Converter-free photovoltaic control method applied to wind-light-storage hybrid energy system

Abstract

The invention discloses a converter-free photovoltaic control method applied to a wind-light-storage hybrid energy system, which integrates photovoltaic power generation into a hybrid system by reducing the number of control loops and converters. The designed controller is suitable for a grid-connected system with wind energy and photovoltaic power as main power supplies, BESS as a secondary power supply and FC and an electrolytic cell as three-level power supplies. And through the combination of the pre-compensator and the integrator, the stability of the controller is enhanced, and the steady-state error is eliminated. In the proposed configuration, the GSC maximizes photovoltaic power generation, injects its power into the grid, while sharing the grid load with the RSC. By coordinating the control of the BESS and the fuel cell, the intermittent influence of wind energy and photovoltaic power generation is reduced, and redundant electric energy is used for hydrogen production of the electrolytic cell to support power generation of the fuel cell in adverse weather. And an energy management strategy is provided, so that BESS overcharging is avoided, intermittency and volatility are reduced, and stable power output and service continuity are ensured.

Description

Technical Field

[0001] The present invention relates to the field of new energy grid connection in power systems, and in particular to an inverter-free photovoltaic control method applied to a wind-solar-storage hybrid energy system. Background Art

[0002] In order to meet the demand for electricity, electricity production continues to increase. As environmental problems become increasingly serious, renewable energy sources such as photovoltaic cells, fuel cells, supercapacitors, wind turbines, geothermal energy, etc. are integrated into the existing power generation structure to achieve clean and green energy.

[0003] However, the current research on wind-solar hybrid does not consider the efficiency and optimality of the proposed structure, and only focuses on the control design and the coordination of power sources. In addition, the efficiency of the hybrid energy system has not been optimized. The PV system is connected to the DFIG without an inverter. This configuration has been observed to have large output power fluctuations, and under normal conditions, the DC link voltage has oscillated significantly. Due to the intermittent nature of light and wind energy, the power demand of the system may be limited if the wind speed and solar irradiance are low or high. In addition, the design cannot extract the maximum amount of solar energy, and the potential of the grid side controller (GSC) is not fully utilized. Summary of the invention

[0004] The purpose of the present invention is to provide a photovoltaic control method without inverter applied to a wind-solar-storage hybrid energy system in view of the deficiencies in the prior art.

[0005] According to a first aspect of an embodiment of the present application, there is provided a converter-free photovoltaic control method applied to a wind-solar-storage hybrid energy system, comprising:

[0006] Construct models of photovoltaic cells, doubly-fed wind turbines, energy storage batteries, fuel cells, and electrolyzers in a wind-solar-storage hybrid energy system;

[0007] Based on the constructed model, the output of the rotor-side converter is adjusted using the RSC control strategy, the DC link voltage is adjusted using the GSC control, and the maximum power point tracking is performed using the disturbance observation algorithm to ensure the coordinated operation of the photovoltaic cells and the wind turbine;

[0008] Monitor the output of photovoltaic cells and wind turbines, connect the energy storage battery to the DC link based on the constructed model, and manage the system's excess or insufficient power by coordinating the energy storage battery, fuel cell and electrolyzer. The excess power is used to charge the energy storage battery system and electrolyzer and produce hydrogen. When the power is insufficient, it is supplemented by the fuel cell to maintain system stability.

[0009] Furthermore, in the wind-solar-storage hybrid energy system,

[0010] The model of a photovoltaic cell is shown below:

[0011]

[0012] Where, I is the current of a single solar cell, I PV is the total current generated by light, I o is the reverse leakage current (saturation current), a is the diode factor, R ser is the total series resistance, R per is the total parallel resistance, V t is the thermal voltage, expressed by V t =KTPV / q, K is the Boltzmann constant, T PV is the temperature of the diode in the photovoltaic panel, q is the electron charge, and V is the total terminal voltage of the solar cell;

[0013] The model of the doubly fed wind turbine is as follows:

[0014] The aerodynamic power of a wind turbine is

[0015]

[0016] Among them, P m represents the mechanical power obtained by the wind turbine, v t is the wind speed, C p represents the power coefficient, λ is the speed ratio, ρ is the air density, β represents the blade angle, and A is the area of ​​the rotor blade;

[0017] The equations of the doubly-fed wind turbine rotor and stator are:

[0018]

[0019] Among them, the components of rotor current and terminal voltage are v qr 、v dr 、i qr and i dr ,ω r and ω0 are the rotor and synchronous speeds respectively; where ω=ω0-ω r , the components of the stator flux in the dq coordinate system are and R r represents the resistance of the rotor winding; σ is the leakage flux component;

[0020]

[0021] Among them, L r , L m and L s They represent rotor inductance, mutual inductance and stator inductance respectively;

[0022] The model of the energy storage battery is:

[0023]

[0024] Among them, V Bat ,I Bat , Q d and C bat Respectively represent the voltage, current, stored power and internal capacity of the energy storage battery; E, R b , i1 and E0 represent the electromotive force, internal resistance, internal current and initial electromotive force of the energy storage battery respectively; k is the proportional coefficient of the energy storage battery characteristics, SOC is the state of the energy storage battery, and t is time;

[0025] The fuel cell model is:

[0026]

[0027] Among them, V cell Represents the cell voltage of a single fuel cell, V Nermat Reversible voltage, R incell represents the intrinsic resistance of the fuel cell; in addition, i cell 、i L and i o Respectively represent the battery exchange current and the current when the fuel consumption rate is equal to its maximum supply rate; A cell and B cell Indicates the numerical coefficient, V CF and n CF Indicates the voltage and number of cells in the fuel cell stack;

[0028] The model of the electrolyzer is:

[0029]

[0030] Among them, V Elec ,I Elec and U rev They represent the electromotive force of the electrolytic cell, the current through the electrolytic cell and the reversible voltage of the electrolytic cell respectively, r1 and r2 represent the internal and external resistances of the electrolytic cell, T is the temperature of the diode in the electrolytic cell, k Elec , k T1 , k T2 and k T3 is the overvoltage coefficient of the electrolytic cell, A Elec Represents the area of ​​the electrode unit.

[0031] Furthermore, the output of the rotor-side converter is adjusted using the RSC control strategy, including:

[0032] The dynamic characteristics of the doubly-fed wind turbine rotor current are separated using the following formula:

[0033]

[0034] Among them, the specific expressions of g1 and g2 are as follows:

[0035]

[0036] Among them, V DC represents the DC link voltage, i qr and i dr The transfer function of the current is shown below:

[0037]

[0038] The PI controller is used to control the components of the rotor current. The parameter expressions of the PI controller are as follows:

[0039]

[0040] Active power Q of stator circuit s and reactive power P s The expression is:

[0041]

[0042] Where G1(s) and G2(s) are the transfer functions of the direct-axis and quadrature-axis currents, respectively. dr (s) and I qr (s) are the Laplace transforms of the direct-axis and quadrature-axis currents, s is the Laplace operator, K Ir Indicates the integral gain, K Pr represents the proportional gain of the PI controller, T cr is the time constant of closed-loop current control, v ms is the stator voltage amplitude.

[0043] Furthermore, the DC link voltage is regulated by using the GSC control, including:

[0044] The current components of GSC are decoupled as:

[0045]

[0046] Among them, v qg and v dg is the component of the grid voltage in the dq coordinate system, i qg and i dg are the q-axis and d-axis components of the grid current, L g is the grid-side inductance, R g is the grid side resistance, modulation index m qg and m dg represents the duty cycle of the modulation in the q-axis and d-axis directions. In this case, the stator voltage vector is aligned on the d-axis of the reference frame, so vqs =0, let The transfer function of the system is expressed as:

[0047]

[0048] m qg and m dg The expression is:

[0049]

[0050] A current control loop is used to maintain the voltage balance of GSC. The current control loop is controlled by a PI controller. lig is the integral gain, K pig is the proportional gain, as follows:

[0051]

[0052] Closed loop transfer function G CL It is used to simplify the first-order function as follows:

[0053]

[0054] The power balance between the DC and AC sides of the GSC is maintained by a voltage control loop, which couples the DC link with the PV system, and its expression is as follows:

[0055]

[0056] Among them, P PV is the output power of the photovoltaic system, C DC is the capacitance of the DC circuit, P r is the rotor side power, P BESS is the power of the energy storage battery, where T cig When the value is less than 1 / 10 of the switching frequency, use as a control variable instead of i dg ;make Introducing variable P c The transfer function becomes:

[0057]

[0058] With P c When closely related, it is expressed as:

[0059]

[0060] The method of combining precompensation and integrator is used to improve the stability of PI controller. The PI controller has a cross-gain frequency. The transfer function is:

[0061]

[0062] Among them, α and r are the parameters of the predistorter.

[0063] Furthermore, the energy storage battery is connected to the DC link, and the excess or insufficient power of the system is managed by coordinating the energy storage battery, the fuel cell and the electrolyzer, including the following sub-steps:

[0064] (3.1) Energy storage battery connected to DC link:

[0065] Interfacing the energy storage battery with the DC link using a DC-DC converter:

[0066]

[0067] Among them, i L is the current of BESS, V b is the voltage of BESS, m b is the modulation index;

[0068] Calculate the difference between the PV power, GSC rated power, rotor power and fuel cell power, i.e. the excess power P injected or absorbed by the fuel cell extra , the specific expression is:

[0069] P extra =P PV -P GSC -P r +P FC

[0070] If P extra If the value of is positive, the excess power is absorbed by the energy storage battery; if P extra If the value of is negative, the energy storage battery is required to output power to the DC link;

[0071] (3.2) Power management:

[0072] In charging mode, when the remaining power of the energy storage battery reaches a first threshold, the electrolyzer starts to store excess electricity and produce hydrogen, which is stored in a tank; in discharging mode, when the remaining power of the energy storage battery drops to a second threshold, the fuel cell replenishes the power;

[0073] When the grid load is less than wind and solar energy, the excess electricity is used to charge the energy storage battery until the SOC reaches the upper limit, and the electrolyzer absorbs excess electricity to maintain the operation of the battery; when photovoltaic and wind power generation is insufficient, the energy storage battery provides power for the fuel cell.

[0074] According to a second aspect of an embodiment of the present application, there is provided a converter-free photovoltaic control device applied to a wind-solar-storage hybrid energy system, comprising:

[0075] Modeling module, used to build models of photovoltaic cells, doubly-fed wind turbines, energy storage batteries, fuel cells, and electrolyzers in wind-solar-storage hybrid energy systems;

[0076] The grid-connected control module is used to adjust the output of the rotor-side converter based on the constructed model using the RSC control strategy, adjust the DC link voltage using the GSC control, and perform maximum power point tracking using the disturbance observation algorithm to ensure the coordinated operation of the photovoltaic cells and the wind turbine;

[0077] The energy scheduling module is used to monitor the output status of photovoltaic cells and wind turbines. Based on the constructed model, the energy storage battery is connected to the DC link. By coordinating the energy storage battery, fuel cell and electrolyzer, the system's excess or insufficient power is managed. The excess power is used to charge the energy storage battery system and electrolyzer and produce hydrogen. When the power is insufficient, it is supplemented by the fuel cell to maintain system stability.

[0078] According to a third aspect of an embodiment of the present application, a computer program product is provided, comprising a computer program / instruction, which implements the method described in the first aspect when executed by a processor.

[0079] According to a fourth aspect of an embodiment of the present application, there is provided an electronic device, including:

[0080] one or more processors;

[0081] A memory for storing one or more programs;

[0082] When the one or more programs are executed by the one or more processors, the one or more processors implement the method as described in the first aspect.

[0083] According to a fifth aspect of an embodiment of the present application, a computer-readable storage medium is provided, on which computer instructions are stored, and when the instructions are executed by a processor, the steps of the method described in the first aspect are implemented.

[0084] The technical solution provided by the embodiments of the present application may have the following beneficial effects:

[0085] The present invention provides an efficient and low-cost PV-DFIG-BESS system configuration, simplifies the control loop, and introduces fuel cells and electrolyzers. The AC and DC bus voltage regulation and maximum power point tracking are achieved through the GSC controller, which greatly reduces the GSC power and DC link voltage fluctuations. The new hybrid energy topology optimizes the use of multiple energy sources, improves the power quality of the grid, stabilizes the AC grid voltage and frequency, ensures continuous and stable operation of the system, and provides a more reliable power supply when wind and photovoltaic power generation are limited.

[0086] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0087] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0088] Figure 1 It is a flow chart of a converter-free photovoltaic control method applied to a wind-solar-storage hybrid energy system according to an exemplary embodiment.

[0089] Figure 2 It is a block diagram of an inverter-free photovoltaic control device applied to a wind-solar-storage hybrid energy system according to an exemplary embodiment.

[0090] Figure 3 The diagram is a schematic diagram of an electronic device according to an exemplary embodiment. DETAILED DESCRIPTION

[0091] Here, exemplary embodiments are described in detail, and examples thereof are shown in the accompanying drawings. When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The implementations described in the following exemplary embodiments do not represent all implementations consistent with the present application.

[0092] The terms used in this application are for the purpose of describing specific embodiments only and are not intended to limit this application. The singular forms of "a", "said" and "the" used in this application and the appended claims are also intended to include plural forms unless the context clearly indicates other meanings. It should also be understood that the term "and / or" used herein refers to and includes any or all possible combinations of one or more associated listed items.

[0093] It should be understood that although the terms first, second, third, etc. may be used in the present application to describe various information, these information should not be limited to these terms. These terms are only used to distinguish the same type of information from each other. For example, without departing from the scope of the present application, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Depending on the context, the word "if" as used herein may be interpreted as "at the time of" or "when" or "in response to determining".

[0094] The present invention proposes a converter-free photovoltaic control method applied to a wind-solar-storage hybrid energy system, comprising the following steps:

[0095] Step S1: Construct the model of photovoltaic cells, doubly-fed wind turbine (DFIG), battery energy storage system (BESS), fuel cell (FC), and electrolyzer in the wind-solar-storage hybrid energy system; the specific steps are as follows:

[0096] (1.1) Establish a photovoltaic cell model:

[0097] The mathematical expression for a single solar cell is as follows:

[0098]

[0099] Where, I is the current of a single solar cell, I PV is the total current generated by light, I o is the reverse leakage current (saturation current), a is the diode factor, R ser is the total series resistance, R per is the total parallel resistance, V t is the thermal voltage, which can be expressed by V t =KT PV / q is calculated, K is the Boltzmann constant, T PV is the temperature of the diode in the photovoltaic panel (Kelvin), q is the electron charge, and V is the total terminal voltage of the solar cell.

[0100] (1.2) Build a wind turbine model:

[0101] The aerodynamic power of a wind turbine is expressed by formula (2):

[0102]

[0103] Among them, P m represents the mechanical power obtained by the wind turbine, v t is the wind speed, C p represents the power coefficient, λ is the speed ratio, ρ is the air density, β represents the blade angle, and A is the area of ​​the rotor blade.

[0104] The analysis of DFIG adopts the dq coordinate system, and the d-axis is aligned with the stator magnetic flux space vector, rotating at synchronous speed. The components of the rotor current, the equations of the rotor and the stator can be expressed by formula (3):

[0105]

[0106] Among them, the components of rotor current and terminal voltage in dq coordinate system are v qr 、v dr 、i qr and i dr ω r and ω0 are the rotor speed and synchronous speed respectively (unit: radian / second). Where ω=ω0-ω r The components of the stator flux in the dq coordinate system are and R r represents the resistance of the rotor winding. σ is the leakage flux component, and its mathematical expression is shown in formula (4):

[0107]

[0108] Among them, L r , L m and L s They represent rotor inductance, mutual inductance and stator inductance respectively.

[0109] (1.3) Establish the BESS battery model:

[0110]

[0111] Among them, V Bat ,I Bat , Q d and C bat Respectively represent the voltage, current, stored power (ampere-hour) and internal capacity of BESS; E, R b , i1 and E0 represent the electromotive force, internal resistance, internal current and initial electromotive force of BESS respectively; K is the Boltzmann constant, k is the proportional coefficient of BESS characteristics, SOC is the state of BESS, and t is time.

[0112] (1.4) Establish a fuel cell (FC) model:

[0113] The CF voltage of a single fuel cell can be expressed by the following mathematical expression:

[0114]

[0115] Among them, V cell Represents the cell voltage of a single fuel cell, V NermatReversible voltage, R incell represents the intrinsic resistance of the fuel cell; in addition, i cell 、i L and i o They represent the battery's exchange current (working current) and the current when the fuel consumption rate is equal to its maximum supply rate; A cell and B cell Indicates the numerical coefficient, V CF and n CF Indicates the voltage and number of cells in the fuel cell stack.

[0116] (1.5) Build the electrolytic cell model:

[0117] Water is decomposed into hydrogen and oxygen by the electric current flowing in the electrolyzer, and this process is given by the empirical formula V Elec , I Elec It is expressed as shown in formula (7) and formula (8):

[0118]

[0119] Among them, V Elec ,I Elec and U rev They represent the electromotive force of the electrolytic cell, the current through the electrolytic cell and the reversible voltage of the electrolytic cell, r1 and r2 represent the internal and external resistances of the electrolytic cell, K is the Boltzmann constant, T is the temperature of the diode in the electrolytic cell, and k Elec , k T1 , k T2 and k T3 is the overvoltage coefficient of the electrolytic cell. In addition, A Elec Represents the area of ​​the electrode unit.

[0120] Step 2: Use the RSC control strategy to adjust the output of the rotor-side converter to maintain the stability of active and reactive power and ensure the coordinated operation of wind power generation and the photovoltaic system; use the GSC control to adjust the DC link voltage and use the disturbance observation (P&O) algorithm for maximum power point tracking (MPPT) to ensure the coordinated operation of wind power generation and the photovoltaic system; specifically include the following sub-steps:

[0121] (2.1) RSC control

[0122] The component of the terminal voltage v qr and v dr Controlled by the rotor-side converter (RSC). Using sinusoidal pulses and modulation index m qr and m dr To control the voltage component. Since the variable i qr and i drThe product of makes the rotor current model present nonlinear characteristics. Therefore, in order to solve the rotor terminal voltage, the dynamic characteristics of the DFIG rotor current are separated by the following formula:

[0123]

[0124] Among them, g1 and g2 are two new control parameters, which depend on m qr and md r , the specific expression is as follows:

[0125]

[0126] Among them, V DC Represents the DC link voltage. qr and i dr The transfer function of current G ir (s) can be obtained by formula (11) as follows:

[0127]

[0128] G1(s) and G2(s) are the transfer functions of the direct-axis and quadrature-axis currents, respectively. dr (s) and I qr (s) are the Laplace transforms of the direct-axis and quadrature-axis currents, respectively, and s is the Laplace operator.

[0129] In order to control the components of the rotor current, a proportional-integral (PI) controller is designed, which is implemented based on the zero-pole cancellation method. The zero point of the system transfer function is expressed as Its extreme point is represented by Among them, K Ir Indicates the integral gain, K Pr represents the proportional gain of the PI controller. In order to obtain an appropriate bandwidth, the time constant T of the closed-loop current control cr is set very small, usually kept at 1 / 10 of the switching frequency. Based on these criteria, the parameter expressions of the PI controller are as follows:

[0130]

[0131] Active power Q of stator circuit s and reactive power P s The expression is:

[0132]

[0133] Among them, v ms is the stator voltage amplitude. To avoid high rotor currents and rotor-side converter (RSC) overload, i dr The set value is set to zero.

[0134] (2.2) GSC control

[0135] The purpose of GSC control is to regulate the DC link voltage in the proposed model. The maximum power point tracking (MPPT) of the PV system is also maintained and tracked by the disturbance and observation (P&O) algorithm. First, the current component of the GSC is decoupled as follows:

[0136]

[0137] Among them, v qg and v dg is the component of the grid voltage in the dq coordinate system, i qg and i dg are the q-axis and d-axis components of the grid current, L g is the grid-side inductance, R g is the grid side resistance, modulation index m qg and m dg represents the duty cycle of the modulation in the q-axis and d-axis directions. In this case, the stator voltage vector is aligned on the d-axis of the reference frame, so v qs = 0. Let When , the transfer function of the proposed system can be expressed as:

[0138]

[0139] m qg and m dg The expression is:

[0140]

[0141] A current control loop is used to maintain the voltage balance of GSC. The current control loop is controlled by a PI controller. lig is the integral gain, K pig is the proportional gain, as follows:

[0142]

[0143] Among them, T cig is the time constant of the current control loop. The closed loop transfer function G CL It is used to simplify the first-order function as follows:

[0144]

[0145] A voltage control loop is designed to maintain the power balance between the DC and AC sides of the GSC, in which the DC link is coupled with the PV system. The expression is as follows:

[0146]

[0147] Among them, P PV is the output power of the photovoltaic system, C DC is the capacitance of the DC circuit, P r is the rotor side power, P BESS is the power of the energy storage battery. cig When the value is very small (i.e. less than 1 / 10 of the switching frequency), use as a control variable instead of i dg In addition, let The transfer function becomes:

[0148]

[0149] With P c When closely related, it can be expressed as:

[0150]

[0151] Due to G v The nonlinear characteristics of (S) are not suitable for PI controllers to handle these nonlinear problems. In order to obtain sufficient phase margin and completely eliminate the steady-state error, a method combining a precompensator and an integrator is used. This improves the stability of the controller and provides a stable control at the crossover gain frequency (ω cut ) adds a phase shift Controller in The mathematical expression of the transfer function is:

[0152]

[0153] Among them, α and r are the parameters of the predistorter.

[0154] (2.3) Perturbation and observation method

[0155] The perturbation and observation method is a commonly used method in the maximum power point tracking (MPPT) algorithm. The perturbation and observation method is used to maximize the power generation efficiency of the photovoltaic system and ensure that the photovoltaic system can always operate at the maximum power point when the light conditions are constantly changing. This method is adjusted by periodically perturbing the operating voltage of the photovoltaic system and then observing the power change trend.

[0156] The perturbation and observation method compares the power at the current sampling moment with the power at the previous sampling moment. If the power increases, the algorithm will continue to adjust the voltage in the same direction; if the power decreases, the voltage will be adjusted in the opposite direction. In this way, the perturbation and observation cycle is repeated continuously, and the system eventually approaches the maximum power point.

[0157] Step S3: Monitor the output of photovoltaic and wind turbines, and manage excess and insufficient power by coordinating BESS, fuel cells, and electrolyzers: excess power is used for charging and hydrogen production, and insufficient power is supplemented by fuel cells to maintain system stability; specifically, it includes the following sub-steps:

[0158] (3.1) BESS battery connected to DC link:

[0159] The BESS battery is interfaced with the DC link using a DC-DC converter, and the relevant equation can be expressed by formula (23):

[0160]

[0161] Among them, i L is the current of BESS, V b is the voltage of BESS, m b is the modulation index. By converting the excess power (P extra ) divided by the BESS voltage to generate a battery current reference. The error between the BESS current reference and the BESS inductor current is input into a PI controller to generate a duty cycle signal.

[0162] P extra Equivalent to photovoltaic power generation P PV 、GSC rated power P GSC , rotor power P r and fuel cell power P FC The specific expression is:

[0163] P extra =P PV -P GSC -P r +P FC (twenty four)

[0164] P extra It represents the excess power injected or absorbed by the BESS. When the wind speed and solar radiation are high, P extra The value of is positive, so the BESS absorbs this excess power. However, when the solar radiation or wind speed is low, this power is negative, which means that the power generated by the BESS is negative, that is, energy needs to be injected into the DC link to meet the load demand.

[0165] (3.2) Power management:

[0166] In charging mode, when the remaining power SOC of the BESS reaches a first threshold (such as 80%), the electrolyzer starts to store excess power and produce hydrogen, which is stored in a tank. In discharging mode, when the SOC drops to a second threshold (such as 20%), the fuel cell (FC) replenishes power. In addition, when demand is low or wind power is strong, excess power is used to charge the BESS until the SOC reaches the upper limit. Subsequently, the electrolyzer absorbs excess power to maintain the operation of the battery. When photovoltaic and wind power generation is insufficient, the BESS will provide power to the FC even if demand is high, ensuring that the SOC is maintained at the lower limit.

[0167] The above step S2 is for the grid-connected control of the new energy converter, and the control objects are wind turbines and photovoltaics. The optimal power output point of the wind turbine photovoltaic system is found through RSC, GSC and disturbance observation method, which provides key data for the overall energy management of step S3; step S3 is the regulation of the energy of the hybrid energy, and the control objects are BESS, fuel cells and electrolyzers. The energy distribution in step S3 will be adjusted according to the wind turbine photovoltaic power generation power in step S2. Based on the accurate tracking of the maximum power point in step S2, the energy scheduling in step 3 can optimize the power distribution of the entire system.

[0168] It can be seen from the above embodiments that the present application combines the control strategies of the disturbance observation method (MPPT), the rotor-side converter (RSC) and the grid-side converter (GSC) to achieve efficient coordinated control of photovoltaic power generation, wind power generation, BESS energy storage system and fuel cells. Through the control of RSC, the synchronization of the power generation system and the power grid is ensured, and the power output is optimized; GSC is responsible for the scheduling and management of electric energy while maintaining the stability of the grid frequency. Under unfavorable power generation conditions, the system can still ensure continuous power supply through optimized energy management strategies. The simplified control loop design significantly improves the dynamic response capability of the system, and the integration of the electrolyzer and the fuel cell further improves the energy utilization rate of the system, thereby achieving the desired technical effect of the present application.

[0169] Corresponding to the aforementioned embodiment of the inverter-free photovoltaic control method applied to the wind-solar-storage hybrid energy system, the present application also provides an embodiment of the inverter-free photovoltaic control device applied to the wind-solar-storage hybrid energy system.

[0170] Figure 2 1 is a block diagram of a photovoltaic control device without an inverter applied to a wind-solar-storage hybrid energy system according to an exemplary embodiment. Figure 2 , the device may include:

[0171] Modeling module 21, used to construct models of photovoltaic cells, double-fed wind turbines, energy storage batteries, fuel cells, and electrolyzers in the wind-solar-storage hybrid energy system;

[0172] The grid-connected control module 22 is used to adjust the output of the rotor-side converter using the RSC control strategy based on the constructed model, adjust the DC link voltage using the GSC control, and perform maximum power point tracking using the disturbance observation algorithm to ensure that the photovoltaic cell and the wind turbine work in coordination;

[0173] The energy scheduling module 23 is used to monitor the output status of photovoltaic cells and wind turbines. Based on the constructed model, the energy storage battery is connected to the DC link, and the excess or insufficient power of the system is managed by coordinating the energy storage battery, fuel cell and electrolyzer. The excess power is used to charge the energy storage battery system and electrolyzer and produce hydrogen. When the power is insufficient, it is supplemented by the fuel cell to maintain the stability of the system.

[0174] Regarding the device in the above embodiment, the specific manner in which each module performs operations has been described in detail in the embodiment of the method, and will not be elaborated here.

[0175] For the device embodiment, since it basically corresponds to the method embodiment, the relevant parts can refer to the partial description of the method embodiment. The device embodiment described above is only schematic, wherein the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the present application scheme. A person of ordinary skill in the art can understand and implement it without paying any creative work.

[0176] Accordingly, the present application also provides a computer program product, including a computer program / instruction, which, when executed by a processor, implements the above-mentioned inverter-free photovoltaic control method applied to a wind-solar-storage hybrid energy system.

[0177] Accordingly, the present application also provides an electronic device, comprising: one or more processors; a memory for storing one or more programs; when the one or more programs are executed by the one or more processors, the one or more processors implement the inverter-free photovoltaic control method for the wind-solar-storage hybrid energy system as described above. Figure 3 As shown, it is a hardware structure diagram of a device with data processing capability where a converter-free photovoltaic control device applied to a wind-solar-storage hybrid energy system provided by an embodiment of the present invention is located, except Figure 3 In addition to the processor, memory and network interface shown, any device with data processing capability in which the apparatus in the embodiment is located may also include other hardware, generally based on the actual functions of the device with data processing capability, which will not be described in detail.

[0178] Accordingly, the present application also provides a computer-readable storage medium on which computer instructions are stored, and when the instructions are executed by the processor, the inverter-free photovoltaic control method applied to the wind-solar-storage hybrid energy system as described above is implemented. The computer-readable storage medium can be an internal storage unit of any device with data processing capabilities described in any of the aforementioned embodiments, such as a hard disk or a memory. The computer-readable storage medium can also be an external storage device, such as a plug-in hard disk, a smart memory card (Smart Media Card, SMC), an SD card, a flash card (Flash Card), etc. equipped on the device. Furthermore, the computer-readable storage medium can also include both an internal storage unit and an external storage device of any device with data processing capabilities. The computer-readable storage medium is used to store the computer program and other programs and data required by any device with data processing capabilities, and can also be used to temporarily store data that has been output or is to be output.

[0179] Those skilled in the art will readily appreciate other embodiments of the present application after considering the specification and practicing the contents disclosed herein. The present application is intended to cover any variations, uses or adaptations of the present application, which follow the general principles of the present application and include common knowledge or customary technical means in the art that are not disclosed in the present application.

[0180] It should be understood that the present application is not limited to the exact construction that has been described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof.

Claims

1. A converter-free photovoltaic control method applied to a wind-solar-storage hybrid energy system, characterized in that: The following steps are involved: Construct models of photovoltaic cells, doubly-fed wind turbines, energy storage batteries, fuel cells, and electrolyzers in a wind-solar-storage hybrid energy system; Based on the constructed model, the output of the rotor-side converter is adjusted using the RSC control strategy, the DC link voltage is adjusted using the GSC control, and the maximum power point tracking is performed using the disturbance observation algorithm to ensure the coordinated operation of the photovoltaic cells and the wind turbine; Monitor the output of photovoltaic cells and wind turbines, connect the energy storage battery to the DC link based on the constructed model, and manage the system's excess or insufficient power by coordinating the energy storage battery, fuel cell and electrolyzer. The excess power is used to charge the energy storage battery system and electrolyzer and produce hydrogen. When the power is insufficient, it is supplemented by the fuel cell to maintain system stability.

2. The method according to claim 1, characterized in that: In the wind-solar-storage hybrid energy system, The model of a photovoltaic cell is shown below: Where, I is the current of a single solar cell, I PV is the total current generated by light, I o is the reverse leakage current (saturation current), a is the diode factor, R ser is the total series resistance, R per is the total parallel resistance, V t is the thermal voltage, expressed by V t =KT PV / q is calculated, K is the Boltzmann constant, T PV is the temperature of the diode in the photovoltaic panel, q is the electron charge, and V is the total terminal voltage of the solar cell; The model of the doubly fed wind turbine is as follows: The aerodynamic power of a wind turbine is Among them, P m represents the mechanical power obtained by the wind turbine, v t is the wind speed, C p represents the power coefficient, λ is the speed ratio, ρ is the air density, β represents the blade angle, and A is the area of ​​the rotor blade; The equations of the doubly-fed wind turbine rotor and stator are: Among them, the components of rotor current and terminal voltage are v qr 、v dr 、i qr and i dr ,ω r and ω0 are the rotor and synchronous speeds respectively; where ω=ω0-ω r , the components of the stator flux in the dq coordinate system are and R r represents the resistance of the rotor winding; σ is the leakage flux component; Among them, L r , L m and L s They represent rotor inductance, mutual inductance and stator inductance respectively; The model of the energy storage battery is: Among them, V Bat ,I Bat , Q d and C bat Respectively represent the voltage, current, stored power and internal capacity of the energy storage battery; E, R b , i1 and E0 represent the electromotive force, internal resistance, internal current and initial electromotive force of the energy storage battery respectively; k is the proportional coefficient of the energy storage battery characteristics, SOC is the state of the energy storage battery, and t is time; The fuel cell model is: Among them, V cell Represents the cell voltage of a single fuel cell, V Nermat Reversible voltage, R incell represents the intrinsic resistance of the fuel cell; in addition, i cell 、i L and i o Respectively represent the battery exchange current and the current when the fuel consumption rate is equal to its maximum supply rate; A cell and B cell Indicates the numerical coefficient, V CF and n CF Indicates the voltage and number of cells in the fuel cell stack; The model of the electrolyzer is: Among them, V Elec ,I Elec and U rev They represent the electromotive force of the electrolytic cell, the current through the electrolytic cell and the reversible voltage of the electrolytic cell respectively, r1 and r2 represent the internal and external resistances of the electrolytic cell, T is the temperature of the diode in the electrolytic cell, k Elec , and is the overvoltage coefficient of the electrolytic cell, A Elec Represents the area of ​​the electrode unit.

3. The method according to claim 1, characterized in that The output of the rotor-side converter is adjusted using the RSC control strategy, including: The dynamic characteristics of the doubly-fed wind turbine rotor current are separated using the following formula: Among them, the specific expressions of g1 and g2 are as follows: Among them, V DC represents the DC link voltage, i qr and i dr The current transfer function is obtained by formula (11) as follows: The PI controller is used to control the components of the rotor current. The parameter expressions of the PI controller are as follows: Active power Q of stator circuit s and reactive power P s The expression is: Where G1(s) and G2(s) are the transfer functions of the direct-axis and quadrature-axis currents, respectively. dr (s) and I qr (s) are the Laplace transforms of the direct-axis and quadrature-axis currents, s is the Laplace operator, K Ir Indicates the integral gain, K Pr represents the proportional gain of the PI controller, T cr is the time constant of closed-loop current control, v ms is the stator voltage amplitude.

4. The method according to claim 1, characterized in that Regulate the DC link voltage using GSC control, including: The current component of GSC is decoupled as formula (14): Among them, v qg and v dg is the component of the grid voltage in the dq coordinate system, i qg and i dg are the q-axis and d-axis components of the grid current, L g is the grid-side inductance, R g is the grid side resistance, modulation index m qg and m dg represents the duty cycle of the modulation in the q-axis and d-axis directions. In this case, the stator voltage vector is aligned on the d-axis of the reference frame, so v qs =0, let The transfer function of the system is expressed as: m qg and m dg The expression is: A current control loop is used to maintain the voltage balance of GSC. The current control loop is controlled by a PI controller. lig is the integral gain, K pig is the proportional gain, as follows: Closed loop transfer function G CL It is used to simplify the first-order function as follows: The power balance between the DC and AC sides of the GSC is maintained by a voltage control loop, which couples the DC link with the PV system, and its expression is as follows: Among them, P PV is the output power of the photovoltaic system, C DC is the capacitance of the DC circuit, P r is the rotor side power, P BESS is the power of the energy storage battery, where T cig When the value is less than 1 / 10 of the switching frequency, use as a control variable instead of i dg ;make Introducing variable P c The transfer function becomes: With P c When closely related, it is expressed as: The method of combining precompensation and integrator is used to improve the stability of PI controller. The PI controller has a cross-gain frequency. The transfer function is: Among them, α and r are the parameters of the predistorter.

5. The method according to claim 1, characterized in that Connect the energy storage battery to the DC link and manage the system's excess or insufficient power by coordinating the energy storage battery, fuel cell, and electrolyzer, including the following sub-steps: (3.1) Energy storage battery connected to DC link: The energy storage battery is interfaced with the DC link using a DC-DC converter, which is expressed by formula (23): Among them, i L is the current of BESS, V b is the voltage of BESS, m b is the modulation index; Calculate the difference between the PV power, GSC rated power, rotor power and fuel cell power, i.e. the excess power P injected or absorbed by the fuel cell extra , the specific expression is: P extra =P PV -P GSC -P r +P FC (24) If P extra If the value of is positive, the excess power is absorbed by the energy storage battery; if P extra If the value of is negative, the energy storage battery is required to output power to the DC link; (3.2) Power management: In charging mode, when the remaining power of the energy storage battery reaches a first threshold, the electrolyzer starts to store excess electricity and produce hydrogen, which is stored in a tank; in discharging mode, when the remaining power of the energy storage battery drops to a second threshold, the fuel cell replenishes the power; When the grid load is less than wind and solar energy, the excess electricity is used to charge the energy storage battery until the SOC reaches the upper limit, and the electrolyzer absorbs excess electricity to maintain the operation of the battery; when photovoltaic and wind power generation is insufficient, the energy storage battery provides power for the fuel cell.

6. A converter-free photovoltaic control device applied to a wind-solar-storage hybrid energy system, characterized in that: include: Modeling module, used to build models of photovoltaic cells, doubly-fed wind turbines, energy storage batteries, fuel cells, and electrolyzers in wind-solar-storage hybrid energy systems; The grid-connected control module is used to adjust the output of the rotor-side converter based on the constructed model using the RSC control strategy, adjust the DC link voltage using the GSC control, and perform maximum power point tracking using the disturbance observation algorithm to ensure the coordinated operation of the photovoltaic cells and the wind turbine; The energy scheduling module is used to monitor the output status of photovoltaic cells and wind turbines. Based on the constructed model, the energy storage battery is connected to the DC link. By coordinating the energy storage battery, fuel cell and electrolyzer, the system's excess or insufficient power is managed. The excess power is used to charge the energy storage battery system and electrolyzer and produce hydrogen. When the power is insufficient, it is supplemented by the fuel cell to maintain system stability.

7. A computer program product comprising a computer program / instructions, characterized in that When the computer program / instructions are executed by a processor, the method according to any one of claims 1 to 5 is implemented.

8. An electronic device, characterized in that: include: one or more processors; A memory for storing one or more programs; When the one or more programs are executed by the one or more processors, the one or more processors implement the method according to any one of claims 1 to 5.

9. A computer-readable storage medium having computer instructions stored thereon, characterized in that: When the instruction is executed by a processor, the steps of the method according to any one of claims 1 to 5 are implemented.

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