A method and system for coordinated control based on hybrid power electronic transformer

Abstract

This invention proposes a collaborative control method and system based on a hybrid power electronic transformer, belonging to the field of active distribution network operation and control technology. The method includes the following steps: configuring the topology of the hybrid power electronic transformer; continuous-layer global optimization to construct an equivalent model of the hybrid power electronic transformer, ignoring the physical discrete constraints of the equipment, defining continuous decision variables and decision vectors, and introducing a comprehensive objective function with a hierarchical penalty mechanism; executing an improved whale optimization algorithm to optimize the comprehensive objective function, outputting a globally optimal continuous vector as the theoretically optimal electrical operating state of the hybrid power electronic transformer; establishing a linear superposition relationship between the ideal total turns ratio target value output by continuous optimization and the compensation turns ratio provided by the mechanical tap and the power electronic converter based on the hybrid power electronic transformer topology; constructing and calculating the feasible region of the electronic capacity constraint of the power electronic converter; and combining the feasible region to execute a minimum action decision based on inertia maintenance.

Description

Technical Field

[0001] This invention relates to the field of active distribution network operation and control technology, and in particular to a collaborative control method and system based on a hybrid power electronic transformer. Background Technology

[0002] The penetration rate of distributed photovoltaic (DPV) and wind power on the distribution side continues to rise. However, the random fluctuations and uneven spatiotemporal distribution of distributed power output lead to prominent source-load timing misalignment problems, which can easily cause issues such as voltage exceeding limits at the feeder end, frequent voltage fluctuations, and backflow of power, seriously threatening the safe and stable operation of the distribution network. Existing voltage regulation technologies have significant limitations. Traditional mechanical on-load tap changers (OLTCs) rely on mechanical contact switching, which is slow and has limited daily operation, making it difficult to cope with the minute-level high-frequency fluctuations of new energy sources, and easily causing a "negative voltage regulation effect." Pure power electronic transformers (PETs), while highly controllable, have high losses and are expensive. Hybrid power electronic transformer (HPET) regulation strategies still have key shortcomings. Most schemes follow a "discrete first, then continuous" serial optimization logic, that is, first determine the mechanical tap position based on long-scale prediction, and then fine-tune the electronic part. This approach severs the physical coordination between discrete and continuous variables, easily getting trapped in a local optimum determined by the mechanical tap position, and failing to achieve optimal energy efficiency for the entire network. In addition, existing studies have focused on voltage amplitude regulation in radial power grids, neglecting the phase-shifting control potential of HPET in ring network operation mode. They have failed to fully utilize vector regulation to actively guide power from heavily loaded branches to lightly loaded branches, making it difficult to meet the multi-objective requirements of high-penetration renewable energy access.

[0003] Therefore, it is essential to provide a collaborative control method and system based on hybrid power electronic transformers to solve the problems of slow response and short lifespan of traditional mechanical voltage regulation and high losses of pure power electronic solutions. It is also necessary to achieve precise voltage and power flow control of the distribution network through deep collaboration between software and hardware. Summary of the Invention

[0004] In view of this, the present invention proposes a collaborative control method and system based on a hybrid power electronic transformer to improve the current situation of slow response and short life of traditional mechanical voltage regulation and high loss of pure power electronic schemes, and to achieve precise voltage and power flow control of distribution networks through deep hardware and software collaboration.

[0005] On the one hand, the present invention provides a cooperative control method based on a hybrid power electronic transformer, comprising the following steps: Step 0: Configure the topology of the hybrid power electronic transformer; including the main transformer body and the power electronic converter. The main transformer body is used for power transmission and generates a reference voltage vector based on different mechanical taps. The power electronic converter is connected to the neutral point side of the main transformer body winding as a controlled AC voltage source, generates a compensation voltage vector, and injects it into the main transformer body to form the total output vector of the hybrid power electronic transformer. Step 1: Continuous Layer Global Optimization; Construct an equivalent model of the hybrid power electronic transformer, ignoring the physical discrete constraints of the equipment, and define continuous decision variables and decision vectors; Based on the decision vectors, introduce a comprehensive objective function with a hierarchical penalty mechanism; Execute the improved whale optimization algorithm to optimize the comprehensive objective function and output the globally optimal continuous vector. X * This represents the theoretically optimal electrical operating state of a hybrid power electronic transformer. Step 2: Discrete-layer physical decomposition; receiving the globally optimal continuous vector. X * Then, based on the hybrid power electronic transformer topology, a linear superposition relationship is established between the target value of the ideal total turns ratio of the continuously optimized output and the compensation turns ratio provided by the mechanical tap and the power electronic converter; the feasible region of the electronic capacity constraint of the power electronic converter is constructed and calculated; combined with the feasible region, the minimum action decision based on inertia maintenance is executed to generate mechanical commands to maintain or change the mechanical tap, as well as electrical commands for the supplementary voltage vector output by the power electronic converter.

[0006] Based on the above technical solutions, preferably, the main transformer body mentioned in step 0 includes the main winding. L 0. Several tap-adjustable windings L 1. L 2、…、 L N Several mechanical switches K 11 , K 21 … K n1 In the transformer unit, one end of the main winding is connected in series to the distribution network feeder, and the other end of the main winding is selectively connected through several mechanical switches. K 11 , K 21 … K n1 The taps and several tap-adjusting windings L 1. L 2、…、 L N A one-to-one electrical connection is used to change the number of winding turns added to the circuit and determine a discrete reference ratio. kmech And generate a reference voltage vector. u Tap Several tap-adjustable windings L 1. L 2、…、 L N The number of turns in each coil is different; the main winding and its connected tap-regulating winding transmit power to the secondary side through the transformer unit.

[0007] Preferably, the power electronic converter described in step 0 includes a single-phase bridge fully controlled power unit and a series-coupled transformer. The single-phase bridge fully controlled power unit includes four semiconductor devices S1, S2, S3, and S4. The drains of the first semiconductor device S1 and the third semiconductor device S3 are electrically connected to the positive terminal of the DC bus, respectively. The sources of the second semiconductor device S2 and the fourth semiconductor device S4 are electrically connected to the negative terminal of the DC bus. The source of the first semiconductor device S1 and the drain of the second semiconductor device S2 are connected as the first output terminal of the single-phase bridge fully controlled power unit, and the source of the third semiconductor device S3 and the drain of the fourth semiconductor device S4 are connected as the second output terminal of the single-phase bridge fully controlled power unit. By driving the single-phase bridge fully controlled power unit to invert the input DC signal into an AC signal, which is then sent to the main transformer body via the series-coupled transformer. The power electronic converter generates a compensation voltage vector. u XN , and the reference voltage vector u Tap Superimposed, forming the total output vector of the hybrid power electronic transformer. u out = u Tap + u XN .

[0008] Further preferred embodiments include a current-limiting branch, a fast bypass switch, and a surge arrester protection array. The current-limiting branch conducts instantaneously when any mechanical switch is turned on, preventing arcing of the contacts during connection or disconnection. The fast bypass switch is located between the positive and negative terminals of the DC bus and conducts when an anomaly occurs in the distribution network, preventing damage to the power electronic converter. The surge arrester protection array is located between the power electronic converter port and the windings of the series-coupled transformer to clamp voltage surges.

[0009] Further preferably, the equivalent model of the hybrid power electronic transformer described in step 1, which ignores the physical discrete constraints of the equipment and defines continuous decision variables and decision vectors, treats the hybrid power electronic transformer as an ideal voltage source with continuously adjustable turns ratio and phase shift angle, and selects the total equivalent turns ratio of all hybrid power electronic transformer nodes. ktotal and equivalent phase shift angle α As a continuous decision variable, assume that the distribution network is deployed with n Taiwan hybrid power electronic transformer, definition t System decision vector at time step X 2 N A 1-dimensional real vector: , make node i =1, 2, ..., n ,but k total,i Indicates the first i The total equivalent turns ratio of the hybrid power electronic transformer. α i Indicates the first i Phase shift angle of a hybrid power electronic transformer.

[0010] Furthermore, preferably, the comprehensive objective function based on the decision vector and incorporating a hierarchical penalty mechanism described in step 1 is defined as follows: F ( X The objective function is obtained by summing the active power loss and penalty term of the entire network. The comprehensive objective function is the objective function. F ( X minimum value minF ( X ), , As a maximum penalty factor, N bus The total number of nodes. U max , U min These are the lower and upper limits of the node voltage, respectively. U n For the first n Voltage at each node, active power loss across the entire network. , N br The total number of branch roads, G m For branch circuit conductance, U i and U j The voltage amplitude at the nodes at both ends of the branch is... The phase angle difference between the nodes at both ends of the branch is denoted as .

[0011] In a further preferred embodiment, the improved whale optimization algorithm described in step 1 is used to optimize the comprehensive objective function and output the globally optimal continuous vector. X * The theoretically optimal electrical operating state of a hybrid power electronic transformer includes the following steps: S11: Population initialization, setting the population size N p and maximum number of iterations T max Within the continuous domain defined by continuous decision variables, the initial population is randomly generated using real-number encoding. ; S12: Fitness assessment, for each individual in the population. X k Perform power flow calculations on the distribution network to obtain the voltage distribution and power loss of all nodes in the network. Substitute these values ​​into the objective function to calculate the fitness value and update the current global optimum. X * ; S13: Execute the position update strategy, generating random numbers in each iteration. p and convergence factor A The update mechanism is adaptively selected based on the following logic: Mechanism 1, when... and At that time, the simulated whale shrinks its encirclement around its prey, and the individual moves towards the current global optimal solution. Approaching, update strategy ,in B and C For the algorithm coefficient vector, T This represents the current iteration number. X ( T ) is the first T Individuals in the next iteration; Mechanism 2, when At that time, the simulated whale swims upwards along a spiral path, digging deep within the solution space, and the updated strategy is... , This represents the distance between the individual and the global optimal solution. b The constant is the helical constant. l A random number in the interval [-1, 1]; Mechanism 3, when In this scenario, simulating a whale randomly wandering in search of prey, an individual does not move towards the optimal solution but instead randomly selects a reference individual. X rand Update ; S14: Repeat steps S12 and S13 until the maximum number of iterations is reached or the convergence accuracy is met, and output the final globally optimal continuous vector.

[0012] Preferably, step 2 establishes a linear superposition relationship between the target value of the ideal total turns ratio for continuous optimization output and the compensation turns ratio provided by the mechanical gear and the power electronic converter; constructs and calculates the feasible region of the electronic capacity constraint of the power electronic converter, which allows for any given time... t The target value of the total equivalent turns ratio of the hybrid power electronic transformer corresponding to the globally optimal continuous vector. It is the discrete voltage transformation ratio provided by the mechanical switch. k mech ( TAP t Compensation ratio provided by power electronic converter k elec ( t The superposition of ) , TAP t It is any time t The index of the mechanical gear position; let the electronic capacity constraint of the power electronic converter be: the compensation ratio provided by the power electronic converter. k elec ( t The absolute value of () must not exceed the maximum compensation capacity of the power electronic converter. , Based on the target value of the total equivalent turns ratio of the hybrid power electronic transformer By working backwards, we can determine all mechanical gears that satisfy the capacity constraint, thus forming the feasible region at the current moment. .

[0013] More preferably, in step 2, combining the feasible region to perform the minimum motion decision based on inertia retention means obtaining the mechanical gear state at the previous moment. Determine whether it belongs to the feasible region at the current time. ,if This indicates that the mechanical gear position from the previous moment, combined with the current electronic compensation capability, is sufficient to meet the new adjustment requirements; therefore, the mechanical gear position should remain unchanged. At this point, the adjustment deviation is completely absorbed by the power electronic module, and the compensation ratio provided by the power electronic converter is... , The discrete voltage turns ratio provided for the mechanical switch to be turned on at the previous moment; if This indicates that the change in the ideal turns ratio exceeds the limit of the compensation turns ratio provided by the power electronic converter under the current mechanical gear position, and a mechanical switch must be performed to select the gear closest to the mechanical gear position at the previous moment as the new target gear. , and For the current moment t and the previous moment t -1st i The mechanical tap position selected for the hybrid power electronic transformer. i This is the index number for hybrid power electronic transformers.

[0014] On the other hand, the present invention provides a collaborative control system based on a hybrid power electronic transformer for the above-mentioned method, comprising: The hybrid power electronic transformer configuration module consists of a main transformer body, a power electronic converter, and peripheral devices, forming several hybrid power electronic transformers. The main transformer body of each hybrid power electronic transformer is equipped with several mechanical taps to generate different reference voltage vectors. The power electronic converter, as a controlled AC voltage source, generates a compensation voltage vector and injects it into the main transformer body to form the total output vector of the hybrid power electronic transformer. The continuous global optimization module, based on the circuit of the hybrid power electronic transformer configuration module, constructs an equivalent model of the hybrid power electronic transformer, ignores the physical discrete constraints of the equipment, constructs a comprehensive objective function, optimizes the comprehensive objective function, and outputs the optimal result as the theoretical optimal electrical operating state of the hybrid power electronic transformer; The discrete physics decision module, based on the optimal results output by the continuous global optimization module and the hybrid power electronic transformer topology, establishes a linear superposition relationship between the target value of the ideal total turns ratio output by continuous optimization and the compensation turns ratio provided by the mechanical gear and the power electronic converter. Within the feasible region of the electronic capacity constraint of the power electronic converter, it executes the minimum action decision based on inertia maintenance and outputs the mechanical command of the mechanical gear and the electrical command output by the power electronic converter.

[0015] The present invention provides a collaborative control method and system based on a hybrid power electronic transformer, which has the following advantages compared with the prior art: 1. At the hardware physical layer, this invention constructs a hybrid topology consisting of a "stepped regulation module" composed of a mechanical decomposition head and a "stepless regulation module" composed of a series power electronic converter. Utilizing the principle of voltage vector superposition, a compensation voltage with continuously controllable amplitude and phase is injected through the power electronic converter to achieve stepless regulation of the output voltage and active guidance of the ring network power flow.

[0016] 2. At the system control layer, this invention constructs a "continuous-discrete collaborative optimization" control architecture. This architecture breaks away from the traditional "discrete first, then continuous" serial logic, adopting a reverse decoupling strategy of "first global continuous optimization, then physical implementation decomposition." The system first treats the hybrid transformer as an ideal regulating element in the continuous domain, searching for the globally optimal solution that satisfies voltage safety and minimizes network loss. Subsequently, based on the "minimum action principle," this continuous ideal solution is dynamically decomposed into mechanical tap positions and electronic compensation commands. This method effectively smooths high-frequency fluctuations in new energy sources and eliminates voltage overruns, while fully utilizing the wide-range regulation capability of the electronic module to absorb fluctuations and minimizing the operating frequency of the mechanical tap changer, thereby achieving a balance between long equipment lifespan and high system energy efficiency.

[0017] 3. In order to solve the problem of shortened lifespan caused by frequent operation of traditional mechanical switches, this invention introduces an "inertia holding" strategy. Under the premise of meeting electrical constraints, the system is forced to maintain the original mechanical state, or the mechanical action is triggered only when necessary, and the action amplitude is minimal. This reduces the number of daily actions of the mechanical tap changer from dozens of times in the traditional strategy to a single time. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, 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 the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is an overall block diagram of a collaborative control method and system based on a hybrid power electronic transformer according to the present invention. Figure 2 This is a hybrid power electronic transformer topology diagram of a collaborative control method and system based on a hybrid power electronic transformer according to the present invention. Figure 3 This is a continuous layer flowchart of a collaborative control method and system based on a hybrid power electronic transformer according to the present invention; Figure 4 This is a discrete-layer flowchart of a collaborative control method and system based on a hybrid power electronic transformer according to the present invention. Detailed Implementation

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. 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.

[0021] Traditional voltage regulation techniques for distribution networks focus primarily on controlling voltage amplitude. However, in ring network operation mode, simply adjusting voltage amplitude is insufficient to effectively control circulating power. Existing research on hybrid transformers often overlooks their phase-shift control potential, leading to overload in critical branches and significant circulating current losses, thus limiting the ring network's ability to absorb distributed power sources.

[0022] In view of this, such as Figure 1 As shown, on one hand, the present invention provides a cooperative control method based on a hybrid power electronic transformer, comprising the following steps: Step 0: Configure the topology of the hybrid power electronic transformer; including the main transformer body and the power electronic converter. The main transformer body is used for power transmission and generates a reference voltage vector based on different mechanical taps. The power electronic converter is connected to the neutral point side of the main transformer body winding as a controlled AC voltage source, generates a compensation voltage vector, and injects it into the main transformer body to form the total output vector of the hybrid power electronic transformer.

[0023] This invention proposes a hybrid power electronic transformer (HPET) suitable for distribution networks with a high proportion of renewable energy. The device employs a series hybrid architecture of "stepped mechanical coarse adjustment + stepless electronic fine adjustment" in its circuit topology, aiming to achieve wide-range, high-precision voltage and power flow control through low-cost hardware combinations. The HPET is connected in series to the distribution network feeder, for example, on the 10kV or 0.4kV side.

[0024] like Figure 2 As shown, the hybrid power electronic transformer mainly consists of three parts: the main transformer body, the power electronic converter, and the auxiliary protection circuit module. Specifically, 1) the main transformer body includes the main winding L0 and several tap-changing windings. L 1. L 2、…、 L N Several mechanical switches K 11 , K 21 … K n1 In the transformer unit, one end of the main winding is connected in series to the distribution network feeder, and the other end of the main winding is selectively connected through several mechanical switches. K 11 , K 21 … K n1 The taps and several tap-adjusting windings L 1. L 2、…、 L N By making one-to-one electrical connections and changing the number of turns in the windings added to the circuit, a discrete reference turns ratio can be determined. k mech And generate a reference voltage vector. u Tap Several tap-adjustable windings L 1. L 2、…、 L N The number of turns in each coil is different; the main winding and its connected tap-regulating winding transmit power to the secondary side through the transformer unit.

[0025] The stepped regulation module in the mechanical section is an improvement on the traditional on-load tap-changing transformer structure. It is responsible for wide-range discrete voltage regulation and serves as the main power transmission channel. The windings, including the main winding and the tap-changing winding, are combined to form different turns ratios. The mechanical switches, controlled by a logic control unit, manage specific winding and switch combinations, changing the effective number of turns in the circuit to determine the discrete reference turns ratio. k mech Each tap-regulating winding provides a discrete voltage reference, with a single-range adjustment step typically designed to be 1.25% or 2.5% of the rated voltage. The diagram shows the voltage transformer and current transformer in the TV and TA configurations.

[0026] 2) A power electronic converter, comprising a single-phase bridge fully controlled power unit and a series-coupled transformer. The single-phase bridge fully controlled power unit includes four semiconductor devices S1, S2, S3, and S4. The drains of the first semiconductor device S1 and the third semiconductor device S3 are electrically connected to the positive terminal of the DC bus. The sources of the second semiconductor device S2 and the fourth semiconductor device S4 are electrically connected to the negative terminal of the DC bus. The source of the first semiconductor device S1 and the drain of the second semiconductor device S2 are connected as the first output terminal of the single-phase bridge fully controlled power unit. The source of the third semiconductor device S3 and the drain of the fourth semiconductor device S4 are connected as the second output terminal of the single-phase bridge fully controlled power unit. By driving the single-phase bridge fully controlled power unit, the input DC signal is inverted to an AC signal, which is then sent to the main transformer body via the series-coupled transformer. Figure 2 It can be seen that the DC side of the power electronic converter is equipped with a large-capacity DC capacitor C. DC This is used to stabilize the DC bus voltage and provide energy buffering for voltage injection on the AC side. A passive filter circuit, such as inductor L0 and capacitor C0, is configured at the converter output to filter out high-frequency switching harmonics generated by the PWM modulation of the power electronic converter. The filtered pure voltage is injected into the neutral point side of the main circuit through a series-coupled transformer. In this embodiment, the four semiconductor devices can be IGBTs.

[0027] The power electronic converter is configured to output a voltage vector of arbitrary phase. Driven by an external controller, it can output a longitudinal component U that is in phase with the reference voltage vector. d It is used to fill the dead zone between mechanical gears and can also provide a lateral component U orthogonal to the reference voltage vector. q It is used to adjust the phase angle, thereby giving the hybrid power electronic transformer phase-shift control capability.

[0028] The main transformer body undertakes the main power transmission and voltage transformation tasks, while the power electronic converter generates the compensation voltage vector. uXN , and the reference voltage vector u Tap Superimposed, forming the total output vector of the hybrid power electronic transformer. u out = u Tap + u XN By controlling the amplitude and phase of the compensation voltage vector, continuous adjustment of the total output vector can be achieved.

[0029] 3) The auxiliary protection circuit module mainly includes a current-limiting branch, a fast bypass switch, and a surge arrester protection array. The current-limiting branch includes a current-limiting resistor R1 and an auxiliary power switch DL1, which conducts instantaneously when any mechanical switch is turned on to prevent arcing when the contacts are turned on or off. The fast bypass switch includes... Figure 2 Semiconductor devices marked S5 and S6, such as thyristors (SCRs), are installed between the positive and negative terminals of the DC bus. They quickly bypass the circuit when an anomaly occurs in the power distribution network to prevent damage to the power electronic converter. The surge arrester protection array is installed between the power electronic converter port and the windings of the series-coupled transformer to clamp voltage surges.

[0030] Step 1: Continuous Layer Global Optimization; Construct an equivalent model of the hybrid power electronic transformer, ignoring the physical discrete constraints of the equipment, and define continuous decision variables and decision vectors; Based on the decision vectors, introduce a comprehensive objective function with a hierarchical penalty mechanism; Execute the improved whale optimization algorithm to optimize the comprehensive objective function and output the globally optimal continuous vector. X * This represents the theoretically optimal electrical operating state of a hybrid power electronic transformer.

[0031] This invention proposes a two-layer collaborative control architecture of "first global continuous optimization, then physical decomposition," breaking the traditional serial logic of "discrete first, then continuous," aiming to solve the problem of strong coupling between discrete mechanical tap positions and continuous electronic compensation quantities. The virtual layer, or continuous layer, temporarily ignores the discreteness and dead zone of the mechanical switches, equating the HPET (High-Performance Electronic Switch) to an "ideal power router" with continuously adjustable turns ratio and phase angle, searching for the theoretically electrical optimal operating point within the total solution space. The physical layer, or discrete layer, receives the ideal commands from the virtual layer and, based on equipment physical constraints and the "minimum action principle," decomposes them into specific mechanical tap positions and power electronic converter compensation commands.

[0032] The specific process is as follows: Figure 3As shown, in the continuous-discrete collaborative optimization control architecture, the first layer is a continuous-layer global optimization based on a virtual ideal model. This step aims to temporarily ignore the discrete action constraints of the mechanical switches of the hybrid power electronic transformer (HPET) and search for the theoretically optimal control command in the continuous solution space of the entire system that can simultaneously satisfy the grid voltage security constraints and minimize the active power loss of the system.

[0033] The definition of continuous decision variables and decision vectors involves treating the hybrid power electronic transformer as an ideal voltage source with continuously adjustable turns ratio and phase shift angle, and selecting the total equivalent turns ratio of all nodes in the hybrid power electronic transformer. k total and equivalent phase shift angle α As a continuous decision variable, assume that the distribution network is deployed with n Taiwan hybrid power electronic transformer, definition t System decision vector at time step X 2 N A 1-dimensional real vector: , make node i =1, 2, ..., n ,but k total,i Indicates the first i The total equivalent turns ratio of the hybrid power electronic transformer, in this embodiment, ranges from [0.8, 1.2]. α i Indicates the first i The phase shift angle of the hybrid power electronic transformer in this embodiment is taken in the range of [-15°, 15°].

[0034] Based on decision vectors, the comprehensive objective function incorporating a hierarchical penalty mechanism is defined as follows: F ( X The independent variable of the objective function is the system decision vector. X， The objective function is obtained by summing the active power loss and penalty term of the entire network. The comprehensive objective function is the objective function. F ( X minimum value minF ( X ), , As a maximum penalty factor, N bus The total number of nodes. U max , U min These are the lower and upper limits of the node voltage, respectively, which are taken as 1.07 pu and 0.93 pu in this embodiment; U n For the first nVoltage at each node, active power loss across the entire network. , N br The total number of branch roads, G m For branch circuit conductance, U i and U j The voltage amplitude at the nodes at both ends of the branch is... This represents the phase angle difference between the nodes at both ends of the branch. In this embodiment, the maximum penalty factor is 10. 6 This penalizes voltage exceeding limits. It should be noted that when the voltage at any node exceeds the limit... U n When the safe range is exceeded, the penalty term is non-zero and has a huge value, making the objective function... F ( X The sudden increase in voltage limits forces the optimization algorithm to abandon the solution, thus ensuring that the search results prioritize the voltage safety constraints.

[0035] The improved whale optimization algorithm described in step 1 is used to optimize the comprehensive objective function and output the globally optimal continuous vector. X * The theoretically optimal electrical operating state of a hybrid power electronic transformer includes the following steps: S11: Population initialization, setting the population size N p and maximum number of iterations T max Within the continuous domain defined by continuous decision variables, the initial population is randomly generated using real-number encoding. ; S12: Fitness assessment, for each individual in the population. X k Perform power flow calculations on the distribution network to obtain the voltage distribution and power loss of all nodes in the network, and substitute them into the objective function. F ( X In this process, the fitness value is calculated, and the current global optimum is updated. X * The power flow calculation of the distribution network here can be performed using methods such as forward backward substitution or the Newton-Raphson method.

[0036] S13: Execute the position update strategy, generating random numbers in each iteration. p and convergence factor A The update mechanism is adaptively selected based on the following logic: Mechanism 1, when... and At that time, the simulated whale shrinks its encirclement around its prey, and the individual moves towards the current global optimal solution. Approaching, update strategy ,in B and C For the algorithm coefficient vector, T This represents the current iteration number. X ( T ) is the first T Individuals in the next iteration; Mechanism 2, when At that time, the simulated whale swims upwards along a spiral path, digging deep within the solution space, and the updated strategy is... , This represents the distance between the individual and the global optimal solution. b The constant is the helical constant. l A random number in the interval [-1, 1]; Mechanism 3, when In this scenario, simulating a whale randomly wandering in search of prey, an individual does not move towards the optimal solution but instead randomly selects a reference individual. X rand Update This mechanism effectively prevents the algorithm from getting stuck in local voltage extreme points, thus enhancing its global optimization capability.

[0037] S14: Repeat steps S12 and S13 until the maximum number of iterations is reached or the convergence accuracy is met, and output the final globally optimal continuous vector.

[0038] This output represents the theoretically optimal electrical operating state that the system can achieve at the current moment, ignoring the physical discrete constraints of the equipment, and will be passed as a benchmark target to the next stage of discrete layer for physical decomposition.

[0039] Step 2: Discrete-layer physical decomposition; receiving the globally optimal continuous vector. X * Then, based on the hybrid power electronic transformer topology, a linear superposition relationship is established between the target value of the ideal total turns ratio of the continuously optimized output and the compensation turns ratio provided by the mechanical tap and the power electronic converter; the feasible region of the electronic capacity constraint of the power electronic converter is constructed and calculated; combined with the feasible region, the minimum action decision based on inertia maintenance is executed to generate mechanical commands to maintain or change the mechanical tap, as well as electrical commands for the supplementary voltage vector output by the power electronic converter.

[0040] In the continuous-discrete collaborative optimization control architecture, the second layer is a discrete-layer physical decomposition. This step receives the ideal continuous control command output from the first layer. Based on the physical constraints of the hybrid power electronic transformer (HPET), the "minimum action principle" is used to dynamically decompose it into discrete tap position commands from the mechanical tap changer and continuous compensation commands from the power electronic converter. The specific process is as follows: Figure 4 As shown.

[0041] This involves establishing a linear superposition relationship between the ideal total turns ratio target value for continuous optimization output and the compensation turns ratio provided by the mechanical gear position and the power electronic converter; constructing and calculating the feasible region of the electronic capacity constraint of the power electronic converter, which is such that at any given time... t The target value of the total equivalent turns ratio of the hybrid power electronic transformer corresponding to the globally optimal continuous vector. It is the discrete voltage transformation ratio provided by the mechanical switch. k mech ( TAP t Compensation ratio provided by power electronic converter k elec ( t The superposition of ) , TAP t It is any time t The index of the mechanical gear positions.

[0042] Since the capacity and DC bus voltage of a power electronic converter are finite, there is a maximum physical limit to the voltage compensation it can provide. Let the electronic capacity constraint of the power electronic converter be: the compensation ratio provided by the power electronic converter. k elec ( t The absolute value of () must not exceed the maximum compensation capacity of the power electronic converter. , Based on the target value of the total equivalent turns ratio of the hybrid power electronic transformer By working backwards, we can determine all mechanical gears that satisfy the capacity constraint, thus forming the feasible region at the current moment. Maximum compensation capability in this embodiment The value is set to 0.1 pu. This feasible region contains all mechanical gear candidate values ​​that can achieve the ideal gear ratio through electronic compensation at the current moment.

[0043] Step 2, which involves combining the feasible region to perform a minimum motion decision based on inertia maintenance, refers to obtaining the mechanical gear state from the previous moment. Determine whether it belongs to the feasible region at the current time. ,if This indicates that the mechanical gear position from the previous moment, combined with the current electronic compensation capability, is sufficient to meet the new adjustment requirements; therefore, the mechanical gear position should remain unchanged. At this point, the adjustment deviation is completely absorbed by the power electronic module, and the compensation ratio provided by the power electronic converter is... , The discrete voltage turns ratio provided for the mechanical switch to be turned on at the previous moment; if This indicates that the change in the ideal turns ratio exceeds the limit of the compensation turns ratio provided by the power electronic converter under the current mechanical gear position, and a mechanical switch must be performed to select the gear closest to the mechanical gear position at the previous moment as the new target gear. , and For the current moment t and the previous moment t -1st i The mechanical tap position selected for the hybrid power electronic transformer. i This is the index number for hybrid power electronic transformers.

[0044] This invention introduces an "inertia hold" strategy, which forces the system to maintain its original mechanical state while satisfying electrical constraints. This strategy ensures that mechanical actions are triggered only when necessary, and with minimal amplitude, thereby reducing the number of daily actions of the mechanical tap changer from dozens in traditional strategies to a single action.

[0045] Based on the decomposition results determined in step 2, the final bottom-level drive signals are generated: Mechanical command: Send a switching command to the on-load tap changer drive mechanism. TAP t Or maintain instructions; electronic instructions: based on calculated k elec ( t Determine the longitudinal component U of the injected voltage. d Phase angle instruction: Directly receives the ideal phase shift angle from the first layer of continuous optimization output. α* Determine the transverse component U of the injected voltage. q Using space vector pulse width modulation (SVPWM) or sinusoidal pulse width modulation (SPWM) techniques, the power electronic converter is driven to output a composite voltage vector. , here j 0 is the imaginary unit.

[0046] On the other hand, the present invention provides a collaborative control system based on a hybrid power electronic transformer for the above-mentioned method, comprising: The hybrid power electronic transformer configuration module consists of a main transformer body, a power electronic converter, and peripheral devices, forming several hybrid power electronic transformers. The main transformer body of each hybrid power electronic transformer is equipped with several mechanical taps to generate different reference voltage vectors. The power electronic converter, as a controlled AC voltage source, generates a compensation voltage vector and injects it into the main transformer body to form the total output vector of the hybrid power electronic transformer. The continuous global optimization module, based on the circuit of the hybrid power electronic transformer configuration module, constructs an equivalent model of the hybrid power electronic transformer, ignores the physical discrete constraints of the equipment, constructs a comprehensive objective function, optimizes the comprehensive objective function, and outputs the optimal result as the theoretical optimal electrical operating state of the hybrid power electronic transformer; The discrete physics decision module, based on the optimal results output by the continuous global optimization module and the hybrid power electronic transformer topology, establishes a linear superposition relationship between the target value of the ideal total turns ratio output by continuous optimization and the compensation turns ratio provided by the mechanical gear and the power electronic converter. Within the feasible region of the electronic capacity constraint of the power electronic converter, it executes the minimum action decision based on inertia maintenance and outputs the mechanical command of the mechanical gear and the electrical command output by the power electronic converter.

[0047] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A collaborative control method based on a hybrid power electronic transformer, characterized in that, Includes the following steps: Step 0: Configure the topology of the hybrid power electronic transformer; including the main transformer body and the power electronic converter. The main transformer body is used for power transmission and generates a reference voltage vector based on different mechanical taps. The power electronic converter is connected to the neutral point side of the main transformer body winding as a controlled AC voltage source, generates a compensation voltage vector, and injects it into the main transformer body to form the total output vector of the hybrid power electronic transformer. Step 1: Continuous layer global optimization; construct an equivalent model of the hybrid power electronic transformer, ignore the physical discrete constraints of the equipment, and define continuous decision variables and decision vectors; Based on the decision vector, a comprehensive objective function with a hierarchical penalty mechanism is introduced; an improved whale optimization algorithm is executed to optimize the comprehensive objective function and output the globally optimal continuous vector. X * This represents the theoretically optimal electrical operating state of a hybrid power electronic transformer. Step 2: Physical decomposition of discrete layers; Receive the globally optimal continuous vector X * Then, based on the hybrid power electronic transformer topology, a linear superposition relationship is established between the target value of the ideal total turns ratio of the continuously optimized output and the compensation turns ratio provided by the mechanical tap and the power electronic converter; the feasible region of the electronic capacity constraint of the power electronic converter is constructed and calculated; combined with the feasible region, the minimum action decision based on inertia maintenance is executed to generate mechanical commands to maintain or change the mechanical tap, as well as electrical commands for the supplementary voltage vector output by the power electronic converter.

2. The collaborative control method based on a hybrid power electronic transformer according to claim 1, characterized in that, The main transformer body mentioned in step 0 includes the main winding. L 0. Several tap-adjustable windings L 1. L 2、…、 L N Several mechanical switches K 11 , K 21 … K n1 In the transformer unit, one end of the main winding is connected in series to the distribution network feeder, and the other end of the main winding is selectively connected through several mechanical switches. K 11 , K 21 … K n1 The taps and several tap-adjusting windings L 1. L 2、…、 L N A one-to-one electrical connection is used to change the number of winding turns added to the circuit and determine a discrete reference ratio. k mech And generate a reference voltage vector. u Tap Several tap-adjustable windings L 1. L 2、…、 L N The number of turns in each coil is different; the main winding and its connected tap-regulating winding transmit power to the secondary side through the transformer unit.

3. The collaborative control method based on a hybrid power electronic transformer according to claim 2, characterized in that, The power electronic converter described in step 0 includes a single-phase bridge fully controlled power unit and a series-coupled transformer. The single-phase bridge fully controlled power unit includes four semiconductor devices S1, S2, S3, and S4. The drains of the first semiconductor device S1 and the third semiconductor device S3 are electrically connected to the positive terminal of the DC bus. The sources of the second semiconductor device S2 and the fourth semiconductor device S4 are electrically connected to the negative terminal of the DC bus. The source of the first semiconductor device S1 and the drain of the second semiconductor device S2 are connected as the first output terminal of the single-phase bridge fully controlled power unit. The source of the third semiconductor device S3 and the drain of the fourth semiconductor device S4 are connected as the second output terminal of the single-phase bridge fully controlled power unit. By driving the single-phase bridge fully controlled power unit, the input DC signal is inverted to an AC signal, which is then sent to the main transformer via the series-coupled transformer. The power electronic converter generates a compensation voltage vector. u XN , and the reference voltage vector u Tap Superimposed, forming the total output vector of the hybrid power electronic transformer. u out = u Tap + u XN .

4. The collaborative control method based on a hybrid power electronic transformer according to claim 3, characterized in that, It also includes a current-limiting branch, a fast bypass switch, and a surge arrester protection array. The current-limiting branch conducts the moment any mechanical switch is turned on, preventing arcing when the contacts are turned on or off. The fast bypass switch is located between the positive and negative terminals of the DC bus. When an anomaly occurs in the distribution network, the fast bypass switch conducts to prevent damage to the power electronic converter. The surge arrester protection array is located between the power electronic converter port and the windings of the series-coupled transformer to clamp voltage surges.

5. The collaborative control method based on a hybrid power electronic transformer according to claim 3, characterized in that, The equivalent model of the hybrid power electronic transformer described in step 1, which ignores the physical discrete constraints of the equipment and defines continuous decision variables and decision vectors, is to equate the hybrid power electronic transformer to an ideal voltage source with continuously adjustable turns ratio and phase shift angle. The total equivalent turns ratio of all nodes of the hybrid power electronic transformer is selected. k total and equivalent phase shift angle α As a continuous decision variable, assume that the distribution network is deployed with n Taiwan hybrid power electronic transformer, definition t System decision vector at time step X 2 N A 1-dimensional real vector: , make node i =1, 2, ..., n ,but k total,i Indicates the first i The total equivalent turns ratio of the hybrid power electronic transformer. α i Indicates the first i Phase shift angle of a hybrid power electronic transformer.

6. The collaborative control method based on a hybrid power electronic transformer according to claim 5, characterized in that, The comprehensive objective function based on decision vectors and incorporating a hierarchical penalty mechanism, as described in step 1, is defined as follows: F ( X ), objective function F ( X The objective function is obtained by summing the active power loss and penalty term of the entire network. F ( X minimum value minF ( X ).

7. The collaborative control method based on a hybrid power electronic transformer according to claim 6, characterized in that, The improved whale optimization algorithm described in step 1 is used to optimize the comprehensive objective function and output the globally optimal continuous vector. X * The theoretically optimal electrical operating state of a hybrid power electronic transformer includes the following steps: S11: Population initialization, setting the population size N p and maximum number of iterations T max Within the continuous domain defined by continuous decision variables, the initial population is randomly generated using real-number encoding. ; S12: Fitness assessment, for each individual in the population. X k Perform power flow calculations on the distribution network to obtain the voltage distribution and power loss of all nodes in the network. Substitute these values ​​into the objective function to calculate the fitness value and update the current global optimum. X * ; S13: Execute the position update strategy, generating random numbers in each iteration. p and convergence factor A The update mechanism is adaptively selected based on the following logic: Mechanism 1, when... and At that time, the simulated whale shrinks its encirclement around its prey, and the individual moves towards the current global optimal solution. Approaching, update strategy ,in B and C For the algorithm coefficient vector, T This represents the current iteration number. X ( T ) is the first T Individuals in the next iteration; Mechanism 2, when At that time, the simulated whale swims upwards along a spiral path, digging deep within the solution space, and the updated strategy is... , This represents the distance between the individual and the global optimal solution. b The constant is the helical constant. l A random number in the interval [-1, 1]; Mechanism 3, when In this scenario, simulating a whale randomly wandering in search of prey, an individual does not move towards the optimal solution but instead randomly selects a reference individual. X rand Update ; S14: Repeat steps S12 and S13 until the maximum number of iterations is reached or the convergence accuracy is met, and output the final globally optimal continuous vector.

8. The collaborative control method based on a hybrid power electronic transformer according to claim 2, characterized in that, Step 2 describes establishing a linear superposition relationship between the target value of the ideal total turns ratio for continuous optimization output and the compensation turns ratio provided by the mechanical gear and the power electronic converter; constructing and calculating the feasible region of the electronic capacity constraint of the power electronic converter is such that at any given time... t The target value of the total equivalent turns ratio of the hybrid power electronic transformer corresponding to the globally optimal continuous vector. It is the discrete voltage transformation ratio provided by the mechanical switch. k mech ( TAP t Compensation ratio provided by power electronic converter k elec ( t The superposition of ) TAP t It is any time t The index of the mechanical gears; given the electronic capacity constraint of the power electronic converter, reverse-engineer all mechanical gears that satisfy the capacity constraint to form the feasible region at the current moment. .

9. The collaborative control method based on a hybrid power electronic transformer according to claim 8, characterized in that, Step 2, which involves combining the feasible region to perform a minimum motion decision based on inertia maintenance, refers to obtaining the mechanical gear state from the previous moment. Determine whether it belongs to the feasible region at the current time. ,if This indicates that the mechanical gear position from the previous moment, combined with the current electronic compensation capability, is sufficient to meet the new adjustment requirements; therefore, the mechanical gear position should remain unchanged. At this point, the adjustment deviation is completely absorbed by the power electronic module, and the power electronic converter provides the compensation ratio. k elec ( t ); if This indicates that the change in the ideal gear ratio exceeds the limit of the compensation gear ratio provided by the power electronic converter under the current mechanical gear position, and a mechanical switch must be performed to select the gear position closest to the previous mechanical gear position as the new target gear position.

10. A collaborative control system based on a hybrid power electronic transformer, used to implement the method described in any one of claims 1-9, characterized in that, include: The hybrid power electronic transformer configuration module consists of a main transformer body, a power electronic converter, and peripheral devices, forming several hybrid power electronic transformers. The main transformer body of each hybrid power electronic transformer is equipped with several mechanical taps to generate different reference voltage vectors. The power electronic converter, as a controlled AC voltage source, generates a compensation voltage vector and injects it into the main transformer body to form the total output vector of the hybrid power electronic transformer. The continuous global optimization module, based on the circuit of the hybrid power electronic transformer configuration module, constructs an equivalent model of the hybrid power electronic transformer, ignores the physical discrete constraints of the equipment, constructs a comprehensive objective function, optimizes the comprehensive objective function, and outputs the optimal result as the theoretical optimal electrical operating state of the hybrid power electronic transformer; The discrete physics decision module, based on the optimal results output by the continuous global optimization module and the hybrid power electronic transformer topology, establishes a linear superposition relationship between the target value of the ideal total turns ratio output by continuous optimization and the compensation turns ratio provided by the mechanical gear and the power electronic converter. Within the feasible region of the electronic capacity constraint of the power electronic converter, it executes the minimum action decision based on inertia maintenance and outputs the mechanical command of the mechanical gear and the electrical command output by the power electronic converter.

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