Energy direct control type control method and system of cascade three-level converter

Abstract

The application discloses an energy direct control type control method and system of a cascade three-level converter, and is applied to the technical field of the cascade three-level converter, and the method comprises the following steps: obtaining target operation requirements of a target power system, and determining sub-operation requirements of each three-level converter; determining energy requirements of each three-level converter; determining first converter parameters of the three-level converter corresponding to voltage energy requirements, wherein the first converter parameters are obtained from a direct-current voltage deviation of the three-level converter, and the direct-current voltage deviation is obtained from corresponding sub-operation requirements and real-time operation data; determining second converter parameters of the three-level converter corresponding to power energy requirements; and controlling each three-level converter to execute a target control scheme obtained from the first converter parameters and the second converter parameters. The energy direct control type control method of the cascade three-level converter provided by the application can meet actual regulation requirements of a power system, and guarantees safe and stable operation of the power system.

Description

Technical Field

[0001] This invention relates to the field of cascaded three-level converter technology, and in particular to a direct energy control method and system for cascaded three-level converters. Background Technology

[0002] During the operation of a power system, by properly controlling a cascaded three-level converter, alternating current can be converted into direct current of a selected level, which is beneficial to the safe and stable operation of the power system.

[0003] However, existing control methods are based solely on voltage, such as generating control strategies with the DC-side voltage remaining constant as the single control objective. This approach cannot be adjusted in real time according to grid dispatch requirements or operating conditions, making it difficult for the power system to respond to power system fluctuations in a timely manner. Consequently, the generated control strategies cannot meet the actual regulation needs of the power system, ultimately affecting the safe and stable operation of the power system. Summary of the Invention

[0004] This invention provides a direct energy control method and system for cascaded three-level converters to solve the technical problem that existing control methods are relatively simple and cannot meet the actual regulation needs of power systems, thereby achieving the effect of meeting the actual regulation needs of power systems and ensuring the safe and stable operation of power systems.

[0005] To address the aforementioned technical problems, this invention provides a direct energy control method and system for cascaded three-level converters, the method comprising: The target operating requirements of the target power system and the real-time operating data of each three-level converter in the target power system are obtained, and the sub-operating requirements of each three-level converter are determined based on the target operating requirements and the real-time operating data. Determine the energy requirements for each of the three-level converters, wherein the energy requirements include voltage energy requirements and power energy requirements; The first converter parameter corresponding to the voltage energy demand of the three-level converter is determined. The first converter parameter is obtained by the DC voltage deviation of the three-level converter. The DC voltage deviation is obtained by the corresponding sub-operational demand and the real-time operation data. The second converter parameter corresponding to the power energy demand of the three-level converter is determined. The second converter parameter is obtained from the active power deviation of the three-level converter. The active power deviation is obtained from the corresponding sub-operational demand and the real-time operation data. Each of the three-level converters is controlled to execute the target control scheme obtained from the parameters of the first converter and the parameters of the second converter.

[0006] Preferably, the step of acquiring the target operating requirements of the target power system and the real-time operating data of each three-level converter in the target power system, and determining the sub-operating requirements of each of the three-level converters based on the target operating requirements and the real-time operating data, includes: Analyze the acquired operational data of the target power system, and determine the target operational requirements based on the analysis results; Based on the real-time operating data, the real-time energy value of each of the three-level converters is determined; The real-time energy values ​​are sorted, and based on the sorting results and the target operation requirements, the sub-operation requirements are determined.

[0007] Preferably, the determination of the energy requirement for each of the three-level converters includes voltage energy requirement and power energy requirement, comprising: Analyze the power capacity of each of the three-level converters to obtain the target three-level converter with the maximum power capacity, and then remove the target three-level converter to obtain the first set of three-level converters; Set the energy requirement of the target three-level converter to the voltage energy requirement; The energy requirements of each of the first three-level converters in the first three-level converter cluster are determined based on preset conditions.

[0008] Preferably, determining the energy demand of each of the first three-level converters in the first three-level converter cluster based on preset conditions includes: The target operating requirements and the sub-operating requirements of each of the first three-level converters are analyzed at least to determine the preset conditions.

[0009] Preferably, the first converter parameter for determining the three-level converter corresponding to the voltage energy demand is obtained from the DC voltage deviation of the three-level converter. The DC voltage deviation is obtained from the corresponding sub-operational demand and the real-time operating data, including: The energy deviation value is obtained by analyzing the sub-operation requirements and the real-time operation data; The DC voltage deviation is obtained based on the energy deviation value; Based on the DC voltage deviation and the preset DC voltage difference, a DC voltage reference value is obtained; Based on the DC voltage reference value, the parameters of the first converter are obtained.

[0010] Preferably, obtaining the DC voltage deviation based on the energy deviation value includes: At least a proportional-integral technique is used to convert the energy deviation value into the DC voltage deviation.

[0011] Preferably, determining the first converter parameters of the three-level converter corresponding to the voltage energy demand includes: The first converter parameters include at least the parameters of the dual half-bridge cascaded protection circuit and the converter circuit parameters.

[0012] Preferably, the second converter parameter for determining the three-level converter corresponding to the power energy demand is obtained from the active power deviation of the three-level converter. The active power deviation is obtained from the corresponding sub-operational demand and the real-time operating data, including: The energy deviation value is obtained by analyzing the sub-operation requirements and the real-time operation data; Based on the energy deviation value, the active power deviation is obtained; Based on the active power deviation and the preset active power, an active power reference value is obtained; The parameters of the second converter are obtained based on the active power reference value.

[0013] Preferably, after controlling each of the three-level converters to execute the target control scheme obtained from the first converter parameters and the second converter parameters, the method further includes: Record the control parameters of the target control scheme and the corresponding sub-operational requirements to obtain historical control data; Based on the historical control data, the preset conditions for the next cycle are optimized to obtain the target preset conditions for the next cycle.

[0014] Another aspect of the present invention provides a direct-energy control system for a cascaded three-level converter, comprising: The acquisition module is used to acquire the target operating requirements of the target power system and the real-time operating data of each three-level converter in the target power system, and to determine the sub-operating requirements of each three-level converter based on the target operating requirements and the real-time operating data. A determination module is used to determine the energy requirements of each of the three-level converters, wherein the energy requirements include voltage energy requirements and power energy requirements; The first module is used to determine the first converter parameters of the three-level converter corresponding to the voltage energy demand. The first converter parameters are obtained from the DC voltage deviation of the three-level converter. The DC voltage deviation is obtained from the corresponding sub-operational demand and the real-time operation data. The second module is used to determine the second converter parameters of the three-level converter corresponding to the power energy demand. The second converter parameters are obtained from the active power deviation of the three-level converter. The active power deviation is obtained from the corresponding sub-operational demand and the real-time operation data. The target module is used to control each of the three-level converters to execute the target control scheme obtained from the first converter parameters and the second converter parameters.

[0015] Compared with the prior art, the beneficial effects of the present invention are at least one of the following: This invention overcomes the limitations of existing technologies that rely solely on voltage (e.g., constant DC-side voltage) for control by acquiring the target operating requirements of the target power system and the real-time operating data of each three-level converter, and determining the sub-operating requirements of each converter based on these two data. Furthermore, it determines the voltage energy requirement and power energy requirement of each converter, and correspondingly derives the first converter parameters from the DC voltage deviation and the second converter parameters from the active power deviation. Finally, it controls each converter to execute the target control scheme generated jointly by the first and second converter parameters. Therefore, this invention can adjust the control strategy in real time according to grid dispatch requirements or operating conditions, enabling the power system to respond promptly to system fluctuations. The generated control scheme is more aligned with actual adjustment needs, thereby effectively ensuring the safe and stable operation of the power system. Attached Figure Description

[0016] Figure 1 This is a flowchart illustrating the direct energy control method for a cascaded three-level converter in one embodiment of the present invention. Figure 2 This is a schematic diagram of the neutral point clamping module in one embodiment of the present invention; Figure 3 This is a schematic diagram of the energy direct control system of a cascaded three-level converter in one embodiment of the present invention; Figure label: Among them, 11 is the acquisition module; 12 is the determination module; 13 is the first module; 14 is the second module; and 15 is the target module. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0018] In the description of this invention, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," "third," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0019] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0020] In the description of this invention, it should be noted that, unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in this specification is for the purpose of describing specific embodiments only and is not intended to limit the invention. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0021] In power system operation, proper control of cascaded three-level converters can convert AC power into DC power of a selected level, contributing to safe and stable operation. However, existing control methods are solely based on voltage (such as taking constant DC side voltage as the only objective), and cannot be adjusted in real time according to dispatching needs or operating conditions. This makes it difficult for the system to respond to fluctuations in a timely manner, and the control strategy does not meet actual regulation requirements, ultimately affecting safe and stable operation.

[0022] One embodiment of the present invention provides a direct energy control method for a cascaded three-level converter. For details, please refer to [link to relevant documentation]. Figure 1 , Figure 1 The diagram shown is a flowchart illustrating a direct energy control method for a cascaded three-level converter according to one embodiment of the present invention, comprising: S1. Obtain the target operating requirements of the target power system and the real-time operating data of each three-level converter in the target power system, and determine the sub-operating requirements of each three-level converter based on the target operating requirements and the real-time operating data. S2. Determine the energy requirements of each of the three-level converters, wherein the energy requirements include voltage energy requirements and power energy requirements; S3. Determine the first converter parameter of the three-level converter corresponding to the voltage energy demand. The first converter parameter is obtained from the DC voltage deviation of the three-level converter. The DC voltage deviation is obtained from the corresponding sub-operation demand and the real-time operation data. S4. Determine the second converter parameter of the three-level converter corresponding to the power energy demand. The second converter parameter is obtained from the active power deviation of the three-level converter. The active power deviation is obtained from the corresponding sub-operation demand and the real-time operation data. S5. Control each of the three-level converters to execute the target control scheme obtained from the first converter parameters and the second converter parameters.

[0023] One embodiment of the present invention employs a cascaded three-level energy direct control circuit to implement the cascaded three-level energy direct control method and the cascaded three-level energy direct control system of the present invention. The cascaded three-level energy direct control circuit includes: N NPC (Neutral Point Clamped) modules with voltage regulation and multiplexing functions of protection circuits, an isolation transformer, a voltage-regulated energy direct control module based on the voltage regulation and multiplexing function of the protection circuits, a power-regulated energy direct control module based on the voltage regulation and multiplexing function of the protection circuits, an outer loop control module, an inner loop control module, and an inter-module voltage equalization module.

[0024] N protection circuits with voltage regulation and multiplexing function NPC modules are connected in parallel on their AC sides, and each NPC module has an isolation transformer connected on its AC side, and their DC sides are connected in series to improve the DC withstand voltage and transmission capacity of the CNPC. Each NPC module with voltage regulation and multiplexing function, in addition to using a traditional three-phase diode-clamped three-level bridge arm, has a protection circuit based on dual half-bridge cascade on its DC side. For example... Figure 2 As shown, Figure 2The diagram shows a schematic of the neutral point clamping module in one embodiment of the present invention. The AC side terminals A, B, and C are directly connected to the midpoints of the A, B, and C phase arms of the main circuit (i.e., the connection points between the upper and lower power switching devices of each phase), serving as the interface between the module and an external three-phase AC power supply or load. The main circuit of the NPC module is a three-phase diode-clamped three-level bridge arm, which is the core part for performing three-phase rectification / inverting power conversion. The main circuit consists of three phase arms A, B, and C. Each phase arm has multiple power switching devices with anti-parallel diodes arranged above and below it, and the midpoint of the bridge arm is connected to the intermediate neutral point (capacitor midpoint node) on the DC side through clamping diodes. The DC bus adopts a split capacitor structure, with positive and negative capacitors connected in series to divide the voltage, forming three DC potentials: positive, neutral, and negative, providing the operating voltage required for the three-level operation of the main circuit. On the DC side of the main circuit, a protection circuit based on a dual half-bridge cascade is also configured. This protection circuit consists of a first half-bridge and a second half-bridge cascaded vertically. Each half-bridge contains two power switching devices with anti-parallel diodes (labeled as the first device and the second device in the figure, respectively). They are connected across / cascaded between the positive, neutral, and negative potentials on the DC side for energy bypass, clamping, and voltage regulation multiplexing functions during faults. In terms of overall connection, the DC side output / neutral bus of the main circuit is directly connected to the protection circuit on the right. That is, the positive, neutral, and negative potentials of the DC bus are respectively connected to the corresponding nodes of the dual half-bridge cascaded protection stage. Thus, based on the traditional three-phase diode clamping three-level bridge arm, this module has DC side protection and voltage regulation capabilities.

[0025] This protection circuit adopts a topology based on dual half-bridge cascade. Under normal operating conditions, the power switching devices in each half-bridge can be actively controlled to turn on and off through pulse width modulation or duty cycle adjustment, thereby flexibly changing the connection state of the DC-side equivalent circuit, the energy throughput path, or the voltage divider / clamping ratio. At the same time, the combination of capacitors and switches connected between the positive, neutral, and negative potentials can dynamically distribute and rebalance the DC bus voltage, realizing active adjustment of the neutral point potential and stable control of the bus voltage. Therefore, this circuit not only provides bypass and clamping protection during faults, but also has voltage regulation and multiplexing capabilities during normal operation.

[0026] The voltage-regulated energy direct control module based on the voltage regulation multiplexing function of the protection circuit has its input terminals connected to the measured energy signal terminal of the CNPC (Cascaded Neutral Point Clamped) and the command reference value terminal of the scheduling or coordinated control, respectively. Its output terminal is connected to the DC voltage reference value input terminal of the outer loop control module. It is used to convert the energy deviation value into a DC voltage deviation value through the PI or PR controller, and then sum it with the preset DC voltage to generate a DC voltage reference value. The power regulation type energy direct control module based on the voltage regulation multiplexing function of the protection circuit has its input terminal connected to the measured energy signal terminal and the command reference value terminal of the CNPC respectively, and its output terminal connected to the active power reference value input terminal of the outer loop control module. It is used to convert the energy deviation value into an active power deviation value through the PI or PR controller, and then sum it with the preset active power to generate an active power reference value. The outer loop control module has its input terminals connected to the output terminals of the voltage-regulated energy direct control module and the power-regulated energy direct control module, respectively, and its output terminal connected to the input terminal of the inner loop control module. It is used to perform outer loop control based on the received DC voltage reference value or active power reference value. The inner loop control module has its input connected to the output of the outer loop control module and its output connected to the input of the inter-module voltage equalization module, and is used to execute the inner loop control. The inter-module voltage equalization module has its input terminal connected to the output terminal of the inner loop control module, and its output terminal connected to the control terminal of all switching devices in the CNPC, in order to generate trigger pulses to achieve inter-module voltage equalization.

[0027] First, the target operating requirements of the target power system and the real-time operating data of each three-level converter in the target power system are obtained. Based on the target operating requirements and the real-time operating data, the sub-operating requirements of each three-level converter are determined. The obtained operating data of the target power system is analyzed, and the target operating requirements are determined based on the analysis results. Based on the real-time operating data, the real-time energy values ​​of each three-level converter are determined. The real-time energy values ​​are sorted, and based on the sorting results and the target operating requirements, the sub-operating requirements are determined.

[0028] The target power system refers to the overall power grid operation object, namely, the power conversion and stability control system containing multiple cascaded three-level converters. The target operating requirements are the overall control objectives determined by analyzing system-level operating data (such as frequency, load, and dispatch commands). The three-level converter is the basic power conversion unit constituting the system, i.e., a module with a neutral-point clamping (NPC) topology. Real-time operating data consists of the actual electrical parameters (such as voltage, current, and power) collected by each converter at the current moment. Real-time energy values ​​are the quantified values ​​of the current energy state of each converter calculated based on these real-time data. Sub-operating requirements are specific control sub-objectives assigned to each individual converter within the framework of the target operating requirements, combined with the ranking results of the real-time energy values ​​of each converter, to ensure that all modules work together to achieve the overall system control objectives.

[0029] System-level operational data is acquired from the target power system's dispatch center or energy management system. This data includes the current grid frequency, bus voltages, total load power, dispatch command curves issued by higher authorities, and system stability boundary conditions. This data undergoes filtering and normalization preprocessing. Subsequently, system-level power balance analysis or optimal power flow calculations determine the overall target operational requirements the system needs to achieve at the current moment, such as the total DC voltage reference value, total active power output command, or reactive power regulation. Simultaneously, real-time operational data for each module is collected from local sensors in each three-level converter. This includes DC-side voltage, AC-side three-phase current, module temperature, and switch status. Digital signal processors or field-programmable gate arrays are used to perform analog-to-digital conversion and digital filtering on the collected analog quantities to obtain the real-time electrical parameters of each converter at the current moment.

[0030] Based on the real-time operating data of each converter, the actual real-time energy value of each three-level converter is calculated according to the preset real-time energy value calculation formula. The energy values ​​of all modules are then sorted from highest to lowest or lowest to highest, resulting in a relative high-low sequence of the current energy levels of each module. Finally, the sorting results and the system-level target operating requirements are used as input. Specific sub-operating requirements are assigned to each three-level converter according to a preset allocation rule. This allocation rule assigns more power regulation tasks to modules with higher energy values ​​and fewer regulation tasks to modules with lower energy values, or prioritizes receiving charging commands. This ensures that the sum of the voltage regulation target, power output target, or energy balance target that each module should achieve can fully and coordinately realize the overall system-level target operating requirements.

[0031] Assuming the target power system has three three-level converters, and the system-level target operating requirements are a total power output of 6MW and a stable total DC voltage of 30kV, the real-time energy values ​​calculated based on the real-time operating data of each converter are 500J for the first converter, 300J for the second converter, and 200J for the third converter, with a total energy value of 1000J. These are ordered from highest to lowest energy value, resulting in the first, second, and third converters. According to a preset allocation rule, the module with the higher energy value undertakes more power regulation tasks. Modules with lower energy values ​​receive charging commands first. The specific calculation process is as follows: the energy proportions of each converter are 500÷1000=0.5, 300÷1000=0.3, and 200÷1000=0.2, respectively. Multiplying the system's total power target of 6MW by the three energy proportions respectively yields the active power output of the first converter (6×0.5=3MW), the second converter (6×0.3=1.8MW), and the third converter (6×0.2=1.2MW). The sum of these three is 6MW, which satisfies the system's total power target. The target total system voltage of 30kV is calculated by multiplying the voltage regulation values ​​of the three converters by their respective energy proportions: 30 × 0.5 = 15kV for the first converter, 30 × 0.3 = 9kV for the second converter, and 30 × 0.2 = 6kV for the third converter. The sum of these three values ​​is 30kV. Combined with the preset reference voltages on the DC side of each converter, these values ​​collectively support the stable requirement of a total DC voltage of 30kV for the system. The average energy value is calculated to be 1000 ÷ 3 = 333.33J. The real-time energy value of the third converter, 200J, is lower than the average value. Therefore, additional charging commands are received. The first converter (500J) and the second converter (300J) are not lower than the average value and do not receive charging commands. The active power value, voltage regulation value and charging command calculated above together constitute the sub-operational requirements of each converter. That is, the sub-operational requirements are the specific control sub-objectives assigned to each converter individually under the framework of system-level target operation requirements, combined with the real-time energy value ranking results of each converter. The sum of the sub-operational requirements of all converters fully and coordinately realizes the overall target operation requirements of the system.

[0032] Preferably, the energy requirement of each three-level converter is determined, wherein the energy requirement includes voltage energy requirement and power energy requirement. The power capacity of each three-level converter is analyzed to obtain the target three-level converter with the largest power capacity, and the target three-level converter is removed to obtain the first set of three-level converters; the energy requirement of the target three-level converter is set as the voltage energy requirement; the energy requirement of each three-level converter in the first set of three-level converters is determined based on preset conditions.

[0033] Three-level converters are the basic power conversion units that constitute a cascaded system, i.e., modules with neutral-point clamping topologies. Energy demand refers to the energy regulation tasks that each three-level converter needs to undertake to achieve the overall system control objectives, specifically divided into two dimensions: voltage energy demand and power energy demand. Voltage energy demand refers to the energy regulation tasks that the converter needs to undertake related to DC-side voltage stability. Power energy demand refers to the energy regulation tasks that the converter needs to undertake related to active power output or absorption. Energy capacity refers to the maximum energy capacity that each three-level converter can store or process, usually determined by its DC-side capacitor value and rated voltage. The target three-level converter is the one with the largest energy capacity among all converters. The first three-level converter set refers to the set of converters remaining after removing the target converter with the largest energy capacity from all converters. Preset conditions refer to the pre-set rules or criteria used to determine what kind of energy demand should be allocated to each converter in the first three-level converter set. These conditions can be determined based on the target operating requirements and the sub-operating requirements of each converter.

[0034] The energy capacity data of all three-level converters is obtained. This energy capacity is determined by the capacitance and rated voltage of the DC-side capacitors of each converter, and can be obtained through factory parameters or online identification. Then, all converters are traversed, and their energy capacities are compared. The converter with the largest capacity is selected as the target three-level converter and removed from the overall set to form the first set of three-level converters. For the removed target three-level converter, its energy demand is directly set as the voltage energy demand. That is, this converter will only participate in the DC bus voltage regulation task and will not undertake power-related energy regulation. This is because the converter with the largest capacity has a stronger voltage support capability, and using it specifically for voltage stability control can give full play to its hardware advantages.

[0035] For each remaining converter in the first three-level converter cluster, its energy demand is determined one by one according to preset conditions. These preset conditions are obtained by analyzing the target operating requirements and the sub-operating requirements of each converter at the system level. For example, based on factors such as the current energy level of each converter, its location, and scheduling instructions, it is determined which converters are suitable to handle voltage energy demand and which are suitable to handle power energy demand. The premise for this step is that each NPC module in the circuit of the present invention is equipped with a protection circuit based on dual half-bridge cascade. When the protection circuit is working normally, it can actively adjust the DC bus voltage distribution and midpoint potential balance through PWM, and has the function of voltage regulation multiplexing. At the same time, the structure of parallel AC side and series DC side of each module allows the system to flexibly allocate different modules to undertake voltage or power regulation tasks. Therefore, when each converter is assigned voltage energy demand or power energy demand in the above manner, the voltage regulation type energy direct control module and the power regulation type energy direct control module can generate corresponding DC voltage reference value and active power reference value according to these demands, respectively. Through the outer loop control module, the inner loop control module and the inter-module voltage equalization module, a drive pulse is finally formed to control each converter to perform its assigned energy regulation task.

[0036] Specifically, at least the target operating requirements and the sub-operating requirements of each of the first three-level converters should be analyzed to determine the preset conditions. The first three-level converters refer to all the converters remaining after removing the target converter with the largest energy capacity from all converters. Sub-operating requirements are specific control sub-objectives assigned to each individual converter within the framework of the target operating requirements, based on the ranking of real-time energy values. Preset conditions are pre-defined judgment rules, determined at least based on the analysis of the system-level target operating requirements and the sub-operating requirements of each remaining converter, used to decide whether the first three-level converters should ultimately bear the voltage energy requirement or the power energy requirement.

[0037] First, the specific values ​​in the target operating requirements are obtained, such as the system requiring a stable total DC voltage within ±10kV and a total active power output of 5MW. Simultaneously, the sub-operating requirements of each converter in the first three-level converter cluster are obtained, such as converter A requiring a voltage regulation of ±2kV, converter B requiring a power regulation of 1MW, and converter C requiring a voltage regulation of ±1.5kV. Then, these individual sub-operating requirements are accumulated separately according to voltage and power categories to obtain the total voltage and power regulation allocated to all remaining converters, and compared with the total voltage and total power targets in the system's target operating requirements. If the total allocated voltage regulation is less than the system's total voltage target, the preset condition is set to prioritize allocating voltage energy demand to individuals in the remaining converters whose sub-operational needs are biased towards voltage regulation. If the total allocated power regulation is less than the system's total power target, the preset condition is set to prioritize allocating power energy demand to individuals whose sub-operational needs are biased towards power regulation. If both conditions are met, the preset condition can be set to allocate voltage energy demand or power energy demand sequentially according to the real-time energy values ​​of each converter from low to high, in order to achieve energy balance. Finally, through the above logical judgment based on numerical comparison, a clear set of preset condition rule tables is formed, which is directly used to guide the energy demand allocation decision of each converter in the first three-level converter system.

[0038] Assuming that there are three converters remaining in the first three-level converter cluster, namely the first converter, the second converter, and the third converter, the total system voltage target is 30kV and the total power target is 10MW. The current allocated voltage regulation is 11kV and the allocated power regulation is 5MW. In this case, the total voltage regulation is less than the total system voltage target and the total power regulation is also less than the total system power target. At this time, the preset condition is set as follows: priority is given to allocating voltage energy demand to converters whose sub-operation demand is biased towards voltage regulation, and priority is given to allocating power energy demand to converters whose sub-operation demand is biased towards power regulation. The term "sub-operational demand biased towards voltage regulation" refers to a situation where voltage regulation tasks constitute a larger proportion of the sub-operational demand for a converter. For example, if the sub-operational demand of the first converter is to regulate a DC voltage of 6kV and an active power of 1MW, and the proportion of voltage regulation in its total task is significantly higher than that of power regulation, then the first converter is determined to be biased towards voltage regulation, and the first converter is allocated voltage energy demand. Conversely, "sub-operational demand biased towards power regulation" refers to a situation where power regulation tasks constitute a larger proportion of the sub-operational demand for a converter. For example, if the sub-operational demand of the second converter is to regulate a DC voltage of 2kV and an active power of 4MW, and the proportion of power regulation in its total task is significantly higher than that of voltage regulation, then the second converter is determined to be biased towards power regulation, and the second converter is allocated power energy demand. If the next cycle detects that the total allocated voltage regulation reaches 30kV and the total allocated power regulation reaches 10MW, both of which meet the system target, the preset condition is changed to allocate voltage energy demand or power energy demand in order of the real-time energy values ​​of the first, second, and third converters from low to high. This ensures that the converter with the lowest energy value receives the regulation task first, so as to level the energy levels of each module. The above judgment logic is finally solidified into a rule table. Each row in the table corresponds to a numerical comparison result and its corresponding allocation rule. In each control cycle, the table can be directly consulted to determine whether each converter in the first three-level converter group should be allocated voltage energy demand or power energy demand.

[0039] Preferably, the first converter parameters corresponding to the voltage energy demand of the three-level converter are determined. The first converter parameters are obtained from the DC voltage deviation of the three-level converter, which is obtained from the corresponding sub-operational demand and real-time operating data. The energy deviation value is obtained by analyzing the sub-operational demand and real-time operating data; the DC voltage deviation is obtained based on the energy deviation value; the DC voltage reference value is obtained based on the DC voltage deviation and the preset DC voltage difference; and the first converter parameters are obtained based on the DC voltage reference value.

[0040] Voltage energy demand refers to the energy regulation task related to DC-side voltage stability that the converter needs to undertake; the first converter parameter refers to the corresponding control quantity generated to achieve the voltage energy demand. This parameter includes at least the parameters of the dual half-bridge cascaded protection circuit and the converter circuit parameters, which are used to drive the converter to perform voltage regulation actions; DC voltage deviation is the voltage difference calculated from the difference between the converter's sub-operational demand and its real-time operating data, reflecting the degree of deviation between the current actual DC voltage and the target demand; sub-operational demand is the specific control sub-objective assigned to each converter under the framework of target operating demand; real-time operating data is the actual electrical parameters collected by each converter at the current moment, including DC-side voltage, AC-side three-phase current, etc.; energy deviation value is the energy domain difference obtained after analyzing the sub-operational demand and real-time operating data. This value is converted into DC voltage deviation through proportional-integral technology; preset DC voltage difference is the DC voltage rated value or reference value preset by the system; DC voltage reference value is the final voltage command value obtained by summing the DC voltage deviation and the preset DC voltage difference, which serves as the input target of the outer loop control.

[0041] First, the target voltage value to be achieved by each three-level converter is extracted from the sub-operational requirements corresponding to that converter. Simultaneously, the actual DC-side voltage value of the converter at the current moment is obtained from real-time operating data. The voltage deviation is obtained by subtracting the actual voltage value from the target voltage value. However, since the core of this invention lies in direct energy control, this voltage deviation needs to be converted into an energy deviation value. Specifically, the voltage deviation is multiplied by the capacitance value of the converter's DC-side capacitor and then multiplied by the average voltage value to obtain the current energy deviation value. Then, a voltage-regulated direct energy control module is used. The input terminals of this module are connected to the measured energy signal terminal of the CNPC and the instruction reference value terminal of the scheduling or coordinated control. It integrates a proportional-integral or proportional-resonant controller. The aforementioned energy deviation value is input to this module, and after calculation by the controller, the corresponding DC voltage deviation value is output, thus completing the conversion from energy deviation to voltage deviation.

[0042] The calculated DC voltage deviation is summed with the preset DC voltage difference corresponding to the converter. The preset DC voltage difference is the rated reference value of the DC side voltage of the converter preset by the system. After summing, the DC voltage reference value of the converter is obtained, which represents the target voltage command that the converter should achieve. Subsequently, the voltage-regulated energy direct control module outputs the DC voltage reference value to the DC voltage reference value input terminal of the outer loop control module. The outer loop control module performs outer loop control according to the reference value, and its output is sent to the inner loop control module to perform inner loop control. The output of the inner loop control module is then sent to the inter-module voltage equalization module. Finally, the inter-module voltage equalization module generates a trigger pulse and outputs it to the control terminal of all switching devices in the CNPC. The first converter parameters generated in this process specifically include the pulse width modulation duty cycle command of each power switching device in the dual half-bridge cascaded protection circuit and the conduction sequence of each bridge arm switching device in the main circuit. These parameters directly drive the converter to perform voltage regulation, so that the actual DC voltage follows the DC voltage reference value, thereby achieving the voltage stability control target required by the voltage energy demand.

[0043] Specifically, in one embodiment of the present invention, it is assumed that the DC-side capacitor of a three-level converter in the target power system has a capacitance of 4.7mF, and the system's pre-set rated reference value for the DC-side voltage of the converter is 10kV. During the current control cycle, the target voltage value to be achieved is extracted from the sub-operational requirements corresponding to the converter, which is 10.2kV. Simultaneously, the actual DC-side voltage value of the converter at the current moment is collected from real-time operating data, which is 9.8kV. Subtracting the actual voltage value from the target voltage value yields the voltage deviation = 10.2kV - 9.8kV = 0.4kV. Since the core of this invention is direct energy control, this voltage deviation needs to be converted into an energy deviation value. Specifically, the voltage deviation is multiplied by the DC-side capacitor value and then multiplied by the average voltage value, i.e., the energy deviation value = 0.4kV × 4.7mF × 10kV = 18.8J, resulting in an energy deviation value of 18.8 joules at the current moment. The energy deviation value is then sent to the voltage-regulated direct energy control module. The input of this module is connected to the measured energy signal terminal of CNPC and the instruction reference value terminal of scheduling or coordinated control. The integrated proportional-integral controller performs calculations according to the proportional coefficient Kp=0.5 and the integral coefficient Ki=20. Assuming that the DC voltage deviation value after PI regulation is 0.15kV, the conversion from energy deviation to voltage deviation is completed.

[0044] Next, the calculated DC voltage deviation of 0.15kV is summed with the preset DC voltage difference of 10kV corresponding to the converter to obtain a DC voltage reference value of 10kV + 0.15kV = 10.15kV. This reference value represents the target voltage command that the converter should achieve. Subsequently, the voltage-regulated energy direct control module outputs this DC voltage reference value to the DC voltage reference value input terminal of the outer loop control module. The outer loop control module performs outer loop control based on the 10.15kV reference value and outputs the current reference value required by the inner loop. This current reference value is sent to the inner loop control module to perform inner loop control. The inner loop control module performs closed-loop regulation based on the real-time acquired AC three-phase current to generate a modulation wave signal. Its output is then sent to the inter-module voltage equalization module. Finally, the inter-module voltage equalization module compares the modulation wave with the high-frequency carrier and superimposes the inter-module voltage equalization compensation amount to form a trigger pulse and outputs it to the control terminal of all switching devices in the CNPC. The first converter parameters generated during this process specifically include the pulse width modulation duty cycle commands of each power switching device in the dual half-bridge cascaded protection circuit and the conduction timing of each bridge arm switching device in the main circuit. For example, the duty cycle of the first switching device in the upper bridge arm of phase A of the main circuit is adjusted to 0.52, the duty cycle of the second switching device in the lower bridge arm is adjusted to 0.48, and the duty cycle of the first switching device in the first half-bridge of the protection circuit is adjusted to 0.55. These parameters directly drive the converter to perform voltage regulation, so that the actual DC voltage gradually rises from 9.8kV and follows the DC voltage reference value of 10.15kV, thereby achieving the voltage stability control target required by the voltage energy demand.

[0045] Specifically, at least proportional-integral (PI) technology should be used to convert the energy deviation value into a DC voltage deviation. PI technology is a closed-loop control algorithm. Its proportional part multiplies the current energy deviation value by a proportional coefficient to quickly respond to instantaneous changes, while its integral part multiplies the accumulated energy deviation value over time by an integral coefficient to eliminate steady-state error. The two are then added together to output the control quantity.

[0046] First, the calculated energy deviation value is sent as an input signal to a voltage-regulated energy direct control module based on the voltage regulation multiplexing function of the protection circuit. This module integrates a proportional-integral controller. The proportional element in the controller multiplies the current energy deviation value by a proportional coefficient to generate a fast-response adjustment component. The integral element accumulates the energy deviation value over time and then multiplies it by an integral coefficient to eliminate static errors. The two are then superimposed to output the corresponding DC voltage deviation value. If there are harmonics or periodic disturbances on the AC side of the converter, a proportional-resonant controller can be used instead of a proportional-integral controller. It provides high gain at the resonant frequency to suppress specific harmonics. In addition, a proportional-integral-derivative controller can be used to introduce a derivative element to enhance the dynamic response speed of the system, or a fuzzy proportional-integral controller can be used to adaptively adjust the proportional coefficient and integral coefficient according to the magnitude and rate of change of the energy deviation value. Model predictive control can also be used to directly predict the future response based on the discrete model of the system and select the optimal voltage deviation output.

[0047] Specifically, the first converter parameters include at least the parameters of the dual half-bridge cascaded protection circuit and the converter circuit parameters. The dual half-bridge cascaded protection circuit parameters refer to the pulse width modulation duty cycle commands and conduction sequences that each power switching device in the two cascaded half-bridges should execute in the protection circuit configured on the DC side of each neutral point clamping module. These parameters directly determine how the protection circuit achieves dynamic distribution of the DC bus voltage and regulation of the neutral point potential through switching actions. The converter circuit parameters refer to the pulse width modulation duty cycle commands and conduction sequences that each power switching device in the A, B, and C phase arms of the neutral point clamping module's main circuit should execute. These parameters directly determine the voltage output state when the main circuit performs three-phase rectification or inverter power conversion.

[0048] In the circuit of this embodiment of the invention, the DC side of the main circuit of each neutral point clamping module is equipped with a protection circuit based on dual half-bridge cascade. The main circuit is a three-phase diode clamping three-level bridge arm of A, B, and C, which is responsible for performing three-phase rectification or inverter power conversion. The protection circuit is composed of a first half-bridge and a second half-bridge cascaded vertically. Each half-bridge contains two power switching devices, which are connected across the positive, neutral, and negative potentials of the DC side. When the voltage-regulated direct-control module generates a DC voltage reference value and processes it through the outer loop control module, inner loop control module, and inter-module voltage equalization module, the final output of the first converter parameter actually includes two types of instructions: one type is the converter circuit parameters acting on the power switching devices of each power switching device in the A, B, and C phase arms of the main circuit, namely the pulse width modulation duty cycle and conduction sequence of each switching device, used to control the main circuit to achieve the required voltage transformation; the other type is the double half-bridge cascaded protection circuit parameters acting on the power switching devices of each stage of the double half-bridge in the protection circuit, namely the pulse width modulation duty cycle and conduction sequence of each switching device in the protection circuit, used to control the protection circuit to actively adjust the DC bus voltage distribution and midpoint potential balance during normal operation. Both types of parameters are output simultaneously and drive the switching devices of the main circuit and the protection circuit respectively, enabling the converter to achieve power transformation through the main circuit and stabilize the DC voltage through the voltage regulation multiplexing function of the protection circuit when performing voltage regulation tasks, thereby jointly achieving the complete control objective of voltage energy demand.

[0049] Preferably, the second converter parameters corresponding to the power energy demand of the three-level converter are determined. These second converter parameters are obtained from the active power deviation of the three-level converter, which is derived from the corresponding sub-operational demand and real-time operating data. The sub-operational demand and real-time operating data are analyzed to obtain the energy deviation value; based on the energy deviation value, the active power deviation is obtained; based on the active power deviation and the preset active power, an active power reference value is obtained; and based on the active power reference value, the second converter parameters are obtained.

[0050] Power energy demand refers to the energy regulation tasks related to active power output or absorption that the converter needs to undertake; the second converter parameter is a set of control quantities generated to achieve the power energy demand, used to drive the converter to perform power regulation actions; the active power deviation is the power difference calculated from the difference between the converter's sub-operational demand and its real-time operating data, reflecting the degree of deviation between the current actual active power and the target demand; the sub-operational demand is a specific control sub-objective assigned to each converter under the framework of the target operating demand; the real-time operating data is the actual electrical parameters collected by each converter at the current moment, including the three-phase current on the AC side, the voltage on the DC side, and other physical quantities used to calculate active power; the energy deviation value is the energy domain difference obtained after analyzing the sub-operational demand and the real-time operating data, which is converted into active power deviation through proportional-integral technology; the preset active power is the rated or reference value of active power preset by the system; the active power reference value is the final power command value obtained by summing the active power deviation and the preset active power, serving as the input target of the outer loop control.

[0051] First, the target power value to be achieved by each three-level converter is extracted from the sub-operational requirements corresponding to that converter. Simultaneously, the actual active power value of the converter at the current moment is obtained from real-time operating data. The actual active power can be calculated by collecting the three-phase current on the AC side and the voltage on the DC side according to instantaneous power theory. The deviation in the power domain is obtained by subtracting the actual power value from the target power value. However, since the core of this invention is direct energy control, this power deviation needs to be converted into an energy deviation value. Specifically, the power deviation is integrated over time to obtain the energy deviation value at the current moment. Then, a power-regulated direct energy control module is used. The input terminals of this module are connected to the measured energy signal terminal of the CNPC and the instruction reference value terminal of the scheduling or coordinated control. It integrates a proportional-integral or proportional-resonant controller. The aforementioned energy deviation value is input into this module, and after calculation by the controller, the corresponding active power deviation value is output, thus completing the conversion from energy deviation to power deviation.

[0052] The calculated active power deviation is summed with the preset active power corresponding to the converter. The preset active power is the rated active power reference value of the converter set in advance by the system. After summing, the active power reference value of the converter is obtained. This reference value represents the target power command that the converter should achieve. Subsequently, the power-regulated direct energy control module outputs the active power reference value to the active power reference value input terminal of the outer loop control module. The outer loop control module executes outer loop control based on this reference value, and its output is sent to the inner loop control module to execute inner loop control. The output of the inner loop control module is then sent to the inter-module voltage equalization module. Finally, the inter-module voltage equalization module generates a trigger pulse and outputs it to the control terminals of all switching devices in the CNPC. The second converter parameters generated in this process specifically include the pulse width modulation duty cycle commands of each power switching device in the A, B, and C three-phase bridge arms of the main circuit. By adjusting the conduction duty cycle of each switching device, the amplitude and phase of the AC side current of the converter are changed, thereby controlling the magnitude and direction of the active power, so that the actual active power follows the active power reference value, and achieving the power regulation and control target required by the power energy demand.

[0053] Finally, each three-level converter is controlled to execute the target control scheme obtained from the parameters of the first and second converters. The target control scheme is a comprehensive set of control commands obtained by fusing the parameters of the first and second converters. This scheme includes both voltage regulation commands and power regulation commands, and coordinates the relationship between the two in terms of execution timing and priority.

[0054] The first converter parameters generated by the voltage-regulated direct energy control module and the second converter parameters generated by the power-regulated direct energy control module are simultaneously sent to the outer loop control module. Based on the received DC voltage and active power reference values, the outer loop control module calculates the required current or voltage reference values ​​for the inner loop according to a preset outer loop control strategy and outputs the calculation results to the inner loop control module. The inner loop control module, based on the received reference values ​​and combined with the real-time acquired AC three-phase current and DC voltage, performs closed-loop regulation of the current or voltage inner loop, generating corresponding modulation wave signals and outputting them to the inter-module voltage equalization module. The inter-module voltage equalization module receives the output of the inner loop control module, compares the modulated wave signal with the high-frequency carrier, and superimposes the inter-module voltage equalization compensation amount. Finally, it forms the pulse width modulation trigger pulses of all switching devices in each converter. These pulses simultaneously drive the power switching devices of the A, B, and C three-phase bridge arms of the main circuit of each neutral point clamping module, as well as the power switching devices at each stage in the DC side double half-bridge cascaded protection circuit. This enables each converter to perform voltage regulation according to the first converter parameter and power regulation according to the second converter parameter, thereby fully executing the target control scheme generated by the fusion of the two types of parameters.

[0055] After controlling each three-level converter to execute the target control scheme obtained from the parameters of the first converter and the second converter, the method further includes: recording the control parameters of the target control scheme and the corresponding sub-operation requirements to obtain historical control data; and optimizing the preset conditions for the next cycle based on the historical control data to obtain the target preset conditions for the next cycle.

[0056] Control parameters refer to the various values ​​actually output in the target control scheme, including the pulse width modulation duty cycle of each converter, DC voltage reference value, active power reference value, and intermediate variables of the outer loop control module and inner loop control module; historical control data is a data set formed by associating the control parameters of the target control scheme with the corresponding sub-operational requirements for each run, including the correspondence between control parameters and sub-operational requirements; preset conditions are pre-set rules or criteria for determining what kind of energy demand should be allocated to each converter in the first three-level converter group; the next cycle refers to the next control execution cycle after the current control cycle ends; the target preset conditions for the next cycle are updated preset conditions obtained by optimizing historical control data, which are used to more accurately guide the energy demand allocation decision of each converter in the next control cycle.

[0057] At the end of each control cycle, the digital signal processor or host computer in the control system records all control parameters in the target control scheme executed this time, including but not limited to the DC voltage reference value output by the voltage regulation type energy direct control module, the active power reference value output by the power regulation type energy direct control module, the intermediate adjustment amount generated by the outer loop control module and the inner loop control module, and the pulse width modulation duty cycle of each switching device finally output by the inter-module voltage equalization module. At the same time, the sub-operation requirements of each three-level converter corresponding to this control cycle are also associated and recorded to form a complete time sequence data record and stored in the non-volatile memory inside the system. After multiple accumulations, a historical control dataset containing the correspondence between multiple sets of control parameters and sub-operation requirements is obtained. Then, the host computer or digital signal processor retrieves the historical control dataset and uses offline optimization algorithms or multivariate regression analysis methods to compare and analyze the control parameters in the historical data with the original judgment logic of the preset conditions. It calculates the deviation and matching degree between the actual control parameters executed by each converter under different preset conditions and the sub-operational requirements. Based on this, it adjusts the judgment threshold and allocation weight in the preset conditions to better fit the actual operating conditions and scheduling requirements. Finally, it generates the optimized target preset conditions and stores them in the system parameter area for use in the next control cycle when performing energy demand allocation, thereby realizing online iterative optimization and continuous updating of preset conditions.

[0058] The above embodiments of the present invention elaborate in detail, from the process level of the control method, how to obtain target operating requirements and real-time operating data, determine sub-operating requirements, divide voltage energy requirements and power energy requirements, generate first converter parameters and second converter parameters respectively, and execute the target control scheme, as well as optimize preset conditions through historical data. The following embodiments, from the hardware topology and system architecture level, specifically define the physical basis on which the above method depends. That is, the CNPC is composed of N NPC modules with dual half-bridge cascaded protection circuits connected in AC parallel and DC series. The protection circuit has voltage regulation multiplexing function. The specific configuration of voltage regulation type energy direct control module and power regulation type energy direct control module in the energy direct control system architecture based on this hardware is given, as well as the energy management principle of system-level collaborative control. The two are complementary, the hardware provides the execution carrier for the method, and the method gives the hardware the logical rules of energy direct control, together constituting a complete energy direct control technology solution.

[0059] Another embodiment of the present invention provides an energy direct control method for cascaded three-level converters (CNPCs). Its core lies in elevating the control of the CNPC from the traditional voltage, current, and power levels to the energy level, enabling direct scheduling and control of the converter's internal energy. To achieve this goal, the present invention first imposes specific constraints on the hardware topology: the CNPC consists of N neutral point clamping modules with voltage regulation and multiplexing functions connected in parallel on the AC side and in series on the DC side. Each NPC module, in addition to using traditional three-phase diode clamping three-level bridge arms, must have a protection circuit based on a cascaded double half-bridge on its DC side. This protection circuit, by bridging two cascaded half-bridges between the positive, neutral, and negative potentials on the DC side, allows the module to actively adjust the DC bus voltage distribution and neutral point potential balance through pulse width modulation of power switching devices during normal operation, thereby possessing voltage regulation and multiplexing functions. This is also the topological prerequisite for the CNPC to achieve energy direct control.

[0060] Based on this, the present invention constructs a complete energy direct control system architecture, including a voltage-regulated energy direct control module and a power-regulated energy direct control module based on the voltage regulation and multiplexing function of the protection circuit, an outer loop control module, an inner loop control module, and an inter-module voltage equalization module. Specifically, the voltage-regulated energy direct control module calculates the energy deviation value by subtracting the measured energy from the CNPC from the command reference value of the scheduling or coordinated control. This deviation value is used by a proportional-integral or proportional-resonant controller to generate a DC voltage deviation value, which is then summed with a preset DC voltage to form a DC voltage reference value, which is sent to the subsequent outer loop control module to execute DC voltage outer loop control. The power-regulated energy direct control module uses the same energy deviation calculation method, generating an active power deviation value through the controller, summing it with a preset active power to form an active power reference value, which is then sent to the subsequent outer loop control module to execute active power outer loop control. The outer loop control module, inner loop control module, and inter-module voltage equalization module are the same as in traditional CNPC control, and ultimately, the inter-module voltage equalization module generates the trigger pulses for all switching devices in the CNPC.

[0061] This invention also provides energy management principles for system-level collaborative control. After direct energy control is enabled, the interaction port between the CNPC and the collaborative control system changes from traditional voltage, current, and power quantities to energy. The collaborative control system needs to configure the energy reference value and energy regulation mode of the CNPC. When Q CNPCs in the system require regulation, the collaborative control system must ensure that at least one CNPC operates in voltage-regulated direct energy control mode. The remaining CNPCs can select either voltage-regulated or power-regulated direct energy control modes according to actual needs. Simultaneously, the allocation of energy reference values ​​for all CNPCs must satisfy the constraint that the sum of the energy reference values ​​of all CNPCs equals the total energy required by the scheduling system. Based on this, this invention proposes an optimization principle that uses the per-unit equality of available energy for each CNPC as the energy reference value for allocation, achieving a balanced distribution of the system's total energy demand among multiple CNPCs, thereby optimizing the overall performance of the flexible power distribution system.

[0062] Another embodiment of the present invention provides an energy direct-controllability control system for a cascaded three-level converter. For details, please refer to [link to relevant documentation]. Figure 3 , Figure 3 The diagram shown is a schematic representation of the energy direct-control system of a cascaded three-level converter according to one embodiment of the present invention, including: The acquisition module 11 is used to acquire the target operating requirements of the target power system and the real-time operating data of each three-level converter in the target power system, and to determine the sub-operating requirements of each three-level converter based on the target operating requirements and the real-time operating data. The determination module 12 is used to determine the energy requirements of each three-level converter, wherein the energy requirements include voltage energy requirements and power energy requirements; The first module 13 is used to determine the first converter parameters of the three-level converter corresponding to the voltage energy demand. The first converter parameters are obtained from the DC voltage deviation of the three-level converter. The DC voltage deviation is obtained from the corresponding sub-operational demand and real-time operation data. The second module 14 is used to determine the second converter parameters of the three-level converter corresponding to the power energy demand. The second converter parameters are obtained from the active power deviation of the three-level converter. The active power deviation is obtained from the corresponding sub-operational demand and real-time operation data. The target module 15 is used to control each three-level converter to execute the target control scheme obtained from the parameters of the first converter and the parameters of the second converter.

[0063] Those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented by a computer program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, it can include the processes of the embodiments of the above methods. The storage medium can be a magnetic disk, optical disk, read-only memory (ROM), or random access memory (RAM), etc.

[0064] Accordingly, embodiments of the present invention provide a computer-readable storage medium comprising a stored computer program, wherein, when the computer program is executed, it controls the device containing the computer-readable storage medium to perform steps in the energy direct control method for a cascaded three-level converter as described in the above embodiments, for example... Figure 1 Steps S1 to S5 as described above.

[0065] This invention, through synchronous acquisition of system-level operational requirements and converter-level real-time data, generates personalized sub-operational requirements for each three-level converter, and in the process, decouples the two independent dimensions of voltage energy requirement and power energy requirement in parallel. Subsequently, the corresponding parameters of the first and second converters are derived using DC voltage deviation and active power deviation, respectively, and finally the two sets of parameters are merged to form a comprehensive target control scheme. This technical approach enables the control strategy to move beyond passively following a single electrical quantity, and instead actively perform multi-objective dynamic trade-offs based on grid dispatch instructions and real-time operating condition changes. This fundamentally eliminates the drawbacks of response lag and regulation mismatch in traditional methods, significantly improving the adaptability, flexibility, and disturbance resistance of the power system in complex operating environments.

[0066] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A direct energy control method for a cascaded three-level converter, characterized in that, include: The target operating requirements of the target power system and the real-time operating data of each three-level converter in the target power system are obtained, and the sub-operating requirements of each three-level converter are determined based on the target operating requirements and the real-time operating data. Determine the energy requirements for each of the three-level converters, wherein the energy requirements include voltage energy requirements and power energy requirements; The first converter parameter corresponding to the voltage energy demand of the three-level converter is determined. The first converter parameter is obtained by the DC voltage deviation of the three-level converter. The DC voltage deviation is obtained by the corresponding sub-operational demand and the real-time operation data. The second converter parameter corresponding to the power energy demand of the three-level converter is determined. The second converter parameter is obtained from the active power deviation of the three-level converter. The active power deviation is obtained from the corresponding sub-operational demand and the real-time operation data. Each of the three-level converters is controlled to execute the target control scheme obtained from the parameters of the first converter and the parameters of the second converter.

2. The energy direct control method for a cascaded three-level converter as described in claim 1, characterized in that, The process of acquiring the target operating requirements of the target power system and the real-time operating data of each three-level converter in the target power system, and determining the sub-operating requirements of each three-level converter based on the target operating requirements and the real-time operating data, includes: Analyze the acquired operational data of the target power system, and determine the target operational requirements based on the analysis results; Based on the real-time operating data, the real-time energy value of each of the three-level converters is determined; The real-time energy values ​​are sorted, and based on the sorting results and the target operation requirements, the sub-operation requirements are determined.

3. The energy direct control method for a cascaded three-level converter as described in claim 1, characterized in that, The determination of the energy requirement for each of the three-level converters, wherein the energy requirement includes voltage energy requirement and power energy requirement, includes: Analyze the power capacity of each of the three-level converters to obtain the target three-level converter with the maximum power capacity, and then remove the target three-level converter to obtain the first set of three-level converters; Set the energy requirement of the target three-level converter to the voltage energy requirement; The energy requirements of each of the first three-level converters in the first three-level converter cluster are determined based on preset conditions.

4. The energy direct control method for a cascaded three-level converter as described in claim 3, characterized in that, The determination of the energy demand of each of the first three-level converters in the first three-level converter cluster based on preset conditions includes: The target operating requirements and the sub-operating requirements of each of the first three-level converters are analyzed at least to determine the preset conditions.

5. The energy direct control method for a cascaded three-level converter as described in claim 1, characterized in that, The determination of the first converter parameter corresponding to the voltage energy demand of the three-level converter is made by the DC voltage deviation of the three-level converter. The DC voltage deviation is obtained from the corresponding sub-operational demand and the real-time operating data, including: The energy deviation value is obtained by analyzing the sub-operation requirements and the real-time operation data; The DC voltage deviation is obtained based on the energy deviation value; Based on the DC voltage deviation and the preset DC voltage difference, a DC voltage reference value is obtained; Based on the DC voltage reference value, the parameters of the first converter are obtained.

6. The energy direct control method for a cascaded three-level converter as described in claim 5, characterized in that, The process of obtaining the DC voltage deviation based on the energy deviation value includes: At least a proportional-integral technique is used to convert the energy deviation value into the DC voltage deviation.

7. The energy direct control method for a cascaded three-level converter as described in claim 1, characterized in that, The determination of the first converter parameters corresponding to the voltage energy demand for the three-level converter includes: The first converter parameters include at least the parameters of the dual half-bridge cascaded protection circuit and the converter circuit parameters.

8. The energy direct control method for a cascaded three-level converter as described in claim 1, characterized in that, The second converter parameter corresponding to the power energy demand of the three-level converter is determined by the active power deviation of the three-level converter. The active power deviation is obtained from the corresponding sub-operational demand and the real-time operating data, including: The energy deviation value is obtained by analyzing the sub-operation requirements and the real-time operation data; Based on the energy deviation value, the active power deviation is obtained; Based on the active power deviation and the preset active power, an active power reference value is obtained; The parameters of the second converter are obtained based on the active power reference value.

9. The energy direct control method for a cascaded three-level converter as described in claim 3, characterized in that, After controlling each of the three-level converters to execute the target control scheme obtained from the first converter parameters and the second converter parameters, the method further includes: Record the control parameters of the target control scheme and the corresponding sub-operational requirements to obtain historical control data; Based on the historical control data, the preset conditions for the next cycle are optimized to obtain the target preset conditions for the next cycle.

10. A direct-control energy control system for a cascaded three-level converter, characterized in that, include: The acquisition module is used to acquire the target operating requirements of the target power system and the real-time operating data of each three-level converter in the target power system, and to determine the sub-operating requirements of each three-level converter based on the target operating requirements and the real-time operating data. A determination module is used to determine the energy requirements of each of the three-level converters, wherein the energy requirements include voltage energy requirements and power energy requirements; The first module is used to determine the first converter parameters of the three-level converter corresponding to the voltage energy demand. The first converter parameters are obtained from the DC voltage deviation of the three-level converter. The DC voltage deviation is obtained from the corresponding sub-operational demand and the real-time operation data. The second module is used to determine the second converter parameters of the three-level converter corresponding to the power energy demand. The second converter parameters are obtained from the active power deviation of the three-level converter. The active power deviation is obtained from the corresponding sub-operational demand and the real-time operation data. The target module is used to control each of the three-level converters to execute the target control scheme obtained from the first converter parameters and the second converter parameters.

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