Method and device for controlling network-forming type energy storage converter

Abstract

The invention provides a control method and device for a network-forming type energy storage converter, and belongs to the field of energy storage converter control. The method comprises the following steps: acquiring three-phase current and three-phase voltage of a grid-connected point of a target network-building type energy storage converter; according to the three-phase current and the three-phase voltage, determining active output power, reactive output power, and resistance and reactance of a power grid to which the target network-forming type energy storage converter belongs; based on the resistance and the reactance, outer ring self-adaptive parameters are calculated; wherein the outer ring adaptive parameter is used for performing VSG control; and according to the outer-loop adaptive parameter, the three-phase current, the three-phase voltage, the active output power and the reactive output power, controlling the target network-forming type energy storage converter. According to the invention, the active control strategy and the reactive control strategy in VSG control are improved based on the outer-loop adaptive parameters, so that the problem of coupling between the damping coefficient and the primary frequency modulation coefficient is solved, and the situation that the control performance is reduced and unstable due to the change of the impedance of the power grid is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of energy storage converter control, and in particular to a control method and device for a grid-type energy storage converter. Background Art

[0002] Grid-type energy storage converters are regarded as key equipment to support the stable operation of new power systems because they have similar external operating characteristics to conventional synchronous generators. Among them, the Virtual Synchronous Generator (VSG) control strategy simulates the rotor motion equation, primary frequency regulation characteristics and primary voltage regulation characteristics, and has attracted extensive attention from scholars at home and abroad. More and more grid-type energy storage converters have been put into application and operation in demonstration projects.

[0003] The traditional VSG control strategy has the problem of mutual coupling between the primary frequency modulation coefficient and the damping coefficient, as well as the problem of grid strength adaptability when using fixed control parameters. The former will cause the energy storage converter to fail to realize the primary frequency modulation function according to the grid guidelines, while the latter will cause the energy storage converter to fail to operate stably under different grid conditions, threatening the safe and stable operation of the power system. In addition, in order to ensure that the control parameters can change adaptively, it is necessary to obtain grid impedance information. In the traditional method of obtaining grid impedance information, considering that the active measurement method of injecting non-characteristic harmonics into the system needs to have high measurement accuracy, the Fourier transform method and the complex filter just meet this requirement, but the traditional Fourier transform method has the problem of spectrum leakage. The complex coefficient filter (CCF) can effectively avoid the problem of spectrum leakage, but the traditional double complex filter structure needs to separate the positive and negative sequences separately when using it, which is more complicated.

[0004] That is, at present, there is a lack of effective means to solve the problems of mutual coupling between the primary frequency modulation coefficient and the damping coefficient in traditional VSG control strategies, as well as the problem of grid strength adaptability when using fixed control parameters. Summary of the invention

[0005] The embodiment of the present invention provides a control method and device for a grid-type energy storage converter to solve the problems of mutual coupling between the primary frequency modulation coefficient and the damping coefficient in the traditional VSG control strategy, and the problem of grid strength adaptability when using fixed control parameters.

[0006] In a first aspect, an embodiment of the present invention provides a control method for a grid-connected energy storage converter, comprising:

[0007] Collect the three-phase current and three-phase voltage of the target grid-connected energy storage converter;

[0008] Determine the active output power, reactive output power, and the resistance and reactance of the power grid to which the target grid-type energy storage converter belongs according to the three-phase current and the three-phase voltage;

[0009] Based on the resistance and reactance, outer loop adaptive parameters are calculated; wherein the outer loop adaptive parameters are used for VSG control;

[0010] The target grid-type energy storage converter is controlled according to the outer loop adaptive parameters, three-phase current, three-phase voltage, active output power and reactive output power.

[0011] In a possible implementation, the resistance and reactance of the power grid to which the target grid-type energy storage converter belongs are determined according to the three-phase current and the three-phase voltage, including:

[0012] Inputting the αβ-axis components corresponding to the three-phase current and the three-phase voltage into the improved composite filter respectively, to obtain a current harmonic signal of a first preset frequency and a voltage harmonic signal of a first preset frequency; wherein the improved composite filter is determined based on a second-order generalized integrator and a complex filter;

[0013] The resistance and reactance of the power grid to which the target grid-type energy storage converter belongs are calculated according to the current harmonic signal of the first preset frequency and the voltage harmonic signal of the first preset frequency.

[0014] In one possible implementation, the improved composite filter is:

[0015]

[0016] Among them, ω c is the cutoff angular frequency of the second-order generalized integrator, ω0 is the resonant angular frequency of the second-order generalized integrator, ω hc is the cutoff frequency of the composite filter, ω h1.5 is the resonant angular frequency of the composite filter.

[0017] In a possible implementation, the target grid-type energy storage converter is controlled according to the outer loop adaptive parameters, three-phase current, three-phase voltage, active output power and reactive output power, including:

[0018] Calculate the three-phase internal potential according to the outer loop adaptive parameters, active output power and reactive output power;

[0019] Calculate the current reference values ​​on the dq axis components according to the three-phase internal potential and the three-phase voltage;

[0020] Calculate the voltage reference value on the dq axis components according to the current reference value on the dq axis components, the three-phase current and the current harmonic signal of the second preset frequency; wherein the current harmonic signal of the second preset frequency is determined based on the current harmonic signal of the first preset frequency;

[0021] The trigger signal of each switch tube in the target energy storage converter is determined according to the voltage reference value on the dq axis component to control the target grid-type energy storage converter.

[0022] In a possible implementation, the three-phase internal potential is calculated according to the outer loop adaptive parameters, the active output power and the reactive output power, including:

[0023] Input the active frequency control parameters and active output power in the outer loop adaptive parameters into the active-frequency control loop to obtain the phase of the inner potential;

[0024] Input the reactive voltage control parameters and reactive output power in the outer loop adaptive parameters into the reactive-voltage control loop to obtain the amplitude of the inner potential;

[0025] The three-phase internal potential is calculated based on the phase angle and amplitude.

[0026] In a possible implementation, calculating a voltage reference value on the dq axis components according to the current reference value on the dq axis components, the three-phase current, and the current harmonic signal of the second preset frequency includes:

[0027] The current reference value on the dq axis components, the three-phase current and the current harmonic signal of the second preset frequency are input into the current inner loop to obtain the voltage reference value on the dq axis components.

[0028] In a possible implementation, the outer loop adaptive parameters are calculated based on the resistance and reactance, including:

[0029] Input the resistance and reactance into the VSG power outer loop control parameter calculation formula to obtain the outer loop adaptive parameters; wherein the outer loop adaptive parameters include active frequency control parameters and reactive voltage control parameters;

[0030] The active frequency control parameters include the natural oscillation frequency, cutoff frequency and equivalent damping coefficient in the active model of the improved VSG control strategy based on the reshaping of damping characteristics;

[0031] The reactive voltage control parameters include proportional coefficient and integral coefficient.

[0032] In a possible implementation, the VSG power outer loop control parameter calculation formula is:

[0033]

[0034] Among them, ω np is the natural oscillation frequency of the active-frequency loop system; p is the relative position of the real pole and the real part of the conjugate pole; ζ p is the damping ratio of the active control system; E sis the internal potential amplitude; U g is the voltage amplitude at the power supply end of the power grid; ω N is the rated angular frequency of the power grid; k f is the primary frequency modulation coefficient; J is the moment of inertia of the system; X f and X g are filter reactance and grid reactance respectively; D eq is the equivalent damping coefficient of the proposed improved VSG control strategy based on damping characteristic reshaping; ω p is the cut-off frequency; k v is the proportionality coefficient; k i is the integral coefficient; ζ q is the damping ratio; ω nq is the natural oscillation frequency; ω q is the low-pass filter cutoff frequency.

[0035] In a possible implementation, determining the active output power and the reactive output power according to the three-phase current and the three-phase voltage includes:

[0036] The first coordinate transformation is applied to the three-phase current and the three-phase voltage respectively to obtain the αβ axis components corresponding to the three-phase current and the three-phase voltage;

[0037] The αβ-axis components corresponding to the three-phase current and the three-phase voltage are respectively transformed by the second coordinate transformation to obtain the dq-axis components corresponding to the three-phase current and the three-phase voltage;

[0038] The active output power and reactive output power are calculated based on the dq-axis components corresponding to the three-phase current and the three-phase voltage.

[0039] In a second aspect, an embodiment of the present invention provides a control device for a grid-type energy storage converter, comprising:

[0040] A collection module, used to collect the three-phase current and three-phase voltage of the target grid-connected energy storage converter;

[0041] A calculation module, used to determine the active output power, reactive output power, and the resistance and reactance of the power grid to which the target grid-type energy storage converter belongs according to the three-phase current and the three-phase voltage;

[0042] A determination module is used to calculate an outer loop adaptive parameter based on the resistance and the reactance; wherein the outer loop adaptive parameter is used for VSG control;

[0043] The control module is used to control the target grid-type energy storage converter according to the outer loop adaptive parameters, three-phase current, three-phase voltage, active output power and reactive output power.

[0044] The embodiment of the present invention provides a control method and device for a grid-type energy storage inverter. Compared with the prior art, the embodiment of the present invention has the following advantages: improving the active control strategy in VSG control based on outer loop adaptive parameters can solve the coupling problem between the damping coefficient and the primary frequency modulation coefficient; improving the reactive control strategy in VSG control based on outer loop adaptive parameters can avoid the reduction of control performance and possible instability caused by changes in grid impedance; it can be seen that the method provided by the embodiment of the present invention can effectively solve the problem of mutual coupling between the primary frequency modulation coefficient and the damping coefficient in the traditional VSG control strategy, and the problem of grid strength adaptability when using fixed control parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0046] Figure 1 is a flow chart of the implementation of the control method of the grid-type energy storage converter provided by the embodiment of the present invention;

[0047] Figure 2 It is a resistance reactance calculation block diagram of a control method for a grid-type energy storage converter provided in an embodiment of the present invention;

[0048] Figure 3 It is a VSG control block diagram of a control method for a grid-type energy storage converter provided by an embodiment of the present invention;

[0049] Figure 4 is a control block diagram of a control method for a grid-type energy storage converter provided by an embodiment of the present invention;

[0050] Figure 5 It is a structural schematic diagram of a control device for a grid-type energy storage converter provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0051] In the following description, specific details such as specific system structures, technologies, etc. are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present invention. However, it should be clear to those skilled in the art that the present invention may be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to prevent unnecessary details from obstructing the description of the present invention.

[0052] In order to make the purpose, technical solutions and advantages of the present invention more clear, specific embodiments will be described below in conjunction with the accompanying drawings.

[0053] Figure 1 It is a flow chart for implementing the control method of the grid-type energy storage converter provided in an embodiment of the present invention.

[0054] like Figure 1 As shown, the method includes:

[0055] Step 110: Collect the three-phase current and three-phase voltage of the target grid-connected energy storage converter.

[0056] In this embodiment, the three-phase current and three-phase voltage of the target grid-connected energy storage converter can be sampled to obtain the three-phase current i apcc ,i bpcc ,i cpcc , and the three-phase voltage u apcc ,u bpcc ,u cpcc , where the subscripts “a”, “b”, and “c” correspond to the A-phase, B-phase, and C-phase voltage and current, respectively.

[0057] Step 120: Determine the active output power, reactive output power, and the resistance and reactance of the power grid to which the target grid-type energy storage converter belongs according to the three-phase current and the three-phase voltage.

[0058] In this embodiment, the determination of the active output power, the reactive output power, and the resistance and reactance of the power grid to which the target grid-forming energy storage converter belongs can be implemented in two steps, which are described below respectively.

[0059] Accordingly, in an optional embodiment, determining the active output power and the reactive output power according to the three-phase current and the three-phase voltage may include:

[0060] The first coordinate transformation is performed on the three-phase current and the three-phase voltage respectively to obtain the αβ axis components corresponding to the three-phase current and the three-phase voltage.

[0061] The αβ-axis components corresponding to the three-phase current and the three-phase voltage are respectively transformed by the second coordinate transformation to obtain the dq-axis components corresponding to the three-phase current and the three-phase voltage.

[0062] The active output power and reactive output power are calculated based on the dq-axis components corresponding to the three-phase current and the three-phase voltage.

[0063] In this embodiment, the first coordinate transformation may be a 3s / 2s transformation, and the second coordinate transformation may be a 2s / 2r transformation. Specifically, after obtaining the three-phase current and the three-phase voltage, the three-phase current and the three-phase voltage are firstly subjected to coordinate transformation, that is, the three-phase current and the three-phase voltage may be subjected to a 3s / 2s transformation to obtain the αβ axis components corresponding to the three-phase current and the three-phase voltage, that is, u α ,uβ and i α ,i β Among them, the 3s / 2s transformation formula of three-phase current and three-phase voltage can be expressed as:

[0064]

[0065] Then, the voltage and current under the αβ axis of the two-phase stationary coordinate system are transformed by 2s / 2r to obtain the dq axis components corresponding to the three-phase current and three-phase voltage, that is, u d ,u q and i d ,i q .

[0066] Among them, u d ,u q and i d ,i q The calculation formulas can be expressed as:

[0067]

[0068] Wherein θ is the phase angle, which is determined in the specific steps corresponding to step 140. Since this part describes the process of determining the active output power and the reactive output power, the detailed determination process of the phase angle will be described in the relevant steps of step 140 and will not be expanded here.

[0069] According to the dq-axis components corresponding to the obtained three-phase current and three-phase voltage, the output active power and reactive output power of the target grid-type energy storage converter are calculated using the instantaneous power theory. The calculation formula is as follows:

[0070]

[0071] After describing the process of calculating active output power and reactive output power, the process of calculating resistance and reactance is described in detail below.

[0072] Accordingly, in an optional embodiment, determining the resistance and reactance of the power grid to which the target grid-type energy storage converter belongs according to the three-phase current and the three-phase voltage may include:

[0073] The αβ-axis components corresponding to the three-phase current and the three-phase voltage are respectively input into the improved composite filter to obtain a current harmonic signal of a first preset frequency and a voltage harmonic signal of a first preset frequency; wherein the improved composite filter is determined based on a second-order generalized integrator and a complex filter.

[0074] The resistance and reactance of the power grid to which the target grid-type energy storage converter belongs are calculated according to the current harmonic signal of the first preset frequency and the voltage harmonic signal of the first preset frequency.

[0075] Figure 2 The block diagram of the resistance reactance calculation of the control method of the grid-type energy storage converter provided by the embodiment of the present invention is as follows. Figure 2 This embodiment is described.

[0076] In this embodiment, in order to calculate the resistance and reactance, this embodiment is implemented by two parts: harmonic extraction and resistance and reactance calculation. Considering the problem of spectrum leakage in the traditional Fourier transform method, this embodiment proposes a new improved composite filter and an improved grid impedance measurement method to obtain the resistance and reactance of the grid to which the target grid-type energy storage converter belongs.

[0077] In this embodiment, the improved composite filter can be expressed as:

[0078]

[0079] Among them, ω c is the cutoff angular frequency of the second-order generalized integrator, ω0 is the resonant angular frequency of the second-order generalized integrator, and its value is the fundamental angular frequency of the power grid, ω hc is the cutoff frequency of the composite filter, ω h1.5 is the resonant angular frequency of the composite filter, and its value is the angular frequency corresponding to the first preset frequency.

[0080] Since the three-phase current and voltage have been transformed to calculate the active power and reactive power, the αβ axis components corresponding to the three-phase current and three-phase voltage are obtained, that is, u α ,u β and i α ,i β Therefore, this step will not be described in detail in this embodiment.

[0081] will u α ,u β and i α ,i β Input into the improved composite filter, extract the non-specific harmonics, and obtain the current harmonic signal of the first preset frequency and the voltage harmonic signal of the first preset frequency, that is, and The first preset frequency may be 75 Hz, and accordingly, the current harmonic signal of the first preset frequency and the voltage harmonic signal of the first preset frequency may be current and voltage of non-characteristic subharmonics of 75 Hz.

[0082] According to the impedance definition, the resistance and reactance of the power grid to which the target grid-type energy storage converter belongs under the αβ axis are calculated by the following formula:

[0083]

[0084] Among them, R g_est is the resistance; L g_est is the inductance; U α is a voltage harmonic signal of a first preset frequency; I α The current harmonic signal is of a first preset frequency.

[0085] In order to effectively solve the problem of mutual coupling between the primary frequency modulation coefficient and the damping coefficient in the traditional VSG control strategy, and the problem of grid strength adaptability when using fixed control parameters, this embodiment provides a method as shown in step 130, and accordingly:

[0086] Step 130: Calculate outer loop adaptive parameters based on resistance and reactance; wherein the outer loop adaptive parameters are used for VSG control.

[0087] In an optional embodiment, calculating the outer loop adaptive parameters based on the resistance and reactance in step 130 may include:

[0088] The resistance and reactance are input into the VSG power outer loop control parameter calculation formula to obtain the outer loop adaptive parameters; wherein the outer loop adaptive parameters include active frequency control parameters and reactive voltage control parameters.

[0089] The active frequency control parameters include the natural oscillation frequency, cutoff frequency and equivalent damping coefficient in the active model of the improved VSG control strategy based on the reshaping of damping characteristics.

[0090] The reactive voltage control parameters include proportional coefficient and integral coefficient.

[0091] In this embodiment, the VSG power outer loop control parameter calculation formula may be:

[0092]

[0093]

[0094] Among them, ω np is the natural oscillation frequency of the active-frequency loop system; p is the relative position of the real pole and the real part of the conjugate pole; ζ p is the damping ratio of the active control system; E g is the internal potential amplitude; U g is the voltage amplitude at the power supply end of the power grid; ω N is the rated angular frequency of the power grid; k f is the primary frequency modulation coefficient; J is the moment of inertia of the system; X f and X g are filter reactance and grid reactance respectively; D eq is the equivalent damping coefficient of the proposed improved VSG control strategy based on damping characteristic reshaping; ωp is the cut-off frequency; k v is the proportionality coefficient; k i is the integral coefficient; ζ q is the damping ratio; ω nq is the natural oscillation frequency; ω q is the low-pass filter cutoff frequency.

[0095] The VSG power outer loop control parameter calculation formula can be predetermined by:

[0096] First, the small signal models of the active-frequency control loop and the reactive-voltage control loop are established respectively, and the corresponding small signal closed-loop transfer functions are obtained:

[0097]

[0098] Among them, T j is the inertia time constant; S n is the rated capacity of the energy storage converter.

[0099] According to the cubic equation ax 3 +bx 2 +cx+d=0, and the form of the root of the small signal model is determined:

[0100]

[0101] Among them, a, b, c, d are the coefficients of the cubic equation corresponding to the denominator, A, B, C, Δ are the terms of the discriminant, and F1 is the parameter expression separated by simplifying the expression. When the discriminant Δ satisfies the condition greater than 0, there is a pole on the real axis and a pair of conjugate poles.

[0102] When the relative position p of the real pole and the real part of the conjugate pole is large, the real pole has no dominant influence on the dynamic response of the system, thereby achieving the order reduction of the small signal model. The transfer function of the active output power after order reduction can be expressed as:

[0103]

[0104] The general expression of the transfer function of the standard second-order system with zero point used for comparison is:

[0105]

[0106] In the formula, ω n is the natural oscillation frequency of the system, ζ is the damping ratio of the system, and z is the negative number of the zero point of the system.

[0107] Based on the small signal model of active-frequency control and reactive-voltage control after order reduction, by comparing the transfer function of the second-order system with zero point, the relationship and constraints between the corresponding parameters are obtained jointly, so as to deduce the connection between the grid strength and the power outer loop control parameters, and then obtain the calculation formula of VSG power outer loop control parameters.

[0108] Step 140: Control the target grid-connected energy storage converter according to the outer loop adaptive parameters, three-phase current, three-phase voltage, active output power and reactive output power.

[0109] In this embodiment, the target grid-type energy storage inverter can be controlled based on the outer loop adaptive parameters, three-phase current, three-phase voltage, active output power and reactive output power by calculating the three-phase internal potential, calculating the current reference value on the dq-axis components, and calculating the voltage reference value on the dq-axis components.

[0110] Accordingly, in an optional embodiment, in step 140, controlling the target grid-type energy storage converter according to the outer loop adaptive parameters, three-phase current, three-phase voltage, active output power and reactive output power may include:

[0111] The three-phase internal potential is calculated based on the outer loop adaptive parameters, active output power and reactive output power.

[0112] According to the three-phase internal potential and three-phase voltage, the current reference values ​​on the dq axis components are calculated.

[0113] The voltage reference value on the dq axis components is calculated according to the current reference value on the dq axis components, the three-phase current and the current harmonic signal of the second preset frequency; wherein the current harmonic signal of the second preset frequency is determined based on the current harmonic signal of the first preset frequency.

[0114] The trigger signal of each switch tube in the target energy storage converter is determined according to the voltage reference value on the dq axis component to control the target grid-type energy storage converter.

[0115] In this embodiment, the essence of controlling the target grid-type energy storage converter is to calculate the voltage command v in the three-phase stationary coordinate system according to the voltage reference value and phase on the dq axis component by using the 2r / 3s transformation. aref , v bref , v cref ; That is, the three-phase voltage reference value. The calculation formula of the three-phase voltage reference value is as follows:

[0116]

[0117] According to the three-phase voltage reference value, the duty cycle is calculated to obtain a three-phase duty cycle signal, and the three-phase duty cycle signal is output for modulation to obtain a trigger signal of each switch tube in the target grid-type energy storage converter to control the target energy storage converter.

[0118] Among them, the calculation formula of the three-phase duty cycle signal is:

[0119]

[0120] Among them, U dc is the voltage of the DC side energy storage battery.

[0121] Optionally, calculating the three-phase internal potential according to the outer loop adaptive parameter, the active output power and the reactive output power may include:

[0122] The active frequency control parameters and active output power in the outer loop adaptive parameters are input into the active-frequency control loop to obtain the phase of the inner potential.

[0123] The reactive voltage control parameters and reactive output power in the outer loop adaptive parameters are input into the reactive-voltage control loop to obtain the amplitude of the inner potential.

[0124] The three-phase internal potential is calculated based on the phase angle and amplitude.

[0125] Figure 3 The VSG control block diagram of the control method of the grid-type energy storage converter provided by the embodiment of the present invention is shown below in combination with Figure 3 This embodiment is described:

[0126] In this embodiment, the active power reference value P ref , active output power and the calculated active frequency control parameters, the improved active control strategy with the proposed damping characteristic reshape is adopted to control the active power output of the converter and generate the phase θ of the internal potential. Correspondingly, the calculation formula of the phase θ can be:

[0127]

[0128] Among them, P out is the active output power.

[0129] According to the reactive power reference value Q ref , reactive output power and the calculated reactive-voltage control parameters, control the reactive power output of the converter, and generate the amplitude of the internal potential E ref , accordingly, the amplitude E ref It can be expressed as:

[0130]

[0131] Among them, Q out is the reactive output power.

[0132] According to the obtained phase θ and amplitude E ref , the three-phase internal potential is calculated by the following formula:

[0133]

[0134] After determining the three-phase internal potential, the difference between the three-phase internal potential and the three-phase voltage is passed through the virtual impedance loop to obtain the current reference value i in the three-phase stationary coordinate system. aref ,i bref ,i cref , which is the three-phase current reference value, and its calculation formula is as follows:

[0135]

[0136] The three-phase current reference value is transformed by 3s / 2r coordinates to obtain the current reference value dq axis component, that is, i dref ,i qref Correspondingly, the calculation formula is as follows:

[0137]

[0138] Accordingly, calculating the voltage reference value on the dq axis components according to the current reference value on the dq axis components, the three-phase current and the current harmonic signal of the second preset frequency may include:

[0139] The current reference value on the dq axis components, the three-phase current and the current harmonic signal of the second preset frequency are input into the current inner loop to obtain the voltage reference value on the dq axis components.

[0140] In this embodiment, a PI controller is used to control the grid-connected point current i under the dq axis. d ,i q Control to realize the current reference instruction i dref ,i qref The zero-error tracking is performed, and the voltage instructions of the six bridge arms of the grid-type energy storage converter are obtained. Specifically:

[0141] The current reference value on the dq axis components, the three-phase current and the current harmonic signal of the second preset frequency are input into the current inner loop to obtain the voltage reference value on the dq axis components; wherein the calculation formula of the current harmonic signal of the second preset frequency is:

[0142]

[0143] Among them, I n is the rated current of the converter.

[0144] Here, it should be noted that the essence of the second preset frequency is the same as the first preset frequency, but it is expressed in different forms in different coordinate systems. In the dq coordinate system, its coordinate axis rotates synchronously with the power grid at an angular velocity of 2.0×π×50rad / s, so the signal obtained in this coordinate system is a DC quantity. On this basis, a 25Hz AC component is superimposed, and the corresponding frequency in the abc three-phase stationary coordinate system is 75Hz. It can be seen that the second preset frequency is designed as an artificially set current command value based on the first preset frequency.

[0145] The calculation formula of the voltage reference value on the dq axis component is:

[0146]

[0147] Among them, i d_ref and i q_ref is the reference value obtained by virtual impedance calculation, L f is the total inductance of the LC filter.

[0148] Figure 4 is a control block diagram of a control method for a grid-type energy storage converter provided by an embodiment of the present invention. Figure 4 This control block diagram will be described.

[0149] In this embodiment, the three-phase voltage and three-phase current of the target grid-type energy storage converter are first collected, and then the three-phase voltage and three-phase current are transformed by 3s / 2s and 2s / 2r respectively; wherein, the αβ-axis components corresponding to the three-phase voltage and three-phase current obtained by 3s / 2s transformation are applied to the improved grid impedance measurement method. The dq-axis components corresponding to the three-phase voltage and three-phase current obtained by 2s / 2r transformation are used to calculate the active output power and reactive output power.

[0150] Then, VSG adaptive control is performed according to the active output power, reactive output power, and the resistance and inductance of the power grid calculated by the improved power grid impedance measurement method. Specifically, the αβ axis components corresponding to the three-phase voltage and the three-phase current are input into the improved composite filter to extract harmonics, and the harmonic extraction results are used to calculate the resistance and inductance of the power grid; wherein, the improved composite filter is determined based on the second-order generalized integrator (SOGI) and the complex filter CCF. By calculating the resistance and reactance of the improved composite filter, the problem of spectrum leakage in the traditional Fourier transform method can be solved. The obtained resistance and reactance are input into the VSG power outer loop control parameter calculation formula to obtain the outer loop adaptive parameters. The VSG is controlled by the outer loop adaptive parameters, the active output power and the reactive output power to obtain the corresponding three-phase internal potential, which can effectively solve the coupling problem between the damping coefficient and the primary frequency modulation coefficient, and avoid the control performance degradation and instability caused by the change of power grid impedance.

[0151] Afterwards, the three-phase current reference values ​​are calculated based on the obtained three-phase internal potentials and three-phase voltages, and the current reference values ​​on the output dq axis components are calculated based on the three-phase current reference values.

[0152] Finally, the current reference value on the dq axis components, the dq axis components corresponding to the three-phase current, and the current harmonic signal of the second preset frequency are input into the current inner loop to obtain the voltage reference value on the dq axis components; the duty cycle is calculated based on the voltage reference value and phase on the dq axis components to control the grid-type energy storage inverter according to the duty cycle.

[0153] It can be seen that the transfer function reduction method based on the pole configuration method in the embodiment of the present invention facilitates the parameter design of the improved VSG control based on the reshaping of the damping characteristics to obtain the outer loop adaptive parameters. The goal of suppressing power oscillations is achieved by improving the active-frequency control strategy, and the coupling problem between the damping coefficient and the primary frequency modulation coefficient is solved. Its adaptive outer loop parameter control strategy can adaptively adjust the power outer loop parameters of the improved VSG strategy according to the measured grid impedance, which can avoid the reduction of control performance and possible instability caused by changes in grid impedance. In addition, the grid impedance measurement method of the improved composite filter based on SOGI and CCF in the embodiment of the present invention, compared with the traditional harmonic impedance measurement method, this method not only avoids the spectrum leakage problem of the Fourier algorithm, but also can quickly and accurately obtain the measurement value.

[0154] It should be understood that the order of execution of the steps in the above embodiment does not necessarily mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiment of the present invention.

[0155] The following is an embodiment of the device of the present invention. For details not described in detail therein, reference may be made to the corresponding method embodiment described above.

[0156] Figure 5 The structure diagram of the control device of the grid-type energy storage converter provided by the embodiment of the present invention is shown. For the convenience of description, only the part related to the embodiment of the present invention is shown, which is described in detail as follows:

[0157] like Figure 5 As shown, the control device 5 of the grid-type energy storage converter includes:

[0158] The acquisition module 51 is used to acquire the three-phase current and three-phase voltage of the target grid-connected energy storage converter;

[0159] A calculation module 52, used to determine the active output power, reactive output power, and the resistance and reactance of the power grid to which the target grid-type energy storage converter belongs according to the three-phase current and the three-phase voltage;

[0160] A determination module 53, for calculating outer loop adaptive parameters based on resistance and reactance; wherein the outer loop adaptive parameters are used for VSG control;

[0161] The control module 54 is used to control the target grid-type energy storage converter according to the outer loop adaptive parameters, three-phase current, three-phase voltage, active output power and reactive output power.

[0162] In a possible implementation, the calculation module 52 is specifically configured to:

[0163] Inputting the αβ-axis components corresponding to the three-phase current and the three-phase voltage into the improved composite filter respectively, to obtain a current harmonic signal of a first preset frequency and a voltage harmonic signal of a first preset frequency; wherein the improved composite filter is determined based on a second-order generalized integrator and a complex filter;

[0164] The resistance and reactance of the power grid to which the target grid-type energy storage converter belongs are calculated according to the current harmonic signal of the first preset frequency and the voltage harmonic signal of the first preset frequency.

[0165] In one possible implementation, the improved composite filter is:

[0166]

[0167] Among them, ω c is the cutoff angular frequency of the second-order generalized integrator, ω0 is the resonant angular frequency of the second-order generalized integrator, ω hc is the cutoff frequency of the composite filter, ω h1.5 is the resonant angular frequency of the composite filter.

[0168] In a possible implementation, the control module 54 is specifically configured to:

[0169] Calculate the three-phase internal potential according to the outer loop adaptive parameters, active output power and reactive output power;

[0170] Calculate the current reference values ​​on the dq axis components according to the three-phase internal potential and the three-phase voltage;

[0171] Calculate the voltage reference value on the dq axis components according to the current reference value on the dq axis components, the three-phase current and the current harmonic signal of the second preset frequency; wherein the current harmonic signal of the second preset frequency is determined based on the current harmonic signal of the first preset frequency;

[0172] The trigger signal of each switch tube in the target energy storage converter is determined according to the voltage reference value on the dq axis component to control the target grid-type energy storage converter.

[0173] In a possible implementation, the control module 54 is specifically configured to:

[0174] Input the active frequency control parameters and active output power in the outer loop adaptive parameters into the active-frequency control loop to obtain the phase of the inner potential;

[0175] Input the reactive voltage control parameters and reactive output power in the outer loop adaptive parameters into the reactive-voltage control loop to obtain the amplitude of the inner potential;

[0176] The three-phase internal potential is calculated based on the phase angle and amplitude.

[0177] In a possible implementation, the control module 54 is specifically configured to:

[0178] The current reference value on the dq axis components, the three-phase current and the current harmonic signal of the second preset frequency are input into the current inner loop to obtain the voltage reference value on the dq axis components.

[0179] In a possible implementation, the determination module 53 is specifically configured to:

[0180] Input the resistance and reactance into the VSG power outer loop control parameter calculation formula to obtain the outer loop adaptive parameters; wherein the outer loop adaptive parameters include active frequency control parameters and reactive voltage control parameters;

[0181] The active frequency control parameters include the natural oscillation frequency, cutoff frequency and equivalent damping coefficient in the active model of the improved VSG control strategy based on the reshaping of damping characteristics;

[0182] The reactive voltage control parameters include proportional coefficient and integral coefficient.

[0183] In a possible implementation, the VSG power outer loop control parameter calculation formula is:

[0184]

[0185]

[0186] Among them, ω np is the natural oscillation frequency of the active-frequency loop system, p is the relative position; ζ p is the damping ratio of the active control system; E g is the internal potential amplitude; U g is the voltage amplitude at the power supply end of the power grid; ω N is the rated angular frequency of the power grid; k f is the primary frequency modulation coefficient; J is the moment of inertia of the system; X f and X g are filter reactance and grid reactance respectively; D eq is the equivalent damping coefficient of the proposed improved VSG control strategy based on damping characteristic reshaping; ω p is the cut-off frequency; k v is the proportionality coefficient; k i is the integral coefficient; ζ q is the damping ratio; ω nq is the natural oscillation frequency; ω q is the low-pass filter cutoff frequency.

[0187] In a possible implementation, the calculation module 52 is specifically configured to:

[0188] The first coordinate transformation is applied to the three-phase current and the three-phase voltage respectively to obtain the αβ axis components corresponding to the three-phase current and the three-phase voltage;

[0189] The αβ-axis components corresponding to the three-phase current and the three-phase voltage are respectively transformed by the second coordinate transformation to obtain the dq-axis components corresponding to the three-phase current and the three-phase voltage;

[0190] The active output power and reactive output power are calculated based on the dq-axis components corresponding to the three-phase current and the three-phase voltage.

[0191] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0192] Those of ordinary skill in the art will appreciate that the templates, units, and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0193] If the module / unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the present invention implements all or part of the processes in the above-mentioned embodiment method, and can also be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium. When the computer program is executed by the processor, it can implement the steps of the control method embodiments of the above-mentioned grid-type energy storage inverter. Among them, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form. The computer-readable medium may include: any entity or device that can carry the computer program code, recording medium, U disk, mobile hard disk, disk, optical disk, computer memory, read-only memory, random access memory, electrical carrier signal, telecommunication signal and software distribution medium.

[0194] The embodiments described above are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included in the protection scope of the present invention.

Claims

1. A control method for a grid-type energy storage converter, characterized in that: include: Collect the three-phase current and three-phase voltage of the target grid-connected energy storage converter; Determine the active output power, the reactive output power, and the resistance and reactance of the power grid to which the target grid-type energy storage converter belongs according to the three-phase current and the three-phase voltage; Based on the resistance and the reactance, calculating an outer loop adaptive parameter; wherein the outer loop adaptive parameter is used for VSG control; The target grid-type energy storage converter is controlled according to the outer loop adaptive parameters, the three-phase current, the three-phase voltage, the active output power and the reactive output power.

2. The control method of the grid-type energy storage converter according to claim 1, characterized in that: The step of determining the resistance and reactance of the power grid to which the target grid-type energy storage converter belongs according to the three-phase current and the three-phase voltage includes: Inputting the αβ-axis components corresponding to the three-phase current and the three-phase voltage into an improved composite filter respectively, to obtain a current harmonic signal of a first preset frequency and a voltage harmonic signal of a first preset frequency; wherein the improved composite filter is determined based on a second-order generalized integrator and a complex filter; The resistance and reactance of the power grid to which the target grid-type energy storage converter belongs are calculated according to the current harmonic signal of the first preset frequency and the voltage harmonic signal of the first preset frequency.

3. The control method of the grid-type energy storage converter according to claim 2 is characterized in that: The improved composite filter is: Among them, ω c is the cutoff angular frequency of the second-order generalized integrator, ω0 is the resonant angular frequency of the second-order generalized integrator, ω hc is the cutoff frequency of the composite filter, ω h1.5 is the resonant angular frequency of the composite filter.

4. The control method of the grid-type energy storage converter according to claim 2 is characterized in that: The controlling of the target grid-type energy storage converter according to the outer loop adaptive parameter, the three-phase current, the three-phase voltage, the active output power and the reactive output power includes: Calculating the three-phase internal potential according to the outer loop adaptive parameter, the active output power and the reactive output power; Calculating current reference values ​​on dq axis components according to the three-phase internal potential and the three-phase voltage; Calculate the voltage reference value on the dq axis component according to the current reference value on the dq axis component, the three-phase current and the current harmonic signal of the second preset frequency; wherein the current harmonic signal of the second preset frequency is determined based on the current harmonic signal of the first preset frequency; The trigger signal of each switch tube in the target energy storage converter is determined according to the voltage reference value on the dq axis component to control the target grid-type energy storage converter.

5. The control method of the grid-type energy storage converter according to claim 4, characterized in that: The calculating the three-phase internal potential according to the outer loop adaptive parameter, the active output power and the reactive output power comprises: Inputting the active frequency control parameter and the active output power in the outer loop adaptive parameter into the active-frequency control loop to obtain the phase of the inner potential; Inputting the reactive voltage control parameter and the reactive output power in the outer loop adaptive parameter into the reactive-voltage control loop to obtain the amplitude of the inner potential; The three-phase internal potentials are calculated based on the phase angles and amplitudes.

6. The control method of the grid-type energy storage converter according to claim 4, characterized in that: The step of calculating the voltage reference value on the dq axis component according to the current reference value on the dq axis component, the three-phase current and the current harmonic signal of the second preset frequency comprises: The current reference value on the dq axis components, the three-phase current and the current harmonic signal of the second preset frequency are input into the current inner loop to obtain the voltage reference value on the dq axis components.

7. The control method of the grid-type energy storage converter according to claim 1, characterized in that: The calculating the outer loop adaptive parameter based on the resistance and the reactance includes: Inputting the resistance and the reactance into a VSG power outer loop control parameter calculation formula to obtain outer loop adaptive parameters; wherein the outer loop adaptive parameters include active frequency control parameters and reactive voltage control parameters; The active frequency control parameters include the natural oscillation frequency, cutoff frequency and equivalent damping coefficient in the active model of the improved VSG control strategy based on the reshaping of the damping characteristics; The reactive voltage control parameters include a proportional coefficient and an integral coefficient.

8. The control method of the grid-type energy storage converter according to claim 7, characterized in that: The VSG power outer loop control parameter calculation formula is: Among them, ω np is the natural oscillation frequency of the active-frequency loop system; p is the relative position of the real pole and the real part of the conjugate pole; ζ p is the damping ratio of the active control system; E s is the internal potential amplitude; U g is the voltage amplitude at the power supply end of the power grid; ω N is the rated angular frequency of the power grid; k f is the primary frequency modulation coefficient; J is the moment of inertia of the system; X f and X g are filter reactance and grid reactance respectively; D eq is the equivalent damping coefficient of the proposed improved VSG control strategy based on damping characteristic reshaping; ω p is the cut-off frequency; k v is the proportionality coefficient; k i is the integral coefficient; ζ q is the damping ratio; ω nq is the natural oscillation frequency; ω q is the low-pass filter cutoff frequency.

9. The control method of the grid-type energy storage converter according to claim 1, characterized in that: The determining the active output power and the reactive output power according to the three-phase current and the three-phase voltage comprises: Applying a first coordinate transformation to the three-phase current and the three-phase voltage respectively to obtain αβ-axis components corresponding to the three-phase current and the three-phase voltage; Applying a second coordinate transformation to the αβ-axis components corresponding to the three-phase current and the three-phase voltage respectively to obtain the dq-axis components corresponding to the three-phase current and the three-phase voltage; The active output power and the reactive output power are calculated according to the dq-axis components corresponding to the three-phase current and the three-phase voltage.

10. A control device for a grid-type energy storage converter, characterized in that: include: A collection module, used to collect the three-phase current and three-phase voltage of the target grid-connected energy storage converter; A calculation module, used to determine the active output power, the reactive output power, and the resistance and reactance of the power grid to which the target grid-type energy storage converter belongs according to the three-phase current and the three-phase voltage; A determination module, configured to calculate an outer loop adaptive parameter based on the resistance and the reactance; wherein the outer loop adaptive parameter is used for VSG control; A control module is used to control the target grid-type energy storage converter according to the outer loop adaptive parameters, the three-phase current, the three-phase voltage, the active output power and the reactive output power.

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