grid-connected power of the photovoltaic grid-connected inverter, in which the control method of the present invention is adopted, when the illumination intensity changes for 4 s;
fig. 7 (a) is a simulation waveform diagram of bus voltage at the dc side of the photovoltaic grid-connected inverter, in which when the illumination intensity changes and the filter inductance changes from 23mH to 18mH in 4s, other parameters are not changed, and a conventional control method is adopted;
fig. 7 (b) is a simulation waveform diagram of grid-connected voltage and current of the photovoltaic grid-connected inverter, in which when the illumination intensity changes and the filter inductance changes from 23mH to 18mH in 4s, other parameters are unchanged, and the traditional control method is adopted;
fig. 7 (c) is a simulation waveform diagram of grid-connected power of the photovoltaic grid-connected inverter, in which when the illumination intensity changes and the filter inductance changes from 23mH to 18mH, other parameters do not change, and a conventional control method is adopted when 4 s;
fig. 8 (a) is a simulation waveform diagram of the dc-side bus voltage of the photovoltaic grid-connected inverter, in which the output power of the photovoltaic panel is constant, the grid voltage suddenly rises by 10% when 10s, and other parameters are unchanged, and the control method of the present invention is adopted;
fig. 8 (b) is a simulation waveform diagram of grid-connected voltage and current of the photovoltaic grid-connected inverter, in which the output power of the photovoltaic panel is constant, when the output power is 10s, the grid voltage suddenly rises by 10%, and other parameters are unchanged, and the control method of the invention is adopted;
fig. 8 (c) is a simulation waveform diagram of grid-connected power of the photovoltaic grid-connected inverter, in which the output power of the photovoltaic panel is constant, the grid voltage suddenly rises by 10% when 10s is elapsed, and other parameters are unchanged, and the control method of the invention is adopted.
Detailed Description
In order to describe the invention more specifically, the direct power control method for suppressing the voltage fluctuation of the dc-side bus of the photovoltaic grid-connected inverter according to the invention is described in detail below with reference to the accompanying drawings and the detailed description.
Fig. 1 is a schematic diagram of a control scheme of a conventional photovoltaic grid-connected inverter, fig. 2 is a schematic diagram of a structure of the photovoltaic grid-connected inverter, and fig. 3 is a schematic diagram of a control scheme of the photovoltaic grid-connected inverter; the invention relates to a direct power control method for inhibiting voltage fluctuation of a direct-current side bus of a photovoltaic grid-connected inverter, which comprises the following steps of:
s1, establishing a photovoltaic power generation system, wherein the photovoltaic power generation system comprises a photovoltaic array, a boost circuit, a 17kW grid-connected inverter, a filter inductor, an MPPT controller, a control system and a power grid, and the photovoltaic array is connected with the boost circuit and the boost circuit are connected with the inverter through capacitors; 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 circuit; the input end of the control system is connected with a power grid, and the output end of the control system is connected with an inverter; setting the photovoltaic array parameter as V oc ＝450V，I sc =60A, maximum power point V mpp ＝350V，I mpp ＝45A。
S2, collecting light by utilizing Hall voltage sensorOutput voltage U of the volt array pv DC bus voltage U dc And the voltage v of the network a,b,c Collecting output current I of the photovoltaic array by using a Hall current sensor pv And net side current i a,b,c Carrying out abc/alpha beta conversion on three-phase balance power grid voltage and three phases to obtain instantaneous active component v on an alpha beta shaft α 、i α And a transient reactive component v β 、i β (ii) a The α β coordinate transformation matrix is as follows:
the expression of the three-phase balanced power grid voltage in an alpha beta coordinate system is as follows:
wherein: v g The amplitude of the three-phase balanced grid voltage is shown, and omega is the angular frequency of the grid voltage; in the present embodiment, the effective value of the three-phase balanced grid voltage is 220V, ω =2 π f, f =50hz, V g 179.6V were taken.
S3, maximum power point tracking is carried out on the photovoltaic array by adopting a fixed step length disturbance observation method, and the sampling period T of the MPPT algorithm a Calculated by the following formula (3):
wherein: l is 0 To boost the inductance value, C 0 Representing the filter capacitance, R, of the boost circuit L The parasitic resistance on the inductor is used, k is the ratio of the current change rate to the voltage change rate, k & lt-1 can be assumed in a constant voltage source region, and k is approximately equal to 0 in a constant current source region; in this embodiment, L 0 Is 5mH 0 550 μ F, R L Is 300 omega, k is 0, and the perturbation step size is 5 multiplied by 10 -4 The sampling period is 1.67X 10 -4 s。
And S4, calculating the instantaneous active power P and the instantaneous reactive power Q by the following formulas:
wherein: i.e. i α And i β The current is the current on the network side after coordinate transformation.
Neglecting the resistance of the filter inductor, it can be expressed as:
wherein: l is the filter inductance value, e α ，e β Is the α β component of the inverter output voltage.
Squaring based on DC bus voltage
And grid-connected active power P g Obtaining the disturbance power by a disturbance observer
It is combined with a correction link G ch (s) multiplying to obtain the corrected disturbance power
Calculation by disturbance observer
The method comprises the following steps:
s4-1 first, bus capacitors C and R l The dynamic equations of the consumed active power and the grid-connected active power are as follows:
s4-2, wherein: c is DC bus capacitor, U dc Is a DC bus voltage, R l Representing losses, P, of the subsequent inverter s For the direct current power flowing through the booster circuit, P g Is the grid-connected active power; in this embodiment, C is 3300. Mu.F, R l Taking 1000 omega;
further, the above equation (6) is written as follows:
wherein: x is the number of 1 And x 2 Is a state variable, u P To control the input quantity, P s Is the disturbance quantity; in this embodiment, L is 23mH.
S4-3. The non-linear disturbance observer for estimating the external disturbance d (t) can be described by the following equation:
wherein: z is an intermediate state quantity of the observer,
for the estimation of the disturbance variable, the observer gain is l (x) = [ l 1 l 2 ]And p (x) is an observation function needing to be designed and can be expressed as: p (x) = l 1 x 1 +l 2 x 2 ；
S4-4, obtaining observer gain l 1 ＞0，l 2 =0, expression (9) of the nonlinear disturbance observer is:
wherein:
as a disturbance variable P s An estimate of (d).
Further, the disturbance observer observed value
With true value P s There is the following relationship between:
wherein: t is ob Is the time constant of a non-linear disturbance observer with a value equal to C/2l 1 。
S5, squaring the voltage detection value of the direct current bus
Square of given value of DC bus voltage
After the difference is made, an error control signal is obtained
Error signal e by P regulator dc Performing closed-loop processing to output quantity and disturbance power of P regulator
Adding to obtain the given value of the active power of the inverter
Given value of active power P * Calculated by the following formula (11):
wherein: k p Is the gain of the voltage outer loop P regulator, e dc Is an error control signal having a value equal to
G ch (s) is a transfer function of an observation error correction link; in this embodiment, K p Taking out the mixture of 0.5 percent,
transfer function G of correction link ch (s)＝0.05s+1。
The G is ch (s) is calculated by the following formula (12):
wherein: k P,p 、K P,i The proportional and differential gains of the active power inner loop PI regulator are respectively.
The G is ch The expression(s) can be simplified as:
wherein: t is a unit of ch Is the differential time constant.
S6, giving active power
And output active power P g Difference by subtraction, given reactive power
And output reactive power Q g The subtracted difference signals are respectively input into an inner-loop active PI controller and an inner-loop reactive PI controller to obtain output signals
Wherein an instantaneous reactive power reference of the grid-connected inverter output is set
S7, output signals of the inner ring active PI controller and the inner ring reactive PI controller are processed
Respectively asEstablishing a feedforward decoupling model from input signals of a feedforward decoupling controller, the input of which
Calculated by the following formula (14):
wherein: e.g. of the type P And e Q For the power regulation error, it is calculated by the following equation (15):
wherein: k P,p 、K P,i 、K Q,p 、K Q,i And
are respectively 40, 19893, 40, 19893 and 0.
S7, based on the voltage v of the power grid α 、v β Combined with the output u of the feedforward decoupling system P 、u Q To obtain a voltage control signal e α And e β (ii) a Output u of feedforward decoupling controller P 、u Q Calculated by the following formula (16):
wherein:
is the input to a feed forward decoupling controller.
Further, the method comprises the following steps: output u of feedforward decoupling controller P 、u Q Can also be expressed as:
wherein: e.g. of a cylinder d 、e q The component of the inverter output voltage on the dq axis.
Control signal e α 、e β Calculated by the following formula (18):
wherein: u. of P 、u Q For the output of a feed-forward decoupling controller, v α 、v β Is the component of the grid voltage on the α β axis.
S8, for the voltage control signal u α And u β Carrying out alpha beta/abc conversion to obtain an SPWM signal of the inverter so as to control a switching device in the grid-connected inverter, wherein an alpha beta/abc conversion matrix is T abc/αβ The inverse matrix of (c).
Hereinafter, the photovoltaic grid-connected inverter according to the present embodiment is simulated.
FIG. 4 (a) is a waveform diagram of output power of the photovoltaic panel when the illumination intensity changes for 4 s; FIG. 4 (b) is a graph of the output voltage waveform of the photovoltaic panel when the illumination intensity changes for 4 s; FIG. 4 (c) is a waveform diagram of the output current of the photovoltaic panel when the illumination intensity changes for 4 s; in 4s, the illumination intensity is changed, and the output power of the photovoltaic panel is changed from 8kW to 16kW;
fig. 5 (a) is a simulation waveform diagram of the dc side bus voltage of the photovoltaic grid-connected inverter, in which the illumination intensity changes and a conventional control method is adopted, when 4s occurs; fig. 5 (b) is a simulated waveform diagram of grid-connected voltage and current of the photovoltaic grid-connected inverter, in which the illumination intensity changes and a traditional control method is adopted, when 4s occurs; fig. 5 (c) is a simulation waveform diagram of the grid-connected power of the photovoltaic grid-connected inverter, in which the illumination intensity changes and a conventional control method is adopted, when 4s occurs;
FIG. 6 (a) is a simulation waveform diagram of the DC side bus voltage of the photovoltaic grid-connected inverter, in which the control method of the present invention is adopted, when the illumination intensity changes for 4 s; FIG. 6 (b) is a simulated waveform diagram of grid-connected voltage and current of the photovoltaic grid-connected inverter, in which the control method of the present invention is adopted, when the illumination intensity changes for 4 s; FIG. 6 (c) is a simulation waveform diagram of grid-connected power of the photovoltaic grid-connected inverter, in which the control method of the present invention is adopted, when the illumination intensity changes for 4 s;
when the illumination intensity changes and the system has step disturbance, the traditional voltage and current double closed-loop control strategy is adopted, the fluctuation range of the bus voltage is large, and compared with the embodiment, the bus voltage has serious overshoot and slow convergence speed; by adopting the control method provided by the invention, the bus voltage has about 110V overshoot, and the stable state can be achieved only after 0.8 s.
Fig. 7 (a) is a simulation waveform diagram of bus voltage at the dc side of the photovoltaic grid-connected inverter, in which when the illumination intensity changes and the filter inductance changes from 23mH to 18mH in 4s, other parameters are not changed, and a conventional control method is adopted; fig. 7 (b) is a simulation waveform diagram of grid-connected voltage and current of the photovoltaic grid-connected inverter, in which when the illumination intensity changes and the filter inductance changes from 23mH to 18mH in 4s, other parameters are unchanged, and the traditional control method is adopted; fig. 7 (c) is a simulation waveform diagram of grid-connected power of the photovoltaic grid-connected inverter, in which when the illumination intensity changes and the filter inductance changes from 23mH to 18mH, other parameters do not change, and a conventional control method is adopted when 4 s; it can be seen that when the filter inductance value is changed, other parameters are kept unchanged, and by adopting the control method provided by the invention, the response speed of the system is slowed down, the time required for reaching a stable state is prolonged, but the overall performance is not changed obviously.
Fig. 8 (a) is a simulation waveform diagram of the dc-side bus voltage of the photovoltaic grid-connected inverter, in which the output power of the photovoltaic panel is constant, the grid voltage suddenly rises by 10% when 10s, and other parameters are unchanged, and the control method of the present invention is adopted; fig. 8 (b) is a simulation waveform diagram of grid-connected voltage and current of the photovoltaic grid-connected inverter, in which the output power of the photovoltaic panel is constant, when the output power is 10s, the grid voltage suddenly rises by 10%, other parameters are unchanged, and the control method of the invention is adopted; fig. 8 (c) is a simulation waveform diagram of the grid-connected power of the photovoltaic grid-connected inverter, in which the output power of the photovoltaic panel is constant, and when the grid voltage rises 10% suddenly and other parameters are unchanged at 10s, by using the control method provided by the present invention, the bus voltage and the active power have slight overshoot, and after the grid voltage is stable, the system can quickly reach a stable state.
In summary, the embodiment does not need to acquire phase information of the power grid, does not need to perform synchronous rotation coordinate transformation, and has a simple structure and excellent dynamic response performance; the direct-current bus voltage and the network side power are obtained through sampling, and the fast tracking of the interference amount can be realized by utilizing the nonlinear disturbance observer, so that the robustness on uncertain disturbance and parameter change is strong; by adopting the direct power control method based on the power grid voltage modulation, the power at the power grid side can be controlled in real time, the rapid balance of the input power and the output power of the direct current source is realized, and the fluctuation of the voltage of the direct current bus is effectively inhibited.
Claims (8)
1. A direct power control method for restraining voltage fluctuation of a direct-current side bus of a photovoltaic grid-connected inverter is characterized by comprising the following steps: the method comprises the following steps:
s1, establishing a photovoltaic power generation system, wherein the photovoltaic power generation system comprises a photovoltaic array, a boost circuit, an inverter, a filter inductor, an MPPT controller, a control system and a power grid, and the photovoltaic array is connected with the boost circuit and the boost circuit is connected with the inverter through capacitors; 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 circuit; the input end of the control system is connected with a power grid, and the output end of the control system is connected with an inverter;
s2, detecting the voltage U of the photovoltaic array by using a voltage sensor pv DC bus voltage U dc And the network voltage v a,b,c Detecting the output current I of the photovoltaic array by means of a current sensor pv And net side current i a,b,c Respectively carrying out abc/alpha beta conversion on the three-phase voltage and the three-phase current to obtain an instantaneous active component v on an alpha beta axis α 、i α And instantaneousReactive component v β 、i β ；
S3, changing the output voltage of the photovoltaic array by adopting a fixed step disturbance observation method and changing the duty ratio of a switching tube, and carrying out maximum power point tracking on the photovoltaic array;
s4, according to the instantaneous active component v α 、i α And a transient reactive component v β 、i β Calculating the grid-connected active power P g And grid-connected reactive power Q g Based on the square of the DC bus voltage
And grid-connected active power P g Obtaining the disturbance power by a nonlinear disturbance observer
It is combined with a correction link G ch (s) multiplying to obtain the corrected disturbance power
S5, squaring the voltage detection value of the direct current bus
Square of given value of DC bus voltage
After the difference is made, an error control signal is obtained
Error signal e by voltage outer loop P regulator dc Performing closed-loop processing to output quantity and disturbance power of the voltage outer-loop P regulator
Adding to obtain the given value of the active power of the inverter
S6, giving active power
And output active power P g Difference by subtraction, given reactive power
And output reactive power Q g The subtracted difference signals are respectively used as the input of an inner-loop active PI controller and an inner-loop reactive PI controller to obtain output signals
Wherein an instantaneous reactive power reference of the grid-connected inverter output is set
S7, output signals of the inner ring active PI controller and the inner ring reactive PI controller are processed
Respectively used as input signals of a feedforward decoupling controller to construct a feedforward decoupling model based on the voltage v of the power grid α 、v β Combined with the output u of the feedforward decoupling system P 、u Q To obtain a voltage control signal e α And e β ；
S8, for the voltage control signal e α And e β Carrying out alpha beta/abc conversion to obtain SPWM control signal e of the inverter a 、e b 、e c 。
2. The method of claim 1, wherein the disturbance power is obtained by a non-linear disturbance observer
The process comprises the following steps:
s4-1 direct current bus capacitors C and R l Consumed active power and grid-connected active power P g The dynamic equation of (a) is:
wherein: c is DC bus capacitor, U dc Is a DC bus voltage, R l Representing losses, P, of the subsequent inverter s For the direct current power flowing through the booster circuit, P g For grid-connected active power, Q g Is the grid-connected reactive power;
s4-2, rewriting the above formula (1) into the following form:
wherein: x is the number of 1 And x 2 As state variables, the control input is u P ＝v α e α +v β e β ，P s Defining as a disturbance variable;
s4-3. The non-linear disturbance observer for estimating the external disturbance d (t) can be described by the following equation:
wherein: z is the intermediate state quantity of the nonlinear disturbance observer,
for the estimated value of the disturbance variable, the gain of the nonlinear disturbance observer is l (x) = [ l = 1 l 2 ]Wherein l is 1 、l 2 The gain of the nonlinear disturbance observer is represented, p (x) is an observation function needing to be designed, and can be represented as: p (x) = l 1 x 1 +l 2 x 2 ；
S4-4, obtaining observer gain l 1 >0，l 2 =0, the above formula (3) can be written as:
wherein:
as a disturbance variable P s An estimate of (d).
3. The method of claim 1, wherein the disturbance observer observations
With true value P s There is the following relationship between:
wherein: to b Is the time constant of a non-linear disturbance observer with a value equal to C/2l 1 。
4. Method according to claim 1, characterized in that the active power set point value
Calculated by the following formula (6):
wherein: k p Gain of the voltage outer loop P regulator, e dc Is an error control signal having a value equal to
G ch (s) is a transfer function of an observation error correction link;
wherein: t is ch Is the derivative time constant.
5. The method of claim 1, wherein the input to the feedforward decoupling controller is
Calculated by the following formula (8):
wherein: k P,p Proportional gain, K, for an active power inner loop PI regulator P,i Is the integral gain, K, of an active power inner loop PI regulator Q,p Proportional gain, K, for a reactive power inner loop PI regulator Q , i Integral gain, e, of a reactive power inner loop PI regulator P Adjusting the error for active power, e Q For the reactive power regulation error, it is calculated by the following equation (9):
wherein:
is a given value of reactive power, which is 0.
6. The method of claim 1, wherein the first and second light sources are selected from the group consisting of,characterized in that the output signal u of the feedforward decoupling controller P 、u Q Calculated by the following formula (10):
or is represented as:
wherein: e.g. of the type d 、e q The component of the inverter output voltage on the dq axis.
7. Method according to claim 1, characterized in that the control signal e α 、e β Calculated by the following formula (12):
wherein: u. of P 、u Q For feedforward decoupling of the output signal of the controller, v α 、v β For the component of the grid voltage on the α β axis, V g The amplitude of the three-phase balanced grid voltage.
8. Method according to claim 1, characterized in that the SPWM controls signal e a ，e b ，e c Calculated by the following formula (13):
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| CN112003302A (en) * | 2020-08-21 | 2020-11-27 | 西安热工研究院有限公司 | Method for inhibiting voltage fluctuation of micro-grid bus |
| CN111969619B (en) * | 2020-10-26 | 2021-03-02 | 国网江西省电力有限公司电力科学研究院 | Reactive compensation method and device for photovoltaic inverter |
| CN112436547B (en) * | 2020-11-17 | 2022-07-05 | 青岛大学 | Double-grid-connected interface medium-voltage photovoltaic power generation system with SOP function |
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| CN112350330A (en) * | 2020-11-20 | 2021-02-09 | 西安热工研究院有限公司 | Method for inhibiting voltage fluctuation of alternating current side of energy storage inverter |
| CN112531783B (en) * | 2020-12-07 | 2022-06-07 | 青岛大学 | Photovoltaic power generation system with SOP function |
| CN113241796B (en) * | 2021-06-03 | 2022-05-27 | 合肥工业大学 | Power control method for photovoltaic grid-connected inverter under extremely weak grid |
| CN113726204A (en) * | 2021-09-07 | 2021-11-30 | 天津理工大学 | Robust control method for DC bus voltage of photovoltaic grid-connected inverter |
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Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103455081A (en) * | 2013-08-19 | 2013-12-18 | 西安理工大学 | Maximum power point tracking method based on disturbance observation |
| CN108808722A (en) * | 2017-04-27 | 2018-11-13 | 安徽华网电力设计有限公司 | Grid-connected and power quality controlling unified control method |
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| Publication number | Priority date | Publication date | Assignee | Title |
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