Current sharing control method and device and storage medium

Abstract

The invention provides a current sharing control method and device and a storage medium, and relates to the technical field of current sharing control. The current sharing control method is applied to any energy storage converter in an energy storage converter parallel system, and the energy storage converters are connected through a data bus. According to the current-sharing control method, a first current parameter corresponding to the current-sharing control method is determined by obtaining and through an output current, an output phase angle and an inverter voltage sampling value of the current-sharing control method. And then the current-sharing compensation amount is determined according to the first current parameter and second current parameters corresponding to the other energy storage converters. And then determining a current inner ring reference value according to the output phase angle, the inversion voltage sampling value and the current-sharing compensation amount. And determining a driving signal according to the current inner ring reference value and the inverter voltage sampling value so as to drive the energy storage converter to execute current sharing control. On the basis of not changing the hardware cost of the system, the dynamic current sharing response speed of the slave is prevented from being limited by the communication rate of the data bus, and the dynamic performance of the energy storage converter parallel system is improved.

Description

Technical Field

[0001] The present invention relates to the field of current sharing control technology, and in particular to a current sharing control method, device and storage medium. Background Art

[0002] When the energy storage inverter operates in an isolated island in an independent AC microgrid, it can provide stable voltage and frequency for the load and other distributed power sources, while improving the consumption capacity of renewable energy. In the prior art, multiple energy storage inverters are usually used to form an energy storage inverter parallel system, and on the basis of the energy storage inverter parallel system, a master-slave control method is adopted to achieve flexible configuration of the capacity of the independent AC microgrid system and other distributed power sources, such as refined management between battery units.

[0003] In the prior art, there are two main methods for current sharing control of energy storage converters: the first method is a parallel current sharing method based on a hardware current sharing bus, for example, a dedicated current sharing bus hardware circuit is designed to sample the deviation signal between the local output current of the converter and the average output current of the parallel system, and the deviation sampling signal is sent to the sampling port of the digital signal processor, so that the output is adjusted according to the current deviation signal by the digital signal processor, thereby realizing parallel current sharing control. The second method is a parallel current sharing method controlled by the slave current source, for example, when the energy storage converter host performs off-grid constant voltage and constant frequency control with rated voltage and rated frequency as the control target, and the energy storage converter host broadcasts the output of the off-grid voltage outer loop (i.e., the current reference given by the off-grid current inner loop) to all slaves through the data bus (Controller Area Network, CAN), the slave uses the current reference given by the host current inner loop as the control target value, performs constant current control, thereby realizing parallel current sharing control.

[0004] However, the above-mentioned solution 1 requires a separate design of a hardware current-sharing busbar. Although it has good dynamic performance, it increases the system hardware cost and control complexity. When the hardware current-sharing busbar is abnormal, the energy storage inverter system will not work properly, thereby increasing the failure rate of the energy storage inverter system. Solution 2 requires data broadcasting based on the original data bus between the host and the slave. However, the slave obtains the output of the off-grid voltage outer loop from the host as the target value. When executing constant current control, the dynamic current-sharing response speed of the slave is limited by the data bus communication rate, and the data bus communication rate is usually much lower than the execution speed of the energy storage inverter control loop. Therefore, the dynamic performance corresponding to Solution 2 is poor. When the load suddenly changes, it may not be able to respond to the host's current command in time, resulting in mainstream overcurrent, triggering overload protection, and making the energy storage inverter parallel system unable to work properly.

[0005] Based on this, a current sharing control scheme is urgently needed to avoid the dynamic current sharing response speed of the slave being limited by the data bus communication rate without changing the system hardware cost, so as to improve the dynamic performance of the energy storage inverter parallel system. Summary of the invention

[0006] The present invention provides a current sharing control method, device and storage medium, which can avoid the dynamic current sharing response speed of the slave being limited by the data bus communication rate without changing the system hardware cost, and improve the dynamic performance of the energy storage inverter parallel system.

[0007] The present invention can be implemented like this:

[0008] On the one hand, the present invention provides a current sharing control method, which is applied to any energy storage converter in an energy storage converter parallel system composed of multiple energy storage converters, wherein each of the energy storage converters is connected via a data bus, and each of the energy storage converters performs constant voltage and constant frequency control, and the current sharing control method comprises the following steps:

[0009] Obtaining its own output current, output phase angle and inverter voltage sampling value, and determining its own corresponding first current parameter according to the output current and the output phase angle;

[0010] Acquire the second current parameters corresponding to the remaining energy storage converters through the data bus;

[0011] Determine the current sharing compensation amount according to the first current parameter and the second current parameter; wherein the first current parameter and the second current parameter both include the active component and the reactive component of the output current of the energy storage converter;

[0012] Determine its own current inner loop reference value according to the output phase angle, the inverter voltage sampling value and the current sharing compensation amount;

[0013] A driving signal is determined according to the current inner loop reference value and the inverter voltage sampling value to drive the energy storage converter to perform current sharing control.

[0014] Preferably, when the first current parameter includes a first active component and a first reactive component; when the second current parameter includes a second active component and a second reactive component, the step of determining the current sharing compensation amount according to the first current parameter and the second current parameter includes:

[0015] Determine the active component deviation corresponding to itself according to the first active component and each of the second active components; determine the reactive component deviation corresponding to itself according to the first reactive component and each of the second reactive components;

[0016] The current sharing compensation amount is determined according to the active component deviation and the reactive component deviation.

[0017] Preferably, taking the kth energy storage converter as an example, the calculation formula of the current sharing compensation amount satisfies:

[0018]

[0019] Among them, G s (s) is the transfer function corresponding to the current-sharing proportional-integral controller, K p_s K is the proportional coefficient corresponding to the current-sharing proportional-integral controller. i_s is the integral coefficient corresponding to the current-sharing proportional-integral controller, is the active current sharing compensation amount, is the reactive current sharing compensation, θ is the output phase angle, I share is the current sharing compensation, I outdk is the output current I corresponding to the kth energy storage converter outk The active component of I, i.e., the first active component; outqk is the output current I corresponding to the kth energy storage converter outk The reactive component, i.e., the first reactive component; I outd_avg is the mean value of the active power component of the system; I outq_avg is the mean value of the reactive component of the system.

[0020] Preferably, taking the kth energy storage converter as an example, the calculation formulas of the first active component and the first reactive component satisfy:

[0021]

[0022] Among them, I outdk is the output current I corresponding to the kth energy storage converter outk The active component of I, i.e., the first active component; outqk is the output current I corresponding to the kth energy storage converter outk The reactive component, i.e. the first reactive component; e -j is the phase shift operator of -90°; θ is the output phase angle.

[0023] Preferably, the step of determining the active component deviation corresponding to itself according to the first active component and each of the second active components; and determining the reactive component deviation corresponding to itself according to the first active component and each of the second active components comprises:

[0024] Determining a system active component of the energy storage converter parallel system according to the first active component and each of the second active components;

[0025] Determining a system reactive component of the energy storage converter parallel system according to the first reactive component and each of the second reactive components;

[0026] According to the number of the energy storage converters in the energy storage converter parallel system, the system active component and the system reactive component, respectively determine the system active component mean value and the system reactive component mean value;

[0027] Determining the active component deviation corresponding to itself according to the system active component mean and the first active component;

[0028] The reactive component deviation corresponding to the system is determined according to the reactive component mean value of the system and the first reactive component.

[0029] Preferably, the calculation formulas for the mean value of the system active component and the mean value of the system reactive component respectively satisfy:

[0030]

[0031] Among them, I outd_avg is the mean value of the active power component of the system; I outq_avg is the mean value of the reactive component of the system; n is the total number of energy storage converters; I outdk is the output current I corresponding to the kth energy storage converter outk Active component of I outqk is the output current I corresponding to the kth energy storage converter outk The reactive component.

[0032] Preferably, the step of determining its own current inner loop reference value according to the output phase angle, the inverter voltage sampling value and the current sharing compensation amount comprises:

[0033] Obtain its own inverter voltage amplitude;

[0034] Determine a voltage outer loop reference value using the inverter voltage amplitude and the output phase angle;

[0035] Determining an initial current inner loop reference value according to the voltage outer loop reference value and the inverter voltage sampling value;

[0036] A current inner loop reference value is determined according to the current sharing compensation amount and the initial current inner loop reference value.

[0037] Preferably, the step of determining the driving signal according to the current inner loop reference value and the inverter voltage sampling value comprises:

[0038] Determining an initial modulation reference signal according to a current inner loop reference value;

[0039] Determining a modulation reference signal according to the inverter voltage sampling value and the current inner loop reference value;

[0040] A driving signal is determined according to a preset carrier signal and the modulation reference signal.

[0041] Preferably, the expression of the modulation reference signal satisfies:

[0042]

[0043] Among them, V mod_ref is the modulation reference signal; G i (s) is the transfer function corresponding to the current inner loop controller; G v (s) is the transfer function corresponding to the voltage outer loop controller; V inv is the inverter voltage sampling value; is the voltage outer loop reference value; is the current inner loop reference value; I inu is the inductor current sampling value; I s h are is the current sharing compensation amount.

[0044] In a second aspect, the present invention further provides a current sharing control device, which is applied to any energy storage converter in a parallel energy storage converter system consisting of a plurality of energy storage converters, comprising:

[0045] A first current parameter acquisition module, used to acquire its own output current, output phase angle and inverter voltage sampling value, and determine its own corresponding first current parameter according to the output current and the output phase angle;

[0046] A second current parameter acquisition module, used to acquire the second current parameters corresponding to the remaining energy storage converters;

[0047] A current sharing compensation amount determination module, used to determine the current sharing compensation amount according to the first current parameter and the second current parameter; wherein the first current parameter and the second current parameter both include the active component and the reactive component of the output current of the energy storage converter;

[0048] A current inner loop reference value determination module, used to determine its own current inner loop reference value according to the output phase angle, the inverter voltage sampling value and the current sharing compensation amount;

[0049] The drive signal determination module is used to determine the drive signal according to the current inner loop reference value and the inverter voltage sampling value, so as to drive the energy storage converter to perform current sharing control.

[0050] In a third aspect, the present invention further provides a storage medium having a computer program stored thereon, wherein when the computer program is executed by a processor, the current sharing control method as described in any one of the above-mentioned first aspects is implemented.

[0051] The beneficial effects of the embodiments of the present invention include, for example:

[0052] A current sharing control method, device and storage medium, wherein the current sharing control method is applied to any energy storage converter in an energy storage converter parallel system composed of multiple energy storage converters, and each of the energy storage converters is connected through a data bus. The current sharing control method includes the following steps: obtaining its own output current, output phase angle and inverter voltage sampling value, and determining its own corresponding first current parameter based on the output current and output phase angle. Obtaining the second current parameter corresponding to each of the remaining energy storage converters. Then determining the current sharing compensation amount based on the first current parameter and the second current parameter. Determining its own current inner loop reference value based on the output phase angle, the inverter voltage sampling value and the current sharing compensation amount. Determining a drive signal based on the current inner loop reference value and the inverter voltage sampling value to drive the energy storage converter to perform current sharing control. The present invention avoids the limitation of the dynamic current sharing response speed of the slave machine by the data bus communication rate on the basis of not changing the system hardware cost, and improves the dynamic performance of the energy storage converter parallel system. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0054] Figure 1 A flow chart of the steps of a current balancing control method provided by the present invention;

[0055] Figure 2 A system structure diagram of the energy storage converter parallel system provided by the present invention;

[0056] Figure 3 A control flow chart of the current sharing control method provided by the present invention;

[0057] Figure 4 is a step-by-step flow chart of step 203 of the present invention;

[0058] Figure 5 is a step-by-step flow chart of step 301 in the present invention;

[0059] Figure 6 is a step-by-step flow chart of step 204 of the present invention;

[0060] Figure 7 is a step-by-step flow chart of step 205 of the present invention;

[0061] Figure 8 A schematic diagram of the structure of a current balancing control system provided by the present invention;

[0062] Fig. 9is a rendering of a current sharing control method in one embodiment of the present invention;

[0063] Fig.10 The output voltage and current waveform diagram of each single-phase energy storage converter in a microgrid at full load steady state in one embodiment of the present invention;

[0064] Fig.11 The waveform diagram of the output voltage and current of each single-phase energy storage converter when it is dynamically suddenly put into operation in a microgrid in one embodiment of the present invention;

[0065] Fig.12 The following is a waveform diagram of the output voltage and current of each single-phase energy storage converter when it is dynamically unloaded in a microgrid in one embodiment of the present invention.

[0066] Icons: 100- energy storage converter parallel system; 101- energy storage converter stand-alone; 102- energy storage battery; 103- energy storage converter; 104- control unit; 600- current sharing control device; 601- first current parameter acquisition module; 602- second current parameter acquisition module; 603- current sharing compensation amount determination module; 604- current inner loop reference value determination module; 605- drive signal determination module. DETAILED DESCRIPTION

[0067] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0068] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0069] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0070] In the description of the present invention, it should be noted that the terms “first”, “second”, etc., if used, are only used to distinguish the descriptions and cannot be understood as indicating or implying relative importance.

[0071] It should be noted that, in the absence of conflict, the features in the embodiments of the present invention may be combined with each other.

[0072] Combined with the background technology, in the prior art, the energy storage converter parallel system often adopts two schemes in the process of executing current sharing control. Scheme 1 is a parallel current sharing scheme based on a hardware current sharing bus. For example, a dedicated current sharing bus hardware circuit is designed to sample the deviation between the local output current of the energy storage converter and the average output current of the parallel system to obtain a current deviation signal, and the above current deviation signal is sent to the sampling port of the digital signal processor to adjust the output according to the current deviation signal through the digital signal processor, thereby realizing parallel current sharing control. Scheme 2 is a parallel current sharing scheme based on slave current source control. For example, when the energy storage converter host performs off-grid constant voltage and constant frequency control with rated voltage and rated frequency as the control target, and the energy storage converter host broadcasts the output of the off-grid voltage outer loop to all slaves through the data bus, the slave uses the current reference given by the host current inner loop as the control target value, performs constant current control, thereby realizing parallel current sharing control, however, the above two schemes cannot avoid the dynamic current sharing response speed of the slave being limited by the data bus communication rate without changing the system hardware cost.

[0073] Based on the above considerations, this embodiment provides a current sharing control solution to improve the dynamic performance of the energy storage converter parallel system without changing the system hardware cost.

[0074] The above current sharing control scheme will be described in detail below.

[0075] Please refer to Figure 1 On the one hand, this embodiment provides a current sharing control method, which is applied to any energy storage converter in an energy storage converter parallel system composed of multiple energy storage converters, each energy storage converter is connected through a data bus, and each energy storage converter performs constant voltage and constant frequency control. In a possible implementation method, please refer to Figure 2 , Figure 2 The system structure diagram of the energy storage converter parallel system in this embodiment is shown. The energy storage converter parallel system includes an energy storage converter parallel system 100 composed of multiple energy storage converter units 101, and the energy storage converter unit 101 includes energy storage batteries 102 and energy storage converters (Power Conversion System, PCS) 103 connected in sequence. The AC output end of each energy storage converter 103 is connected to the AC bus through a relay; the AC bus is connected to the microgrid load after passing through an industrial frequency transformer.

[0076] The energy storage converter parallel system 100 further includes a control unit 104, which is used to send a control signal to each energy storage converter 103 to control the start and stop of the energy storage converter 103. When one energy storage converter is selected as a host and the other energy storage converters are slaves, the control unit 104 can be connected to the host to broadcast control signals or control instructions to each slave through the host. Each energy storage converter 103 is connected through a data bus.

[0077] In this embodiment, each energy storage converter of the energy storage converter parallel system performs constant voltage and constant frequency control, so that its off-grid dynamic response speed is mainly determined by the off-grid voltage outer loop and off-grid current inner loop corresponding to each energy storage converter. The current sharing control based on the data bus is only used to perform the function of output current sharing regulation. Therefore, by using the current sharing control method provided in this embodiment, the rate corresponding to the data bus does not affect the dynamic performance of the energy storage converter parallel system.

[0078] Please continue to refer to Figure 1 In this embodiment, the current sharing control method includes the following steps 201 to 205.

[0079] Step 201: Obtain its own output current, output phase angle and inverter voltage sampling value, and determine its own corresponding first current parameter according to the current and output phase angle.

[0080] Step 202: Obtain second current parameters corresponding to the remaining energy storage converters.

[0081] Step 203: Determine the current sharing compensation amount according to the first current parameter and the second current parameter.

[0082] The first current parameter and the second current parameter both include the active component and the reactive component of the output current of the energy storage converter.

[0083] Step 204: Determine its own current inner loop reference value according to the output phase angle, the inverter voltage sampling value and the current sharing compensation amount.

[0084] Step 205 : Determine a driving signal according to the current inner loop reference value and the inverter voltage sampling value to drive the energy storage converter to perform current sharing control.

[0085] Please refer to Figure 3 , Figure 3A current sharing control block diagram in this embodiment is shown. The current sharing control method provided in this embodiment is a dual-loop parallel current sharing control algorithm based on the instantaneous active component of the output current and the instantaneous reactive component of the output current corresponding to the energy storage inverter. Specifically, the current sharing compensation amount corresponding to the energy storage inverter itself is determined according to the instantaneous active component of the output current and the instantaneous reactive component of the output current corresponding to the energy storage inverter. Then, the current sharing compensation amount is used as the current sharing adjustment amount of the off-grid current inner loop to be superimposed on the off-grid current reference given corresponding to the energy storage inverter itself to achieve current sharing control.

[0086] Please refer to Figure 3 The energy storage converter includes an inverter full-bridge circuit (PCS inverter full-bridge circuit) and an inverter output filter circuit (PCS output filter circuit) connected in sequence. The inverter output filter circuit is connected to the rear-end load through a relay. In this embodiment, the inverter output filter circuit is used to provide an inverter voltage sampling value V inv , inductor current sampling value I inv Among them, I out is the output current of the energy storage converter. This embodiment is mainly based on the output current I out The corresponding active component and reactive component construct the current sharing compensation amount I share .

[0087] When the inverter filter includes a first inductor L1, a second inductor L2 and a filter capacitor C, the first end of the first inductor L1 is connected to the first end of the second inductor L2 and the first end of the filter capacitor C; the second end of the first inductor L1 and the second end of the filter capacitor C are connected to the output end of the inverter full-bridge module; the second end of the second inductor L2 is connected to the relay. The above inverter voltage sampling value V inv It is the voltage across the filter capacitor in the inverter filter; the above inductor current sampling value I inv That is, the current output by the first inductor L1 in the inverter filter.

[0088] Figure 3 The control block diagram of the current sharing compensation amount in this embodiment is shown. The current sharing compensation amount can be obtained by the output current I of the energy storage converter. out Determine the reactive component I of the output current by Park transformation outqk and active component I outdk The reactive component of the output current I outqk As an example, the reactive current sharing compensation amount can be determined by the reactive current sharing loop controller and the limiter in sequence. Similarly, the reactive component of the output current I outdk As an example, the reactive current sharing compensation amount can be determined by the active current sharing loop controller and the limiter in turn. Finally, the Park transformation is used to calculate the reactive current sharing compensation amount. Active current compensation Determine the final current sharing compensation value I share .

[0089] In a possible implementation method, in this embodiment, the step 201 of obtaining the output current, output phase angle and inverter voltage sampling value of the self, and determining the first current parameter corresponding to the self according to the output current and output phase angle is specifically:

[0090] Taking the kth energy storage converter as an example, the output current I corresponding to itself can be sampled by the AD converter outk , output phase angle θ, and then use the output phase angle θ to adjust the output current I outk Perform Park coordinate transformation to determine the active component I of the output current corresponding to the kth energy storage converter outdk and reactive component I outqk , the active component of the above output current I outdk The reactive component of the output current I outqk That is, as the first active component and the first reactive component in this embodiment, the first active component and the first reactive component can be expressed as:

[0091]

[0092] Among them, I outdk is the output current I corresponding to the kth energy storage converter outk The active component of I, i.e., the first active component; outqk is the output current I corresponding to the kth energy storage converter outk The reactive component, i.e. the first reactive component; e -j is the phase shift operator of -90°; θ is the output phase angle.

[0093] Similarly, the remaining energy storage converters in the energy storage parallel system will use the above method to determine their corresponding second active component and second reactive component, and then transmit the second active component and second reactive component corresponding to each of the remaining energy storage converters to the kth energy storage converter through the data bus.

[0094] After the kth energy storage converter receives the above-mentioned second active components and second reactive components, it determines the current sharing compensation amount corresponding to any energy storage converter in combination with the first active component and the first reactive component corresponding to itself.

[0095] In one possible implementation method, in this embodiment, please refer to Figure 4 When the first current parameter includes a first active component and a first reactive component; when the second current parameter includes a second active component and a second reactive component, step 203 of determining the current sharing compensation amount according to the first current parameter and the second current parameter includes steps 301-302.

[0096] Step 301: Determine the active component deviation corresponding to itself according to the first active component and each second active component; determine the reactive component deviation corresponding to itself according to the first reactive component and each second reactive component.

[0097] Step 302: Determine the current sharing compensation amount according to the active component deviation and the reactive component deviation.

[0098] In this embodiment, please refer to Figure 5 , a method for determining the active component deviation and the reactive component deviation, that is, step 301 includes steps 3011-3015.

[0099] Step 3011: determine the system active component of the energy storage converter parallel system according to the first active component and each second active component.

[0100] Step 3012: Determine the system reactive component of the energy storage converter parallel system based on the first reactive component and each second reactive component.

[0101] Step 3013: Determine the mean value of the system active component and the mean value of the system reactive component according to the number of energy storage converters in the energy storage converter parallel system, the system active component and the system reactive component.

[0102] Step 3014: Determine the active component deviation corresponding to the system active component according to the mean value of the system active component and the first active component.

[0103] Step 3015: Determine the reactive component deviation corresponding to the system reactive component according to the mean value of the system reactive component and the first reactive component.

[0104] In this embodiment, the mean value of the system active component and the mean value of the system reactive component are respectively expressed as:

[0105]

[0106] Among them, I outd_avg is the mean value of the active power component of the system; I outq_avg is the mean value of the reactive component of the system; n is the total number of energy storage converters; I outdk is the output current I corresponding to the kth energy storage converter outk Active component of I outqk is the output current I corresponding to the kth energy storage converter outk The reactive component of the kth energy storage converter is expressed as: The reactive component deviation B is expressed as:

[0107] In this embodiment, the active current sharing loop controller can be used to determine the active current sharing output value according to the active component deviation, and then pass through the limiter to obtain the first current sharing compensation amount. Similarly, the reactive current sharing loop controller can be used to determine the reactive current sharing output value according to the reactive component deviation, and then pass through the limiter to obtain the second current sharing compensation amount. Finally, the first current sharing compensation amount and the second current sharing compensation amount are subjected to Park coordinate inverse transformation to obtain the final current sharing compensation amount.

[0108] Taking the kth energy storage converter as an example, the above current sharing compensation value I share It can be expressed as:

[0109]

[0110] Among them, G s (s) is the transfer function corresponding to the current-sharing proportional-integral controller, K p_s K is the proportional coefficient corresponding to the current-sharing proportional-integral controller. i_s is the integral coefficient corresponding to the current-sharing proportional-integral controller, is the active current sharing compensation amount, is the reactive current sharing compensation, θ is the output phase angle, I share is the current sharing compensation, I outdk is the output current I corresponding to the kth energy storage converter outk The active component of I, i.e., the first active component; outqk is the output current I corresponding to the kth energy storage converter outk The reactive component, i.e., the first reactive component; I outd_avg is the mean value of the active power component of the system; I outq_avg is the mean value of the reactive component of the system.

[0111] In this embodiment, each energy storage converter performs constant voltage and constant frequency control, and the above-mentioned current sharing compensation amount is used as the current sharing adjustment amount of the off-grid current inner loop, which is superimposed on the off-grid current reference given by each energy storage converter, thereby realizing current sharing control.

[0112] In this embodiment, please refer to Figure 6 Step 204 of determining its own current inner loop reference value according to the output phase angle, the inverter voltage sampling value and the current sharing compensation amount includes steps 401 to 404.

[0113] Step 401: Obtain its own inverter voltage amplitude.

[0114] Step 402: Determine a voltage outer loop reference value using the inverter voltage amplitude and the output phase angle.

[0115] Step 403: determine an initial current inner loop reference value according to the voltage outer loop reference value and the inverter voltage sampling value.

[0116] Step 404 : determining a current inner loop reference value according to the current sharing compensation amount and the initial current inner loop reference value.

[0117] Continue to refer Figure 3 In a possible implementation method, the above constant voltage and constant frequency control method can be: each energy storage converter in the energy storage converter parallel system takes the corresponding rated voltage as the target voltage, takes the corresponding rated frequency as the target power, and forms its own inverter voltage from zero with a preset slope to determine its own inverter voltage amplitude. At the same time, in order to achieve accurate synchronization of the power frequency phase of the master and slave machines, an energy storage converter can be selected as the master, and the remaining energy storage converters can be slaves. When the phase angle corresponding to the current master is zero, that is, θ=0, the CAN communication bus is immediately used to synchronize the phase angle synchronization signal to each slave with the highest priority. After the slave receives the phase angle synchronization signal, each slave sets its own phase angle to zero. The above master-slave power frequency synchronization is executed synchronously with the above off-grid constant voltage and frequency control.

[0118] Based on the above constant voltage and constant frequency control method, in this embodiment, the steps of determining the voltage outer loop reference value by using the inverter voltage amplitude and the output phase angle can be:

[0119] The energy storage converter can be based on its rated frequency F rate With rated operating frequency f s The angular frequency ω0 is determined by the ratio of the angular frequency ω0 (or the execution frequency of the control algorithm in the energy storage converter). Then, the phase angle θ is determined according to the angular frequency ω0 during the working cycle, and the range of the phase angle θ satisfies: (0, 2π). The phase angle θ can be subjected to a sine operation to obtain the processed phase angle sin(θ), and then the processed phase angle sin(θ) is superimposed on the slowly changing inverter voltage V A_ref and will be used as the reference value of the voltage outer loop controller, that is, the voltage outer loop reference value Among them, V A_ref is the amplitude corresponding to the slowly changing inverter voltage. In this process, the amplitude of the inverter voltage slowly changes from zero to the target amplitude at a fixed slope to avoid voltage step in the voltage outer loop control process, resulting in overshoot and impact on the back-end inverter filter. In this embodiment, the rated voltage V rate As the target, determine the preset slope. At the same time, considering the soft start waiting time, it can be 10s time interval from 0 to the rated voltage V rate Determine a preset slope, which satisfies: (Vrate / 10s)-(Vrate / 0.02s). In this embodiment, the preferred preset slope is (Vrate / 1s).

[0120] Determine the reference value of the voltage outer loop controller, that is, the voltage outer loop reference value After that, the inverter voltage sampling value V inv , determine the inverter voltage sampling value V inv With the voltage outer loop reference value The difference between the voltage and current is used to determine the initial current inner loop reference value. The initial current inner loop reference value satisfy: In this embodiment, the voltage outer loop controller is a proportional-integral controller, and its corresponding transfer function is expressed as: Among them, K p_v is the voltage outer loop proportional coefficient, K i_v is the voltage outer loop integral coefficient.

[0121] In this embodiment, please continue to refer to Figure 3 , the above current compensation amount I share Added to the initial current inner loop reference value Get the initial output value of the current inner loop controller, and then determine the initial output value and the inductor current sampling value I inv The difference between the values ​​of φ and φ is calculated to obtain the final input value of the current inner loop controller, that is, the current inner loop reference value described in this embodiment, which is expressed as:

[0122] In this embodiment, please refer to Figure 7 , step 205 of determining the driving signal according to the current inner loop reference value and the inverter voltage sampling value includes steps 501 to 503.

[0123] Step 501: Determine an initial modulation reference signal according to a current inner loop reference value.

[0124] Step 502: Determine a modulation reference signal according to the inverter voltage sampling value and the current inner loop reference value.

[0125] Step 503: Determine a driving signal according to a preset carrier signal and the modulation reference signal.

[0126] Similarly, please refer to Figure 3 In this embodiment, the current inner loop controller G i (s) to obtain an initial modulation reference signal, which is expressed as: In this embodiment, the current inner loop controller is a proportional integral controller, and the transfer function corresponding to the current inner loop controller is: Among them, K p_i is the voltage outer loop proportional coefficient, K i_i is the voltage outer loop integral coefficient.

[0127] In a possible implementation, in order to speed up the response speed of the control system and enhance the dynamic performance, the current inner loop controller G i The output value of (s) is superimposed with the inverter voltage sampling value V inv , that is, superimposing the sampled value feedforward to obtain the initial modulation reference signal. In this embodiment, the modulation reference signal V mod_eef It can be expressed as:

[0128] Please continue to refer to Figure 3 In this embodiment, the final modulation reference signal V mod_ref After that, the final modulated reference signal is modulated by a preset modulation ratio to modulate the transmission reference signal. In this embodiment, the expression of the modulated transmission reference signal is: Among them, V pwm_ref is the amplitude of the modulation reference signal, V Tri is the amplitude of the preset carrier signal, V bus is the DC bus voltage sampling value, is the modulation ratio, V mod_ref is the final modulation reference signal.

[0129] Then the modulated wave reference signal enters the PWM modulator to be modulated by the preset carrier signal inside the PWM modulator to generate a drive signal, thereby driving the energy storage converter to achieve off-grid constant voltage and constant frequency control. In this embodiment, the preset carrier signal can be an amplitude of V Tri , frequency is f s The triangular carrier.

[0130] In summary, the present invention provides a current sharing control method, which is applied to any energy storage converter in an energy storage converter parallel system composed of multiple energy storage converters, and each of the energy storage converters is connected by a data bus. The current sharing control method includes the following steps: obtaining its own output current, output phase angle and inverter voltage sampling value, and determining its own corresponding first current parameter based on the output current and output phase angle. Obtaining the second current parameter corresponding to each of the remaining energy storage converters. Then determining the current sharing compensation amount based on the first current parameter and the second current parameter. Determine its own current inner loop reference value based on the output phase angle, the inverter voltage sampling value and the current sharing compensation amount. Determine the drive signal based on the current inner loop reference value and the inverter voltage sampling value to drive the energy storage converter to perform current sharing control. The present invention avoids the limitation of the dynamic current sharing response speed of the slave by the data bus communication rate on the basis of not changing the system hardware cost, and improves the dynamic performance of the energy storage converter parallel system.

[0131] Second, please refer to Figure 8 The present invention further provides a current sharing control device 600, comprising:

[0132] The first current parameter acquisition module 601 is used to acquire its own output current, output phase angle and inverter voltage sampling value, and determine its own corresponding first current parameter according to the current and output phase angle.

[0133] The second current parameter acquisition module 602 is used to acquire the second current parameters corresponding to the remaining energy storage converters.

[0134] The current sharing compensation amount determination module 603 is used to determine the current sharing compensation amount according to the first current parameter and the second current parameter; wherein the first current parameter and the second current parameter both include the active component and the reactive component of the output current of the energy storage converter.

[0135] The current inner loop reference value determination module 604 is used to determine its own current inner loop reference value according to the output phase angle, the inverter voltage sampling value and the current sharing compensation amount.

[0136] The driving signal determination module 605 is used to determine the driving signal according to the current inner loop reference value and the inverter voltage sampling value, so as to drive the energy storage converter to perform current sharing control.

[0137] A current balancing control device provided in this embodiment includes all the technical means and technical effects of the current balancing control method described in the first aspect above, that is, it can avoid the dynamic current balancing response speed of the slave machine being limited by the data bus communication rate without changing the system hardware cost, thereby improving the dynamic performance of the energy storage inverter parallel system, which will not be repeated here.

[0138] In a third aspect, the present invention further provides a storage medium having a computer program stored thereon, and when the computer program is executed by a processor, the current sharing control method as described in any one of the first aspects above is implemented.

[0139] This embodiment provides a storage medium on which a computer program is stored. The computer program is executed by a processor to implement all the technical means of the current sharing control method described in the first aspect above, and achieves the following technical effects: without changing the system hardware cost, the dynamic current sharing response speed of the slave machine is avoided from being limited by the data bus communication rate, thereby improving the dynamic performance of the energy storage inverter parallel system.

[0140] This embodiment also provides a comparative experiment, please refer to Figures 9 to 12 , the above-mentioned figure shows the effect diagram of the current sharing control method in this embodiment. This embodiment uses multiple single-phase energy storage converters controlled by master and slave to construct an energy storage converter parallel system, wherein the rated output power of each single-phase energy storage converter is 2000W, the rated voltage is 230V, the rated frequency is 50Hz, and the rated current is 8.7A, wherein A is the voltage waveform corresponding to the load, B is the output current waveform corresponding to the master, and C is the output current waveform corresponding to any slave.

[0141] You can continue to refer to Fig. 9 In this embodiment, the energy storage converter parallel system is as follows Figure 2 Under the structure shown, according to Figure 1 The steps of the current sharing control method shown in the figure perform current sharing control, and each energy storage converter completes the closing of the relay near the zero point of the AC voltage, and the closing time difference of the relays corresponding to the master and the slave is within 2ms. After the soft start with load is completed, the energy storage converter corresponding to the master and the slave divides the total power to twice its rated power, and after the power is stable during the soft start with load, there is no overcurrent, overload or power fluctuation of a single energy storage converter.

[0142] Please refer to Fig.10 , Fig.10 The output voltage and current waveforms of each single-phase energy storage converter unit at full load steady state in the microgrid are shown. In the figure, the error of the output current of each single-phase energy storage converter unit in steady state is less than one percent of the rated current (1% rated current). It can be seen from the output waveforms in the figure that the total harmonic voltage distortion (THDU) meets the set conditions and the output waveform is relatively stable.

[0143] Please refer to Fig.11 , Fig.12 , Fig.11 , Fig.12 The output voltage and current waveforms of each single-phase energy storage converter are shown respectively when it is dynamically added or unloaded in the microgrid. Fig.11 , Fig.12 It can be seen that when the load changes dynamically, the current sharing effect corresponding to each single-phase energy storage converter in the energy storage converter parallel system is good, the output voltage overshoot is very small, and the dynamic performance corresponding to the energy storage converter parallel system is excellent.

[0144] Based on this experiment, it can be seen that the current sharing control method provided in this embodiment can avoid the dynamic current sharing response speed of the slave being limited by the data bus communication rate without changing the system hardware cost, thereby improving the dynamic performance of the energy storage converter parallel system.

[0145] In summary, the present invention provides a current sharing control method, device and storage medium, wherein the current sharing control method is applied to any energy storage converter in an energy storage converter parallel system composed of multiple energy storage converters, and each energy storage converter is connected through a data bus. The current sharing control method includes the following steps: obtaining its own output current, output phase angle and inverter voltage sampling value, and determining the first current parameter corresponding to itself according to the output current and output phase angle. Obtain the second current parameter corresponding to each of the remaining energy storage converters. Then determine the current sharing compensation amount according to the first current parameter and the second current parameter. Determine its own current inner loop reference value according to the output phase angle, the inverter voltage sampling value and the current sharing compensation amount. Determine the drive signal according to the current inner loop reference value and the inverter voltage sampling value to drive the energy storage converter to perform current sharing control. On the basis of not changing the system hardware cost, avoid the dynamic current sharing response speed of the slave being limited by the data bus communication rate, and improve the dynamic performance of the energy storage converter parallel system.

[0146] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A current sharing control method, applied to any energy storage converter in an energy storage converter parallel system composed of multiple energy storage converters, wherein each of the energy storage converters is connected via a data bus, and each of the energy storage converters performs constant voltage and constant frequency control, characterized in that: The current sharing control method comprises the following steps: Obtaining its own output current, output phase angle and inverter voltage sampling value, and determining its own corresponding first current parameter according to the output current and the output phase angle; Acquire the second current parameters corresponding to the remaining energy storage converters through the data bus; Determine the current sharing compensation amount according to the first current parameter and the second current parameter; wherein the first current parameter and the second current parameter both include the active component and the reactive component of the output current of the energy storage converter; Determine its own current inner loop reference value according to the output phase angle, the inverter voltage sampling value and the current sharing compensation amount; A driving signal is determined according to the current inner loop reference value and the inverter voltage sampling value to drive the energy storage converter to perform current sharing control.

2. The current sharing control method according to claim 1, characterized in that: When the first current parameter includes a first active component and a first reactive component; when the second current parameter includes a second active component and a second reactive component, the step of determining the current sharing compensation amount according to the first current parameter and the second current parameter includes: Determine the active component deviation corresponding to itself according to the first active component and each of the second active components; determine the reactive component deviation corresponding to itself according to the first reactive component and each of the second reactive components; The current sharing compensation amount is determined according to the active component deviation and the reactive component deviation.

3. The current sharing control method according to claim 1 or 2, characterized in that: Taking the kth energy storage converter as an example, the calculation formula of the current sharing compensation amount satisfies: Among them, G s (s) is the transfer function corresponding to the current-sharing proportional-integral controller, K p_s K is the proportional coefficient corresponding to the current-sharing proportional-integral controller. i_s is the integral coefficient corresponding to the current-sharing proportional-integral controller, is the active current sharing compensation amount, is the reactive current sharing compensation, θ is the output phase angle, I share is the current sharing compensation, I outdk is the output current I corresponding to the kth energy storage converter outk The active component of I, i.e., the first active component; outqk is the output current I corresponding to the kth energy storage converter outk The reactive component, i.e., the first reactive component; I outd_avg is the mean value of the active power component of the system; I outq_avg is the mean value of the reactive component of the system.

4. The current sharing control method according to claim 2, characterized in that: Taking the kth energy storage converter as an example, the calculation formulas of the first active component and the first reactive component satisfy: Among them, I outdk is the output current I corresponding to the kth energy storage converter outk The active component of I, i.e., the first active component; outqk is the output current I corresponding to the kth energy storage converter outk The reactive component, i.e. the first reactive component; e -j is the phase shift operator of -90°; θ is the output phase angle.

5. The current sharing control method according to claim 2, characterized in that: The step of determining the active component deviation corresponding to itself according to the first active component and each of the second active components; and determining the reactive component deviation corresponding to itself according to the first active component and each of the second active components comprises: Determining a system active component of the energy storage converter parallel system according to the first active component and each of the second active components; Determining a system reactive component of the energy storage converter parallel system according to the first reactive component and each of the second reactive components; According to the number of the energy storage converters in the energy storage converter parallel system, the system active component and the system reactive component, respectively determine the system active component mean value and the system reactive component mean value; Determining the active component deviation corresponding to itself according to the system active component mean and the first active component; The reactive component deviation corresponding to the system is determined according to the reactive component mean value of the system and the first reactive component.

6. The current sharing control method according to claim 5, characterized in that: The calculation formulas for the mean value of the active component of the system and the mean value of the reactive component of the system satisfy: Among them, I outd_avg is the mean value of the active power component of the system; I outq_avg is the mean value of the reactive component of the system; n is the total number of energy storage converters; I outdk is the output current I corresponding to the kth energy storage converter outk Active component of I outqk is the output current I corresponding to the kth energy storage converter outk The reactive component.

7. The current sharing control method according to claim 1, characterized in that: The step of determining its own current inner loop reference value according to the output phase angle, the inverter voltage sampling value and the current sharing compensation amount comprises: Obtain its own inverter voltage amplitude; Determine a voltage outer loop reference value using the inverter voltage amplitude and the output phase angle; Determining an initial current inner loop reference value according to the voltage outer loop reference value and the inverter voltage sampling value; A current inner loop reference value is determined according to the current sharing compensation amount and the initial current inner loop reference value.

8. The current sharing control method according to claim 1 or 7, characterized in that: The step of determining the driving signal according to the current inner loop reference value and the inverter voltage sampling value comprises: Determining an initial modulation reference signal according to a current inner loop reference value; Determining a modulation reference signal according to the inverter voltage sampling value and the current inner loop reference value; A driving signal is determined according to a preset carrier signal and the modulation reference signal.

9. The current sharing control method according to claim 8, characterized in that: The expression of the modulation reference signal satisfies: Among them, V mod_ref is the modulation reference signal; G i (s) is the transfer function corresponding to the current inner loop controller; G v (s) is the transfer function corresponding to the voltage outer loop controller; V inv is the inverter voltage sampling value; is the voltage outer loop reference value; is the current inner loop reference value; I inv is the inductor current sampling value; I share is the current sharing compensation amount.

10. A current sharing control device, applied to any energy storage converter in a parallel energy storage converter system consisting of multiple energy storage converters, characterized in that: include: A first current parameter acquisition module, used to acquire its own output current, output phase angle and inverter voltage sampling value, and determine its own corresponding first current parameter according to the output current and the output phase angle; A second current parameter acquisition module, used to acquire the second current parameters corresponding to the remaining energy storage converters; A current sharing compensation amount determination module, used to determine the current sharing compensation amount according to the first current parameter and the second current parameter; wherein the first current parameter and the second current parameter both include the active component and the reactive component of the output current of the energy storage converter; A current inner loop reference value determination module, used to determine its own current inner loop reference value according to the output phase angle, the inverter voltage sampling value and the current sharing compensation amount; The drive signal determination module is used to determine the drive signal according to the current inner loop reference value and the inverter voltage sampling value, so as to drive the energy storage converter to perform current sharing control.

11. A storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the current sharing control method according to any one of claims 1 to 9 is implemented.

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