A dual-objective continuous set model predictive power decoupling control method and system

Abstract

The application discloses a dual-target continuous set model predictive power decoupling control method, and belongs to the technical field of power electronic conversion; the control method comprises the following steps: obtaining a mathematical model of discrete time points of a boost inductor current and a filter inductor current, performing discretization processing on the mathematical model to obtain a prediction model, and calculating inductor current and grid-connected current prediction values at a next time point; obtaining control input variables of the boost inductor current and the filter inductor current, setting a value function, and obtaining optimal conduction duty ratios of a boost side and an inversion side through the input variables and the prediction values; designing a PI voltage outer ring, obtaining reference values required by an inner ring, and performing prediction error compensation; based on the PI voltage outer ring and the optimal duty ratios, designing a notch filter in the voltage outer ring, calculating a feedforward value of a reference current, and performing control decoupling of input current and output current.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of power electronic conversion, and particularly relates to a dual-target continuous set model predictive power decoupling control method and system. BACKGROUND

[0002] In a photovoltaic inverter system, a front-stage boost circuit is usually combined with an inverter circuit, but once this combined mode is used in a large-scale distributed photovoltaic grid-connected system, the number of devices is large, and a single-stage boost inverter reduces the number of devices used and has a boost function and an inverter function, and the negative polarity end of the input power supply and the neutral point of the grid are connected in common, eliminating the influence of the leakage current, and being more suitable for the application scenario of photovoltaic grid connection. For the traditional PI control method of the existing inverter system, the PI double-closed-loop control parameters are difficult to set in a complex coupled system, and the PI cannot realize zero-error tracking of a sinusoidal signal; the limited set model predictive control can realize effective control of multiple variables, and is beneficial to increase constraints and has been widely used in inverter systems, but the control signal frequency is not fixed, resulting in dispersed output signal harmonics, and it is difficult to design a filter; the traditional continuous set model predictive control is generally designed for traditional topologies, and the research on the continuous set model predictive control of the single-stage boost inverter circuit is currently less. SUMMARY

[0003] In view of the deficiencies of the prior art, the purpose of the present application is to provide a dual-target continuous set model predictive power decoupling control method and system, which solves the problems in the prior art.

[0004] The purpose of the present application can be achieved by the following technical solutions:

[0005] A dual-target continuous set model predictive power decoupling control method is used for decoupling control of a grid-connected system containing a single-stage boost photovoltaic inverter circuit, and comprises the following steps:

[0006] A mathematical model of a boost inductor current and a grid-connected current is obtained, the mathematical model is discretized to obtain a prediction model, and a boost inductor current and a grid-connected current prediction value at the next moment are calculated;

[0007] Control input variables of the boost inductor current and the grid-connected current are obtained, a value function is set, and through the input variables and the prediction value, optimal conduction duty cycles of the boost side and the inverter side are obtained;

[0008] A PI voltage outer loop is designed, input current and output current reference values required by an inner loop are obtained, and prediction error compensation is performed;

[0009] Based on the PI voltage outer loop and the optimal duty ratio, a notch filter in the voltage outer loop is designed, a feedforward value of the reference current is calculated, and input current and output current are controlled to be decoupled.

[0010] Further, the single-stage boost photovoltaic inverter circuit is configured in a common ground structure by combining a full-bridge inverter circuit and a bidirectional boost circuit, and a multiplexing switch tube exists.

[0011] The single-stage boost photovoltaic inverter circuit comprises switch tubes S1-S5, a capacitor C, an input power supply, an alternating current source, a boost inductor L, and a filter inductor L g The switch tube S5 and the switch tube S1, the switch tube S2, and the capacitor C constitute a bidirectional boost circuit, U in is an input voltage of the boost circuit, U C is an output voltage of the boost circuit, and the output of the single-stage boost photovoltaic inverter circuit is incorporated into the power grid through the filter inductor L g after filtering out harmonics.

[0012] Further, the mathematical model is:

[0013]

[0014]

[0015] In the formula, f i1 , f i2 , f i3 respectively represent the slopes corresponding to the three changes of the boost inductor current, f g1 , f g2 , f g3 respectively represent the slopes corresponding to the three changes of the grid-connected current; i L is the input current, U C is the voltage of the capacitor C, U in is the input voltage, U ab is the bridge arm voltage, U g is the grid voltage, R L is the parasitic impedance of the boost inductor, R g is the parasitic impedance of the filter inductor, i g is the grid-connected current, L is the boost inductor value, L g is the filter inductor value.

[0016] Further, the calculation formula of the inductor current and the grid-connected current prediction value at the next moment is:

[0017] i L (k+1)=i L (k)+2fi1 t L +(T s -2t L )f i2

[0018] i g (k+1)=i g (k)+2f g1 t g +(T s -2t g )f g2

[0019] wherein, i L (k+1) and i g (k+1) are the predicted inductance current value and grid-connected current value at next time, i g (k) and i L (k) are the grid-connected current and boost inductance current sampled by the sampling module at k time, T s is the sampling period, t L represents the time of the first rising of the boost inductance current, t g represents the time of the first rising of the grid-connected current.

[0020] Further, the optimal duty ratio calculation formula of the boost side and the inverter side is:

[0021]

[0022] In the formula, d S5 is the optimal duty ratio of the switch tube S5 calculated, and d is the optimal duty ratio of the grid-connected current working in the rising interval calculated in a period;

[0023] The duty ratio d S5 of the switch tube S5 is directly generated by the PWM modulation module. Since the inverter side has two half-cycle working periods, d is processed as follows:

[0024] Define two intermediate variables d1 and d2. If the grid voltage U g >0, then d1=0, d2=d. If U g <0, then d1=d, d2=0. The modulation signal obtained by processing in this way, d1 is the duty ratio of the switch tube S3, and d2 is the duty ratio of the switch tube S1. The duty ratios d1 and d2 are directly PWM modulated to obtain the conduction signals of S1 and S3. Since S4 and S3 are complementary, and S2 and S1 are complementary, the conduction signals of all switch tubes of the two bridge arms of the inverter side are obtained.

[0025] Further, the process of performing prediction error compensation by the PI voltage outer loop comprises:

[0026] For the input side, the voltage outer loop is used to achieve the DC input voltage following MPPT reference voltage, and the output of the voltage outer loop PI controller is the reference value of the input current i L_ref ;

[0027] For the output side, the voltage outer loop controls the average voltage U C_ave of the intermediate decoupling capacitor C to ensure the power balance between the input and output sides and that the system will not be over-modulated. When the input power increases, the average voltage U C_ave of the capacitor C increases, the average capacitor voltage is subtracted from the reference value of the average capacitor voltage, and after the PI controller, the reference value of the output current is increased to compensate for the error value of the inner loop output predicted current.

[0028] Further, when the average voltage reference value of the output side voltage outer loop satisfies the following formula, the control decoupling of the input current and the output current can be achieved:

[0029]

[0030] In the formula, U g is the peak-to-peak value of the grid voltage, U C is the instantaneous value of the capacitor voltage, and U in is the input voltage.

[0031] A dual-target continuous set model predictive power decoupling control system, comprising:

[0032] a predictive model construction module that acquires a mathematical model of the boost inductor current and the grid current at discrete time points, discretizes the mathematical model to obtain a predictive model, and calculates predictive values of the inductor current and the grid current at the next time point;

[0033] an optimization module that acquires control input variables of the boost inductor current and the grid current, sets a value function, and acquires optimal conduction duty cycles of the boost side and the inverter side through the input variables and the predictive values;

[0034] a PI voltage outer loop design module that designs a PI voltage outer loop, acquires reference values of the input current and the output current required by the inner loop, and performs predictive error compensation;

[0035] and a control decoupling module that, based on the PI voltage outer loop and the optimal duty cycles, designs a notch filter in the voltage outer loop, calculates a feedforward value of the reference current, and performs control decoupling of the input current and the output current.

[0036] A computer storage medium storing a readable program, which, when executed, can perform the dual-target continuous set model predictive power decoupling control method described above.

[0037] An electronic device comprises a processor, a memory, a communication interface and a communication bus, the processor, the memory and the communication interface complete communication with each other through the communication bus;

[0038] The memory is used to store at least one executable instruction, and the executable instruction makes the processor execute the operation corresponding to the above-mentioned dual-target continuous set model predictive power decoupling control method.

[0039] The beneficial effects of the present application are:

[0040] 1. The control method of the present application simultaneously controls the input current and the output current of the power electronic converter, and fully considers the coupling relationship in the control, and realizes the control decoupling of the input current and the output current of the system by introducing the PI outer ring to control the average value of the intermediate decoupling capacitor voltage, and effectively avoids the system operation collapse problem caused by the coupling relationship.

[0041] 2. The present application uses the PI outer ring to obtain the reference value of the inner ring, and performs prediction error compensation on the inner ring continuous set model predictive control, and the inner ring directly controls the photovoltaic input power and the alternating current side power through the continuous set model predictive power decoupling control, which significantly reduces the DC side secondary ripple problem caused by the instantaneous power imbalance between the alternating current input side and the direct current input side in the single-phase photovoltaic inverter system, and realizes automatic power decoupling. BRIEF DESCRIPTION OF DRAWINGS

[0042] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the drawings needed to be used in the embodiment or prior art description will be briefly introduced below, and obviously, other drawings can also be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0043] Figure 1 The power decoupling control method of the present application is a flow chart;

[0044] Figure 2 The power decoupling control diagram of the present application is a flow chart;

[0045] Figure 3 The single-stage boost photovoltaic inverter circuit topology structure diagram of the present application is a flow chart;

[0046] Figure 4 The MATLAB simulation steady-state input current and output current waveform effect diagram of the present application is a flow chart;

[0047] Figure 5 The MATLAB simulation steady-state input current, output current and input voltage THD effect diagram of the present application is a flow chart;

[0048] Figure 6 It is a MATLAB simulation steady-state output capacitor voltage waveform diagram of the present invention;

[0049] Figure 7 It is a diagram showing the dynamic response of input current and output current when the reference current changes in the MATLAB simulation using the present invention. DETAILED DESCRIPTION

[0050] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0051] Example 1

[0052] like Figure 2 As shown, a dual-objective continuous set model predictive power decoupling control method is used to perform decoupling control on a grid-connected system including a single-stage boost photovoltaic inverter circuit;

[0053] The single-stage boost inverter circuit is constructed by combining a full-bridge inverter circuit with a bidirectional boost circuit to form a common ground structure. In addition, there are multiplexed switch tubes, which is a single-stage boost inverter circuit. The input side of the single-stage boost inverter circuit is connected to a photovoltaic panel or a DC source, and the output side is connected to the power grid. Combined with a controller (the controller algorithm adopts a dual-objective continuous set model predictive power decoupling control method of the present invention), the efficient operation of the system is achieved.

[0054] like Figure 3 As shown, the single-stage boost inverter circuit includes: switch tubes S1-S5, capacitor C, input power supply (voltage is U in ), AC source (voltage is u g ), boost inductor L and filter inductor L g The switch tube S5, the switch tube S1, the switch tube S2 and the capacitor C form a bidirectional boost circuit. in is the input voltage of the boost circuit, U C is the output voltage of the boost circuit. At the same time, if the switch tube S1 and the switch tube S5 are regarded as a whole, S1 and S5, as well as S2, combined with S3 and S4, form a full-bridge inverter circuit, thus forming a single-stage boost inverter circuit. The output of the inverter is filtered by the inductor L g After filtering out harmonics, it is connected to the grid.

[0055] like Figure 1 As shown, a dual-objective continuous set model predictive power decoupling control method includes the following steps:

[0056] S1, obtaining a mathematical model of the object to be predicted (boost inductor current and grid current) at discrete moments, discretizing the mathematical model to obtain a prediction model, and constructing the basic framework of the inner-loop model predictive control; the prediction model is used to calculate the predicted values ​​of the inductor current and grid current at the next moment;

[0057] After PWM modulation, with triangle wave as carrier, the filter inductor L g The current waveform of the boost inductor L rises linearly first, then drops linearly, and finally rises linearly again in one sampling (switching) cycle. The slopes of the three-segment inductor current changes of the boost inductor L are defined as fi1, fi2, and fi3 respectively, and the filter inductor L is defined as g The slopes of the three inductance changes are defined as f g1 、f g2 、f g3 The three time periods corresponding to the change of the boost inductor current are defined as t L 、(T s -t L ), t L The three time periods corresponding to the grid current change are defined as t g 、(T s -t g ), t g , where T s is the sampling period.

[0058] According to Kirchhoff's voltage law, Ohm's law and Faraday's law, the mathematical model is established as follows:

[0059]

[0060]

[0061] Where, f i1 ,f i2 ,f i3 They represent the slopes corresponding to the three changes in the boost inductor current, f g1 ,f g2 ,f g3 They represent the slopes corresponding to the three changes in grid-connected current, i L is the input current, U in is the input voltage, U C is the voltage of capacitor C, U ab is the bridge arm voltage, U g is the grid voltage, R L is the boost inductor parasitic impedance, R g is the parasitic impedance of the filter inductor, i g is the grid-connected current, L is the boost inductance value, L gFilter inductance value;

[0062] The prediction model can be further obtained, and the prediction model is used to calculate the predicted values of the inductor current and the grid-connected current at the next moment. The expression of the prediction model is:

[0063] i L (k+1) = i L (k) + 2f i1 t L +(T s -2t L )f i2 (7)

[0064] i g (k+1) = i g (k) + 2f g1 t g +(T s -2t g )f g2 (8)

[0065] wherein i L (k+1) and i g (k+1) are the predicted boost inductor current value and the grid-connected current value at the next moment, respectively, i g (k) and i L (k) are the grid-connected current and the boost inductor current sampled by the sampling module at the k moment, respectively, Ts is the sampling period, t L represents the time of the first rising of the boost inductor current, and t g represents the time of the first rising of the grid-connected current.

[0066] S2, obtaining the control input variables of the objects to be predicted (the boost inductor current and the grid-connected current) (the boost inductor current and the grid-connected current), setting a value function, obtaining the optimal conduction duty ratios of the boost side and the inverter side through the input variables and the predicted values calculated in S1, and completing the design of the inner loop model predictive control;

[0067] The value function is set as the square of the error between the reference current and the predicted value, and is used to find the optimal predicted value. The value function is:

[0068] J(t L ) = [i L_ref -i L (k+1)] 2 = f(t L ) (9)

[0069] J(t g ) = [i g_ref -i g (k+1)] 2 = f(tg ) (10)

[0070] where i L (k+1) and i g (k+1) are the predicted boost inductor current value and grid-connected current value at next time, i L_ref and i g_ref are the predicted inductor current and grid-connected current reference value, J(t L ) and J(t g ) are the cost functions, which are expressed as a single variable function f(t L ) and f(t g ) respectively.

[0071] Let to obtain the optimal time t L_best and t g_best :

[0072]

[0073] where t L_best is the optimal value of the first section of the boost inductor current rising time t L , t g_best is the optimal value of the first section of the grid-connected current rising time t g , i L (k) and i g (k) are the sampling values of the boost inductor current and grid-connected current at time k, f i1 , f i2 , and f i3 represent the slopes corresponding to the three sections of the boost inductor current change, f g1 , f g2 , and f g3 represent the slopes corresponding to the three sections of the grid-connected current change, where f i1 = f i3 , f g1 = f g3 .

[0074] The optimal duty cycles of the boost side and the inverter side are calculated as follows:

[0075]

[0076] where d S5 is the optimal duty cycle of the switch S5, and d is the optimal duty cycle of the grid-connected current working in the rising section within a period.

[0077] The duty cycle d S5 of the switch S5The on-off signal of the switch S5 can be directly generated by the PWM modulation module. Since there are two half cycles of working period in the inverter side, the d needs to be processed as follows:

[0078] Two intermediate variables d1 and d2 are defined. If the grid voltage U g >0, then d1=0, d2=d. If U g <0, then d1=d, d2=0. The modulation signal obtained by such processing is the duty ratio of the switch S3, and d2 is the duty ratio of the switch S1. The duty ratios d1 and d2 are directly subjected to PWM modulation to obtain the on-off signals of the switches S1 and S3. Since S4 and S3 are complementary, and S2 and S1 are complementary, the on-off signals of all the switches of the two bridge arms of the inverter side are obtained.

[0079] The PI voltage outer loop module is designed for S3 to obtain the input current and output current reference values required by the inner loop, and to build the basic framework of the PI control of the outer loop.

[0080] The PI voltage outer loop module is used for prediction error compensation.

[0081] Firstly, for the input side, the voltage outer loop is used to realize the DC input voltage following the reference voltage of MPPT (Maximum Power Point Tracking). Since the DC input voltage and the input current are one-to-one corresponding on the photovoltaic curve, the control of the input voltage U in can be realized by controlling the input inductor current i L . The output of the voltage outer loop PI controller is the reference value i L_ref of the input current, so as to realize the direct control of the photovoltaic input power.

[0082] For the output side, the voltage outer loop controls the average voltage U C_ave of the intermediate decoupling capacitor C to ensure the power balance between the input and output sides and that the system will not be over-modulated. When the input power increases, the average voltage U C_ave of the capacitor C increases. The difference between the average voltage of the capacitor and the reference value of the capacitor voltage is subjected to the PI controller, and then added to the feedforward value calculated from the input power to increase the reference value of the output current, so as to compensate the error value of the inner loop output prediction current.

[0083] Based on the PI voltage outer loop module designed for S3 and the optimal duty ratio obtained by S2, the voltage outer loop notch filter, the calculation of the reference current feedforward value, and the control and decoupling of the input current and the output current are designed for S4.

[0084] Because the capacitor voltage absorbs the double frequency ripple energy, the capacitor voltage sampling value has double frequency ripple, and after the PI controller, other low frequency ripples are introduced again, which will affect the output waveform quality, so a notch filter needs to be designed to realize the average value control of the capacitor voltage, so as to realize the decoupling control of the input current and the output current.

[0085] The function of the notch filter is to filter out the double frequency component of the intermediate decoupling capacitor voltage obtained by sampling and send it to the PI controller, one of the purposes is to avoid the double frequency component entering the PI controller to obtain the third harmonic, so that the output current reference value contains other component low harmonics, and the second purpose is to control the average value of the capacitor voltage. The transfer function of the double parameter notch filter is:

[0086]

[0087] Where s is a complex variable, representing a complex variable in the frequency domain. ω0is the target angular frequency of the notch, ω bw is the bandwidth of the notch filter.

[0088] The introduction of the reference current feedforward value is mainly to improve the dynamic performance of the system. The calculation of the output reference current feedforward value i g_front is as follows. The feedforward value is obtained according to the average power on the input side. According to the power conservation, P in = P g , P in is the input average power, P g is the output average power, and the peak-to-peak value of the grid voltage is U g , so the output reference current feedforward value is:

[0089] i g_front = 2P in / U g (16)

[0090] In the formula, i g_front is the output reference current feedforward value, P in is the input average power, and U g is the peak-to-peak value of the grid voltage.

[0091] The control decoupling of the double target, i.e. the input current and the output current, is as follows. Because the proposed single-stage boost inverter works in the negative half cycle, S5 is reused, i.e. the inverter and the boost need to pass through S5 control at the same time. Once the control quantities of the two conflict, the system will run out of control. Analysis shows that as long as the duty ratio d S5 of the boost side is greater than the duty ratio d 2_neg, the negative half cycle is inverted, S5 is on, and the control coupling will not be generated. The following formula derivation is carried out to calculate the reference value of the intermediate bus capacitor voltage, so as to realize d S5 >d 2_neg , and the control decoupling is realized.

[0092] When U g ≤ 0, let d 2_neg = m, m is the modulation ratio; according to the relationship between the modulation ratio and the voltage, the following formula is obtained:

[0093]

[0094] Wherein, U g is the peak-to-peak value of the grid voltage, and U C is the instantaneous value of the capacitor voltage; according to the boost relationship of the boost circuit, the following formula is obtained:

[0095]

[0096] According to the coupling relationship analyzed in the foregoing, d S5 >d 2_neg can realize control decoupling, that is:

[0097]

[0098] As long as the mean voltage reference value of the output side voltage outer loop is designed to satisfy the above formula, the control decoupling can be realized. Therefore, a certain margin is reserved, and the pulsating double-frequency power is absorbed by the decoupling capacitor C. As long as U C_ave_ref = U C + 50, and the above formula is satisfied, the control decoupling can be realized, wherein U C_ave_ref is the mean voltage reference value of the decoupling capacitor C.

[0099] Embodiment 2

[0100] In this embodiment, the control method of the application is tested and verified by simulation experiments.

[0101] Wherein, Figure 4 is the MATLAB simulation steady-state output current, input voltage and input current waveform effect diagram (the horizontal coordinate represents time, and the vertical coordinate represents the input and output current values) by applying the application. Figure 5 is the MATLAB simulation steady-state input current, input voltage and output current THD effect diagram (the horizontal coordinate represents the frequency value, and the vertical coordinate represents the harmonic distortion percentage relative to the fundamental wave) by applying the application. Figure 6 is the MATLAB simulation steady-state output capacitor voltage waveform diagram (the horizontal coordinate represents time, and the vertical coordinate represents the capacitor voltage value) by applying the application. Figure 7is the input current and output current dynamic response effect picture (the horizontal coordinate represents time, the vertical coordinate represents output voltage value; the solid gray line and the black line curve represent the reference current and the actual output current respectively, except for the middle small part, the rest are very close) in the MATLAB simulation of the application when the input power changes.

[0102] The specific simulation parameters are shown in Table 1:

[0103] Simulation parameters Parameter value Direct current input voltage V in ]]> 50V Filter inductance L g ]]> 5mH Grid voltage U g ]] AC 110V / 50HZ Decoupling capacitor C 100uF Sampling frequency 20kHZ Boost inductance L 4mH

[0104] The above algorithm is written into the FUNTION module of MATLAB through C language, the sampled variable value is input into the FUNTION module, and the switch combination at the current time is calculated and applied to the switch converter.

[0105] As shown in Figure 4 and Figure 5 , the input current, input voltage and output current waveform quality are good, and the current distortion rate is low. As shown in Figure 6 , the average control of the capacitor voltage also has excellent effect. According to Figure 7 , when the reference current value changes, the model predictive current control makes the system quickly transition to steady state, and has good dynamic performance.

[0106] Embodiment 3

[0107] In this embodiment, a dual-target continuous set model predictive power decoupling control system is disclosed, which specifically comprises:

[0108] The prediction model construction module: obtain the mathematical model of the discrete time of the to-be-predicted object (boost inductance current and grid-connected current), and perform discretization processing on the mathematical model to obtain a prediction model, and construct the basic framework of the model predictive control of the inner loop; wherein the prediction model is used to calculate the inductance current and grid-connected current prediction values at the next time;

[0109] The optimization module: obtains the control input variables of the to-be-predicted object (boost inductance current and grid-connected current), sets a value function, and obtains the optimal conduction duty ratio of the boost side and the inverter side through the input variables and the prediction values, to complete the design of the inner loop model predictive control;

[0110] The PI voltage outer loop design module: design a PI voltage outer loop module, obtain the input current and output current reference values required by the inner loop, and construct the basic framework of the PI control of the outer loop;

[0111] And the decoupling control module: based on the PI voltage outer loop and the optimal duty ratio, to design the notch filter in the voltage outer loop, calculate the feedforward value of the reference current, and control the decoupling of the input current and the output current.

[0112] The control method of the present application can be implemented in hardware, firmware, or as software or computer code that can be stored in a recording medium such as a CD ROM, a RAM, a floppy disk, a hard disk, or a magneto-optical disk, or be downloaded through a network originally stored in a remote recording medium or a non-transitory machine-readable medium and to be stored in a local recording medium, so that the method described herein can be processed by such software on a recording medium using a general purpose computer, a special purpose processor, or programmable or special purpose hardware such as an ASIC or an FPGA. It can be understood that the computer, processor, microprocessor controller, or programmable hardware includes a storage component (e.g., RAM, ROM, flash memory, etc.) that can store or receive software or computer code, which, when accessed and executed by the computer, processor, or hardware, implements the method described herein. Furthermore, when a general purpose computer accesses code for implementing the method shown herein, the execution of the code transforms the general purpose computer into a special purpose computer for executing the method shown herein.

[0113] The above shows and describes the basic principles, main features and advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above-mentioned embodiments, and the above-mentioned embodiments and descriptions in the specification are only to illustrate the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application.

Claims

1. A dual-objective continuous set model predictive power decoupling control method, characterized in that: The method is used to perform decoupling control on a grid-connected system including a single-stage boost photovoltaic inverter circuit, comprising the following steps: Obtaining a mathematical model of the boost inductor current and the grid-connected current, discretizing the mathematical model to obtain a prediction model, and calculating the predicted values ​​of the boost inductor current and the grid-connected current at the next moment; Obtaining control input variables of the boost inductor current and the grid-connected current, setting a value function, and obtaining the optimal on-duty ratio of the boost side and the inverter side through the input variables and the predicted values; Design the PI voltage outer loop to obtain the input current and output current reference values ​​required by the inner loop and perform prediction error compensation; Based on the PI voltage outer loop and the optimal duty cycle, a notch filter in the voltage outer loop is designed, a feedforward value of a reference current is calculated, and control decoupling of input current and output current is performed; The single-stage boost photovoltaic inverter circuit is constructed by combining a full-bridge inverter circuit with a bidirectional boost circuit to form a common ground structure, and has multiplexed switch tubes; the input side of the single-stage boost photovoltaic inverter circuit is connected to a photovoltaic panel or a DC source, and the output side is connected to the power grid; The single-stage boost photovoltaic inverter circuit includes: The single-stage boost photovoltaic inverter circuit includes: The circuit includes switch tubes S1-S5, capacitor C, input power supply U in , AC source U g , boost inductor L dc And the filter inductor L g ; Switch tubes S1, S5 and S2 are connected in series from top to bottom to form a group of bridge arms; switch tubes S3 and S4 are connected in series from top to bottom to form another group of bridge arms; the two groups of bridge arms are connected in parallel to form an inverter bridge; input power supply U in The positive terminal is directly connected to the boost inductor L dc connected, and its cathode is connected to the source of the switch tube S5; with a series equivalent resistor R L The boost inductor L dc Connect the input source U at both ends in The positive electrode and the drain of the switch tube S5; the AC source U g The two ends of the filter inductor L are directly connected g And input power U in The negative pole; with a series equivalent resistance R g The filter inductor L g One end is connected to the AC source U g , the other end is connected to the source of the switch tube S3; The mathematical model is: Where, f i1 ,f i2 ,f i3 They represent the slopes corresponding to the three changes in the boost inductor current, f g1 ,f g2 ,f g3 They represent the slopes corresponding to the three changes in grid-connected current; i L is the input current, U C is the voltage of capacitor C, U in is the input voltage, U ab is the bridge arm voltage, U g is the grid voltage, R L is the boost inductor parasitic impedance, R g is the parasitic impedance of the filter inductor, i g is the grid-connected current, L is the boost inductance value, L g is the filter inductance value; The optimal duty cycle calculation formula for the boost side and the inverter side is: Where, d S5 is the calculated optimal duty cycle of the switch tube S5, d is the calculated optimal duty cycle of the grid-connected current working in the rising range within one cycle; i L_ref and i g_ref are the predicted inductor current and grid current reference values ​​respectively; i g (k) and i L (k) are the grid-connected current and boost inductor current sampled by the sampling module at time k, T s is the sampling period; The duty cycle d of the switch tube S5 S5 The PWM modulation module directly generates the turn-on signal of the switch tube S5. Since the inverter side has two positive and negative half-cycle working cycles, d is processed as follows: Define two intermediate variables d1 and d2. If the grid voltage U g >0, then d1=0, d2=d, if U g <0, then d1=d, d2=0; in the modulated signal obtained by this processing, d1 is the duty cycle of the switch tube S3, and d2 is the duty cycle of the switch tube S1. The duty cycles d1 and d2 are directly PWM modulated to obtain the conduction signals of S1 and S3. Because S4 and S3 are complementary, and S2 and S1 are complementary, the conduction signals of all the switch tubes in the two bridge arms of the inverter side are obtained; The process of using the PI voltage outer loop to perform prediction error compensation includes: For the input side, the voltage outer loop is used to make the DC input voltage follow the reference voltage of the MPPT. The output of the voltage outer loop PI controller is the reference value of the input current i L_ref ; For the output side, the voltage outer loop controls the average voltage U of the intermediate decoupling capacitor C. C_ave , to ensure the power balance between the input and output sides and the system will not be over-modulated. When the input power increases, the average voltage U of the capacitor C C_ave Increase, the average value of the capacitor voltage is subtracted from the capacitor voltage reference value, and after passing through the PI controller, the feedforward value calculated by the input power is added, and the reference value of the output current increases, thereby compensating for the error value of the inner loop output prediction current; When the mean voltage reference value of the output voltage outer loop satisfies the following formula, the control decoupling of the input current and output current can be achieved: Where U g is the peak-to-peak value of the grid voltage, U C is the instantaneous value of the capacitor voltage, U in is the input voltage.

2. The method for predicting power decoupling control based on a dual-objective continuous set model according to claim 1, characterized in that: The calculation formula for the predicted values ​​of the inductor current and grid-connected current at the next moment is: i L (k+1)=i L (k)+2f i1 t L +(T s -2t L )f i2 i g (k+1)=i g (k)+2f g1 t g +(T s -2t g )f g2 Among them, i L (k+1) and i g (k+1) are the predicted inductor current value and grid current value at the next moment, t L Indicates the time of the first rise of the boost inductor current, t g Indicates the time of the first rise of the grid-connected current.

3. A dual-objective continuous set model predictive power decoupling control system capable of executing the control method according to claim 1 or 2, characterized in that: include: Prediction model building module: obtains the mathematical model of the boost inductor current and grid current at discrete moments, discretizes the mathematical model to obtain a prediction model, and calculates the predicted values ​​of the inductor current and grid current at the next moment; Optimization module: obtains control input variables of the boost inductor current and the grid-connected current, sets a value function, and obtains the optimal conduction duty cycle of the boost side and the inverter side through the input variables and the predicted values; PI voltage outer loop design module: Designs the PI voltage outer loop, obtains the input current and output current reference values ​​required by the inner loop, and performs prediction error compensation; And, a control decoupling module: based on the PI voltage outer loop and the optimal duty cycle, designs a notch filter in the voltage outer loop, calculates a feedforward value of a reference current, and performs control decoupling of input current and output current.

4. A computer storage medium storing a readable program, characterized in that: When the program is running, it can execute the dual-objective continuous set model predictive power decoupling control method described in any one of claims 1-2.

5. An electronic device, characterized in that: include: A processor, a memory, a communication interface, and a communication bus, wherein the processor, the memory, and the communication interface communicate with each other via the communication bus; The memory is used to store at least one executable instruction, and the executable instruction enables the processor to perform operations corresponding to a dual-objective continuous set model prediction power decoupling control method as described in any one of claims 1-2.

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