Off-grid multi-machine parallel control method for energy storage converter

Abstract

The invention provides an off-grid multi-machine parallel control method for an energy storage converter, and the method comprises the following steps: a host obtains a given voltage, and transmits the given voltage to each slave; the host acquires power feedback of each slave, calculates average power based on the power feedback of all the slaves, and sends the average power to each slave; the slave obtains slave first voltage compensation based on the average power and the power feedback; and the slave performs voltage loop control and current loop feed-forward calculation at least based on the given voltage and the slave first voltage compensation. According to the energy storage converter off-grid multi-machine parallel control method provided by the invention, the host issues the average power to each slave to realize power equalization, and the voltage compensation is calculated according to the difference between the average power and the power feedback to compensate to the given voltage; the dynamic responsiveness of the dynamic voltage is improved, meanwhile, the power and current balance of each energy storage converter in parallel operation is guaranteed, and dynamic and steady-state operation of multiple energy storage converters in parallel operation is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of energy storage, and in particular to an off-grid multi-machine parallel control method for an energy storage converter. Background Art

[0002] The power conversion system (PCS) can control the charging and discharging process of the battery, perform AC / DC conversion, and directly supply power to the AC load when there is no power grid. The PCS is mainly composed of a DC / AC bidirectional converter and a controller. The PCS controller receives control instructions through communication, and controls the converter to charge or discharge the battery according to the sign and size of the power instruction, thereby adjusting the active power and reactive power of the power grid.

[0003] However, the current off-grid application conditions of single-machine energy storage inverters cannot meet the capacity requirements of some application scenarios, and two or more energy storage inverters need to be operated in parallel. The parallel operation of multiple off-grid energy storage inverters needs to consider the stable start and stop of multiple machines, the circulation between multiple machines, command synchronization, load balancing and other issues. If the control is improper, the equipment cannot operate normally, and there may even be a risk of explosion. Summary of the invention

[0004] Based on this, it is necessary to provide a method for controlling multiple off-grid energy storage inverters in parallel to address the problems in the above-mentioned background technology, which can at least avoid the formation of circulating current and achieve power and current balance of multiple off-grid energy storage inverters in parallel.

[0005] To achieve the above-mentioned purpose and other related purposes, one aspect of the present application provides a method for controlling multiple off-grid energy storage converters in parallel, comprising the following steps:

[0006] The host obtains the voltage setting and sends the voltage setting to each slave;

[0007] The host obtains power feedback from each slave, calculates the average power based on the power feedback of all slaves, and sends the average power to each slave;

[0008] The slave obtains a first voltage compensation of the slave based on the average power and the power feedback;

[0009] The slave performs voltage loop control and current loop feedforward calculation based on at least a voltage reference and a first voltage compensation of the slave.

[0010] In one embodiment, the off-grid multi-machine parallel control method of the energy storage inverter also includes: the slave obtains the slave second voltage compensation based on the average power, slave voltage feedback, and slave current feedback; the slave performs voltage loop control and current loop feedforward calculation based on the voltage setting, slave first voltage compensation, and slave second voltage compensation.

[0011] In one embodiment, after the host obtains the voltage reference, the method further includes: the host performs host voltage loop control and host current loop feedforward calculation based on the voltage reference.

[0012] In one embodiment, the host performs host voltage loop control based on the voltage setting, including: obtaining the voltage setting and the host voltage feedback, and obtaining the output of the host voltage loop based on the difference between the voltage setting and the host voltage feedback, wherein the output of the host voltage loop is the input of the host current loop; wherein,

[0013] Based on the difference between the reactive power voltage setting and the host reactive power voltage feedback, the output of the host reactive power voltage loop is obtained, and the output of the host reactive power voltage loop is the input of the host reactive power current loop;

[0014] Based on the difference between the host active power voltage setting and the host active power voltage feedback, the output of the host active power voltage loop is obtained, and the output of the host active power voltage loop is the input of the host active power current loop;

[0015]

[0016] Among them, V dref Indicates reactive power voltage given, V d1 Indicates host reactive power voltage feedback, V PIout_d1 Represents the output of the host reactive power voltage loop, I dref1 Represents the input of the host reactive power current loop; V qref Indicates active power voltage given, V q1 Indicates the host active power voltage feedback, V PIout_q1 Indicates the output of the host active power voltage loop, I qref1 Indicates the input of the host active power current loop, K vp , K vi Represents the parameters of the controller.

[0017] In one embodiment, the host current loop feedforward calculation includes:

[0018] Based on the difference between the input of the host current loop and the host current feedback, as well as the voltage setting, the host modulation voltage is obtained; wherein,

[0019] Based on the difference between the input of the host reactive power current loop and the host reactive power current feedback, as well as the reactive power voltage setting, the host reactive power modulation voltage is obtained;

[0020] Based on the difference between the input of the host active power current loop and the host active power current feedback, as well as the active power voltage setting, the host active power modulation voltage is obtained;

[0021]

[0022] Among them, I dref1 Represents the input of the host reactive power current loop, I d1 Indicates host reactive power current feedback, V dref Indicates reactive power voltage reference, U dref1 Indicates the host reactive power modulation voltage; I qref1 Indicates the active power current given, I q1 Indicates the host active power current feedback, V qref Indicates active power voltage setting, U qref1 Indicates the host active power modulation voltage, K ip , K ii Represents the parameters of the controller, and Ka represents the given voltage coefficient.

[0023] In one embodiment, the slave performs a slave power loop calculation based on average power and power feedback to obtain a slave first voltage compensation, including:

[0024] Based on the difference between the average power and the power feedback, the first voltage compensation of the slave is obtained; wherein,

[0025] Calculating the first voltage compensation of the slave reactive power based on the difference between the average reactive power and the reactive power feedback;

[0026] Calculating the first voltage compensation of the slave active power based on the difference between the average active power and the active power feedback;

[0027]

[0028] Among them, Q avg Represents the average reactive power, Q act Represents reactive power feedback, V dref_Q Indicates the first voltage compensation of the slave reactive power; P avg Represents the average active power, Q act Represents active power feedback, V dref_P Indicates the first voltage compensation of slave active power; K pp , K pi Represents the parameters of the controller.

[0029] In one embodiment, the slave performs current droop calculation based on average power, slave voltage feedback, and slave current feedback to obtain a second slave voltage compensation, including:

[0030] Based on the average active power, the slave active power voltage feedback, and the slave active power current feedback, a second voltage compensation of the slave active power is obtained;

[0031]

[0032] Among them, Vref_i Indicates the second voltage compensation of the slave's active power, P avg Indicates the average active power, V q2 Indicates the voltage feedback of the slave's active power, i q2 Indicates the current feedback of the slave's active power, and Kr represents the droop coefficient.

[0033] In one embodiment, the slave performs voltage loop control based at least on the voltage reference and the slave's first voltage compensation, including:

[0034] Based on the reactive power voltage reference, the slave's first reactive power voltage compensation, and the slave's reactive power voltage feedback, obtain the output of the slave's reactive power voltage loop, and the output of the slave's reactive power voltage loop is the input of the slave's reactive power current loop;

[0035] Based on the active power voltage reference, the slave's active power voltage feedback, the slave's first active power voltage compensation, and the slave's second active power voltage compensation, obtain the output of the slave's active power voltage loop, and the output of the slave's active power voltage loop is the input of the slave's active power current loop;

[0036]

[0037] Wherein, V dref Indicates the reactive power voltage reference, V dref_Q Indicates the slave's first reactive power voltage compensation; V d2 Indicates the slave's reactive power voltage feedback, V PIout_d2 Indicates the output of the slave's reactive power voltage loop, I dref2 Indicates the input of the slave's reactive power current loop; V qref Indicates the active power voltage reference, V dref_P Indicates the slave's first active power voltage compensation, V ref_i Indicates the slave's second active power voltage compensation, V q2 Indicates the slave's active power voltage feedback, V PIout_q2 Indicates the output of the slave's active power voltage loop, I qref2 Indicates the input of the slave's active power current loop, K vp 、K vi Indicates the parameters of the controller.

[0038] In one embodiment, the slave current loop feedforward calculation includes:

[0039] Based on the difference between the input of the slave current loop and the slave current feedback, and the voltage reference, obtain the slave modulation voltage; wherein,

[0040] Based on the difference between the input of the slave reactive power current and the slave reactive power current feedback, and the reactive power voltage reference, obtain the slave reactive power modulation voltage;

[0041] Based on the difference between the input of the slave active power current and the feedback of the slave active power current, and the given active power voltage, the slave active power modulation voltage is obtained;

[0042]

[0043] Among them, I dref2 Represents the input of the slave reactive power current loop, I d2 Represents the slave reactive power current feedback, V dref Indicates reactive power voltage reference, U dref2 Represents the slave reactive power modulation voltage; I qref2 Represents the input of the slave active power current loop, I q2 Indicates the slave active power current feedback, V qref Indicates active power voltage setting, U qref2 Indicates the slave active power modulation voltage, K ip , K ii Represents the parameters of the controller, and Ka represents the given voltage coefficient.

[0044] In one embodiment, when the master and the slave are started, a voltage setting is obtained based on a black start voltage; or, when the master and the slave are started, a voltage setting is obtained based on a rated voltage.

[0045] According to the off-grid parallel control method for multiple energy storage inverters provided by the present invention, the host sends the average power to each slave to achieve power sharing, and calculates voltage compensation based on the difference between the average power and the power feedback to compensate to a given voltage, thereby improving the dynamic responsiveness of the dynamic voltage while ensuring the power and current balance of each parallel energy storage inverter, thereby achieving dynamic and steady-state operation of multiple parallel machines. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to better describe and illustrate the embodiments and / or examples of those applications disclosed herein, reference may be made to one or more drawings. The additional details or examples used to describe the drawings should not be considered as limiting the scope of any of the disclosed applications, the embodiments and / or examples currently described, and the best modes of these applications currently understood.

[0047] Figure 1 A schematic diagram of a process for starting multiple off-grid machines in parallel of an energy storage converter provided in an embodiment;

[0048] Figure 2 It is a flow chart of a method for controlling off-grid multiple machines in parallel of an energy storage converter provided in one embodiment;

[0049] Figure 3A schematic diagram of host active power voltage loop and host active power current loop control provided in an embodiment;

[0050] Figure 4 A schematic diagram of host reactive power voltage loop and host reactive power current loop control provided in one embodiment;

[0051] Figure 5 A schematic diagram of slave active power loop control provided in an embodiment;

[0052] Figure 6 A schematic diagram of a slave reactive power loop control provided in an embodiment;

[0053] Figure 7 A schematic diagram of slave current droop control provided in an embodiment;

[0054] Figure 8 A schematic diagram of controlling a slave machine active power voltage loop and a slave machine active power current loop provided in an embodiment;

[0055] Fig. 9 A schematic diagram of controlling a slave reactive power voltage loop and a slave reactive power current loop provided in an embodiment;

[0056] Fig.10 The present invention is a schematic diagram of a process for power sharing of multiple off-grid energy storage converters in parallel provided in one embodiment. DETAILED DESCRIPTION

[0057] In order to facilitate understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present application are given in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0058] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0059] The purpose of the terms used herein is only to describe specific embodiments and is not intended to be limiting of the present application. When used herein, the singular forms "one", "an" and "said / the" are also intended to include plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "consisting of" and / or "comprising", when used in this specification, determine the presence of the features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0060] It should be noted that the illustrations provided in this embodiment only illustrate the basic concept of the present application in a schematic manner. Although the illustrations only show components related to the present application and are not drawn according to the number, shape and size of components in actual implementation, the type, quantity and proportion of each component in actual implementation may be changed arbitrarily, and the component layout type may also be more complicated.

[0061] The parallel connection of multiple off-grid energy storage inverters requires consideration of issues such as stable start and stop of multiple machines, circulation between multiple machines, command synchronization, load balancing, etc. If improperly controlled, the equipment cannot operate normally and there may even be a risk of machine explosion. Therefore, it is necessary to study the control method of multiple off-grid energy storage inverters in parallel.

[0062] In one embodiment, the off-grid multi-machine parallel control system of the energy storage converter includes at least a host machine and at least one slave machine, and the host machine and the slave machine can communicate internally via CAN bus, Ethernet, etc.

[0063] In one embodiment, the off-grid parallel startup process of multiple machines of the energy storage inverter includes the following steps: based on determining that all slaves have obtained the startup instruction, the host starts; the host voltage is increased from the first current voltage to the first target voltage, and a voltage phase-locked synchronization start instruction is sent to the slave; after the slave receives the voltage phase-locked synchronization start instruction, the voltage and phase are synchronized with the first target voltage as a reference, and a synchronization completion signal is sent to the host; based on determining that all slaves have completed the synchronization of voltage and phase, the host sends a second target voltage instruction to the slave, and the host and the slave are increased from the second current voltage to the second target voltage.

[0064] In one embodiment, referring to Figure 1As shown, first, based on determining that all slaves have obtained the startup instruction, the host starts. Specifically, after the host PCS_Master obtains the startup instruction, it sends the startup instruction to each slave PCS_Slave through internal communication. After receiving the startup instruction, each slave PCS_Slave sends a confirmation signal to the host PCS_Master through internal communication. When the host PCS_Master determines that each slave PCS_Slave has received the startup instruction, the host starts a synchronous black start.

[0065] Next, the host increases the voltage from the first current voltage to the first target voltage, and sends a voltage phase-locked synchronization start instruction to the slave. Specifically, the host PCS_Master first pre-charges the DC side, closes the AC relay after completing the DC pre-charging, and linearly increases the voltage from the first current voltage to the first target voltage. After reaching the first target voltage, the target voltage is kept stable for output. Among them, the first current voltage of the startup process is generally 0V, and the first target voltage is the black start voltage (V0). The black start voltage (V0) is usually 75%~80% of the rated voltage (Vn), for example, the black start voltage is 75%, 78% or 80% of the rated voltage. The boost process from the current voltage to the black start voltage (V0) usually adopts a linear boost method with a fixed slope to keep the boost process stable. After reaching the black start voltage (V0), the host PCS_Master sends a voltage phase-locked synchronization start instruction to the slave.

[0066] Next, after receiving the voltage phase-locked synchronization start instruction, the slave synchronizes the voltage and phase with the first target voltage as a reference, and sends a synchronization completion signal to the host. Specifically, after each slave PCS_Slave receives the voltage phase-locked synchronization start instruction from the host PCS_Master, it synchronizes the voltage and phase with the AC port voltage as a reference, where the AC port voltage is the first target voltage reached by the host PCS_Master, that is, the black start voltage (V0). After completing the voltage and phase phase-locked synchronization, the slave PCS_Slave closes its own AC inverter side relay and sends a voltage and phase phase-locked synchronization completion signal to the host PCS_Master.

[0067] Next, based on determining that the slaves have completed the synchronization of voltage and phase, the host sends a second target voltage instruction to the slave, and the host and the slave are boosted from the second current voltage to the second target voltage. Specifically, when the host PCS_Master receives the completion voltage and phase lock synchronization signal from each slave PCS_Slave, indicating that each slave PCS_Slave has completed the voltage and phase lock synchronization, the host PCS_Master unifies the new second target voltage instruction below, that is, the instruction to boost to the rated voltage (Vn). The second current voltage of the host PCS_Master and each slave PCS_Slave is the first target voltage, that is, the black start voltage (V0), and the first target voltage is the rated voltage (Vn). Among them, the boost process from the black start voltage (V0) to the rated voltage (Vn) usually adopts a linear boost method with a fixed slope to keep the boost process stable. Furthermore, the boost slope from the black start voltage (V0) to the rated voltage (Vn) is consistent with the boost slope from the first current voltage (ie, 0V) to the black start voltage (V0). After reaching the rated voltage, the host PCS_Master and each slave PCS_Slave are stabilized at the rated voltage, and the off-grid multi-machine parallel startup process of the energy storage converter is completed.

[0068] The present invention provides an off-grid multi-machine parallel control method for an energy storage converter, which can be applied to the above-mentioned off-grid multi-machine parallel starting process of the energy storage converter or other off-grid multi-machine parallel control processes of the energy storage converter. Figure 2 As shown, the off-grid multi-machine parallel control method of energy storage converter includes the following steps:

[0069] Step S201: the host obtains a voltage setting and sends the voltage setting to each slave;

[0070] Step S202: the host obtains power feedback from each slave, calculates average power based on the power feedback from all slaves, and sends the average power to each slave;

[0071] Step S203: the slave obtains a first voltage compensation of the slave based on the average power and the power feedback;

[0072] Step S204: the slave performs voltage loop control and current loop feedforward calculation based at least on the voltage setting and the first voltage compensation of the slave.

[0073] First, step S201 is executed, the host obtains a voltage setting, and sends the voltage setting to each slave.

[0074] In one embodiment, the host obtains a voltage setting based on the target voltage, wherein the voltage setting is the voltage setting of the host and the slave, and the voltage setting further includes a reactive power voltage setting and an active power voltage setting in a two-phase arbitrary rotation coordinate system (dq coordinate system). For example, in the above-mentioned off-grid multi-machine parallel startup process of the energy storage converter, the first target voltage is the black start voltage (V0), and the second target voltage is the rated voltage (Vn). The host can obtain the voltage setting of the host PCS_Master and the slave PCS_Slave of the off-grid multi-machine parallel control system of the energy storage converter based on the black start voltage (V0) or the rated voltage (Vn). The voltage setting includes a reactive power voltage setting V dref and active power voltage given V qref After the host PCS_Master obtains the voltage setting in the dq coordinate system based on the target voltage, the voltage setting is sent to each slave PCS_Slave through internal communication.

[0075] In one embodiment, after the host obtains the voltage setting, it also includes the host performing host voltage loop control based on the voltage setting. The host performing host voltage loop control based on the voltage setting includes: obtaining the voltage setting and the host voltage feedback, obtaining the output of the host voltage loop based on the difference between the voltage setting and the host voltage feedback, and the output of the host voltage loop is the input of the host current loop; wherein, based on the difference between the reactive power voltage setting and the host reactive power voltage feedback, obtaining the output of the host reactive power voltage loop, and the output of the host reactive power voltage loop is the input of the host reactive power current loop; based on the difference between the host active power voltage setting and the host active power voltage feedback, obtaining the output of the host active power voltage loop, and the output of the host active power voltage loop is the input of the host active power current loop.

[0076] In one embodiment, referring to Figure 3 and Figure 4 As shown, the host starts according to the voltage-frequency (VF) mode control. After obtaining the voltage setting of the two-phase arbitrary rotating coordinate system (dq coordinate system) according to, for example, the rated voltage (Vn), the real-time voltage of the host is obtained as the host voltage feedback. The voltage setting and the voltage feedback are subtracted, and the output of the voltage loop is obtained as the input of the current loop through a proportional integral controller (PI controller). Furthermore, the host voltage loop control includes the host reactive power voltage loop control and the host active power voltage loop control. The voltage setting includes the reactive power voltage setting V dref and active power voltage given V qref , based on the host reactive power voltage feedback V d1 , Host active power voltage feedback V q1 As the inverter voltage, therefore, according to the reactive power voltage given Vdref With the host reactive power voltage feedback V d1 By making a difference, the output V of the host reactive power voltage loop can be obtained through the PI controller. PIout_d1 As the input of the host reactive power current loop I dref1 , according to the active power voltage given V qref With the host active power voltage feedback V q1 By making a difference, the output V of the host active power voltage loop can be obtained through the PI controller. PIout_q1 As the input of the host active power current loop I qref1 :

[0077] (Equation 1)

[0078] Among them, V dref Indicates reactive power voltage given, V d1 Indicates host reactive power voltage feedback, V PIout_d1 Represents the output of the host reactive power voltage loop, I dref1 Represents the input of the host reactive power current loop; V qref Indicates active power voltage given, V q1 Indicates the host active power voltage feedback, V PIout_q1 Indicates the output of the host active power voltage loop, I qref1 Indicates the input of the host active power current loop, K vp , K vi Represents the parameters of the controller.

[0079] In one embodiment, after the host obtains the voltage setting, the host also performs a host current loop feedforward calculation based on the voltage setting. The host current loop feedforward calculation includes: obtaining the host modulation voltage based on the difference between the input of the host current loop and the host current feedback, as well as the voltage setting; obtaining the host reactive power modulation voltage based on the difference between the input of the host reactive power current loop and the host reactive power current feedback, as well as the reactive power voltage setting; obtaining the host active power modulation voltage based on the difference between the input of the host active power current loop and the host active power current feedback, as well as the active power voltage setting;

[0080] In one embodiment, referring to Figure 3 and Figure 4 As shown, after the host obtains the output of the voltage loop as the input of the current loop, it obtains the real-time current of the host as the host current feedback, makes a difference based on the input of the current loop and the current feedback, and then combines the voltage setting and passes through the PI controller to obtain the host modulation voltage. Furthermore, the host current loop feedforward calculation includes the host reactive power current loop feedforward calculation and the host active power current loop feedforward calculation. The input of the current loop includes the input I of the host reactive power current loopdref1 and the input I of the host active power current loop qref1 Therefore, according to the input I of the host reactive power current loop dref1 With host reactive power current feedback I d1 The difference is then combined with the reactive power voltage given by V dref , after the PI controller, the host reactive power modulation voltage U can be obtained dref1 , according to the input I of the host active power current loop qref1 With the host active power current feedback I q1 Take the difference and combine it with the active power voltage to give V qref , through the PI controller, the host active power modulation voltage U can be obtained qref1 :

[0081] (Equation 2)

[0082] Among them, I dref1 Represents the input of the host reactive power current loop, I d1 Indicates host reactive power current feedback, V dref Indicates reactive power voltage reference, U dref1 Indicates the host reactive power modulation voltage; I qref1 Represents the input of the host active power current loop, I q1 Indicates the host active power current feedback, V qref Indicates active power voltage setting, U qref1 Indicates the host active power modulation voltage, K ip , K ii Represents the parameters of the controller, and Ka represents the given voltage coefficient.

[0083] Through the host voltage loop control and current loop feedforward calculation, the host modulation voltage is obtained, the host voltage output stability and current output stability are achieved, the response speed and stability of the off-grid parallel process are improved, and the energy storage system's ability to resist sudden loading / unloading interference is enhanced.

[0084] Then, step S202 is executed, the host obtains power feedback from each slave, calculates average power based on the power feedback from all slaves, and sends the average power to each slave.

[0085] In one embodiment, the off-grid multi-machine parallel power sharing process of the energy storage converter includes the following steps: the host sends a first average power to the slave; the slave receives and records the first average power, and sends power feedback to the host; the host obtains the power feedback of each slave, calculates the second average power based on the power feedback of the host and all slaves, and sends the second average power to the slave. The power includes reactive power and active power.

[0086] In one embodiment, referring to Fig.10 As shown, first, the host PCS_Master polls the nth slave PCS_Slave_n at regular intervals through internal communication, and sends the average power to the nth slave PCS_Slave_n. The average power includes the active average power and the reactive average power. Then, after receiving the polling information and the issued average power from the host PCS_Master, the nth slave PCS_Slave_n stores the issued average power (including the active power and the reactive power), and responds to the polling information, taking the current power as the power feedback of the nth slave PCS_Slave_n, and sending it to the host PCS_Master through internal communication. Next, the host obtains the power feedback of the nth slave PCS_Slave_n, and statistically analyzes the power feedback of all slave PCS_Slaves. When a round of polling of all slave PCS_Slaves ends, the host calculates the average value of the power feedback of the host and all slave PCS_Slaves to obtain a new average power, and repeats the above steps to send the new average power to each slave PCS_Slave.

[0087] Among them, the host calculating the average value of the power feedback of the host and all slaves includes obtaining the average active power Pavg according to the active power feedback Pi of the host and all slaves:

[0088] (Equation 3)

[0089] Wherein, Pi represents the active power feedback, and n represents the number of energy storage converters.

[0090] The host calculating the average value of the power feedback of the host and all slaves further includes obtaining the average reactive power Qavg according to the reactive power feedback Qi of the host and all slaves:

[0091] (Equation 4)

[0092] Wherein, Qi represents the reactive power feedback, and n represents the number of energy storage converters.

[0093] By enabling the host to obtain the power feedback of each slave, calculate the average power and send the average power to each slave, power sharing is achieved, the circulating current between multiple paralleled energy storage converters is eliminated, and the problem of local heating caused by the circulating current is avoided, so that the energy storage converter can operate stably for a long time.

[0094] Then step S203 is executed, and the slave obtains the first voltage compensation of the slave based on the average power and the power feedback. Further, it also includes: the slave obtains the second voltage compensation of the slave based on the average power, the voltage feedback of the slave, and the current feedback of the slave.

[0095] In one embodiment, the slave performs slave power loop calculation based on average power and power feedback to obtain a first slave voltage compensation, including: obtaining the first slave voltage compensation based on the difference between the average power and the power feedback. The first slave reactive power voltage compensation is calculated based on the difference between the average reactive power and the reactive power feedback; the first slave active power voltage compensation is calculated based on the difference between the average active power and the active power feedback.

[0096] In one embodiment, referring to Figure 5 and Figure 6 As shown, the host PCS_Master sends the average power to each slave PCS_Slave. After obtaining the average power, the slave PCS_Slave obtains the real-time power of the slave as power feedback, and subtracts the sent average power from the power feedback, and obtains the first voltage compensation, i.e., power voltage compensation, through the PI controller. Furthermore, the slave power loop calculation includes reactive power loop calculation and active power loop calculation. According to the average reactive power Q avg With reactive power feedback Q act By making a difference, the first voltage compensation V of the slave reactive power can be obtained through the PI controller. dref_Q (i.e., reactive power voltage compensation), according to the average active power P avg With active power feedback Q act By making a difference, the first voltage compensation V of the slave active power can be obtained through the PI controller. dref_P (ie, active power voltage compensation):

[0097] (Equation 5)

[0098] Among them, Q avg Represents the average reactive power, Q act Represents reactive power feedback, V dref_Q Indicates the first voltage compensation of the slave reactive power; P avg Represents the average active power, Q act Represents active power feedback, V dref_P Indicates the first voltage compensation of slave active power; K pp , K pi Represents the parameters of the controller.

[0099] In one embodiment, the slave performs current droop calculation based on average power and slave voltage feedback and slave current feedback to obtain a second voltage compensation for the slave, including: obtaining a second voltage compensation for the slave active power based on average active power and slave active power voltage feedback and slave active power current feedback.

[0100] In one embodiment, referring to Figure 7As shown, the slave device obtains the average power and the slave device voltage feedback, obtains the average current of the slave device based on the average power and the slave device voltage feedback, uses the slave device current feedback as the inverter current, subtracts the average current of the slave device from the slave device feedback current, and through a PI controller, the second voltage compensation of the slave device can be obtained, that is, the current droop voltage compensation. Specifically, the slave device obtains the average active power P avg and the active power voltage feedback V q2 of the slave device to obtain the average active current of the slave device, and uses the active power current feedback i q2 of the slave device as the inverter current. According to the difference between the average active current of the slave device and the active power feedback current i q2 of the slave device, combined with the current droop coefficient, through a PI controller, the second voltage compensation V ref_i of the active power of the slave device can be obtained:

[0101] (Equation 6)

[0102] where V ref_i represents the second voltage compensation of the active power of the slave device, P avg represents the average active power, V q2 represents the active power voltage feedback of the slave device, i q2 represents the active power current feedback of the slave device, and Kr represents the droop coefficient.

[0103] On the basis of achieving power sharing, the average current is further calculated using the average power and the voltage feedback, and current droop control is performed to achieve current balance, eliminating the circulating current between multiple parallel energy storage converters and avoiding the problem of local heating caused by the circulating current, so that the energy storage converter can operate stably for a long time.

[0104] Then, step S204 is executed. The slave device performs voltage loop control and current loop feedforward calculation based on at least the voltage reference and the first voltage compensation of the slave device. Further, the slave device performs voltage loop control and current loop feedforward calculation based on the voltage reference, the first voltage compensation of the slave device, and the second voltage compensation of the slave device.

[0105] In one embodiment, the slave device performs voltage loop control based on at least the voltage reference and the first voltage compensation of the slave device, including: obtaining the output of the reactive power voltage loop of the slave device based on the reactive power voltage reference, the first reactive power voltage compensation of the slave device, and the reactive power voltage feedback of the slave device. The output of the reactive power voltage loop of the slave device is the input of the reactive power current loop of the slave device; obtaining the output of the active power voltage loop of the slave device based on the active power voltage reference, the active power voltage feedback of the slave device, the first active power voltage compensation of the slave device, and the second active power voltage compensation of the slave device. The output of the active power voltage loop of the slave device is the input of the active power current loop of the slave device.

[0106] In one embodiment, referring to Figure 8 and Fig. 9 As shown, the slave voltage loop control includes the slave reactive power voltage loop control and the slave active power voltage loop control. In the slave reactive power voltage loop control process, only the first voltage compensation, i.e., power voltage compensation, is performed, while in the slave active power voltage loop control process, not only the first voltage compensation, i.e., power voltage compensation, but also the second voltage compensation, i.e., current droop voltage compensation, is performed. Specifically, the slave reactive power first voltage compensation V dref_Q Compensation to reactive power voltage given V dref As the compensated voltage, the slave reactive power voltage feedback V d2 As the inverter voltage, the difference between the compensated reactive power voltage and the slave reactive power voltage feedback is obtained through the PI controller to obtain the output V of the slave reactive power voltage loop. PIout_d2 , taking the output V of the slave reactive power voltage loop PIout_d2 As the input of the slave reactive power current loop I dref2 The slave active power first voltage compensation and the slave active power second voltage compensation are compensated together to the active power voltage given V qref As the compensated voltage, the slave active power voltage feedback is used as the inverter voltage. According to the difference between the compensated active power voltage and the slave active power voltage feedback, the output V of the slave active power voltage loop is obtained through the PI controller. PIout_q2 , taking the output V of the slave active power voltage loop PIout_q2 As the input of the slave active power current loop I qref2 :

[0107]

[0108] (Equation 7)

[0109] Among them, V dref Indicates reactive power voltage given, V dref_Q Indicates the first voltage compensation of the slave reactive power; V d2 Represents the slave reactive power voltage feedback, V PIout_d2 Represents the output of the slave reactive power voltage loop, I dref2 Represents the input of the slave reactive power current loop; V qref Indicates active power voltage given, V dref_P Indicates the first voltage compensation of slave active power, V ref_i Indicates the second voltage compensation of slave active power, V q2 Indicates the slave active power voltage feedback, V PIout_q2 Represents the output of the slave active power voltage loop, I qref2 Represents the input of the slave active power current loop, K vp , K vi Represents the parameters of the controller.

[0110] In one embodiment, the slave current loop feedforward calculation includes: obtaining a slave modulation voltage based on the difference between the input of the slave current loop and the slave current feedback, and a voltage setting; wherein, based on the difference between the input of the slave reactive power current and the slave reactive power current feedback, and a reactive power voltage setting, obtaining a slave reactive power modulation voltage; based on the difference between the input of the slave active power current and the slave active power current feedback, and an active power voltage setting, obtaining a slave active power modulation voltage.

[0111] In one embodiment, referring to Figure 8 and Fig. 9 As shown, after the slave obtains the output of the voltage loop as the input of the current loop, the real-time current of the slave is obtained as the slave current feedback, that is, the inverter current. The difference is made according to the input of the current loop and the slave current feedback, and then combined with the voltage setting, the slave modulation voltage is obtained through the PI controller. Further, the slave current loop feedforward calculation includes the slave reactive power current loop feedforward calculation and the slave active power current loop feedforward calculation. The input of the current loop includes the input I of the slave reactive power current loop dref2 and the input I of the slave active power current loop qref2 Therefore, according to the input I of the slave reactive power current loop dref2 With the slave reactive power current feedback I d2 The difference is then combined with the reactive power voltage given by V dref , after the PI controller, the slave reactive power modulation voltage U can be obtained dref2 , according to the input I of the slave active power current loop qref2 and slave active power current I q2 Feedback is used to make a difference, and then combined with the active power voltage to give V qref , after the PI controller, the slave active power modulation voltage U can be obtained qref2 :

[0112] (Equation 8)

[0113] Among them, I dref2 Represents the input of the slave reactive power current loop, I d2 Represents the slave reactive power current feedback, V dref Indicates reactive power voltage reference, U dref2 Represents the slave reactive power modulation voltage; I qref2 Represents the input of the slave active power current loop, I q2 Indicates the slave active power current feedback, V qref Indicates active power voltage setting, U qref2 Indicates the slave active power modulation voltage, K ip , Kii Represents the parameters of the controller, and Ka represents the given voltage coefficient.

[0114] In one embodiment, during the off-grid multi-machine parallel control process of the energy storage converter, when the load is suddenly added or unloaded, the deviation of the output voltage of the energy storage converter from the rated voltage within 100ms is not greater than ±10% of the rated voltage. Specifically, when the load is 20%, the resistive load resistance is 5.59Ω (215kW*2*0.2=86kW), when the load is 100%, the resistive load resistance is 1.115Ω, when the load is suddenly added from 20% to 100%, the maximum transient voltage deviation in 100ms is 54.8V, at which time the 10% rated voltage is 69V, and the maximum transient voltage deviation in 100ms is less than 10% of the rated voltage; when the load is suddenly unloaded from 100% to 20%, the maximum transient voltage deviation in 100ms is 48.4V, at which time the 10% rated voltage is 69V, and the maximum transient voltage deviation in 100ms is less than 10% of the rated voltage.

[0115] The voltage compensation is calculated based on the active power, reactive power, and current droop, and the voltage setting is compensated to adjust the voltage setting so that the multiple energy storage converters in parallel can achieve power and current balance. For example, when the output power of one of the multiple energy storage converters in parallel is greater than that of the other converters, the voltage compensation is a negative value to reduce the setting of the current loop so that the multiple energy storage converters in parallel can achieve power and current balance.

[0116] Through the slave voltage loop control and current loop feedforward calculation, the slave modulation voltage is obtained, the slave voltage output stability and current output stability are achieved, the response speed and stability of the off-grid parallel process are improved, and the energy storage system's ability to resist sudden loading / unloading interference is enhanced.

[0117] Based on the same inventive concept, the embodiment of the present application also provides an energy storage system for implementing the above-mentioned off-grid multi-machine parallel control method of energy storage converters. The energy storage system includes multiple parallel energy storage converters and a controller, and the multiple energy storage converters include a host and at least one slave. The controller includes: at least one processor; and a memory connected to the at least one processor in communication; wherein the memory stores a computer program executable by at least one processor, and the computer program is executed by at least one processor so that at least one processor can execute the above-mentioned embodiment of the energy storage converter off-grid multi-machine parallel control method, which is used to realize the synchronous parallel operation of multiple energy storage converters of the energy storage system in off-grid mode.

[0118] In an exemplary embodiment, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by a processor, the steps of the off-grid multi-machine parallel control method of the energy storage converter in the above embodiment are implemented.

[0119] According to the off-grid multi-machine parallel control method of energy storage inverter provided by the present invention, the host sends the average power to each slave to realize power sharing, and calculates the power voltage compensation according to the difference between the average power and the power feedback. At the same time, the average current is calculated by using the average power and the voltage feedback, and the current droop voltage compensation is calculated according to the difference between the average current and the current feedback, which is used to compensate for the given voltage, thereby improving the dynamic responsiveness of the dynamic voltage while ensuring the power and current balance of each parallel energy storage inverter, thereby realizing the dynamic and steady-state operation of multiple parallel machines.

[0120] Please note that the above embodiments are for illustrative purposes only and are not intended to limit the present application.

[0121] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0122] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0123] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the patent application. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application.

Claims

1. A method for controlling off-grid multi-machine parallel connection of energy storage converters, characterized in that: The steps include: The host obtains a voltage setting and sends the voltage setting to each slave; The host obtains power feedback from each slave, calculates average power based on the power feedback from all slaves, and sends the average power to each slave; The slave obtains a first voltage compensation of the slave based on the average power and the power feedback; The slave performs voltage loop control and current loop feedforward calculation based at least on the voltage setting and the slave first voltage compensation.

2. The off-grid multi-machine parallel control method of energy storage converter according to claim 1 is characterized in that: Also includes: The slave obtains a second slave voltage compensation based on the average power, slave voltage feedback, and slave current feedback; The slave performs voltage loop control and current loop feedforward calculation based on the voltage setting, the slave first voltage compensation and the slave second voltage compensation.

3. The off-grid multi-machine parallel control method of energy storage converter according to claim 1, characterized in that: After the host obtains the voltage setting, the method further includes: The host performs host voltage loop control and host current loop feedforward calculation based on the voltage setting.

4. The off-grid multi-machine parallel control method of energy storage converter according to claim 3 is characterized in that: The host performs host voltage loop control based on the voltage setting, including: The voltage setting and the host voltage feedback are obtained, and based on the difference between the voltage setting and the host voltage feedback, the output of the host voltage loop is obtained, and the output of the host voltage loop is the input of the host current loop; wherein, Based on the difference between the reactive power voltage setting and the host reactive power voltage feedback, the output of the host reactive power voltage loop is obtained, and the output of the host reactive power voltage loop is the input of the host reactive power current loop; Based on the difference between the host active power voltage setting and the host active power voltage feedback, the output of the host active power voltage loop is obtained, and the output of the host active power voltage loop is the input of the host active power current loop; Among them, V dref Indicates reactive power voltage given, V d1 Indicates host reactive power voltage feedback, V PIout_d1 Represents the output of the host reactive power voltage loop, I dref1 Represents the input of the host reactive power current loop; V qref Indicates active power voltage given, V q1 Indicates the host active power voltage feedback, V PIout_q1 Indicates the output of the host active power voltage loop, I qref1 Indicates the input of the host active power current loop, K vp , K vi Represents the parameters of the controller.

5. The off-grid multi-machine parallel control method of energy storage converter according to claim 4 is characterized in that: The host current loop feedforward calculation includes: Based on the difference between the input of the host current loop and the host current feedback, and the voltage setting, the host modulation voltage is obtained; wherein, Based on the difference between the input of the host reactive power current loop and the host reactive power current feedback, as well as the reactive power voltage setting, the host reactive power modulation voltage is obtained; Based on the difference between the input of the host active power current loop and the host active power current feedback, as well as the active power voltage setting, the host active power modulation voltage is obtained; Among them, I dref1 Represents the input of the host reactive power current loop, I d1 Indicates host reactive power current feedback, V dref Indicates reactive power voltage reference, U dref1 Indicates the host reactive power modulation voltage; I qref1 Represents the input of the host active power current loop, I q1 Indicates the host active power current feedback, V qref Indicates active power voltage setting, U qref1 Indicates the host active power modulation voltage; K ip , K ii Represents the parameters of the controller, and Ka represents the given voltage coefficient.

6. The off-grid multi-machine parallel control method of energy storage converter according to claim 1, characterized in that: The slave performs slave power loop calculation based on the average power and the power feedback to obtain a first slave voltage compensation, including: Based on the difference between the average power and the power feedback, a first voltage compensation of the slave is obtained; wherein, Calculating the first voltage compensation of the slave reactive power based on the difference between the average reactive power and the reactive power feedback; Calculating the first voltage compensation of the slave active power based on the difference between the average active power and the active power feedback; Among them, Q avg Represents the average reactive power, Q act Represents reactive power feedback, V dref_Q Indicates the first voltage compensation of the slave reactive power; P avg Represents the average active power, Q act Represents active power feedback, V dref_P Indicates the first voltage compensation of slave active power; K pp , K pi Represents the parameters of the controller.

7. The off-grid multi-machine parallel control method of energy storage converter according to claim 2, characterized in that: The slave performs current droop calculation based on the average power and slave voltage feedback and slave current feedback to obtain a second slave voltage compensation, including: Based on the average active power, the slave active power voltage feedback, and the slave active power current feedback, a second voltage compensation of the slave active power is obtained; Among them, V ref_i Indicates the second voltage compensation of slave active power, P avg Represents the average active power, V q2 Indicates the active power voltage feedback of the slave, i q2 It represents the active power current feedback of the slave machine, and Kr represents the droop coefficient.

8. The off-grid multi-machine parallel control method of energy storage converter according to claim 7, characterized in that: The slave performs voltage loop control based at least on the voltage setting and the first voltage compensation of the slave, including: Based on the reactive power voltage setting, the slave reactive power first voltage compensation, and the slave reactive power voltage feedback, the output of the slave reactive power voltage loop is obtained, and the output of the slave reactive power voltage loop is the input of the slave reactive power current loop; Based on the given active power voltage, the slave active power voltage feedback, the slave active power first voltage compensation, and the slave active power second voltage compensation, the output of the slave active power voltage loop is obtained, and the output of the slave active power voltage loop is the input of the slave active power current loop; Among them, V dref Indicates reactive power voltage given, V dref_Q Indicates the first voltage compensation of the slave reactive power; V d2 Represents the slave reactive power voltage feedback, V PIout_d2 Represents the output of the slave reactive power voltage loop, I dref2 Represents the input of the slave reactive power current loop; V qref Indicates active power voltage given, V dref_P Indicates the first voltage compensation of slave active power, V ref_i Indicates the second voltage compensation of slave active power, V q2 Indicates the slave active power voltage feedback, V PIout_q2 Represents the output of the slave active power voltage loop, I qref2 Represents the input of the slave active power current loop, K vp , K vi Represents the parameters of the controller.

9. The off-grid multi-machine parallel control method of energy storage converter according to claim 8, characterized in that: The slave current loop feedforward calculation includes: Based on the difference between the input of the slave current loop and the slave current feedback, as well as the voltage setting, the slave modulation voltage is obtained; wherein, Based on the difference between the input of the slave reactive power current and the feedback of the slave reactive power current, and the given reactive power voltage, the slave reactive power modulation voltage is obtained; Based on the difference between the input of the slave active power current and the feedback of the slave active power current, and the given active power voltage, the slave active power modulation voltage is obtained; Among them, I dref2 Represents the input of the slave reactive power current loop, I d2 Represents the slave reactive power current feedback, V dref Indicates reactive power voltage reference, U dref2 Represents the slave reactive power modulation voltage; I qref2 Represents the input of the slave active power current loop, I q2 Indicates the slave active power current feedback, V qref Indicates active power voltage setting, U qref2 Indicates the slave active power modulation voltage, K ip , K ii Represents the parameters of the controller, and Ka represents the given voltage coefficient.

10. The off-grid multi-machine parallel control method of energy storage converter according to claim 1, characterized in that: When the host and the slave are started, the voltage setting is obtained based on a black start voltage; or, when the host and the slave are started, the voltage setting is obtained based on a rated voltage.

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