Impedance modeling method for optical storage hybrid power generation system

Abstract

The invention discloses an impedance modeling method for an optical storage hybrid power generation system, and the method comprises the steps: building a photovoltaic power generation unit equivalent output impedance model based on a preset photovoltaic power generation unit control strategy; based on a preset energy storage unit control strategy, establishing an energy storage unit equivalent output impedance model; based on a preset harmonic linearization control strategy, establishing an AC-DC side small signal coupling model of the control unit of the optical storage inverter; and fusing the equivalent output impedance model of the photovoltaic power generation unit, the equivalent output impedance model of the energy storage unit and the AC / DC side small signal coupling model of the optical storage inverter control unit to construct an impedance model of the optical storage hybrid power generation system. According to the method, the coupling influence of photovoltaic and energy storage unit impedance on the output impedance characteristic of the optical storage converter is considered, so that a more accurate optical storage power generation system impedance model is established, meanwhile, the method is also suitable for judging the system stability under a weak network condition, and the application of the impedance model in an optical storage power generation scene is better realized.

Description

Technical Field

[0001] The invention relates to the technical field of photovoltaic power generation and storage, and in particular discloses an impedance modeling method for a photovoltaic power generation system. Background Art

[0002] In recent years, with the vigorous development of renewable energy, wind power and photovoltaic power generation have become the main research hotspots. The randomness and volatility of new energy power generation pose a threat to the stable operation of the power grid, while photovoltaic and storage hybrid power generation can effectively smooth the fluctuations of the power grid and participate in the peak and frequency regulation of the power grid. In order to ensure the operational reliability of the grid-connected power system of the new energy system and reduce the oscillation risk generated by the system, it is particularly necessary to study the operational stability of the photovoltaic and storage system, that is, the impedance characteristics. At present, many scholars have conducted research in the following directions: equivalent the capacitance of the photovoltaic and storage converter to infinity, ignoring the AC and DC side coupling characteristics, and establishing its impedance model; or equivalent the photovoltaic and storage power generation system to establish an impedance model when it is in stable operation, ignoring the influence of the dynamic characteristics of the impedance of the photovoltaic array and the energy storage battery itself on the output impedance of the photovoltaic and storage system.

[0003] Titled "Modeling of Frequency Coupling Characteristics of Grid-connected Inverters and Analysis of System Stability", the Proceedings of the CSEE, Vol. 39, No. 5, 2019, article number: 0258-8013(2019), 05-1421-11, establishes a frequency coupling characteristic model of a grid-connected inverter that takes into account factors such as the asymmetry of the phase-locked loop, DC voltage loop, and current control loop. Compared with the previous admittance matrix model, it is simpler and easier to calculate.

[0004] Entitled "Modeling and Characteristic Analysis of Photovoltaic Power Generation Impedance Considering Photovoltaic Arrays", "Proceedings of the CSEE 2023", the article takes into account the influence of irradiance and temperature on the output impedance of the photovoltaic array, establishes the impedance model of its photovoltaic power generation system, and reveals the influence of the dynamic characteristics of the photovoltaic array on the output impedance of the AC side of the photovoltaic power generation.

[0005] In summary, there is currently a lack of research on the influence of the impedance characteristics of the photovoltaic storage system on the coupling mechanism of the AC side impedance characteristics of the photovoltaic storage converter, which is of great significance for further research on the stability of the grid-connected operation of the photovoltaic storage system in the future. Summary of the invention

[0006] The present invention provides an impedance modeling method for a photovoltaic-storage hybrid power generation system, aiming to solve the current technical problem of considering the influence of the coupling mechanism of the impedance characteristics of the photovoltaic-storage system on the impedance characteristics of the AC side of the photovoltaic-storage converter, which is still in a blank.

[0007] The present invention relates to an impedance modeling method for a photovoltaic-storage hybrid power generation system, comprising the following steps:

[0008] Based on the preset photovoltaic power generation unit control strategy, an equivalent output impedance model of the photovoltaic power generation unit is established;

[0009] Based on the preset energy storage unit control strategy, an equivalent output impedance model of the energy storage unit is established;

[0010] Based on the preset harmonic linearization control strategy, a small signal coupling model of the AC and DC sides of the photovoltaic energy storage inverter control unit is established;

[0011] The equivalent output impedance model of the photovoltaic power generation unit, the equivalent output impedance model of the energy storage unit and the small signal coupling model of the AC and DC sides of the photovoltaic and energy storage inverter control unit are integrated to construct the impedance model of the photovoltaic and energy storage hybrid power generation system.

[0012] Further, based on the preset photovoltaic power generation unit control strategy, in the step of establishing the photovoltaic power generation unit equivalent output impedance model, the photovoltaic power generation unit equivalent output impedance model is:

[0013]

[0014] Among them, Z pv is the equivalent output impedance of the photovoltaic power generation unit, is the small signal variable of the DC bus voltage, is the small signal variable of the average current output from the photovoltaic unit to the DC bus, s is the Laplace differential operator, L dc is the boost inductor, G idc is the current control loop transfer function, G delay is the digital control delay, v bus is the DC bus voltage, R pv is the equivalent resistance of the photovoltaic unit, i pv is the inductor current, and d is the duty cycle.

[0015] Furthermore, based on the preset energy storage unit control strategy, in the step of establishing an equivalent output impedance model of the energy storage unit, the equivalent output impedance model of the energy storage unit is:

[0016]

[0017] Among them, Z bat is the equivalent output impedance modulus of the energy storage unit, s is the Laplace differential operator, L dc is the boost inductor, G idc is the current control loop transfer function, G delay For digital delay control, v bus is the DC bus voltage, R bat is the equivalent resistance of the battery, i bat is the inductor current, and d is the duty cycle.

[0018] Further, based on the preset harmonic linearization control strategy, in the step of establishing the AC and DC side small signal coupling model of the photovoltaic storage inverter control unit, the AC and DC side small signal coupling model of the photovoltaic storage inverter control unit is:

[0019]

[0020] in, is the inverter a phase output current small signal, for The positive sequence component of for The negative sequence component of the matrix, T is the transpose of the matrix, I gp is the amplitude of the positive sequence component, I gp2 is the amplitude of the positive sequence component, e is the natural number base in Euler's formula, j is the imaginary unit, is the positive sequence component of the current small signal The phase of is the negative sequence component of the current small signal phase.

[0021] Furthermore, the equivalent output impedance model of the photovoltaic power generation unit, the equivalent output impedance model of the energy storage unit and the AC / DC side small signal coupling model of the photovoltaic storage inverter control unit are integrated to construct the impedance model of the photovoltaic storage hybrid power generation system. The impedance model of the photovoltaic storage hybrid power generation system includes the expression of the AC port admittance of the photovoltaic storage inverter taking into account the output impedance of the photovoltaic storage hybrid power generation. The expression of the AC port admittance of the energy storage inverter is:

[0022]

[0023] Among them, Y pv is a 2*2-order matrix, Λ1 is the small signal of the inverter AC port when the DC bus voltage is constant and current response small signal The transfer coefficient between them, Λ2 is the small signal of DC bus voltage The current response to the small signal The transfer coefficient, P v is the small voltage signal on the AC side and the small power signal on the DC side The transitive relationship, P i is the small current signal on the AC side and the small power signal on the DC side The transfer relationship, I is the unit 2*2 order unit matrix, F(Z dc ) is the DC side power small signal considering the small signal impedance model of the photovoltaic storage unit To DC voltage small signal The transitive relationship, Y cf is a 2*2 order diagonal matrix of filter capacitors, expressed as Y cf=j2πC f ·diag[f p , f p -2f1].

[0024] Furthermore, the equivalent output impedance model of the photovoltaic power generation unit, the equivalent output impedance model of the energy storage unit and the AC / DC side small signal coupling model of the photovoltaic storage inverter control unit are integrated to construct the photovoltaic storage hybrid power generation system impedance model. The coefficients Λ1 and Λ2 are calculated by the following formulas:

[0025]

[0026] Where Λ1 is the small signal of AC voltage on the inverter side when the DC bus voltage is constant. Its current response is small signal The transfer coefficient between m is the modulation coefficient, V dc is the steady-state component of the DC bus voltage, T PLL (s1) is the phase-locked loop transfer function, H gi (s1) is the current controller transfer function, j is the imaginary unit, K gd is the decoupling coefficient, I g1 is the vector expression of the steady-state current, M1 is the fundamental frequency component represented by the modulation signal, s is the Laplace differential operator, L f is the AC side inductance, I * g1 is the conjugate of the vector expression for the steady-state current, M1 * is the conjugate of the fundamental frequency component represented by the modulated signal, s2=j2π(f p -2f1), f p is the disturbance frequency, f1 is the fundamental frequency;

[0027]

[0028] Among them, Λ2 is the small signal of bus voltage Small signal with current response The coefficient is mainly related to the voltage outer loop, current loop and PWM modulation ratio; K m is the modulation coefficient, V dc is the steady-state component of the DC bus voltage, H gi (s1) is the current controller transfer function, H vdc (s1) is the voltage controller transfer function, M g1 represents the fundamental frequency component of the modulated signal, s = j2πf1, L f is the AC side inductance, j is an imaginary unit, K gd is the decoupling coefficient, M * g1is the conjugate of the fundamental frequency component of the modulated signal, s2=j2π(f p -2f1), f p is the disturbance frequency, f1 is the fundamental frequency.

[0029] Furthermore, the equivalent output impedance model of the photovoltaic power generation unit, the equivalent output impedance model of the energy storage unit and the AC / DC side small signal coupling model of the photovoltaic storage inverter control unit are integrated to construct the impedance model of the photovoltaic storage hybrid power generation system. v and P i Calculated by the following formula:

[0030]

[0031] Among them, P V is the small voltage signal on the AC side and the small power signal on the DC side The transitive relationship, I ga is the steady-state value of inverter phase a output, I * ga is the conjugate of the inverter a-phase output steady-state value, P i is the transmission relationship between the AC side current small signal and the DC power small signal, V ga is the inverter modulation voltage steady-state value, V * ga is the conjugate of the inverter modulation voltage steady-state value, s = j2πf p , s2=j2π(f p -2f1), f p is the disturbance frequency, f1 is the fundamental frequency, L f is the AC side inductance, and T is the matrix transpose.

[0032] Furthermore, the equivalent output impedance model of the photovoltaic power generation unit, the equivalent output impedance model of the energy storage unit and the AC / DC side small signal coupling model of the photovoltaic storage inverter control unit are integrated to construct the impedance model of the photovoltaic storage hybrid power generation system. dc ) is calculated by the following formula:

[0033]

[0034] Among them, F(Z dc ) is the DC side power small signal considering the impedance of the photovoltaic storage unit and the DC bus capacitor To the DC side voltage small signal The transitive relationship, F1(sC dc ) is the DC bus capacitor impedance at the DC side power small signal To the DC side voltage small signal The transitive relationship, F2(Z pv) is the small power signal of the photovoltaic unit on the DC side To the DC side voltage small signal The transitive relationship, F3(Z bat ) is the small power signal of the energy storage unit on the DC side To the DC side voltage small signal The transfer relationship, V dc is the DC bus capacitor steady-state voltage, Z pv is the equivalent output impedance of the photovoltaic power generation unit, Z bat is the equivalent output impedance of the energy storage power generation unit, s1=j2π(f p -f1) where f p is the disturbance frequency, f1 is the fundamental frequency, C dc is the DC bus capacitance, I dc is the DC bus steady-state current, V dc is the DC bus steady-state voltage.

[0035] The beneficial effects achieved by the present invention are:

[0036] The present invention provides an impedance modeling method for a photovoltaic-storage hybrid power generation system, by establishing an equivalent output impedance model of a photovoltaic power generation unit based on a preset photovoltaic power generation unit control strategy; establishing an equivalent output impedance model of an energy storage unit based on a preset energy storage unit control strategy; establishing a small signal coupling model of the AC and DC sides of a photovoltaic-storage inverter control unit based on a preset harmonic linearization control strategy; integrating the equivalent output impedance model of the photovoltaic power generation unit, the equivalent output impedance model of the energy storage unit and the small signal coupling model of the AC and DC sides of the photovoltaic-storage inverter control unit to construct an impedance model of the photovoltaic-storage hybrid power generation system. The impedance modeling method for a photovoltaic-storage hybrid power generation system provided by the present invention takes into account the coupling effect of the impedance of the photovoltaic and energy storage units on the output impedance characteristics of the photovoltaic-storage inverter, thereby establishing a more accurate impedance model of the photovoltaic-storage power generation system, and is also suitable for determining the stability of the system under weak network conditions, thereby better realizing the application of the impedance model in photovoltaic-storage power generation scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a schematic flow chart of the impedance modeling method of the photovoltaic storage hybrid power generation system of the present invention;

[0038] Figure 2 It is a schematic diagram of the control strategy of the photovoltaic power generation unit of the present invention;

[0039] Figure 3 It is a schematic diagram of the control strategy of the energy storage unit of the present invention;

[0040] Figure 4 This is a schematic diagram of a control unit of a photovoltaic storage inverter according to the present invention;

[0041] Figure 5Schematic diagram of the topological structure of the optical storage system of the present invention;

[0042] Figure 6 This is a small signal transmission relationship diagram of the photovoltaic power generation system of the present invention. DETAILED DESCRIPTION

[0043] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0044] like Figure 1 As shown, the present invention proposes an impedance modeling method for a photovoltaic storage hybrid power generation system, comprising the following steps:

[0045] Step S100: establishing an equivalent output impedance model of a photovoltaic power generation unit based on a preset photovoltaic power generation unit control strategy.

[0046] Please see Figures 2 to 5 , the MPPT (Maximum Power Point Tracking) control strategy is adopted to establish the equivalent output impedance model of the photovoltaic power generation unit.

[0047] Step S200: establishing an energy storage unit equivalent output impedance model based on a preset energy storage unit control strategy.

[0048] The battery is equivalent to a voltage source, and the internal resistance of the photovoltaic and battery is taken into account respectively (the influence of temperature, light, battery aging and other factors on the internal resistance are not considered), and the equivalent output impedance models of the photovoltaic and energy storage units are established respectively from the DC bus end using the small signal method.

[0049] Step S300: Based on a preset harmonic linearization control strategy, a small signal coupling model of the AC and DC sides of the photovoltaic energy storage inverter control unit is established.

[0050] The harmonic linearization method is used to establish the small signal coupling model of the AC and DC sides of the photovoltaic storage converter. A small signal disturbance is superimposed on the steady-state operating point of the system grid voltage to establish a frequency domain linearized impedance model. The photovoltaic storage inverter control unit is modeled using multi-harmonic linearization.

[0051] The photovoltaic storage model adopts a common bus topology and control strategy. The BOOST boost circuit used by the photovoltaic unit and the energy storage unit is basically the same, but the internal resistance of the photovoltaic and energy storage units is different. pv and R bat They represent the equivalent resistance of the battery in the photovoltaic system (excluding factors such as temperature, light, and battery aging). pv and v bat are the electromotive force in the photovoltaic system and the battery respectively. pv and i bat is the inductor current, ipvbus and i batbus is the average current of the photovoltaic and energy storage units flowing into the DC bus in one cycle, V pv The voltage of the photovoltaic power generation port. G vdc , G idc Both use PI (proportional integral) control, G delay (s) is the control delay link generated by PMW (Pulse Width Modulation) control.

[0052] Step S400, the photovoltaic power generation unit equivalent output impedance model, the energy storage unit equivalent output impedance model and the AC and DC side small signal coupling model of the photovoltaic storage inverter control unit are integrated to construct an impedance model of the photovoltaic storage hybrid power generation system.

[0053] The established photovoltaic power generation unit equivalent output impedance model, energy storage unit equivalent output impedance model and AC / DC side small signal coupling model of the photovoltaic and energy storage inverter control unit are integrated to construct a common bus topology structure of the photovoltaic and energy storage hybrid power generation system impedance model.

[0054] The impedance model of the photovoltaic and energy storage hybrid power generation system adopts a system topology structure, which includes three parts: photovoltaic power generation, energy storage, and grid-connected converter. a 、v b 、v c is the grid connection point voltage, i ga 、i gb 、i gc is the output current of the grid-connected converter, i ca 、i cb 、i cc is the three-phase filter capacitor voltage, L f and C f are the filter inductors and capacitors. PLL is the phase angle collected by the phase-locked loop at the grid-connected point voltage, V dcref is the DC bus voltage command value, which is provided by the photovoltaic MPPT algorithm and the energy storage battery BMS (Battery Management System). d 、v q ,i d 、i q are d-axis and q-axis voltage and current, respectively, H gi (s), H vdc (s) are the PI controller transfer functions of the inner current loop and the outer DC voltage loop, i dref 、i qref are the d-axis and q-axis reference currents obtained by the DC bus voltage outer loop PI controller. gd is the current loop decoupling coefficient.

[0055] Furthermore, in the impedance modeling method of the photovoltaic-storage hybrid power generation system proposed in this embodiment, in step S100, in the equivalent output impedance model of the photovoltaic power generation unit, it is assumed that the internal resistance R of the photovoltaic power generation pv is a fixed value, ignoring the influence of nonlinear changes caused by external factors such as temperature and light, the equivalent impedance of the photovoltaic unit is obtained by the small signal method:

[0056]

[0057] In formula (1), Z pv is the equivalent output impedance of the photovoltaic power generation unit, is the small signal variable of the DC bus voltage, is the small signal variable of the average current output from the photovoltaic unit to the DC bus, s is the Laplace differential operator, L dc is the boost inductor, G idc is the current control loop transfer function, G delay is the digital control delay, v bus is the DC bus voltage, R pv is the equivalent resistance of the photovoltaic unit, i pv is the inductor current, and d is the duty cycle.

[0058] Preferably, in the impedance modeling method of the photovoltaic storage hybrid power generation system proposed in this embodiment, in step S200, similarly, R bat In order to ignore the influence of battery temperature, aging and other factors, assuming that the internal resistance of the battery is a constant, the equivalent output impedance model of the energy storage unit is established as follows:

[0059]

[0060] In formula (2), Z bat is the equivalent output impedance modulus of the energy storage unit, s is the Laplace differential operator, L dc is the boost inductor, G idc is the current control loop transfer function, G delay For digital delay control, v bus is the DC bus voltage, R bat is the equivalent resistance of the battery, i bat is the inductor current, and d is the duty cycle.

[0061] Furthermore, in the impedance modeling method of the photovoltaic-storage hybrid power generation system proposed in this embodiment, in step S300, a harmonic linearization method is used to establish a small signal coupling model of the AC and DC sides of the photovoltaic-storage converter, a small signal disturbance is superimposed at the steady-state operating point of the system grid voltage, and a frequency domain linearized impedance model is established. The inverter unit of the photovoltaic-storage converter adopts multi-harmonic linearization modeling, and the steady-state values ​​and small signal models of the voltage and current on the AC and DC sides of the photovoltaic-storage converter are defined as follows:

[0062]

[0063] In formula (3), V a is the steady-state value of phase a voltage at the grid connection point, V1 is the vector value of the voltage fundamental wave; V1 * is the conjugate of the vector value of the voltage fundamental wave; e is the natural number base in Euler's formula; j is a complex operator; is the phase of the voltage fundamental.

[0064]

[0065] In formula (4), I ga is the steady-state value of phase a voltage at the grid connection point, I g1 is the vector value of the voltage fundamental wave; I g1 * is the conjugate of the vector value of the voltage fundamental wave; e is the natural number base in Euler's formula; j is a complex operator; is the phase of the voltage fundamental.

[0066]

[0067] In formula (5), is the small voltage signal of phase a at the grid connection point, for The positive sequence component of for The negative sequence component of p The amplitude of the positive sequence component of the small signal of the phase voltage at the grid connection point a; e is the natural number base in the Euler formula; j is the imaginary unit; is the positive sequence component of the current small signal Phase; V p2 is the negative sequence component of the small signal of phase a voltage at the grid connection point The amplitude of is the negative sequence component of the current small signal phase.

[0068]

[0069] In formula (6), is the inverter a phase output current small signal, for The positive sequence component of for The negative sequence component of the matrix, T is the transpose of the matrix, I gp is the amplitude of the positive sequence component, I gp2 is the amplitude of the positive sequence component, e is the natural number base in Euler's formula, j is the imaginary unit, is the positive sequence component of the current small signal The phase of is the negative sequence component of the current small signal Phase. V dc , I dc is the steady-state value of the voltage and current on the DC side of the photovoltaic energy storage inverter; —Small voltage and current signals on the DC side of the photovoltaic energy storage inverter.

[0070] A small positive sequence voltage disturbance signal is superimposed at the steady-state operating point of the photovoltaic energy storage system connected to the grid. The frequency is f p According to the linear circuit superposition principle, the small signal current at the output of the photovoltaic inverter is is the output small signal current of the inverter when the DC bus voltage is constant Small signal current generated by DC bus voltage fluctuation When the DC bus voltage change is not considered, the voltage small signal The small current signal output after the phase-locked loop, current inner loop controller and PWM modulation is: and The transfer function between is represented by Λ1. The AC side outputs a small signal current and Active power fluctuations are generated. According to the AC-DC power balance principle, a small DC power signal is generated on the DC side. With voltage small signal and current small signal The transfer coefficients between them are P V and P i . DC power small signal Further analysis of the AC voltage small signal and AC current small signal The impact and transmission relationship are respectively expressed as P v and P i When the DC side impedance is only composed of the DC bus capacitance C dc Composition, DC power small signal And DC voltage small signal The impedance transfer relationship between them is F1(sC dc If the output impedance characteristics of photovoltaic power generation and battery power generation are taken into account and are connected in parallel with the DC bus capacitor, the transfer relationship is simplified to F2(Z pv )+F3(Z bat ). DC voltage small signal After the DC voltage outer loop and the current loop are decoupled, the small current signal of the AC output port is obtained through PWM modulation. The transfer function is represented by Λ2.

[0071] Preferably, see Figures 1 to 6In the impedance modeling method of the photovoltaic-storage hybrid power generation system proposed in this embodiment, in step S400, the impedance model of the photovoltaic-storage hybrid power generation system includes an expression of the AC port admittance of the photovoltaic-storage inverter taking into account the output impedance of the photovoltaic-storage hybrid power generation, and the expression of the AC port admittance of the storage inverter is:

[0072]

[0073] Y in formula (7) pv is a 2*2-order matrix, Λ1 is the small signal of the inverter AC port when the DC bus voltage is constant and current response small signal The transfer coefficient between them, Λ2 is the small signal of DC bus voltage The current response to the small signal The transfer coefficient, P v is the small voltage signal on the AC side and the small power signal on the DC side The transitive relationship, P i is the small current signal on the AC side and the small power signal on the DC side The transfer relationship, I is the unit 2*2 order unit matrix, F(Z dc ) is the DC side power small signal considering the small signal impedance model of the photovoltaic storage unit To DC voltage small signal The transitive relationship, Y cf is a 2*2 order diagonal matrix of filter capacitors, expressed as Y cf =j2πC f ·diag[f p , f p -2f1].

[0074] The coefficients Λ1 and Λ2 are calculated by the following formula:

[0075]

[0076] In formula (8), Λ1 is the small signal of the AC voltage on the inverter side when the DC bus voltage is constant. Its current response is small signal The transfer coefficient between m is the modulation coefficient, V dc is the steady-state component of the DC bus voltage, T PLL (s1) is the phase-locked loop transfer function, H gi (s1) is the current controller transfer function, j is the imaginary unit, K gd is the decoupling coefficient, I g1 is the vector expression of the steady-state current, M1 is the fundamental frequency component represented by the modulation signal, s is the Laplace differential operator, L f is the AC side inductance, I *g1 is the conjugate of the vector expression for the steady-state current, M1 * is the conjugate of the fundamental frequency component represented by the modulated signal, s2=j2π(f p -2f1), where f p is the disturbance frequency, f1 is the fundamental frequency;

[0077]

[0078] In formula (9), Λ2 is the small signal of bus voltage Small signal with current response The coefficient is mainly related to the voltage outer loop, current loop and PWM modulation ratio; K m is the modulation coefficient, V dc is the steady-state component of the DC bus voltage, H gi (s1) is the current controller transfer function, H vdc (s1) is the voltage controller transfer function, M g1 represents the fundamental frequency component of the modulated signal, s = j2πf1, L f is the AC side inductance, j is an imaginary unit, K gd is the decoupling coefficient, M * g1 is the conjugate of the fundamental frequency component of the modulated signal, s2=j2π(f p -2f1), where f p is the disturbance frequency, f1 is the fundamental frequency.

[0079] The active power balance equation of the AC and DC sides of the photovoltaic storage converter is obtained: According to the model solution:

[0080]

[0081] In formula (10), P V is the small voltage signal on the AC side and the small power signal on the DC side The transitive relationship, I ga is the steady-state value of inverter phase a output, I * ga is the conjugate of the inverter a-phase output steady-state value, P i is the transmission relationship between the AC side current small signal and the DC power small signal, V ga is the inverter modulation voltage steady-state value, V * ga is the conjugate of the inverter modulation voltage steady-state value, s = j2πf p , s2=j2π(f p -2f1), where f p is the disturbance frequency, f1 is the fundamental frequency, L fis the AC side inductance, and T is the matrix transpose.

[0082] Coefficient F(Z dc ) represents a small DC power signal With DC voltage small signal The transfer relationship is calculated by writing the DC power small signal equation at the DC bus capacitor steady-state operating point:

[0083]

[0084] In formula (11), is the DC side power small signal, V dc and I dc are the steady-state values ​​of DC voltage and current, respectively, is a small DC current signal, expressed as is a small DC voltage signal; Z dc To consider the generation side impedance of the photovoltaic storage and DC bus capacitor.

[0085] The DC power small signal equation can be transformed into:

[0086]

[0087] In formula (12), is the DC side power small signal, V dc and I dc are the steady-state values ​​of DC voltage and current, respectively, It represents the inverse of the small signal impedance on the DC side. is the inverse of the DC side steady-state impedance, is the small signal of DC bus voltage.

[0088] The DC side impedance is composed of the DC bus capacitor, photovoltaic unit, and energy storage single impedance in parallel, which can be expressed as:

[0089]

[0090] In formula (13), F(Z dc ) is the DC side power small signal considering the impedance of the photovoltaic storage unit and the DC bus capacitor To the DC side voltage small signal The transitive relationship, F1(sC dc ) is the DC bus capacitor impedance at the DC side power small signal To the DC side voltage small signal The transitive relationship, F2(Z pv ) is the small power signal of the photovoltaic unit on the DC side To the DC side voltage small signal The transitive relationship, F3(Z bat) is the small power signal of the energy storage unit on the DC side To the DC side voltage small signal The transfer relationship, V dc is the DC bus capacitor steady-state voltage, Z pv is the equivalent output impedance of the photovoltaic power generation unit, Z bat is the equivalent output impedance of the energy storage power generation unit, s1=j2π(f p -f1), f p is the disturbance frequency, f1 is the fundamental frequency, C dc is the DC bus capacitance, I dc is the DC bus steady-state current, V dc is the DC bus steady-state voltage.

[0091] Compared with the prior art, the impedance modeling method for the photovoltaic-storage hybrid power generation system provided in this embodiment establishes an equivalent output impedance model of the photovoltaic power generation unit based on a preset photovoltaic power generation unit control strategy; establishes an equivalent output impedance model of the energy storage unit based on a preset energy storage unit control strategy; establishes a small signal coupling model of the AC and DC sides of the photovoltaic-storage inverter control unit based on a preset harmonic linearization control strategy; and integrates the equivalent output impedance model of the photovoltaic power generation unit, the equivalent output impedance model of the energy storage unit, and the small signal coupling model of the AC and DC sides of the photovoltaic-storage inverter control unit to construct an impedance model of the photovoltaic-storage hybrid power generation system. The impedance modeling method for the photovoltaic-storage hybrid power generation system provided in this embodiment takes into account the coupling effect of the impedance of the photovoltaic and energy storage units on the output impedance characteristics of the photovoltaic-storage inverter, thereby establishing a more accurate impedance model of the photovoltaic-storage power generation system. It is also suitable for determining the stability of the system under weak network conditions, and better realizes the application of the impedance model in photovoltaic-storage power generation scenarios.

[0092] Although preferred embodiments of the present invention have been described, additional changes and modifications may be made to these embodiments by those skilled in the art once the basic inventive concepts are known. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention. Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for impedance modeling of photovoltaic and energy storage hybrid power generation system. It is characterized in that The following steps are involved: Based on the preset photovoltaic power generation unit control strategy, an equivalent output impedance model of the photovoltaic power generation unit is established; Based on the preset energy storage unit control strategy, an equivalent output impedance model of the energy storage unit is established; Based on the preset harmonic linearization control strategy, a small signal coupling model of the AC and DC sides of the photovoltaic energy storage inverter control unit is established; The photovoltaic power generation unit equivalent output impedance model, the energy storage unit equivalent output impedance model and the AC and DC side small signal coupling model of the photovoltaic storage inverter control unit are integrated to construct an impedance model of the photovoltaic storage hybrid power generation system.

2. The impedance modeling method of the photovoltaic-storage hybrid power generation system according to claim 1, It is characterized in that In the step of establishing an equivalent output impedance model of a photovoltaic power generation unit based on a preset photovoltaic power generation unit control strategy, the equivalent output impedance model of the photovoltaic power generation unit is: Among them, Z pv is the equivalent output impedance of the photovoltaic power generation unit, is the small signal variable of the DC bus voltage, is the small signal variable of the average current output from the photovoltaic unit to the DC bus, s is the Laplace differential operator, L dc is the boost inductor, G idc is the current control loop transfer function, G delay is the digital control delay, v bus is the DC bus voltage, R pv is the equivalent resistance of the photovoltaic unit, i pv is the inductor current, and d is the duty cycle.

3. The impedance modeling method of the photovoltaic-storage hybrid power generation system according to claim 1, It is characterized in that In the step of establishing an energy storage unit equivalent output impedance model based on a preset energy storage unit control strategy, the energy storage unit equivalent output impedance model is: Among them, Z bat is the equivalent output impedance modulus of the energy storage unit, s is the Laplace differential operator, L dc is the boost inductor, G idc is the current control loop transfer function, G delay For digital delay control, v bus is the DC bus voltage, R bat is the equivalent resistance of the battery, i bat is the inductor current, and d is the duty cycle.

4. The impedance modeling method of the photovoltaic-storage hybrid power generation system according to claim 1, It is characterized in that In the step of establishing the AC and DC side small signal coupling model of the photovoltaic storage inverter control unit based on the preset harmonic linearization control strategy, the AC and DC side small signal coupling model of the photovoltaic storage inverter control unit is: in, is the inverter a phase output current small signal, for The positive sequence component of for The negative sequence component of T is the transpose of the matrix, I gp is the amplitude of the positive sequence component, I gp2 is the amplitude of the positive sequence component, e is the natural number base in Euler's formula, j is the imaginary unit, is the positive sequence component of the current small signal The phase of is the negative sequence component of the current small signal phase.

5. The impedance modeling method of the photovoltaic hybrid power generation system according to claim 1, It is characterized in that In the step of integrating the photovoltaic power generation unit equivalent output impedance model, the energy storage unit equivalent output impedance model and the AC and DC side small signal coupling model of the photovoltaic storage inverter control unit to construct a photovoltaic storage hybrid power generation system impedance model, the photovoltaic storage hybrid power generation system impedance model includes an expression for the photovoltaic storage inverter AC port admittance taking into account the photovoltaic storage hybrid power generation output impedance, and the expression for the storage inverter AC port admittance is: Among them, Y pv is a 2*2 matrix, Λ 1 The small signal of the inverter AC port when the DC bus voltage is constant and current response small signal The transfer coefficient between 2 is the DC bus voltage small signal The current response to the small signal The transfer coefficient, P v is the small voltage signal on the AC side and the small power signal on the DC side The transitive relationship, P i is the small current signal on the AC side and the small power signal on the DC side The transfer relationship, I is the unit 2*2 order unit matrix, F(Z dc ) is the DC side power small signal considering the small signal impedance model of the photovoltaic storage unit To DC voltage small signal The transitive relationship, Y cf It is a 2*2 order diagonal matrix of filter capacitors.

6. The impedance modeling method of the photovoltaic-storage hybrid power generation system according to claim 5, It is characterized in that In the step of integrating the photovoltaic power generation unit equivalent output impedance model, the energy storage unit equivalent output impedance model and the AC / DC side small signal coupling model of the photovoltaic storage inverter control unit to construct the photovoltaic storage hybrid power generation system impedance model, the coefficient Λ 1 ,Λ 2 Calculated by the following formula: Among them, Λ 1 When the DC bus voltage is constant, the small AC voltage signal on the inverter side Its current response is small signal The transfer coefficient between m is the modulation coefficient, V dc is the steady-state value of the DC bus voltage, T PLL (s 1 ) is the phase-locked loop transfer function, H gi (s 1 ) is the current controller transfer function, j is an imaginary unit, K gd is the decoupling coefficient, I g1 is the vector expression of steady-state current, M 1 is the fundamental frequency component represented by the modulated signal, s is the Laplace differential operator, L f is the AC side inductance, I * g1 is the conjugate of the steady-state current vector, M 1 * is the conjugate of the fundamental frequency component represented by the modulated signal, s 2 =j2π(f p -2f 1 ), f p is the disturbance frequency, f 1 is the fundamental frequency; Among them, Λ 2 is the bus voltage small signal Small signal with current response The coefficient is mainly related to the voltage outer loop, current loop and PWM modulation ratio; K m is the modulation coefficient, V dc is the steady-state value of the DC bus voltage, H gi (s 1 ) is the current controller transfer function, H vdc (s 1 ) is the voltage controller transfer function, M g1 is the fundamental frequency component of the modulated signal, L f is the AC side inductance, j is an imaginary unit, K gd is the decoupling coefficient, M * g1 represents the conjugate of the fundamental frequency component of the modulated signal, s = j2πf 1 ,s 2 =j2π(f p -2f 1 ), f p is the disturbance frequency, f 1 is the fundamental frequency.

7. The impedance modeling method of the photovoltaic-storage hybrid power generation system according to claim 5, It is characterized in that In the step of integrating the photovoltaic power generation unit equivalent output impedance model, the energy storage unit equivalent output impedance model and the AC / DC side small signal coupling model of the photovoltaic storage inverter control unit to construct the photovoltaic storage hybrid power generation system impedance model, the coefficient P v and P i Calculated by the following formula: Among them, P V is the small voltage signal on the AC side and the small power signal on the DC side The transitive relationship, I ga is the steady-state value of inverter phase a output, I * ga is the conjugate of the inverter a-phase output steady-state value, P i is the transmission relationship between the AC side current small signal and the DC power small signal, V ga is the inverter modulation voltage steady-state value, V * ga is the conjugate of the inverter modulation voltage steady-state value, s = j2πf p ,s 2 =j2π(f p -2f 1 ), f p is the disturbance frequency, f 1 is the fundamental frequency, L f is the AC side inductance, and T is the matrix transpose.

8. The impedance modeling method of the photovoltaic-storage hybrid power generation system according to claim 5, It is characterized in that In the step of integrating the photovoltaic power generation unit equivalent output impedance model, the energy storage unit equivalent output impedance model and the AC / DC side small signal coupling model of the photovoltaic storage inverter control unit to construct the photovoltaic storage hybrid power generation system impedance model, the coefficient F(Z dc ) is calculated by the following formula: Among them, F(Z dc ) is the DC side power small signal considering the impedance of the photovoltaic storage unit and the DC bus capacitor To the DC side voltage small signal The transitive relationship, F 1 (sC dc ) is the DC bus capacitor impedance at the DC side power small signal To the DC side voltage small signal The transitive relationship, F 2 (Z pv ) is the small power signal of the photovoltaic unit on the DC side To the DC side voltage small signal The transitive relationship, F 3 (Z bat ) is the small power signal of the energy storage unit on the DC side To the DC side voltage small signal The transfer relationship, V dc is the DC bus capacitor steady-state voltage, Z pv is the equivalent output impedance of the photovoltaic power generation unit, Z bat is the equivalent output impedance of the energy storage power generation unit, s 1 =j2π(f p -f 1 ), f p is the disturbance frequency, f 1 is the fundamental frequency, C dc is the DC bus capacitance, I dc is the DC bus steady-state current, V dc is the DC bus steady-state voltage.

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