Energy storage converter switch control method and device based on virtual impedance, terminal equipment and storage medium

Abstract

The invention discloses an energy storage converter switch control method and device based on virtual impedance, terminal equipment and a storage medium. The method comprises the following steps: acquiring an electrical angular velocity of a synchronous generator, a synchronous rotation angular velocity of a power grid, virtual input mechanical power, an active power reference value, a capacitor voltage reference value, a reactive power reference value, output electromagnetic power, an energy storage converter reactive power, a rated voltage amplitude, a capacitor voltage, virtual inductance and virtual resistance; an energy storage converter outer ring control model is constructed according to the parameters; then obtaining the output voltage of the energy storage converter in each switching state, and sampling the output current; and finally, according to the outer loop control model of the energy storage converter, the output voltage and the sampling output current, determining a target switching state of the energy storage converter. According to the invention, the whole control process is simpler and more convenient than a linear control method based on PI control.

Description

Technical Field

[0001] The present invention relates to the technical field of energy storage converter control, and in particular, to a switching control method, device, terminal device and storage medium of an energy storage converter based on virtual impedance. Background Art

[0002] In recent years, a large number of power electronic devices and distributed energy sources have been connected to the power grid, resulting in a decline in the inertia support ability of the power grid, which cannot provide voltage support and frequency support for loads. Therefore, it is necessary for an energy storage converter device with grid-forming ability to simulate the external characteristics of a synchronous generator, provide inertia support, and improve the characteristics of low inertia and weak damping of the power grid.

[0003] Traditional converters adopt a linear control method based on PI control, which has the advantages of simplicity and easy implementation. However, the model decoupling is complex, and the PI controller requires tuning complex PI parameters during design, increasing the complexity of the converter control structure and the difficulty of control parameter design, which is not conducive to simplifying control and improving calculation efficiency. Summary of the Invention

[0004] The present invention provides a switching control method, device, terminal device and storage medium of an energy storage converter based on virtual impedance, which can make the whole control process simpler than the linear control method based on PI control.

[0005] An embodiment of the present invention provides a switching control method of an energy storage converter based on virtual impedance, including:

[0006] Obtaining the electrical angular velocity of a synchronous generator, the synchronous rotating angular velocity of the power grid, the virtual input mechanical power, the reference value of active power, the reference value of capacitor voltage, the reference value of reactive power, the output electromagnetic power, the reactive power of the energy storage converter, the rated voltage amplitude, the capacitor voltage, the virtual inductor and the virtual resistor;

[0007] Constructing an active power - frequency loop equation of the energy storage converter according to the electrical angular velocity of the synchronous generator, the synchronous rotating angular velocity of the power grid, the input virtual mechanical power, the reference value of active power and the output electromagnetic power;

[0008] Constructing a reactive power - voltage loop equation of the energy storage converter according to the reactive power of the energy storage converter, the reference value of capacitor voltage, the reference value of reactive power and the rated voltage amplitude;

[0009] Constructing a virtual reference current equation of the energy storage converter according to the reference value of capacitor voltage, the capacitor voltage, the virtual inductor and the virtual resistor;

[0010] Constructing an outer - loop control model of the energy storage converter according to the active power - frequency loop equation, the virtual reference current equation and the reactive power - voltage loop equation;

[0011] Obtain the output voltage of the above energy storage converter under each switch state, and obtain the sampled output current at a preset time step;

[0012] According to the above outer-loop control model, output voltage, and sampled output current of the energy storage converter, calculate the target switch state of the above energy storage converter, and control the above energy storage converter according to the above target switch state.

[0013] Further, the obtaining of the sampled output current at a preset time step includes:

[0014] Obtain the output current of the above energy storage converter in the current signal sampling period;

[0015] Starting from the output current in the current signal sampling period, sequentially obtain a preset number of historical output currents before the current signal sampling period at the above preset time step;

[0016] Based on the output current in the current signal sampling period and the above historical output currents, obtain the above sampled output current.

[0017] Further, the calculating of the target switch state of the above energy storage converter according to the above outer-loop control model, output voltage, and sampled output current includes:

[0018] Calculate the virtual reference current according to the above outer-loop control model of the energy storage converter;

[0019] Calculate the slope of the sampled output current according to the above sampled output current and the above preset time step;

[0020] Calculate the predicted output current components of each switch state of the above energy storage converter in the stationary coordinate system at the next sampling period according to the above slope, the above output voltage, and the above sampled output current;

[0021] Determine the target switch state of the above energy storage converter according to the above predicted output current components and the above virtual reference current.

[0022] Further, the calculating of the predicted output current components of each switch state of the above energy storage converter in the stationary coordinate system at the next sampling period according to the above slope, the above output voltage, and the above sampled output current includes:

[0023] Obtain the sampling duration of the above signal sampling period;

[0024] Calculate the first perturbation component on the α-axis of the above stationary coordinate system and the second perturbation component on the β-axis of the above stationary coordinate system according to the above output voltage and the above slope;

[0025] Based on the above output voltage, first disturbance component, second disturbance component, sampled output current, and the above sampling duration, calculate the above predicted output current component.

[0026] Further, calculating the first disturbance component on the α-axis of the above stationary coordinate system and the second disturbance component on the β-axis of the above stationary coordinate system based on the above output voltage and the above slope includes:

[0027] Based on the above output voltage, calculate the first output voltage component of the above output voltage on the α-axis of the above stationary coordinate system and the second output voltage component on the β-axis of the above stationary coordinate system;

[0028] Based on the above slope, calculate the first slope component of the above slope on the α-axis of the above stationary coordinate system and the second slope component on the β-axis of the above stationary coordinate system;

[0029] Based on the above first output voltage component and first slope component, calculate the first disturbance component on the α-axis of the above stationary coordinate system;

[0030] Based on the above second output voltage component and second slope component, calculate the second disturbance component on the β-axis of the above stationary coordinate system.

[0031] Further, calculating the above predicted output current component based on the above output voltage, first disturbance component, second disturbance component, sampled output current, and the above sampling duration includes:

[0032] Based on the above first disturbance component, first output voltage component, sampling duration, and first output current component, calculate the first predicted output current component on the α-axis of the above stationary coordinate system;

[0033] Based on the above second disturbance component, second output voltage component, sampling duration, and second output current component, calculate the second predicted output current component on the β-axis of the above stationary coordinate system.

[0034] Further, determining the target switching state of the above energy storage converter based on the above predicted output current component and the above virtual reference current includes:

[0035] Based on the above virtual reference current, obtain the first virtual reference current component of the above virtual reference current on the α-axis of the above stationary coordinate system and the second virtual reference current component on the β-axis;

[0036] Calculate the first absolute value of the difference between the above first virtual reference current component and the first predicted output current;

[0037] Calculate a second absolute value of the difference between the second virtual reference current component and the second predicted output current;

[0038] Use the sum of the first absolute value and the second absolute value as the value function value of the energy storage converter, and then obtain the value function values of the energy storage converter in various switching states; wherein, each value function value corresponds to a switching state;

[0039] Use the switching state corresponding to the minimum value function value as the target switching state.

[0040] Based on the method embodiment above, the present invention correspondingly provides an apparatus embodiment;

[0041] The present invention provides an energy storage converter switching control device based on virtual impedance, including:

[0042] A first data acquisition module, a frequency loop equation construction module, a voltage loop equation construction module, a virtual reference current equation construction module, a control model construction module, a second data acquisition module, and an energy storage converter control module;

[0043] The first data acquisition module is configured to acquire the electrical angular velocity of the synchronous generator, the synchronous rotating angular velocity of the power grid, the virtual input mechanical power, the active power reference value, the capacitor voltage reference value, the reactive power reference value, the output electromagnetic power, the reactive power of the energy storage converter, the rated voltage amplitude, the capacitor voltage, the virtual inductor, and the virtual resistor;

[0044] The frequency loop equation construction module is configured to construct an active power - frequency loop equation of the energy storage converter according to the electrical angular velocity of the synchronous generator, the synchronous rotating angular velocity of the power grid, the input virtual mechanical power, the active power reference value, and the output electromagnetic power;

[0045] The voltage loop equation construction module is configured to construct a reactive power - voltage loop equation of the energy storage converter according to the reactive power of the energy storage converter, the capacitor voltage reference value, the reactive power reference value, and the rated voltage amplitude;

[0046] The virtual reference current equation construction module is configured to construct a virtual reference current equation of the energy storage converter according to the capacitor voltage reference value, the capacitor voltage, the virtual inductor, and the virtual resistor;

[0047] The control model construction module is configured to construct an outer - loop control model of the energy storage converter according to the active power - frequency loop equation, the virtual reference current equation, and the reactive power - voltage loop equation;

[0048] The second data acquisition module is configured to acquire the output voltage of the energy storage converter in each switch state and acquire the sampled output current at a preset time step.

[0049] The energy storage converter control module is configured to calculate the target switch state of the energy storage converter according to the outer loop control model of the energy storage converter, the output voltage, and the sampled output current, and control the energy storage converter according to the target switch state.

[0050] Based on the above method embodiment, the present invention correspondingly provides a terminal device embodiment.

[0051] The present invention provides a terminal device, including a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor. When the processor executes the computer program, it implements a method for controlling the switch of an energy storage converter based on virtual impedance according to any embodiment of the present invention.

[0052] Based on the above method embodiment, the present invention correspondingly provides a storage medium embodiment.

[0053] The present invention provides a storage medium, including a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor. When the processor executes the computer program, it implements a method for controlling the switch of an energy storage converter based on virtual impedance according to any embodiment of the present invention.

[0054] The embodiments of the present invention have the following beneficial effects:

[0055] The present invention provides a switching control method for an energy storage converter based on virtual impedance. The method includes: first, obtaining the electrical angular velocity of a synchronous generator, the synchronous rotational angular velocity of a power grid, a virtual input mechanical power, a reference active power value, a reference capacitor voltage value, a reference reactive power value, an output electromagnetic power, the reactive power of the energy storage converter, a rated voltage amplitude, a capacitor voltage, a virtual inductor, and a virtual resistor; then, constructing an active power - frequency loop equation of the energy storage converter according to the electrical angular velocity of the synchronous generator, the synchronous rotational angular velocity of the power grid, the input virtual mechanical power, the reference active power value, and the output electromagnetic power; then, constructing a reactive power - voltage loop equation of the energy storage converter according to the reactive power of the energy storage converter, the reference capacitor voltage value, the reference reactive power value, and the rated voltage amplitude; then, constructing a virtual reference current equation of the energy storage converter according to the reference capacitor voltage value, the capacitor voltage, the virtual inductor, and the virtual resistor; then, constructing an outer - loop control model of the energy storage converter according to the active power - frequency loop equation, the virtual reference current equation, and the reactive power - voltage loop equation; then, obtaining the output voltage of the energy storage converter in each switching state and acquiring a sampled output current at a preset time step; finally, calculating a target switching state of the energy storage converter according to the outer - loop control model of the energy storage converter, the output voltage, and the sampled output current, and controlling the energy storage converter according to the target switching state. Therefore, the present invention directly constructs the active power - frequency loop equation, the virtual reference current equation, and the reactive power - voltage loop equation of the energy storage converter based on relevant electrical parameters, and then obtains the outer - loop control model of the energy storage converter. Finally, the target switching state of the energy storage converter is determined according to the outer - loop control model of the energy storage converter to perform switching control on the energy storage converter. That is, the present invention does not require a PI controller and can directly construct an outer - loop control model of the energy storage converter for determining the target switching state based on relevant electrical parameters. Therefore, it is not necessary to calculate the relevant gain parameters of the PI controller, avoiding the complex calculation process brought about by calculating the gain parameters and making the entire control process simpler. Description of the Drawings

[0056] Figure 1 FIG. is a schematic flowchart of a switching control method for an energy storage converter based on virtual impedance provided by an embodiment of the invention.

[0057] Figure 2 FIG. is a topology diagram of an energy storage converter provided by an embodiment of the present invention.

[0058] Figure 3 FIG. is a control diagram of an energy storage converter provided by an embodiment of the present invention.

[0059] Figure 4 FIG. is a structural diagram of a switching control device for an energy storage converter based on virtual impedance provided by an embodiment of the present invention. Detailed implementation manners

[0060] Next, the technical solutions in the present invention will be clearly and completely described in conjunction with the accompanying drawings in the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention without creative efforts shall fall within the protection scope of the present invention.

[0061] As Figure 1 shown, a method for controlling the switch of an energy storage converter based on virtual impedance provided by an embodiment of the present invention includes:

[0062] Step S101: Obtain the electrical angular velocity of the synchronous generator, the synchronous rotational angular velocity of the power grid, the virtual input mechanical power, the active power reference value, the capacitor voltage reference value, the reactive power reference value, the output electromagnetic power, the reactive power of the energy storage converter, the rated voltage amplitude, the capacitor voltage, the virtual inductor, and the virtual resistor;

[0063] Schematically, the topology diagram of the energy storage converter is as Figure 2 shown, and the system is obtained by sequentially connecting an energy storage converter, a filter inductor L, a filter capacitor C, a line impedance R, and a power grid.

[0064] Step S102: Construct an active power-frequency loop equation of the energy storage converter according to the electrical angular velocity of the synchronous generator, the synchronous rotational angular velocity of the power grid, the input virtual mechanical power, the active power reference value, and the output electromagnetic power;

[0065] Specifically, the constructed active power-frequency loop equation is shown as follows:

[0066]

[0067] In the formula, P m represents the input virtual mechanical power, and P m includes an active power command and the output of a virtual governor. P e represents the output electromagnetic power, D represents the damping coefficient, ω represents the electrical angular velocity of the synchronous generator, ω 0 represents the synchronous rotational angular velocity of the power grid, J represents the inertia coefficient, t represents time, m represents the active-frequency droop coefficient, and P ref represents the active power reference value.

[0068] Step S103: Construct a reactive power-voltage loop equation of the energy storage converter according to the reactive power of the energy storage converter, the capacitor voltage reference value, the reactive power reference value, and the rated voltage amplitude;

[0069] Specifically, the constructed reactive power-voltage loop equation is as follows:

[0070] U ref = U 0 + n(Q ref - Q e )

[0071] In the formula, U ref represents the reference value of the capacitor voltage, U 0 represents the rated voltage amplitude, which is also the grid connection point voltage amplitude, n represents the reactive power-voltage droop coefficient, Q ref represents the reference value of the reactive power, and Q e represents the reactive power of the energy storage converter, that is, the reactive power output by the energy storage converter.

[0072] Step S104: Construct the virtual reference current equation of the energy storage converter according to the above reference value of the capacitor voltage, capacitor voltage, virtual inductor, and virtual resistor;

[0073] Specifically, the constructed virtual reference current equation is as follows:

[0074]

[0075] In the formula, i ref represents the virtual reference current, L v represents the virtual inductor, R v represents the virtual resistor, U ref represents the reference value of the capacitor voltage, U c represents the capacitor voltage, and s represents the complex domain variable.

[0076] Step S105: Construct the outer loop control model of the energy storage converter according to the above active power-frequency loop equation, virtual reference current equation, and reactive power-voltage loop equation;

[0077] Schematically, the control diagram of the energy storage converter is as shown in Figure 3 . Figure 3 Part a in it is the schematic diagram of the control strategy of the energy storage converter, Figure 3 Part b in it is the schematic diagram of the control strategy of the energy storage converter with virtual impedance introduced, Figure 3 Part c in it is the schematic diagram of the model-free parameter inductor current predictive control strategy. The above outer loop control model of the energy storage converter is composed of part a and part b in Figure 3 . This outer loop control model of the energy storage converter is a control of the energy storage converter with virtual impedance introduced.

[0078] Step S106: Obtain the output voltage of the above energy storage converter in each switching state, and obtain the sampled output current at a preset time step;

[0079] Specifically, the energy storage converter consists of three bridge arms, and each bridge arm has two switch states, namely "open" and "closed". Therefore, the entire energy storage converter has a total of 8 switch states, and each switch state corresponds to an output voltage.

[0080] In a preferred embodiment, the obtaining of the sampled output current according to the preset time step includes:

[0081] Obtain the output current of the above energy storage converter in the current signal sampling period;

[0082] Starting from the output current in the current signal sampling period, sequentially obtain a preset number of historical output currents before the current signal sampling period according to the above preset time step;

[0083] According to the output current in the current signal sampling period and the above historical output currents, obtain the above sampled output current.

[0084] Schematically, if the output current in the current signal sampling period k is represented by i(k), the preset time step is represented by h, and the preset number is set to 3, then the above historical output currents are sequentially: i(k - h), i(k - 2h), and i(k - 3h).

[0085] In this preferred embodiment, starting from the current signal sampling period, a preset number of historical output currents are obtained according to the preset time step, and together with the output current in the current signal sampling period, they form the sampled output current.

[0086] Step S107: Calculate the target switch state of the above energy storage converter according to the above energy storage converter outer loop control model, output voltage, and sampled output current, and control the above energy storage converter according to the above target switch state.

[0087] In a preferred embodiment, the calculating of the target switch state of the above energy storage converter according to the above energy storage converter outer loop control model, output voltage, and sampled output current includes:

[0088] Calculate the virtual reference current according to the above energy storage converter outer loop control model;

[0089] Calculate the slope of the sampled output current according to the above sampled output current and the above preset time step;

[0090] Calculate the predicted output current components of each switch state of the above energy storage converter in the stationary coordinate system at the next sampling period according to the above slope, the above output voltage, and the above sampled output current;

[0091] Determine the target switching state of the energy storage converter according to the predicted output current component and the virtual reference current as described above.

[0092] Schematically, as Figure 3 shown, from Figure 3 part a in the figure, that is, the output of the energy storage converter control strategy is calculated through the energy storage converter control strategy introducing virtual impedance shown in part b of the figure to obtain the virtual reference current. Subsequently, the components of the virtual reference current on the α-axis and β-axis in the stationary coordinate system are respectively used as the reference values of the output current of the energy storage converter corresponding to the next signal sampling period and Then in Figure 3 figure c, together with the obtained predicted output current component, determine the final switching vector (i.e., the target switching state).

[0093] In this preferred embodiment, the target switching state for controlling the energy storage converter is finally determined through the calculated virtual reference current and predicted output current component.

[0094] In another preferred embodiment, according to the slope, the output voltage, and the sampled output current as described above, when calculating the next sampling period, the predicted output current components of each switching state of the energy storage converter in the stationary coordinate system include:

[0095] Obtain the sampling duration of the signal sampling period;

[0096] According to the output voltage and the slope, calculate the first perturbation component on the α-axis in the stationary coordinate system and the second perturbation component on the β-axis in the stationary coordinate system;

[0097] According to the output voltage, the first perturbation component, the second perturbation component, the sampled output current, and the sampling duration, calculate the predicted output current component.

[0098] Specifically, first calculate the first perturbation component and the second perturbation component according to the output voltage and the slope, and then calculate the predicted output current component according to the output voltage, the first perturbation component, the second perturbation component, the sampled output current, and the sampling duration.

[0099] In this preferred embodiment, the predicted output current components of each switching state of the energy storage converter are calculated through the slope, the output voltage, the sampled output current, and the sampling duration of the signal sampling period.

[0100] In another preferred embodiment, the calculation of the first perturbation component on the α-axis in the stationary coordinate system and the second perturbation component on the β-axis in the stationary coordinate system according to the output voltage and the slope as described above includes:

[0101] Based on the above output voltage, calculate the first output voltage component on the α-axis of the above stationary coordinate system and the second output voltage component on the β-axis of the above stationary coordinate system for the above output voltage;

[0102] Based on the above slope, calculate the first slope component on the α-axis of the above stationary coordinate system and the second slope component on the β-axis of the above stationary coordinate system for the above slope;

[0103] Based on the above first output voltage component and the first slope component, calculate the first perturbation component on the α-axis of the above stationary coordinate system;

[0104] Based on the above second output voltage component and the second slope component, calculate the second perturbation component on the β-axis of the above stationary coordinate system.

[0105] Specifically, the general mathematical model of the energy storage converter in the two-phase stationary coordinate system is shown as the following formula:

[0106]

[0107] In the formula, L is the inductance, i α is the output current component of the energy storage converter on the α-axis of the stationary coordinate system, i β is the output current component of the energy storage converter on the β-axis of the stationary coordinate system, U α is the capacitor voltage component output by the energy storage converter on the α-axis of the stationary coordinate system, U β is the capacitor voltage component output by the energy storage converter on the β-axis of the stationary coordinate system, E α is the component of the grid voltage on the α-axis of the stationary coordinate system, E β is the component of the grid voltage on the β-axis of the stationary coordinate system, and R is the resistance.

[0108] Specifically, the formula obtained by discretizing the general mathematical model of the above energy storage converter in the two-phase stationary coordinate system is shown as the following formula:

[0109]

[0110] In the formula, i α (k + 1) represents the predicted current component on the α-axis of the stationary coordinate system at the (k + 1)-th signal sampling period, i β (k + 1) represents the predicted current component on the β-axis of the stationary coordinate system at the (k + 1)-th signal sampling period, T represents the sampling duration of the signal sampling period, U α (k) represents the output voltage component on the α-axis of the stationary coordinate system at the k-th signal sampling period, U β(k) represents the output voltage component on the β-axis of the stationary coordinate system at the k-th signal sampling period, E α (k) represents the grid voltage component on the α-axis of the stationary coordinate system at the k-th signal sampling period, E β (k) represents the grid voltage component on the β-axis of the stationary coordinate system at the k-th signal sampling period, i α (k) represents the output current component on the α-axis of the stationary coordinate system at the k-th signal sampling period, i β (k) represents the output current component on the β-axis of the stationary coordinate system at the k-th signal sampling period.

[0111] Therefore, based on the above general mathematical model of the energy storage converter in the two-phase stationary coordinate system and the equations obtained after the above discretization, when inductance or resistance disturbances occur, the following formulas can be obtained:

[0112]

[0113] In the formula, ΔL represents the inductance disturbance amount, and ΔR represents the resistance disturbance amount.

[0114] Subsequently, the super-local model of the general system can be obtained:

[0115]

[0116] And the general energy storage converter model:

[0117]

[0118] In the formula, λ α represents the voltage scaling factor of the system on the α-axis of the stationary coordinate system, λ β represents the voltage scaling factor of the system on the β-axis of the stationary coordinate system, F α represents the first disturbance component on the α-axis of the stationary coordinate system, F β represents the second disturbance component on the β-axis of the stationary coordinate system.

[0119] Specifically, using the fourth-order four-segment Runge-Kutta to represent the differential terms on the left side of the above energy storage converter model, the following equations are obtained:

[0120]

[0121] In the formula, h represents the above preset time step, K 1 、K 2 、K 3 、K 4 represent the slopes, K 1α represents the first slope component of the slope K 1 of K2α Represents the slope K 2 The first slope component of, K 3α Represents the slope K 3 The first slope component of, K 4α Represents the slope K 4 The first slope component of, K 1β Represents the slope K 1 The second slope component of, K 2β Represents the slope K 2 The second slope component of, K 3β Represents the slope K 3 The second slope component of, K 4β Represents the slope K 4 The second slope component of, i(k) represents the output current at the current signal sampling period k, i(k - h) represents the historical output current at a distance of h from the current signal sampling period, i(k - 2h) represents the historical output current at a distance of 2h from the current signal sampling period, and i(k - 3h) represents the historical output current at a distance of 3h from the current signal sampling period.

[0122] Furthermore, the following formula is used to calculate F α and F β The model of:

[0123]

[0124] Specifically, substituting the first output voltage component, the first slope component, the second output voltage component, and the second slope component into the above formula for calculating F α and F β In the model of, the first perturbation component on the α-axis and the second perturbation component on the β-axis in the above stationary coordinate system can be calculated.

[0125] In this preferred embodiment, the first perturbation component on the α-axis in the stationary coordinate system and the second perturbation component on the β-axis in the above stationary coordinate system are calculated according to the output voltage and the slope.

[0126] In another preferred embodiment, calculating the above predicted output current component according to the above output voltage, the first perturbation component, the second perturbation component, the sampled output current, and the above sampling duration includes:

[0127] Calculating the first output current component of the above sampled output current on the α-axis in the stationary coordinate system and the second output current component on the β-axis in the above stationary coordinate system according to the above sampled output current;

[0128] According to the above first disturbance component, first output voltage component, sampling duration, and first output current component, calculate the first predicted output current component on the α-axis of the above-mentioned stationary coordinate system;

[0129] According to the above second disturbance component, second output voltage component, sampling duration, and second output current component, calculate the second predicted output current component on the β-axis of the above-mentioned stationary coordinate system.

[0130] Specifically, according to the super-local model of the system, the energy storage converter model, and using the fourth-order four-stage Runge-Kutta for the differential formula on the left side of the above energy storage converter model, obtain the model-free parameter prediction equation for the inductor current:

[0131]

[0132] Specifically, substitute the first output voltage component, second output voltage component, first disturbance component, second disturbance component, first output current component, second output current component, and sampling duration into the above model-free parameter prediction equation, and then the predicted output current component can be calculated.

[0133] Specifically, the above inductor current is the output current of the energy storage converter when connected to the grid.

[0134] Specifically, the energy storage converter has a total of 8 switching states. For each switching state, there is a group of U α and U β . By calculating the 8 groups of output voltages in sequence, the first predicted output current component i α (k + 1), and the second predicted output current component i β (k + 1) corresponding to each of the 8 switching states can be obtained.

[0135] Schematically, as shown in part c of Figure 3 , input the first output current component i α , the second output current component i β , the first output voltage component U α , and the second output voltage component U β into the "model-free parameter inductor current prediction model", that is, the above "model-free parameter prediction equation for the inductor current", and then the predicted output current component can be calculated.

[0136] Preferably, it can be seen from the model-free parameter prediction equation for the inductor current that when the inductor parameter changes, the error can be compensated by F α and F β , and there is no need to calculate the relevant inductor parameter values, which overcomes the problem of dependence on parameters in the prediction process.

[0137] In this preferred embodiment, a predicted output current component is calculated based on a first output voltage component, a second output voltage component, a first disturbance component, a second disturbance component, a first output current component, a second output current component, and a sampling duration.

[0138] In another preferred embodiment, determining the target switching state of the energy storage converter according to the predicted output current component and the virtual reference current includes:

[0139] Based on the virtual reference current, a first virtual reference current component on the α-axis of the stationary coordinate system of the virtual reference current and a second virtual reference current component on the β-axis are obtained;

[0140] Calculate the first absolute value of the difference between the first virtual reference current component and the first predicted output current;

[0141] Calculate the second absolute value of the difference between the second virtual reference current component and the second predicted output current;

[0142] Take the sum of the first absolute value and the second absolute value as the value function value of the energy storage converter, and then obtain the value function values of the energy storage converter in each switching state; where each value function value corresponds to a switching state;

[0143] Specifically, the value function calculation formula is shown as follows:

[0144]

[0145] In the formula, J 1 represents the value function value, represents the reference value component of the output current of the energy storage converter on the α-axis of the stationary coordinate system at the (k + 1)-th signal sampling period, and its value is the component of the virtual reference current i ref on the α-axis of the stationary coordinate system, represents the reference value component of the output current of the energy storage converter on the β-axis of the stationary coordinate system at the (k + 1)-th signal sampling period, and its value is the component of the virtual reference current i ref on the β-axis of the stationary coordinate system.

[0146] Take the switching state corresponding to the minimum value function value as the target switching state.

[0147] Specifically, 8 switching states will obtain 8 value function values, and take the switching state corresponding to the minimum value function value among the 8 value function values as the target switching state.

[0148] Preferably, the above-mentioned switching control method of the energy storage converter based on virtual impedance avoids the complex PI parameter tuning, improves the problems such as overshoot inherent in the PI controller, and has a faster dynamic response and stronger robustness in the prediction and control processes than the traditional PI control. At the same time, when the circuit parameters are mismatched, this method has better current tracking ability and lower THD. After introducing virtual impedance, the control loop of the traditional double closed-loop is simplified, and the dynamic response speed and grid connection performance are improved.

[0149] Preferably, compared with the multi-loop VSG (energy storage converter) control, the model-free parameter prediction equation of the inductor current proposed in this method replaces the current loop under the traditional PI controller, reduces the complexity of the control structure and the difficulty of control parameter design, reduces the output error, and enhances the parameter robustness. At the same time, this method can predict the future evolution trajectory of the state variables without system parameters (such as the gain parameters of the PI controller, etc.). It avoids the introduction of parameter values in stages such as delay compensation, prediction, and value function screening, is applicable to non-linear complex systems such as energy storage converters, has low algorithm complexity, and is not affected by the accuracy of modeling.

[0150] Preferably, compared with the traditional double closed-loop system with voltage outer loop and current inner loop, this method simplifies the control loop, has faster dynamic performance, improves the dynamic characteristics during the grid connection operation of the VSG, and realizes the fast and effective smooth grid connection of the energy storage converter.

[0151] In this preferred embodiment, by predicting the output current component and the above-mentioned virtual reference current, the target switching state of the energy storage converter is determined, and then the switching control of the energy storage converter is realized according to the target switching state.

[0152] Based on the above method item embodiments, the present invention correspondingly provides device item embodiments.

[0153] As Figure 4 shown, an embodiment of the present invention provides a switching control device for an energy storage converter based on virtual impedance, including:

[0154] A first data acquisition module, a frequency loop equation construction module, a voltage loop equation construction module, a virtual reference current equation construction module, a control model construction module, a second data acquisition module, and an energy storage converter control module;

[0155] The above-mentioned first data acquisition module is used to acquire the electrical angular velocity of the synchronous generator, the synchronous rotational angular velocity of the power grid, the virtual input mechanical power, the active power reference value, the capacitor voltage reference value, the reactive power reference value, the output electromagnetic power, the reactive power of the energy storage converter, the rated voltage amplitude, the capacitor voltage, the virtual inductor, and the virtual resistor;

[0156] The above frequency loop equation construction module is used to construct the active power - frequency loop equation of the energy storage converter according to the electrical angular velocity of the synchronous generator, the synchronous rotating angular velocity of the power grid, the input virtual mechanical power, the active power reference value, and the output electromagnetic power;

[0157] The above voltage loop equation construction module is used to construct the reactive power - voltage loop equation of the energy storage converter according to the reactive power of the energy storage converter, the capacitor voltage reference value, the reactive power reference value, and the rated voltage amplitude;

[0158] The above virtual reference current equation construction module is used to construct the virtual reference current equation of the energy storage converter according to the capacitor voltage reference value, the capacitor voltage, the virtual inductor, and the virtual resistor;

[0159] The above control model construction module is used to construct the outer - loop control model of the energy storage converter according to the active power - frequency loop equation, the virtual reference current equation, and the reactive power - voltage loop equation;

[0160] The above second data acquisition module is used to acquire the output voltage of the energy storage converter in each switching state and acquire the sampled output current at a preset time step;

[0161] The above energy storage converter control module is used to calculate the target switching state of the energy storage converter according to the outer - loop control model of the energy storage converter, the output voltage, and the sampled output current, and control the energy storage converter according to the target switching state.

[0162] It should be noted that the device embodiments described above are merely illustrative. The modules described as separate components may or may not be physically separated, and the components shown as modules may or may not be physical modules, that is, they may be located in one place or distributed to multiple network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the solution of this embodiment. In addition, in the attached drawings of the device embodiments provided by the present invention, the connection relationship between the modules indicates that there is a communication connection between them, which can be specifically implemented as one or more communication buses or signal lines. Those of ordinary skill in the art can understand and implement without creative efforts. The above schematic diagram is merely an example of a switching control device for an energy storage converter based on virtual impedance, and does not constitute a limitation on a switching control device for an energy storage converter based on virtual impedance. It may include more or fewer components than shown in the figure, or combine some components, or different components.

[0163] Based on the above - mentioned method - item embodiments, the present invention correspondingly provides terminal - device - item embodiments.

[0164] Another embodiment of the present invention provides a terminal device, including a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor. When the processor executes the computer program, a method for controlling a switch of an energy storage converter based on virtual impedance in any one of the embodiments of the present invention is implemented.

[0165] Exemplarily, in this embodiment, the computer program may be divided into one or more modules. The one or more modules are stored in the memory and executed by the processor to complete the present invention. The one or more module elements may be a series of computer program instruction segments capable of performing specific functions, and the instruction segments are used to describe the execution process of the computer program in the device.

[0166] The terminal device may be a computing device such as a desktop computer, a notebook, a palm computer, and a cloud server. The device may include, but is not limited to, a processor and a memory.

[0167] The so-called processor may be a central processing module (Central Processing Unit, CPU), or may also be other general-purpose processors, digital signal processors (Digital Signal Processor, DSP), application specific integrated circuits (Application Specific Integrated Circuit, ASIC), off-the-shelf programmable gate arrays (Field-Programmable Gate Array, FPGA), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or the processor may also be any conventional processor, etc. The processor is the control center of the device, and connects various parts of the entire device through various interfaces and lines.

[0168] The memory may be used to store the computer program and / or module. The processor realizes various functions of the device by running or executing the computer program and / or module stored in the memory, and calling the data stored in the memory. The memory may mainly include a program storage area and a data storage area. Among them, the program storage area may store an operating system, application programs required for at least one function, etc. In addition, the memory may include a high-speed random access memory, and may also include a non-volatile memory, such as a hard disk, a memory, a plug-in hard disk, a smart media card (Smart Media Card, SMC), a secure digital (Secure Digital, SD) card, a flash card (Flash Card), at least one magnetic disk storage device, a flash device, or other volatile solid-state storage devices.

[0169] Based on the above method embodiments, the present invention correspondingly provides storage medium embodiments.

[0170] Another embodiment of the present invention provides a storage medium. The above storage medium includes a stored computer program. When the computer program runs, it controls the device where the storage medium is located to execute the method for controlling the switch of an energy storage converter based on virtual impedance according to any one of the embodiments of the present invention.

[0171] In this embodiment, the above storage medium is a computer-readable storage medium. The above computer program includes computer program code, and the computer program code can be in the form of source code, object code, executable file or some intermediate form, etc. The above computer-readable medium can include: any entity or device capable of carrying the above computer program code, recording medium, USB flash drive, mobile hard disk, magnetic disk, optical disc, computer memory, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), electrical carrier signal, telecommunication signal, and software distribution medium, etc.

[0172] Compared with the prior art, by implementing the above various embodiments of the present invention, the entire control process can be made simpler than the linear control method based on PI control.

[0173] The above is the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements are also regarded as the protection scope of the present invention.

Claims

1. A switch control method for an energy storage converter based on virtual impedance, characterized in that: include: Obtaining the electrical angular velocity of the synchronous generator, the synchronous rotation angular velocity of the power grid, the virtual input mechanical power, the active power reference value, the capacitor voltage reference value, the reactive power reference value, the output electromagnetic power, the energy storage converter reactive power, the rated voltage amplitude, the capacitor voltage, the virtual inductance and the virtual resistance; According to the electrical angular velocity of the synchronous generator, the synchronous rotation angular velocity of the power grid, the input virtual mechanical power, the active power reference value and the output electromagnetic power, an active power-frequency loop equation of the energy storage converter is constructed; According to the reactive power of the energy storage converter, the capacitor voltage reference value, the reactive power reference value and the rated voltage amplitude, a reactive power-voltage loop equation of the energy storage converter is constructed; Constructing a virtual reference current equation of the energy storage converter according to the capacitor voltage reference value, the capacitor voltage, the virtual inductance and the virtual resistance; According to the active power-frequency loop equation, the virtual reference current equation and the reactive power-voltage loop equation, an outer loop control model of the energy storage converter is constructed; Obtaining the output voltage of the energy storage converter in each switching state, and obtaining the sampled output current according to a preset time step; The target switching state of the energy storage converter is calculated according to the outer loop control model of the energy storage converter, the output voltage and the sampled output current, and the energy storage converter is controlled according to the target switching state.

2. A virtual impedance based energy storage converter switch control method according to claim 1, characterized in that: The step of obtaining the sampled output current according to the preset time step comprises: Obtaining the output current of the energy storage converter in the current signal sampling period; Starting with the output current in the current signal sampling period, sequentially acquiring a preset number of historical output currents before the current signal sampling period according to the preset time step; The sampled output current is obtained according to the output current in the current signal sampling period and the historical output current.

3. The energy storage converter switch control method based on virtual impedance according to claim 2 is characterized in that: The step of calculating the target switching state of the energy storage converter according to the outer loop control model of the energy storage converter, the output voltage and the sampled output current includes: According to the energy storage converter outer loop control model, a virtual reference current is calculated; Calculating the slope of the sampled output current according to the sampled output current and the preset time step; Calculate, according to the slope, the output voltage and the sampled output current, the predicted output current components of each switch state of the energy storage converter in the stationary coordinate system during the next sampling period; A target switching state of the energy storage converter is determined according to the predicted output current component and the virtual reference current.

4. The energy storage converter switch control method based on virtual impedance according to claim 3 is characterized in that: The predicted output current components of each switching state of the energy storage converter in the stationary coordinate system during the next sampling period are calculated according to the slope, the output voltage and the sampled output current, including: Obtaining the sampling duration of the signal sampling period; According to the output voltage and the slope, a first disturbance component on the α-axis of the stationary coordinate system and a second disturbance component on the β-axis of the stationary coordinate system are calculated; The predicted output current component is calculated according to the output voltage, the first disturbance component, the second disturbance component, the sampled output current and the sampling duration.

5. The energy storage converter switch control method based on virtual impedance according to claim 4 is characterized in that: The step of calculating a first disturbance component on the α-axis of the stationary coordinate system and a second disturbance component on the β-axis of the stationary coordinate system according to the output voltage and the slope comprises: According to the output voltage, a first output voltage component of the output voltage on the α-axis of the stationary coordinate system and a second output voltage component on the β-axis of the stationary coordinate system are calculated; According to the slope, a first slope component of the slope on the α-axis of the stationary coordinate system and a second slope component of the slope on the β-axis of the stationary coordinate system are calculated; Calculating a first disturbance component on the α-axis of the stationary coordinate system according to the first output voltage component and the first slope component; A second disturbance component on the β-axis of the stationary coordinate system is calculated according to the second output voltage component and the second slope component.

6. A virtual impedance based energy storage converter switch control method according to claim 5, characterized in that: The step of calculating the predicted output current component according to the output voltage, the first disturbance component, the second disturbance component, the sampled output current and the sampling duration includes: According to the sampled output current, a first output current component of the sampled output current on the α-axis of the stationary coordinate system and a second output current component on the β-axis of the stationary coordinate system are calculated; Calculate a first predicted output current component on the α-axis of the stationary coordinate system according to the first disturbance component, the first output voltage component, the sampling duration, and the first output current component; A second predicted output current component on the β axis of the stationary coordinate system is calculated according to the second disturbance component, the second output voltage component, the sampling duration, and the second output current component.

7. A virtual impedance based energy storage converter switch control method according to claim 6, characterized in that: The step of determining a target switching state of the energy storage converter according to the predicted output current component and the virtual reference current includes: According to the virtual reference current, obtaining a first virtual reference current component of the virtual reference current on the α-axis of the stationary coordinate system and a second virtual reference current component on the β-axis; calculating a first absolute value of a difference between the first virtual reference current component and a first predicted output current; calculating a second absolute value of a difference between the second virtual reference current component and a second predicted output current; The sum of the first absolute value and the second absolute value is used as the value function value of the energy storage converter, and then the value function value of the energy storage converter in each switching state is obtained; wherein each value function value corresponds to a switching state; The switch state corresponding to the minimum value of the cost function is used as the target switch state.

8. A switch control device for an energy storage converter based on virtual impedance, characterized in that: include: A first data acquisition module, a frequency loop equation construction module, a voltage loop equation construction module, a virtual reference current equation construction module, a control model construction module, a second data acquisition module and an energy storage converter control module; The first data acquisition module is used to acquire the electrical angular velocity of the synchronous generator, the synchronous rotation angular velocity of the power grid, the virtual input mechanical power, the active power reference value, the capacitor voltage reference value, the reactive power reference value, the output electromagnetic power, the energy storage converter reactive power, the rated voltage amplitude, the capacitor voltage, the virtual inductance and the virtual resistance; The frequency loop equation construction module is used to construct an active power-frequency loop equation of the energy storage converter according to the electrical angular velocity of the synchronous generator, the synchronous rotation angular velocity of the power grid, the input virtual mechanical power, the active power reference value and the output electromagnetic power; The voltage loop equation construction module is used to construct a reactive power-voltage loop equation of the energy storage converter according to the reactive power of the energy storage converter, the capacitor voltage reference value, the reactive power reference value and the rated voltage amplitude; The virtual reference current equation construction module is used to construct a virtual reference current equation of the energy storage converter according to the capacitor voltage reference value, the capacitor voltage, the virtual inductance and the virtual resistance; The control model building module is used to build an outer loop control model of the energy storage converter according to the active power-frequency loop equation, the virtual reference current equation and the reactive power-voltage loop equation; The second data acquisition module is used to obtain the output voltage of the energy storage converter in each switching state, and obtain the sampled output current according to a preset time step; The energy storage converter control module is used to calculate the target switching state of the energy storage converter according to the outer loop control model of the energy storage converter, the output voltage and the sampled output current, and control the energy storage converter according to the target switching state.

9. A terminal device, characterized in that: It comprises a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, wherein when the processor executes the computer program, a virtual impedance-based energy storage converter switch control method as described in any one of claims 1 to 7 is implemented.

10. A storage medium, characterized in that: The storage medium includes a stored computer program, wherein when the computer program is running, the device where the storage medium is located is controlled to execute a virtual impedance-based energy storage converter switch control method as described in any one of claims 1 to 7.

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