Grid-connected control method and system for energy storage converter and medium

Abstract

The invention discloses a grid-connected control method and system for an energy storage converter and a medium, and belongs to the technical field of converter control, and the method comprises the steps: obtaining three-phase voltage and three-phase current, building an instantaneous power model of active power and reactive power, and constructing a power loop UDE model; designing a first filter to obtain an estimated value of first lumped interference and a control law of a UDE control power loop; establishing a current loop UDE model of a grid-connected working mode of the energy storage converter based on a grid-side inductance voltage equation of the energy storage converter, and designing a second filter to obtain an estimated value of second lumped interference and a control law of a UDE control current loop; and inputting the active power instruction and the reactive power instruction into a control law of a UDE control power loop, and carrying out modulation to obtain a switch tube control signal, thereby solving the problems of out-of-limit frequency fluctuation and poor electric energy quality caused by uncertainty of load power change in the prior art.

Description

TECHNICAL FIELD

[0001] The application relates to a grid-connected control method and system of a power conversion system and a medium, and belongs to the technical field of converter control. BACKGROUND

[0002] In recent years, domestic and foreign scholars have extensively and deeply researched power storage technology, and a power conversion system (PCS) as a core device for realizing bidirectional power flow between a power storage system and a power grid has developed very rapidly in the field of electric power industry. The performance of the power conversion system determines whether the power storage system can stably, efficiently and reliably operate, so the key step of researching and developing an efficient and reliable power conversion system is indispensable in the development of power storage technology. At present, the power conversion system is increasingly developed towards high frequency, miniaturization and low loss and high efficiency, and a traditional two-level power conversion system cannot meet the design requirements of high power due to the limitation of the topology itself. The three-level power conversion system has a lower harmonic content generated by inversion at a high switching frequency due to the superiority of the topology itself, which is beneficial to saving the design cost of a filter. Therefore, the three-level PCS has extremely important research value and very wide application prospect.

[0003] With the development of distributed power supply, more and more applications are to provide energy for local loads. In the grid-connected control mode of the power conversion system, a PI regulator is usually used to control the outer power loop and the inner current loop, so as to realize the stable grid-connected operation of the power conversion system. Since the power conversion system is a controlled system with multiple variables and strong coupling, although the PI regulator is widely used due to its simple structure and high reliability, the decoupling ability of the traditional PI control is limited, and the power conversion system is often disturbed by various internal parameter changes and external power grid working condition changes in the actual grid-connected operation process. For example, in the case of sudden change of power instruction or sudden change of power grid voltage and frequency, the control effect of the traditional PI controller will be poor. Therefore, the control strategy needs to be further improved. SUMMARY

[0004] The application aims to provide a grid-connected control method, system and medium of a power conversion system, replace the PI controller in the control loop with an uncertain disturbance estimation controller, estimate the lumped disturbance, and solve the problem of frequency fluctuation out of limit and poor power quality caused by the uncertainty of load power change in the prior art, and effectively control the degree of deterioration of the control effect caused by the uncertainty of load power change.

[0005] To solve the above technical problems, the application is implemented by using the following technical scheme.

[0006] In a first aspect, the present application provides a method for grid-connected control of energy storage converter based on an uncertainty and disturbance estimator (UDE), comprising:

[0007] obtaining three-phase voltage and three-phase current of the power grid;

[0008] establishing instantaneous power models of active power and reactive power respectively based on the three-phase voltage and the three-phase current, and constructing a power loop UDE model;

[0009] calculating an estimated value of first lumped disturbance based on the power loop UDE model using a first filter;

[0010] obtaining a control law of the UDE control power loop based on the estimated value of the first lumped disturbance;

[0011] establishing a current loop UDE model of the grid-connected working mode of the energy storage converter based on an equation of grid-side inductance voltage of the energy storage converter;

[0012] calculating an estimated value of second lumped disturbance based on the current loop UDE model using a second filter;

[0013] obtaining a control law of the UDE control current loop based on the estimated value of the second lumped disturbance;

[0014] inputting the active power command and the reactive power command into the control law of the UDE control power loop to obtain a given value of the current loop;

[0015] inputting the given value of the current loop into the control law of the UDE control current loop to obtain a switch control signal.

[0016] Further, the method for establishing the instantaneous power models of active power and reactive power respectively based on the three-phase voltage and the three-phase current comprises:

[0017] obtaining axis voltage and current and axis voltage and current through coordinate transformation of the three-phase voltage and the three-phase current;

[0018] calculating actual instantaneous active power and actual instantaneous reactive power of the power grid according to axis voltage and current and axis voltage and current;

[0019] filtering the actual instantaneous active power and the actual instantaneous reactive power of the power grid through a low-pass filter to obtain an active power value and a reactive power value;

[0020] establishing the instantaneous power models of active power and reactive power respectively based on the active power value and the reactive power value;

[0021] wherein the calculation formulae of the actual instantaneous active power and the actual instantaneous reactive power are respectively represented as:

[0022] ;

[0023] wherein, represents the actual instantaneous active power, represents the actual instantaneous reactive power, , respectively represents the d-axis voltage and the d-axis current, , respectively represents the d-axis voltage and the d-axis current;

[0024] wherein the calculation formulae of the active power value and the reactive power value are respectively represented as:

[0025] ;

[0026] wherein, , respectively represents the active power value and the reactive power value, represents the bandwidth of the low-pass filter, represents the inverse Laplace transform operator, represents the complex frequency.

[0027] Further, the power loop UDE model is used to calculate the estimated value of the first lumped disturbance by using a first filter, comprising:

[0028] a first expected model is preset as a reference model of the power loop UDE model;

[0029] based on the power loop UDE model, a first control input and a first error equation in the active power and the reactive power are obtained by referring to the reference model of the power loop UDE model, a mathematical expression of the first lumped disturbance is derived according to the first error equation, and the estimated value of the first lumped disturbance is calculated by using the first filter;

[0030] the power loop UDE model is represented as:

[0031] ;

[0032] wherein, represents the power loop UDE model at the current moment , and represents the derivative of the power loop control state variable at the current moment , wherein, , represents the current moment The first control input, , Indicates the current time of shaft current, Indicates the current time of shaft current, Indicates the current time The first episode's total interference, among which, ;

[0033] The first expected model is represented as:

[0034]

[0035] In the formula, Indicates the current time The first expectation model is for the current time. The state variables of the first expected model The derivative, and These represent the first control coefficient matrix and the second control coefficient matrix, respectively. , , , Let these represent the active power constant coefficient and reactive power constant coefficient of the first expected model, respectively. For the current moment The reference input for the first expected model;

[0036] The first control input and the first error equation are respectively expressed as:

[0037] ;

[0038] ;

[0039] In the formula, Indicates the current time The first error model is for the current time. Power loop system error The derivative, .

[0040] Furthermore, the control laws of the UDE control power loop include UDE control laws for active power and UDE control laws for reactive power, wherein the UDE control laws for active power and reactive power are respectively expressed as follows:

[0041] ;

[0042] ;

[0043] In the formula, UDE control law representing active power, UDE control law representing reactive power. , , and They represent , , and The complex frequency domain form obtained after Laplace transform , These represent the bandwidth of the first active power filter and the bandwidth of the first reactive power filter, respectively.

[0044] Furthermore, the grid-side inductor voltage equation of the energy storage converter is expressed as:

[0045] ;

[0046] In the formula, , They represent the current time. of The voltage across the shaft's capacitor and The voltage across the shaft's capacitor. Indicates the resistance value of the grid-side inductor. Indicates the grid-side inductance value. Indicates the angular frequency of the power grid. Indicates the current time of Instantaneous change in shaft current Indicates the current time of Instantaneous change in shaft current Indicates the current time The instantaneous change in time.

[0047] Furthermore, the estimation of the second lumped interference calculated using the second filter based on the current loop UDE model includes:

[0048] A second expected model is preset as the reference model for the current loop UDE model;

[0049] Referring to the reference model of the current loop UDE model, based on the current loop UDE model, the second control input and the second error equation in the active current and reactive current are obtained. The mathematical expression of the second lumped disturbance is derived according to the second error equation. The estimated value of the second lumped disturbance is calculated by using the second filter.

[0050] The current loop UDE model is represented as follows:

[0051] ;

[0052] In the formula, Indicates the current time The current loop UDE model is for the current time. Current loop control state variables The derivative, , Indicates the current time The second control input, , Indicates the current time The second episode's total interference, , , They represent the current time. of shaft voltage and shaft current, , They represent the current time. of shaft voltage and shaft current, , They represent shaft and The change in the axis;

[0053] The second expectation model is expressed as:

[0054]

[0055] In the formula, Indicates the current time The second expectation model is for the current time. The state variables of the second expected model The derivative, , Let these represent the first and second constant coefficient matrices of the second expectation model, respectively. , , Represents the constant coefficients of the second expectation model. Indicates the current time The reference input for the second expectation model, Represents the identity matrix;

[0056] The second control input and the second error equation are respectively expressed as:

[0057] ;

[0058] ;

[0059] In the formula, Indicates the current time The second error model is for the current time. Current loop system error The derivative, .

[0060] Furthermore, it also includes using a second filter to estimate the unknown variables and external disturbances in the second control input to obtain approximate values ​​of the estimated value of the second lumped disturbance and the second control input; wherein, the approximate value of the estimated value of the second lumped disturbance is expressed as:

[0061] ;

[0062] In the formula, For the current moment The second episode of total interference The approximate value of the estimated value, For the current moment The second filter;

[0063] The approximate value of the second control input is expressed as:

[0064] ;

[0065] In the formula, Indicates the current time The approximate value of the second control input.

[0066] Furthermore, the control law of the UDE control current loop is expressed as follows:

[0067] ;

[0068] In the formula, Indicates capacitor voltage The complex frequency domain form, , They represent the current time. Current loop control state variables Current moment The reference input of the second expectation model The complex frequency domain form obtained after the Laplace transform, Indicates the resistance value of the grid-side inductor. The complex frequency domain form, This indicates the bandwidth of the selected second filter. Indicates the resistance value of the grid-side inductor. The complex frequency domain form.

[0069] Secondly, the present invention provides a grid-connected control system for an energy storage converter, comprising:

[0070] The data acquisition module is used to acquire the three-phase voltage and three-phase current of the power grid;

[0071] The power loop UDE model construction module is used to establish instantaneous power models of active power and reactive power based on the three-phase voltage and the three-phase current, and to construct the power loop UDE model.

[0072] The first estimation calculation module is used to calculate the estimated value of the first lumped interference based on the power loop UDE model and using the first filter.

[0073] The control law acquisition module for the UDE control power loop is used to obtain the control law of the UDE control power loop based on the estimated value of the first lumped disturbance.

[0074] The current loop UDE model construction module is used to establish the current loop UDE model of the energy storage converter in grid-connected operation mode based on the grid-side inductor voltage equation of the energy storage converter.

[0075] The second estimation calculation module is used to calculate the estimated value of the second lumped disturbance based on the current loop UDE model and using the second filter.

[0076] The control law acquisition module for the UDE control current loop is used to obtain the control law of the UDE control current loop based on the estimated value of the second lumped disturbance.

[0077] The current loop setpoint acquisition module is used to input the active power command and reactive power command into the control law of the UDE control power loop to obtain the current loop setpoint.

[0078] The switching transistor control signal acquisition module is used to modulate the control law of the current loop, which is input into the current loop setpoint, to obtain the switching transistor control signal.

[0079] Thirdly, the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the grid-connected control method for energy storage converters as described in the first aspect.

[0080] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0081] This invention constructs a dual-closed-loop uncertain disturbance estimation and control architecture with power and current loops. It utilizes a first / second filter to perform cascaded estimation and compensation of lumped disturbances, achieving precise suppression of uncertain disturbances such as grid-side voltage fluctuations and load disturbances. This significantly improves the dynamic tracking accuracy of active / reactive power and grid-side current during the grid connection of the energy storage converter, as well as the system robustness, ensuring stable operation of the grid connection interface under complex conditions. It solves the problems of frequency fluctuation exceeding limits and power quality deterioration caused by the uncertainty of load power changes in distributed power sources with high renewable energy penetration rates. This accelerates system stabilization, improves the grid-connected current quality of the energy storage converter, and effectively controls the degree of control performance degradation caused by the uncertainty of load power changes. Attached Figure Description

[0082] Figure 1 This is a schematic flowchart of a grid-connected control method for an energy storage converter provided in an embodiment of the present invention;

[0083] Figure 2 This is a schematic diagram of the three-level circuit principle of the three-phase PWM inverter to be controlled provided in the embodiment of the present invention;

[0084] Figure 3 This is a schematic diagram of the control law structure of the UDE-controlled active power loop provided in an embodiment of the present invention;

[0085] Figure 4 This is a schematic diagram of the control law structure of the UDE-controlled reactive power loop provided in an embodiment of the present invention;

[0086] Figure 5 This is a schematic diagram of the control law structure of the UDE control current loop provided in an embodiment of the present invention;

[0087] Figure 6 This is the embodiment of the present invention. Figure 1 The diagram shown is a simulation schematic of a step disturbance of the active power reference value of an energy storage converter using a grid-connected control method based on an uncertain disturbance estimator.

[0088] Figure 7 This is the embodiment of the present invention. Figure 1 The diagram shown is a simulation of a step disturbance in the reactive power reference value of an energy storage converter using a grid-connected control method based on an uncertain disturbance estimator.

[0089] Figure 8 This is the embodiment of the present invention. Figure 1 The diagram shows a simulated current harmonic spectrum of an energy storage converter operating in steady state using a grid-connected control method based on an uncertain disturbance estimator.

[0090] Figure 9 This is the embodiment of the present invention.Figure 1 The diagram shows an experimental waveform of an energy storage converter absorbing active power under no-load sudden change using a grid-connected control method based on an uncertain disturbance estimator.

[0091] Figure 10 This is the embodiment of the present invention. Figure 1 The diagram shows an experimental waveform of an energy storage converter that absorbs reactive power and then releases reactive power using a grid-connected control method based on an uncertain disturbance estimator.

[0092] Figure 11 This is the embodiment of the present invention. Figure 1 The diagram shows an experimental waveform of a storage converter operating in steady state using a grid-connected control method based on an uncertain disturbance estimator. Detailed Implementation

[0093] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the embodiments of the present invention and the specific features in the embodiments are detailed descriptions of the technical solution of the present invention, rather than limitations thereof. In the absence of conflict, the embodiments of the present invention and the technical features in the embodiments can be combined with each other.

[0094] Example 1

[0095] like Figure 1 As shown in the figure, this embodiment introduces a grid-connected control method for an energy storage converter, including:

[0096] Step 1: Obtain the three-phase voltage and three-phase current of the power grid.

[0097] This invention acquires three-phase voltage and current signals in real time synchronously using high-precision sensors, and converts them into digital quantities via an ADC module. This step provides the original state variables for subsequent power calculations and model building, ensuring the real-time performance and accuracy of the control system, and is the foundation for system state perception.

[0098] Step 2: Based on the three-phase voltage and the three-phase current, establish instantaneous power models for active power and reactive power respectively, and construct a power loop UDE model.

[0099] This invention converts three-phase voltage and current into active / reactive components in the dq rotating coordinate system using instantaneous power theory, constructs a power loop state-space model with lumped disturbances, and introduces a disturbance observer structure into the power loop UDE model to incorporate lumped disturbances such as system uncertainties and external disturbances into the model, providing a mathematical basis for subsequent disturbance estimation and compensation.

[0100] Step 3: Based on the power loop UDE model, the first filter is used to calculate the estimated value of the first lumped interference.

[0101] This invention derives the relationship between the power loop control input and the error equation using UDE theory, determines the expression for lumped interference, designs a low-pass filter to perform frequency domain shaping on the error signal, and realizes real-time estimation of lumped interference, providing a basis for interference compensation in control law design.

[0102] Step 4: Obtain the control law for the UDE control power loop based on the estimated value of the first lumped disturbance.

[0103] This invention incorporates disturbance estimates into the control law design and employs a feedforward compensation strategy to counteract the effects of lumped disturbances. The control law combines PID feedback with disturbance compensation terms to achieve accurate tracking of active and reactive power, thereby improving the system's disturbance rejection capability and dynamic response speed.

[0104] Step 5: Based on the grid-side inductor voltage equation of the energy storage converter, establish the current loop UDE model of the energy storage converter in grid-connected operation mode.

[0105] This invention derives a dynamic model of the current loop from the converter grid-side inductor voltage equation, considering nonlinear factors such as inductor parasitic parameters and switching ripple, and constructs a current loop state equation containing lumped disturbances. The UDE model of the current loop decouples the current tracking error from the disturbance term, providing a precise mathematical description for current loop control.

[0106] Step 6: Based on the current loop UDE model, the second filter is used to calculate the estimated value of the second lumped interference.

[0107] This invention derives the mapping relationship between control input and error using a current loop UDE model and employs an adaptive filtering algorithm to estimate lumped interference in real time. The filter design balances bandwidth and stability, ensuring both speed and accuracy in interference estimation.

[0108] Step 7: Obtain the control law for the UDE control current loop based on the estimated value of the second lumped disturbance.

[0109] This invention incorporates the current loop disturbance estimate into the control law, employing a strategy combining sliding mode control and disturbance compensation. The control law achieves rapid and accurate tracking of current commands while suppressing current distortion caused by nonlinear factors such as inductor saturation and switching dead zones, thereby improving grid-connected current quality.

[0110] Step 8: Input the active power command and reactive power command into the control law of the UDE control power loop to obtain the current loop setpoint.

[0111] This invention converts upper-level power commands into current-loop reference values ​​using a power loop control law, achieving decoupled power-current control. This step completes the command transmission from the power layer to the current layer, ensuring that power commands are accurately implemented through the current loop and meeting grid-connected power factor regulation requirements.

[0112] Step 9: Input the current loop setpoint into the UDE control current loop control law to obtain the switching transistor control signal.

[0113] This invention generates a modulation wave signal through a current loop control law, which in turn generates a switching transistor control signal, realizing the mapping from current command to switching action, driving the converter switching transistor to work, and ultimately achieving precise control of grid-connected power and optimization of power quality.

[0114] Example 2

[0115] Based on the same inventive concept as Embodiment 1, this embodiment introduces the implementation steps of a grid-connected control method for an energy storage converter, including:

[0116] Step 1: Obtain the three-phase voltage and three-phase current of the power grid.

[0117] Step 2: Based on the three-phase voltage and the three-phase current, establish instantaneous power models for active power and reactive power respectively, and construct a power loop UDE model.

[0118] The schematic diagram of the three-level circuit of the three-phase PWM inverter to be controlled in this embodiment is shown below. Figure 2 As shown, a three-level topology with diode clamping is used. - It consists of 12 insulated-gate bipolar transistors (IGBTs) with anti-parallel diodes. - It consists of 6 clamping diodes. , These are the converter-side filter inductors and their internal resistances. , These are the grid-side filter inductors and their internal resistances, respectively. For AC side filter capacitor, It is a damping resistor. , , These are the phase voltages of the three-phase power grid, sampled using voltage sensors. , , These are the three-phase grid-connected currents, sampled using current sensors. , , These are the fundamental frequencies of the output voltage at the midpoint of the three-phase bridge arms, respectively. , , These are the AC voltages of the three-phase filter capacitors. This is the output current of the DC voltage source. The voltage is either the DC voltage source voltage or the energy storage battery voltage; the value is sampled using a voltage sensor. , These are the upper and lower split capacitors on the DC side, respectively.

[0119] In this embodiment, instantaneous power models for active power and reactive power are established based on the three-phase voltage and the three-phase current, respectively, including:

[0120] The three-phase voltage and three-phase current are obtained through coordinate transformation. shaft voltage and current and Shaft voltage and current;

[0121] according to shaft voltage and current and Calculate the actual instantaneous active power and actual instantaneous reactive power of the power grid using axis voltage and current;

[0122] In this embodiment, the calculation formulas for the actual instantaneous active power and the actual instantaneous reactive power are expressed as follows:

[0123] ;

[0124] In the formula, Indicates the actual instantaneous active power. Indicates the actual instantaneous reactive power. , They represent shaft voltage and shaft current, , They represent shaft voltage and shaft current;

[0125] The actual instantaneous active power and actual instantaneous reactive power of the power grid are filtered by a low-pass filter to obtain the active power value and reactive power value. In this embodiment, instantaneous power models of active power and reactive power are established based on the active power value and reactive power value, respectively.

[0126] like Figure 3 and Figure 4 The diagrams shown illustrate the control law structures for the active power loop and reactive power loop of the UDE control system, respectively, including the differential feedforward of the reference model, the PI regulator, and the model inverse of the controlled system. After calculating the active / reactive power based on the sampled grid voltage and current, the actual active / reactive power values ​​are obtained after filtering by a low-pass filter.

[0127] Therefore, in this embodiment, the calculation formulas for the active power and reactive power output of the energy storage converter to the grid are expressed as follows:

[0128] ;

[0129] In the formula, , These represent the active power value and the reactive power value, respectively. This indicates the bandwidth of the low-pass filter. This represents the inverse Laplace transform operator. Represents a complex frequency.

[0130] Step 3: Based on the power loop UDE model, the first filter is used to calculate the estimated value of the first lumped interference.

[0131] In this embodiment, the step of calculating the estimated value of the first lumped interference using the first filter based on the power loop UDE model includes:

[0132] The first expected model is preset as the reference model for the power loop UDE model;

[0133] Referring to the reference model of the power loop UDE model, the first control input and the first error equation in the active power and reactive power are obtained based on the power loop UDE model. The mathematical expression of the first lumped disturbance is derived based on the first error equation, and the estimated value of the first lumped disturbance is calculated using the first filter.

[0134] In this embodiment, the power loop UDE model is represented as:

[0135] ;

[0136] In the formula, Indicates the current time The power loop UDE model for the current time. Power loop control state variables The derivative of, where, , Indicates the current time The first control input, , Indicates the current time of shaft current, Indicates the current time of shaft current, Indicates the current time The first episode's total interference, among which, ;

[0137] In this embodiment, the first desired model is represented as:

[0138]

[0139] In the formula, Indicates the current time The first expectation model is for the current time. The state variables of the first expected model The derivative, and These represent the first control coefficient matrix and the second control coefficient matrix, respectively. , , , Let these represent the active power constant coefficient and reactive power constant coefficient of the first expected model, respectively. For the current moment The reference input for the first expected model.

[0140] In this embodiment, the first control input and the first error equation are respectively expressed as:

[0141] ;

[0142] ;

[0143] In the formula, Indicates the current time The first error model is for the current time. Power loop system error The derivative, .

[0144] This embodiment uses a first filter to suppress the first lumped interference. An approximate estimate is made to obtain the estimated value of the first lumped interference; the first filter is a first-order low-pass filter.

[0145] Step 4: Obtain the control law for the UDE control power loop based on the estimated value of the first lumped disturbance.

[0146] In this embodiment, the control law of the UDE control power loop includes a UDE control law for active power and a UDE control law for reactive power, wherein the UDE control law for active power and the UDE control law for reactive power are respectively expressed as:

[0147] ;

[0148] ;

[0149] In the formula, UDE control law representing active power, UDE control law representing reactive power. , , and They represent , , and The complex frequency domain form obtained after Laplace transform , These represent the bandwidth of the first active power filter and the bandwidth of the first reactive power filter, respectively.

[0150] Step 5: Based on the grid-side inductor voltage equation of the energy storage converter, establish the current loop UDE model of the energy storage converter in grid-connected operation mode.

[0151] like Figure 5 The diagram shows the control law structure of the UDE control current loop, including the differential feedforward of the reference model, the PI controller, and the model inverse of the controlled system. The filtered state differential feedforward accelerates the error convergence process and improves the dynamic response speed of the current loop; the PI controller can track state variables without steady-state error; and the model inverse can cancel out the known dynamic processes of the controlled system.

[0152] In this embodiment, considering the grid-side inductor resistance, the grid-side inductor voltage equation of the energy storage converter is expressed as:

[0153] ;

[0154] In the formula, , They represent the current time. of The voltage across the shaft's capacitor and The voltage across the shaft's capacitor. Indicates the resistance value of the grid-side inductor. Indicates the grid-side inductance value. Indicates the angular frequency of the power grid. Indicates the current time of Instantaneous change in shaft current Indicates the current time of Instantaneous change in shaft current Indicates the current time The instantaneous change in time.

[0155] In this embodiment, the step of calculating the estimated value of the second lumped interference using the second filter based on the current loop UDE model includes:

[0156] A second expected model is preset as the reference model for the current loop UDE model;

[0157] Referring to the reference model of the current loop UDE model, the second control input and the second error equation in the active current and reactive current are obtained based on the current loop UDE model. The mathematical expression of the second lumped disturbance is derived based on the second error equation, and the estimated value of the second lumped disturbance is calculated using the second filter.

[0158] In this embodiment, the current loop UDE model is represented as:

[0159] ;

[0160] In the formula, Indicates the current time The current loop UDE model is for the current time. Current loop control state variables The derivative, , Indicates the current time The second control input, , Indicates the current time The second episode's total interference, , , They represent the current time. of shaft voltage and shaft current, , They represent the current time. of shaft voltage and shaft current, , They represent shaft and The amount of change in the axis.

[0161] Step 6: Based on the current loop UDE model, the second filter is used to calculate the estimated value of the second lumped interference.

[0162] In this embodiment, the second desired model is represented as:

[0163]

[0164] In the formula, Indicates the current time The second expectation model is for the current time. The state variables of the second expected model The derivative, , Let these represent the first and second constant coefficient matrices of the second expectation model, respectively. , , Represents the constant coefficients of the second expectation model. Indicates the current time The reference input for the second expectation model, Represents the identity matrix.

[0165] In this embodiment, the second control input and the second error equation are respectively expressed as:

[0166] ;

[0167] ;

[0168] In the formula, Indicates the current time The second error model is for the current time. Current loop system error The derivative, .

[0169] In this embodiment, the unknown variables and external disturbances in the second control input are estimated using a second filter to obtain approximate values ​​of the estimated value of the second lumped disturbance and the second control input; wherein, the approximate value of the estimated value of the second lumped disturbance is expressed as:

[0170] ;

[0171] In the formula, For the current moment The second episode of total interference The approximate value of the estimated value, For the current moment The second filter.

[0172] In this embodiment, the approximate value of the second control input is expressed as:

[0173] ;

[0174] In the formula, Indicates the current time The approximate value of the second control input.

[0175] Step 7: Obtain the control law of the UDE control current loop based on the estimated value of the second lumped disturbance.

[0176] In this embodiment, the control law of the UDE control current loop is expressed as:

[0177] ;

[0178] In the formula, Indicates capacitor voltage The complex frequency domain form, , They represent the current time. Current loop control state variables Current moment The reference input of the second expectation model The complex frequency domain form obtained after the Laplace transform, Indicates the resistance value of the grid-side inductor. The complex frequency domain form, This indicates the bandwidth of the selected second filter. Indicates the resistance value of the grid-side inductor. The complex frequency domain form.

[0179] In the UDE controller, the parameters of the PI regulator are only related to the desired system bandwidth αc and the filter bandwidth βc, which greatly simplifies the parameter tuning of the PI controller.

[0180] Step 8: Input the active power command and reactive power command into the control law of the UDE control power loop to obtain the current loop setpoint.

[0181] Step 9: Input the current loop setpoint into the UDE control current loop control law to obtain the switching transistor control signal.

[0182] This embodiment uses SPWM modulation to convert the virtual back EMF. The input PWM modulation loop intersects with the triangular carrier wave to obtain a high-frequency PWM pulse, which is then used for secondary frequency modulation control of the switching transistor.

[0183] from Figure 6 The simulation diagram of the active power reference value step disturbance of the energy storage converter shows that at startup, i.e., at t=0, the active power command P* is 100kW; at t=0.1, the active power command is subjected to a step disturbance, P* changes from 100kW to -100kW, and the energy storage converter changes from discharging to charging. The curves of the active power P in response to the step disturbance of the active power command value by the PI controller and the UDE controller are shown below. Figure 7 As shown, under active power command disturbances, the response time of PI control is approximately 0.02 s, while the response time of UDE control is approximately 0.01 s. Compared to PI control, UDE control has a faster response speed when there is no overshoot and no steady-state error.

[0184] from Figure 7The simulation diagram of the step disturbance of the reactive power reference value of the energy storage converter shows that at startup, i.e. at t=0, the reactive power reference value Q* is -100kVar; at t=0.1, the step disturbance is applied, Q* changes from -100kVar to 100kVar, and the phase of the grid-connected current changes from lagging to leading.

[0185] The reactive power Q curves of the PI controller and UDE controller in response to the step disturbance of the reactive power reference value are as follows: Figure 7 As shown, under reactive power command disturbances, the response time of PI control is approximately 0.1s; the response time of UDE control is approximately 0.01s, with no steady-state error. Therefore, compared to PI control, UDE control has a faster response speed without overshoot or steady-state error. Figure 8 This is a schematic diagram of the simulated current harmonic spectrum for steady-state operation of the energy storage converter, where the total harmonic distortion rate of the current is 1.76%. Therefore, with effective improvements in dynamic performance and anti-interference performance, the steady-state performance of the UDE controller is comparable to that of the PI controller.

[0186] Figure 9 This is a schematic diagram of the experimental waveform for a sudden change in active power absorption under no-load conditions in an energy storage converter. In the experiment, a step disturbance of the active power setpoint P* was applied to the active power loop of the energy storage converter. With a sudden application of a 10kW active power setpoint command, the response time of the UDE controller was approximately 100ms. Compared to PI control, the response time of UDE control was reduced by 60%.

[0187] Figure 10 The diagram illustrates the experimental waveform of an energy storage converter abruptly switching from absorbing reactive power to releasing reactive power. Specifically, it shows the experimental waveform of the energy storage converter switching from no-load to absorbing 100kVar reactive power. As can be seen from the diagram, under the disturbance of reactive power command, the response time of the UDE controller is approximately 120ms, which is about 56.36% less than that of PI control.

[0188] Figure 11 The diagram illustrates the experimental waveforms for steady-state operation of the energy storage converter, specifically the waveforms of absorbing 100kVar reactive power and then releasing 100kVar reactive power. Under reactive power command disturbances, the response time of the UDE controller is approximately 170ms, which is about 58.02% less than that of PI control.

[0189] This embodiment features a simplified structure and intuitively adjustable parameters. The final experimental results collectively verify the effectiveness of the method provided by this invention under power interference conditions, demonstrating that the response speed of the PCS using a UDE controller is improved by 50% compared to a PCS using a PI controller. In situations such as nonlinear loads, photovoltaic inverter clusters, or concentrated charging piles, abnormal changes such as grid voltage distortion, rises, or drops may occur. Using a UDE controller can better ensure the normal operation of the PCS and improve device performance.

[0190] Example 3

[0191] Based on the same inventive concept as other embodiments, this embodiment introduces a grid-connected control system for an energy storage converter, including:

[0192] The data acquisition module is used to acquire the three-phase voltage and three-phase current of the power grid;

[0193] The power loop UDE model construction module is used to establish instantaneous power models of active power and reactive power based on the three-phase voltage and the three-phase current, and to construct the power loop UDE model.

[0194] The first estimation calculation module is used to calculate the estimated value of the first lumped interference based on the power loop UDE model and using the first filter.

[0195] The control law acquisition module for the UDE control power loop is used to obtain the control law of the UDE control power loop based on the estimated value of the first lumped disturbance.

[0196] The current loop UDE model construction module is used to establish the current loop UDE model of the energy storage converter in grid-connected operation mode based on the grid-side inductor voltage equation of the energy storage converter.

[0197] The second estimation calculation module is used to calculate the estimated value of the second lumped disturbance based on the current loop UDE model and using the second filter.

[0198] The control law acquisition module for the UDE control current loop is used to obtain the control law of the UDE control current loop based on the estimated value of the second lumped disturbance.

[0199] The current loop setpoint acquisition module is used to input the active power command and reactive power command into the control law of the UDE control power loop to obtain the current loop setpoint.

[0200] The switching transistor control signal acquisition module is used to modulate the control law of the current loop, which is input into the current loop setpoint, to obtain the switching transistor control signal.

[0201] The specific functions of each module described above are explained in the relevant content of Embodiment 1 or Embodiment 2, and will not be repeated here.

[0202] Example 4

[0203] Based on the same inventive concept as other embodiments, this embodiment describes a computer-readable storage medium having computer instructions stored thereon, which, when executed by a processor, implement the steps of the methods of Embodiment 1 or 2 described above.

[0204] In summary, this invention constructs a dual-closed-loop uncertain disturbance estimation and control architecture with power and current loops. By utilizing a first / second filter to perform cascaded estimation and compensation of lumped disturbances, it achieves precise suppression of uncertain disturbances such as grid-side voltage fluctuations and load disturbances. This significantly improves the dynamic tracking accuracy of active / reactive power and grid-side current during the grid connection of the energy storage converter, as well as the system robustness, ensuring stable operation of the grid connection interface under complex conditions. It solves the problems of frequency fluctuation exceeding limits and power quality deterioration caused by the uncertainty of load power changes in distributed power sources under high renewable energy penetration rates. This accelerates system stabilization, improves the grid-connected current quality of the energy storage converter, and effectively controls the degree of control performance degradation caused by the uncertainty of load power changes.

[0205] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0206] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0207] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a processFigure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0208] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0209] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A grid-connected control method for an energy storage converter, characterized in that, include: Obtain the three-phase voltage and three-phase current of the power grid; Instantaneous power models for active power and reactive power are established based on the three-phase voltage and the three-phase current, respectively, and a power loop UDE model is constructed. Based on the power loop UDE model, the estimated value of the first lumped interference is calculated using the first filter; The control law for the UDE control power loop is obtained based on the estimated value of the first total disturbance. Based on the grid-side inductor voltage equation of the energy storage converter, a current loop UDE model of the energy storage converter in grid-connected operation mode is established. Based on the current loop UDE model, the second filter is used to calculate the estimated value of the second lumped interference; The control law for the UDE control current loop is obtained based on the estimated value of the total disturbance in the second set. The active power command and reactive power command are input into the control law of the UDE control power loop to obtain the current loop setpoint; The current loop setpoint is input into the UDE to control the current loop control law, which is then modulated to obtain the switching transistor control signal.

2. The grid-connected control method for energy storage converters according to claim 1, characterized in that, Instantaneous power models for active and reactive power are established based on the three-phase voltages and three-phase currents, respectively, including: The three-phase voltage and three-phase current are obtained through coordinate transformation. shaft voltage and current and Shaft voltage and current; according to shaft voltage and current and Calculate the actual instantaneous active power and actual instantaneous reactive power of the power grid using axis voltage and current; The actual instantaneous active power and actual instantaneous reactive power of the power grid are filtered through a low-pass filter to obtain the active power value and reactive power value; Instantaneous power models for active power and reactive power are established based on active power and reactive power values, respectively. The calculation formulas for the actual instantaneous active power and the actual instantaneous reactive power are expressed as follows: ； In the formula, Indicates the actual instantaneous active power. This represents the actual instantaneous reactive power. , They represent shaft voltage and shaft current, , They represent shaft voltage and shaft current; The calculation formulas for the active power value and the reactive power value are expressed as follows: ； In the formula, , These represent the active power value and the reactive power value, respectively. This indicates the bandwidth of the low-pass filter. This represents the inverse Laplace transform operator. Represents a complex frequency.

3. The grid-connected control method for energy storage converters according to claim 1, characterized in that, The estimation of the first lumped interference calculated using the first filter based on the power loop UDE model includes: The first expected model is preset as the reference model for the power loop UDE model; Referring to the reference model of the power loop UDE model, the first control input and the first error equation in the active power and reactive power are obtained based on the power loop UDE model. The mathematical expression of the first lumped disturbance is derived according to the first error equation. The estimated value of the first lumped disturbance is calculated using the first filter. The power loop UDE model is represented as follows: ； In the formula, Indicates the current time The power loop UDE model for the current time. Power loop control state variables The derivative of, where, , This indicates the bandwidth of the low-pass filter. Indicates the current time The first control input, express shaft voltage, , Indicates the current time of shaft current, Indicates the current time of shaft current, Indicates the current time The first episode's total interference, among which, , express shaft current, , They represent shaft voltage and shaft current; The first expected model is represented as: ； In the formula, Indicates the current time The first expectation model is for the current time. The state variables of the first expected model The derivative, and These represent the first control coefficient matrix and the second control coefficient matrix, respectively. , , , Let represent the active power constant coefficient and reactive power constant coefficient of the first expected model, respectively. For the current moment The reference input for the first expected model; The first control input and the first error equation are respectively expressed as: ； ； In the formula, Indicates the current time The first error model is for the current time. Power loop system error The derivative, .

4. The grid-connected control method for energy storage converters according to claim 3, characterized in that, The control laws of the UDE control power loop include UDE control laws for active power and UDE control laws for reactive power, wherein the UDE control laws for active power and reactive power are respectively expressed as follows: ； ； In the formula, UDE control law representing active power, UDE control law representing reactive power. , , and They represent , , and The complex frequency domain form obtained after Laplace transform , These represent the bandwidth of the first active power filter and the bandwidth of the first reactive power filter, respectively.

5. The grid-connected control method for energy storage converters according to claim 4, characterized in that, The grid-side inductor voltage equation of the energy storage converter is expressed as follows: ； In the formula, , They represent the current time. of The voltage across the shaft's capacitor and The voltage across the shaft's capacitor. Indicates the resistance value of the grid-side inductor. Indicates the grid-side inductance value. Indicates the angular frequency of the power grid. Indicates the current time of Instantaneous change in shaft current Indicates the current time of Instantaneous change in shaft current Indicates the current time The instantaneous change in time.

6. The grid-connected control method for energy storage converters according to claim 1, characterized in that, The estimation of the second lumped interference, calculated using the second filter based on the current loop UDE model, includes: A second expected model is preset as the reference model for the current loop UDE model; Referring to the reference model of the current loop UDE model, based on the current loop UDE model, the second control input and the second error equation in the active current and reactive current are obtained. The mathematical expression of the second lumped disturbance is derived according to the second error equation. The estimated value of the second lumped disturbance is calculated by using the second filter. The current loop UDE model is represented as follows: ； In the formula, Indicates the current time The current loop UDE model, Indicates the resistance value of the grid-side inductor. This indicates the grid-side inductance value at the current moment. Current loop control state variables The derivative, , Indicates the current time The second control input, , , They represent the current time. of The voltage across the shaft's capacitor and The voltage across the shaft's capacitor. Indicates the current time The second episode's total interference, , , They represent the current time. of shaft voltage and shaft current, , They represent the current time. of shaft voltage and shaft current, , They represent shaft and The change in the axis; The second expectation model is expressed as: In the formula, Indicates the current time The second expectation model is for the current time. The state variables of the second expected model The derivative, , Let these represent the first and second constant coefficient matrices of the second expectation model, respectively. , , Represents the constant coefficients of the second expectation model. Indicates the current time The reference input for the second expectation model, Represents the identity matrix; The second control input and the second error equation are respectively expressed as: ； ； In the formula, Indicates the current time The second error model is for the current time. Current loop system error The derivative, .

7. The grid-connected control method for an energy storage converter according to claim 6, characterized in that, It also includes using a second filter to estimate the unknown variables and external disturbances in the second control input to obtain an approximate value of the estimated value of the second lumped disturbance and an approximate value of the second control input; The approximate value of the estimated value of the second lumped interference is expressed as: ； In the formula, For the current moment The second episode of total interference The approximate value of the estimated value, For the current moment The second filter; The approximate value of the second control input is expressed as: ； In the formula, Indicates the current time The approximate value of the second control input.

8. The grid-connected control method for an energy storage converter according to claim 6, characterized in that, The control law of the UDE control current loop is expressed as follows: ； In the formula, Indicates capacitor voltage The complex frequency domain form, , They represent the current time. Current loop control state variables Current moment The reference input of the second expectation model The complex frequency domain form obtained after the Laplace transform, Indicates the resistance value of the grid-side inductor. The complex frequency domain form, This indicates the bandwidth of the selected second filter. Indicates the resistance value of the grid-side inductor. The complex frequency domain form.

9. A grid-connected control system for an energy storage converter, characterized in that, include: The data acquisition module is used to acquire the three-phase voltage and three-phase current of the power grid; The power loop UDE model construction module is used to establish instantaneous power models of active power and reactive power based on the three-phase voltage and the three-phase current, and to construct the power loop UDE model. The first estimation calculation module is used to calculate the estimated value of the first lumped interference based on the power loop UDE model and using the first filter. The control law acquisition module for the UDE control power loop is used to obtain the control law of the UDE control power loop based on the estimated value of the first lumped disturbance. The current loop UDE model construction module is used to establish the current loop UDE model of the energy storage converter in grid-connected operation mode based on the grid-side inductor voltage equation of the energy storage converter. The second estimation calculation module is used to calculate the estimated value of the second lumped disturbance based on the current loop UDE model and using the second filter. The control law acquisition module for the UDE control current loop is used to obtain the control law of the UDE control current loop based on the estimated value of the second lumped disturbance. The current loop setpoint acquisition module is used to input the active power command and reactive power command into the control law of the UDE control power loop to obtain the current loop setpoint. The switching transistor control signal acquisition module is used to modulate the control law of the current loop, which is input into the current loop setpoint, to obtain the switching transistor control signal.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the grid-connected control method for the energy storage converter as described in any one of claims 1-8.

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