Master-slave control method and system of ac-dc parallel conversion module and energy storage system

Abstract

The application provides a master-slave control method and system of an AC-DC parallel variable flow module and an energy storage system, and relates to the technical field of energy storage converter control. The method is applied to a master-slave control architecture in which the DC side and the AC side of at least two variable flow modules are parallel, and comprises the following steps: a master control module generates a three-phase voltage instruction for constructing a microgrid according to a system total power instruction; the three-phase voltage instruction is converted into a DC voltage signal, and closed-loop control of a voltage loop and a current loop is performed according to the DC voltage signal; and the DC voltage signal is sent to a slave control module, so that the slave control module performs the same closed-loop control as the master control module according to the DC voltage signal, so as to make the slave variable flow module and the master variable flow module output the same three-phase voltage signal. The application can improve the control response speed under a load impact scenario, quickly eliminate the output voltage deviation between modules, and greatly improve the dynamic current sharing effect and the current sharing control response speed.

Description

Technical Field

[0001] This application relates to the field of energy storage converter control technology, and in particular to a master-slave control method, system and energy storage system for AC / DC parallel converter modules. Background Technology

[0002] In industrial manufacturing, data centers, and other scenarios, energy storage systems often need to handle impulsive loads such as motor starting and pulsed equipment. These loads are characterized by rapid and large power fluctuations. Therefore, extremely high requirements are placed on the dynamic response speed and circulating current suppression capabilities of energy storage systems.

[0003] Currently, for AC / DC parallel three-level energy storage converter systems, the main approach is a master-slave control scheme based on shared power stage or voltage reference stage. However, in existing power stage and voltage reference stage sharing schemes, the slave module needs to go through multiple stages such as drooping operation and coordinate transformation before it can respond to power command changes. The control link is long and the dynamic response is lagging. This can lead to the output voltage of the master and slave control modules being out of sync during sudden power changes in the impact load, resulting in a significant surge in dynamic circulating current and even triggering overcurrent protection. Summary of the Invention

[0004] This application provides a master-slave control method, system, and energy storage system for AC / DC parallel converter modules to solve the problem of asynchronous output voltage of master-slave control modules during sudden power surges in impulsive loads, which leads to a significant spike in dynamic circulating current and even triggers overcurrent protection.

[0005] In a first aspect, embodiments of this application provide a master-slave control method for AC / DC parallel converter modules, applied to a master-slave control architecture for at least two converter modules connected in parallel on both the DC and AC sides; the method includes: The main control module generates three-phase voltage commands for constructing the microgrid based on the total system power command; The main control module converts the three-phase voltage command into a DC voltage signal and performs closed-loop control of the voltage loop and current loop based on the DC voltage signal. The main control module sends the DC voltage signal to the slave control module, so that the slave control module performs the same closed-loop control as the main control module based on the DC voltage signal, so that the main converter module and the slave converter module output the same three-phase voltage signal.

[0006] In one possible implementation, the midpoints of the DC buses of the at least two converter modules are interconnected to form a common DC bus midpoint; the method further includes: The main control module acquires the actual common neutral point voltage of the common DC bus midpoint and calculates the common neutral point voltage deviation between the actual common neutral point voltage and the rated common neutral point voltage. The main control module determines the midpoint balance control quantity based on the common midpoint voltage deviation value; The main control module sends the midpoint balance control quantity to the slave control module, so that both the main control module and the slave control module perform midpoint voltage balance control according to the midpoint balance control quantity.

[0007] In one possible implementation, the main control module determines the midpoint balance control quantity based on the common midpoint voltage deviation value, including: The difference between the common midpoint voltage deviation value and the preset reference deviation value is used to obtain the midpoint voltage deviation adjustment amount; The midpoint voltage deviation adjustment amount is transmitted to the regulator for adjustment, and the basic midpoint adjustment amount is output. Based on the current phase power direction, the polarity of the basic midpoint adjustment amount is corrected to obtain the midpoint balance control amount.

[0008] In one possible implementation, the total system power command includes: an active power setpoint, a reactive power setpoint, a voltage setpoint, and an active power limit value; The steps by which the main control module generates three-phase voltage commands for constructing the microgrid based on the total system power command include: Obtain the actual active power feedback power, actual reactive power feedback power, and actual feedback voltage of the at least two converter modules connected in parallel; Based on the given active power value and the given active power limit value, determine the effective active power value after limiting; Based on the given effective active power and the actual active feedback power, active frequency droop control is performed to obtain the reference phase angle of the three-phase voltage. Based on the given reactive power, the actual reactive feedback power, the given voltage, and the actual feedback voltage, reactive voltage droop control is performed to obtain the reference voltage amplitude of the three-phase voltage. The three-phase voltage command is generated based on the reference phase angle and the reference voltage amplitude.

[0009] In one possible implementation, the step of performing active frequency droop control based on the given effective active power value and the actual active feedback power to obtain the reference phase angle of the three-phase voltage includes: The difference between the effective active power setpoint and the actual active power feedback is calculated to obtain the active power deviation; The active power deviation is transmitted to the active frequency droop adjustment branch and multiplied by a preset droop coefficient to generate a frequency droop adjustment component. The active power deviation is transmitted to the virtual inertia damping branch, and an inertia damping adjustment component is generated based on virtual inertia integral adjustment and damping negative feedback adjustment. The system's rated frequency, the frequency droop adjustment component, and the inertia damping adjustment component are superimposed to obtain the system's real-time operating frequency. The reference phase angle of the three-phase voltage is obtained by integrating the real-time operating frequency of the system.

[0010] In one possible implementation, the step of performing reactive voltage droop control based on the reactive power setpoint, the actual reactive feedback power, the voltage setpoint, and the actual feedback voltage to obtain the reference voltage amplitude of the three-phase voltage includes: Calculate the reactive power deviation between the given reactive power value and the actual reactive power feedback power; The reactive power deviation is transmitted to the reactive voltage droop adjustment branch, and the reactive voltage droop adjustment component is output according to the reactive voltage droop adjustment characteristics. Calculate the voltage deviation between the voltage setpoint and the actual feedback voltage; The reactive power droop adjustment component is superimposed with the voltage deviation, and then the voltage adjustment amount is generated through proportional-integral regulation. The voltage regulation amount is superimposed on the no-load reference voltage, and then the line voltage drop compensation amount is subtracted to output the reference voltage amplitude of the three-phase voltage; wherein, the line voltage drop compensation amount is obtained by multiplying the actual reactive power feedback power by the reactive power voltage drop compensation coefficient and the effective value to peak value coefficient in sequence.

[0011] In one possible implementation, the method further includes: The main control module calculates in real time the power change rate of the total output power of the at least two converter modules connected in parallel; When the power change rate is greater than the preset impact threshold, the main control module generates a feedforward compensation amount based on the power change rate. The main control module superimposes the feedforward compensation amount onto the DC voltage signal and sends the DC voltage signal with feedforward compensation to the slave control module, so that the main control module and the slave control module perform closed-loop control of the voltage loop and current loop respectively based on the DC voltage signal with feedforward compensation.

[0012] The data is simultaneously sent to the slave control module, which responds to load changes in advance through feedforward compensation, further suppressing the dynamic circulation during the impact.

[0013] In one possible implementation, the DC voltage signal includes a d-axis voltage setpoint and a q-axis voltage setpoint; The steps of the main control module performing closed-loop control of the voltage loop and current loop based on the DC voltage signal include: Obtain the actual d-axis voltage feedback value and the actual q-axis voltage feedback value output by the main converter module; Calculate the d-axis voltage deviation between the given d-axis voltage value and the actual d-axis voltage feedback value, and the q-axis voltage deviation between the given q-axis voltage value and the actual q-axis voltage feedback value; The d-axis voltage deviation and the q-axis voltage deviation are respectively adjusted by proportional-integral method to obtain the d-axis current setpoint and the q-axis current setpoint; Obtain the actual d-axis current feedback value and the actual q-axis current feedback value output by the main converter module; The d-axis current deviation between the given d-axis current value and the actual d-axis current feedback value is calculated by proportional-integral adjustment and then superimposed with the d-axis feedforward voltage to obtain the d-axis voltage control quantity. The deviation between the given q-axis current value and the actual q-axis current feedback value is calculated by proportional-integral adjustment and then superimposed with the q-axis feedforward voltage to obtain the q-axis voltage control quantity. Based on the d-axis voltage control quantity and the q-axis voltage control quantity, a PWM drive signal for the main converter module is generated to drive the main converter module to output the corresponding three-phase voltage signal.

[0014] Secondly, embodiments of this application provide a master-slave control system for AC / DC parallel converter modules, comprising: at least two converter modules and two control modules; The DC sides of the at least two converter modules are connected in parallel, and the AC sides are connected in parallel. One of the at least two converter modules is designated as the master converter module, and the remaining converter modules are designated as slave converter modules. One of the two control modules serves as the main control module and is connected to the control terminal of the main converter module, while the other control module serves as the slave control module and is connected to the control terminal of the slave converter module. The main control module and the slave control module include at least one communication link; The main control module generates a three-phase voltage command for constructing the microgrid based on the total system power command. The main control module converts the three-phase voltage command into a DC voltage signal and performs closed-loop control of the voltage loop and current loop based on the DC voltage signal. The main control module sends the DC voltage signal to the slave control module through the communication link, so that the slave control module performs the same closed-loop control as the main control module based on the DC voltage signal, so that the main converter module and the slave converter module output the same three-phase voltage signal.

[0015] Thirdly, embodiments of this application provide an energy storage system, including a memory and a processor. The memory stores a computer program that can run on the processor. When the processor executes the computer program, it implements the master-slave control method of the AC / DC parallel converter module described in the first aspect and any one of the first aspects.

[0016] This application provides a master-slave control method for AC / DC parallel converter modules. This method is based on at least two converter modules connected in parallel on both the DC and AC sides, and employs a master-slave control architecture to achieve network control. Since the master control module converts the generated three-phase voltage command into a DC voltage signal (i.e., the DC voltage signal along the d-axis and q-axis in the dq coordinate system) and directly sends it to the slave control module, the master and slave converter modules perform dual closed-loop control of voltage and current with identical voltage setpoints. This eliminates algorithmic errors introduced by the slave control module in critical node operations such as droop control and coordinate transformation, achieving complete homogeneity of the master and slave voltage closed-loop input setpoints. At the critical nodes of slave control, voltage deviations at the parallel ports of at least two converter modules are eliminated, significantly improving the suppression effect of AC fundamental current circulation. Furthermore, for impulsive load scenarios, achieving complete homogeneity of master and slave at the voltage loop setpoint layer allows the slave control module to skip droop operations and coordinate transformation stages, significantly reducing command response delay. This results in faster dynamic current suppression during load changes, making the dynamic current circulation much smaller than existing voltage reference and power level sharing schemes, achieving optimal dynamic current sharing performance.

[0017] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit this specification. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the architecture of an energy storage converter provided in one embodiment of this application; Figure 2 This is a schematic flowchart of a master-slave control method for an AC / DC parallel converter module provided in an embodiment of this application; Figure 3 This is a flowchart illustrating the master-slave control method for an AC / DC parallel converter module provided in another embodiment of this application; Figure 4 This is a schematic diagram of a master-slave collaborative control loop provided in an embodiment of this application; Figure 5This is a schematic diagram of the master-slave control system of an AC / DC parallel converter module provided in one embodiment of this application; Figure 6 This is a schematic diagram of the structure of an AC / DC parallel energy storage converter according to an embodiment of this application; Figure 7 This is a schematic diagram of the structure of an energy storage system provided in an embodiment of this application. Detailed Implementation

[0020] The present application will be described more clearly below with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the function of the present application, but do not limit the present application in any way. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present application. These all fall within the protection scope of the present application.

[0021] It should be understood that, when used in this application specification and the appended claims, the term "comprising" indicates the presence of the described features, integrals, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or a collection thereof.

[0022] It should also be understood that the term “and / or” as used in this application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0023] In the description of this application and the appended claims, the terms "first," "second," "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0024] References to "one embodiment" or "some embodiments" as described in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.

[0025] Furthermore, the term "multiple" mentioned in the embodiments of this application should be interpreted as two or more.

[0026] In industrial manufacturing, data centers, and other scenarios, energy storage systems often need to handle impulsive loads such as motor starting and pulsed equipment. These loads are characterized by rapid and large power fluctuations. Therefore, extremely high requirements are placed on the dynamic response speed and circulating current suppression capabilities of energy storage systems.

[0027] Currently, for AC / DC parallel three-level energy storage converter systems, the main approach is a master-slave control scheme based on shared power stage or voltage reference stage. However, in existing power stage and voltage reference stage sharing schemes, the slave module needs to independently go through multiple stages such as droop calculation and coordinate transformation before it can respond to power command changes. The control link is long and the dynamic response is lagging, which can lead to the output voltage of the master and slave control modules being out of sync during sudden power changes in the impact load. This can cause a significant surge in dynamic circulating current and even trigger overcurrent protection.

[0028] To address the aforementioned technical challenges, this application proposes the following technical concept: For the dual core requirements of "fast dynamic response and high circulating current suppression" under impact load scenarios, this solution proposes a master-slave network control architecture with shared voltage commands. The master control module completes all droop control and coordinate transformation calculations, directly generating a DC voltage command signal in the dq coordinate system, which is then synchronously sent to the slave control module. The slave control module directly uses the received DC voltage signal as its own voltage loop input reference, skipping all droop control and coordinate transformation calculations. This solution significantly shortens the command response link of the slave control module, effectively improving dynamic response speed. Furthermore, because the voltage input commands of the master and slave control modules are completely synchronized, algorithmic errors introduced by the slave control module in key nodes such as droop control and coordinate transformation are eliminated. This achieves complete homogeneity of the master and slave voltage closed-loop input commands, eliminating voltage deviations at the parallel ports of at least two converter modules at key control nodes, ensuring highly consistent output voltages on the AC side of at least two converter modules and more thorough AC circulating current suppression. Compared to existing shared control schemes for power stage and voltage reference stage, this application achieves the best dynamic AC current sharing effect and response speed.

[0029] First refer to Figure 1 , Figure 1 This is a schematic diagram of the architecture of an energy storage converter provided in one embodiment of this application.

[0030] like Figure 1 As shown, the energy storage converter consists of at least two converter modules. The DC sides of the at least two converter modules are connected in parallel and share the same DC power supply (DC+, DC-), and the AC sides are also connected in parallel. Furthermore, the at least two converter modules adopt a master-slave control architecture, with one converter module serving as the master converter module and the rest serving as slave converter modules (such as the first slave converter module to the Mth slave converter module).

[0031] Each converter module includes a pre-charge protection module, a DC filter module, a bus capacitor, an inverter circuit, and an AC filter module. These modules convert the DC input from the DC side into three-phase AC power via DC filtering and inversion, and then output three-phase AC voltage signals (U, V, W) after AC filtering. The pre-charge protection module consists of a pre-charge contactor and a pre-charge resistor connected in series, and then connected in parallel with the DC contactor.

[0032] It should be noted that the above architectural diagrams are shown only to facilitate understanding of the spirit and principles of this application, and the implementation of this application is not limited in any way. On the contrary, the implementation of this application can be applied to any applicable scenario.

[0033] Figure 2 This is a flowchart illustrating the master-slave control method for an AC / DC parallel converter module provided in one embodiment of this application.

[0034] like Figure 2 As shown, the method in this application embodiment may include the following steps: In step S201, the main control module generates a three-phase voltage command for constructing the microgrid based on the total system power command.

[0035] In this step, the total system power command includes the active power setpoint P. ref Reactive power setpoint Q ref Voltage setpoint U ref and global active power limit value P OL_Pos / Neg The main control module will output the system's given active power setpoint P. ref Reactive power setpoint Q ref Voltage setpoint U ref and global active power limit value P OL_Pos / Neg As the control reference for the power outer loop in the main control module, substitute it as follows: Figure 4 The active frequency droop control (Pf droop control) loop and reactive voltage droop control (QV droop control) loop shown generate a grid reference, including the reference voltage amplitude E and the reference phase angle. Then, the network reference is converted into a symmetrical three-phase reference voltage in a three-phase stationary coordinate system. This refers to the three-phase voltage command.

[0036] Among them, the global active power limit value P OL_Pos / Neg P is the active power bidirectional limiting value (positive / negative). OL_Pos P is the positive limit value for active power (corresponding to the maximum discharge active power). OL_Neg This is the negative limit value for active power (corresponding to the maximum charging active power).

[0037] In step S202, the main control module converts the three-phase voltage command into a DC voltage signal and performs closed-loop control of the voltage loop and current loop based on the DC voltage signal.

[0038] In this step, the conversion of the three-phase voltage command into a DC voltage signal can be referenced. Figure 4 The coordinate transformation process in the main control module shown involves the main control module transforming the symmetrical three-phase reference voltage in the three-phase stationary coordinate system. Input the abc / dq coordinate transformation module to obtain the reference phase angle. To synchronize the rotation angle, a Parker transformation is performed to convert the three-phase AC voltage signal in the three-phase stationary coordinate system into a DC voltage signal in the synchronously rotating dq coordinate system: d-axis voltage setpoint Udr and q-axis voltage setpoint Uqr. This DC voltage signal is then used as the input reference for the voltage loop, sequentially completing the dual closed-loop control of the voltage and current loops. Finally, the PWM drive signal for the main converter module is output via Space Vector Pulse Width Modulation (SVPWM) to drive the main converter module to output the corresponding three-phase AC voltage signal.

[0039] In step S203, the main control module sends the DC voltage signal to the slave control module, so that the slave control module performs the same closed-loop control as the main control module based on the DC voltage signal, so that the main converter module and the slave converter module output the same three-phase voltage signal.

[0040] In this step, the control module skips the active-frequency droop control, reactive-voltage droop control, and coordinate transformation processes. Its voltage loop reference depends entirely on the DC voltage signal sent by the main control module. Figure 4 As shown by the blue dashed line, the master control module shares the d-axis voltage setpoint Udr and the q-axis voltage setpoint Uqr with the slave control module. The slave control module uses Udr and Uqr sent by the master control module as the input reference of the local voltage loop, and independently performs a dual closed-loop control process of voltage closed-loop control and current closed-loop control, as well as an SVPWM modulation process, to generate PWM drive signals for the slave converter modules, so as to drive at least one slave converter module to output the corresponding three-phase AC voltage signal.

[0041] In one possible implementation, the master control module sends the DC voltage signal to the slave control module at a preset time interval, which can be a microsecond-level time interval (such as several hundred microseconds) to ensure that the slave control module can follow the master control module to complete the network construction in a timely manner, thereby improving the dynamic response speed of the system network construction control.

[0042] In this embodiment, for the AC / DC parallel + three-level topology, AC-side voltage coupling circulating current will occur. After the DC side is connected in parallel, the output voltages of multiple converter modules are strongly correlated. If the slave control module completes the network construction by following the system power command or voltage reference command sent by the master control module, the slave control module is prone to deviation from the master control module during the independent droop control and coordinate transformation process. This will result in the phase and amplitude of the output voltages of the master and slave converters still being deviated, and AC circulating current will still occur. Furthermore, for impulsive load scenarios, the control link of the slave control module independently performing multiple stages such as droop calculation and coordinate transformation is long, and the dynamic response is lagging. At the moment of sudden power change of the impulsive load, the output voltages of the master and slave control modules are not synchronized, resulting in a significant surge in dynamic circulating current. In this embodiment, the master and slave control modules use identical DC voltage signals as the reference for the voltage loop to perform subsequent voltage and current closed-loop control. This achieves complete master-slave reference unification at the voltage loop reference layer, eliminating algorithmic errors introduced by the slave control module in critical node operations such as droop control and coordinate transformation. It also ensures complete homogeneity of the master and slave voltage closed-loop input references, eliminating voltage deviations at least two parallel ports of the converter modules at critical slave control nodes, resulting in more thorough AC circulating current suppression. Furthermore, the slave control module directly uses the received DC voltage signal as its own voltage loop input reference, skipping all droop control and coordinate transformation operations. This scheme significantly reduces... The shortened command response link of the slave control module effectively improves the dynamic current sharing control response speed. Furthermore, since the voltage input of the master and slave control modules is completely synchronized, the AC output voltage of at least two converter modules is highly consistent, ensuring that the AC output power of at least two converter modules is accurately and evenly distributed. According to the law of conservation of energy, the power transmitted from the common DC bus is also balanced, suppressing the DC circulating current caused by uneven power distribution on the DC side from the power source. Compared with the shared power command scheme, the combined effect and speed of AC circulating current suppression and DC circulating current suppression are the best, which greatly improves the dynamic current sharing effect and response speed of the system under impact load scenarios.

[0043] Figure 3 This is a flowchart illustrating the master-slave control method for an AC / DC parallel converter module provided in another embodiment of this application. The method in this embodiment focuses on describing the process of the master control module performing midpoint balance loop control.

[0044] refer to Figure 1 At least two converter modules have their DC bus midpoints interconnected to form a common DC bus midpoint N.

[0045] It should be noted that in the traditional parallel energy storage converter module architecture, only the AC side is connected in parallel, and the bus midpoint voltage of a single converter module can be individually controlled by a closed-loop control. However, in the embodiment of this application, not only the AC side is connected in parallel, but the DC side is also connected in parallel. The parallel connection of both AC and DC will generate not only AC side circulating current, but also DC side circulating current. Therefore, the embodiment of this application proposes a hardware improvement, namely, the DC bus midpoints of two adjacent converter modules are connected through a neutral line relay. By closing the neutral line relay, the DC bus midpoints (O) of multiple converter modules are interconnected to form a common DC bus midpoint N. The generated DC side circulating current can be discharged through the interconnected neutral line to avoid affecting the subsequent inverter circuit and AC filter circuit. However, based on this midpoint interconnection topology, if the midpoint voltage of each converter module is still controlled separately in a closed loop, and the two control modules each collect their own midpoint voltage and independently adjust the closed loop, the two sets of midpoint voltage control quantities will interfere with each other through the interconnection midline (such as canceling each other out or superimposing each other), causing the midpoint voltage to fluctuate continuously. The upper and lower voltage divider capacitors are prone to voltage imbalance and overvoltage on one side of the capacitor. Under impact load scenarios, the midpoint potential fluctuation will be further amplified, thereby aggravating the DC circulating current problem. In severe cases, it can lead to overvoltage damage to the capacitor on one side of the bus.

[0046] Based on this, the method provided in this embodiment also includes a midpoint balance control process.

[0047] like Figure 3 As shown, the method provided in this embodiment further includes the following steps: Step S301: The main control module acquires the actual common neutral point voltage of the common DC bus midpoint and calculates the common neutral point voltage deviation value between the actual common neutral point voltage and the rated common neutral point voltage.

[0048] In this step, refer to Figure 1 Each converter module's DC bus capacitor consists of an upper capacitor C1 and a lower capacitor C2 connected in series, with a total DC voltage of U. dc =U C1 +U C2 The series connection point is the DC bus midpoint O. After the DC bus midpoints of multiple converter modules are interconnected, they form a common DC bus midpoint N. Under ideal steady-state conditions: U C1 =U C2 =U dc / 2, i.e., the rated common neutral point voltage U O =U dc / 2. The main control module acquires the actual common neutral point voltage U in real time. mid Calculate the voltage deviation at the common midpoint, ΔVbusN = U mid - U dc / 2.

[0049] In step S302, the main control module determines the midpoint balance control quantity based on the common midpoint voltage deviation value.

[0050] In one possible implementation, the main control module determines the midpoint balance control quantity based on the common midpoint voltage deviation value, including: subtracting the common midpoint voltage deviation value from a preset reference deviation value to obtain a midpoint voltage deviation adjustment quantity; transmitting the midpoint voltage deviation adjustment quantity to the regulator for adjustment and outputting a basic midpoint adjustment quantity; and correcting the polarity of the basic midpoint adjustment quantity based on the current phase power direction to obtain the midpoint balance control quantity.

[0051] Specifically, ideally, the preset reference deviation value is 0. The difference between the preset reference deviation value (0) and the common midpoint voltage deviation value ΔVbusN is used to obtain the deviation signal. This deviation signal reflects the direction of the midpoint potential deviating from the target value. The deviation signal is input to the P regulator (proportional regulator) to output the basic midpoint adjustment amount. The basic midpoint adjustment amount is input to the phase power direction adjustment module Sign(V*I) to correct the polarity of the basic midpoint adjustment amount and obtain the midpoint balance control amount. Among them, V usually refers to the phase voltage command (or actual phase voltage) and phase current (or current command) of the corresponding phase. V*I represents the instantaneous active power component of the phase (active when voltage and current are in phase, and reactive when they are orthogonal). The Sign function is to take the sign of V*I. If V*I>0, then Sign(V*I)=+1, indicating that the power flows from the DC side to the AC side and the system is in the inverter state. If V*I<0, then Sign(V*I)=-1, indicating that the power flows from the AC side to the DC side and the system is in the rectification state. In a three-level energy storage converter, the current direction (power flow direction) directly alters the polarity of the vector's influence on the midpoint potential. For example, the same vector might shift the midpoint potential in one direction during inversion but in the opposite direction during rectification. Therefore, the polarity of the dynamic base midpoint adjustment must be determined based on the sign of V*I to ensure that the midpoint adjustment is always adjusted in the direction that eliminates the deviation, regardless of the power direction. Ultimately, by correcting the polarity of the base midpoint adjustment, the midpoint balance control quantity is obtained.

[0052] In step S303, the main control module sends the midpoint balance control quantity to the slave control module, so that both the main control module and the slave control module perform midpoint voltage balance control according to the midpoint balance control quantity.

[0053] In this step, to avoid interference between the two sets of midpoint voltage correction values ​​caused by each control module independently acquiring the midpoint voltage for closed-loop regulation, thus leading to continuous fluctuations in the midpoint voltage, the slave control module in this implementation no longer performs independent midpoint balancing control on the midpoint potential of the slave converter module. Instead, it directly uses the midpoint balancing control value sent by the master control module, referencing... Figure 4 The main control module sends the midpoint balance control quantity output by the midpoint balance loop to the slave control module at preset time intervals (such as several hundred microseconds). The slave control module directly uses the midpoint balance control quantity sent by the main control module to participate in modulation and realize midpoint balance control.

[0054] In this embodiment, the process of the main control module and the slave control module balancing the midpoint voltage based on the midpoint balance control quantity is the same, including: inputting the midpoint balance control quantity to the SVPWM modulation module, superimposing the midpoint balance control quantity onto the three-phase modulation wave output by the current loop of the corresponding phase (performing an inverse dq / abc coordinate transformation on the DC voltage control quantity output by the current loop in the dq axis coordinate system to obtain the three-phase modulation voltage signal output by the current loop), and then entering the SVPWM modulation stage, changing the midpoint current by adjusting the duty cycle of the PWM drive signal to achieve dynamic balance of the midpoint potential.

[0055] In this embodiment, due to the AC / DC parallel connection + DC bus midpoint interconnection + three-level topology, not only will AC-side voltage coupling circulating current occur, but DC-side midpoint potential coupling conflict will also occur due to the DC bus midpoint interconnection (when multiple converter modules independently adjust the midpoint balance by sharing the DC bus midpoint, the control quantities will interfere with each other, leading to increased midpoint offset and uneven capacitor voltage distribution). Under impact load scenarios, the DC-side circulating current will be further aggravated. In this embodiment, by sharing the d-axis voltage setpoint Udr and the q-axis voltage setpoint Uqr, the slave control module follows the dq-axis voltage commands of the master control module, achieving complete master-slave output consistency at the voltage level, thus suppressing the problem at its source. With AC circulating current and a short control link from the control module, it offers a more direct AC current sharing effect than shared current commands under impact load scenarios, and better AC circulating current suppression and faster dynamic response than shared system-level power commands. Simultaneously, by sharing the midpoint balance control quantity, the master and slave control modules uniformly use the same set of midpoint adjustment quantities, completely resolving DC midpoint voltage coupling conflicts caused by DC bus midpoint interconnection, avoiding midpoint voltage fluctuations caused by independent adjustments, and effectively suppressing DC-side circulating current caused by midpoint potential shift. This significantly improves the overall current sharing effect on both the AC and DC sides, achieving rapid suppression of dynamic circulating current and midpoint potential stability under impact load scenarios.

[0056] In one possible implementation, the steps by which the main control module generates three-phase voltage commands for constructing the microgrid based on the total system power command include: Step 1: Obtain the actual active power feedback, actual reactive power feedback, and actual feedback voltage of the at least two converter modules connected in parallel.

[0057] In this step, the main control module collects the actual active power feedback P1 from at least two converter modules connected in parallel. fdbActual reactive power feedback Q1 fdb and actual feedback voltage U fdb .

[0058] Step 2: Determine the effective active power setpoint after limiting based on the given active power value and the given active power limit value.

[0059] In one possible implementation, the active power limiting value P OL_Pos / Neg The calculation steps include: the main control module acquires the maximum actual reactive power feedback power output from at least two converter modules connected in parallel and the rated apparent power of the entire unit; the main control module determines the active power limit value based on the maximum actual reactive power feedback power and the rated apparent power; wherein, the maximum actual reactive power feedback power acquired by the main control module is the larger of the first actual reactive power feedback power and the second actual reactive power feedback power, the first actual reactive power feedback power is acquired by the main control module itself, and the second actual reactive power feedback power is acquired from the control module and sent to the main control module.

[0060] Specifically, the main control module itself collects the first actual reactive power feedback Q1 from the parallel output of at least two converter modules. fdb The control module also collects the second actual reactive power feedback power Q2 from the parallel output of at least two converter modules. fdb And send it to the main control module, the main control module compares it with Q1 fdb and Q2 fdb The larger of the two values ​​will be taken as the maximum actual reactive power feedback power Q. fdb Based on the rated apparent power Sn and maximum Q of the whole machine fdb Determine the current remaining available capacity of the entire unit. The remaining available capacity determines the maximum upper limit of active power output, thus obtaining the active power limit value P. OL_Pos / Neg .

[0061] In this step, the global active power limit value P is used as the basis. OL_Pos / Neg For the active power given value P ref Perform amplitude limiting to obtain the effective P after amplitude limiting. ref That is, when the active power setpoint is within the active power limit range, the active power setpoint P will be... ref As an effective P ref When the active power setpoint exceeds the active power limit range, the corresponding active power limit value will be used as the effective P. ref .

[0062] In this step, the rated apparent power Sn of the entire machine and the maximum Q collected by the master and slave control modules are used. fdbCalculating the global active power limit value can prevent the total active and reactive power output of the system from exceeding the rated capacity of the whole machine, avoid overload damage to power devices, and improve operational reliability.

[0063] Step 3: Based on the given effective active power and the actual active feedback power, perform active frequency droop control to obtain the reference phase angle of the three-phase voltage.

[0064] In one possible implementation, the step of performing active frequency droop control based on the effective active power setpoint and the actual active feedback power to obtain the reference phase angle of the three-phase voltage includes: calculating the difference between the effective active power setpoint and the actual active feedback power to obtain the active power deviation; transmitting the active power deviation to the active frequency droop adjustment branch and multiplying it by a preset droop coefficient to generate a frequency droop adjustment component; transmitting the active power deviation to the virtual inertia damping branch and generating an inertia damping adjustment component based on virtual inertia integral adjustment and damping negative feedback adjustment; superimposing the system's rated frequency, the frequency droop adjustment component, and the inertia damping adjustment component to obtain the system's real-time operating frequency; and performing an integral operation on the system's real-time operating frequency to obtain the reference phase angle of the three-phase voltage.

[0065] For details, please refer to Figure 4 The active power-frequency droop control loop in the control loop of the main control module shown calculates the effective P after limiting. ref and P1 fdb The difference is used to obtain the active power deviation ΔP. The active power deviation ΔP is then input to the active frequency droop adjustment branch and the active frequency droop coefficient. K pf Multiplying them together yields the frequency droop adjustment component. ,Right now If the actual active power output > the active power setpoint, the frequency is lowered; if the actual active power output < the active power setpoint, the frequency is raised. This satisfies the drooping law that the higher the active power output, the lower the output frequency, thus achieving automatic equalization of active power among multiple parallel converter modules. Simultaneously, the active power deviation ΔP is input to the virtual inertia damping branch: ΔP passes through 1 / 2π... f N After being converted into equivalent mechanical torque deviation, it is fed into the virtual inertia integral stage. The damping coefficient D forms a negative feedback damping loop to simulate a synchronous generator. Then, after a 1 / 2π conversion, the inertia damping adjustment component is obtained. The virtual inertia adjustment is used to suppress instantaneous frequency changes, simulating the inertial buffer of a synchronous generator. The damping coefficient negative feedback is used to suppress frequency oscillations and quickly smooth out disturbances, ensuring that the frequency does not oscillate violently when switching loads on an island. The system's rated frequency is... f N Frequency droop adjustment component The real-time operating frequency of the system is obtained by superimposing the inertia damping adjustment component. f c System real-time operating frequency f c After integration by a 2π / s integrator, the result is converted into a reference phase angle for the three-phase voltage. .

[0066] In this step, by increasing the moment of inertia and damping coefficient D through virtual inertia damping adjustment, the microgrid's ability to resist load disturbances is greatly improved. The frequency will not jump drastically when the load is suddenly increased or decreased, thus improving the system's operational stability and reliability.

[0067] Step four: Based on the given reactive power, the actual reactive feedback power, the given voltage, and the actual feedback voltage, perform reactive voltage droop control to obtain the reference voltage amplitude of the three-phase voltage.

[0068] In one possible implementation, the step of performing reactive power droop control based on the reactive power setpoint, the actual reactive power feedback power, the voltage setpoint, and the actual feedback voltage to obtain the reference voltage amplitude of the three-phase voltage includes: calculating the reactive power deviation between the reactive power setpoint and the actual reactive power feedback power; transmitting the reactive power deviation to the reactive power droop adjustment branch and outputting a reactive power droop adjustment component according to the reactive power droop adjustment characteristics; calculating the voltage deviation between the voltage setpoint and the actual feedback voltage; superimposing the reactive power droop adjustment component with the voltage deviation and generating a voltage adjustment amount through proportional-integral adjustment; superimposing the voltage adjustment amount on the no-load reference voltage and then subtracting the line voltage drop compensation amount to output the reference voltage amplitude of the three-phase voltage; wherein, the line voltage drop compensation amount is obtained by multiplying the actual reactive power feedback power sequentially by the reactive power voltage drop compensation coefficient and the RMS-to-peak conversion coefficient.

[0069] For details, please refer to Figure 4 The reactive power deviation in the reactive power-voltage droop control loop of the main control module shown is calculated as follows: ; Calculate voltage deviation: The reactive power deviation Transmitted to the reactive voltage droop regulation branch, and the voltage droop coefficient ( Multiply () This yields the reactive power droop adjustment component, achieving the QV droop characteristic where the larger the reactive power, the lower the voltage amplitude, thus realizing automatic power sharing among multiple parallel converter modules; the reactive power droop adjustment component is then correlated with the voltage deviation. After superposition, the voltage is adjusted by a PI controller using proportional-integral regulation to correct the voltage error. The voltage adjustment output from the PI controller is superimposed on the no-load reference voltage E0, and then the line voltage drop compensation is subtracted to finally output the three-phase reference voltage amplitude E. The line voltage drop compensation is... ( This is the reactive power voltage drop compensation coefficient. (This is the RMS to peak value conversion factor), used to compensate for line impedance voltage drop and optimize voltage sag issues under heavy load scenarios.

[0070] Step 5: Generate the three-phase voltage command based on the reference phase angle and the reference voltage amplitude.

[0071] In this step, refer to Figure 4 The main control module uses the reference voltage amplitude E as the voltage peak value and the reference phase angle. Given the initial phase of phase a voltage, a symmetrical three-phase reference voltage (i.e., three-phase voltage command) with a phase difference of 120° electrical angle is generated in a three-phase stationary coordinate system. The expression is: u a =E* sin (θ ref ), u b =E* sin (θ ref -2π / 3), u c =E* sin (θ ref +2π / 3).

[0072] In one possible implementation, the method further includes: the main control module calculating in real time the power change rate of the total output power of the at least two converter modules in parallel; when the power change rate is greater than a preset impact threshold, the main control module generating a feedforward compensation amount based on the power change rate; the main control module superimposing the feedforward compensation amount onto the DC voltage signal, and sending the DC voltage signal with feedforward compensation to the slave control module, so that the main control module and the slave control module perform closed-loop control of the voltage loop and current loop respectively based on the DC voltage signal with feedforward compensation.

[0073] In this embodiment, the process of the main control module calculating the power change rate in real time is as follows: the main control module collects the total current and voltage output of at least two converter modules in parallel according to a preset sampling period (e.g., 10 microseconds), multiplies the two to obtain the instantaneous total active power P_total, and calculates the active power change rate dP / dt using the sliding time window method. The time window can be set according to the actual situation (e.g., 100μs), that is, dP / dt = (P_current - P_before) / 100μs, where P_current is the total active power at the current moment, and P_before is the total active power 100μs ago.

[0074] In this embodiment, the process of generating feedforward compensation based on the power change rate is as follows: The preset impact threshold can be set to 30% / ms of the system's rated power. When the absolute value of the power change rate dP / dt exceeds this threshold, it is determined to be an impact load condition, triggering feedforward compensation. The d-axis feedforward compensation is equal to the product of the power change rate and the d-axis feedforward proportional coefficient, and the q-axis feedforward compensation is equal to the product of the power change rate and the q-axis feedforward proportional coefficient. The d-axis and q-axis feedforward proportional coefficients are dimensional control parameters determined based on system circuit parameters (such as the main circuit filter inductor and voltage orientation coefficient) to compensate for the dynamic voltage drop on the filter inductor during sudden load changes, ensuring that the calculated feedforward compensation offsets the voltage fluctuations caused by the sudden load change.

[0075] For details on the calculation process of the feedforward scaling factor, please refer to relevant technical documents; it will not be explained in detail here.

[0076] In this embodiment, the DC voltage signal includes a d-axis voltage setpoint Udr and a q-axis voltage setpoint Uqr. The main control module superimposes the d-axis feedforward compensation and the q-axis feedforward compensation onto the original d-axis voltage setpoint Udr and q-axis voltage setpoint Uqr, respectively, to form a DC voltage signal with feedforward compensation (i.e., the d-axis voltage setpoint and the q-axis voltage setpoint with feedforward compensation). The main control module sends this DC voltage signal with feedforward compensation into its own voltage loop for closed-loop control, and simultaneously transmits it to the slave control module via a high-speed communication link at a period of 50μs, ensuring that both the master and slave control modules respond to the feedforward compensation simultaneously.

[0077] In this embodiment, the DC voltage signal is fed forward to respond to load surges in advance by using the power change rate as the basis for compensation. For example, if the power suddenly increases when the load is connected, the positive voltage compensation is quickly calculated and output through the feedforward compensation amount to raise the voltage loop setpoint in advance and offset the output voltage drop caused by the increase in load power. There is no need to wait for the voltage loop to detect the voltage drop and then adjust it slowly. Instead, the voltage change rate is directly predicted and compensated in advance, which greatly reduces the voltage drop depth under impact load and improves dynamic performance. Since the master and slave control modules synchronously superimpose the feedforward compensation amount, the output voltages of the two modules always remain highly synchronized, which further reduces the dynamic circulating current caused by load impact and effectively avoids the overcurrent protection being triggered by the load impact. This greatly improves the reliability and stability of the system when operating under impact load.

[0078] In one possible implementation, the DC voltage signal includes a d-axis voltage setpoint Udr and a q-axis voltage setpoint Uqr. The main control module performs closed-loop control of the voltage and current loops based on the DC voltage signal, comprising: acquiring the actual d-axis voltage feedback value and the actual q-axis voltage feedback value output by the main converter module; calculating the d-axis voltage deviation between the d-axis voltage setpoint and the actual d-axis voltage feedback value, and the q-axis voltage deviation between the q-axis voltage setpoint and the actual q-axis voltage feedback value; performing proportional-integral adjustment on the d-axis voltage deviation and the q-axis voltage deviation respectively to obtain the d-axis current setpoint and the q-axis current setpoint; acquiring the actual d-axis current feedback value output by the main converter module. The d-axis current is fed back to the given d-axis current and the actual d-axis current feedback value. The d-axis current deviation between the given d-axis current and the actual d-axis current feedback value is then calculated using proportional-integral (PI) adjustment and superimposed with the d-axis feedforward voltage to obtain the d-axis voltage control quantity. Similarly, the q-axis current deviation between the given q-axis current and the actual q-axis current feedback value is calculated using PI adjustment and superimposed with the q-axis feedforward voltage to obtain the q-axis voltage control quantity. Based on the d-axis voltage control quantity and the q-axis voltage control quantity, a PWM drive signal for the main converter module is generated to drive the main converter module to output the corresponding three-phase voltage signal.

[0079] In this embodiment, the voltage closed-loop control process includes: using the d-axis voltage setpoint Udr and q-axis voltage setpoint Uqr as voltage loop reference commands, the main control module obtains the actual d-axis voltage feedback value Ud and the actual q-axis voltage feedback value Uq after transforming the three-phase output voltage from the main converter module through the abc / dq coordinate system; and calculates the difference between the d-axis voltage setpoint Udr and the actual d-axis voltage feedback value Ud to obtain the d-axis voltage deviation value. ; d-axis voltage deviation value The data is fed into a d-axis voltage PI regulator for d-axis voltage error adjustment, and the output d-axis current setpoint idr is obtained. Similarly, the difference between the q-axis voltage setpoint Uqr and the actual q-axis voltage feedback value Uq is used to obtain the q-axis voltage deviation value. ; q-axis voltage deviation value The q-axis voltage is fed into a PI regulator to adjust the q-axis voltage error and outputs the q-axis current setpoint iqr.

[0080] In this embodiment, the current closed-loop control process includes: using the d-axis current setpoint idr and the q-axis current setpoint iqr as current loop reference commands, the main control module obtains the actual d-axis current feedback value id and the actual q-axis current feedback value iq after transforming the three-phase current output by the main converter module through the abc / dq coordinate system; the difference between the d-axis current setpoint idr and the actual d-axis current feedback value id is calculated to obtain the d-axis current deviation value. d-axis current deviation value After the current PI regulator input to the d-axis performs current error calculation, the actual d-axis voltage feedback value Ud is used as the d-axis voltage feedforward and superimposed with the output of the d-axis current PI regulator to obtain the d-axis voltage control value Udm. Similarly, the difference between the q-axis current setpoint iqr and the actual q-axis current feedback value iq is used to obtain the q-axis current deviation value. q-axis current deviation value After the current PI regulator of the q-axis performs current error calculation, the actual q-axis voltage feedback value Uq is used as the q-axis voltage feedforward and superimposed with the output of the q-axis current PI regulator to obtain the q-axis voltage control quantity Uqm.

[0081] In this embodiment, the modulation driving process includes: transforming the d-axis voltage control quantity Udm and the q-axis voltage control quantity Uqm through the dq / abc inverse coordinate transformation to obtain a three-phase modulated voltage signal (three-phase modulated wave) in the three-phase stationary coordinate system; superimposing the three-phase modulated voltage signal with the midpoint balance control quantity and then entering the SVPWM modulation stage to generate drive pulse signals (main PWM drive signals) for each power device in the inverter circuit of the main converter module, thereby controlling the main converter module to realize the power conversion and output the corresponding three-phase AC voltage signal.

[0082] It should be noted that during the network construction control process, such as Figure 4 As shown, after receiving the DC voltage signal, the slave control module executes the same voltage closed-loop, current closed-loop, and modulation processes as the main control module, outputting drive pulse signals (PWM drive signals) for each power device in the inverter circuit of the slave converter module. This controls the slave converter module to achieve power conversion and output the corresponding three-phase AC voltage signal. The specific implementation methods of the voltage closed-loop, current closed-loop, and modulation processes in the control loop of the slave control module are consistent with those of the main control module, and will not be explained again here.

[0083] It is understandable that the actual output values, such as the actual voltage and current values, used by the control module during voltage and current closed-loop control are obtained from the actual output values ​​of the converter module collected by the control module.

[0084] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0085] Figure 5 This is a schematic diagram of the master-slave control system of an AC / DC parallel converter module provided in one embodiment of this application.

[0086] like Figure 5 As shown, the system provided in this embodiment includes: at least two converter modules and two control modules; wherein, the DC sides of the at least two converter modules are connected in parallel, and the AC sides are connected in parallel; one of the at least two converter modules serves as the master converter module, and the other converter modules serve as slave converter modules; one of the two control modules serves as the master control module and is connected to the control terminal of the master converter module, and the other control module serves as the slave control module and is connected to the control terminal of the slave converter module; at least one communication link is included between the master control module and the slave control module; the master control module generates a three-phase voltage command for constructing a microgrid based on the total system power command; the master control module converts the three-phase voltage command into a DC voltage signal, and performs closed-loop control of the voltage loop and current loop based on the DC voltage signal; the master control module sends the DC voltage signal to the slave control module through the communication link, so that the slave control module performs the same closed-loop control as the master control module based on the DC voltage signal, so that the master converter module and the slave converter module output the same three-phase voltage signal.

[0087] It should be noted that, in this system embodiment, the detailed implementation of the network control by the master and slave control modules and the corresponding beneficial effects can be found in the descriptions of the relevant method embodiments above, and will not be explained in detail here.

[0088] In one possible implementation, for high-power scenarios, multiple energy storage converters may be connected in parallel on both the AC and DC sides, such as... Figure 6 As shown, it includes a master energy storage converter and at least one slave energy storage converter. The master-slave cooperative control architecture and the network control method based on the master-slave control architecture proposed in this application embodiment are also applicable to this AC / DC parallel energy storage converter scenario.

[0089] It should be noted that the detailed implementation process of the above system embodiments can be found in the relevant method embodiments section, and will not be repeated here.

[0090] Figure 7 This is a schematic diagram of the structure of an energy storage system provided in one embodiment of this application. Figure 7 As shown, the energy storage system 700 of this embodiment includes a processor 710 and a memory 720, wherein the memory 720 stores a computer program 721 that can run on the processor 710. When the processor 710 executes the computer program 721, it implements the steps in any of the above method embodiments. Alternatively, when the processor 710 executes the computer program 721, it implements the functions of each module / unit in the above system embodiments.

[0091] For example, computer program 721 may be divided into one or more modules / units, one or more of which are stored in memory 720 and executed by processor 710 to complete this application. The one or more modules / units may be a series of computer program instruction segments capable of performing a specific function, which describe the execution process of computer program 721 in the device.

[0092] Those skilled in the art will understand that Figure 7 This is merely an example of an energy storage system and does not constitute a limitation on energy storage systems. It may include more or fewer components than shown, or combine certain components, or different components, such as input / output devices, network access devices, buses, etc.

[0093] The processor 710 can be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor or any conventional processor.

[0094] The memory 720 can be an internal storage unit of the energy storage system, such as a hard disk or memory, or an external storage device, such as a plug-in hard disk, smart media card (SMC), secure digital (SD) card, flash card, etc., found in electronic devices. The memory 720 can also include both internal and external storage units of the energy storage system. The memory 720 is used to store computer programs and other programs and data required by the energy storage system. The memory 720 can also be used to temporarily store data that has been output or will be output.

[0095] For the sake of simplicity and clarity, only the above-described functional modules / units are used as examples. In practical applications, the functions described above can be assigned to different functional modules / units as needed. These modules / units can be implemented in hardware, software, or a combination of both.

[0096] An embodiment of this application also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the master-slave control method for the AC / DC parallel converter module in the above-described method embodiments.

[0097] This application also provides a computer program product, including a computer program. When the computer program is executed by a processor, it implements the master-slave control method for the AC / DC parallel converter module in the above-described method embodiments.

[0098] Computer programs include computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. Computer-readable media can include: any entity or device capable of carrying computer program code, recording media, USB flash drives, portable hard drives, magnetic disks, optical disks, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signals, telecommunication signals, and software distribution media, etc.

[0099] In the above embodiments, the descriptions of each embodiment have their own emphasis. Parts not detailed or described in a particular embodiment can be referred to in the relevant descriptions of other embodiments. Unless otherwise specified or in conflict with logic, the terminology and / or descriptions between different embodiments are consistent and can be referenced interchangeably. Technical features in different embodiments can be combined to form new embodiments based on their inherent logical relationships.

[0100] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A master-slave control method for an AC / DC parallel converter module, characterized in that, A master-slave control architecture applied to at least two converter modules connected in parallel on both the DC and AC sides; the method includes: The main control module generates three-phase voltage commands for constructing the microgrid based on the total system power command; The main control module converts the three-phase voltage command into a DC voltage signal and performs closed-loop control of the voltage loop and current loop based on the DC voltage signal. The main control module sends the DC voltage signal to the slave control module, so that the slave control module performs the same closed-loop control as the main control module based on the DC voltage signal, so that the main converter module and the slave converter module output the same three-phase voltage signal.

2. The master-slave control method for AC / DC parallel converter modules according to claim 1, characterized in that, The midpoints of the DC buses of the at least two converter modules are interconnected to form a common DC bus midpoint; the method further includes: The main control module acquires the actual common neutral point voltage of the common DC bus midpoint and calculates the common neutral point voltage deviation value between the actual common neutral point voltage and the rated common neutral point voltage. The main control module determines the midpoint balance control quantity based on the common midpoint voltage deviation value; The main control module sends the midpoint balance control quantity to the slave control module, so that both the main control module and the slave control module perform midpoint voltage balance control according to the midpoint balance control quantity.

3. The master-slave control method for AC / DC parallel converter modules according to claim 2, characterized in that, The main control module determines the midpoint balance control quantity based on the common midpoint voltage deviation value, including: The difference between the common midpoint voltage deviation value and the preset reference deviation value is used to obtain the midpoint voltage deviation adjustment amount; The midpoint voltage deviation adjustment amount is transmitted to the regulator for adjustment, and the basic midpoint adjustment amount is output. Based on the current phase power direction, the polarity of the basic midpoint adjustment amount is corrected to obtain the midpoint balance control amount.

4. The master-slave control method for AC / DC parallel converter modules according to claim 1, characterized in that, The total power command of the system includes: active power setpoint, reactive power setpoint, voltage setpoint, and active power limit value; The steps by which the main control module generates three-phase voltage commands for constructing the microgrid based on the total system power command include: Obtain the actual active power feedback power, actual reactive power feedback power, and actual feedback voltage of the at least two converter modules connected in parallel; By combining the active power limit value with the active power setpoint, the effective active power setpoint after the limit is obtained; Using the given effective active power and the actual active feedback power as inputs, the reference phase angle of the three-phase voltage is output through active frequency droop control calculation. Using the given reactive power, the actual reactive feedback power, the given voltage, and the actual feedback voltage as inputs, the reference voltage amplitude of the three-phase voltage is output through reactive voltage droop control calculation. The three-phase voltage command is generated based on the reference phase angle and the reference voltage amplitude.

5. The master-slave control method for AC / DC parallel converter modules according to claim 4, characterized in that, The step of performing active frequency droop control based on the given effective active power and the actual active feedback power to obtain the reference phase angle of the three-phase voltage includes: The difference between the effective active power setpoint and the actual active power feedback is calculated to obtain the active power deviation; The active power deviation is transmitted to the active frequency droop adjustment branch and multiplied by a preset droop coefficient to generate a frequency droop adjustment component. The active power deviation is transmitted to the virtual inertia damping branch, and an inertia damping adjustment component is generated based on virtual inertia integral adjustment and damping negative feedback adjustment. The system's rated frequency, the frequency droop adjustment component, and the inertia damping adjustment component are superimposed to obtain the system's real-time operating frequency. The reference phase angle of the three-phase voltage is obtained by integrating the real-time operating frequency of the system.

6. The master-slave control method for AC / DC parallel converter modules according to claim 4, characterized in that, The step of performing reactive voltage droop control based on the reactive power setpoint, the actual reactive power feedback power, the voltage setpoint, and the actual feedback voltage to obtain the reference voltage amplitude of the three-phase voltage includes: Calculate the reactive power deviation between the given reactive power value and the actual reactive power feedback power; The reactive power deviation is transmitted to the reactive voltage droop adjustment branch, and the reactive voltage droop adjustment component is output according to the reactive voltage droop adjustment characteristics. Calculate the voltage deviation between the given voltage value and the actual feedback voltage; The reactive power droop adjustment component is superimposed with the voltage deviation, and then the voltage adjustment amount is generated through proportional-integral regulation. The voltage regulation amount is superimposed on the no-load reference voltage, and then the line voltage drop compensation amount is subtracted to output the reference voltage amplitude of the three-phase voltage; wherein, the line voltage drop compensation amount is obtained by multiplying the actual reactive power feedback power by the reactive power voltage drop compensation coefficient and the effective value to peak value coefficient in sequence.

7. The master-slave control method for AC / DC parallel converter modules according to any one of claims 1 to 6, characterized in that, Also includes: The main control module calculates in real time the power change rate of the total output power of the at least two converter modules connected in parallel; When the power change rate is greater than the preset impact threshold, the main control module generates a feedforward compensation amount based on the power change rate. The main control module superimposes the feedforward compensation amount onto the DC voltage signal and sends the DC voltage signal with feedforward compensation to the slave control module, so that the main control module and the slave control module perform closed-loop control of the voltage loop and current loop respectively based on the DC voltage signal with feedforward compensation.

8. The master-slave control method for AC / DC parallel converter modules according to any one of claims 1 to 6, characterized in that, The DC voltage signal includes a d-axis voltage setpoint and a q-axis voltage setpoint; The steps of the main control module performing closed-loop control of the voltage loop and current loop based on the DC voltage signal include: Obtain the actual d-axis voltage feedback value and the actual q-axis voltage feedback value output by the main converter module; Calculate the d-axis voltage deviation between the given d-axis voltage value and the actual d-axis voltage feedback value, and the q-axis voltage deviation between the given q-axis voltage value and the actual q-axis voltage feedback value; The d-axis voltage deviation and the q-axis voltage deviation are respectively adjusted by proportional-integral method to obtain the d-axis current setpoint and the q-axis current setpoint; Obtain the actual d-axis current feedback value and the actual q-axis current feedback value output by the main converter module; The d-axis current deviation between the given d-axis current value and the actual d-axis current feedback value is calculated by proportional-integral adjustment and then superimposed with the d-axis feedforward voltage to obtain the d-axis voltage control quantity. The deviation between the given q-axis current value and the actual q-axis current feedback value is calculated by proportional-integral adjustment and then superimposed with the q-axis feedforward voltage to obtain the q-axis voltage control quantity. Based on the d-axis voltage control quantity and the q-axis voltage control quantity, a PWM drive signal for the main converter module is generated to drive the main converter module to output the corresponding three-phase voltage signal.

9. A master-slave control system for an AC / DC parallel converter module, characterized in that, include: At least two converter modules and two control modules; The DC sides of the at least two converter modules are connected in parallel, and the AC sides are connected in parallel. One of the at least two converter modules is designated as the master converter module, and the remaining converter modules are designated as slave converter modules. One of the two control modules serves as the main control module and is connected to the control terminal of the main converter module, while the other control module serves as the slave control module and is connected to the control terminal of the slave converter module. The main control module and the slave control module include at least one communication link; The main control module generates a three-phase voltage command for constructing the microgrid based on the total system power command. The main control module converts the three-phase voltage command into a DC voltage signal and performs closed-loop control of the voltage loop and current loop based on the DC voltage signal. The main control module sends the DC voltage signal to the slave control module through the communication link, so that the slave control module performs the same closed-loop control as the main control module based on the DC voltage signal, so that the main converter module and the slave converter module output the same three-phase voltage signal.

10. An energy storage system comprising a memory and a processor, wherein the memory stores a computer program executable on the processor, characterized in that, When the processor executes the computer program, it implements the master-slave control method for the AC / DC parallel converter module as described in any one of claims 1 to 8.

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